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in category paleontology

184 results found. For more information, click each entry to expand.

161: Foot scales in the Early Cretaceous bird Gansus yumenensis from China
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Posted 08 Jun 2021

Foot scales in the Early Cretaceous bird Gansus yumenensis from China
299 downloads bioRxiv paleontology

Tao Zhao, Zhiheng LI, He Zhang, Yanhong Pan

Most modern birds have scales covering the foot and feathers elsewhere. Discoveries of fossil feathers attached to the metatarsus in non-avian dinosaurs and basal birds suggests that the avian scales are secondarily derived from feathers. However, our knowledge of early avian scales and their taphonomy is still limited, due to the scarcity of fossil record. Here we employ multiple techniques to characterize the morphological and chemical details preserved and investigate how they are preserved in the skin of IVPP V15077, a referred specimen of the Early Cretaceous Gansus yumenensis. Results show that two types of scales, scutellate and interstitial scales, are preserved in IVPP V15077, which, in combination with previous discovery of scutate and reticulate scales in other Early Cretaceous birds, indicates that all four types of scales present in modern birds have appeared in the Early Cretaceous. SEM observations and Raman analysis suggest that the skin of Gansus yumenensis may be pigmented. Elemental mapping indicates that aluminosilicates and calcium phosphate are involved in the mineralization of the skin.

162: Preservation of collagen in the soft tissues of frozen mammoths
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Posted 12 Apr 2021

Preservation of collagen in the soft tissues of frozen mammoths
294 downloads bioRxiv paleontology

Shunji Hattori, Tomomi Kiriyama-Tanaka, Masashi Kusubata, Yuki Taga, Testuya Ebihara, Katsuyuki Imai, Mitsutaka Miura, Yoshihiro Mezaki, Alexei Tikhonov, Haruki Senoo

We investigated the characteristics of extracellular matrix (ECM) in the soft tissue of two frozen baby woolly mammoths (Mammuthus primigenius) that died and were buried in Siberian permafrost approximately 40,000 years ago. Morphological and biochemical analyses of mammoth lung and liver demonstrated that those soft tissues were preserved at the gross anatomical and histological levels. The ultrastructure of ECM components, namely a fibrillar structure with a collagen-characteristic pattern of cross-striation, was clearly visible with transmission and scanning electron microscopy. Type I and type IV collagens were detected by immunohistochemical observation. Quantitative amino acid analysis of liver and lung tissues of the baby mammoths indicated that collagenous protein is selectively preserved in these tissues as a main protein. Type I and type III collagens were detected as major components by means of liquid chromatography-mass spectrometry analysis after digestion with trypsin. These results indicate that the triple helical collagen molecule, which is resistant to proteinase digestion, has been preserved in the soft tissues of these frozen mammoths for 40,000 years.

163: The petrosal and basicranial morphology of Protoceras celer
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Posted 05 May 2021

The petrosal and basicranial morphology of Protoceras celer
286 downloads bioRxiv paleontology

Selina Viktor Robson, Jessica M Theodor, Brendon Seale

Protoceratids are an extinct family of endemic North American artiodactyls. The phylogenetic position of protoceratids in relation to camelids and ruminants has been contentious for over a century. The petrosal morphology of basal ( Leptotragulus ) and derived ( Syndyoceras ) protoceratids has suggested that protoceratids are closely related to ruminants, whereas a prior description of a disarticulated intermediate protoceratid petrosal ( Protoceras celer ) indicated that protoceratids were closely related to camelids. This contradictory evidence implied that there were several character reversals within the protoceratid lineage and brought into question the utility of basicranial characters in artiodactyl phylogenetics. Here, we provide descriptions of an additional P. celer petrosal. The descriptions are based on data produced by computed tomography scans, which allowed us to image the petrosal in situ in the skull. Our results indicate that the petrosal morphology of P. celer is similar to that of other protoceratids, implying that, contrary to previous evidence, petrosal morphology is conserved within the Protoceratidae.

