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| Laosuchus naga
Arbez, Sidor & Steyer, 2019
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Abstract
Chroniosuchians were a clade of non-amniotic tetrapods known from the Guadalupian (middle Permian) to Late Triassic, mainly from Russia and China. The rarity of complete or articulated remains means that relatively little is known about this group in terms of its anatomy, palaeobiology or evolutionary history. Based on a nearly complete skull with a left hemimandible, we describe the first chroniosuchian from Laos from rocks preserving the Permian–Triassic boundary in the Luang Prabang Basin, which is located on the tectonic Indochina Block. This specimen is referred to a new genus and species, Laosuchus naga, based on numerous diagnostic features, including an extremely reduced pineal foramen; absence of palatal dentition; well-developed transverse flange of the pterygoid that contacts the maxilla; internal crest on and above the dorsal side the palate; otic notch closed by the tabular horn and the posterior part of the squamosal, forming a continuous wall; thin and high ventromedial ridge on parasphenoid. A phylogenetic analysis of 51 characters and 25 taxa reveals a basal position for Laosuchus naga among Chroniosuchia. In addition, CT scan data reveal internal structures and provide new insights about the anatomy and palaeobiology of chroniosuchians. Laosuchus naga was likely amphibious and spent most of its time in water, rather than in terrestrial environments. As chroniosuchians are non-marine tetrapods previously known on the North China Block, South China Block and Laurussia, the occurrence of Laosuchus naga on the Indochina Block supports the hypothesis of physical connections between all these tectonic plates by the time of the Permo–Triassic boundary.
Keywords: braincase, Reptiliomorpha, sensory system, palaeobiogeography, phylogeny, tomography
Systematic palaeontology
Superclass Tetrapoda Goodrich, 1930
Order Reptiliomorpha Säve-Söderbergh, 1934 (sensu Benton, 2004)
Suborder Chroniosuchia Tatarinov, 1972 (sensu Witzmann & Schoch, 2017)
Family incertae sedis
Genus Laosuchus gen. nov
Etymology. From the country of origin (Laos) and the
ancient Greek soukhos, ‘crocodile’, for its crocodilian-like
appearance.
Laosuchus naga sp. nov.
Etymology. From the mythological monster ‘Naga’ (or
Phaya Naga) believed to live in the Mekong River,
which is close to the type locality.
Thomas Arbez, Christian A. Sidor and J.-Sébastien Steyer. 2019. Laosuchus naga gen. et sp. nov., A New Chroniosuchian from South-East Asia (Laos) with Internal Structures Revealed by micro-CT Scan and Discussion of its Palaeobiology. Journal of Systematic Palaeontology. 17(14); 1165-1182. DOI: 10.1080/14772019.2018.1504827
La forme de la Pangée mieux comprise grâce à un fossile de proto-reptile sciencesetavenir.fr/archeo-paleo/paleontologie/tectonique-un-fossile-eclaire-la-forme-de-la-pangee_128713 via @Sciences_Avenir
