Paleocommunity research efforts have explored a multitude of faunal assemblages using a wide range of sampling and analytical methods to infer a paleoecological signal. Here, we derive six secondary datasets from a single stratigraphic series of faunal assemblages in the Finis Shale (Pennsylvanian) of Jacksboro, Texas, USA, using a variety of data categorization decisions (i.e., abundance versus calcified biomass, all taxa versus selected indicator taxa, and generic versus higher clade resolution). Biomass- and abundance-derived datasets were not significantly different in terms of evenness, Shannon's information index, or Simpson's diversity index. Using Bray-Curtis and nonmetric multidimensional scaling ordinations, with Sorenson and relative Sorenson distance measures, ordination axis scores of the six derived datasets were all significantly correlated with one another, suggesting little difference in their respective paleoecological signals. Three potential explanations for this consistent paleoecological signal, regardless of which data categorizations are employed, include: (1) the dominance of a few brachiopod taxa overwhelmingly influenced the community structure, (2) relatively constrained environmental conditions limited community variation, and (3) low variation in specimen size minimized potential differences among abundance and calcified biomass categorizations. We suggest that other datasets with greater diversities, greater evenness, or from a wider range of paleoenvironments might not show this consistency. Thus, to the degree possible and appropriate, paleoecological investigators should test the effects of these data categorization decisions on a paleoecological signal, regardless of the analytical method employed.

Many carbonate sections are characterized by monotonous successions that mask subtle changes in paleoenvironmental parameters. Foraminiferal populations, however, are more sensitive to environmental parameters and commonly reflect these subtle changes. The accuracy of paleoenvironmental interpretations based on foraminiferal assemblages depends on the precise delineation and interpretation of abundance biozones (ABs). Samples rich in foraminifera were taken from four outcrops (OC1–OC4, oldest to youngest) of the Mayo limestone bioherm (Tamana Formation) that comprised 6–8 limestone-marl alternations each. Bottom-up SHE Analysis for Biozone Identification (SHEBI) indicated the samples to be from seven ABs (AB1–AB7). The percentage of the foraminiferal assemblage as planktonic specimens (%P) ranged from 5%–25% and was generally lower in AB1, AB3, AB5, and AB7 than in intervening biozones. This indicates deposition at shallow- to mid-neritic paleodepths (∼20–55 m) during a series of transgressions and regressions. Per sample (point) diversities, measured using the information function H, ranged from 1.67 to 2.86. Total within-AB diversities (α diversities), were calculated from the final value of H and expressed as the effective number of species S_E [ = e^H]; these ranged from 7.8 to 18.4. Changes in diversity across AB boundaries (β diversities) were calculated using the percentage change in S_E, and ranged from −44% to 137%. Not all β diversities were significant, indicating that paleodepth was not the only control on α diversity. Fluctuations in the percentage abundances of Elphidium spp., Pseudononion atlanticum, and Amphistegina sp. show that changes in the organic matter flux also exerted some control, being lowest in the Amphistegina-rich AB3.

The relationship between predator and prey is a persistent theme in marine paleontology. Herein we focus on the decapod Crustacea, the shrimps, lobsters, and crabs, and their role as predators on the Mollusca through geologic time. Five major means by which decapods crush shells or eat shelled prey might be recorded in the body-fossil record, as they require specialization of the appendages. These include use of (1) heterochelous first pereiopods, (2) molariform teeth on the fingers of the chelae, (3) a curved proximal tooth on the movable finger of the chela, (4) calcified mandibles, and (5) flattened pereiopods (walking legs). Decapods have had adaptations for durophagous predation on mollusks since the early Triassic. Durophagous adaptations had appeared among multiple clades by the Late Cretaceous. The myriad means by which decapods prey upon Mollusca, and the multiple uses for which pereiopods and other appendages are adapted, suggests that predation studies should incorporate more decapod types and more types of predation when examining predation as a driver of evolution.

Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was used to determine rare earth element (REE) content of 76 fossil bones collected from the Upper Cretaceous (Campanian) Two Medicine (TMF) and Judith River (JRF) Formations of Montana. REE content is distinctive at the formation scale, with TMF samples exhibiting generally higher overall REE content and greater variability in REE enrichment than JRF samples. Moreover, JRF bones exhibit relative enrichment in heavy REE, whereas TMF bones span heavy and light enrichment fields in roughly equal proportions. TMF bones are also characterized by more negative Ce anomalies and greater U enrichment than JRF bones, which is consistent with more oxidizing diagenetic conditions in the TMF. Bonebeds in both formations show general consistency in REE content, with no indication of spatial or temporal mixing within sites. Previous studies, however, suggest that the bonebeds in question are attritional assemblages that accumulated over considerable time spans. The absence of geochemical evidence for mixing is consistent with diagenesis transpiring in settings that remained chemically and hydrologically stable during recrystallization. Lithology-related patterns in REE content were also compared, and TMF bones recovered from fluvial sandstones show relative enrichment in heavy REE when compared with bones recovered from fine-grained floodplain deposits. In contrast, JRF bones, regardless of lithologic context (sandstone versus mudstone), exhibit similar patterns of REE uptake. This result is consistent with previous reconstructions that suggest that channel-hosted microfossil bonebeds of the JRF developed via the reworking of preexisting concentrations embedded in the interfluve. Geochemical data further indicate that reworked elements were potentially delivered to channels in a recrystallized condition, which is consistent with rapid adsorption of REE postmortem.

Only the small (2.0 ± 0.1 cm) orthide brachiopod Rhipidomella in the Middle Devonian Dundee Formation exposed at Whitehouse Quarry, Ohio, preserves evidence of interactions with endoskeletobionts and predators (39.6%, n  =  48), as opposed to the slightly larger atrypides, spiriferides, and stropheodonts (n  =  245). All traces of predation and boring by other organisms are lacking on such larger brachiopods as strophomenides and spiriferides, which are more often encrusted in Devonian localities of North America—the Silica Shale of Ohio, Hamilton Group of New York, and Cedar Valley Limestone of Iowa. Punctate shells of Rhipidomella preserve interactions with endoskeletobionts and predators, phenomena less common for punctate brachiopods. All traces on Rhipidomella were preserved as endoskeletobionts; if calcified encrusters were present, they likely were lost postmortem. Several Rhipidomella individuals bear partially repaired grooves from parasitic interactions with sinuous, boring organisms, attributed to ctenostome bryozoans. These parasites bored into the shell along the commissure, likely benefiting from the inhalant and exhalant currents produced by the brachiopod, and in some cases, expanded away from the commissure following the host's death. The straight, U-shaped borings in one Rhipidomella specimen with boreholes are similar in morphology to Caulostrepsis traces that occurred with their tubes opening along the margins of a modern brachiopod. Other endoskeletobiont traces likely formed on the postmortem shells of Rhipidomella. Predation repair scars are present on two specimens, indicating the presence of predators and the survival of some Rhipidomella individuals from durophagy. No specimens contain evidence of drilling predators.

The spheroidal edrioasteroid echinoderm Totiglobus, preserved in the middle Cambrian Chisholm Shale of eastern Nevada, was one of many interesting morphologies to develop during the period of rapid evolutionary diversification in the early and middle Cambrian. To understand more about how the unusual morphology of Totiglobus evolved, a detailed examination of fossil specimens and the strata in which they are preserved was performed. A total of 263 specimens were examined and placed into taphonomic categories based on their preserved orientation relative to the seafloor. Seventy-two well-preserved specimens were used for statistical analysis. Of these, 49% were preserved with the aboral surface down. The preference for preservation in this category, with the aboral surface (which contains a suctorial attachment disc) oriented directly on top of the sediment, was statistically significant (p < 0.025). These data support the hypothesis that Totiglobus lived attached to the seafloor through suction. Rock samples were also collected from seven localities in the Chisholm Shale and the bioturbation levels were determined using the ichnofabric index (ii) method. A total of 48 samples, comprising 4.09 m of strata, were collected and x-radiographed. Ichnofabric index (ii) data recorded from these rocks revealed extremely low bioturbation levels (∼ii  =  1) with no mixed layer development (1.01 average ii). These results likewise support the sediment attachment hypothesis for Totiglobus. This study indicates that some unusual Cambrian morphologies, including that of Totiglobus, evolved partly in response to the presence of nonactualistic seafloor conditions and are therefore not simply early evolutionary experiments.

Freshwater bivalves with exceptionally well-preserved gill supports occur in the Upper Triassic (Carnian) mudrocks at the Krasiejów claypit in southern Poland. X-ray EDS (energy dispersion system) spectrometer analysis reveals that the originally chitinous gill supports are secondarily mineralized in calcium phosphate. Co-occurrence of mineralized bacteria suggests they were involved in the phosphatization process. Actualistic taphonomic experiments using the freshwater mussel Unio tumidus suggest that mineralization was completed between 50 to 150 hours after the death of the fossil bivalves.