164: Metacommunity analyses show increase in ecological specialisation throughout the Ediacaran
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Posted 17 May 2021

Metacommunity analyses show increase in ecological specialisation throughout the Ediacaran
284 downloads bioRxiv paleontology

Rebecca Eden, Andrea Manica, Emily G. Mitchell

The first animals appear during the late Ediacaran (572 - 541 Ma); an initial diversity increase was followed by a drop, interpreted as catastrophic mass extinction. We investigate the processes underlying these changes using the "Elements of Metacommunity Structure" framework. The oldest metacommunity was characterized by taxa with wide environmental tolerances, and limited specialisation and inter-taxa interactions. Structuring increased in the middle metacommunity, with groups of taxa sharing synchronous responses to environmental gradients, aggregating into distinct communities. This pattern strengthened in the youngest metacommunity, with communities showing strong environmental segregation and depth structure. Thus, metacommunity structure increased in complexity, with increased specialisation and resulting competitive exclusion, not a catastrophic environmental disaster, leading to diversity loss in the terminal Ediacaran, revealing that the complex eco-evolutionary dynamics associated with Cambrian diversification were established in the Ediacaran.

165: Before trilobite legs: Pygmaclypeatus daziensis reconsidered and the ancestral appendicular organization of Cambrian artiopods
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Posted 19 Aug 2021

Before trilobite legs: Pygmaclypeatus daziensis reconsidered and the ancestral appendicular organization of Cambrian artiopods
281 downloads bioRxiv paleontology

Michel Schmidt, Xianguang Hou, Dayou Zhai, Huijuan Mai, Jelena Belojevic, Xiaohan Chen, Roland R. Melzer, Javier Ortega-Hernandez, Yu Liu

The Cambrian Stage 3 Chengjiang biota in South China is one of the most influential Konservat Lagerstatten worldwide thanks to the fossilization of diverse nonbiomineralizing organisms through pyritization. Despite their contributions to understanding the evolution of early animals, several Chengjiang species remain poorly known due to their scarcity and/or incomplete preservation. Here, we use micro-computed tomography to reveal in detail the ventral appendage organization of the enigmatic non-trilobite artiopod Pygmaclypeatus daziensis, one of the rarest euarthropods in Chengjiang, and explore its functional ecology and broader evolutionary significance. P. daziensis possesses a set of uniramous antennae and 14 pairs of post-antennal biramous appendages, the latter of which show an unexpectedly high degree of heteronomy based on the localized differentiation of the protopodite, endopod and exopod along the antero-posterior body axis. The small body size (less than 2 cm), presence of delicate spinose endites, and well-developed exopods with multiple paddle-shaped lamellae on the appendages of P. daziensis indicate a nekto-benthic mode of life, and a scavenging/detritus feeding strategy. P. daziensis shows that appendage heteronomy is phylogenetically widespread within Artiopoda, the megadiverse clade that includes trilobites and their relatives with nonbiomineralizing exoskeletons and suggests that a single exopod lobe with paddle like lamellae is ancestral for this clade.

166: Ooids forming in situ within microbial mats (Kiritimati atoll, central Pacific)
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Posted 05 May 2021

Ooids forming in situ within microbial mats (Kiritimati atoll, central Pacific)
278 downloads bioRxiv paleontology

Pablo Suarez-Gonzalez, Joachim Reitner

Ooids (subspherical particles with a laminated cortex growing around a nucleus) are ubiquitous in the geological record since the Archean and have been widely studied for more than two centuries. However, various questions about them remain open, particularly about the role of microbial communities and organic matter in their formation and development. Although ooids typically occur rolling around in agitated waters, here we describe for the first time aragonite ooids forming statically within microbial mats from hypersaline ponds of Kiritimati (Kiribati, central Pacific). Subspherical particles had been previously observed in these mats and classified as spherulites, but they grow around autochthonous micritic nuclei, and many of them have laminated cortices, with alternating radial fibrous laminae and micritic laminae. Thus, they are compatible with the definition of ooid and are in fact identical to many modern and fossil examples. Kiritimati ooids are more abundant and developed in some ponds and in some particular layers of the microbial mats, which has led to the discussion and interpretation of their formation processes as product of mat evolution, through a combination of organic and environmental factors. Radial fibrous laminae are formed during periods of increased supersaturation, either by metabolic or environmental processes. Micritic laminae are formed in closer association with the mat exopolymer (EPS) matrix, probably during periods of lower supersaturation and/or stronger EPS degradation. Therefore, this study represents a step forward in the understanding of ooid development as influenced by microbial communities, providing a useful analogue for explaining similar fossil ooids.

