Type ichnospecies.—Archaeonassa fossulata Fenton & Fenton, 1937a.

Emended Diagnosis.—Short, round- to ovoid-shaped or elongated trails or burrows commonly deeper at one end, and may grade into indistinct V-shaped trails; concave to slightly convex furrow flanked by pair of convex ridges, central furrow typically wider than ridges; lateral convex ridges may be smooth or ornamented with oblique to transverse striations or smaller lobes (Fenton & Fenton, 1937a; Buckman, 1994).

Discussion.—Fenton and Fenton (1937a) established Archaeonassa for elongate, concave furrows with flanking convex ridges produced by snails and other gastropods from the lower Cambrian Mount Whyte Formation of British Columbia. Häntzschel (1975) placed Archaeonassa in the Scolicia Group, but was not placed in synonymy with Scolicia because Archaeonassa lacks any complex backfill diagnostic to Scolicia (Buckman, 1994). Buckman (1994) reviewed Archaeonassa and considered it the senior synonym of Scolicia vada Chamberlain, 1971, and some specimens of Palaeobullia Götzinger & Becker, 1932. Yochelson and Fedonkin (1997) rejected this synonymy, however, partly because Buckman (1994) did not include the original type material of Archaeonassa while also including ornamented lateral ridges.

Archaeonassa is generally interpreted as a gastropod locomotion or grazing trace ((Fenton & Fenton, 1937a; Buckman, 1994; Jensen, Droser, & Gehling, 2005). Yochelson and Fedonkin (1997), however, suggested that Archaeonassa was not produced by mollusks but did not suggest any other producers. Trilobites and echinoids have also been suggested as possible tracemakers (Buckman, 1994). Jensen, Droser, and Gehling (2005) pointed out that such protists as foraminifera can make traces similar to Archaeonassa but are rarely considered as producers. Buchanan and Hedley (1960, p. 557–558) did not figure any ichnofossils (i.e., only provided drawings of the pseudopodial systems used by forams), but provided a description of foram-produced furrows: “… a furrow is left in the sand as a result of the leading edge of the test being preceded by a raised mound or ‘bow-wave’ of sand.” This description, however, does match most Archaeonassa descriptions. Archaeonassa has mostly been reported from shallow-marine deposits (e.g., tidal flats), as well as from continental deposits (e.g., delta front, fluvial, and lacustrine; e.g., (Fenton & Fenton, 1937a; Buatois & Mángano, 2002, 2007; Mángano, Buatois, & Muñiz Guinea, 2005). Archaeonassa was recently reported from flysch deposits from India (Khaidem, Rajkumar, & Soibam, 2015); however, those specimens are overlapping, bilobate, convex epireliefs, likely Crossopodia M‘Coy, 1851 or Gyrochorte Heer 1865 in Heer 1864–1865. Archaeonassa ranges from the Ediacaran to recent (e.g., (Fenton & Fenton, 1937a, Jensen, Droser, & Gehling, 2005; Buckman, 1994; Martin, 2013).

Material.—IBGS PJ-M-027: one specimen, Miners Hollow; IBGS PJ-M-033: one specimen (part and counterpart), Miner's Hollow.

Diagnosis.—Concave to slightly convex furrow flanked by pair of convex ridges; central furrow wider than flanking ridges; the lateral convex ridges may be smooth or ornamented with oblique to transverse striations or smaller lobes ((Fenton & Fenton, 1937a; Buckman, 1994).

Description.—Convex furrow with concave lateral ridges in hyporelief (IBGS PJ-M-027) and concave furrow with convex lateral ridges in epirelief (IBGS PJ-M-033). Furrows 37.4-40.2 mm long, 3.7–5.4 mm wide, and 1.4 mm deep; lateral ridges 0.6–2.8 mm wide.

Occurrence.—Gray to slightly blue-gray (weathered to tan), calcareous and micaceous silty shale.

Associated ichnotaxa.—Gyrophyllites kwassizensis, Nereites cf. macleayi, Planolites montanus, and Treptichnus pedum.

Discussion.—Specimens were assigned to Archaeonassa fossulata based on the simple and smooth furrows flanked by lateral ridges in epirelief (Fig. 6.1). The specimen of Archaeonassa on IBGS PJ-M-027 occurs as a convex furrow with concave lateral ridges in hyporelief. The width and depth of the furrow and lateral ridges are not uniform. The furrow and ridges are narrower and shallower on one end than on the other, suggesting the tracemaker may have been burrowing obliquely through the sediment. The specimen on IBGS PJ-M-033 occurs as a concave furrow with convex lateral ridges (in part and counterpart).

Material.—IBGS PJ-M-002: two specimens, Miner's Hollow; IBGS PJ-M-005: three specimens, Spence Shale float, Cataract Canyon.

Diagnosis.—Smooth, curved, asymmetrical furrow in concave epirelief with or without paired convex lateral ridges along sides of furrow that may merge at furrow terminations with massive fill; infill and lateral ridges may be absent, forming depressions with terracing on trace wall.

Description.—Curved, asymmetrical furrow with convex lateral ridges in epirelief. Furrows 47.2–52.6 mm long, 11.2–38.2 mm wide, and 1.4–5.7 mm deep; lateral ridges 2.7–5.2 mm wide and 2.1–3.8 mm thick, merged at furrow terminations.

Etymology.—After Paul Jamison, who collected and donated a large number of fossil specimens used in this study.

Types.—Holotype: IBGS PJ-M-005; Paratype: IBGS PJ-M-002.

Type stratum.—Cambrian, Series 3, Spence Shale Member of the Langston Formation.

Type locality.—Miner's Hollow, west side of Wellsville Mountain: T10N, R2W, Sec. 14, NE1/4 SW1/4 and NW1/4 SE1/4 (41° 36′ 4.8″N, 112° 2′ 12.5″W).

Repository.—Division of Invertebrate Paleontology, Museum of Natural History and Biodiversity Research Center, University of Kansas, Lawrence, Kansas, USA.

Occurrence.—Two lithologies: (1) Tan to light brown, siliciclastic silty shale; and (2) gray, calcareous shale.

Associated ichnotaxa.—Phycodes curvipalmatum and Taenidium cf. satanassi.

Discussion.—Until now, Archaeonassa was monotypic. The closest published morphotype resembling A. jamisoni was from a neoichnological experiment by Jensen, Droser, and Gehling (2005, fig. 2C) that produced asymmetrical undertraces via locomotion of a marine gastropod, Nassarius (Hinia) reticulata (Linnaeus, 1758). They compared the experimental traces to specimens of Archaeonassa from the Ediacaran Ust' Pinega Formation of northwest Russia and the Ediacara Member of the Rawnsley Quartzite, Flinder's Ranges, South Australia. Jensen, Droser, and Gehling (2005) suggested that the Neoproterozoic Archaeonassa represented movement over sandy media and were analogous to the specimens generated by creeping gastropods during their experiment. Sören Jensen (personal communication, 2014) suggested that the A. jamisoni specimens were likely produced by a similar behavior. Martin (2013, fig. 6, p. 266) illustrated a modern moon-snail trace that consisted of a short, concave, asymmetrical furrow flanked by lateral ridges and greatly resembled A. jamisoni (Fig. 6.2). Jean-Bernard Caron (personal communication, 2016) suggested, however, that an ichnofossil interpretation of A. jamisoni is highly dubious due to the wide range of morphology between specimens and may actually be nodular concretions. We disagree with the nodular-concretion interpretation due to the presence of several shallow furrows that widen and deepen proximal to the specimens and taper and shallow out away from them (see Fig. 19.3). We interpret the shallow furrows to be short, entry furrows of a biogenic affinity.

Yochelson and Fedonkin (1997) noted that the original description of Archaeonassa contained two morphologies (elongate ribbon traces and rimmed pits) but restricted Archaeonassa to elongate ribbon traces and did not discuss the rimmed pits (resting traces) mentioned by Fenton and Fenton (1937a, p. 454). The rimmed pits of Archaeonassa jamisoni differ from A. fossulata due to the lack of elongate, ribbonlike furrow morphology typical of the ichnospecies. The Spence Shale material presented herein is, therefore, assigned to Archaeonassa based on comparisons to material described in Fenton and Fenton (1937a) and Buckman (1994) and discussions with S. Jensen. We interpret A. jamisoni to represent a combined locomotion and resting trace and possibly even a hunting trace of a gastropod.

Type ichnospecies.—Arenicola carbonaria Binny, 1852 by subsequent designation (Richter, 1924, p. 137).

Diagnosis.—Vertical, U-shaped burrows without spreiten, and visible as paired openings in plan view (Fürsich, 1974a; Fillion & Pickerill, 1990).

Discussion.—Arenicolites is a U-shaped burrow similar to Diplocraterion Torell, 1870, but lacks spreite between tubes (Hakes, 1976; Fillion & Pickerill, 1990). Ten ichnospecies of Arenicolites are recognized: A. brevis Matthew, 1890; A. carbonaria Binney, 1852; A. compressus (Sowerby, 1829); A. curvatus Goldring, 1962; A. longistriatus Rindsberg & Kopaska-Merkel, 2005; A. naraensis Badve & Ghare, 1978; A. sparsus Salter, 1857; A. statheri Bather, 1925; A. subcompressus (Eichwald, 1860); and A. variabilis Fürsich, 1974a. Arenicolites compressus, A. curvatus, and A. subcompressus have elliptical cross sections, and A. curvatus also has inclined limbs (Fürsich, 1974a; Chamberlain, 1977; Fillion & Pickerill, 1990). Arenicolites statheri has narrow, parallel and vertical limbs, and both A. statheri and A. naraensis have a thick wall lining (Fürsich, 1974a; Chamberlain, 1977; Fillion & Pickerill, 1990). Arenicolites sparsus typically lacks a wall lining but usually occurs only as paired openings on the tops of beds (Fürsich, 1974a). Arenicolites carbonaria consists of a small-diameter U-shaped tube with a very thin wall lining and funnel-shaped apertures (Fürsich, 1974a; Fillion & Pickerill, 1990). Arenicolites longistriatus is a U-shaped burrow that is subhorizontal after compaction and has longitudinal striations along the length of the burrow, most commonly at the base of the U-shaped tube (Rindsberg & Kopaska-Merkel, 2005).

The ichnotaxonomic status of some Arenicolites ichnospecies is currently debated. Recently, Mcllroy, Crimes, and Pauley (2005) and Callow, Mcllroy, and Brasier (2011) reexamined the type material of Arenicolites sparsus, the first ichnospecies established, and found that the depressions Salter (1857) interpreted as paired burrow apertures were in fact not paired and not connected together by a U-shaped tube. Arenicolites sparsus was reinterpreted as body fossils of small microbial mats and transferred to Beltanelliformis Menner in Keller & others, 1974 (McIlroy, Crimes, & Pauley, 2005; Callow, McIlroy, & Brasier, 2011). Menon and others (2015) later reinterpreted Beltanelliformis as a pseudofossil formed from fluid injection through the sediment and, therefore, A. sparsus is also likely a pseudofossil.

Arenicolites is considered a dwelling or suspension-feeding burrow of annelid worms or small arthropods (e.g., Hakes, 1976; Bromley & Asgaard, 1979; Fillion & Pickerill, 1990). Arenicolites has been reported mostly from shallow marine deposits, but freshwater-aquatic and deep-marine deposits have been reported as well (e.g., Crimes & others, 1977; Bromley & Asgaard, 1979; Fillion & Pickerill, 1984; Hasiotis, 2002, 2004, 2008; Ash & Hasiotis, 2013). Arenicolites ranges from the early Cambrian to recent (e.g., Crimes, 1987, 1992) with problematic specimens reported from the Neoproterozoic (e.g., Fillion & Pickerill, 1990).

Material.—IBGS PJ-M-003: multiple specimens, Spence Shale float, Cataract Canyon.

Diagnosis.—Vertical, U-shaped tubes expressed in plan view as paired depressions (concave epirelief) with small diameter limbs and funnel-shaped apertures in cross section (Fürsich, 1974a; Fillion & Pickerill, 1990).

Description.—Specimens are preserved as paired openings in concave epirelief. Apertures 1.0–2.2 mm wide, 0.7–1.1 mm deep, with variable spacing 0.7–4.1 mm. Burrow limbs are narrower than burrow openings and range 0.2–0.9 mm wide. Most limbs lack or have very thin wall linings (> 0.1 mm).

Occurrence.—Gray, massive, peloidal carbonate wackestone and packs tone to mudstone with thin continuous and discontinuous laminations of tan to brown, very fine-grained siliciclastic sandstone and siltstone. Soft-sediment deformation is present, but limestone and laminations are extensively bioturbated (ii3–4).

Associated ichnotaxa.—Conichnus conicus.

Discussion.—Specimens were assigned to Arenicolites carbonaria due to their small, paired depression morphology. These specimens occur on the same slab as the Conichnus conicus described herein, but in a horizon ∼ cm below the Conichnus specimens (Fig. 6.3). Since Arenicolites is usually indicative of shallow-marine settings (e.g., Fillion & Pickerill, 1990) and due to its close vertical proximity to the Conichnus, sample IBGS PJ-M-003 is interpreted to have been deposited in shallower water and/or higher energy settings than the other Spence Shale ichnofossils. Though complete U-shaped tubes connecting surficial depressions are not visible in areas of the massive limestone in cut slabs, one complete U-shaped tube and several partial tubes are visible in weathered sections connecting funnel shapes in the thin laminations of very fine sandstone and siltstone (Fig. 6.4).

Type ichnospecies.—Aulichnites parkerensis Fenton & Fenton, 1937b.

Diagnosis.—Convex epirelief, bilobate, ribbon trail with a medial furrow separating lobes; lower surface may show a unilobate, convex-downward shape, or as concave furrows with convex medial ridge (Fenton & Fenton, 1937b; Fillion & Pickerill, 1990).

Discussion.—Aulichnites is similar to other convex bilobate epirelief ichnotaxa, including Gyrochorte, Olivellites Fenton & Fenton, 1937c, Psammichnites Torell, 1870, and Scolicia de Quarterages, 1849. Aulichnites and Gyrochorte are composed of paired convex ridges with a medial furrow (epirelief) ; however, the ridges of well-preserved Gyrochorte have a biserial-plaited ornamentation (Häntzschel, 1975), and may occur as vertical stacks of bilobate, concave-down spreite (Heinberg, 1973, p. 231, fig. 6). Aulichnites may be similar to poorly preserved Gyrochorte specimens that lack the plaited ornamentation, like those illustrated by Heinberg (1973). D'Alessandro and Bromley (1987) and Mángano, Buatois, and Rindsberg (2002) synonymized Aulichnites under Psammichnites after interpreting Aulichnites to be a preservational variant of Olivellites, which was also considered a junior synonym of Psammichnites. Though similar, Aulichnites and Olivellites were established separately by Fenton and Fenton (1937b, 1937c) due to the presence of a medial furrow or ridge in epirelief, respectively. Chamberlain (1971) synonymized Aulichnites under Scolicia with no reason given; however, Häntzschel (1975) rejected the Chamberlain (1971) synonymy and most subsequent authors (e.g., Hakes, 1976, 1977; Fillion & Pickerill, 1990) have followed Häntzschel's rejection.

Aulichnites is interpreted as the locomotion or grazing trail of a gastropod (Fenton & Fenton, 1937b; Fillion & Pickerill, 1990); however, some authors considered them to have been produced by xiphosurids (i.e., horseshoe crabs; Yochelson & Schindel, 1978; Chisholm, 1985; Fillion & Pickerill, 1990). Aulichnites occurs in shallow- and deep-marine as well as brackish water deposits (e.g., Fenton & Fenton, 1937b; Fillion & Pickerill, 1990). Aulichnites ranges from the Ediacaran to recent (e.g., Häntzschel, 1975; Narbonne & Aitken, 1990; Crimes, 1992; Buatois & Mángano, 1993b; Jenkins, 1995; MacNaughton, 2003).

Material.—IBGS PJ-M-019: one specimen, Miner's Hollow.

Diagnosis.—Paired concave furrows separated by a medial ridge in hyporelief.

Description.—Bilobate, concave furrows separated by convex ridge in hyporelief, 7.0 mm long and 3.4 mm wide.

Occurrence.—Gray, laminated, siliciclastic or calcareous silty shale. Laminations are continuous with very little bioturbation occurring to disrupt them, indicating an ii2. The exposed bedding plane has extensive bioturbation with overprinting, indicating a (BPBI)3–4.

Associated ichnotaxa.—Dimorphichnus isp., Lockeia siliquaria, Phycosiphon incertum, Protovirgularia cf. pennatus, and Treptichnus vagans.

Discussion.—This specimen occurs as a short bilobate trail of paired concave ridges. The Aulichnites specimen terminates at a unilobate convex hyporelief mound. This mound is likely a short amygdaloidal (almond-shaped) resting trace assigned herein as Lockeia siliquaria. We consider the Aulichnites and Lockeia specimens to represent a compound trace (sensu Bertling & others, 2006) with the tracemaker having burrowed through the sediment (Aulichnites) and then stopped to rest (L. siliquaria).

Material.—KUMIP 314229, KUMIP 314231, IBGS PJ-M-020, IBGS PJ-M-021, IBGS PJ-M-029: one specimen each, Miner's Hollow; IBGS PJ-M-025, two specimens, float from Cataract Canyon.

Diagnosis.—Vertical, hemispherical, plug-shaped burrow lacking shallow, central depression at apex of the burrow (Crimes & others, 1977).

Description.—Circular to elliptical plug-shaped depressions (concave epirelief) and mounds (convex hyporelief), diameter 15.8–40.8 mm, 4.3–17.2 mm thick, and diameter/thickness (D/T) ratio 1.5–3.5. Some epirelief specimens have transverse, ledge-like constrictions along burrow wall, hyporelief specimens have smooth walls; and lack both radial ridges and a central depression (hyporelief) or knob (epirelief) on base.

Occurrence.—Gray (weathered to brown), laminated calcareous or siliciclastic silty shale and sandy shale.

Associated ichnotaxa.—Cruziana barbata, Planolites annularis, Rusophycus carbonarius, Sagittichnus lincki, and Teichichnus cf. nodosus.

Discussion.—The majority of specimens assigned to this ichnospecies occur in concave epirelief on individual slab samples. Bergaueria hemispherica specimens have smooth rounded bases that lack small knobs (concave epirelief) or depressions (convex hyporelief) characteristic to other Bergaueria ichnospecies (Pemberton, Frey, & Bromley, 1988). Ledgelike constrictions (Fig. 7.3–7.6) occur transversely along burrow wall and are similar to constrictions associated with Conostichus. Crimes and others (1977) noted a similar concentric ornamentation and suggested it represents mudrich laminations not related to tracemaker morphology. Specimens lack radial ridges that would justify assignment to B. radiata, B. perata, or even Conostichus. One B. hemispherica specimen (Fig. 7.5–7.6) does bear a strong resemblance to Conostichus broadheadi due to the presence of a well-developed conical shape and narrow apical disc but lacks the distinctive longitudinal fluting. The 1.5–3.5 D/T ratios fit with those suggested by Pemberton, Frey, and Bromley (1988) for Bergaueria.

Material.—IBGS PJ-M-026: one specimen (part and counterpart), Miner's Hollow.

Diagnosis.—Smooth walled, unlined or thinly lined, cylindrical mounds in convex hyporelief; faint ridges present radiating from a central depression may be present; diameter is generally equal to or greater than thickness (height) (Prantl, 1945; Pemberton, Frey, & Bromley, 1988).

Description.—Smooth, low relief depression (mound in convex hyporelief), 10.0 mm in diameter, 1.2 mm thick (height), and has a diameter-thickness ratio (D/T) of 8.33. No discernable radial ridges or central depressions are present.

