An unusual shark assemblage from the Ladinian-Carnian interval of South China

A detailed taxonomic study of a diverse chondrichthyan fauna from the Ladinian-Carnian (Middle-Late Triassic) interval at Nimaigu locality in Guizhou Province, South China is presented. Six taxa are described, two of which are assigned to Elasmobranchii incertae sedis (aff. Rosaodus sp., Rosaodus xingyiensis gen. et sp. nov.) and three to the Euselachii (Euselachii gen. et sp. indet., Favusodus orientalis gen. et sp. nov., Keichouodus nimaiguensis gen. et sp. nov.), while the last one represents a possible Holocephali (aff. Arctacanthus sp.). Their stratigraphic distribution is documented on a bed-by-bed basis. This fauna is unusual because it is dominated by sharks with a cladodont-like dentition (which were barely known after the end-Permian mass extinction), and because it is almost devoid of durophagous euselachians, which makes it different from all other contemporaneous shark faunas worldwide. Transitional features are documented between 'cladodont' teeth and those of neoselachian sharks, which provide new insights into the replacement pattern of ancient sharks by modern ones.