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[dinosaur] Clevosaurus cambrica, new species from Triassic of Wales + Tetrapod burrows from Triassic ChaÃares Formation





Ben Creisler
bcreisler@gmail.com

New non-dino papers:

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Clevosaurus cambrica sp. nov.

Emily Keeble, David I. Whiteside & Michael J. Benton (2018)
The terrestrial fauna of the Late Triassic Pant-y-ffynnon Quarry fissures, South Wales, UK and a new species of Clevosaurus (Lepidosauria: Rhynchocephalia)Original Research Article
Proceedings of the Geologists' Association (advance online publication)
doi:Â https://doi.org/10.1016/j.pgeola.2017.11.001
https://www.sciencedirect.com/science/article/pii/S0016787817301529



Pant-y-ffynnon Quarry in South Wales yielded a rich cache of fossils in the early 1950s, including articulated specimens of new species (the small sauropodomorph dinosaur Pantydraco caducus and the crocodylomorph Terrestrisuchus gracilis), but no substantial study of the wider fauna of the Pant-y-ffynnon fissure systems has been published. Here, our overview of existing specimens, a few described but mostly undescribed, as well as freshly processed material, provides a comprehensive picture of the Pant-y-ffynnon palaeo-island of the Late Triassic. This was an island with a relatively impoverished fauna dominated by small clevosaurs (rhynchocephalians), including a new species, Clevosaurus cambrica, described here from a partially articulated specimen and isolated bones. The new species has a dental morphology that is intermediate between the Late Triassic Clevosaurus hudsoni, from Cromhall Quarry to the east, and the younger C. convallis from Pant Quarry to the west, suggesting adaptive radiation of clevosaurs in the palaeo-archipelago. The larger reptiles on the palaeo-island do not exceed 1.5âm in length, including a small carnivorous crocodylomorph, Terrestrisuchus, and a possible example of insular dwarfism in the basal dinosaur Pantydraco.


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Lucas E. Fiorelli, SebastiÃn Rocher, AgustÃn G. Martinelli, MartÃn D. Ezcurra, E. MartÃn Hechenleitner & Miguel Ezpeleta (2018)
Tetrapod burrows from the MiddleâUpper Triassic ChaÃares Formation (La Rioja, Argentina) and its palaeoecological implications.
Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication)
doi: https://doi.org/10.1016/j.palaeo.2018.01.026
https://www.sciencedirect.com/science/article/pii/S0031018217309963





Highlights

First report of tetrapod burrows from the MiddleâUpper Triassic ChaÃares Formation
The burrows are numerous, complex, and preserved within incipient palaeosols formed in semiarid conditions
The new record of tetrapod burrows is associated with a new Triassic fauna with a Ladinian-Carnian age.
The burrows of the ChaÃares Formation were probably produced by small eucynodonts.

Abstract


We describe tetrapod burrows from the uppermost Middleâlower Upper Triassic (latest Ladinianâearly Carnian) ChaÃares Formation (Ischigualasto-Villa UniÃn Basin), La Rioja Province, northwestern Argentina. The burrows were found in different localities of the unit, but restricted to the lowermost 17âm of the formation. They occur at the same interval as a tetrapod assemblage composed of erpetosuchid and basal paracrocodylomorph pseudosuchians, basal traversodontid and chiniquodontid eucynodontians, and stenaulorhynchine rhynchosaurids. This assemblage differs from the typical ChaÃares fauna that occurs in stratigraphically higher levels. The burrows were found within the deposits of moderately developed palaeosols formed in volcanically-influenced braided fluvial facies under semi-arid climate conditions. The burrow systems are cylindrical to sub-cylindrical in cross-section, up to 25âcm in diameter, and characterized by long, multiple branching tunnels, several metres long, that meander horizontally or are slightly inclined (<30Â), forming a complex network that is a result of passive fill of a previously open burrow. In general, these structures have a similar architecture and three-dimensional organization to those previously described from the upper parts of the Ischigualasto Formation in the same basin. It is hypothesised that some of these burrows were formed by small eucynodonts (e.g., basal traversodontids, chiniquodontids), and their co-occurrence with diverse, medium to large pseudosuchian predators (e.g., Luperosuchus, Tarjadia), suggests these non-mammaliaform eucynodonts would excavate burrows to live and avoid climate-stress conditions and/or predation. The new discovery of burrows in the ChaÃares Formation sheds light on the evolution of the palaeoecology of mammaliaform precursors during the dawn of the archosaur domain.




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