Occurrence.—Gray (weathered to brown), calcareous silty shale.

Associated ichnotaxa.—None.

Discussion.—Only one specimen was collected and described from the Spence Shale. Bergaueria perata Prantl, 1945, was erected for unlined or thinly lined plug-shaped ichnofossils that may have diameters significantly greater than its thickness. Shallow and smooth B. aff. perata specimens may also be similar to Bergaueria sucta Seilacher, 1990–smooth, low relief, disclike basal impressions of actinians in laterally repeated sets that indicate lateral movement or creeping (Jensen, 1997). The smooth low relief and high D/T ratio is suggestive of an affinity to B. sucta, but the lack lateral repetition would preclude assignment as such.

Type ichnospecies.—Conichnus conicus Männil, 1966.

Diagnosis.—Short to long, vertical, cone-shaped to subcylindrical burrows with smooth, rounded base or randomly oriented papillalike protuberances on base; burrow infill maybe unstructured or have V-shaped laminations (Männil, 1966; Pemberton, Frey, & Bromley, 1988).

Discussion.—Conichnus is similar to several plug-shaped ichnofossils. Pemberton, Frey, and Bromley (1988) conducted a detailed review of 15 plug-shaped ichnogenera and synonymized them together into five ichnogenera; Astropolichnus, Bergaueria, Conichnus, Conostichus, and Dolopichnus. Conichnus is a conical to subcylindrical burrow with smooth walls and rounded base (C. conicus), but the base may have protuberances (C. papillatus) (e.g., Männil, 1966; Frey & Howard, 1981; Pemberton, Frey, & Bromley, 1988). Conostichus is distinguished by transverse constrictions and longitudinal fluting of the burrow wall, a basal apical disc, and a burrow diameter approximately twice its height. Bergaueria is characterized by a cylindrical to hemispherical shape, thick to thin wall linings, a central depression and/or radial ridges on the base, and a diameter twice its height. Dolopichnus is distinguished by a larger size, a central cylindrical core typically with coarser infill, bulb-shaped terminations in some, and a diameter roughly one quarter its height. Astropolichnus is a short cylinder with a diameter over three times its height, radial ridges, and a central core (Pemberton, Frey, & Bromley, 1988).

Conichnus is commonly interpreted as dwelling or resting traces of actinians (e.g., sea anemones) (e.g., Pemberton, Frey, & Bromley, 1988; Mangano & others, 2002). Most Conichnus are reported from shallow-marine deposits and tidal deposits (e.g., Frey & Howard, 1981; Hiscott, James, & Pemberton, 1984; Mángano & others, 2002). Conichnus ranges from the early Cambrian to recent (e.g., Curran & Frey, 1977; Hiscott, James, & Pemberton, 1984; Jackson, Hasiotis, & Flaig, 2016).

Material.—IBGS PJ-M-003: 12 specimens, Spence Shale float, Cataract Canyon.

Diagnosis.—Short cone- to plug-shaped depression with smooth, rounded bottom, some penetrated by vertical tube.

Description.—Short, plug-shaped depression with smooth base filled with massive, gray calcareous mudstone; 4–10 mm in diameter and 1–4 mm deep. Central-plug diameter 2.6–2.9 mm.

Occurrence.—Tan to brown, very fine-grained sandstone with ripple marks above a layer of gray peloidal carbonate wackestone and packstone to mudstone with thin, tan to brown silty to sandy laminations and soft-sediment deformation; however, no Conichnus specimens are present in the lower layer.

Associated ichnotaxa.—Arenicolites carbonarius.

Discussion.—Specimens were assigned to C. conicus for their small, pluglike morphology with smooth, rounded bottoms and lack of basal protuberances (Fig. 8.2–8.4). Conichnus conicus specimens occur on the same sample with Arenicolites carbonarius but are restricted to a higher layer. Most C. conicus specimens occur close to another specimen and falsely appear as openings to U-shaped burrows (e.g., Arenicolites or Diplocraterion, Fig. 8.2). A cut section of one specimen revealed a massive, carbonate mudstone infill penetrated by a central vertical tube (e.g., possible Skolithos; Fig. 8.3–8.4) suggesting that some C. conicus may be composite traces (i.e., two or more unrelated ichnotaxa occurring within each other; sensu Bertling & others, 2006).

Type ichnospecies.—Cruziana rugosa d'Orbigny, 1842, by subsequent designation in Miller (1889).

Diagnosis.—Elongate, bilobate, ribbonlike furrows with medial ridges (concave epirelief) or grooves (convex hyporelief): furrows commonly covered by herringbonelike, transverse, or longitudinal striations (Crimes, 1970a, 1970b; Seilacher, 1970; Häntzschel, 1975).

Discussion.—Seilacher (1970) united both bilobate long furrows and short excavations (=Rusophycus) under Cruziana due to similar striation patterns (interpreted as scratch marks) attributed to the same organism, trilobites; however, this proposal was rejected by numerous authors (e.g., Crimes, 1970a, 1970b, 1975; Fillion & Pickerill 1990; Pickerill, 1995; Jensen, 1997) due to significant morphologic differences between the two ichnogenera. Bromley and Asgaard (1979) included ribbonlike Isopodichnus Bornemann, 1889, under Cruziana because the two ichnogenera differ only in accessory features (e.g., size), which is suggested for use only in ichnospecific designation (sensu Fürsich 1974b). The Cruziana Isopodichnus synonymy, though rejected by Hakes (1985), Pollard (1985), and Seilacher (1985), is still followed by most authors. Crimes (1970b) noted that Cruziana can grade into other ichnogenera (e.g., Diplichnites, Diplopodichnus Brady, 1947, and Rusophycus) and that the V-shaped striations open in the direction of movement as with Diplichnites.

Cruziana is commonly interpreted as a surficial to shallow deposit-feeding, dwelling, grazing, locomotion, or predation trace (e.g., Crimes, 1970a, 1970b; Seilacher, 1970; Zonneveld & others, 2002; Gingras & others, 2007). Most Cruziana have been interpreted as the product of trilobites but other tracemakers have been suggested; nontrilobite arthropods (e.g., horseshoe crabs, branchiopods, aglaspidids), or even some vertebrates (e.g., Seilacher, 1970; Fisher, 1978; Shone, 1978, 1979; Bromley & Asgaard, 1979, Pollard, 1985). Cruziana has been reported in deep- and shallow-marine and continental deposits (e.g., fluvial, lacustrine, and brackish) (e.g., Crimes, 1970a, 1970b; Bromley & Asgaard, 1979; Seilacher, 1985; Pillion & Pickerill, 1990; Pickerill, 1995). Cruziana ranges from the early Cambrian to the Cretaceous (e.g., Crimes, 1987, 1992; Mangano & others, 2002; Hasiotis, 2012).

Material.—KUMIP 314229; eight specimens, Spence Shale, Miner's Hollow, Wellsville Mountains, Utah, USA.

Diagnosis.—Small to medium, straight to curved, bilobate ribbonlike furrow with medial ridge and curved V-shaped striations angled ∼60° (Seilacher, 1970; Legg, 1985).

Description.—Bilobate, concave epirelief, ribbon trails; 27.0– 94.4 mm long and 9.8–11.9 mm wide. Curved striations are visible in several specimens and have a V-shaped angle 142–163°.

Occurrence.—Greenish gray (weathered to brown) calcareous, micaceous silty shale.

Associated ichnotaxa.—Bergaueria hemispherica, Planolites annularis, and Rusophycus carbonarius.

Discussion.—Specimens assigned to C. barbata partly crossover other C. barbata specimens on the same sample along their lengths causing some lobes to be lost and give the appearance of a trilobate form, but the specimens can be differentiated, as the V-shaped striations are oriented opposite to the overlapping furrow (Fig. 9.1). Several trilobite pygidia are present on the sample; however, their widths are greater than the widths of the C. barbata specimens indicating that those trilobites were not the producers (sensu Fortey & Seilacher, 1997). Spence Shale specimens of C. barbata are significantly smaller (∼1 cm) than most previously recorded specimens (∼3–9 cm; Legg, 1985; Orłowski, 1992). The decreased size is likely the result of lower available oxygen near the sediment-water interface (e.g., G arson & others, 2012).

Material.—KUMIP 204523 A (part) and B (counterpart): 31 specimens, Miners Hollow; KUMIP 314228; two specimens, Miner's Hollow; IBGS PJ-M-007: five specimens, Miners Hollow; IBGS PJ-M-016: two specimens, Miners Hollow; IBGS PJ-M-017: one specimen, Miners Hollow float.

Diagnosis.—Small to large, straight to curved, bilobate ribbonlike furrow with medial ridge and transverse striations (Bromley & Asgaard, 1979; Fillion & Pickerill, 1990; Jensen, 1997).

Description.—Concave or convex, bilobate, ribbonlike burrows with a medial ridge (epirelief) or furrow (hyporelief) and transverse striations; Burrows 11.4–95.1 mm long and 8.0–15.4 mm wide. Striation V-shaped angle ∼80° but some range from 145–160°. Burrow paths are typically slightly curved to straight, but several burrows are highly curved and overlap or crosscut each other.

Occurrence.—Greenish gray to gray laminated, calcareous silty to sandy shale; sometimes weathered to brown or brownish yellow.

Associated ichnotaxa.—Lockeia siliquaria, Monomorphichnus lineatus, M. cf. multilineatus, Planolites beverleyensis, P. montanus, Rusophycus carbonarius, Rusophycus cf. cerecedensis, Treptichnus bifurcus, and T. pedum.

Discussion.—Bromley and Asgaard (1979) placed ribbonlike Isopodichnus Bornemann, 1889, under Cruziana problematica because size was not enough to warrant a separate ichnogenus. Some authors, however, retain Isopodichnus for use as a salinity indicator in fresh- and brackish-water settings (e.g., Hakes 1985; Pollard 1985; Seilacher 1985, 2007). Bromley and Asgaard (1979) also noted that Isopodichnus was reported from marine deposits by Alpert (1976a) and Trewin (1976), thus, making retention of Isopodichnus as a salinity indicator invalid. Jensen (1997) attempted to distance the ichnospecies from the common interpretation as a salinity indicator by placing it under a resurrected name, Cruziana tenella (Linnarsson, 1871) (for discussion, see Jensen, 1997). Reassignment of C. problematica to C. tenella has been accepted by some authors (e.g., MacNaughton & Narbonne 1999; Jensen, Droser, & Heim, 2002; Zonneveld & others, 2002; Sadlok, 2010), but rejected by others for nomenclatural stability (e.g., Mángano & others, 2002; Schatz & others, 2011). We reject the renaming of C. problematica to C. tenella in favor of nomenclatural stability, even though the use of ichnotaxa as environmental stress indicators is not valid to establish, rename, or retain ichnotaxa.

Cruziana problematica specimens show some meandering, suggesting they were produced via grazing, and are noticeably larger than R. carbonarius (Fig. 9.3–9.4, Fig. 10.1–10.5). The average width of C. problematica is 10 mm, whereas R. carbonarius averages ∼5 mm wide. The width difference suggests that C. problematica tracemakers were not the same as the tracemakers of R. carbonarius (sensu Fortey & Seilacher, 1997), which could be juveniles of the adult form (Cruziana producers). Cruziana problematica and C. problematica-sized Rusophycus specimens do not occur together on KUMIP 204523, although one association does occur on KUMIP 314228 (see Fig. 9.4). The specimens of Cruziana problematica on KUMIP 204523 co-occur with Rusophycus carbonarius, Planolites montanus, and Treptichnus bifurcus and were likely not constructed at the same time and may have been affected by sudden changes in available oxygen or nutrients. Rusophycus carbonarius specimens crosscut both C. problematica and other R. carbonarius (Fig. 10.1), whereas Cruziana problematica specimens only crosscut each other (Fig. 10.3). Planolites montanus crosscuts both C. problematica and R. carbonarius (Fig. 10.4). The crosscutting relationships suggest that C. problematica were constructed and abandoned first, followed by R. carbonarius, and then finally, P. montanus. The T. bifurcus specimen was constructed sometime after the C. problematica as the latter was cross cut by the former (Fig. 10.5), but its placement in the aforementioned crosscutting timeline is unknown because the T. bifurcus specimen has no interaction with any other specimen.

Type ichnospecies.—Dimorphichnus obliquus Seilacher, 1955a.

Diagnosis.—Asymmetrical trackways with two types of impressions, typically of equal width; (1) long, thin, straight to sigmoidal striations; and (2) short, punctate to elliptical impressions at end of long striations; both types occur oblique to direction of movement (Seilacher, 1955a; Fillion & Pickerill, 1990).

Discussion.—Seilacher (1955a) named Dimorphichnus for oblique sets of elongate striations with punctate impressions produced by trilobites. The movement of the Dimorphichnus tracemaker was oblique to fully sideways with the short, punctate impressions formed by one set of legs acting as a holdfast to keep the tracemaker in place, while the sigmoidal striations were formed by the other set of legs sweeping through the medium returning to their starting position (Seilacher, 1955a, 2007). Crimes (1970a, 1970b) suggested the oblique to sideways orientation of Dimorphichnus was due to increased current energy forcing the tracemaker to reorient itself to remain stable while moving or grazing. After Monomorphichnus was described by Crimes (1970b), Seilacher (1985) argued that Monomorphichnus was a junior synonym of Dimorphichnus and the Monomorphichnus holotype contained punctate impressions consistent with Dimorphichnus. Most authors have rejected this suggestion and maintain both as separate ichnogenera (e.g., Walter, Elphinstone, & Heys, 1989; Fillion & Pickerill, 1990; Orłowski, 1992; Jensen, 1997; Hofmann & others, 2012). More recently, Seilacher (2007) proposed that Dimorphichnus and Monomorphichnus should be considered as a behavioral and preservational variant of Diplichnites, respectively. Jensen (1997) and Hofmann and others (2012) suggested that Dimorphichnus and Monomorphichnus should remain separate due to each representing a separate behavior.

Dimorphichnus is interpreted as a locomotive, deposit feeding, or grazing trace (Seilacher, 1955a, 1985; Crimes, 1970b; Fillion & Pickerill, 1990). Proposed producers of Dimorphichnus include marine and continental arthropods (e.g., trilobites, decapods, centipedes, millipedes) (Fillion & Pickerill, 1990). Dimorphichnus has been reported from shallow-marine, deep-marine, and continental deposits (e.g., alluvial, lacustrine, and eolian) (e.g., Seilacher, 1955a; Fillion & Pickerill, 1990). Dimorphichnus ranges from the Cambrian to recent (e.g., Crimes, 1970b).

Material.—IBGS PJ-M-019; one specimen, Miner's Hollow; IBGS PJ-M-024: one specimen, Miner's Hollow.

Diagnosis.—Small, thin, laterally repeated sets of elongate, sigmoidal striations (convex hyporelief) with separate blunt, ovoid to circular mounds occurring near end of elongate striations.

Description.—Specimens consist of thin convex ridges and separate ovoid to punctate mounds near the ridge ends. Trackways 19.6 mm long, 7.1 mm wide. Sigmoidal striations 4.0–6.2 mm long, 0.2–0.4 mm wide. The blunt mounds 0.8–2.0 mm long, 0.4–0.6 mm wide.

Occurrence.—Gray, laminated, siliciclastic or calcareous silty shale. Laminations are continuous with very little bioturbation occurring to disrupt them, indicating an ii2. The exposed bedding plane has extensive bioturbation with some overprinting, indicating a BPBI 3–4.

Associated ichnotaxa.—Aulichnites isp., Lockeia siliquaria, Phycosiphon incertum, Planolites annularis, P. montanus, Protovirgularia cf. pennatus, Rusophycus carbonarius, Sagittichnus lincki, and Treptichnus vagans.

Discussion.—The specimens of Dimorphichnus are very diminutive in size with sigmoidal striation. Pusher mound widths are <1.0 mm (Fig. 10.6). The Dimorphichnus isp. on IBGS PJ-M-019 does not crosscut any recognizable traces. The extensive bioturbation of the base of IBGS PJ-M-019 makes identification of ichnotaxa difficult and suggests a more oxygenated environment than the shallower laminations yielding Phycosiphon incertum.

Type ichnospecies.—Diplichnites aenigma Dawson, 1873.

Diagnosis.—Simple trackways of punctate to elongate track impressions in parallel track rows; track impressions closely and regularly spaced, and normal or oblique to trackway axis (Häntzschel, 1975; Briggs, Rolfe, & Brannan, 1979; Fillion & Pickerill, 1990).

Discussion.—Originally interpreted as trails of large myriapods or annelids by Dawson (1873), recent authors have used Diplichnites to describe smaller-scaled trackways thought to be produced by trilobites (Fillion & Pickerill, 1990). Briggs, Rolfe, and Brannan (1979) suggested that Diplichnites be restricted to continental arthropod trackways because they noted that workers were departing from the original diagnosis of Diplichnites as a continental trackway and suggested using some junior synonyms of Diplichnites from Osgood (1970) to place the trilobite-produced trackways.

Nine ichnospecies are currently recognized within the literature (e.g., Buatois & others, 1998; Smith & others, 2003): Diplichnites aenigma Dawson, 1873; D. binatus Webby, 1983; D. cuithensis Briggs, Rolfe, & Brannen, 1979; D. govenderi Savage, 1971; D. gouldi (Gevers in Gevers & others, 1971); D. incertipes (Matthew, 1910); D. minimus Walter & Gaitzsch, 1988; D. minor (Matthew, 1910), and D. triassicus (Linck, 1943). Track orientation and shape, number of tracks per track series, and number of track series per track row are generally used to differentiate ichnospecies (e.g., Savage, 1971; Trewin & McNamara, 1995). Trewin and McNamara (1995) divided D. gouldi into three morphotype end-members (types A, B, and C) based on trackway width and the number of tracks per track series.

Diplichnites is generally interpreted as a locomotion trace of trilobites but other arthropods, including myriapods, and some annelids have been suggested (e.g., Dawson, 1873; Osgood, 1970; Briggs, Rolfe, & Brannen, 1979). Diplichnites is found in shallowand deep-marine, and continental deposits (e.g., Crimes & others, 1977; Fillion & Pickerill, 1990; Crimes & Fedonkin, 1994). Deep-marine Diplichnites is mostly reported from the lower and middle Cambrian and only rarely after the Cambrian (Pickerill, 1981; Crimes & Fedonkin, 1994). Diplichnites ranges from the Cambrian to recent (e.g., Briggs, Rolfe, & Brannen, 1979; Crimes, 1987, 1992; Fillion & Pickerill, 1990; Hasiotis, 2012).

Material.—KUMIP 204522: one specimen, Antimony Canyon; IBGS PJ-M-011: one specimen, Spence Tongue of the Lead Bell Shale, Oneida Narrows, Bear River Range, Idaho, USA; IBGS PJ-M-014 (part and counterpart) and IBGS PJ-M-015: one specimen, Miner's Hollow.

Diagnosis.—Paired rows of punctate to ellipsoidal or elongated straight impressions oriented perpendicular or oblique to trackway axis; track series consist of 5–9 tracks in opposition. Within track rows, multiple sets of track impressions may overlap previous sets (Trewin & McNamara, 1995; Buatois & others, 1998; Smith & other, 2003).

Description.—Trackways 32.1–49.0 mm long; outer trackway 10–15 mm wide, inner trackway 8.4–9.5 mm wide. Punctate to ellipsoidal tracks 2–4 mm wide, spaced 2.5–4.0 mm apart. Specimens with overlapping track series, overlap occurs by 2–3 tracks, overlap distance 1.5–2.9 mm.

