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Results 181 through 198 out of 198

in category paleontology


181: An age-depth model and revised stratigraphy of vertebrate-bearing units in Natural Trap Cave, Wyoming

David Michael Lovelace, Cory M. Redman et al.

241 downloads (posted 01 Aug 2021)

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.


182: New cheloniellid arthropod with large raptorial appendages from the Silurian of Wisconsin, USA

Andrew James Wendruff, Loren Babcock et al.

235 downloads (posted 07 Sep 2018)

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 diagno...


183: Morphometric Analysis of Lungfish Endocasts Elucidates Early Dipnoan Palaeoneurological Evolution

Alice M Clement, Tom J Challands et al.

228 downloads (posted 15 Sep 2021)

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 potentia...


184: Comments on a small sabretooth cat in the Abismo Ponta de Flecha Cave, Vale do Ribeira, southeastern Brazil

Artur Chahud

228 downloads (posted 06 Sep 2021)

The Vale do Ribeira, located in southeastern Brazil, is known for many caves with osteological material, including several extinct species. The saber-tooth cat Smilodon populator was a large predator that inhabited the Pleistocene and Holocene of South America. A specimen found in the Abismo Ponta de Flecha Cave based on small bones (metacarpals and phalanges) is commented here. The metacarpals have morphological characteristics of S. populator, but are smaller than that of S. fatalis and Panthera onca and larger than t...


185: The scratch-digging lifestyle of the Permian "microsaur" Batropetes as a model for the exaptative origin of jumping locomotion in frogs

Maren Jansen, David Marjanović

204 downloads (posted 27 Sep 2021)

Recent studies have shown that the Triassic stem-frog Triadobatrachus lacked the ability to jump off, but nonetheless had the forelimb strength to withstand the impact of landing from a jump. We propose a hypothesis to resolve this pseudoparadox: the strengthened forelimbs are former adaptations to forelimb-based digging that later made jumping possible by exaptation. Micro-CT data from a skeleton of Batropetes palatinus reveal thin cortical bone, confirming Batropetes as terrestrial. Combining adaptations to walking an...


186: Bioerosion traces and borings in the Upper Devonian vertebrate remains from the Holy Cross Mountains, Poland Bioerosion in fish remains

Piotr Szrek, Patrycja G. Dworczak et al.

201 downloads (posted 24 Jul 2021)

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 groo...


187: Three new Cenomanian conifers from El Chango (Chiapas, Mexico) offer a snapshot of the geographic mosaic of the Mesozoic conifer decline

Ixchel Gonzalez-Ramirez, Sergio RS Cevallos-Ferriz et al.

188 downloads (posted 03 Sep 2021)

Premise of study: El Chango is a recently discovered quarry that contains extremely well preserved fossils. The Cenomanian age of the locality corresponds to a time when the global flora was transitioning from gymnosperm- to angiosperm-dominated, yet conifers predominate in this locality. These fossils thus provide a rare opportunity to understand the replacement of conifers by angiosperms as the dominant group of plants. Methods: We collected material from El Chango in annual expeditions (2010 to 2014). We selected the...


188: The response of Oligo-Miocene bivalve fauna of the Kutch Basin (western India) to regional changes in tectonics and climate

Saurav Dutta, Devapriya Chattopadhyay

177 downloads (posted 09 Sep 2021)

Tectonic changes have influenced the evolution of the marine community by changing the seaway configuration over time. Two such tectonic events during Oligo-Miocene, the closure of the Tethyan seaway leading to separation of the Arabian sea from proto-Mediterranean (~19 Ma) and significant uplift of the Tibetan plateau marking the initiation of the monsoon (~16 Ma), represent a classic case of tectonic shift influencing the regional environment of the Indian subcontinent. We investigated the taxonomic and body-size resp...


189: Belemnite phylogeny and decline during the mid-Cretaceous

Kevin Stevens

175 downloads (posted 12 Oct 2021)

Belemnites are common fossil coleoid cephalopods of the Mesozoic. They began to diversify in the Triassic-Early Jurassic and maintained this diversity until the early Early Cretaceous. During the mid-Cretaceous, they declined in diversity and distribution, being restricted to only the Boreal and Austral Realm since the Turonian. Here, I present the first cladistic analysis of belemnite phylogeny, spanning taxa representative of the whole diversity and stratigraphic range of the group. This analysis shows that the usuall...


190: Orientations of Mistaken Point fronds indicate morphology impacted ability to survive turbulence

Philip B. Vixseboxse, Charlotte G. Kenchington et al.

174 downloads (posted 11 Sep 2021)

The Ediacaran organisms of the Mistaken Point E surface have provided crucial insight into early animal communities, including how they reproduced, the importance of Ediacaran height and what the most important factors were to their community dynamics. Here, we use this iconic community to investigate how morphological variation between eight taxa affected their ability to withstand different flow conditions. For each of Beothukis, Bradgatia, Charniodiscus procerus, Charniodiscus spinosus, Plumeropriscum, Primocandelabr...


