Middle Permian therocephalians from the South African Karoo.

ABDALA, F.; DAY, M; RUBIDGE, B. S.

Kazan

Congreso; XVIII International Congress on Carboniferous and Permian; 2015

Russian Academy of Sciences, Interdepartmental Stratigraphical Committee of Russia, Carboniferous and Permian subcommissions of Russia, Kazan Federal University, Moscow State University, All-Russian Research Geological Institute, International subcommissi

The Permian was a very important period in the Earth history when modern trophic pyramid structures became established in terrestrial environments. One of the key places to investigate this particular time period is the Beaufort Group of the Karoo Basin, South Africa, which records a continuous sequence of continental deposition ranging from the Middle Permian to the Middle Triassic (a range of approximately 30 million years). The Beaufort group is divided in sevenassemblage zones (AZs), defined by their fauna. The three oldest of these are the Eodicynodon, Tapinocephalus and Pristerognathus AZs, which represent the Middle Permian and the transition to the Upper Permian. Therocephalians are a heterogeneous group first recorded in the Middle Permian of the Karoo Basin. Early representatives of this group reached large sizes (dorsal skull length of 370 mm) and some were among the top predators in Middle Permian faunas from South Africa. There are two records of small to medium sized scylacosaurid therocephalians in the Eodicynodon AZ representing the oldest members of this group in the world. The two therocephalian families classically represented in the Middle Permian, scylacosaurids and lycosuchids, were abundant inthe Tapinocephalus AZ, whereas the fauna of the Pristerognathus AZ shows a transition with a reduction in the species richness of the basal families. In this AZ are also recorded the first appearance of the smaller therocephalian taxa Hofmeyriidae and Ictidosuchidae, that would become well established in the younger Late Permian faunas. In this work we will present a reanalysisof the taxonomy and the stratigraphic and geographic distribution of the Middle Permian therocephalians from the Karoo Basin, which are crucial for studies of biostratigraphy and of early therocephalian evolution.