Occurrence.—Two lithologies: (1) gray to dark gray (weathered to tan), very fine to fine carbonate sand to silty shale; and (2) pale greenish gray, mica-rich, silty to sandy shale. Thin to thick laminations are present, but are unbroken or have rare traces in slab samples (ii1–2). Bedding plane is only disrupted by D. gouldi (BPBI 2).

Associated ichnotaxa.—Planolites montanus and Treptichnus vagans.

Discussion.—Diplichnites gouldi was originally described by Gevers in Gevers and others (1971) for paired, parallel rows of punctate to ellipsoidal track impressions under the name Arthropodichnus gouldi. Gevers (1973) changed the name from Arthropodichnus to Beaconichnus since Arthropodichnus was already proposed for another ichnogenus. Bradshaw (1981) transferred Beaconichnus gouldi into Diplichnites as D. gouldi. Trewin & McNamara (1995) recognized three end-members (types A, B, and C) with material assigned to D. gouldi based on trackway widths and tracks per series. Buatois and others (1998), however, considered that D. gouldi type A did not belong in Diplichnites and viewed it as a form of Umfolozia Savage, 1971, while retaining D. gouldi types B and C. Smith and others (2003) suggest retaining all three end-members of D. gouldi, with which we agree.

Häntzschel (1975) placed Acripes Matthew, 1910, within Diplichnites due to similar morphology. Miller (1996) reviewed type material of Acripes and confirmed its placement in Diplichnites but made no reference or recommendation on whether all three Acripes ichnospecies should remain valid under Diplichnites. Some authors have included A. incertipes, A. leavitti, and A. minor as valid ichnospecies within Diplichnites (e.g., Keighley & Pickerill, 1998; Smith & others, 2003). Keighley and Pickerill (1998) recommended that A. incertipes (Matthew, 1910, pl. III, fig. 1–2) should not be included in Diplichnites due to significantly different track impression shapes of each track row similar to Dimorphichnus, Petalichnus, and Ptilichnus.

The ichnospecies of Matthew (1910), Acripes incertipes (sensu stricto; plate III, fig. 1), A. leavitti, and A. minor, are morphologically almost identical to Diplichnites gouldi. Each ichnospecies are paired, parallel trackways with punctate, opposite track impressions in series that may overlap and are differentiated primarily by size. We suggest that they should be grouped under a single ichnospecies, Diplichnites gouldi, as it: (1) has the most similar morphology to Acripes; (2) is the most commonly used in the literature; and (3) would help stabilize the nomenclature regarding Diplichnites.

Specimens assigned to Diplichnites gouldi type A consist of small, punctate to ellipsoidal track impressions. Most D. gouldi type A specimens occur with specimens of Planolites montanus, but one specimen is present alongside Monomorphichnus bilinearis as well as P. montanus (IBGS PJ-M-011). Most trackways are straight to gently curved, with the track series being most apparent in the curved sections. Some specimens have punctate tracks (Fig. 11.1); however, tracks are typically ellipsoidal and oriented ∼45–90° from the trace axis (Fig. 11.2–11.3). Several of the ellipsoidal-track specimens show track impressions of both track rows that are oriented parallel in a single direction suggesting bottom currents influenced the movement of the tracemakers (Trewin & McNamara, 1995; Smith & others, 2003; Seilacher, 2007).

Material.—KUMIP 204521: one specimen (part and counterpart), Miner's Hollow.

Diagnosis.—Paired rows of thin, straight, elongated striations grouped in pairs or triplets oriented obliquely to the trackway axis; track impression morphology may be asymmetric (Webby, 1983; Buatois & others, 1998).

Description.—The left track row (relative to inferred tracemaker movement) is poorly preserved compared to the right track row. Trackway 153 mm long; outer trackway 23.8 mm wide, and inner trackway 18.4 mm wide. Thin, elongate striations 7.6–12.2 mm long, 0.6–1.6 mm wide, and spaced 1.2–5.9 mm apart. Track impressions oriented 45° from the central axis with a ∼90° V-shaped angle.

Occurrence.—Dark gray (weathered to tan) to pale greenish gray, very fine- to fine-grained carbonate silty shale.

Associated ichnotaxa.—Diplichnites cf. govenderi and Protovirgularia cf. pennatus.

Discussion.—The specimen assigned to Diplichnites cf. binatus occurs with other surficial arthropod trackways. The specimen is crosscut by a paired-row trackway with highly variable track impression morphologies, which ranges between punctate to apostrophelike to bifid to trifid morphologies of Keighley and Pickerill (1998) that is herein assigned to D. cf. govenderi. The D. cf. binatus specimen is poorly preserved and only one track row is clearly visible (Fig. 11.4), but shows a clear V-shape angle to indicate the tracemaker moved from right to left (relative to the image). Some of the elongate tracks occur in close pairs, which justify placement under D. binatus; however, some impressions are singular and others are in groups of three.

Diplichnites cf. binatus bears a resemblance to Pterichnus Hitchcock, 1865, as both ichnospecies have track impressions that are elongate and thin; however, D. cf. binatus commonly has asymmetrical impressions (Buatois & other, 1998), whereas the impressions of P. tardigradus are usually always symmetrical (Hitchcock, 1858, 1865; Gaillard & others, 2005). Minter, Mángano, and Caron (2012) suggested that Pterichnus and other similar V-forming trackways described by Hitchcock (1858, 1865) were actually undertracks and should be considered junior synonyms of Lithographus Hitchcock, 1858.

Material.—KUMIP 204521 A and B: two specimens, Miner's Hollow.

Diagnosis.—Paired rows of lunate to tapered to bifid track impressions oriented perpendicular to oblique to trackway axis; tracks may be opposite or staggered.

Description.—Trackways 47–190 mm long; outer trackways 30.6–45.3 mm wide, and inner trackway 9.5–15.8 mm wide. Lunate to tapered, bifid track impressions 3.6–12.2 mm long, 0.8–1.6 mm wide, and spaced 2.6–13.0 mm apart. Specimens lack overlapping series and form single-series track rows.

Occurrence.—Dark gray (weathered to tan) to pale greenish gray, very fine- to fine-grained calcareous silty shale. No visible bedding or laminations are present. Low to moderate bedding plane disruption by traces indicating BPBI 2.

Associated ichnotaxa.—Diplichnites cf. binatus and Protovirgularia cf. pennatus.

Discussion.—The specimen assigned to this ichnospecies has highly variable track impressions that make classification difficult; however, the closest ichnotaxa to which the Spence Shale material can be assigned are Diplichnites govenderi, Incisifex Dahmer, 1937, Lithographus or Permichnium Guthorl, 1934. The specimens differ from Incisifex because the track impressions are typically straight and elongate, whereas D. cf. govenderi have a mix of bifid, lunate, and elongate impressions (Häntzschel, 1975). The specimen differs from Lithographus because none of the track impressions have the trifid to J-shaped track impressions, whereas the holotype of D. govenderi (Savage, 1971, fig. 7A) shows lunate-shaped track impressions similar to those seen in the Spence Shale specimens. Permichnium differs from D. cf. govenderi as the track impressions are typically bifid and open either to the outside or inside of the trackway (Kramer & others, 1995), whereas D. cf. govenderi has multiple impression shapes.

A “quadrifid” track impression is present and is likely two tracks overprinting each other, composed of two bifid grooves that intersect near the outer margin of the trackway (Fig. 11.5). The quadrifid impression was likely produced via a two-part limb motion. First, an insertion of a bifid limb into the medium, which moved obliquely inward and to the posterior of the trackway, as indicated by a raised sediment mound near the end of the impression. Later, a second insertion that shifted obliquely inward toward the anterior of the trackway, which resulted in overlapping bifid impressions.

Type ichnospecies.—Gordia marnia Emmons, 1844, by original monotypy.

Diagnosis.—Smooth, winding but not meandering, unbranched, cylindrical burrows with common overcrossings and massive infill (Fillion & Pickerill, 1990; Wang & others, 2009).

Discussion.—Gordia was originally described and named for its resemblance to the freshwater hairworm, Gordius Linnaeus, 1758, but a poor definition caused some authors to view Gordia as nomen nudum (Emmons, 1844; Fillion & Pickerill, 1990). Hall (1847) provided a new description, which provided the diagnosis for Gordia as an ichnofossil (Fillion & Pickerill, 1990). Buatois and others (1998) suggested the synonymy of Haplotichnus Miller, 1889, under Gordia due to similar path irregularity and burrow overlap, even though Haplotichnus has frequent sharp bends in the burrow and rarely crosses itself. They considered the sharp bends in Haplotichnus to represent only a minor behavioral difference that yielded only an accessory feature (sensu Fürsich, 1974b; Buatois & others, 1998) and did not warrant separation. The sharp, irregular bends, however, are major architectural differences (sensu Hasiotis & Mitchell, 1993; Hasiotis, Mitchell, & Dubiel, 1993), as the sharp-angle bends and rare self-crossings are ichnotaxonomically significant at the ichnogeneric level. We, therefore, reject the synonymy of Haplotichnus within Gordia, and retain Haplotichnus as a separate ichnotaxon.

Gordia is commonly interpreted as a locomotion, depositfeeding, or grazing trace of annelid worms or other wormlike organisms, arthropods, or nematodes (e.g., Emmons, 1844, Buatois & Mángano, 1993b). Gordia is a one of most common faciescrossing ichnofossils known and has been reported from almost every depositional environment in deep and shallow marine, as well as, from estuarine, fluvial, and lacustrine deposits (e.g., Fillion & Pickerill, 1990; Buatois & Mángano, 1993b; Uchman, Kazakauskas, & Gaigalas, 2009; Jackson, Hasiotis, & Flaig, 2016). Gordia ranges from the Ediacaran to recent (Crimes & Anderson, 1985; McCann & Pickerill, 1988; Fillion & Pickerill, 1990; Wang & others, 2009; Hasiotis & others, 2012).

Material.—IBGS LG-M-006; one specimen; IBGS PJ-M-004; one specimen, Miners Hollow.

Diagnosis.—Thin, arcuate to winding burrows or trails with self-overcrossing patterns (De Gibert & others, 2000).

Description.—Winding burrows in convex epi- or hyporelief or in concave epirelief with multiple, arcuate, self-overcrossing trails. Burrows 4.2–38.4 mm long, 0.3–1.1 mm wide.

Occurrence.—Laminated, greenish gray (weathers to brown or yellowish brown), mica-rich siliciclastic shale with thin laminations of dark gray sandy shale. One specimen occurs in a BST carbonaceous film of Banffia sp. (J.B. Caron, personal communication, 2016).

Associated ichnotaxa.—None.

Discussion.—The occurrence G. marnia within the BST film (Fig. 12.1, 12.3) suggests that anoxic conditions were present for a period long enough to allow the Banffia sp. to decay into a BST carbon film before oxic or dysoxic conditions returned, allowing the Gordia tracemaker to feed off the remaining organic matter (sensu Wang & others, 2009; Garson & others, 2012). The numerous overlapping burrow segments on IBGS PJ-M-004 suggests a high concentration of detrital organics in the sediment (Fig. 12.2, 12.4).

Type ichnospecies.—Gyrophyllites kwassizensis Glocker, 1841.

Diagnosis.—Vertical to oblique shaft with numerous radiating club- to leaf-shaped tunnels or lobes on staggered levels and usually unbranched; each lobe may have been backfilled (Uchman, 1998).

Discussion.—Gyrophyllites is very similar to numerous rosetteshaped ichnofossils. Głuszek (1998) noted that Gyrophyllites bears a strong resemblance to Asterosoma Otto, 1854, when viewed in plan view where only one level of Gyrophyllites is viewed. Some authors have noted that Gyrophyllites looks similar to both Asterichnus Bandel, 1967, and Stelloglyphus Vialov, 1964 (e.g., Uchman, 1998, Le Roux, Nielson, & Henríquez, 2008). Similarities between Atollites Maas, 1902, and Gyrophyllites have been noted as both have radiating lobes and a theorized helical structure (Seilacher, 1977; Serpagli, 2005). However, the lobe terminations in Atollites are more spherical than club shaped or straight compared to Gyrophyllites. Lorenzinia Gabelli, 1900, is composed of radiating burrows with a large flat central area separating the inner burrow terminations and has no apparent central shaft (Häntzschel, 1975). Fürsich and Bromley (1985) reinterpreted Dactyloidites Hall, 1886, and remarked on its superficial similarity to Gyrophyllites and other rosette ichnofossils, but noted that Dactyloidites contained radial spreiten. The figures in Fürsich and Bromley (1985, fig. 7, 8, & 10), however, show vertically to sub vertically stacked spreiten with the exception of D. asterioides. Though commonly illustrated as a three-dimensional helical structure (e.g., Häntzschel, 1975, p. 66, fig. 40.2b), Gyrophyllites is thought by some to be a rosette trace occurring in multiple stories, with each restricted to a single bedding plane and connected by a central tube (e.g., Fürsich & Kennedy, 1975; Le Roux, Nielson, & Henriquez, 2008; Strzebonski & Uchman, 2015).

Gyrophyllites is interpreted as the feeding burrow system of a wormlike deposit feeder, such as polychaete and echiuran worms (e.g., Chamberlain, 1975; Fürsich & Kennedy, 1975; Mángano, Buatois, & Muñiz Guinea, 2005; Le Roux, Nielson, & Henriquez, 2008; Strzebonski & Uchman, 2015). Fürsich and Kennedy (1975) suggested that Gyrophyllites was produced preferentially in silty and clayey layers as the tracemaker mined sediment for food and stopped excavation when sand-rich layers were encountered. Gyrophyllites is most commonly reported from deep-marine flysch and fan overbank deposits but has also been reported from shallow-marine deposits (e.g., Wetzel & Uchman, 1997; Uchman, 1998; Seilacher, 2007; Strzebonski & Uchman, 2015). Gyrophyllites ranges from the Cambrian to Eocene (Mángano, Buatois, & Muñiz Guinea, 2005; Strzebonski & Uchman, 2015).

Material.—KUMIP 314143; two specimens, Cataract Canyon; KUMIP 314162; one specimen, Miners Hollow; KUMIP 314223; one specimen, Antimony Canyon; IBGS PJ-M-022: one specimen, High Creek Canyon, Bear River Range, Utah, USA; IBGS PJ-M-033: one specimen, Miners Hollow.

Diagnosis.—Horizontal, straight to club-shaped lobes radiating from single point; may have burrow fills of different color from host lithology, thin ring of disturbed sediment surrounding radiating lobes, and/or lobes that appear bifurcated.

Description.—Endorelief, concave epirelief, and convex hyporelief rosettes with 7‐19 straight to club-shaped lobes radiating from a central shaft. Rosettes 16.4–42.5 mm diameter; Lobes 3.9–20.8 mm long, 1.4–11.0 mm wide. Lobes commonly separate but may bifurcate, overlap, or be amalgamated together. Central shaft is only visible on one specimen as a small dark circle, 1.1 mm diameter.

Occurrence.—Two lithologies; (1) greenish gray (weathered to brown) siliciclastic silty to sandy shale and may have black to brown dendrites; and (2) dark gray (weather to brown), laminated calcareous silty shale. No visible bedding or laminations present; low to moderate bedding plane disruption (BPBI 2).

Associated ichnotaxa.—Planolites beverleyensis, Rusophycus carbonarius, Sagittichnus lincki, and Treptichnus bifurcus.

Discussion.—Most specimens assigned to G. kwassizensis occur individually; however, on one slab sample, two endorelief specimens are present and in close proximity (Fig. 13.1–13.2). Only two slab specimens have G. kwassizensis with other ichnotaxa (Fig. 13.3–13.5). Two specimens occur as flat endoreliefs (see Fig. 13.1–13.2). Fill of both rosettes is slightly finer and a lighter color than the surrounding matrix. The lobe shape of each specimen is variable. One specimen has wide lobes with indistinct margins, whereas the other has thinner lobes with distinct margins. At the center of the thin-lobed specimen is a small dark circle, which we interpret as the central tube that would have connected to the next tier and where the tracemaker resided.

One collector and donor, Phillip Reese, originally identified a medusoid fossil specimen (Fig. 13.6) as Brooksella Walcott, 1896, which was stored in the KUMIP since 1989 and only recently was reinterpreted as Gyrophyllites by R. A. Robison. Most authors follow the suggestion of Häntzschel (1975) and consider Brooksella to be a body fossil, rather than an ichnofossil. Some authors have retained Brooksella as a valid medusoid ichnogenus (e.g., Willoughby & Robison, 1979; Jensen, 1997), whereas others (e.g., Fürsich & Bromley, 1985) consider Brooksella to be a junior synonym of Dactyloidites Hall, 1886. This specimen has a sandy outer rim surrounding the central, radiating lobes, likely due to the organism having made contact with a sandier layer and stopped excavation (Fürsich & Kennedy, 1975).

Willoughby and Robison (1979) reported four specimens of Brooksella from the Spence Shale (Spence Tongue of the Lead Bell Shale of Idaho). Three specimens (Willoughby & Robison, 1979, fig. 1A—C) belong to Gyrophyllites. The fourth (Willoughby & Robison, 1979, fig. 1D) belongs to Dactyloidites as it consists of six radiating lobes with small tubes or tube plugs in the distal ends of the lobes, similar to the specimen of Dactyloidites asterioides Fitch, 1850, figured by Häntzschel (1975, p. 145, fig. 88).

Type ichnospecies.—Halopoa imbricata Torell, 1870, designated by Häntzschel, 1975.

Diagnosis.—Long, horizontal burrows covered with irregular longitudinal ridges or wrinkles; may include multiple overlapping cylindrical probes (Uchman, 1998).

Discussion.—Halopoa is considered by multiple authors to be very similar to Fucusopsis Palibin in Vasseoevich, 1932, causing each ichnogenus to be transferred back and forth into the other (e.g., Hakes, 1976; Jensen, 1997; Uchman, 1998). Both ichnogenera are described as long, straight to curved, horizontal burrows with longitudinal striations or wrinkles. Hakes (1976) compared and noted that poorly preserved specimens of Fucusopsis, Halopoa, and Scoyenia White, 1929, would be difficult to differentiate. Fucusopsis was synonymized with Palaeophycus and split between P. striatus and P. sulcatus (Pemberton & Frey, 1982). Jensen (1997) argued that Halopoa imbricata was similar to both Fucusopsis and P. sulcatus and partially followed the synonymy of Pemberton and Frey (1982), regarding H. imbricata as a valid ichnospecies within Palaeophycus (i.e., P. imbricatus). Jensen (1997) agreed with the Osgood (1970) interpretation that longitudinal striations on the burrow were caused by sediment deflection and lamination rupture as the tracemaker burrowed through the medium. Jensen (1997) considered them not very useful for ichnotaxonomic assessment as the surficial morphology reflected properties of the sediment. He also noted that there were (rare) spreiten present in H. imbricata but disregarded the fact that spreite are usually an indicator of active burrowing (sensu Fürsich, 1974b).

Uchman (1998) argued for the retention of Halopoa, noting the striations of Fucusopsis and Halopoa were likely produced by active digging, passive dragging of body parts due to body shape, or the sediment deflection-lamina rupture method proposed by Osgood (1970). He considered each to represent unique behaviors that generated a unique morphology. Uchman also noted several Halopoa specimens had Teichichnus-like, vertically stacked, overlapping probes (spreiten), but maintained Halopoa and Teichichnus as separate, arguing that Teichichnus generally lacks external ornamentation and that the spreiten in Halopoa were not as developed. He argued against the Pemberton and Frey (1982) synonymy, noting Halopoa lacked any type of wall or lining that would warrant placement within Palaeophycus. We herein follow the Uchman (1998) retention of Halopoa.