167: Identifying planktonic foraminiferal morphospecies: which are the important images?
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Posted 14 Apr 2021

Identifying planktonic foraminiferal morphospecies: which are the important images?
271 downloads bioRxiv paleontology

George Hodge Scott

Selection of imagery that promotes accurate identification of morphotaxa is viewed as a significant problem in the taxonomy of planktonic foraminifera. Currently, imagery of taxa is sparse, apparently selected by visual judgement, and presented without information about its typicality. What is required are impartially selected images which embrace population variation to serve as training sets for reliable identification of taxa. Outlined here is a simple morphometrically-based solution, applied to the shape of shells in two orientations, in which shape variation is resolved onto three principal component axes. On the premise that the best-adapted shells are the commonest, specimens within 1 standard deviation (sd) of the trivariate mean are recognized as population exemplars suitable for use as trainers. Specimens which project at [≥]2 sd onto at least one axis are mapped as boundary specimens whose identity might be questioned. This procedure is trialled on samples of Truncorotalia crassaformis. Exemplars from the Equatorial Atlantic and Caribbean compare closely; they partially overlap with those from a Holocene Southwest Pacific population provisionally interpreted as a subtaxon, Truncorotalia crassaformis hessi.

168: Growth allometry and dental topography in Upper Triassic conodonts supports trophic differentiation and molar-like element function
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Posted 10 Jun 2021

Growth allometry and dental topography in Upper Triassic conodonts supports trophic differentiation and molar-like element function
247 downloads bioRxiv paleontology

Valentin Samuel Kelz, Pauline Guenser, Michele Mazza, Manuel Rigo, Emilia Jarochowska

Conodont dental elements are distinguished by their high disparity and rapid morphological evolution. P1 elements located in the pharynx are the most rapidly evolving, but their function in the animal has been only investigated in a handful of taxa and proposed to be analogous to mammal molars. This hypothesis predicts that their surface area should show positive allometry with respect to element length, as has been previously identified in 2D projections in two Carboniferous taxa. Here we apply the same method to test this hypothesis in 3D models of platform-bearing P1 elements of two common Late Triassic taxa, Metapolygnathus communisti and Epigondolella rigoi. We further hypothesise that these commonly co-occurring taxa differed in their growth allometry, reflecting their different trophic niches. Platform length grew isometrically with respect to element length, whereas log-transformed platform area showed positive allometry with respect to element length, with slopes equal 3.86 in M. communisti and 4.16 in E. rigoi, supporting a function of the platform analogous to molars and trophic differentiation. We cross-tested the latter interpretation by dental topographic analysis using Dirichlet Normal Energy (DNE). Specimens of the adult growth stage of E. rigoi showed higher DNE values than specimens of the same growth stage in M. communisti, consistent with stronger positive allometry of platform surface and with a higher demand for energy in this species. DNE values of platform surface increased linearly in function of element length and log-transformed platform area, indicating no ontogenetic changes. Based on DNE values available for primates, those of the adult growth stages were similar to those reported for insectivores or folivores in the case of E. rigoi and for folivores or omnivores in the case of M. communisti. Previous studies applying morphological and ultrastructural proxies for the dietary position of conodonts addressed mostly stratigraphically older conodont taxa, but our results indicate that Late Triassic species occupied the predator/scavenger niche in spite of the highly developed diversity of gnathostomes in this niche. We also show that within this broad niche, co-occurring taxa differed in their diets, which supports trophic diversification as an important driver of the remarkable disparity of their elements.

169: New cheloniellid arthropod with large raptorial appendages from the Silurian of Wisconsin, USA
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Posted 07 Sep 2018

New cheloniellid arthropod with large raptorial appendages from the Silurian of Wisconsin, USA
235 downloads bioRxiv paleontology

Andrew James Wendruff, Loren Babcock, Donald Mikulic, Joanne Kluessendorf

Cheloniellids comprise a small, distinctive group of Paleozoic arthropods of whose phylogenetic relationships within the Arthropoda remain unresolved. A new form, Latromirus tridens, n. gen, n. sp. is reported from the Waukesha Lagerstatte in the Brandon Bridge Formation (Silurian: Telychian), near Waukesha, Wisconsin, USA. Exceptionally preserved specimens show previously poorly known features including biramous appendages; this is the first cheloniellid to show large, anterior raptorial appendages. We emend the diagnosis of Cheloniellida; cephalic appendages are uniramous and may include raptorial appendages; trunk appendages are biramous.

