New dicynodonts (Therapsida, Anomodontia) from the Early Triassic of Laos: implications for the tetrapod recovery after the Permian–Triassic mass extinction and the paleobiogeography of Southeast Asian Blocks

Chloe Olivier (1) , Bernard Battail (2) , Sylvie Bourquin (3) , Camille Rossignol (4) , Jean-Sébastien Steyer (2) , Nour-Eddine Jalil (2)

1 iSTeP - Institut des Sciences de la Terre de Paris
2 CR2P - Centre de Recherche en Paléontologie - Paris
3 GR - Géosciences Rennes
4 UFOP - Universidade Federal de Ouro Preto

The dicynodonts are an emblematic group of herbivorous therapsids, which have survived the Permian–Triassic (PT) crisis. Laotian dicynodonts from stratigraphically well-constrained beds, using U–Pb on zircon dating, bring new insights into terrestrial faunas of Southeast Asia during the Early Triassic. They have already briefly been described but their phylogenetic relationships were never been investigated. Reexamination of the Laotian dicynodonts, three well-preserved skulls, indicates that they belong to two new species. Our phylogenetic analysis within Dicynodontia indicates that 1) gen. et sp. nov. 1 is closely related to some ”Dicynodon ”- grade taxa; and 2) gen. et sp. nov. 2 is a stem taxon to Kannemeyeriiformes. The phylogenetic affinities of these new Laotian dicynodonts allow to discuss about the recovery of the terrestrial tetrapods during the Early Triassic: the survival of a Permian lineage across the PT crisis and/or a rapid recovery with a new occurrence in the Early Triassic. The Laotian dicynodonts also shed new light on the debated paleogeographic issues concerning the evolution of Southeast Asia from the late Paleozoic to the early Mesozoic, particularly on the timing of the collision between the Indochina, the South China and the North China blocks. The Early Triassic age of the two new Laotian dicynodonts, their essentially terrestrial lifestyle, and the phylogenetic affinities between gen. et sp. nov. 2 and Early Triassic Chinese Kannemeyeriiformes, suppose a land connection between the Indochina Block and other dicynodont bearing continents as early as the Early Triassic.

Domains: Stratigraphy; Paleontology

Chloe Olivier, Bernard Battail, Sylvie Bourquin, Camille Rossignol, Jean-Sébastien Steyer, et al.. New dicynodonts (Therapsida, Anomodontia) from the Early Triassic of Laos: implications for the tetrapod recovery after the Permian–Triassic mass extinction and the paleobiogeography of Southeast Asian Blocks. 5th International Palaeontological Congress, Jul 2018, Paris, France. pp.660. ⟨insu-01906018⟩