The genus Falsolikanella, introduced by Granier (1987), was based on the basal Cretaceous species Likanella campanensis Azéma and Jaffrezo (1972) and assigned to the tribe Diploporeae (Pia, 1920) emend. Güvenc, 1979 within the green alga order Dasycladales. Later, other species were assigned to Falsolikanella. Sections of the type specimens of Likanella campanensis are reviewed. They show that in this species, the arrangement of the laterals is not metaspondyl, but typical of the genus Actinoporella (Gümbel in Alth, 1882) emend Conrad, Praturlon, and Radoičić, 1974, with coronae arising from a single primary lateral. Therefore, the species is assigned to the genus Actinoporella within the tribe Acetabularieae Decaisne, 1842, family Polyphysaceae Kützing, 1843, and the generic attribution of other species previously assigned to Falsolikanella is discussed.

Vase-shaped microfossils (VSMs) occur in dolostone clasts within conglomerates, breccias, and diamictites of the Neoproterozoic Urucum Formation, Jacadigo Group, southwest Brazil. Although their taphonomic history is distinct from those of other VSM assemblages, morphometric comparison of Urucum fossils with five others described previously from North America and Europe show that two of the Urucum species—the long-necked Limeta lageniformis Morais, Fairchild, and Lahr in Morais et al., 2017 and the funnel-necked Palaeoamphora urucumenseMorais et al., 2017—occur in the Kwagunt and Callison Lake assemblages, as does Pakupaku kabinRiedman, Porter, and Calver, 2017 recently described from the Togari Group, Tasmania. Obelix rootsii (Cohen, Irvine, and Strauss, 2017) new combination, previously known only from the Callison Lake Formation, is documented here from the Kwagunt Formation. In addition, Trigonocyrillium horodyskii (Bloeser, 1985) and Bonniea dacrucharesPorter, Meisterfeld, and Knoll, 2003, first described from the Kwagunt assemblage, have now been found in the Urucum Formation. In light of this survey, 16 of the 18 validly described VSM species are now known to occur in the Kwagunt Formation and 13 in the Callison Lake Formation, with 12 of them shared by both formations. The fact that the Urucum VSM assemblage exhibits six of seven species in common with the Kwagunt Formation—L. lageniformis, P. urucumense, Cycliocyrillium simplexPorter, Meisterfeld, and Knoll, 2003, C. torquataPorter, Meisterfeld, and Knoll, 2003, B. dacrucharesPorter, Meisterfeld, and Knoll, 2003, and T. horodyskii (Bloeser, 1985)—and all but the last of these in common with the Callison Lake Formation supports correlation of these three assemblages and indicates that the source of the fossiliferous clasts within the Urucum Formation may well have been a now-vanished late Tonian carbonate platform.

Thirteen bryozoan species are described from the Brewer Dock (Hickory Corners) Member of the Reynales Formation (lower Silurian, Aeronian) at the locality Hickory Corners in western New York, USA. Three species are new: trepostomes Homotrypa niagarensis n. sp. and Leioclema adsuetum n. sp. and the rhabdomesine cryptostome Moyerella parva n. sp. Only one species, Hennigopora aptaPerry and Hattin, 1960, developed obligatory encrusting colonies whereas the others produced erect ramose colonies of various thicknesses and shapes: cylindrical, branched, and lenticular. Bryozoans display high abundance and richness within the rock. This fauna is characteristic of a moderately agitated environment with a stable substrate. The identified species reveal paleobiogeographic connections to other Silurian localities of New York as well as Ohio and Indiana (USA) and Anticosti (Canada).

Exceptional sub-micrometer details of shell microstructure are preserved in phosphatic micro-steinkerns representing several phyla from shell beds of the Upper Ordovician of the Cincinnati Arch region, USA. These fossils provide the most detailed record of Ordovician mollusk shell microstructures, as well as exceptional details on the earliest cases of undisputed nacre. The trend towards nacre in the Mollusca is one aspect of the surge in escalation between mollusks and their predators during the Great Ordovician Biodiversification Event.

