Permian and Triassic Dicynodont (Therapsida: Anomodontia) Faunas of the Luangwa Basin, Zambia: Taxonomic Update and Implications for Dicynodont Biogeography and Biostratigraphy

Abstract

Dicynodont fossils were first collected in the Luangwa Basin, Zambia, in the 1920s, but limited detailed study and taxonomic uncertainty have obscured their biostratigraphic utility and their implications for topics such as dicynodont biogeography and the effects of the end-Permian extinction. Here we present a comprehensive taxonomic revision of the dicynodonts of the Luangwa Basin, taking into account specimens in all major museum collections and new material collected by our team in 2009. We recognize 14 dicynodont species from the Upper Permian Upper Madumabisa Mudstone: Pristerodon mackayi, Endothiodon sp., Diictodon feliceps, Compsodon helmoedi, Emydops sp., Dicynodontoides cf. D. nowacki, a new tusked cistecephalid, cf. Katumbia parringtoni, Kitchinganomodon crassus, Oudenodon bainii, Odontocyclops whaitsi, Dicynodon huenei, Syops vanhoepeni, and a new lystrosaurid. Previous reports of Lystrosaurus in the basin appear to be in error. In addition, we found no significant partitioning of dicynodont taxa in the northern and southern parts of the basin, despite substantial differences in preservation, indicating the presence of a single faunal assemblage in the Upper Permian. The Madumabisa dicynodont assemblage is best correlated with the Cistecephalus Assemblage Zone of South Africa. The shared presence of Dicynodon huenei and possibly Katumbia in the Luangwa Basin and the Ruhuhu Basin of Tanzania suggests that the Tanzanian Usili Formation also can be correlated with the Cistecephalus zone. Interestingly, the Madumabisa assemblage from Zambia is more similar to the coeval assemblage from South Africa, despite its closer geographic proximity to Tanzania. The Karoo and Ruhuhu basins also include more endemic species in the Permian than the Luangwa Basin. The Middle Triassic Ntawere Formation preserves four dicynodont species (Kannemeyeria lophorhinus, “Kannemeyeria” latirostris, Zambiasaurus submersus, Sangusaurus edentatus), which occur at two stratigraphic levels. The lower Ntawere assemblage resembles that of the Omingonde Formation of Namibia in the presence of Kannemeyeria lophorhinus and potentially Dolichuranus (if “K.” latirostris represents this taxon). The upper Ntawere assemblage shares the genus Sangusaurus with that of the Manda beds of Tanzania and includes the endemic Zambiasaurus. Comparisons of these assemblages to the Omingonde and Manda suggest that both are best correlated with the Cynognathus C subzone. When combined with data on other tetrapod taxa, our revised dicynodont assemblages contribute to an emerging picture of broad faunal similarity in southern and eastern Africa during the Late Permian, and increasing differentiation between the South African and other Karoo basins following the end-Permian extinction.