170: New fossils of Jurassic ophiurid brittle stars (Ophiuroidea; Ophiurida) provide evidence for early clade evolution in the deep sea
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Posted 03 Jun 2021

New fossils of Jurassic ophiurid brittle stars (Ophiuroidea; Ophiurida) provide evidence for early clade evolution in the deep sea
218 downloads bioRxiv paleontology

Ben Thuy, Lea D. Numberger-Thuy, Tania Pineda-Enriquez

Understanding of the evolutionary history of the ophiuroids, or brittle stars, is hampered by a patchy knowledge of the fossil record. Especially the stem members of the living clades are poorly known, resulting in blurry concepts of the early clade evolution and imprecise estimates of divergence ages. Here, we describe new ophiuroid fossil from the Lower Jurassic of France, Luxembourg, and Austria and introduce the new taxa Ophiogojira labadiei gen. et sp. nov. from lower Pliensbachian shallow sublittoral deposits, Ophiogojira andreui gen. et sp. nov. from lower Toarcian shallow sublittoral deposits, and Ophioduplantiera noctiluca gen. et sp. nov. from late Sinemurian to lower Pliensbachian bathyal deposits. A Bayesian morphological phylogenetic analysis shows that Ophiogojira holds a basal position within the order Ophiurida, whereas Ophioduplantiera has a more crownward position within the ophiurid family Ophiuridae. The position of Ophioduplantiera in the evolutionary tree suggests that family-level divergences within the Ophiurida must have occurred before the late Sinemurian, and that ancient slope environments played an important role in fostering early clade evolution.

171: MICROMORPHY OFFERS EFFECTIVE DEFENCE AGAINST PREDATION: INSIGHTS FROM THE COST-BENEFIT ANALYSES OF MICRO GASTROPOD PREDATION RECORD
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Posted 31 May 2021

MICROMORPHY OFFERS EFFECTIVE DEFENCE AGAINST PREDATION: INSIGHTS FROM THE COST-BENEFIT ANALYSES OF MICRO GASTROPOD PREDATION RECORD
195 downloads bioRxiv paleontology

Anupama Chandroth, Devapriya Chattopadhyay

Predation, an important driver of natural selection, is studied in the fossil record using quantifiable traces like drill holes produced by gastropods and repair scars produced after durophagous attacks. Despite the abundance of such records in molluscan prey, predation records of micromolluscs (<5mm) remained unexplored. Using a Miocene assemblage of microgastropods from the Quilon Limestone, India, we established the predatory-prey dynamics with the help of cost-benefit analyses. The overall predation intensity is low (DF = 0.06, RF= 0.04) and does not depend on the relative abundance of prey groups suggesting a non-random prey selection regardless of the encounter frequency. The predation is selective in terms of taxonomy, ornamentation, and size of the prey. The smallest size class has the lowest DF and RF supporting a negative size refugia. Higher IDF in larger size class and ornamented groups implies morphological defense resulting in higher failure. Microgastropods show a lower predation intensity than their regular-sized counterparts in a global comparison of coeval records. Results of the cost-benefit analyses explain this difference; the net energy gain from predatory drilling is found to increase monotonically with increasing prey size making the small prey less beneficial. Because the predators try to maximize net energy gain from a predatory attack, the microgastropod prey characterized by relatively low net energy yield is not preferred in the presence of larger prey. Micromorphy, therefore, appears a viable strategy for the prey group to be adopted as an evolutionary response against predation, especially in resource-limited conditions that fail to support large body size.

172: Generating and testing hypotheses about the fossil record of insect herbivory with a theoretical ecospace
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Posted 16 Jul 2021

Generating and testing hypotheses about the fossil record of insect herbivory with a theoretical ecospace
188 downloads bioRxiv paleontology

Sandra R Schachat, Jonathan L Payne, C. Kevin Boyce, Conrad C Labandeira

A typical fossil flora examined for insect herbivory contains a few hundred leaves and a dozen or two insect damage types. Paleontologists employ a wide variety of metrics to assess differences in herbivory among assemblages: damage type diversity, intensity (the proportion of leaves, or of leaf surface area, with insect damage), the evenness of diversity, and comparisons of the evenness and diversity of the flora to the evenness and diversity of damage types. Although the number of metrics calculated is quite large, given the amount of data that is usually available, the study of insect herbivory in the fossil record still lacks a quantitative framework that can be used to distinguish among different causes of increased insect herbivory and to generate null hypotheses of the magnitude of changes in insect herbivory over time. Moreover, estimates of damage type diversity, the most common metric, are generated with inconsistent sampling standardization routines. Here we demonstrate that coverage-based rarefaction yields valid and reliable estimates of damage type diversity that are robust to differences among floral assemblages in the number of leaves examined, average leaf surface area, and the inclusion of plant organs other than leaves such as seeds and axes. We outline the potential of a theoretical ecospace that combines various metrics to distinguish between potential causes of increased herbivory. We close with a discussion of the most appropriate uses of a theoretical ecospace for insect herbivory, with the overlapping damage type diversities of Paleozoic gymnosperms and Cenozoic angiosperms as a brief case study.

