The first geikiid dicynodont, Aulacephalodon kapoliwacela, sp. nov. (Therapsida, Anomodontia), from the upper Madumabisa Mudstone Formation, Zambia

The upper Madumabisa Mudstone Formation is a richly fossiliferous rock formation exposed in the Luangwa Basin in Zambia, with well-documented upper Permian vertebrate assemblages comparable to those of coeval basins in Tanzania and South Africa. The tetrapod communities of the upper Madumabisa Mudstone include 20 species of dicynodonts. Although most Permian dicynodont clades are represented in the upper Madumabisa Mudstone assemblages, the ornamented clade Geikiidae, which occurs in both the Karoo and Ruhuhu basins, has yet to be reliably reported in the Luangwa Basin; historical reports likely represent other cryptodont taxa. We report a new species of geikiid, Aulacephalodon kapoliwacela, sp. nov., known from both the lower and upper assemblages of the upper Madumabisa Mudstone Formation. This species closely resembles the abundant South African taxon Aulacephalodon bainii, including bearing robust tusks, bosses on the squamosals, and a tall ascending process of the jugal, but differs in the absence of a pineal boss and differing ontogenetic trajectories of the postfrontal and postcaniniform crests. We also provisionally rediagnose A. bainii using only characters visible in the holotype, and for the first time provide a diagnosis for the genus. Phylogenetic analysis supports a close relationship between Zambian and South African geikiids. Multiple juvenile individuals of A. kapoliwacela help clarify ontogenetic trends within Geikiidae, including differences in development and fusion of the postfrontal between geikiid species. Large wear facets on the tusks of some individuals indicate substrate-focused foraging behavior in Aulacephalodon.