Different morphotypes of vertically embedded ammonoid shells are abundant in the 1-km-thick deposits of the Santa Marta Formation, Antarctica, that record the evolution of a deep-water delta system. Vertical shells deposited in water depths well below the theoretical limit imposed by hydrodynamic and hydrostatic analyses are preserved as isolated specimens, dense concentrations associated with abundant wood fragments (pod preservation), or as dense concentrations inside and around large ammonites (sheltered preservation). Taphonomic analysis indicates that (1) vertical shell orientation is primary; (2) postburial reworking was minimum or absent, as indicated by consistent shell orientation parallel to regional paleocurrents and complete preservation of fragile shells with phragmocones filled with drusy calcite; and (3) vertical orientation is not biased towards a preferred morphotype. Rapid sedimentation, including deposition from high- and low-density currents, tempestites, and weak bottom currents carrying a dense suspension of ammonoid shells and wood fragments, was one of the main factors controlling the vertical preservation below the limits imposed by theoretical hydrostatic analyses. Another important factor was the plugging of the siphuncular tube with clay particles during transportation. The clay plug was stiff enough to resist the ambient hydrostatic pressure, avoiding or delaying the waterlogging of the phragmocone.

The Virginia Solite Quarry occurrence of exceptionally abundant and uniquely preserved specimens of the tetrapod Tanytrachelos ahynis offers an opportunity to quantify multiple aspects of vertebrate taphonomy. Presence or absence of 128 skeletal elements and of 136 skeletal variables were recorded for 99 specimens from two distinct layers within the quarry—lake cycles 2 and 16. Anatomical completeness, or the percent of bones and variables present in a specimen, is low in spite of protection given by anoxic bottom waters from predators and scavengers; the median specimen preserves 14.5% of bones and 11.8% of measured variables. Specimen size, soft-tissue preservation, and postexhumation weathering have no significant effect on specimen completeness; soft-tissue preservation has a significant impact on degree of articulation. Tanytrachelos specimens with heterotopic bones are not significantly more complete than those lacking such bones; this quantitative pattern reinforces independent qualitative taphonomic evidence supporting a biological rather than taphonomic interpretation of the two morphotypes. Lake cycles 2 and 16 differ significantly in terms of articulation and anatomical completeness when anatomical specimen completeness has been corrected for postdepositional faulting. Preservation frequency of bones and variables, or the percent of specimens in which a bone or variable is present, varies greatly but is low with substantial removal of smaller skeletal elements and preferential preservation of such hindlimb elements as femora. Low anatomical specimen completeness and positive correlation between bone size and frequency of preservation both indicate specimen disturbance by minor hydraulic currents. Taphonomic patterns support a low-to-moderate-depth depositional environment, which is shallower than the original reconstruction.

The methods by which fossils are extracted from sediments can alter their observed size-frequency distributions, which can in turn alter observed paleoecologic patterns. Building on previous work, this study uses virtual sieving (i.e., replicated via subsampling on a computer) to test the effects of size filtering on the apparent ecologic composition of a database of Miocene mollusks in which the size of every specimen was measured. When simulated mesh sizes varied by nearly an order of magnitude (2–10 mm), the apparent relative abundances of tiering, motility, and feeding categories varied substantially in some individual bulk samples. Not surprisingly, the extent to which variations in mesh size affected the ecologic proportions of a sample depended in part on its size-frequency distribution. If the goal is to characterize the ecology of adult assemblages, the chosen mesh size should not be so small that juveniles dominate the results or so large that a majority of specimens are excluded. For many molluscan assemblages, 2–4 mm should often be appropriate. For preexisting data sets composed of heterogeneously collected data, there is a positive result: averaging samples together to produce a mean view of ecologic composition tends to remove the more egregious effects of the size-filtering bias. Thus, comparisons of the ecologic composition of single samples may be sensitive to mesh-size effects, but comparisons of regional or global faunas are likely more robust, and variations in size filtering may not be an obstacle to large-scale, secular comparisons of ecospace use. Measuring ecologic importance using biomass instead of abundance also reduced the effects of the mesh-size bias by reducing the influence of small-bodied individuals on ecologic proportions.