173: Presenting the Compendium Isotoporum Medii Aevi (CIMA) and Bayesian Case Studies
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Posted 06 Aug 2021

Presenting the Compendium Isotoporum Medii Aevi (CIMA) and Bayesian Case Studies
186 downloads bioRxiv paleontology

Carlo Cocozza, Enrico Cirelli, Marcus Gross, Wolf-Ruediger Teegen, Ricardo Fernandes

The Compendium Isotoporum Medii Aevi (CIMA) gathers more than 50 000 isotopic measurements for bioarchaeological samples located within Europe and its margins dating between AD 500-1500. This volume of isotopic data, together with collected supporting information, offers multiple research opportunities. This is illustrated here using novel Bayesian modelling methods on selected case studies to reconstruct medieval human lifeways (i.e. human subsistence, spatial mobility), animal management practices, and paleo-environmental conditions. We also discuss how the integration of isotopic data with other types of archaeological and historical data can improve our knowledge of historical developments throughout medieval Europe.

174: New insights into the earlier evolutionary history of epiphytic macrolichens
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Posted 03 Aug 2021

New insights into the earlier evolutionary history of epiphytic macrolichens
165 downloads bioRxiv paleontology

Qiuxia Yang, Yanyan Wang, Robert Lucking, H. Thorsten Lumbsch, Xin Wang, Zhenyong Du, Yunkang Chen, Ming Bai, Dong Ren, Jiangchun Wei, Hu Li, Yongjie Wang, Xinli Wei

Lichens are well known as pioneer organisms colonizing bare surfaces such as rocks and therefore have been hypothesized to play a role in the early formation of terrestrial ecosystems. Given the rarity of fossil evidence, our understanding of the evolutionary history of lichen-forming fungi is primarily based on molecular dating approaches. These studies suggest extant clades of macrolichens diversified after the K-Pg boundary. Here we corroborate the mid-Mesozoic fossil Daohugouthallus ciliiferus as an epiphytic macrolichen that predates the K-Pg boundary by 100 Mys. Based on new material and geometric morphometric analysis, we demonstrate that the Jurassic fossil is morphologically most similar to Parmeliaceae, but cannot be placed in Parmeliaceae or other similar family-level clades forming macrolichens as these evolved much later. Consequently, a new family, Daohugouthallaceae, is proposed here to accommodate this fossil, which reveals macrolichens may have been diverse long before the Cenozoic diversification of extant lineages.

175: Paleoecological implications of Lower-Middle Triassic stromatolites and microbe-metazoan build-ups in the Germanic Basin: Insights into the aftermath of the Permian - Triassic crisis
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Posted 12 Jul 2021

Paleoecological implications of Lower-Middle Triassic stromatolites and microbe-metazoan build-ups in the Germanic Basin: Insights into the aftermath of the Permian - Triassic crisis
164 downloads bioRxiv paleontology

Yu Pei, Hans Hagdorn, Thomas Voigt, Jan-Peter Duda, Joachim Reitner

The aftermath of the Permian - Triassic crisis is characterized by ubiquitous occurrences of microbial sediments around the world. For instance, Triassic deposits of the Germanic Basin have shown to provide a rich record of stromatolites as well as of microbe-metazoan build-ups with non-spicular demosponges. Despite their paleoecological significance, however, all of these microbialites have only rarely been studied. This study aims to fill this gap by examining and comparing microbialites from the Upper Buntsandstein (Olenekian, Early Triassic) and the lower Middle Muschelkalk (Anisian, Middle Triassic). By combining analytical petrography (optical microscopy, micro X-ray fluorescence, Raman spectroscopy) and geochemistry ({delta}13Ccarb, {delta}18Ocarb), we show that all studied microbialites formed in hypersaline lagoons to sabkha environments. Olenekian deposits in Jena and surroundings and Anisian strata at Werbach contain stromatolites. Anisian successions at Hardheim, in contrast, host microbe-metazoan build-ups. Thus, the key-difference is the absence or presence of non-spicular demosponges in microbialites. After the Permian - Triassic crisis, the widespread microbialites (e.g., stromatolites/microbe-metazoan build-ups) possibly resulted from suppressed ecological competition and occupied the vacant ecological niche. It seems plausible that microbes and non-spicular demosponges had a mutualistic relationship and it is tempting to speculate that the investigated microbial-metazoan build-ups reflect an ancient evolutionary and ecologic association. Furthermore, both microbes and non-spicular demosponges may benefit from elevated salinities. Perhaps it was minor differences in salinities that controlled whether or not non-spicular demosponges could develop.