191: Global ecomorphological restructuring of dominant marine reptiles prior to the K/Pg mass extinction

Jamie A MacLaren, Rebecca F Bennion et al.

171 downloads (posted 01 Jan 2022)

Mosasaurid squamates were the dominant amniote predators in marine ecosystems during most of the Late Cretaceous. Evidence from multiple sites worldwide of a global mosasaurid community restructuring across the Campanian-Maastrichtian transition may have wide-ranging implications for the evolution of diversity of these top oceanic predators. In this study, we use a suite of biomechanical traits and functionally descriptive ratios to investigate how the morphofunctional disparity of mosasaurids evolved through time and s...


192: The first Miocene fossils from coastal woodlands in the southern East African Rift

Rene Bobe, Vera Aldeias et al.

153 downloads (posted 18 Dec 2021)

The Miocene is a key time in the evolution of African mammals and their ecosystems witnessing the origin of the African apes and the isolation of eastern coastal forests through an expanding biogeographic arid corridor. Until recently, however, Miocene sites from the southeastern regions of the continent were unknown. Here we report discovery of the first Miocene fossil teeth from the shoulders of the Urema Rift in Gorongosa National Park, Mozambique, at the southern East African Rift System. We provide the first 1) rad...


193: Linking host plants to damage types in the fossil record of insect herbivory

Sandra R Schachat, Jonathan L. Payne et al.

135 downloads (posted 05 Nov 2021)

Studies of insect herbivory on fossilized leaves tend to focus on a few, relatively simple metrics that are agnostic to the distribution of insect damage types among host plants. More complex metrics that link particular damage types to particular host plants have the potential to address additional ecological questions, but such metrics can be biased by sampling incompleteness due to the difficulty of distinguishing the true absence of a particular interaction from the failure to detect it---a challenge that has been r...


194: Relationships between the hard and soft dimensions of the nose in Pan troglodytes and Homo sapiens reveal the nasal protrusions of Plio-Pleistocene hominids

Ryan M. Campbell, Gabriel Vinas et al.

134 downloads (posted 18 Oct 2021)

By identifying similarity in bone and soft tissue covariation patterns in hominids, it is possible to produce facial approximation methods that are compatible with more than one species of primate. In this study, we conducted an interspecific comparison of the nasomaxillary region in chimpanzees and modern humans with the aim of producing a method for predicting the nasal protrusions of ancient Plio-Pleistocene hominids. We addressed this aim by first collecting and performing regression analyses of linear and angular m...


195: New fossil wasp species from the earliest Eocene Fur Formation has its closest relatives in late Eocene ambers (Hymenoptera, Ichneumonidae, Pherhombinae)

Noah Meier, Anina Wacker et al.

107 downloads (posted 22 Nov 2021)

Darwin wasps (Ichneumonidae) are one of the most species-rich insect families, but also one of the most understudied ones, both in terms of their extant and extinct diversity. We here use morphometrics of wing veins and an integrative Bayesian analysis to place a new rock fossil species from the Danish Fur Formation (~54 Ma) in the tree of Darwin wasps. The new species, Pherhombus parvulus n. sp., is placed firmly in Pherhombinae, an extinct subfamily so far only known from Baltic and Rovno-Ukranian ambers, which are es...


196: High diversity of pimpline parasitoid wasps (Hymenoptera, Ichneumonidae, Pimplinae) from the lowermost Eocene Fur Formation

Seraina Klopfstein

97 downloads (posted 19 Nov 2021)

With an estimated 100,000 extant species, Darwin wasps (Ichneumonidae) are more specious than all vertebrates together. However, only 288 fossil species have been described to date, with hundreds more awaiting formal description in palaeontological collections. One of the largest gaps in our knowledge concerns the ~12 million years between the K-PG mass extinction and the late Ypresian, from which only two species have been formally described, including Pimpla stigmatica Henriksen from the Danish Fur Formation (~55 Ma)....


197: On the dynamics of spatial updating

Jean Blouin, Jean-Philippe Pialasse et al.

91 downloads (posted 28 Oct 2021)

Most of our knowledge on the human neural bases of spatial updating comes from fMRI studies in which recumbent participants moved in virtual environments. As a result, little is known about the dynamic of spatial updating during real body motion. Here, we exploited the high temporal resolution of electroencephalography (EEG) to investigate the dynamics of cortical activation in a spatial updating task where participants had to remember their initial orientation while they were passively rotated about their vertical axis...


198: A community-developed extension to Darwin Core for reporting the chronometric age of specimens

Laura Brenskelle, John Wieczorek et al.

85 downloads (posted 24 Nov 2021)

Darwin Core, the data standard used for sharing modern biodiversity and paleodiversity occurrence records, has previously lacked proper mechanisms for reporting what is known about the estimated age range of specimens from deep time. This has led to data providers putting these data in fields where they cannot easily be found by users, which impedes the reuse and improvement of these data by other researchers. Here we describe the development of the Chronometric Age Extension to Darwin Core, a ratified, community-develo...