Some recent non-dino papers:
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Free pdf:
Microwear textures on mole teeth show no relationship with environmental abrasives.
Diet appears to dominate microwear of small insectivores at extremes of grit load.
There are no differences in microwear formed in high- and low-grit environments.
Implications for the diets and habits of fossil mammals are discussed with examples.
Abstract
Dental microwear texture analysis (DMTA) is a key proxy used to reconstruct the diets of extant and extinct animals. Causal agents of dental wear have been debated for decades, but the recent controversial suggestion that exogenous abrasives (or 'grit' particles) from the environment exert a greater influence on microwear formation than food items has led to renewed interest in this field of research. Feeding trials using large mammals suggest that DMTA can distinguish dietary differences despite variable grit loads. However, the effect of exogenous abrasives on the dental microwear of small, non-herbivorous mammals with quantified grit loads remains untested. Here, we examine dental microwear textures from the European mole (Talpa europaea), which provides an ideal test for the role of grit given moles' subterranean habitat and diet dominated by earthworms that contain, and are coated by, exogenous abrasives. We quantify the environmental abrasive load (by measuring silicate content of soils) and dietary abrasive load (by measuring silicate content of stomach contents) for moles from sites across Norfolk, UK to evaluate the effect of variation in grit loads on microwear textures. No significant relationships are found between microwear texture parameters and any metric of exogenous abrasive load, or between texture parameters and physical soil grit characteristics. Comparing mole microwear textures with those of bats, which have negligible environmental abrasive loads, reveals that moles are indistinguishable in multivariate texture-dietary space from bats that consume 'soft' prey, supporting suggestions that microwear textures preserve accurate dietary signatures and are not overwritten by wear from exogenous abrasives. Drawing upon examples from Jurassic mammaliaforms, we demonstrate the implications of these results for reconstructing the diets and habits of fossil mammals.
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Free pdf:
David Jebb, Zixia Huang, Martin Pippel, Graham M. Hughes, Ksenia Lavrichenko, Paolo Devanna, Sylke Winkler, Lars S. Jermiin, Emilia C. Skirmuntt, Aris Katzourakis, Lucy Burkitt-Gray, David A. Ray, Kevin A. M. Sullivan, Juliana G. Roscito, Bogdan M. Kirilenko, Liliana M. DÃvalos, Angelique P. Corthals, Megan L. Power, Gareth Jones, Roger D. Ransome, Dina K. N. Dechmann, Andrea G. Locatelli, SÃbastien J. Puechmaille, Olivier Fedrigo, Erich D. Jarvis, Michael Hiller, Sonja C. Vernes, Eugene W. Myers & Emma C. Teeling (2020)
Six reference-quality genomes reveal evolution of bat adaptations.
Nature 583: 578-584
DOI:
https://doi.org/10.1038/s41586-020-2486-3https://www.nature.com/articles/s41586-020-2486-3
Bats possess extraordinary adaptations, including flight, echolocation, extreme longevity and unique immunity. High-quality genomes are crucial for understanding the molecular basis and evolution of these traits. Here we incorporated long-read sequencing and state-of-the-art scaffolding protocols to generate, to our knowledge, the first reference-quality genomes of six bat species (Rhinolophus ferrumequinum, Rousettus aegyptiacus, Phyllostomus discolor, Myotis myotis, Pipistrellus kuhlii and Molossus molossus). We integrated gene projections from our 'Tool to infer Orthologs from Genome Alignments' (TOGA) software with de novo and homology gene predictions as well as short- and long-read transcriptomics to generate highly complete gene annotations. To resolve the phylogenetic position of bats within Laurasiatheria, we applied several phylogenetic methods to comprehensive sets of orthologous protein-coding and noncoding regions of the genome, and identified a basal origin for bats within Scrotifera. Our genome-wide screens revealed positive selection on hearing-related genes in the ancestral branch of bats, which is indicative of laryngeal echolocation being an ancestral trait in this clade. We found selection and loss of immunity-related genes (including pro-inflammatory NF-ÎB regulators) and expansions of anti-viral APOBEC3 genes, which highlights molecular mechanisms that may contribute to the exceptional immunity of bats. Genomic integrations of diverse viruses provide a genomic record of historical tolerance to viral infection in bats. Finally, we found and experimentally validated bat-specific variation in microRNAs, which may regulate bat-specific gene-_expression_ programs. Our reference-quality bat genomes provide the resources required to uncover and validate the genomic basis of adaptations of bats, and stimulate new avenues of research that are directly relevant to human health and disease.
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Free pdf:
Free pdf:
https://www.nature.com/articles/s41598-020-68482-5.pdfMolecular and morphological phylogenies concur in indicating that the African lineages formerly referred to Crocodylus niloticus are the sister taxon the four Neotropical crocodiles (Crocodylus intermedius, C. moreleti, C. acutus and C. rhombifer), implying a transoceanic dispersal from Africa to America. So far the fossil record did not contribute to identify a possible African forerunner of the Neotropical species but, curiously, the oldest remains referred to the African C. niloticus are Quaternary in age, whereas the oldest American fossils of Crocodylus are older, being dated to the early Pliocene, suggesting that another species could be involved. We re-described, also thanks to CT imaging, the only well-preserved topotipic skull of Crocodylus checchiai Maccagno, 1947 from the late Miocene (Messinian) African site of As Sahabi in Libya. As previously suggested on the basis of late Miocene material from Tanzania, C. checchiai is a valid, diagnosable species. According to our phylogenetic analyses, C. checchiai is related to the Neotropical taxa and could be even located at the base of their radiation, therefore representing the missing link between the African and the American lineages.