176: Morphometric Analysis of Lungfish Endocasts Elucidates Early Dipnoan Palaeoneurological Evolution
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Posted 15 Sep 2021

Morphometric Analysis of Lungfish Endocasts Elucidates Early Dipnoan Palaeoneurological Evolution
151 downloads bioRxiv paleontology

Alice M Clement, Tom J Challands, Richard Cloutier, Laurent Houle, Per E Ahlberg, Shaun P Collin, John A Long

Lungfish (Dipnoi) are lobe-finned fish (Sarcopterygii) that have persisted for over 400 million years from the Devonian Period to present day. They are the extant sister group to tetrapods and thus have the ability to provide unique insight into the condition of the earliest tetrapods as well as their own evolutionary history. The evolution of their dermal skull and dentition is relatively well understood, but this is not the case for the central nervous system. While the brain itself has very poor preservation potential and is not currently known in any fossil lungfish, substantial indirect information about it and associated structures such as the inner ears can be obtained from the cranial endocast. However, before the recent development of X-ray tomography as a palaeontological tool, these endocasts could not be studied non-destructively, and few detailed studies were undertaken. Here we describe and illustrate the endocasts of six Palaeozoic lungfishes (Iowadipterus halli, Gogodipterus paddyensis, Pillararhynchus longi, Griphognathus whitei, Orlovichthys limnatis, and Rhinodipterus ulrichi) from tomographic scans. We combine these with six previously described lungfish endocasts (4 fossil and 2 recent taxa), also based on tomographic studies, into a 12-taxon data set for multivariate morphometric analysis using 17 variables. We find that the olfactory region appears to be more highly plastic than the hindbrain, and undergoes significant elongation in several taxa. Further, while the semicircular canals covary as an integrated module, the utriculus and sacculus of the inner ear instead vary independently of each other. The functional and phylogenetic implications of our findings are discussed.

177: An age-depth model and revised stratigraphy of vertebrate-bearing units in Natural Trap Cave, Wyoming
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Posted 01 Aug 2021

An age-depth model and revised stratigraphy of vertebrate-bearing units in Natural Trap Cave, Wyoming
139 downloads bioRxiv paleontology

David Michael Lovelace, Cory M. Redman, Thomas A. Minckley, Blaine W Schubert, Shannon Mahan, John R. Wood, Jenny L. McGuire, Juan Laden, Kathleen Bitterman, Holly Heiniger, Lindsey Fenderson, Alan Cooper, Kieren Mitchell, Julie A. Meachen

Almost a half-century ago excavations at Natural Trap Cave (NTC) began to yield evidence of the steppe paleoecology along the western slope of the Bighorn Mountains in north central Wyoming. The first decade of fieldwork led to the discovery of a diverse fauna that existed at the end of the Last Glacial Maximum. Stratigraphic deposits below the entrance of the cave were studied soon after excavations began, but never formally published. Although stratigraphy, taphonomy, and depositional circumstances were briefly discussed over the following years, little has been done to correlate the numerous stratigraphic schemes used by various authors. In this study, four stratigraphic sections were measured and analysed to establish an easily modifiable lithostratigraphic system of nomenclature. We provide the first correlations of all stratigraphic nomenclature used throughout excavations at NTC to facilitate comparisons with current and previous collections and publications. By leveraging more than 100 radioisotopic dates we developed an age-depth model and chronostratigraphic framework to further interrogate spatiotemporal relationships between strata, paleoenvironmental proxies, and fossil assemblages. Deposition is shown to be discontinuous; sediment accumulation in the study area is restricted to the buildup through peak penultimate and Last Glacial maxima. More recent (<10 ka) Holocene deposits unconformably cover the eroded surface of underlying Pleistocene strata. There is active reworking of sediments with transport and deposition of reactivated sediments within the Lower Chamber. We note that the two hiatuses coincide with interglacial periods and may reflect changing depositional circumstances within the cave such as extended periods of non-deposition, erosion, or bypass (possibly leading to deposition in the Lower Chamber). Contrary to previous reports, we demonstrate that it is unlikely a prominent snow cone existed or contributed to the pattern of sediment and fossil distribution within the study area, furthermore, we do not observe a continuous Pleistocene-Holocene transition in the study area. Further stratigraphic work will be needed to better understand the interrelationship between Main and Lower chamber deposits and the evolution of sediment accumulation in NTC.

