Abstract Taphonomic studies of Cenozoic mammals are scarce. We report a study of the taphonomy of the Corralito site (Middle Pleistocene to Holocene), Córdoba Province, Argentina, which documents the last population of the South American native ungulate typotherid Mesotherium cristatum. We discovered two specimens of M. cristatum (a hemimandible and postcranial remains) with numerous traces, along with one indeterminate camelid metapodial. Extensive and detailed analysis of these traces using macroscopic and confocal laser scanning microscopy has allowed us to identify various taphonomic agents: carnivoran bite traces, rodent gnawing, trampling, and root etching. We document the ichnotaxa Machichnus and Nihilichus and describe Corralitoichnus conicetensis gen. et sp. nov., which are attributed to Ctenomys incisors, along with Katagmichnus myelus gen. et sp. nov., associated with deep transverse traces on long bones diaphysis linked to bone breakage and marrow consumption by a medium–large carnivoran. This represents the first evidence of such behaviour in South America during the Cenozoic. Furthermore, the taphonomic time sequence of each recognized biological agent was reconstructed using a comprehensive understanding of the different biological processes that affected the specimens from post‐mortem to post‐burial. This study offers direct evidence of distinct biological agents from the Middle Pleistocene, particularly in the western Pampean region, focusing on one of South America's most iconic mammals (M. cristatum). It establishes a solid foundation for future taphonomic research on fossil bones, especially on predation or scavenging traces (Family Machichnidae), a relatively understudied area in South American native ungulates and the continent as a whole.

Abstract The Cretaceous witnessed the establishment of many desertic landscapes across the globe, including the Early Cretaceous Caiuá palaeodesert, in south‐central Brazil, and those of several Late Cretaceous deposits of the Gobi Desert. Although separated in time and space, their faunas share the presence of medium‐sized, edentulous theropods (e.g. oviraptorids and Berthasaura leopoldinae) which depart from the typically carnivorous diet of the group. Here, we report a new dentary of the latter taxon, which bears alveolar vestiges, suggesting that its teeth were lost during ontogeny, as previously reported for another noasaurid, Limusaurus inextricabilis, from the Late Jurassic of China. In addition, we used geometric morphometrics to quantitatively analyse the shape of theropod jaw bones, revealing a significant morphological convergence signal for the dentary of Be. leopoldinae and oviraptorids, which are dorsoventrally deep, and bear a large mandibular fenestra. This probably resulted from adaptations to feed on the tough parts of xerophytic plants, which are important food sources in desertic environments.

Abstract The Plectambonitoidea Jones form an abundant and diverse Palaeozoic clade of the phylum Brachiopoda. The shells were generally small and pursued a recumbent mode of life resting on a convex ventral valve or possibly on a concave dorsal valve. A morphological matrix was constructed for the 123 genera comprising the superfamily, based on 43 characters. The changing disparity through time was evaluated from the morphological matrix based on four different metrics and the diversification and diversity dynamics of the clade revealed using corrected range data from the Paleobiology Database. The group expanded its reach during the Tremadocian, accelerating in numbers during the Floian and Dapingian, and peaking in the Darriwilian. The group suffered a major extinction at the end of the Ordovician, continuing as a dead clade walking until the Middle Devonian. On the other hand, the expansion of disparity predated the hikes in diversity, accelerating during the early part of the Ordovician. In common with other major groups of brachiopods, experimentation and innovation amongst new body plans expanded prior to bursts of diversity at lower taxonomic levels.

Abstract Decay experiments are ever increasing in complexity to better understand taphonomic processes. However, adding new variables, such as sediment, can create methodological biases, such as artificial anatomical character loss during exhumation. Non‐invasive in situ imaging techniques such as x‐ray computed tomography (XCT scanning) could mitigate this, but the consequences of exposing carcasses to x‐rays are not fully understood, and evidence regarding the impact of x‐rays on internal microbial faunas that drive decay is conflicting. Here, we test whether XCT scanning impacts the decay of Danio rerio carcasses within a substrate. Our control experiments show that quartz sand sediment physically stabilizes the carcass throughout decay and the sequence of anatomical character loss remains constant, however, sand initially accelerates the onset and rate of decay of soft tissues. Our XCT data show that exposure to x‐rays does not cause a deviation from the normal sequence of decay, validating XCT as a non‐destructive visualization method for decay experiments. Furthermore, when accompanied with traditional exhumation and dissection, XCT provides decay data with higher accuracy of character analysis than traditional methods, and allows novel quantitative techniques to monitor physical changes in the decaying carcass (e.g. total volume, build‐up of gases, collapse of the body cavity etc.) We underline limitations with the technique, but our experiment acts as an important ‘stepping stone’ for progression toward non‐invasive designs of decay experiments.