Naticid taxonomy is in a state of flux owing to non-descript shell morphology and frequent convergence. Inadequate preservation of naticid body fossils has further complicated the matter in determining the true affinity and the exact time of origin of the clade. As a result, a plethora of classificatory schemes of naticid phylogeny and times of origin has been proposed. In many previous studies, true naticid affinities of fossils have been sought based on single or a few morphological characters, which are susceptible to poor preservation. In the present paper, we have attempted a holistic reappraisal of naticid taxonomy based on an extensive database of shell morphological characters and identified many distinct family- and subfamily-specific characters that survived fossilization. This approach has enabled us to identify three new naticid species from the Late Jurassic horizons of Kutch, India, thus extending back the time of origin of the family Naticidae by 30 Ma.

Analysis of character matrix data reveals that the present species—Gyrodes mahalanobisi new species, Euspira jhuraensis new species, and Euspira lakhaparensis new species—belong to two subfamilies, Gyrodinae and Polinicinae. The occurrence of typical naticid drill holes on various coeval gastropod and bivalve taxa along with these body fossils provides strong supporting evidence for the naticid affinity of these forms.

Since the genus Retrotapes was erected, some authors have favored or opposed its validity, or argued about the assignment of the extant species R. exalbidus and R. lenticularis to Retrotapes. Some authors synonymized Retrotapes with the Miocene genus Frigichione, and others with the extant genus Eurhomalea to which most of the species that belong to Retrotapes were previously assigned. In the present contribution, a phylogenetic analysis of the genus is performed to test these controversies. In addition, a systematic revision of the Chilean species of the genus is performed to complete the analysis of Retrotapes taxa from Patagonia and Antarctica started by previous authors. This study demonstrates that Retrotapes is a monophyletic genus, which is not closely related to Frigichione or Eurhomalea. Instead, Retrotapes is closely related to some Austral taxa from Kerguelen Island (Paleomarcia), New Zealand (Atamarcia), and Australia (Katelysia), a relationship previously unknown. Besides, the extant species R. lenticularis and R. exalbidus belong to Retrotapes and were recovered as part of a clade closely related to the type species of the genus, R. ninfasiensis (Miocene, Patagonia). Retrotapes is reported in Chile beginning in the late Eocene, where it was represented by R. difficilis n. comb., which is a taxon that resembles some Eocene species of the same genus from Antarctica. In the late Oligocene–early Miocene, it was represented by R. navidadis and later in the Pliocene by three species: the fossil R. fuenzalidae and the two extant ones.

LytohoplitesSpath, 1925 is a late Tithonian–?early Berriasian ammonoid genus with a southern perigondwanean distribution. Two Lytohoplites species, L. burckhardti (Mayer-Eymar in Burckhardt, 1900) (type species) and L. vetustoides (Burckhardt, 1903), were originally described from carbonate successions of the Vaca Muerta Formation, Neuquén Basin, Argentina. Nevertheless, the holotype of L. burckhardti consisted of a single incomplete specimen that is currently missing. This situation compelled the search for new Lytohoplites specimens in Argentina and the selection of a neotype for L. burckardti. New Lytohoplites representatives were obtained through bed-by-bed collections performed at five localities in the Neuquén Basin. In addition to the taxonomic revision of the Lytohoplites species occurring in the basin, a paleobiological approach was preferred to conduct a paleontological analysis of L. burckhardti, including a description of its ontogeny, probable sexual dimorphism, and spectrum of intraspecific variability. Results of the qualitative and quantitative analyses supported the homogeneity of L. burckhardti as a taxonomic unit, thus implying that L. vetustoides should be considered its synonym. Lytohoplites in the Neuquén Basin is restricted to beds assigned to the Andean Substeueroceras koeneni Assemblage Zone (upper Tithonian–lower Berriasian), and not to the Andean Corongoceras alternans Assemblage Zone (upper Tithonian). Furthermore, the paleobiogeographic distribution of Lytohoplites around southern Gondwana and the herein reported occurrence of L. subcylindricusCollignon, 1962, otherwise only known from Madagascar, lend support to the existence of a functional trans-Gondawana seaway at least since the upper Tithonian.