Three ichnospecies of Halopoa are known; H. annulata (Książkiewicz, 1977), H. imbricata, and H. storeana Uchman, 2001. The primary feature that separates H. imbricata from H. storeana is the orientation of the surficial wrinkles (ridges). The wrinkles of H. imbricata are parallel to subparallel to the trace axis, whereas the wrinkles on H. storeana have a plaited pattern (Uchman, 2001). Halopoa annulata is differentiated from H. imbricata and H. storeana by occasional branching and the presence of transverse annulations producing an undulatory pattern along the burrow (Uchman, 1998, 2001).

Commonly interpreted as the feeding burrow of an infaunal deposit feeder, Halopoa tracemakers may include annelid worms, enteropneusts, echiurans, and holothurians (e.g., Hakes, 1976; Uchman, 1998; Zonneveld, Gingras, & Beatty, 2010). Uchman (2001) interpreted Halopoa as a grazing trace. Halopoa is most commonly found in sandstone turbidites of deep-marine flysch deposits (e.g.. Uchman, 1998); however, some have been reported from shallow-marine deposits (e.g., Jensen, 1997) and tidal flats (e.g., Mangano & others, 2002). Halopoa ranges from the early Cambrian to middle Miocene (Jensen, 1997; Uchman, 1998).

Material.—IBGS LG-M-012: three specimens, Box Elder Canyon, Wellsville Mountains, Utah, USA

Diagnosis.—Long, horizontal burrows covered with irregular, longitudinal ridges (Uchman, 1998).

Description.—Horizontal, convex hyporelief burrows with irregular-shaped ridges and furrows or wrinkles along the length of the burrow. Burrows 11.0–70.0 mm long, 1.6–2.7 mm wide. Burrows overlap each other to form pseudobranching.

Occurrence.—Gray (weathered to brown) calcareous silty shale.

Associated ichnotaxa.—Planolites montanus and Treptichnus vagans.

Discussion.—Ichnofossils are primarily assigned to Halopoa aff. imbricata due to the longitudinally wrinkled texture of the outer burrow margins and the lack of transverse annulations or a plaited pattern (Fig. 14.1). The nature of the burrow fill is unknown, and the burrows are poorly preserved, convex hyporeliefs. Burrows show overlapping to form pseudobranching, but some possible branching (i.e., secondary successive branching; sensu Keighley & Pickerill, 1995) may be present. Analysis of the fill is needed to confirm the type of branching, if present.

Type ichnospecies.—Lockeia siliquaria, James 1879.

Diagnosis.—Amygdaloidal- to ovoid-shaped mounds (convex hyporelief) or depressions (concave epirelief) that taper at one or both ends; surface usually smooth but may be irregular; may have a medial longitudinal crest (hyporelief) or groove (epirelief) (Osgood, 1970; Fillion & Pickerill, 1990; Mángano & others, 2002).

Discussion.—Lockeia was the subject of much debate when reintroduced into ichnotaxonomy. Osgood (1970) considered Lockeia as the senior synonym for almond-shaped resting traces and considered Pelecypodichnus Seilacher, 1953a, to be a subjective junior synonym. Numerous authors have followed this suggestion (e.g., Häntzschel, 1975, Hakes 1976, Mángano & others, 2002). Other authors, however, continued to used Pelecypodichnus after Eagar (1974) argued that Lockeia was nomen oblitum citing the International Code of Zoological Nomenclature rule (ICZN 1964, 2nd edition, Article 31) requiring a figure or illustration, alongside the original description, to be a valid taxon (Hakes, 1976; Bromley & Asgaard, 1979; Fillion & Pickerill, 1990). Hakes (1976) retained Lockeia because Article 12 of the ICZN did not require figures for taxa established before 1931 if the original author provided a description or definition. Hakes (1977) later regarded Lockeia as nomen oblitum citing the 50-year rule (ICZN, Article 79) of nonuse of a taxon. Maples and West (1989) noted that Lockeia was used once to validly erect an ichnospecies, Lockeia anticostiana, by Twenhofel (1927) during the supposed 50-year hiatus and, thus, invalidated the argument of Hakes (1977).

At least 13 ichnospecies of Lockeia have been proposed: L. amygdaloides (Seilacher, 1953a); L. anticostiana Twenhofel, 1927; L. avalonensis Fillion & Pickerill, 1990; L. cordata Rindsberg, 1994; L. cunctator Schlirf & Uchman in Schlirf, Uchman, & Kümmel, 2001; L. czarnockii (Karaszewski, 1975); L. elongata Yang, 1984; L. gigantus Kim & Kim, 2008; L. hunanensis Zhang & Wang, 1996; L. ornata (Bandel, 1967); L. serialis Seilacher & Seilacher, 1994; L. siliquaria James, 1879; and L. triangulichnus Kim, 1994. Schlirf, Uchman, and Kümmel (2001) and Mángano and others (2002) recently reviewed and compared most of the ichnospecies of Lockeia except for L. gigantus. Lockeia anticostiana was considered as Planolites (Hakes, 1977). Lockeia cunctator is considered a repichnia version of Lockeia similar to and partly as a replacement for L. serialis—considered nomen nudum due to lack of holotype designation and not figured by Seilacher and Seilacher (1994)—but L. cunctator is more similar to Treptichnus bifurcus from where it was transferred by Schlirf, Uchman, and Kümmel (2001)—due to its feather-stitch morphology. Lockeia gigantus was proposed for extremely large, almond-shaped ichnofossils (up to 70 mm long and 30 mm wide) from the Lower Cretaceous lacustrine deposits of Korea (Kim & Kim, 2008).

Lockeia is considered a dwelling or resting trace of a bivalve or bivalve-like organism (Seilacher & Seilacher, 1994; Mángano & others, 2002). Lockeia has been reported from shallow marine (e.g., lower delta fronts, and subtidal and intertidal flats), deep marine, and continental lacustrine and fluvial deposits (e.g., Seilacher, 1953a; Hakes, 1976; Bromley & Asgaard, 1979; Crimes & others, 1981; Fillion & Pickerill, 1990; Głuszek, 1995; Hasiotis, 2002, 2004, 2007, 2008; Mángano & others, 2002; Hasiotis & others, 2012). Precambrian Lockeia specimens have been reported (e.g., Narbonne & Aitken, 1990; Jenkins, 1995; McMenamin, 1996), however, Mángano and others (2002) and Jensen, Droser, and Gehling (2006) noted that the traces did not possess the diagnostic characteristics of Lockeia and were likely dubiofossils or body fossils, respectively. The Narbonne and Aitken (1990) specimens show the oval to almond shape characteristic of Lockeia, and, thus, the assignment is justified. Some of the specimens illustrated by McMenamin (1996) may actually be a form of Treptichnus, as they appear to have a feather-stitch morphology characteristic to Treptichnus. Lockeia ranges from the Ediacaran to recent (e.g., Crimes, 1987, 1992; Narbonne & Aitken, 1990; Hasiotis, 2002; Mángano & others, 2002; Jensen, Droser, & Gehling, 2006).

Material.—KUMIP 314228; one specimen, Miner's Hollow; IBGS LG-M-003: one specimen; IBGS PJ-M-019; one specimen, Miner's Hollow.

Diagnosis.—Amygdaloidal (almond-shaped) convex hyporeliefs, with one or both ends usually tapered to a point, some may be round.

Description.—Amygdaloid-shaped (almond-shaped) mound in convex hyporelief; 4.1–6.3 mm long and 2.6–4.4 mm wide.

Occurrence.—Two lithologies; (1) Light to dark gray, laminated silty shale with continuous laminations indicating an ii2; and (2) medium to dark gray calcareous, micaceous silty to sandy shale. Bedding planes are highly disrupted with numerous traces indicating BPBI 4–5.

Associated ichnotaxa.—Aulichnites isp., Cruziana problematica, Dimorphichnus isp., Monomorphichnus lineatus, M. cf. multilineatus, Phycosiphon incertum, Planolites beverleyensis, P. montanus, Protovirgularia cf. pennatus, Rusophycus carbonarius, Rusophycus cf. cerecedensis, Sagittichnus lincki, and Treptichnus vagans.

Discussion.—The Lockeia siliquaria specimen on IBGS PJ-M-019 occurs at the termination of a bilobate concave hyporelief burrow assigned to Aulichnites. The close linear association of the two ichnotaxa suggests they were produced by the same tracemaker. The depth of the L. siliquaria increases toward the opposite side of the intersection of the two ichnotaxa, suggesting the tracemaker produced the Aulichnites and then the Lockeia (see Fig. 6.5). On IBGS LG-M-003, a L. siliquaria specimen is found alongside specimens of Sagittichnus lincki, which are similarly shaped, small ovoid-shaped convex mounds (for discussion see Sagittichnus, p. 36). The two morphologies can be distinguished by size, as L. siliquaria is larger than the Sagittichnus lincki specimens.

Type ichnospecies.—Monomorphichnus bilinearis Crimes, 1970b.

Diagnosis.—Series of straight to sigmoidal, parallel or intersecting, laterally repeating striations in isolated or grouped sets; typically preserved in convex hyporelief (Crimes, 1970b; Fillion & Pickerill, 1990; Keighley & Pickerill, 1998).

Discussion.—Crimes (1970b) established Monomorphichnus for surficial striations produced by bottom-current-propelled trilobites raking the sediment surface with their endopodite claws. He noted that these striations were similar to Dimorphichnus but lacked the characteristic blunt impressions (Crimes, 1970b; Fillion & Pickerill, 1990; Jensen, 1997). Monomorphichnus maybe a junior synonym of Ctenichnites Matthew, 1891, Eoichnites Matthew, 1891, Medusichnites Matthew, 1891, or Taonichnites Matthew in Selwyn, 1890; however, their ichnotaxonomic status is unclear as some authors have considered them dubiofossils or pseudofossils, whereas others considered them valid ichnotaxa (see Fillion & Pickerill, 1990, for full discussion).

Since Monomorphichnus was established at least 15 ichnospecies have been proposed and differentiated by the number of striations present: M. bilinearis Crimes, 1970b; M. biserialis Mikuláš, 1995; M. cretacea Badve & Ghare, 1980; M. devonicus Yang & Hu in Yang, Hu, & Sun, 1987; M. gaopoensis Yang, Yin, & He, 1982; M. gregarius, Pandey & others, 2014; M. henanensis Yang & Wang, 1991; M. intersectus Fillion & Pickerill, 1990; M. lineatus Crime & others, 1977; M. monolinearis Shah & Sudan, 1983; M. multilineatus Alpert, 1976a; M. pectenensis Legg, 1985; M. podolicus Uchman & others, 2004; M. semilineatus Mikuláš, 1995; and M. sinus Gibb, Chatterton, & Pemberton, 2009. Monomorphichnus cretacea and M. gaopoensis are considered inorganic tool marks or a combination of organic and inorganic structures (e.g., Fillion & Pickerill, 1990; Uchman & others, 2004). Fillion and Pickerill (1990) found M. monolinearis to be a junior synonym of M. lineatus. Monomorphichnus podolicus was synonymized with Cruziana omanica Seilacher, 1970, due to its tendency to occur bilobate (Gibb, Chatterton, & Pemberton, 2009). Monomorphichnus gregarius was introduced by Pandey and others (2014) for highly overlapping sets of 4 striations; however, the holotype has sets of 4–6 striations, most of which occur in sets of 6, with central striations being more prominent, and crosscut other sets, which suggests affinities to both M. multilineatus and M. intersectus. We, therefore, regard M. gregarius and M. intersectus as subjective junior synonyms of M. multilineatus.

Monomorphichnus is considered a locomotion or grazing trace (Crimes, 1970b; Crimes & others, 1977), and often has been attributed to trilobites (e.g., Crimes, 1970b; Alpert, 1976a), but other arthropods (e.g., eurypterids and xiphosurids) have also been proposed as possible tracemakers (Romano & Meléndez, 1985; Jensen, 1997). Osgood (1970) suggested the grazing interpretation was an inefficient feeding strategy and that Monomorphichnus was likely produced by an arthropod trying to stabilize itself while caught in turbulent bottom-water currents. A recent neoichnological study by Jones (2016) has shown several Monomorphichnus-like traces produced by bats via ground-based locomotive and searching behaviors. Monomorphichnus has been reported from shallow- and deep-marine, and continental deposits (e.g., Crimes, 1970b; Crimes & others, 1977; Keighley & Pickerill, 1998). The earliest occurrence of Monomorphichnus has been thought to be in units previously referred to as Vendian—now known as the Ediacaran—by Crimes (1987, 1992). Reports of Monomorphichnus from latest Neoproterozoic strata by Jenkins (1995) and Waggoner and Hagadorn (2002) were reinterpreted by Jenson, Droser, and Gehling (2006) as Radulichnus and tool marks or a trace fossil(?), respectively. However, the redefinition of the Ediacaran (Neoproterozoic)-Cambrian (Paleozoic) boundary based on the occurrence of Treptichnus pedum may define the range of Monomorphichnus as Cambrian to recent (e.g., Jensen, 1997; MacNaughton & Narbonne, 1999; Jenson, Droser, & Gehling, 2006; Landing & others, 2007; Hasiotis, 2012).

Material.—IBGS PJ-M-031; five specimens, Miners Hollow.

Diagnosis.—Pairs of parallel, straight to slightly sigmoidal striations with one striation more prominent than the other, and sometimes repeated laterally (Crimes 1970b; Fillion & Pickerill, 1990).

Description.—Paired sigmoidal striations in convex hyporelief. Striations 12.1–45.2 mm long, 0.6–1.7 mm wide, and spaced 1.0–1.3 mm apart.

Occurrence.—Gray (weathered to brown), micaceous silty shale.

Associated ichnotaxa.—Treptichnus vagans.

Discussion.—Monomorphichnus bilinearis are only present on IBGS PJ-M-031 alongside Treptichnus vagans. The striations were assigned to this ichnogenus due to their sigmoidal shape and tendency to occur in pairs. Some M. bilinearis specimens are cross cut by Treptichnus vagans specimens (Fig. 14.2), thus, indicating the striations were produced first, followed by the construction of the Treptichnus vagans.

Material.—KUMIP 314228; one specimen, Miners Hollow; IBGS LG-M-008 and LG-M-009 (part and counterpart): one specimen, Spence Shale; IBGS PJ-M-012: one specimen, Miners Hollow.

Diagnosis.—Individual, straight to slightly sigmoidal striations that can be repeated laterally (Crimes & others, 1977; Fillion & Pickerill, 1990).

Description.—Sigmoidal to slightly curved striations, some may be bifid, in convex hyporelief and concave epirelief. Striations 5.4– 36.1 mm long, 0.5–2.1 mm wide. One row of repeated striations is 50.6 mm long, 9.7 mm wide, and spaced 1.5–1.9 mm apart. Striations may have blunt ends and sharply taper on the other.

Occurrence.—Two lithologies: (1) greenish gray (weathered to tan or brown), micaceous silty shale; and (2) gray, silty shale with laminations of light and dark gray, silty to sandy, siliciclastic to carbonate shale.

Associated ichnotaxa.—Cruziana problematica, Lockeia siliquaria, Monomorphichnus cf. multilineatus, Planolites beverleyensis, P. montanus, Protovirgularia dichotoma, Rusophycus carbonarius, Rusophycus cf. cerecedensis, Treptichnus bifurcus, and T. vagans.

Discussion.—The specimen on IBGS PJ-M-012 is differentiated from Cruziana billingsi Fillion & Pickerill, 1990, by the arrangement of striations in a single track row—whereas C. billingsi is bilobate—and is almost identical to the holotype illustrated by Crimes and others (1977, p. 107, pl. 3b) (Fig. 14.3). Specimens on IBGS LG-M-008 and LG-M-009 occur with no other traces (Fig. 14.4).

Material.—KUMIP 314228: one specimen, Miner's Hollow.

Diagnosis.—Parallel, straight to sigmoidal striations grouped in sets of 5 to 6, with deeper and thicker striations in center of group (Alpert, 1976a).

Description.—Horizontal, sigmoidal striations (convex hyporelief) grouped in sets of 2–4, spaced 1.6–1.8 mm apart with one striation more prominent than the others. Striations 3.0–14.2 mm long, 0.3–0.7 mm wide, and spaced 0.5–1.1 mm apart.

Occurrence.—Greenish gray (weathered to tan or brown), micaceous silty shale.

Associated ichnotaxa.—Cruziana problematica, Lockeia siliquaria, Monomorphichnus lineatus, Planolites beverleyensis, P. montanus, Rusophycus carbonarius, R. cf. cerecedensis, and Treptichnus bifurcus.

Discussion.—The specimen has striations grouped in pairs assignable to M. bilinearis, but others grouped in triplets and quadruplets, which are assignable to M. multilineatus. A specimen illustrated by Fillion and Pickerill (1990, pl. 10, fig. 3) has several bundles of 2–3 striations mixed with the typical 4–6 striation bundles. The similarity between the Spence Shale specimen and the Fillion and Pickerill (1990) specimen justifies assignment to M. multilineatus. Another Monomorphichnus ichnospecies that the Spence Shale specimen resembles is M. semilineatus Mikuláš, 1995, which is characterized as curved to straight sigmoidal striations in groups of 2–10 (Mikuláš, 1995, pl. 1 & 3, fig. 1C). Monomorphichnus semilineatus, however, appears to be morphologically variable with bundle sets that are indistinguishable from other Monomorphichnus ichnospecies. We, therefore, consider M. semilineatus to be an amalgam of several Monomorphichnus ichnospecies and no valid use to ichnotaxonomy. Monomorphichnus multilineatus also resembles the coarse striations of Rusophycus dispar Linnarsson, 1869, like those figured by Jensen (1990, fig. 1) (Fig. 14.5); however, the specimen lacks the bidirectionality and bilobate shape typical of R. dispar.

Type ichnospecies.—Nereites cambrensis MacLeay 1839 in Murchison (1839, p. 700).

Diagnosis.—Curved, winding to regularly meandering, unbranched, horizontal trails, with a medial backfilled tunnel flanked by an even to lobate zone of reworked sediment (Uchman, 1995; Mángano & others, 2000, 2002).

Discussion.—A long-lasting debate in ichnotaxonomy has been raging regarding status of the ichnotaxa Nereites MacLeay, 1839 in Murchison, 1839; Neonereites Seilacher, 1960; and Scalarituba Weller, 1899. Numerous authors have suggested that Nereites is the senior synonym of Neonereites and Scalarituba, arguing that both are preservational variants of Nereites (e.g., Chamberlain, 1971; Chamberlain & Clark, 1973; D'Alessandro & Bromley, 1987; Devera, 1989; Rindsberg, 1994; Uchman 1995; Mángano & others, 2000, 2002). Some authors, however, retain or advocate for the retention of Neonereites as a separate ichnotaxon (e.g., Benton, 1982; Fillion & Pickerill, 1990; Pickerill, 1991).

Though long suggested, Uchman (1995) was one of the few to formally place Neonereites and Scalarituba within Nereites. He also suggested that the three Neonereites ichnospecies (N. biserialis Seilacher, 1960; N. multiserialis Pickerill & Harland, 1988; and N. uniserialis Seliacher, 1960) should be used informally as subichnospecies to describe associated preservational variation. Helminthoida Schafhäutl, 1851, was also synonymized under Nereites because Uchman (1995) noted Nereites-like marginal lobes in the type specimen. Seilacher (1962) suggested that Helminthoida and Neonereites were related with Neonereites being a preservational variant of Helminthoida in sand-rich environments. We, however, suggest retaining Helminthoida due to its high-sinuosity, tightly meandering, and repetitive pattern in morphology that is distinctive and diagnostic of this ichnotaxon, which is morphologically related to Helminthopsis Heer, 1877.