The purpose of this paper is to study the taphonomy of fossil flies (Diptera) preserved in the lacustrine deposits of the Florissant Fossil Beds (late Eocene), Colorado, United States. Three hundred and twenty-six fossil Diptera were examined, collected from a nearshore (n = 215) and an offshore (n = 111) site. The degree to which a specimen's preservation quality correlated with the ability to identify the specimen to various taxonomic levels and whether specimen size, orientation, or disarticulation had an effect on a preservation quality were evaluated. Also examined was the influence of depositional environment on these variables. Preservation quality was found to be important for identification to species level, but specimens of low preservation quality were still identifiable to the family and genus levels. Specimen size, orientation, and disarticulation were not correlated with the identifiability of a specimen. There was no significant difference in the orientation, disarticulation, or preservation quality of specimens found in the nearshore and offshore sites. There was a significant difference in the size of specimens preserved at each site, with larger specimens being found offshore. More specimens were found in the offshore site, but species richness did not differ between the two sites. Composition of taxa did differ depending on the site. These results demonstrate the importance of collecting all specimens, as even poor quality and disarticulated specimens are identifiable and useful in studies of insect ecology and evolution. In addition, depositional environments should be documented, as size sorting can bias the taxonomic composition of assemblages.

Numerous paleocommunity studies of marine ecosystems have demonstrated that water depth was the primary factor structuring paleocommunities. In contrast, many ecological studies find other factors play a greater role in delineating communities; this difference in results may be owing to the spatiotemporal scale at which the study is performed. To explore this hypothesis, the present study examines a set of Imperial Formation (Pliocene, California) paleocommunities at a scale potentially fine enough to exclude depth as a control over the communities, thus facilitating recognition of fine-scale ecological and environmental processes operating at this scale. Twenty-six taxa from 21 samples were collected in situ from an 8.5-m-thick interval within a 0.32 km² area. Cluster, Bray-Curtis (polar) ordination, and detrended correspondence analyses were used to infer community structure. Cluster and ordination analyses produced similar results independent of choice of distance measure. To test whether depth would be the primary control, even at fine scales, the scores from the first ordination axis for each taxon were compared with their modern mean depth; no strong correlation exists between depth and ordination scores. Cluster and ordination results indicate that life mode (as determined by modern relatives) and to a lesser extent, grain size, were the primary factors influencing paleocommunity structure at this scale. Bivalve taxa were grouped by life mode: quasi-infaunal, shallow-burrowing infaunal, byssate, and cemented. Relative to paleoecological studies conducted on much broader spatiotemporal scales, this study highlights the potential utility of embedding fine-scale studies within broader-scale studies to capture and investigate additional sources of ecological and environmental variation.

Oxygen and carbon isotope ratios were measured on belemnites, planktonic foraminifera, and benthic foraminifera collected from Late Cretaceous sediments on Seymour Island, Antarctic Peninsula, to compare the relative depth habitats of these organisms and to provide insight on temperature seasonality at high southern latitudes near the end of the Cretaceous. Average δ¹⁸O and δ¹³C values of the belemnite Dimitobelus seymouriensis overlap with those of benthic foraminifera; these values are significantly different (p < 0.01) from isotopic compositions recorded by planktonic foraminifera. This comparison shows that D. seymouriensis likely inhabited waters below the surface summer mixed layer of the outer shelf. These results suggest that average δ¹⁸O of D. seymouriensis is a good indicator of intermediate-to-deep-shelf water conditions, which in this locality is a good approximation for pelagic water temperatures in the Southern Ocean. Measurements of δ¹⁸O on high-resolution samples across belemnite growth bands indicate that annual temperature variability of sub-mixed-layer neritic water along the Antarctic coastline was 5°C on average with a mean annual temperature of 6°C.

The Mother's Day Quarry, in the lower part of the Upper Jurassic Morrison Formation of south-central Montana, contains a low-diversity assemblage dominated by immature diplodocoid sauropods. The sauropod bones lie within a ∼3-m-thick, massive, sandy siltstone containing scattered pebbles and carbonate nodules. Clay rip-up clasts indicate a high-energy depositional environment, and high-angle bone orientations are commensurate with a combination of the inferred high-energy burial event and postburial trampling of the assemblage. Since the Morrison Formation records deposition in an alluvial plain setting characterized by little topographic relief, heavy rainfall likely triggered the high-density flow event. Taphonomic analysis shows no indication that the Mother's Day assemblage was transported far by the entombing flow, though many elements may have been reworked. There is no statistically significant orientation of elongate elements and little apparent evidence of hydraulic sorting or transport damage. Remnants of soft tissue recovered from the quarry and the semiarticulated state of many of the bones demonstrate that the sauropod carcasses were buried a relatively short time after death. The cause of death of the sauropods is largely speculative; it is thought to have been related to drought based on the juvenile-dominated age profile of the assemblage and the inferred sequence of limb disarticulation. Comparison with other sauropod-dominated assemblages reveals that burial rates have little influence on the preservation of sauropod remains. Low-transport potential of sauropod bones implies that the sauropod component of dinosaurian assemblages should nearly always represent faunal elements derived from environments proximal to the site of deposition.