Genus Neosinocythere is described from the upper Miocene Itahana Formation in Central Japan, documenting the first record from Japan. The Neosinocythere species were discovered in gravity-flow sediments that were deposited below a depth of 84.9 m with a paleo-summer bottom temperature of 23.7°C and a paleo-winter bottom temperature of 14.1°C, based on a modern analog technique using the ostracode assemblage. Paleobiogeographical and paleoenvironmental analyses indicate that Neosinocythere appeared around the southeastern coast of the Eurasian continent, extended distribution in the northern coast of the Eurasian continent before migrating southward along the coast of the Eurasian continent as global temperatures decreased. The high-diversity area shifted from high latitudes to low latitudes.

The phylogenetic relationships of Paleozoic blastozoan echinoderms are poorly understood and many of the traditionally ascribed groups are likely polyphyletic. Diploporitans, those blastozoans with double pore (diplopore) respiratory structures, have never been placed within a rigorous phylogenetic framework, and their highly variable morphologies suggest that they do not represent a natural clade. A maximum parsimony phylogenetic analysis, spanning a wide range of diploporitan and related taxa, indicates that diplopore-bearing blastozoans are a polyphyletic grouping and, consequently, that diplopore respiratory structures have evolved more than once within the echinoderms. Constraint analyses indicate that a single diplopore-bearing clade bearing the traditionally defined Glyptosphaeritida, Sphaeronitida, Asteroblastida is less parsimonious than multiple diplopore-bearing clades inferred by the unconstrained analysis.

Newly discovered, relatively well-preserved specimens of Cholaster whitei n. sp. (Ophiuroidea, Echinodermata) are described from a small area of extensive outcrop of the Bangor Limestone (Mississippian, Chesterian) exposed on the edge of Cedar Creek Reservoir in northern Alabama, USA. The only other known species of the genus, C. peculiaris Worthen and Miller, is based on a single specimen exposed in dorsal aspect and collected from strata of similar age from southwestern Illinois. Incomplete preservation of the single C. peculiaris specimen limits comparisons, but differences between the two occurrences support separation at the species level.

Skeletal remains of both asteroids and ophiuroids are first recognized from Early Ordovician sediments, and representatives of the two classes have retained plesiomorphies or converged morphologically since that time, thereby suggesting important evolutionary potentials and limitations. Cholaster is asteroid-like and unusual among ophiuroids in that the arms are comparatively broad and strap-like, and lateral ossicles are similar to asteroid adambulacrals and marginals, whereas the “vertebrae” (i.e., fused axial pair) and oral frame configurations of C. whitei n. sp. are typical of the Ophiuroidea. The oral frame of C. peculiaris is unknown.

A poorly preserved specimen of the asteroid Delicaster? also was recovered from nearby strata associated with the C. whitei n. sp.

A rich echinoid fauna within the middle Miocene carbonate sedimentary succession cropping out along the coast between Santa Caterina di Pittinuri and S'Archittu (central-western Sardinia) allows the comparison of faunal gradients and preservation potentials from both hard and soft substrata. Three echinoid assemblages are recognized. Faunal composition, as well as taphonomic and sedimentological features and functional morphological interpretation of the echinoid test indicate an outer sublittoral setting. Assemblage 1 represents a highly structured environment within the photic zone, with mobile substrata occupied by infaunal irregular echinoids, mainly spatangoids, and localized hard substrata, provided by rhodolith beds, with epibenthic regular echinoids represented by the co-occurrence of the diadematid DiademaGray, 1825 and the toxopneustids TripneustesL. Agassiz, 1841 and SchizechinusPomel, 1869. Assemblage 2 shows a higher diversity of irregular echinoids, dominated by the clypeasteroids Echinocyamusvan Phelsum, 1774 and ClypeasterLamarck, 1801 and different spatangoids, with the minute trigonocidarid GenocidarisA. Agassiz, 1869 among regular echinoids. This assemblage points to a soft-bottom environment with moderate water-energy conditions, periodically affected by storms. A low-diversity echinoid fauna in Assemblage 3, dominated by the spatangoids BrissopsisL. Agassiz, 1840 and OvaGray, 1825, documents a deeper, soft-bottom environment, possibly below storm-wave base. These results indicate that the diversity of echinoid faunas originating in sublittoral environments is related to: (1) the presence of both soft and hard substrata, (2) differential preservation potentials of the various echinoid taxa, (3) intense bioturbation, and (4) sediment deposition by sporadic storm events.

