Simulating the formation of herbivore tooth death assemblages to improve expectations for paleoenvironmental reconstruction from intra-tooth isotopic analysis

The rate of taphonomic loss in modern benthic habitats: How much of the potentially preservable community is preserved?

Integrated taphonomy of an avian death assemblage in marine sediments from the late Pliocene of Florida

Paleoecological reconstruction relies on accurately determining the taphonomic origin of fossil deposits. Predation is a common mechanism by which skeletal remains become concentrated over time, leading to the formation of modern and fossil prey death assemblages. Skeletal element representation and breakage patterns within such death assemblages can be used to infer the identity of the responsible predator. However, assemblage-level metrics cannot be used to infer if a single fossil specimen is predator-derived. Microscopic digestive etching on individual bones can also indicate past predation events because acidic gastric fluids create distinctive micrometer-scale fissures in cortical bone. Here we establish a quantitative approach to predator identification from small mammal prey remains using microscopic digestive damage patterns. To do this, we collected mandibles from rodents digested by 13 predator species from local wildlife rehabilitation centers, and imaged them using an FEI Quanta 200 SEM. Results indicate that bones exposed to gastric fluids show clear digestive fissures, and that owl-digested specimens can be readily distinguished from specimens that were digested by diurnal raptors and mammalian carnivores. Specifically, owl-digested specimens are characterized by a high density of small and short digestive fissures. Within the owls, digestive fissure patterns appear to scale with owl body size. Finally, we used linear discriminant analysis to build a classification scheme from our modern data and applied it to Holocene mouse fossils from Two Ledges Chamber, Nevada. We found that the fossil specimens display the digestive fingerprints of owls. Quantification of microscopic digestive fissures thus offers a promising new approach for elucidating the taphonomic history of individual fossil specimens.

Paleoecological reconstruction relies on accurately determining the taphonomic origin of fossil deposits. Predation is a common mechanism by which skeletal remains become concentrated over time, leading to the formation of modern and fossil prey death assemblages. Skeletal element representation and breakage patterns within such death assemblages can be used to infer the identity of the responsible predator. However, assemblage-level metrics cannot be used to infer if a single fossil specimen is predator-derived. Microscopic digestive etching on individual bones can also indicate past predation events because acidic gastric fluids create distinctive micrometer-scale fissures in cortical bone. Here we establish a quantitative approach to predator identification from small mammal prey remains using microscopic digestive damage patterns. To do this, we collected mandibles from rodents digested by 13 predator species from local wildlife rehabilitation centers, and imaged them using an FEI Quanta 200 SEM. Results indicate that bones exposed to gastric fluids show clear digestive fissures, and that owl-digested specimens can be readily distinguished from specimens that were digested by diurnal raptors and mammalian carnivores. Specifically, owl-digested specimens are characterized by a high density of small and short digestive fissures. Within the owls, digestive fissure patterns appear to scale with owl body size. Finally, we used linear discriminant analysis to build a classification scheme from our modern data and applied it to Holocene mouse fossils from Two Ledges Chamber, Nevada. We found that the fossil specimens display the digestive fingerprints of owls. Quantification of microscopic digestive fissures thus offers a promising new approach for elucidating the taphonomic history of individual fossil specimens.

Geochemistry and Resonance Ionization of Platinum-Group Elements

THE PHLOGOPITE PERIDOTITE OF THE FINERO ULTRAMAFIC COMPLEX (IVREA ZONE, NW ALPS): NEW EVIDENCE OF A METASOMATIZED MANTLE SLAB

The results of a comprehensive study of Pleistocene fish‐bearing localities from the territory of Poland are presented. Fish remains came from lacustrine deposits and cave sites representing a time‐span from the late Early Pleistocene until the Early Holocene. Here we present the taxonomic composition and species diversity of all known fish assemblages from Poland. In total, 23 species belonging to 20 genera of eight families were identified. Cyprinids were the most taxonomically diverse, followed by salmonids and percids. Other families were each represented only by a single species. The roach, rudd, bream, pike and perch were the most common components of the Pleistocene fish assemblages of Poland. These assemblages are clearly divided into two groups representing palaeolakes and cave sites. A significant taxonomic similarity is observed between fish assemblages from Poland and those of Chibanian and Late Pleistocene ages from central and eastern Europe. Pleistocene environments and climates of Poland are characterized using a multi‐proxy approach (analysis of stable isotopes, plant macro‐remains, pollen, molluscs and cladocerans). Obtained data allowed us to estimate a number of parameters of Pleistocene water bodies of the Polish Lowland (reservoir type, trophism, oxygen content, depth and water level changes, bottom character, and flow speed). The formation of freshwater fish assemblages was influenced by dynamic changes in the hydrographic network, and climatic changes during the Pleistocene and Holocene. Their development was favoured by the formation of lakes after melting of the ice sheet.