178: High lineage survivorship across the end-Devonian Mass Extinction suggested by a remarkable new Late Devonian actinopterygian
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Posted 03 Sep 2021

High lineage survivorship across the end-Devonian Mass Extinction suggested by a remarkable new Late Devonian actinopterygian
138 downloads bioRxiv paleontology

Sam Giles, Kara Feilich, Stephanie E Pierce, Matt Friedman

Actinopterygian (ray-finned) fishes represent the principal vertebrate group in aquatic settings. This dominance is often attributed to their apparent success in the aftermath of the end-Devonian extinction. Increases in taxonomic and morphological diversity in the early Carboniferous, coupled with phylogenetic hypotheses implying the survival of few Devonian lineages, contribute to a model of explosive post-extinction radiation. However, most actinopterygian fossils from within a ca. 20 Myr window surrounding the end-Devonian extinction remain poorly known, contributing to uncertainty about these patterns. Here we present detailed anatomical data for an exceptionally preserved but diminutive ray-finned fish from within this gap, ~7 Myr prior to the Devonian-Carboniferous boundary. Representing a new genus and species, it bears a series of derived anatomical features otherwise known only from Carboniferous and younger taxa. It nests phylogenetically within a clade of post-Devonian species and, in an expanded phylogenetic analysis incorporating other previously neglected taxa, draws at least ten lineages of Carboniferous actinopterygians into the Late Devonian. This suggests phenotypically cryptic divergence among ray-finned fishes in the latest Devonian, followed by more conspicuous diversification in feeding and locomotor structures in the Carboniferous. This revised model finds parallels in patterns emerging for other clades, and provides a refined perspective on key events early in the history of a group that today contains half of all living vertebrate species.

179: Population modelling insights of extinct environments: the case of the Kem Kem palaeocommunity
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Posted 09 Sep 2021

Population modelling insights of extinct environments: the case of the Kem Kem palaeocommunity
133 downloads bioRxiv paleontology

Lucas dos Anjos

The Kem Kem beds are well-known palaeontological deposits. Among the species that lived there, there are some large theropods, such as Deltadromeus agilis, Carcharodontosaurus saharicus, and Spinosaurus aegyptiacus. It is possible that these large predators were facultative scavengers, and they could compete for carrion. In the present paper, I simulate a small community module of this environment, consisting of Carrion, Fishes, Spinosaurus, and a functional group composed of large terrestrial Theropods. I assume that these top predators feed on carrion, but they also have exclusive food sources. I show that these exclusive food sources could have assured the possibility of coexistence, and in their absence, one top predator could be locally extinct.

180: Bioerosion traces and borings in the Upper Devonian vertebrate remains from the Holy Cross Mountains, Poland Bioerosion in fish remains
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Posted 24 Jul 2021

Bioerosion traces and borings in the Upper Devonian vertebrate remains from the Holy Cross Mountains, Poland Bioerosion in fish remains
131 downloads bioRxiv paleontology

Piotr Szrek, Patrycja G. Dworczak, Olga Wilk

Among the hundreds of collected Devonian vertebrate macrofossils in the Holy Cross Mountains, placoderms dominate and provide data on their morphology, distribution and taphonomy. So far 17 out of more than 500 studied specimens have revealed bones with surfaces covered by sediment-filled trace fossils. The traces have been made on the vertebrate remains before their final burial. The borings, oval in cross-section, include dendroidal networks of shallow tunnels or short, straight or curved individual scratches and grooves, which frequently create groups on the both sides of the bones. ?Karethraichnus isp. from Kowala and ?Osteocallis isp. from Wietrznia are the oldest record of these ichnogenera. Sedimentological clues indicate a shallow water environment, probably from the slope below the storm wave base.

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