The Neognathodus Index (NI) is developed as a primary biostratigraphic indicator for the Desmoinesian Series of the Illinois Basin in Indiana, Illinois, and Kentucky. It is based on the gradual evolutionary morphotypic variations of P1 elements of named species of NeognathodusDunn, 1970. The NI analyses and zonations presented herein are constructed from 472 productive conodont samples from 105 different localities. NIs for the Illinois Basin show morphologic drift in Indiana from the Perth Limestone Member of the Staunton Formation (NI = 2.03) to the Velpen Limestone and Mecca Quarry Shale members of the Linton Formation (NI = 5.04) followed by stability through the Alum Cave (NI = 4.83). Further morphologic drift then occurred through the Providence Limestone Member of the Dugger Formation (NI = 5.43) and continued through the West Franklin Limestone Member of the Shelburn Formation (NI = 6.32) until the extinction of Neognathodus at the end of Desmoinesian. The patterns of drift and stability translate to Neognathodus biozones and are supported by Kolmogorov-Smirnov tests of standardized Neognathodus morphotype distributions. Localized NI variations are due to morphologic shifts and differential evolution in response to localized environmental conditions. Examination of the NI differences in the states of Illinois, Kentucky, and Indiana reflect similar morphologic simplification of the P1 element from Perth to Velpen and Mecca Quarry in Indiana (NI = 2.03–5.04) and from Seville to Brereton in Illinois and Kentucky (NI = 2.80–5.00). Post-Brereton in Illinois and Kentucky (NI = 5.00–5.65) and post-Providence in Indiana (NI = 5.43–6.32) saw progressive P1 simplification, but it was much more pronounced in Indiana.

Peligrochelys walshae is a meiolaniform turtle originally described based on four specimens represented by cranial remains found in the classic locality of Punta Peligro (Chubut, Argentina) in outcrops of the Salamanca Formation (Danian). Recent field work in the vicinity of Punta Peligro resulted in the discovery of almost 30 new specimens, represented by cranial and postcranial remains that can be assigned to P. walshae. In this contribution, we provide a detailed anatomical description of the new specimens, provide an emended diagnosis for the species, and explore its phylogenetic relationships based on all anatomical data available for the species. The new specimens bring valuable information about the anatomy of the skull and postcranium of P. walshae as well as for meiolaniforms in general. The 3D preservation of the skull bones allows us to provide a 3D reconstruction using novel techniques. The updated phylogenetic analysis confirms that P. walshae is part of the clade Meiolaniformes, which spans from the Early Cretaceous until the Holocene and contains the giant, horned turtles (Meiolaniidae). This phylogenetic analysis reinforces the previous hypothesis that the clade Meiolaniformes is dominated by Gondwanan taxa, but also includes some Laurasian representatives. Alternate phylogenetic positions of taxa included in Meiolaniformes in this analysis were tested using the Templeton test. The lineage leading to Peligrochelys walshae is the only meiolaniform non-meiolaniid lineage to have survived the K-Pg mass extinction; its study provides valuable information to evaluate the effects of the K-Pg extinction in turtles.

Barrande erected the genus Aristocystites, type A. bohemicus Barrande, in 1887. He listed other questionable species, including “A.? subcylindricus var. de bohemicus.” Aristocystites subcylindricus has not been accepted apart from Bather who in 1919 designated a type specimen and made it the type species of the new genus Hippocystis. No specimens available to Barrande or Bather preserved the oral area necessary to characterize Hippocystis or A. subcylindricus. Specimen 436969A, in the United States National Museum of Natural History is a more complete specimen of A. subcylindricus and preserves the oral area. This shows that A. subcylindricus is a valid species, but has two ambulacral facets, a character unique to the genus Aristocystites. Aristocystites subcylindricus has tumid plates with obvious sutures, a rounded thecal base, and a gonopore surrounded by three plates. Aristocystites bohemicus has smooth plates, an obvious attachment scar aborally and a gonopore within a single plate. Both species have occasional horseshoe-shaped diplopores.