BackgroundIrregular echinoids are ecosystem engineers with diverse functional services. Documenting present-day distribution of those widespread organisms is important for understanding their ecological significance and enhancing our ability to interpret their rich fossil record.MethodsThis study summarizes SCUBA surveys of clypeasteroid and spatangoid echinoids conducted in 2020 and 2021 along the central part of the Florida Keys. The survey included observations on both live and dead specimens, their distribution, habitat preferences, abundance, and live-dead comparison.ResultsEchinoids were found at 17 out of 27 examined sites (63%) and occurred across a wide range of habitats including coastal seagrass meadows, subtidal sand and seagrass settings of the Hawk Channel, backreef sands, and fine muddy sands of deeper forereef habitats. The encountered species, both dead and alive, included Clypeaster rosaceus (four sites), Clypeaster subdepressus (five sites), Encope michelini (three sites), Leodia sexiesperforata (eight sites), Meoma ventricosa (nine sites), and Plagiobrissus grandis (four sites). All sites were dominated by one species, but some sites included up to five echinoid species. Live-dead fidelity was high, including a good agreement in species composition of living and dead assemblages, congruence in species rank abundance, and overlapping spatial distribution patterns. This high fidelity may either reflect long-term persistence of local echinoid populations or fragility of echinoid tests that could prevent post-mortem transport and the formation of time-averaged death assemblages. Regardless of causative factors, the live-dead comparisons suggest that irregular echinoid assemblages, from settings that are comparable to the study area, may provide a fossil record with a high spatial and compositional fidelity. The survey of live fauna is consistent with past regional surveys in terms of identity of observed species, their rank abundance, and their spatial distribution patterns. The results suggest that despite increasingly frequent hurricanes, active seasonal fisheries, massive tourism, and urban development, irregular echinoids continue to thrive across a wide range of habitats where they provide diverse ecosystem services by oxygenating sediments, recycling organic matter, supporting commensal organisms, and providing food to predators. Results reported here document the present-day status of local echinoid populations and should serve as a useful reference point for assessing future regional changes in echinoid distribution and abundance.

Actualistic studies in freshwater environments are scarce, limiting the interpretation of paleoenvironmental information obtained from the fossil record. The objectives of this study are to assess the taphonomic factors that affect the formation of mollusk assemblages in freshwater environments of the pampean region. Twenty sites were analyzed at regional (La Brava and Nahuel Ruca) and environmental (lentic and lotic) scales. Shells were primarily affected by loss of proteinaceous parts, fragmentation, and fine-scale surface alteration. Taphonomic differences were observed in dead shell condition related to environmental conditions and faunistic composition (thin-/thick-shelled species proportion) in spite of the dominance of one species, Heleobia parchappii. The differences were related to extrinsic (environmental) factors probably due to differential influence of organic decay, microbioerosion, and/or dissolution. However, intrinsic factors, especially those related to differential preservation and input rates of thin-/thick-shelled species, may be also biasing the compositional fidelity of death assemblages. Although the degree of taphonomic alteration across locales and environments was evident, all mollusk assemblages still preserved their biological signature from the precursor communities.

Discrimination and comparison between relatively young (recently dead) and relatively old (less recently dead) shells has been an important component of studies on modern death assemblages. We employed amino acid dating to determine whether or not various shell and taphonomic attributes could be used to categorize Donax into age (time-since-death) categories (e.g., old vs. young). As expected, biological interactions and whether the specimen was a right or left valve were not time-dependent. Abraded shells, shells lacking sheen, those showing evidence of dissolution, fragments and chipped shells tended to be relatively old, but many old shells retained the species' original (living) characteristics with regard to all of these attributes except color and sheen. Shell color was the only attribute yielding a satisfactory division of shells into two age categories, old vs. young. The formation of a typical beach assemblage requires the gradual addition and taphonomic alteration of shells over many hundreds of...

