Some recent non-dino papers:
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Manuel Rigo, Tetsuji Onoue, Lawrence Tanner, Spencer G. Lucas, Linda Godfrey, Miriam E. Katz, Mariachiara Zaffani, Kliti Grice, Jaime Cesar, Daisuke Yamashita, Matteo Marona, Lydia S. Tackett, Hamish Campbell, Fabio Tateo, Giuseppe Concheri, Claudia Agnini, Marco Chiari & Angela Bertinelli (2020)
The Late Triassic Extinction at the Norian/Rhaetian boundary: Biotic evidence and geochemical analysis.
Earth-Science Reviews 103180Â (advance online publication)
doi:
https://doi.org/10.1016/j.earscirev.2020.103180 https://www.sciencedirect.com/science/article/abs/pii/S0012825220302269The latest Triassic was an interval of prolonged biotic extinction culminating in the end-Triassic Extinction (ETE). The ETE is now associated with a perturbation of the global carbon cycle just before the end of the Triassic that has been attributed to the extensive volcanism of the Circum-Atlantic Magmatic Province (CAMP). However, we attribute the onset of declining latest Triassic diversity to an older perturbation of the carbon cycle (Î13Corg) of global extent at or very close to the Norian/Rhaetian boundary (NRB). The NRB appears to be the culmination of stepwise biotic turnovers that characterize the latest Triassic and includes global extinctions of significant marine and terrestrial fossil groups. These biotic events across the NRB have been largely under-appreciated, yet together with a coeval disturbance of the carbon cycle were pivotal in the history of the Late Triassic. Here, we present new and published Î13Corg data from widespread sections (Italy, Greece, Australia, New Zealand, USA, Canada). These sections document a previously unknown perturbation in the carbon cycle of global extent that spanned the NRB. The disturbance extended across the Panthalassa Ocean to both sides of the Pangaean supercontinent and is recorded in both the Northern and Southern Hemispheres. The onset of stepwise Late Triassic extinctions coincides with carbon perturbation (Î13Corg) at the NRB, indicating that a combination of climatic and environmental changes impacted biota at a global scale. The NRB event may have been triggered either by gas emissions from the eruption of a large igneous province pre-dating the NRB, by a bolide impact of significant size or by some alternative source of greenhouse gas emissions. As yet, it has not been possible to clearly determine which of these trigger scenarios was responsible; the evidence is insufficient to decisively identify the causal mechanism and merits further study.
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Ashley C. McGrath, David J. Varricchion & James L. Hayward (2020)
Taphonomic assessment of material generated by an Arboreal Nesting Colony of Great Blue Herons (Ardea herodias).
Historical Biology (advance online publication)
doi:
https://doi.org/10.1080/08912963.2020.1741571 https://www.tandfonline.com/doi/full/10.1080/08912963.2020.1741571Reports on nesting debris generated by great blue heron (Ardea herodias), arboreal nesting birds with 'semi-altricial' young, are limited. In this study, surface and subsurface sampling were conducted in 2012 and 2013 in a heronry near the Missouri River in Montana, including bi-weekly collections in 2013 documenting accumulations over the breeding season. Disarticulated juvenile heron bones with lesser numbers of microvertebrates (fish and small mammals) and invertebrates (crayfish and snails) dominated the assemblage beneath the nests. Eggshell on the surface was present but uncommon (0.85 eggshells/m2) with eggshell orientation varying both by location and fragment size. Eggshell surveys differed with respect to sampled trees and sampling time, but generally favoured concave-up orientation whereas the early season small eggshell survey further from sampled trees favoured concave down. Shallow (10 cm deep) excavation revealed a subsurface assemblage very similar to that on the surface but favouring more resistant elements. Hence, the subsurface assemblage was nearly devoid of eggshell, with a lower representation of invertebrates and fragile bone, but an excess of heron hindlimbs. Our study demonstrates that arboreal nesting sites have the potential for long-term preservation and provides information useful for recognition and reconstruction of arboreal nesting sites from the fossil record.
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Free pdf:
Mammals articulate their jaws using a novel joint between the dentary and squamosal bones. In eutherian mammals, this joint forms in the embryo, supporting feeding and vocalisation from birth. In contrast, marsupials and monotremes exhibit extreme altriciality and are born before the bones of the novel mammalian jaw joint form. These mammals need to rely on other mechanisms to allow them to feed. Here we show that this vital function is carried out by the earlier developing, cartilaginous incus of the middle ear, abutting the cranial base to form a cranio-mandibular articulation. The nature of this articulation varies between monotremes and marsupials, with monotremes retaining a double articulation, similar to that described in the fossil mammaliaform, Morganucodon, while marsupials use a versican rich matrix to stabilise the jaw against the cranial base. These findings provide novel insight into the evolution of mammals and the relationship between the jaw and ear.
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Free pdf:
Free pdf:
https://link.springer.com/content/pdf/10.1186/s42501-020-00057-x.pdfMiddle Palaeozoic vertebrate fossil occurrences are summarised for Australia, with reference to faunal connections between Asia and East Gondwana, as first indicated by fish distributions of Lower Devonian fossil sites. Major endemic groups discussed are pituriaspid (Australian) and galeaspid (Asian) agnathans, wuttagoonaspids (Australian) and antarctaspid (Antarctic, Australian, Asian) arthrodires, yunnanolepid and sinolepid antiarchs (South China, Indochina terrane, Australia), and early tetrapodomorphs (South China, Australia). More widespread groups that lived in shallow marine environments (lungfishes, buchanosteid arthrodires, antiarch Bothriolepis) also show species groups shared between South China and East Gondwana. Exchange of continental facies fishes (e.g. tristichopterid tetrapodomorphs) may have been interrupted by marine transgression in the Frasnian, but were restored in the late Famennian with the appearance of Grenfellaspis in eastern Australia, the only sinolepid antiarch known from outside Asia. The hypothesis of Gondwana dispersion and Asian accretion, to explain the collage of geological terranes forming modern east and southeast Asia, implies increasing dissimilarity with increasing age, but the Siluro-Devonian early vertebrate evidence is inconsistent with this. Previous cladistic analysis of Asian terranes predicted galeaspid agnathans on the Indochina terrane, and their subsequent discovery at Ly Hoa, Vietnam, confirms that Indochina and South China had come together across the Song Ma suture by Middle Devonian time.