Abstract Exceptionally preserved fossils provide critical information on the morphology and ecology of extinct organisms, but their formation requires complex pathways that affect the process of decay in any given depositional environment. The field of experimental taphonomy has produced critical insights that allow us to better understand the physical and chemical mechanisms responsible for fossil preservation. However, taphonomic experiments designed to assess the rate of morphological information loss typically require that they are performed in artificial sea water without sediment to clearly quantify any observable changes over time. Here, we use micro‐computed tomography to non‐invasively investigate changes in carcasses of the branchiopod crustacean Triops longicaudatus for over a year of post‐burial decay. After 64 weeks, specimens are still detectable as three‐dimensional carcass moulds that capture various external morphological features in life position, including the body outline, carapace, and limbs. Our results show that sediment plays a critical role in carcass stabilization in arthropods, maintaining the external integrity of the body over much longer periods of time than previously demonstrated experimentally. We hypothesize that the carcass moulds produced during decay facilitate sites for subsequent mineral precipitation needed for exceptional three‐dimensional fossilization of non‐biomineralized arthropod remains as observed in the fossil record.

Abstract Animals with multi‐element skeletons, including the vertebrates, echinoderms and arthropods, are some of the most biodiverse and ecologically important animal groups. Understanding the relative impact of the myriad geological and biological factors which impact on the quality of multi‐element skeletal fossils is thus crucial for disentangling perceived changes in biodiversity through time and shedding light on gaps in the fossil record. We have characterized the specimen‐level taphonomic history of virtually the entire Palaeozoic fossil record of echinoids, the class of echinoderms which includes the living sea urchins. We find that the majority of this fossil record consists of disarticulated skeletal elements and as preservational quality increases, so does the proportion of specimens which can be identified with higher taxonomic precision. We then assessed the relative impacts of multiple geological and biological factors on our specimen quality, identifying that fine‐grained host matrix, as well as siliciclastic lithology are the biggest factors in determining quality of fossil echinoid preservation, while aspects intrinsic to specific taxonomic groups also play a role. Differential sampling of the fossil record seems to play little role in influencing the distribution of taphonomic grades, and fluctuations in the North American record of siliciclastic rocks are positively correlated with fluctuations in taphonomic grades. Our results highlight that the factors controlling the animal macrofossil record are varied, and that the interplay between these variables, taphonomic grade, and taxonomic precision impacts on our ability to use the fossil record to understand macroevolution.

Abstract The latitudinal biodiversity gradient (LBG) is a fundamental biological pattern seen across taxa and ecosystems today, but its drivers remain uncertain despite intense study. Palaeontological data may add valuable evidence from diversity distributions during intervals with different Earth system configurations, including potential analogues of future climate regimes. However, accurately characterizing these distributions is challenging because the geographic scope of fossil record coverage varies through time, introducing biases that have not been quantified by most previous studies. Here, we attempt a comprehensive documentation of latitudinal biodiversity distributions of marine invertebrates through the past 540 million years, explicitly accounting for regional variation in diversity and sampling. We demonstrate large uncertainties when using current fossil data at this scale. Nevertheless, some signals are detectable. We show that marine animal biodiversity declined with increasing palaeolatitude and with decreasing temperature during at least some intervals from the Permian onwards (298.9 Ma). Additionally, we find that the LBG was shallower on average when Earth's climate was hotter, although this signal is weak. We also document a strong, systematic bias due to intense sampling of the fossil record in North America and especially Europe, which may have led previous studies to incorrectly infer a mid‐latitude diversity peak during warm intervals of Earth history. Our results provide a baseline for what current fossil databases might tell us about Phanerozoic LBGs of marine animals, and suggests that quantitative evaluation of uncertainties and systematic bias will be central to advancing knowledge of geographic variation in diversity through Earth's history.