BIOCOENOSES of planktonic foraminifera are usually accepted to be good indicators of different sorts of oceanic water masses1, and it is assumed that their ecological requirements have not changed drastically during the Quaternary2. Their remains have, therefore, been used for approximately the past 40 yr (ref. 3) to study, qualitatively as well as quantitatively, the palaeoclimatic record4 preserved in young, calcareous, deep-sea sediments. Despite this, however, the mechanism of the formation of death assemblages and sediment assemblages is very poorly understood, mainly because the distribution pattern of planktonic foraminiferal biocoenoses and their output of shell material is only poorly known.

Theoretical aspects of the formation of fossil assemblages are explored for the purpose of obtaining criteria and methods for the reconstruction of circumstances of preservation of shallow-water marine organisms. Models are developed which represent: (1) a death assemblage preserved under conditions of rapid burial; (2) an assemblage preserved in situ under conditions of gradual accumulation; and (3) an assemblage composed almost entirely of remains transported to the site of burial. The histories represented by the models influence the following features of fossil assemblages: faunal composition, morphologic composition, density, disassociation of hard parts, fragmentation, surface condition of fossils, chemical and mineralogical composition of fossils, orientation, dispersion, and the texture and structure of the sedimentary aggregate. The expressions of these features indicate that biological criteria are more indicative of the mode of accumulation than physical criteria. The stretched-line method of sampling provides a means of obtaining objective and repeatable measures of features of the fossil assemblages in place. It is restricted to sediments in which fossils can be recovered readily. A rank-correlation analysis of 11 samples from the Pleistocene Millerton formation of Tomales Bay, California, is given as an example of a means of evaluating the interrelations of variables measured by the line technique.

It is my sincere pleasure and honor to introduce Tom Olszewski as winner of the 2009 Charles Schuchert Award. Tom has made significant and lasting scientific contributions over the last decade, addressing a wide range of important questions on the nature of time-averaging and the formation of death assemblages, the question of ecological stability, the mathematical framework of richness and evenness, and the stratigraphy of Carboniferous cyclothems. Growing up just outside Philadelphia, the son of Polish immigrants, Tom's path to the Schuchert Award was neither straight nor inevitable. Tom recalls reading books by Stephen J. Gould in high school. This certainly piqued his curiosity. But it was not until he attended Franklin & Marshall College that his love for paleontology began to flourish. Searching for a work-study job, Tom thankfully avoided cafeteria work, ending up instead in Roger Thomas' lab, where he helped to catalogue fossils that Franklin & Marshall had inherited from the Princeton University collection. Tom claims that it was working with fossils and with a paleontologist that cemented his interest and he became a major in the geology program. Tom began graduate work at the University of Chicago, but chose to leave after a year and a half to pursue a Master's degree at Kansas State University. Tom acknowledges that he did not feel he was scientifically mature enough to pursue independent research at that time. Nonetheless, the short …

Nearshore coastal areas are subject to harsh conditions, being shaped by continuous wave action and exposed to turbulence, erosion, and dynamic processes of sediment reworking. Situated at the interface between land and water, the environmental signatures preserved in microfossil assemblages from coastal environments are often prone to taphonomic alterations, which potentially bias the fossil record and compromise accurate reconstructions. The preservation and composition of microfossil assemblages, however, is of highest importance for paleoenvironmental and paleoclimatic reconstructions.We have analyzed benthic foraminiferal assemblages from a suite of extremely shallow-water habitats along the Dhofar coastline (Oman) to assess their value for paleoenvironmental reconstructions and inferences. Foraminiferal assemblages from these extremely shallow and turbulent water habitats face hostile conditions to their existence and preservation, where the formation of dead assemblages is the result of postmortem processes, among which out-of-habitat transport and the destruction and disintegration of tests are most significant. We examined habitat-specific samples from extreme shallow-water areas to: (1) illustrate and document the species richness and preservation status of foraminiferal assemblages, (2) assess whether the foraminiferal biotas preserve sufficient environmental information to be useful for paleoenvironmental inferences, and (3) provide novel insight into the diversity and composition of benthic foraminifera along the varied habitats of the southern Oman coast. Our analyses show that extremely shallow foraminiferal assemblages from the southern coast of Oman retain the environmental signatures of their habitats despite intense environmental processes, making them useful for paleoenvironmental studies. Features of these signatures are recorded in the structural composition, species richness, dominance, and diversity indices of foraminiferal communities, in addition to numerical abundances of shell preservation groups.

Petrogenesis of Jian forsterite jade solely composed of end-member forsterite (Fo 99.8): Constrained by trace element and oxygen isotope