Sungeodon kimkraemerae n. gen. n. sp., the oldest kannemeyeriiform (Therapsida, Dicynodontia) and its implications for the early diversification of large herbivores after the P/T boundary

Abstract

Listen

Translate article

The dicynodont Sungeodon kimkraemerae n. gen. n. sp. is described on the basis of a skull from the Lower Triassic Jiucaiyuan Formation of Dalongkou (Junggar Basin, Xinjiang Uygur Autonomous Region, People’s Republic of China). It is the first representative of Kannemeyeriiformes from the earliest Triassic. Kannemeyeriiforms were the predominant clade of Triassic dicynodonts, which constituted a major component of terrestrial Triassic ecosystems. The new taxon helps closing one of the most significant gaps in the fossil record of dicynodonts, since stem-kannemeyeriiforms are known from the Late Permian, whereas the first true kannemeyeriiforms previously known are late Early Triassic in age. After a phylogenetic analysis Sungeodon belongs to the family Stahleckeriidae. Therefore, the Stahleckeriidae may not have had its origin in Africa as previously assumed, but in Central Asia. More importantly, Sungeodon also suggests that the major radiation of kannemeyeriiform dicynodonts, including the emergence of all relevant subgroups of this clade, occurred not later than in the Early Triassic, soon after the end-Permian extinction. To date, only few dicynodont taxa are known from the earliest Triassic, none of which are kannemeyeriiforms. The addition of Sungeodon confirms previous predictions that our knowledge of Early Triassic dicynodont diversity and evolution is far from being complete, and that new discoveries from historically low-sampled geographic regions may fill this gap. A rapid post-extinction diversification of kannemeyeriiforms also fits with the emerging picture from other clades, such as archosaurs, of a rapid recovery from the end-Permian event in the terrestrial realm.