Nereites is interpreted as a deposit-feeding or grazing trace (e.g., Uchman, 1995; Mángano & others, 2000, 2002). Commonly proposed tracemakers include annelid, enteropneust, and polychaete worms (e.g., Seilacher, 1960; Rindsberg, 1994; Uchman 1995; Mángano & others, 2000, 2002); however, gastropods, arthropods, and echinoderms (e.g., holothurians) have also been proposed (e.g., Rindsberg, 1994). Although the namesake of the deep marine Nereites Ichnofacies, Nereites has been reported from shallow-marine (e.g., lagoon, shoreface, tidal flats) and deep-marine settings (e.g., flysch) (e.g., Hakes, 1976; McCann & Pickerill, 1988; Uchman, 1995, 1998; Mángano & others, 2000). Nereites is common in both shallow- and deep-marine Paleozoic deposits but became almost exclusively deep marine in Mesozoic and Cenozoic deposits (e.g., Uchman, 1995; Mángano & others, 2000). Mángano and others (2002) argued that the lacustrine Nereites specimens figured by Hu, Wang, and Goldring (1998) did not fit the diagnostic criteria for Nereites and belong in Vagorichnus Buatois and others, 1995. We, however, consider Vagorichnus to be a junior synonym of Walpia White, 1929, based on morphologic similarities. We suggest that the specimens figured by Hu, Wang, and Goldring (1998) have morphologic features assignable to Walpia, which are typical of burrows produced by modern mud-loving beetles and some spiders just above the sediment-water interface (Hasiotis, 2002, 2004, 2008). Nereites has been reported from the Vendian (i.e., Edicaran) (e.g., Crimes & Germs, 1982; Jenkins, 1995); however, Jensen, Droser, and Gehling (2006) considered those specimens to be a form of Archaeonassa. Yet the photograph of the Nereites specimen in Crimes and Germs (1982) does show a central furrow flanked by ridges that are subtly lobate that grade into strongly hemispherical lobes typical of several Nereites ichnospecies; thus, we consider this specimen to be Nereites. The stratigraphic position of this specimen, however, is in the Vingerbreek Member of the Nudaus Formation of the lower part of the Schwarzrand Subgroup, which is Ediacaran in age, based on the co-occurrence of body fossils (e.g., Cohen & others, 2009). Nereites, therefore, ranges from the Ediacaran to recent (e.g., Crimes & Germs, 1982; Crimes, 1992; Mángano & others, 2000; Uchman, 1995).

Material.—IBGS PJ-M-033: one specimen (part and counterpart), Miner's Hollow.

Diagnosis.—Small, straight to meandering, concave furrow (epirelief) or convex burrow (hyporelief) flanked by small, semicircular lobes along furrow margin (McCann & Pickerill, 1988).

Description.—Straight, concave furrow flanked by small, semicircular lobes 24.1 mm long, 2.5–4.5 mm wide. Furrow 1.1–3.0 mm wide, and lobes 1.4–1.8 mm wide (from furrow margin). Furrow has a serial, spherical-chambered expression, chamber diameter 1.4–3.0 mm.

Occurrence.—Gray (weathered to brown), siliciclastic silty to sandy shale.

Associated ichnotaxa.—Archaeonassa fossulata, Gyrophyllites kwassizensis, and Planolites montanus.

Discussion.—The assignment to Nereites cf. macleayi was based primarily on the presence of small, semicircular lobes present along the furrow margin (Fig. 14.6). The furrow also has a serialchamberlike appearance similar to Neonereites uniserialis; however, since Neonereites was synonymized under Nereites, assignment to Neonereites is untenable. Assignment to Nereites missouriensis may be justified by the presence of the serial chambers; yet, no meniscate backfill typical of N. missouriensis is observed in the specimen.

Type ichnospecies.—Phycodes circinatus Richter, 1853.

Diagnosis.—Horizontal to subhorizontal, cylindrical to U-shaped burrows with dichotomously branched tunnels forming bundles (Fillion & Pickerill, 1990; Knaust, 2007).

Discussion.—Since Richter (1850) originally designated Phycodes for bundled structures regarded as fucoids, Phycodes has undergone several revisions to its present-day status as an ichnofossil (see Fillion & Pickerill, 1990; Han & Pickerill, 1994b; Jensen, 1997). Phycodes has been interpreted as a deposit-feeding trace of annelid worms (Fillion & Pickerill, 1990). Phycodes has been considered to be a good indicator for shallow-marine settings and indicative of the Cruziana Ichnofacies, but Phycodes has been reported from brackish and deep-water deposits as well (e.g., Hakes, 1985; Fillion & Pickerill, 1990; Han & Pickerill, 1994a; Jackson, Hasiotis, & Flaig, 2016). Phycodes ranges from the early Cambrian to the Miocene (Crimes, 1987, 1992; Han & Pickerill, 1994a).

Material.—IBGS PJ-M-005: one specimen, Miner's Hollow float.

Diagnosis.—Thin, short, rounded, horizontal palmate or digitate burrows that originate from the same point (Pollard, 1981).

Description.—Small trifid-branched system of short burrows in convex epirelief and partial endorelief. Burrows range from 4.6–16.9 mm long and 2.0–2.5 mm wide. Burrow fill of two branches are exposed with burrow walls 0.3–0.8 mm thick and is similar to the host lithology.

Occurrence.—Tan to light brown, siliciclastic silty shale.

Associated ichnotaxa.—Archaeonassa jamisoni and Taenidium cf. satanassi.

Discussion.—The specimen consists of a triplet of burrows exhibiting primary successive branching (sensu D'Alessandro & Bromley, 1987; Keighley & Pickerill, 1995). (Fig. 15.1). The specimen is assigned to P. curvipalmatum and not P. palmatus because the burrows are both short and narrow, whereas P. palmatus Hall, 1852 has long and wide burrows. Two branches are preserved mostly as endoreliefs with the burrow walls as the only significant structures remaining, whereas one branch is in convex epirelief.

Type ichnospecies.—Phycosiphon incertum Fischer-Ooster, 1858, by original monotypy.

Diagnosis.—Small, oblique or parallel to bedding, spreiten-filled burrow systems comprised of protrusive U-shaped lobes with dark, finer grained cores and light, coarser grained mantles; lobes may be nearly vertical to bedding; spreiten may not be visible (Wetzel & Bromley, 1994; Głuszek, 1998; Uchman, 1998).

Discussion.—Like most ichnofossils, Phycosiphon was originally interpreted as fossilized algae. More recently, however, it was interpreted as a complex burrow system of a deposit feeder, typically in dysoxic sediments (e.g., Ekdale & Mason, 1988; Uchman, 1998; Naruse & Nifuku, 2008). Wetzel and Bromley (1994) noted two general lobe arrangements occur in Phycosiphon, influenced by the host lithology; (1) lobes are parallel or subparallel to bedding in laminated sands and silts (exaggerated by compaction); and (2) lobes are randomly to vertically oriented in muddy and homogenous sediments. Wetzel and Bromley (1994) also compared Phycosiphon to Anconichnus Kern, 1978, because both are mantled, spreiten-filled, U-shaped burrow systems, and they decided that Anconichnus was a junior synonym of Phycosiphon.

Phycosiphon was monotypic with P. incertum as its sole ichnospecies until Uchman (1998) synonymized Muensteria hamata Fischer-Ooster, 1858, under Phycosiphon as P. hamata, and later joined by Muensteria geniculata Sternberg, 1833 by Uchman (1999) as P. geniculatum. Phycosiphon hamata differs from P. incertum with its more regularly shaped lobes, larger size, and J- to U-shaped lobes. Uchman (1998) also warned that P. hamata should not confused with Zoophycos, which occur in multiple levels, whereas P. hamata occurs on only one. Phycosiphon geniculatum differs from P. hamata and P. incertum by having radially arranged lobes with one margin well defined, usually concave, and the other margin is convex and highly lob ate and indistinct. Naruse and Nifuku (2008) demonstrated that the elliptical burrow cross-sections of Phycosiphon could be used to determine the paleoslope inclination of a deposit.

Phycosiphon is interpreted a trace of a deposit-feeding, wormlike organism (Wetzel & Bromley, 1994). Phycosiphon occurs in continental-shelf slopes, submarine fans, turbidites, and flysch deposits (e.g., Uchman, 1998; Naruse & Nifuku, 2008; Rajchel & Uchman, 2012). Recent studies have found that Phycosiphon tracemakers are early colonizers of the upper portions of turbidite deposits when bottom waters are fully oxygenated (e.g., Wetzel & Uchman, 2001; Naruse & Nifuku, 2008). Phycosiphon ranges from the early Cambrian to recent (Fu, 1991; Naruse & Nifuku, 2008).

Material.—IBGS LG-M-007; seven specimens; IBGS PJ-M-019; five specimen, Miner's Hollow.

Diagnosis.—Small, oblique or parallel to bedding, spreiten-filled burrow systems comprised of protrusive U-shaped lobes with dark, fine-grained cores and light, coarse-grained mantles (Wetzel & Bromley, 1994; Głuszek, 1998; Uchman, 1998).

Description.—Mantled, endorelief burrows with elliptical to U-shaped cross sections. Light gray mantles 0.1–0.4 mm thick, average thickness 0.2 mm. Dark gray cores 0.3–1.0 mm thick, 1.1–7.8 mm wide.

Occurrence.—Two lithologies; (1) green, fine-grained siliciclastic sandstone, weathered to tan; and (2) laminated mudstone of alternating light-gray and dark-gray laminations. Laminations on IBGS PJ-M-019 are continuous with very little bioturbation occurring to disrupt them (ii2), but on IBGS LG-M-007, the laminations are moderately disrupted (ii3–4).

Associated ichnotaxa.—Aulichnites isp., Dimorphichnus isp., Lockeia siliquaria, Protovirgularia cf. pennatus, and Treptichnus vagans.

Discussion.—Phycosiphon incertum present on IBGS LG-M-007 in cross section show a light gray to white mantle and some spreite within the burrow fill (Fig. 16.1–16.4). Some spreiten are visible in longitudinal cross section (Fig. 16.1–16.2), but are most visible in specimens with transverse cross sections (Fig. 16.3–16.4). The sediment of IBGS LG-M-007 is mostly pale green to white finegrained sandstone, while the burrow fill is composed of fine- to very fine-grained, gray to black sandstone. Sample IBGS PJ-M-019 has several specimens of P. incertum on the cut side of the samples (Fig. 16.5–16.6). The mantle surrounding some of the IBGS PJ-M-019 burrows is not very noticeable, possibly due to their small size and compaction.

Type ichnospecies.—Planolites beverleyensis Billings, 1862 (=Planolites vulgaris Nicholson & Hinde, 1875, junior synonym, Pemberton & Frey, 1982).

Diagnosis.—Unlined to rarely lined, rarely branching, straight to tortuous burrows with smooth to irregular walls and circular to elliptical cross sections; infill unstructured and may differ from host-rock lithology (Pemberton & Frey, 1982; Fillion & Pickerill, 1990; Uchman, 1998).

Discussion.—Ichnotaxonomy still has numerous problems with differentiating between certain ichnotaxa, including Palaeophycus Hall, 1847, and Planolites (e.g., Osgood, 1970; Häntzschel, 1975; Pemberton & Frey, 1982). In an attempt to resolve those problems, Pemberton and Frey (1982) reexamined both ichnogenera and established standard diagnostic criteria for differentiating them: (1) burrows lack wall linings; and (2) burrows have different color and texture from host-rock lithology that indicate active infilling. Another criterion suggested to help identify Planolites is the lack of systematic branching or enlargements around branch sites (Fillion & Pickerill, 1990). Keighley and Pickerill (1995) argued against the use of active vs. passive infill and suggested that the presence or lack of a wall lining should be the primary diagnostic criterion for Palaeophycus and Planolites, respectively. Keighley and Pickerill (1997) also recommended synonymizing P. montanus under P. beverleyensis and argued that the size criterion used to separate the two ichnospecies was invalid; however, most authors have ignored the Keighley and Pickerill (1997) recommendation and continue to use both P. beverleyensis and P. montanus (e.g., Pickerill & Fyffe, 1999; Uchman, 1999; Hofmann & others, 2012).

Planolites is typically interpreted as the trace of a deposit-feeding marine or freshwater worm (e.g., Häntzschel, 1975; Fillion & Pickerill, 1990); however, soil arthropods and worms have been suggested as possible tracemakers in continental deposits (e.g., Ekdale, Bromley, & Loope, 2007; Hasiotis, 2004, 2008; Smith & others, 2008a, 2009). Planolites is a facies-crossing ichnogenus and has been report from shallow- to deep-marine and continental deposits (e.g., alluvial, fluvial, lacustrine, and eolian) (e.g., Chamberlain, 1971, 1975, 1977; Fillion & Pickerill, 1990; Keighley & Pickerill, 1997; Kim & others, 2005; Ekdale, Bromley, & Loope, 2007; Bohacs, Hasiotis, & Demko, 2007; Hembree & Hasiotis, 2007; Hofmann & others, 2012). Planolites ranges from the Ediacaran to recent (Häntzschel, 1975; Crimes, 1987, 1992; Uchman, 1998).

Material.—KUMIP 314229: two specimens, Miner's Hollow; IBGS PJ-M-001: four specimens, Miner's Hollow.

Diagnosis.—Horizontal, straight to curved, subcylindrical burrows with pronounced annulations (Pemberton & Frey, 1982; Fillion & Pickerill, 1990).

Description.—Simple, straight to curved burrows in concave epirelief or convex hyporelief with transverse constrictions forming numerous short chambers (1.1–2.0 mm long). Burrows 17.1–125.2 mm long, 0.8–1.5 mm wide. On IBGS PJ-M-001, a reddish brown halo is present along some burrows and extends 0.9–2.3 mm from burrow margin.

Occurrence.—Gray to dark gray, massive siliciclastic shale.

Associated ichnotaxa.—Bergaueria hemispherica, Cruziana barbata, and Rusophycus carbonarius.

Discussion.—The burrows were formed by peristaltic movement of a wormlike tracemaker that resulted in the serial-chambered expression (Pemberton & Frey, 1982). Most P. annularius specimens have a reddish brown oxidation halo surrounding the burrow, indicating poorly oxygenated sediments near the time of construction (e.g., Ekdale, Bromley, & Pemberton, 1984; Bromley, 1996; Forster, 1996) (see Fig. 15.2). One burrow has the reddish brown halo for about half its length and the entire width extending to ∼3 mm from the burrow center, but also loses the annulated chambers where the halo is present. The change from an annulated burrow with or without a halo to a fully haloed, smooth burrow could be a transition from P. annularius to P. montanus representing a change in oxygen and nutrient availability in the sediment (e.g., Pemberton & Frey, 1982; Forster, 1996).

Material.—KUMIP 314223: one specimen, Antimony Canyon; KUMIP 314228: one specimen, Miner's Hollow;s IBGS LG-M-001: one specimen; IBGS LG-M-005: four specimens.

Diagnosis.—Large, smooth, straight to gently curved or undulated cylindrical burrows with unstructured backfill and lacking wall linings (Pemberton & Frey, 1982; Fillion & Pickerill, 1990; Keighley & Pickerill, 1995).

Description.—Convex hyporelief or concave epirelief, straight to gently curved cylindrical burrow; however, some are contorted and overlap. Burrows 10.3–50.4 mm long and 3.0–6.3 mm wide. No wall lining is visible.

Occurrence.—Light to dark gray (weathered to light brown or tan), siliciclastic silty shale.

Associated ichnotaxa.—Cruziana problematica, Gyrophyllites kwassizensis, Lockeia siliquaria, Monomorphichnus lineatus, M. cf. multilineatus, Planolites montanus, Rusophycus carbonarius, and Treptichnus bifurcus.

Discussion.—Planolites beverleyensis is typically differentiated from others ichnospecies of Planolites by its larger burrow diameter (> 5 mm), its generally straighter course, and a lack of annulations (Billings, 1862; Pemberton & Frey, 1982). Though most burrow diameters are < 5 mm, specimens assigned to P. beverleyensis are significantly larger and straighter than any specimen assigned to P. montanus. One specimen of P. beverleyensis appears to record a predation-prey interaction with a Rusophycus cf. cerecedensis (Fig. 15.5) (for discussion see Rusophycus cf. cerecedensis p. 34).

Material.—KUMIP 204523 A and B: four specimens, Miner's Hollow; KUMIP 314122: one specimen, Antimony Canyon; KUMIP 314222 B: 13 specimens, Miner's Hollow; KUMIP 314228: 11 specimens, Miner's Hollow; IBGS LG-M-010: four specimens; IBGS LG-M-011: four specimens; IBGS LG-M-012: two specimens; IBGS LG-M-013: three specimens; IBGS PJ-M-001: one specimen, Miner's Hollow; IBGS PJ-M-004: two specimens, Miner's Hollow; IBGS PJ-M-005: five specimens, Miner's Hollow float; IBGS PJ-M-007: six specimens, Miner's Hollow; IBGS PJ-M-010: three specimens, Miner's Hollow IBGS PJ-M-011: three specimens, Spence Tongue of the Lead Bell Shale, Oneida Narrows, Idaho; IBGS PJ-M-013: one specimen, Miner's Hollow; IBGS PJ-M-014: one specimen, Miner's Hollow; IBGS PJ-M-016: two specimens, Miner's Hollow; IBGS PJ-M-020: one specimen, Miner's Hollow; IBGS PJ-M-023: two specimens, Miner's Hollow; IBGS PJ-M-024: one specimen, Miner's Hollow; IBGS PJ-M-027: two specimens, Miner's Hollow; IBGS PJ-M-030: one specimen, Miner's Hollow; IBGS PJ-M-033: two specimens.

Diagnosis.—Relatively small, curved to tortuous, cylindrical to subcylindrical burrows lacking wall linings (Pemberton & Frey, 1982; Fillion & Pickerill, 1990; Keighley & Pickerill, 1995).

Description.—Small, smooth burrows that are generally straight but sometimes sharply bent, curved, or contorted. Burrows 12.5–73.2 mm long and 0.7–5.4 mm wide.

Occurrence.—Laminated light to dark gray or dark gray (weathered to tan or brown) to pale greenish gray, calcareous or siliciclastic silty shale.

Associated ichnotaxa.—Archaeonassa fossulata, Cruziana problematica, Halopoa aff. imbricata, Lockeia siliquaria, Monomorphichnus lineatus, M. cf. multilineatus, Nereites cf. macleayi, Planolites beverleyensis, Rusophycus carbonarius, R. cf. cerecedensis, Treptichnus bifurcus, and Treptichnus vagans.

Discussion.—Planolites montanus is one of the most common ichnofossils from the Spence Shale. Burrows assigned to this ichnotaxon exhibit simple, smooth margins, fill different from the host rock, a lack of distinct walls, and diameters typically < 5 mm. Some specimens of P. montanus occur in a Treptichnus-like morphology of short burrows that alternate very loosely around a central axis.

Type ichnospecies.—Protovirgularia dichotoma M‘Coy, 1850.

Diagnosis.—Unbranched, straight to slightly curved trails with medial ridge or furrow and paired, wedge-shaped, lateral projections from ridge or furrow (Han & Pickerill, 1994b).

Discussion.—Protovirgularia was originally interpreted by M‘Coy (1850) as a body fossil of octocoral and graptolites. Han and Pickerill (1994b), Seilacher and Seilacher (1994), and Uchman (1998) have reviewed Protovirgularia. Han and Pickerill (1994b) reassessed the four previously established ichnospecies of Protovirgularia, and found that: (1) P. dichotoma M‘Coy, 1850 was the only valid ichnospecies; (2) P. mongraensis Chiplonkar & Badve, 1970, and P. nereitarum (Richter, 1871) as junior synonyms of P. dichotoma; and (3) P. harknessi Lapworth, 1870, was nomen nudum and not valid because it was not described or figured when originally proposed. Seilacher and Seilacher (1994) demonstrated via neoichnological experiments that protobranch bivalves and scaphopods were the primary producers of Protovirgularia and also synonymized Imbrichnus Hallam, 1970, Pennatulites De Stefani, 1885, Uchirites Macsotay, 1967, and Walcottia Miller & Dyer, 1878, under Protovirgularia. Uchman (1998) also expanded Protovirgularia to include some ichnospecies of Gyrochorte, Nereites, Rhabdoglyphus Vassoevich, 1951, and Tuberculichnus Książkiewicz, 1977, as junior synonyms.