Fossil leaves in the middle Miocene Cucaracha Formation along the Panama Canal are 10–15 cm long, thick, and entire-margined; fossil pollen is also dicot dominated, as expected for wet tropical forests. Fossil woods include palms and ring-porous dicots, with smooth bark as is found in weakly seasonal tropical climates. In contrast, late Hemingfordian to early Barstovian mammals of the Cucaracha Formation are the same as those found in Nebraska, Kansas, and Florida, where climate was drier and cooler and vegetation more open. Cucaracha paleosols reconcile these differences as evidence of a mosaic of swamps to mangal (mangrove forests) preserving plants and dry uplands preserving mammals. A dozen pedotypes represent as many vegetation types, including mangrove, fresh-water and marine-influenced swamp, early successional riparian woodland, colonizing forest, dry tropical forest, and woodland. Many paleosols have calcareous nodules, and some have pedogenic barite nodules. Depth to carbonate and paleosol thickness with carbonate indicate mean annual precipitation of 573–916 ± 147 mm and mean annual range of precipitation of 27–65 ± 22 mm. Chemical analyses of paleosol Bt horizons confirm mean annual precipitation of 296–1142 mm and mean annual temperature of 15–16 ± 4.4°C. Low precipitation and temperature estimates imply a rain shadow from a high (1400–4000 m) volcanic mountain range to the west, with continuous land connection to allow immigration of mammals from North America. Partial enclosure of the Caribbean Sea by a mountainous Panama peninsula, as well as by Antillean arcs, initiated high Caribbean marine temperature and salinity well before Pliocene isthmian closure.

Free-living clusters of barnacles are described as nucleations around shell fragments of Ensis directus. The bivalve E. directus is an invader in European seas that exhibits mass mortalities, during which the animals creep partly out of the sediment. Barnacles can then settle on the inside and the outside of the posterior part of these empty, articulated, semi–in situ shells. This posterior, encrusted portion apparently became separated from the remainder of the valve, enabling the barnacles to continue life as a free-living balanulith.

The Tlayúa Quarry, sometimes referred to as the Mexican Solnhofen, is one of the most important fossil localities in Mexico, with fishes making up 70%–80% of the macrofossils. White cryptocrystalline hydroxyapatite patches within many specimens reveal details of muscles, gills, digestive tract, and stomach contents under the scanning electronic microscope. This is the first record of soft-tissue preservation of this kind in Mesozoic fishes from North America. The association of terrestrial, freshwater, and marine organisms, including shallow marine foraminifera, together with abundant ooids and isotopic evidence of fresh water higher in the sequence, favor a shallow, restricted-marine paleoenvironment.

Intricate morphology, combined with relatively soft and soluble calcite mineralogy, make foraminifera tests sensitive indicators of grain abrasion during transport in beach and coastal dune systems. Here, the extent of abrasion and dissolution of foraminifera tests is used to elucidate the relative ages and transport paths of sand from the Sixteen Mile Beach and 24-km-long Yzerfontein-Geelbek Holocene dune cordon on the west coast of southern Africa, located 80 km north of Cape Town. Foraminifera tests collected in rocky pools along the beach are well preserved with complete or nearly complete tests. Foraminifera tests recovered from adjacent beach sands show incipient signs of abrasion and are fragmented moderately and abraded from transport along the shoreface. Wind-blown foraminifera tests along the Yzerfontein-Geelbek active dune cordon show increasing signs of abrasion, corroded surfaces, and partly dissolved walls up to 18 km from the beach source. Between 18 km and 24 km from the beach source, most biogenic calcareous grains— shell fragments and foraminifera tests—in dune sand with an estimated maximum age of 4,500 years have been destroyed by physical and chemical weathering.

A Laojieella specimen of the Lower Cambrian Chengjiang Lagerstätte in Yunnan Province, southern China, contains a tubular organism inside its digestive tract. The gut content appears to resemble Archotuba conoidalis, a sessile animal generally regarded as being closely related to cnidarians. This example demonstrates that Laojieella might be a scavenger. Reasons for the extreme paucity of recognizable remains in gut contents are discussed. Such fossils offer new insights into the reconstruction of the complex food web of the benthic community of the Chengjiang fauna.