News:
Fossils reveal ancient crocodiles made an incredible, cross-ocean journey
In Spanish
In Catalan
Ancient African skull sheds light on American crocodile origins
Cooper R. Fasulo, Kenneth D. Ridgway & Jeffrey M. Trop (2020)
Detrital zircon geochronology and Hf isotope geochemistry of Mesozoic sedimentary basins in south-central Alaska: Insights into regional sediment transport, basin development, and tectonics along the NW Cordilleran margin.
Geosphere (advance online publication)
doi:
https://doi.org/10.1130/GES02221.1 https://pubs.geoscienceworld.org/gsa/geosphere/article/doi/10.1130/GES02221.1/588246/Detrital-zircon-geochronology-and-Hf-isotopeThe Jurassic-Cretaceous Nutzotin, Wrangell Mountains, and Wellesly basins provide an archive of subduction and collisional processes along the southern Alaska convergent margin. This study presents U-Pb ages from each of the three basins, and Hf isotope compositions of detrital zircons from the Nutzotin and Wellesly basins. U-Pb detrital zircon ages from the Upper JurassicâLower Cretaceous Nutzotin Mountains sequence in the Nutzotin basin have unimodal populations between 155 and 133 Ma and primarily juvenile Hf isotope compositions. Detrital zircon ages from the Wrangell Mountains basin document unimodal peak ages between 159 and 152 Ma in Upper JurassicâLower Cretaceous strata and multimodal peak ages between 196 and 76 Ma for Upper Cretaceous strata. Detrital zircon ages from the Wellesly basin display multimodal peak ages between 216 and 124 Ma and juvenile to evolved Hf compositions. Detrital zircon data from the Wellesly basin are inconsistent with a previous interpretation that suggested the Wellesly and Nutzotin basins are proximal-to-distal equivalents. Our results suggest that Wellesly basin strata are more akin to the Kahiltna basin, which requires that these basins may have been offset ~380 km along the Denali fault. Our findings from the Wrangell Mountains and Nutzotin basins are consistent with previous stratigraphic interpretations that suggest the two basins formed as a connected retroarc basin system. Integration of our data with previously published data documents a strong provenance and temporal link between depocenters along the southern Alaska convergent margin. Results of our study also have implications for the ongoing discussion concerning the polarity of subduction along the Mesozoic margin of western North America.
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Upper Permian to Lower Triassic coastal plain successions of the Sydney Basin in eastern Australia have been investigated in outcrop and continuous drillcores. The purpose of the investigation is to provide an assessment of palaeoenvironmental change at high southern palaeolatitudes in a continental margin context for the late Permian (Lopingian), across the endâPermian Extinction interval, and into the Early Triassic. These basins were affected by explosive volcanic eruptions during the late Permian and, to a much lesser extent, during the Early Triassic, allowing highâresolution age determination on the numerous tuff horizons. Palaeobotanical and radiogenic isotope data indicate that the endâPermian Extinction occurs at the top of the uppermost coal and the PermoâTriassic boundary, either within an immediately overlying mudrock succession or within a succeeding channel sandstone body, depending on locality due to lateral variation. Late Permian depositional environments were initially (during the Wuchiapingian) shallow marine and deltaic, but coastal plain fluvial environments with extensive coalâforming mires became progressively established during the early late Permian, reflected in numerous preserved coal seams. The fluvial style of coastal plain channel deposits varies geographically. However, apart from the loss of peatâforming mires, no significant longâterm change in depositional style (grain size, sedimentâbody architecture, or sediment dispersal direction) was noted across the endâPermian Extinction (pinpointed by turnover of the palaeoflora). There is no evidence for immediate aridification across the boundary despite a loss of coal from successions. Rather, the endâPermian Extinction marks the base of a longâterm, progressive trend towards betterâdrained alluvial conditions into the Early Triassic. Indeed, the floral turnover was immediately followed by a flooding event in basinal depocentres, following which fluvial systems similar to those active prior to the endâPermian Extinction were reâestablished. The age of the floral extinction is constrained to 252.54 Â 0.08 to 252.10 Â 0.06 Ma by a suite of new Chemical Abrasion Isotope Dilution Thermal Ionization Mass Spectrometry UâPb ages on zircon grains. Another new age indicates that the return to fluvial sedimentation similar to that before the endâPermian Extinction occurred in the basal Triassic (prior to 251.51 Â 0.14 Ma). The character of the surface separating coalâbearing preâendâPermian Extinction from coalâbarren postâendâPermian Extinction strata varies across the basins. In basinâcentral locations, the contact varies from disconformable, where a fluvial channel body has cut down to the level of the top coal, to conformable where the top coal is overlain by mudrocks and interbedded sandstoneâsiltstone facies. In basinâmarginal locations, however, the contact is a pronounced erosional disconformity with coarseâgrained alluvial facies overlying older Permian rocks. There is no evidence that the contact is everywhere a disconformity or unconformity.