Protovirgularia is interpreted as a push-pull locomotion and feeding trace of bivalves and scaphopods (e.g., Han & Pickerill, 1994b; Seilacher & Seilacher, 1994). Protovirgularia has been reported from shallow marine, deep marine (e.g., turbidites), and brackish water deposits (e.g., deltas, estuaries, and tidal flats) (e.g., Han & Pickerill, 1994b; Seilacher & Seilacher, 1994; Carmona & others, 2010; Jackson, Hasiotis, & Flaig, 2016). Protovirgularia is sometimes suggestive of salinity, sedimentation rate, and turbidity fluctuations as well as possible oxygen depletion (Carmona & others, 2010). Protovirgularia ranges from the early Cambrian to recent (Seilacher & Seilacher, 1994; Orłowski & Zylińska, 2002).

Material.—KUMIP 314233: one specimen.

Diagnosis.—Straight, bilobate trails with medial furrow and paired, convex, chevronlike, wedge-shaped projections oblique from furrow.

Description.—Specimen 29.1 mm long and 4.1 mm wide. The chevronlike, wedge-shaped projections range 2.7–4.2 mm long and 1.5–2.3 mm wide. Projection sets have a 45–55° V-shaped angle. Faint striations are present on projections.

Occurrence.—Dark gray (weathered to tan), calcareous silty shale with very thin siliciclastic mud with possible swaley crossstratification.

Associated ichnotaxa.—Monomorphichnus lineatus and Treptichnus vagans.

Discussion.—Though similar to Didymaulichnus Young, 1972, due to its bilobate shape and seemingly smooth projections, the P. dichotoma specimen has a chevronlike morphology most similar to Protovirgularia morphologic variant 5 of Carmona and others (2010, fig. 3.8 & 4) and experimental undertraces analogous to P. dichotoma illustrated by Seilacher and Seilacher (1994, pl. 1, fig. a) (Fig. 17.1). Protovirgularia specimens illustrated by Fernández, Pazos, and Aguirre-Urreta (2010) show intergradation between P. dichotoma and P. rugosa, and the lateral projections of the Spence Shale P. dichotoma are more oblique and wedgelike, and thus are more similar to P. dichotoma. However, the morphologic characteristic that separates P. dichotoma and P. rugosa is the presence of a Lockeia-like object at the termination of P. rugosa (sensu Seilacher & Seilacher, 1994; Uchman, 1998), which the Spence Shale P. dichotoma specimen lacks.

Material.—KUMIP 204521 A and B: one specimen; IBGS PJ-M-019: Miner's Hollow.

Diagnosis.—Straight to winding, bilobate, chevronlike ribbon trace with medial ridge.

Description.—Chevronlike ribbon trace in convex hyporelief. Specimens 23.5–254 mm long and 2.9–11.2 mm wide. The lobes consist of thin, commalike to arcuate striations or may be plumoselike.

Occurrence.—Two lithologies: (1) laminated light to dark gray silty shale; and (2) dark gray (weathered to tan) to pale greenish gray, calcareous silty to sandy shale.

Associated ichnotaxa.—Aulichnites isp., Dimorphichnus isp., Diplichnites cf. binatus, Diplichnites cf. govenderi, Lockeia siliquaria, Phycosiphon incertum, and Treptichnus vagans.

Discussion.—Protovirgularia cf. pennatus specimen on IBGS PJ-M-019 has characteristics similar to two ichnospecies of Protovirgularia illustrated by Nara and Ikari (2011, fig. 3): P. dichotoma and P. pennatus (Fig. 17.2–17.4). The Protovirgularia cf. pennatus specimen has a medial ridge (convex hyporelief) along the length of the trace, which becomes more prominent near the open end of the trace, characteristic of most Protovirgularia, including P. dichotoma. The striations that form the lateral lobes are very thin and arcuate and similar to the striations of the P. pennatus that form the lateral appendages. The specimen on KUMIP 204521 is winding and has a plumoselike, arcuate striation pattern similar to specimens of P. pennatus (Uchman, 1998, fig. 67A) and Protovirgularia isp. (Knaust, 2007, fig. 7B).

Type ichnospecies.—Rusophycus clavatus Hall, 1852, subsequent designation by Miller (1889, pg. 138).

Diagnosis.—Small to large bilobate mounds or depressions with parallel or merged lobes near the posterior; parallel to oblique to transverse striations; however, some specimens may be smooth (Crimes, 1970b, Osgood, 1970; Alpert, 1976a; Fillion & Pickerill, 1990; Keighley & Pickerill, 1996).

Discussion.—Seilacher (1970) grouped Rusophycus under Cruziana and argued that they should be considered synonymous due to both being produced by the same tracemaker, trilobites. Seilacher also suggested retaining Isopodichnus—morphologically similar to both Cruziana and Rusophycus—for use as a facies indicator for brackish water. Most workers disagree with the Seilacher (1970) suggestion and maintain Rusophycus and Cruziana as separate ichnogenera (See Cruziana for full discussion p. 13). Similar to Cruziana, Rusophycus ichnospecies are separated primarily by striation pattern, but size, lobe morphology (i.e., orientation, ornamentation, shape), and tracemaker morphologic remnants are other criteria sometimes used (Crimes, 1970b; Osgood, 1970; Seilacher, 1970, 2007).

Rusophycus is generally interpreted as a resting or hiding trace (e.g., Crimes 1970b; Osgood, 1970; Seilacher, 1970), but also suggested to be a hunting (e.g., Jensen, 1990; Tarhan, Jensen, & Droser, 2011) or nesting (brooding) trace (e.g., Fenton & Fenton, 1937d). Tracemakers of Rusophycus are commonly interpreted as arthropods, such as trilobites and crustaceans, but gastropods, and even some vertebrates have been proposed (e.g., Crimes, 1970a; Seilacher, 1970; Bromley & Asgaard, 1979; Seilacher, 2007). Post-Triassic Rusophycus are not considered produced by trilobites (Fillion & Pickerill, 1990). Jones (2016) showed small bilobate modern bat manus and pes track impressions similar to small, smooth Rusophycus (e.g., R. carbonarius), meaning that bats may have produced some Rusophycus in Cenozoic water-margin environments (e.g., fluvial, lake plain, crevasse-splay deposits). Rusophycus is a facies-crossing ichnogenus reported from shallow marine (e.g., intertidal, lagoon), deep marine (e.g., slope, basin), brackish, lacustrine, and fluvial deposits (e.g., Crimes, 1970b; Seilacher, 1970; Hakes, 1976, 1985; Bromley & Asgaard, 1979; Pollard, 1985; Pickerill, 1995; Garvey & Hasiotis, 2008; Jackson, Hasiotis, & Flaig, 2016). Rusophycus ranges from the Cambrian to recent (e.g., Crimes, 1987; Hasiotis, 2012).

Material.—KUMIP 204523 A and B (part and counterpart); 39 specimens, Miner's Hollow; KUMIP 314222 B: one specimen, Miner's Hollow; KUMIP 314223: two specimens, Antimony Canyon; KUMIP 314228: eight specimens, Miner's Hollow; KUMIP 314229: three specimens, Miner's Hollow; IBGS LG-M-011: one specimen; IBGS PJ-M-007: 13 specimens, Miner's Hollow; IBGS PJ-M-008: one specimen, Miner's Hollow; IBGS PJ-M-013: one specimen, Miner's Hollow; IBGS PJ-M-018: two specimens, Miner's Hollow; IBGS PJ-M-023: two specimens, Miner's Hollow.

Diagnosis.—Small, bilobate depressions (concave epirelief) or mounds (convex hyporelief) with parallel to slightly gaping lobes; transverse to oblique, fine striations that do not extend beyond the lobe margin, or may be smooth (modified from Keighley & Pickerill, 1997, 1998).

Description.—Small bilobate depressions and mounds with a central furrow, typically smooth but may have fine, oblique striations. Burrows 3.0–11.2 mm long and 2.5–6.5 mm wide at the widest point. Only one specimen has fine striations with a 97–120° V-shaped angle.

Occurrence.—Two lithologies: (1) gray (weathered to brown), laminated calcareous sometimes with brown siliciclastic sand; and (2) gray, siliciclastic silty shale, sometimes with brown carbonate sand.

Associated ichnotaxa.—Bergaueria hemispherica, Cruziana barbata, C. problematica, Gyrophyllites kwassizensis, Lockeia siliquaria, Monomorphichnus lineatus, M. cf. multilineatus, Planolites annularis, P. beverleyensis, P. montanus, Rusophycus cf. cerecedensis, Sagittichnus lincki, Treptichnus bifurcus, and T. vagans.

Discussion.—For a full list of synonymy, refer to Keighley and Pickerill (1996). Most Rusophycus specimens from the Spence Shale were assigned to R. carbonarius due to their small size, coffee bean-like shape, and the smoothness of the paired lobes. Normally, the main criterion for classifying ichnospecies of Rusophycus is the surficial striations present on the lobes. Rusophycus carbonarius is characterized by thin, transverse to oblique striations, but Keighley and Pickerill (1996) included small, smooth forms under R. carbonarius because they noted smooth and striated forms on the same samples. Keighley and Pickerill (1997) suggested that the difference between the two forms was taphonomic, rather than ethologic. Supporters of the Seilacher (1970) suggestion to include Rusophycus under Cruziana and the retention of Isopodichnus would likely identify R. carbonarius as Isopodichnus problematicus due to its small size and the lack of striations.

Rusophycus carbonarius specimens present in the Spence Shale are significantly smaller than any C. problematica specimen. This is most noticeable on KUMIP 204523 and PJ-M-007 (see Fig. 10.1), where significant differences in width between the two ichnogenera suggest that the same organism did not produce the two ichnofossils (sensu Fortey & Seilacher, 1997). We propose that agnostoid trilobites or small (juvenile) polymeroid trilobites likely produced the Rusophycus carbonarius specimens, whereas medium-sized (adult) polymeroid trilobites likely produced C. problematica specimens. Specimens are oriented in a nearly single direction between 315–350° (relative to the longer cut side of KUMIP 204523B), whereas the C. problematica show an overlapping, curvilinear pattern, suggesting that the bottom currents were relatively strong for smaller organisms and the R. carbonariustracemakers had to orient themselves to the current to remain stable (sensu Pickerill, 1995). Pickerill (1995) illustrated multiple oriented Rusophycus and interpreted their alignment was due to maintaining a rheotactic orientation in waters with significant bottom currents. Multiple specimens of R. carbonarius crosscut several C. problematica specimens suggesting that the R. carbonarius tracemakers may have occupied the area of KUMIP 204523 after the excavation of the C. problematica.

Material.—IBGS PJ-M-009: one specimen, Spence Shale float, High Creek Canyon, Bear River Range, Utah, USA

Diagnosis.—Small- to medium-sized bilobate depressions (concave epirelief) or mounds (convex hyporelief) with parallel to slightly gaping lobes, which widen anteriorly, and transverse to oblique, fine to well-developed striations; the medial furrow well developed and increases in depth and width toward one end, generally extending to entire length of the trace (Osgood, 1970; Fillion & Pickerill, 1990).

Description.—Convex, bilobate hyporelief mound with a central furrow, an anterior gape, and a merged posterior. Specimen 14.6 mm long, 9.7 mm wide, and 4.3 mm deep. Central furrow 1.4 mm wide.

Occurrence.—Tan to brown, siliciclastic shale with brown, dark gray, or black dendrites.

Associated ichnotaxa.—Sagittichnus lincki and Treptichnus bifurcus.

Discussion.—Only a single specimen of Rusophycus cf. pudicus was found in the Spence Shale. Like specimens of R. carbonarius, the R. cf. pudicus specimen has smooth lobes. The assignment to R. cf. pudicus is based on the depth increase of the medial furrow, length of furrow equaling the length of the trace, and the wide, well-developed lobes that taper to one end. Within the anterior gape of the central furrow, there is a raised area that may be a poorly preserved impression of the tracemaker coxa. The R. pudicus specimens illustrated by Osgood (1970) were much larger than the specimens shown here, but the size difference in the Spence Shale material could be due to decreased oxygenation or just a smaller tracemaker.

Material.—KUMIP 314228: two specimens, Miner's Hollow; IBGS PJ-M-023: one specimen, High Creek Canyon, Bear River Range, Utah, USA.

Diagnosis.—Medium-sized bilobate mound (convex hyporelief); lobes may be rounded or tapered to points and gape anteriorly; individual lobes may be smooth or with oblique to transverse striations.

Description.—Convex bilobate hyporelief mounds 12.5–28.9 mm long, 10.4–15.4 mm wide, and 1.5 mm deep. Medial furrow 1.9 mm wide but widens to 6.5 mm anteriorly with a ∼60° V-shaped angle. Oblique striations form ∼100° V-shaped angles.

Occurrence.—Brown to gray siliciclastic silty to sandy shale.

Associated ichnotaxa.—Cruziana problematica, Lockeia siliquaria, Monomorphichnus lineatus, M. cf. multilineatus, Planolites beverleyensis, P. montanus, and R. carbonarius.

Discussion.—Specimens assigned herein to Rusophycus cf. cerecedensis are distinguished from R. carbonarius and R. cf. pudicus by their larger size and rounded to tapered lobe shape. One specimen possibly records a predator-prey interaction with P. beverleyensis (see Fig. 15.5), similar to the association of R. carbonarius and P. montanus (see Fig. 18.3) and to other such associations of Rusophycus and simple burrows (e.g., Helminthopsis, Palaeophycus, or Planolites) (e.g., Jensen 1990; Tarhan, Jensen, & Droser, 2011). Another specimen has a P. montanus burrow oriented at an oblique angle on one lobe (Fig. 18.6), but since the burrow extends into the surrounding host rock, the association is likely not predation.

Type ichnospecies.—Sagittichnus lincki Seilacher, 1953b.

Diagnosis.—Small, subcircular to ovoid to arrowhead-shaped, convex mounds (hyporelief) or concave pits (epirelief), usually with medial keel; occurring in small to large groups; medial keel may or may not be present (Häntzschel, 1975; Głuszek, 1995; Garvey & Hasiotis, 2008).

Discussion.—Sagittichnus is described as small, keeled arrowheadshaped pits and mounds that are usually interpreted as resting traces of an unknown tracemaker (Seilacher, 1953b; Głuszek, 1995; Garvey & Hasiotis, 2008). Bromley and Asgaard (1979) reported specimens from Triassic fresh to brackish lacustrine deposits of Greenland that resembled Sagittichnus but interpreted them as inorganic tool marks, and thus invalid; however, other authors disagree and maintain Sagittichnus as a valid ichnogenus (e.g., Głuszek, 1995; Garvey & Hasiotis, 2008). A recent neoichnological study by Retrum, Hasiotis, and Kaesler (2011) showed freshwater ostracodes producing Sagittichnus-like morphologies. Sagittichnus has also been associated with small arthropod trackways (Głuszek, 1995). Sagittichnus is similar to manus and pes track impressions of modern bat trackways (Jones, 2016). Sagittichnus may occur with or grade into deposit feeding, hiding, or resting traces like Rusophycus (Garvey & Hasiotis, 2008). Sagittichnus has been reported from shallow marine and freshwater to brackish continental deposits (e.g., estuarine, fluvial, lacustrine) (e.g., Bromley & Asgaard, 1979; Głuszek, 1995; Garvey & Hasiotis, 2008; Jackson, Hasiotis, & Flaig, 2016). Sagittichnus ranges from the Cambrian to recent (Bednarczyk & Przybyołwicz, 1980; Retrum, Hasiotis, & Kaesler, 2011; Jackson, Hasiotis, & Flaig, 2016).

Material.—IBGS LG-M-002: five specimens, Winter Hollow, Box Elder Mountain; IBGS LG-M-003: 20 specimens; IBGS LG-M-013: 15 specimens, Antimony Canyon; IBGS PJ-M-025: 15 specimens, Spence Shale Float, Cataract Canyon.

Diagnosis.—Small, subcircular to ovoid to arrowhead-shaped, convex mounds lacking discrete medial keels (Garvey & Hasiotis, 2008).

Description.—Small, convex hyporelief mounds without medial keel or furrow. Specimens 1.0–2.7 mm long and 0.7–4.6 mm wide.

Occurrence.—Tan to dark gray, carbonate or siliciclastic shale.

Associated ichnotaxa.—Bergaueria hemispherica, Gyrophyllites kwassizensis, Lockeia siliquaria, Teichichnus cf. nodosus, and Treptichnus bifurcus.

Discussion.—Specimens were assigned to Sagittichnus due to their small, subrounded to ovoid-shaped, convex-mound (hyporelief) morphology, and their highly concentrated groupings (Fig. 19.1–19.2). No specimen had the characteristic medial keel (finlike structure) preserved in either epi- or hyporelief. Most specimens are ovoid in shape, but some show a subrounded to arrowhead shape. Also present on IBGS LG-M-003, alongside some S. lincki, is an ovoid-shaped, convex mound that we consider Lockeia for its noticeably larger size than the surrounding Sagittichnus, the lack of a medial keel, and its tapered ends.

Type ichnospecies.—Scolicia prisca de Quatrefages, 1849.

Diagnosis.—Variable and selectively preserved, simple, winding to meandering to coiling, bilobate or trilobate backfilled burrows; may have one or two parallel, locally discontinuous strings along base; area between strings flat to slightly convex; cross sections circular to oval; geopetal meniscate backfill common but massive burrow infill also common (Häntzschel, 1975; Uchman, 1995).

Discussion.—There are many ichnogenera with morphologies similar to Scolicia, informally grouped in the Scolicia Group by Häntzschel (1975, p. 106). Many ichnotaxa from the Scolicia Group were later synonymized with Scolicia (e.g., Uchman, 1995). Plaziat and Mahmoudi (1988) suggested restricting Scolicia to concave epirelief expressions and retaining Subphyllochorda Götzinger & Becker, 1932 for convex hyporeliefs of echinoid traces; however, this complicates ichnotaxonomy more than it helps, and thus, subsequent authors have rejected this suggestion (e.g., Uchman, 1995, 1998; Fu & Werner, 2000).

Scolicia is commonly interpreted as a locomotion or depositfeeding trace (e.g., Fu & Werner, 2000); however, some authors have interpreted Scolicia to be a grazing trace (e.g., Uchman, 1995). Scolicia is commonly interpreted as the product of irregular echinoids in the Mesozoic and Cenozoic (Plaziat & Mahmoudi, 1988; Uchman, 1995, 1998), whereas Paleozoic producers were likely gastropods (e.g., Götzinger & Becker, 1932; Häntzschel, 1975; Książkiewicz, 1977). In continental environments since the Devonian, producers were also likely gastropods (e.g., Hasiotis, 2004, 2008; Ash & Hasiotis, 2013). Scolicia has been reported from shallow marine as well as deep marine deposits, including turbidites (Uchman, 1995; Fu & Werner, 2000); however, Fu and Werner (2000) suggested that most shallow marine Scolicia are commonly destroyed by overprinting of deep-penetrating traces. Scolicia tracemakers preferred fine sandy to coarse silty settings, suggesting a preference for lower energy environments (Fu & Werner, 2000). Scolicia ranges from the Cambrian to recent (e.g., Häntzschel, 1975; Fu & Werner, 2000).

Material.—IBGS PJ-M-032: four specimens, Miner's Hollow, Wellsville Mountains, Utah, USA.

Diagnosis.—Short to elongated, cylindrical to subcylindrical burrows in endorelief; undertrace in concave epirelief and convex hyporelief, some may be bilobate with basal medial furrow.

Description.—Light to medium brown to gray burrows 17.6– 33.1 mm wide, 5.0–14.6 mm thick, with dark gray burrow margins 0.8–2.7 mm thick. Burrow infills are subangular to subrounded, moderately well-sorted, fine to medium carbonate sand with small reddish brown to red grains and large, very euhedral, dark grains with penetration twinning.

Occurrence.—Light to dark gray, laminated siliciclastic mudstone. Laminations are < 3 mm thick. Soft-sediment deformation is present locally around the burrow with flame structures penetrating or deforming the burrow margin. Laminations above and below the Scolicia isp. lack significant bioturbation but several small burrows are present indicating an ii2, whereas the layer with the Scolicia specimen has an ii4–5.

Associated ichnotaxa.—None.

Discussion.—Specimens assigned to Scolicia (Fig. 20.1–20.2) lack the diagnostic basal bilobate or trilobate shape or double drainage furrows. Cross sections reveal four elliptical burrows with irregularly shaped margins filled with a light to medium brown to gray, fine to medium sand in a matrix of laminated, light gray silt to fine sand (Fig. 20.3–20.6). The burrow margins are composed of dark gray, fine to medium sand (Fig. 20.3). One burrow appears bilobate from presence of a possible medial furrow composed of a wedge of light gray mud partially separating the burrow into two lobes (Fig. 20.4); however, the medial ridge may be due to compaction and soft-sediment deformation (e.g., flame structures) as other burrows have similar structures penetrating them from the sides. Also present is possible fecal-drainage canal near the base of one lobe, formed by a circle of dark sand grains with a brown core (Fig. 20.4). The irregularity of the dark burrow margins may also be the result of soft-sediment deformation and postdepositional diagenesis. The burrow infill has multiple coarse, angular, dark grains that may have resulted from recrystallization during diagenesis, as some of the grains are very euhedral and one grain appears to exhibit penetration twinning (Fig. 20.5–20.6).

Type ichnospecies.—Taenidium serpentinum Heer, 1877.

Diagnosis.—Unlined to thinly lined, unbranched, straight to sinuous, cylindrical burrows with meniscate segmented burrow fill (D'Alessandro & Bromley, 1987).

Discussion.—Prior to D'Alessandro and Bromley (1987) reexamining the original descriptions and type material of Muensteria Sternberg, 1833 and Taenidium Herr, 1877, most workers used Muensteria for unbranched, unlined meniscate burrows, whereas Taenidium was used for branching meniscate burrows. Muensteria was considered invalid as the original description was confusing and included algae, coprolites, and several forms of Chondrites Sternberg, 1833 (D'Alessandro & Bromley, 1987). Taenidium was recommended for unbranched meniscate burrows previously described as Muensteria and a new ichnogenus, Cladichnus, was erected for meniscate burrows with primary successive branching or radiating systems (D'Alessandro & Bromley, 1987).

Keighley and Pickerill (1994) reviewed Beaconites Vialov, 1962, and compared it to other meniscate-backfilled burrows, Ancorichnus Heinberg, 1974, and Taenidium. They considered Beaconites barretti Bradshaw, 1981, as an unlined, unwalled meniscate burrow belonging to Taenidium and argued that the ends of the menisci do not form a wall or lining. Many authors followed Keighley and Pickerill (1994) for the use of Taenidium barretti (e.g., Schlirf, Uchman, & Kümmel, 2001; Keighley & Pickerill, 2003; Buatois & others, 2007).

Beaconites barretti is valid and still retained by many authors (e.g., Morrissey & Braddy, 2004; Smith & Hasiotis, 2008; Smith & others, 2008b; Counts & Hasiotis, 2009) because its architectural morphology is clearly distinct from Taenidium, rejecting the synonymy of most backfilled burrows into Taenidium by Keighley and Pickerill (1994). Beaconites is an unlined, tightly spaced backfilled meniscate burrow where the backfills merge laterally to form a crenulated burrow wall, representing the remnant of an open cell as it was moved through the sediment. We find the Keighley and Pickerill (1994) definitions of walls and linings to be confusing and inappropriate to all backfilled-burrow morphologies. Keighley and Pickerill (1994) considered backfilled burrows to not have true walls or linings as they considered simple excavation to not be a form of active construction, their requirement for walls and linings. They also interchanged the terms wall and lining, causing their definitions and usage to become muddled. Linings are only one possible type of wall structure (sensu Bromley, 1996), whereas Keighley and Pickerill (1994, fig. 1) considered all walled ichnofossils to have linings or mantles. A wall is the outermost margin of the area the tracemaker occupied—regardless of its active or passive excavation or construction (contra Keighley & Pickerill, 1994)—where the burrow infill contacts the matrix (sensu Morrissey & Braddy, 2004). Smith and others (2008b) argued that the overlapping of menisci form a crenulated, but unlined, wall in B. barretti reflecting active excavation of the sediment by the tracemaker, relocating it to the rear of the active cell, and compacting it to form the rear wall. We, therefore, follow Smith and others (2008b) for the retention of Beaconites barretti and definitions of walls vs. lining. Taenidium should be restricted to burrows that exhibit thick, regularly spaced meniscate backfill that is symmetrical about the axis of the burrow, which is unlined and unbranched (D'Alessandro & Bromley, 1987; Smith & others, 2008b). Prior to the inclusion of B. barretti by Keighley and Pickerill (1994), Taenidium was only described from marine deposits. Taenidium reported from continental deposits (e.g., Savrda & others, 2000; Buatois & Mángano, 2002, 2007, 2011; Krapovickas & others, 2009; Scott & Smith, 2015) actually belong to: (1) Naktodemasis Smith & others, 2008b, if the thin meniscate backfill are organized into discreet packages; (2) Beaconites, if the menisci are uneven, alternate around a central axis, and not organized into discreet packages; or (3) Ancorichnus Heinberg, 1974, if a mantle is present (e.g., Smith & others, 2008b; Counts & Hasiotis, 2009; Morshedian, MacEachern, & Dashtgard, 2012; Gingras & others, 2016; Harris & others, 2016).

Taenidium is interpreted as a deposit-feeding trace of marine worms (Gevers & others, 1971; Keighley & Pickerill, 1994; Smith & others, 2008b). Taenidium has been reported from shallow- to deep-marine deposits (Keighley & Pickerill, 1994, fig. 5; Smith & others, 2008b; Jackson, Hasiotis, & Flaig, 2016). Taenidium has been reported from the Vendian (i.e., Ediacaran) by Germs (1972) and Jenkins (1995); however, Jensen, Droser, and Gehling (2006), considered them as a cast of Cloudina and a tubular fossil, respectively. We follow the interpretation of Germs (1972) and Jenkins (1995) based on the similarity of the morphologies to Taenidium. Therefore, Taenidium ranges from the Ediacaran to recent (e.g., Germs, 1972; Crimes, 1992; Jenkins, 1995; Uchman, 1998; Jackson, Hasiotis, & Flaig, 2016).

Material.—IBGS PJ-M-002: one specimen, Miner's Hollow; IBGS PJ-M-005: one specimen, Spence Shale float, Miner's Hollow.

Diagnosis.—Long, slightly sinuous to straight burrow with uniform, evenly spaced, meniscate backfill; meniscate packages shorter than burrow diameter and filled with alternating sediment types (D'Alessandro & Bromley, 1987).

Description.—Straight to gently curved, endorelief burrow with gray meniscate backfill and brown to purple weathered infill. Burrows 152.2–159.4 mm long, 6.3 mm wide; burrow menisci ∼1.5 mm thick and uniform.

Occurrence.—Two lithologies: (1) tan to light brown, siliciclastic silty shale; and (2) gray, calcareous shale.

Associated ichnotaxa.—Archaeonassa jamisoni, Phycodes curvipalmatum, and Planolites; montanus.

Discussion.—The long, mostly straight burrow on IBGS PJ-M-002 was assigned to Taenidium cf. satanassi due to the presence of meniscate backfill exposed by a large ovoid depression, herein designated as Archaeonassa jamisoni. Exposed menisci are shorter designated as Archaeonassa jamisoni. Exposed menisci are shorter than the burrow diameter but lack the sediment alternation characteristic of T. satanassi (Fig. 19.3–19.4). The rest of the specimen occurs in endorelief and shows no clear internal structure; however, the purple coloration of the weathered burrow infill has a slight serrated pattern near the burrow margins, possibly a diagenetic remnant of the meniscate backfill. The specimen of Taenidium cf. satanassi on IBGS PJ-M-005 is completely in endorelief, revealing no internal morphology, and is in close proximity to several A. jamisoni specimens.

Type ichnospecies.—Teichichnus rectus Seilacher, 1955b, by original monotypy.

Diagnosis.—Long, wall-shaped, septate structures consisting of stacks of gutter-shaped laminations (Seilacher, 1955b Fillion & Pickerill, 1990).

Discussion.—Teichichnus was introduced for vertically stacked, horizontal burrows with spreiten and thought to be produced by upwardly shifting deposit feeders (Seilacher, 1955b Fillion & Pickerill, 1990). Teichichnus has been reported to intergrade with multiple ichnofossils: Cruziana, Ophiomorpha Lundgren, 1891, Phycodes, Rhizocorallium Zenker, 1836, and Thalassinoides Ehrenberg, 1844 (e.g., Fillion & Pickerill, 1990; Loope & Dingus, 1999). Teichichnus has been noted for its similarity to Trichophycus Miller & Dryer, 1878, due to the presence of gutter-shaped spreite (e.g., Osgood, 1970; Frey & Howard, 1985; Geyer & Uchman, 1995), but can be typically distinguished by the more planar shape of the spreite and a lack of fine striations present on the outside of the burrow (e.g., Fillion & Pickerill, 1990; Jensen, 1997). Some Teichichnus have been reported to have surficial striations (e.g., Jensen, 1997).

Teichichnus is typically interpreted as a deposit-feeding or grazing trace of annelids and arthropods (e.g., Chisholm, 1970; Fillion & Pickerill, 1990). Teichichnus primarily occurs in shallow-marine deposits (e.g., tidal flats and deltas) but some have been reported from deep-marine (e.g., submarine fans and abyssal plain) and brackish-marine (meso- to polyhaline) water deposits (e.g., Fürsich, 1975; Fillion & Pickerill, 1990; Pemberton & Wightman, 1992; Gingras, MacEachern, & Pemberton, 1998; Jackson, Hasiotis, & Flaig, 2016). Teichichnus ranges from the early Cambrian to recent (e.g., Narbonne & others, 1987; Fillion & Pickerill, 1990; MacNaughton & Narbonne, 1999).

Material.—IBGS PJ-M-025: one specimen, Spence Shale Float, Cataract Canyon.

Diagnosis.—Large, curved, undulating burrow with spreiten forming chain of irregularly spaced nodes preserved in convex hyporelief (Fillion & Pickerill, 1990).

Description.—Curved, undulating, segmented burrow with retrusive spreite. Burrow 73.4 mm long, 7.2–12.5 mm wide, and burrow segments and internodes 2.8–4.3 mm thick. Light to dark gray spreite 0.3–0.6 mm thick, and composed of fine to very fine sand.

Occurrence.—Light to dark gray (weathered to tan), laminated fine to very fine sand.

Associated ichnotaxa.—Bergaueria hemispherica and Sagittichnus lincki.

Discussion.—Teichichnus cf. nodosus (Fig. 19.5) was assigned due to its similarity to the undulating and nodular morphology of T. nodosus Fillion & Pickerill, 1990. This specimen also occurs with a partial eocrinoid, Gogia granulosa Robison, 1965. The specimen of Teichichnus cf. nodosus terminates near a B. hemispherica (see Fig. 6.6). A cross section of T. cf. nodosus reveals several gutter-shaped spreiten that alternate between brown, light gray, and dark gray fine-grained sand (Fig. 19.6).

Type ichnospecies.—Treptichnus bifurcus Miller, 1889 (p. 581).

Diagnosis.—Chains of horizontal to subhorizontal, straight to curved, zigzagging burrow segments associated with vertical to oblique tubes producing a three-dimensional burrow structure; pits and nodules may occur near top or base of burrow segments at sediment interfaces (Buatois & Mángano, 1993a; Uchman, Bromley, & Leszczyński, 1998).

Discussion.—Miller (1889) named Treptichnus for forked, zigzagging burrows with projected burrow ends; Miller interpreted the burrow projections as indicating the direction of tracemaker movement and were produced by insect larvae or pupa. Along with Treptichnus, Miller (1889) also described and commented on Haplotichnus and Plangtichnus as being very similar to Treptichnus in terms of size, tracemaker, and morphology. Plangtichnus is similar to Treptichnus and was originally described as a zigzag trail with pits deeper than the rest of the trail (Miller 1889, p. 580). Archer and Maples (1984) and Maples and Archer (1987) argued that Plangtichnus is distinguishable from Treptichnus by the lack of burrow-end projections that yields a highly angular zigzagging form; however, Buatois and Mángano (1993a) argued that the projections of Treptichnus and the pits of Plangtichnus represented morphologically similar vertical shafts along the burrow system and that the lack of the burrow-end projections was likely caused by erosion. Buatois and Mángano (1993a) claimed that, since both ichnogenera had similar morphology and represented similar behaviors, Plangtichnus and Treptichnus should be considered synonymous. They retained Treptichnus for nomenclatural stability and considered Plangtichnus to be nomen oblitum, citing relative nonuse of the name. Treptichnus pollardi was, therefore, erected as a new ichnospecies to replace the name for the morphology previously associated with Plangtichnus erraticus (Buatois & Mángano, 1993a).

Treptichnus is commonly interpreted as a deposit-feeding trace (Buatois & Mángano, 1993a, 1993b; Uchman, Bromley, & Leszczyński, 1998), but has also been interpreted to be an agricultural, grazing, reproduction, and predation or scavenging trace (e.g., Rindsberg & Kopaska-Merkel, 2005; Seilacher, 2007; Vannier & others, 2010; Wilson & others, 2012; Getty & others, 2016). Treptichnus is interpreted as being produced by marine annelid worms (e.g., Buatois & Mángano, 1993a, 1993b; Uchman, Bromley, & Leszczyński, 1998; Vannier & others, 2010) and some insect larvae in continental environments since the Pennsylvanian (e.g., Miller, 1889; Rindsberg & Kopaska-Merkel, 2005; Getty & others, 2016). Treptichnus has been reported from shallow- and deep-marine, and continental proximal floodplain and proximal lacustrine deposits (e.g., Archer & Maples, 1984; Buatois & Mángano, 1993b; Jensen, 1997; Uchman, Bromley, & Leszczyński, 1998; Wilson & others, 2012; Getty & others, 2016). Treptichnus ranges from the Cambrian to recent (e.g., Buatois & Mángano, 1993a, 1993b; Uchman, Bromley, & Leszczyński, 1998; Vannier & others, 2010; Hasiotis, 2012); however, some Treptichnus have been reported from the Edicaran and were suggested to represent a gradual increase in ichnofossil complexity until the first occurrence of T. pedum at the Precambrian-Cambrian boundary (e.g., Germs, 1972; Jensen & others, 2000; Gehling & others, 2001; Droser & others, 2002).

Material.—KUMIP 204523 A+B; one specimen, Miner's Hollow; KUMIP 314230; one specimen, Antimony Canyon; KUMIP 314250; three specimens, Miner's Hollow; KUMIP 314283: one specimen; IBGS PJ-M-006; one specimen, Miner's Hollow; IBGS PJ-M-008: one specimen, Miner's Hollow; IBGS PJ-M-009: one specimen, Spence Shale float, High Creek Canyon, Bear River Range, Utah, USA; IBGS PJ-M-028: one specimen, Spence Shale Float, Miner's Hollow; IBGS PJ-M-030 (part and counterpart): one specimen, Miner's Hollow.

Diagnosis.—Burrow system with short projections between elongate, thin, and horizontal burrow segments forming straight to slightly curved, zigzagged chains; may occur as chains of evenly spaced beads or depressions alternating around central axis, forming zigzag pattern (Buatois & Mángano, 1993a; Uchman, Bromley, & Leszczyński, 1998).

Description.—A zigzag-segmented burrow system 30.2–120.3 mm long, 8.6–18.4 mm wide with burrow projections. Segments 7.4–33.2 mm long, 1.1–4.7 mm wide; circular to subrounded, depression or bead diameter 1.9–3.9 mm, nonalternating beads spaced 10.7–23.7 mm; whereas alternating beads spaced 5.5–21.0 mm. Angles between burrow segments range from 66–129°, average 99°. Specimens occur in concave and convex hyporelief and epirelief.

Occurrence.—Thickly laminated to massive, medium to dark gray or tan to light brown, siliciclastic silty or calcareous shale.

Associated ichnotaxa.—Cruziana problematica, Gyrophyllites kwassizensis, Lockeia siliquaria, Monomorphichnus lineatus, M. cf. multilineatus, Planolites beverleyensis, P. montanus, Rusophycus carbonarius, Rusophycus cf. pudicus, Sagittichnus lincki, and Treptichnus vagans.

Discussion.—Treptichnus bifurcus is the most common form of Treptichnus from the Spence Shale. Specimens exhibit two primary morphologies with most occurring as chains of simple, short, straight zigzagging burrow segments with short projections of the older segment past the start of new segment (Fig. 21.1, 21.3–21.5). The other T. bifurcus morphology has more curved or slightly meandering burrow segments (Fig. 21.2, 21.6). The projections at the end of burrow segments have been interpreted as compressed portions of the oblique shafts (Maples & Archer, 1987). Getty and others (2016), however, recently argued that burrow projections in Treptichnus were not formed by compression and resulted from the tracemaker backing into the previous segment, changing directions, and constructing a new segment within the same plane. Treptichnus bifurcus is one of the few traces previously reported from the Spence Shale by Robison (1969, pl. 138, fig. 5) as “burrow type A” and “feather-stitch burrow”. The term “feather-stitch trail” was widely used in the literature prior to the 1970s before the rediscovery of the Miller (1889) paper (Buatois & Mángano, 1993a; Uchman, Bromley, & Leszczyński, 1998).

Alternating beaded T. bifurcus specimens (Fig. 22.1–22.3) are similar to the upper surface features of T. bifurcus and T. pollardi in Buatois and Mángano (1993a, fig. 2B, 3B). Reconstructions of T. bifurcus and T. pollardi show both ichnospecies may occur as a series of pits alternating along a central axis in the upper portions of Treptichnus systems and were interpreted as the burrow apertures of vertical to oblique shafts (Buatois & Mángano, 1993a). Since both T. bifurcus and T. pollardi may occur as alternating pits, assignment of alternating beaded specimens to any one Treptichnus ichnospecies is usually not possible. Specimens present on IBGS PJ-M-006, however, occur in very close proximity to a long T. bifurcus specimen with similar diameters of burrow segments, suggesting the specimen could be part of the T. bifurcus and, thus, included within the type ichnospecies.

Alternating beaded T. bifurcus specimens also bear a resemblance to Treptichnus isp. 5 from Buatois and Mángano (1993a, fig. 4), which also occurs as a chain of alternating pits. Treptichnus isp. 5 pits, however, are connected into pairs by burrow segments that do not connect to another pit-burrow segment pair, whereas alternating beaded T. bifurcus specimens are not connected into pairs. Treptichnus specimens from the Eocene Green River Formation (Hogue & Hasiotis, in review) share the alternating beaded T. bifurcus morphology and grade into a single-chain, beaded morphology, which in turn grades into a pitted furrow Ptychoplasma (Protovirgularia) vagans-like morphology (for discussion see Treptichnus vagans p. 43).

Material.—IBGS PJ-M-017: one specimen, Spence Shale Float, Miner's Hollow; IBGS PJ-M-027: one specimen, Miner's Hollow.

Diagnosis.—Treptichnus burrow system consisting of subhorizontal, straight to curved primary burrow with multiple successive burrow segments branching off in regular intervals (Fillion & Pickerill, 1990; Jensen, 1997).

Description.—Winding burrow system with systematic projection of burrow segments from a primary burrow. Burrow system 26.6–131.5 mm long, 10.2–18.8 mm wide. Burrow segments 6.4–41.8 mm long, 0.6–4.9 mm wide.

Occurrence.—Laminated light gray and medium gray or medium gray and dark gray calcareous silty shale.

Discussion.—Originally, the epithet “pedum” was assigned to Phycodes by Seilacher (1955b) for a system of burrow segments that successively branch off along a primary tunnel. Jensen (1997) transferred Phycodes pedum to Treptichnus (see Jensen, 1997 for discussion). Geyer and Uchman (1995) transferred P. pedum to Trichophycus due to the presence of Teichichnus-like spreiten in some burrow segments; however, most authors currently follow Jensen (1997) on the use of Treptichnus pedum (e.g., Jensen & others, 2000; Seilacher, 2007; Wilson & others, 2012; Buatois, Almond, & Germs, 2013). In an attempt to make ichnotaxonomy follow the rules of parsimony common in other areas of science, Dzik (2005) proposed that ichnofossils should be viewed as body fossils and split Treptichnus and placed T. pedum into one of two new worm genera, Manykodes. We disagree with the Dzik (2005) proposal, as parsimony is not always applicable to ichnotaxonomy and to consider ichnofossils as biological taxa would greatly diminish their usefulness in sedimentology and stratigraphy.

Treptichnus pedum specimens occur as convex hyporeliefs on samples IBGS PJ-M-017 and IBGS PJ-M-027. On IBGS PJ-M-017, T. pedum occurs in hyporelief and most burrow segments are convex, whereas others are concave (Fig. 23.1). Treptichnus pedum also occurs with some specimens of Cruziana problematica. The burrow segments are elongated and straight to curved extending from a master tunnel (Maples & Archer, 1987). Some of the straighter segments widen at one end, which suggest the segments were oriented obliquely to bedding and later flattened during compaction like in specimens of T. bifurcus.

Thin, threadlike discontinuous trails–Germs, 1972, p. 866, pl. 1, fig. 5, 7, pl. 2, fig. 1.

^*Tuberculichnus vagans—Książkiewicz, 1977, p. 140, pl. 13, fig. 4, text-fig. 27C–G.

Tuberculichnus meandrinus—Książkiewicz, 1977, p. 141, pl. 13, fig. 5–6, text-fig. 27A–B.

Hormosiroidea canadensis—Crimes & Anderson, 1985, p. 325, fig. 8.1, 9.

Hormosiroidea arumbera—Walter, Elphinstone, & Heys, 1989, p. 244, fig. 14D–E, 15B, 15D.

Hostynichnium duplex—Plička & Siránová, 1989, p. 110, pl. 63.

Tuberculichnus vagans Książkiewicz—Uchman, 1991, p. 209.

Tuberculichnus vagans Książkiewicz—Uchman, 1992, p. 432.

String pits—Buatois & Mángano, 1993b, p. 246, fig. 4G.

non Tuberculichnus vagans Książkiewicz—Löffler & Geyer, 1994, p. 513, fig. 4E (=Margaritichnus or Microspherichnus).

Tuberculichnus meandrinus Książkiewicz—Paczesna, 1996, p. 67, pl. 29, fig. 5.

Tuberculichnus vagans Książkiewicz—Pacześna, 1996, p. 67, pl. 29, fig. 8, [non pl. 30, fig. 1, 3].

Tuberculichnus vagans Książkiewicz—Buatois & others, 1995, p. 268, fig. 6A, B, 7–8.

Tuberculichnus vagans Książkiewicz—Buatois & others, 1996, p. 296, fig. 10C–D.

Protovirgularia vagans (Książkiewicz)—Uchman, 1998, p. 166, fig. 70.

Treptichnus pedum triplex (Seilacher)—Seilacher, 2007, p. 182, pl. 64, fig. A–B.

Protovirgularia vagans (Książkiewicz)—Uchman, 2007, p. 230, pl. 3, fig. 10, pl. 4, fig. 1.

Tuberculichnus vagans (Książkiewicz)—Uchman, 2008a, p. 64, fig. 120.

Protovirgularia vagans (Książkiewicz)—Uchman, 2008b, p. 130, fig. 8.8 B–C.

Ptychoplasma vagans (Książkiewicz)—Uchman, Mikuláš, & Rindsberg, 2011, p. 394, fig. 3A–G, 4A–B.

Linear rosary structures—Caron and others, 2010, Supplementary material 8, p. 16, fig. DR6 A–B.

Rosary-like structures—Mángano, 2011, p. 98, text-fig. 3, 4C–D, 5, 6A–F.

Ptychoplasma vagans (Książkiewicz) (as Fenton & Fenton, 1937b)— Alonso-Muruaga, Buatois, & Limarino, 2013, p. 232, fig. 3E.

non Ptychoplasma vagans (Książkiewicz)—Paranjape, Kulkarni, & Gurav, 2013, p. 1366, pl. 3, fig. G–I (=Halopoa or Palaeophycus).

non Ptychoplasma vagans (Książkiewicz)—Hagdorn, 2014, p. 268, fig. 12.2. (=Lockeia).

non Ptychoplasma vagans (Książkiewicz)—Knaust, Warchoł, & Kane, 2014, p. 2252, fig. 6D (=Palaeophycus or Planolites).

Ptychoplasma vagans (Książkiewicz)—Stachacz, 2016, p. 316, fig. 17 G.

Treptichnus bifurcus Miller—Getty & others, 2016, p. 273, fig. 4.5.

Material.—KUMIP 314122: one specimen, Antimony Canyon; KUMIP 314217: one specimen, Miners Hollow; KUMIP 314222 A–C: five specimens, Miner's Hollow; KUMIP 314233: one specimen; KUMIP 314235: one specimen; IBGS LG-M-004: one specimen; IBGS LG-M-012: one specimen; IBGS LG-M-013: two specimens; IBGS PJ-M-008: one specimen, Miners Hollow; IBGS PJ-M-014: one specimen, Miners Hollow; IBGS PJ-M-019: two specimens, Miners Hollow; IBGS PJ-M-031: four specimens.

Emended Diagnosis.—Irregularly meandering or looping, discontinuous trail of variably spaced, short to elongate, ovoid to irregular to circular beads (hyporelief) or depressions (epirelief).

Description.—Trails 16–314 mm long, may overlap and cross each other. Beads 0.6–7.0 mm long, 0.6–3.3 mm wide, spaced 0.7–7.0 mm apart. Most specimens are convex hyporelief; however, two specimens are concave epirelief (KUMIP 314122 and KUMIP 314235), and one specimens is preserved as part and counterpart (KUMIP 314233).

Occurrence.—Three lithologies: (1) gray (weathers to brown), mica-rich silty shale; (2) dark gray calcareous shale; and (3) gray to dark gray siliciclastic shale.

Associated ichnotaxa.—Dimorphichnus isp., Diplichnites gouldi, Halopoa aff. imbricata, Lockeia siliquaria, Monomorphichnus bilinearis, Phycosiphon incertum, Planolites montanus, Protovirgularia cf. pennatus, Rusophycus carbonarius, Sagittichnus lincki, and Treptichnus bifurcus.

Discussion.—Originally, the epithet “vagans” was assigned to Tuberculichnus by Książkiewicz (1977) for irregularly winding chains of ridgelike knobs. Uchman (1998) moved Tuberculichnus vagans to Protovirgularia for the amygdaloidal shape of said knobs. Uchman, Mikuláš, and Rindsberg (2011) later transferred Protovirgularia vagans to Ptychoplasma Fenton & Fenton, 1937b, for the carinate shape of the knobs. Mángano and others (2002) suggested P. vagans should be considered a form of Lockeia due to its amygdaloidal, carinate shape, and lack any chevronate patterns. Ptychoplasma vagans from Paranjape, Kulkarni, and Gurav (2013) closely resemble Halopoa or Palaeophycus and lack the diagnostic beaded morphology. Hagdorn (2014) illustrated P. vagans specimens occurring in short chains and not winding chains as in the type material. The P. vagans specimens illustrated by Knaust, Warchoł, and Kane (2014) do not form chains, and the ridgelike knobs do not appear connected. The repeated transfer of P. vagans and wide range of reported morphologies has caused a significant problem regarding its identification and ichnotaxonomic status.

Herein, we transfer P. vagans to Treptichnus based on morphological similarities to this ichnotaxon in an attempt to stabilize the nomenclature. The morphology of P. vagans is ill suited for inclusion in Protovirgularia, Ptychoplasma, and Lockeia due to the lack of chevronate and bilobate morphology and the beaded morphology that does not match the type material, respectively. Spence Shale specimens are most similar to P. vagans as both share a winding, single-chain beaded morphology in convex hyporelief. Ptychoplasma vagans, however, sometimes forms irregularly shaped furrows in concave epirelief, which some Spence Shale specimens do as well (Fig. 23.2). Similar to both ichnotaxa is a specimen of Treptichnus from the Eocene Green River Formation (Fig. 23.4), which incorporates aspects of Spence Shale chain specimens, alternating beaded Treptichnus bifurcus, and P. vagans to form: (1) a concave epirelief, alternating beaded morphology (=beaded Treptichnus bifurcus); (2) transitions to a beaded singlechain morphology (=beaded Treptichnus pedum); and then to (3) a pitted furrow morphology (=P. vagans sensu Uchman, Mikuláš, & Rindsberg, 2011) (Hogue & Hasiotis, in review). Due to the similar morphology between ichnotaxa, we, therefore, place Ptychoplasma (Protovirgularia) vagans within Treptichnus as a valid ichnospecies, and it should be referred to as Treptichnus vagans. We interpret the nodes or pits at the base or top of vertical to subvertical shafts as similar to those in T. bifurcus and T. pollardi, as well as a Treptichnus where the tracemaker probed through the sediment interface in a relatively straight line. Erosion of the upper part of the trace would leave an apparent string of beads, with or without remnants of the associated shafts.

Treptichnus vagans is composed of long, winding trails of beads that vary in shape from circular to ovoid to irregular (Fig. 23.2–23.3,5, Fig. 24.1). Most specimens with circular beads cross themselves (Fig. 23.2,5); whereas, only one specimen with ovoidshaped beads does (Fig. 24.1). The individual bead shape in a single chain is not always morphologically uniform. One specimen with ovoid-shaped beads has short “drag” marks on one end of the beads extending in the same direction, which are interpreted as insertion furrows (see Fig. 23.3). Another specimen has a mix of different bead morphologies: ovoid, fluted (grooves), imbricated, and triangular (Fig. 24.2–24.6). The fluted and triangular bead morphologies may have been produced by protobranch mollusks due to their V shape (sensu Seilacher & Seilacher, 1994).

Treptichnus vagans is similar to numerous “string-of-pearls” ichnotaxa, such as Margaritichnus Bandel, 1973, and Microspherichnus Hakes, 1976. Both ichnotaxa consist of long, sometimes meandering, trails of circular to oval-shaped depressions or mounds. Margaritichnus is usually preserved in convex epirelief with mounds closely spaced that are commonly in contact with each other (Hakes, 1976). Microspherichnus is also preserved in convex epirelief with irregularly spaced beads that may or may not be in contact with each other (Hakes, 1976; Fillion & Pickerill, 1990). Treptichnus vagans specimens also resemble the “string pits” of Buatois and Mángano (1993b, fig. 4G). The “string pits” were described as a hypichnial chain of small, subrounded to oval mounds (< 1 mm) spaced 0.5–4.0 mm apart (max. length = 100 mm) and originally interpreted as locomotion traces of an unknown arthropod. The Buatois and Mángano (1993b) “string pits” are included within T. vagans.

Some Treptichnus pedum specimens have been reported with a beadlike morphology similar to T. vagans. Treptichnus pedum specimens from the lower Cambrian of Namibia commonly occur in long, sinuous chains with ovoid to subrounded to circular beads (e.g., Germs, 1972; Jensen & others 2000; Seilacher, 2007; Wilson & others, 2012). Germs (1972) described long, sinuous chains of discontinuous ridges that were later regarded as Treptichnus pedum triplex by Seilacher (2007). The discontinuous ridges of Germs (1972) are almost identical to the Książkiewicz (1977) type material and are included in T. vagans. Multiple specimens of T. pedum with subrounded to circular beads were reported from the lower Cambrian of Namibia (Wilson & others, 2012, fig. 10–12). Some of the Namibian T. pedum specimens with beads are amalgamated together to form recognizable burrow segments (Wilson & others, 2012, fig. 12e–g). Jensen and others (2000) also presented chains of beaded trails assigned to T. pedum that may be better assigned to T. vagans. The Jensen and others (2000) and Wilson and others (2012) specimens likely represent an intergradation between T. pedum and T. vagans.

Treptichnus vagans specimens are similar to Hormosiroidea canadensis Crimes & Anderson, 1985 and H. arumbera Walter, Elphinstone, & Heys, 1989. Uchman (1995) later transferred H. canadensis to Saerichnites Billings, 1866, arguing that the vertical-tube expression was inconsistent with the diagnosis and type ichnospecies of Hormosiroidea. Hormosiroidea Schaffer, 1928, is characterized as a horizontal chain of spheres or depressions connected by a central tube, whereas Saerichnites was established as a trackway of paired, parallel rows of alternating semicircular to subquadrate pits (Häntzschel, 1975). Crimes and Anderson (1985) considered the beads and depressions of H. canadensis to be expressions of a vertical meandering method or vertical shafts that were connected by a horizontal tube. Walter, Elphinstone, and Heys (1989) thought H. arumbera was constructed in the same manner as H. canadensis. Uchman (1995), however, interpreted Saerichnites as an interconnected, zigzag-branching burrow system, similar to Treptichnus. We disagree with the Uchman (1995) synonymy, and tentatively place H. canadensis and H. arumbera within Treptichnus vagans due to their beaded-chain morphology and the synonymization of Hormosiroidea under Halimedides Lorenz von Liburnau, 1902 (Uchman, 1998, 1999; Gaillard & Olivero, 2009).

Treptichnus vagans is also similar to “rosary-like structures” from the middle Cambrian Burgess Shale (Caron & others, 2010; Mángano, 2011) and linear Treptichnus bifurcus from the Lower Jurassic East Berlin Formation of Massachusetts (Getty & others, 2016). The Burgess Shale “rosary structures” are short to long, meandering to winding to zigzagging chains of small, beadlike mounds or pits with connecting tunnels and interpreted as chains of globular to spherical chambers used as agrichnia to farm bacteria (Mángano, 2011). Most Treptichnus vagans specimens lack tunnels connecting the beads. Some “rosary” chambers were filled with pyrite—which the T. vagans specimens lack—and were noted to support an agrichnial interpretation in dysoxic waters and nearanoxic sediments (Mángano, 2011). The “rosary structures” were also noted for their similarity to T. pollardi and its associated vertical shaft nodes (Jensen in Mángano, 2011) and are included in T. vagans. Specimens of linear T. bifurcus reported from the Lower Jurassic East Berlin Formation (Getty & others, 2016, fig. 4.5), described as “string of beads” and composed of linearly oriented burrow segments and swelled projection occurring end on end, are morphologically similar to the Burgess Shale rosary structures, Ptychoplasma, T. pollardi, and T. vagans. We, therefore, include the linear T. bifurcus specimens of Getty and others (2016) within T. vagans.

Material.—KUMIP 314121: one specimen (part and counterpart), Wellsville Mountains, Utah, USA.

Diagnosis.—Circular, convex mound (part) with broad, shallow depression near center.

Description.—Convex mound: 43.9–46.6 mm wide; 11.7 mm thick; depression is 2.8 mm deep. Elrathia? sp. trilobite mold on counterpart: 10.1 mm long, 7.2 mm wide; corresponds to dark gray ovoid-shaped area on part specimen.

Occurrence.—Gray, siliciclastic silty shale.

Associated ichnotaxa.—None.

Discussion.—The exact nature of this specimen is unknown but we propose several possible interpretations: (1) a body fossil and ichnofossil of an unknown cnidarian jellyfish (likely a scyphozoan) perhaps with and the Elrathia? sp. trilobite feeding off the remains of the jellyfish (i.e., Mortichnia and Praedichnia); (2) a resting trace of a suspension-feeding cnidarian, for instance, an upside-down jellyfish (Rhizostomeae, Cassiopeidae) or sea anemone; or (3) the nesting trace of an unknown tracemaker, similar to modern-day fish nests.

A cnidarian body fossil and ichnofossil interpretation is the most likely as there are reports of similar circular-shaped fossils interpreted as jellyfish body fossils (e.g., Hagadorn, Dott, & Damrov, 2002; Gaillard & others, 2006; Oosterink & Winkelhorst, 2013). Hagadorn, Dott, and Damrov (2002) and Gaillard and others (2006) illustrated jellyfish specimens with some of the internal morphology (e.g., gonads) and tentacles preserved, whereas other specimens only had concentric rings or slight deformation attributed to shrinkage and/or locomotive pulsation and localized downslope sliding, respectively. Oosterink and Winkelhorst (2013) specimens had concentric rings attributed to shrinkage and appeared to exhibit some internal morphology. The Spence Shale specimen lacks concentric rings to indicate pulsation, no deformation to indicate downslope sliding, or any discernible internal morphology. The central depression, however, may have been formed by the collapse of the jellyfish bell during decay. Trilobites are also known for being predators and/or scavengers of soft-bodied faunas (e.g., Jensen, 1990; Tarhan, Jensen, & Droser, 2011) and there is a report of a complex Rusophycus association that was interpreted as trilobites consuming possible jellyfish remains (Brandt & Rudkin, 2011). The close association of the jellyfish body impression and the Elrathia? sp. may represent predation or scavenging by the trilobite.

The second proposed interpretation of the mound is as a resting and/or suspension-feeding trace of an unknown species of upsidedown jellyfish (i.e., Cassiopeidae) or actinian (e.g., sea anemone). The upside-down jellyfish, Cassiopeia Perón & Lesueur, 1810, has a flat to concave, broad bell with tentacles extended upward to capture prey, and it commonly rests on the seafloor (Hummelinck, 1968; DeFelice, Eldridge, & Carlton, 2001; Schembri, Deidun, & Vella, 2010). The concave bell of Cassiopeia could possibly form a short, broad mound while resting on the sediment-water interface. An actinian tracemaker could also produce a similar shallow-mound form (e.g., Bergaueria sucta); however, the orientation of the specimen would be opposite of the current interpretation.

A third, proposed interpretation is that the mound is a nestlike excavation of an unknown tracemaker, possibly the Elrathia? sp. trilobite. Nestlike excavations of known and unknown tracemakers are not unheard of in ichnotaxonomy. Fenton and Fenton (1937d) established and interpreted Rusophycus jenningsi as a trilobite brooding nest. Ancient and modern fish produce simple to intricate, radially symmetric mounds or depressions (e.g., Piscichnus) to attract mates and spawn (e.g., Feibel, 1987; Hasiotis & others, 2012; Kawase, Okata, & Ito, 2013). The Elrathia? trilobite may have produced the mound in an attempt to attract a mate with whom to reproduce.