New insights into the giant mustelids (Mammalia, Carnivora, Mustelidae) from Langebaanweg fossil site (West Coast Fossil Park, South Africa, early Pliocene)

Giant mustelids are a paraphyletic group of mustelids found in the Neogene of Eurasia, Africa and North America. Most are known largely from dental remains, with their postcranial skeleton mostly unknown. Here, we describe new craniodental and postcranial remains of the large lutrine Sivaonyx hendeyi and the leopard-size gulonine Plesiogulo aff. monspessulanus from the early Pliocene site Langebaanweg, South Africa. The new material of the endemic S. hendeyi, includes upper incisors and premolars, and fragmentary humerus, ulna and a complete astragalus. Its postcrania shares more traits with the living Aonyx capensis than the late Miocene Sivaonyx beyi from Chad. Sivaonyx hendeyi could therefore be tentatively interpreted as a relatively more aquatic taxon than the Chadian species, comparable to A. capensis. The new specimens of Plesiogulo comprise two edentulous maxillae, including one of a juvenile individual with incomplete decidual dentition, and a fragmentary forelimb of an adult individual. The new dental measurements point to this form being amongst the largest specimens of the genus. Both P3-4 differs from the very large species Plesiogulo botori from late Miocene of Kenya and Ethiopia. This confirms the existence of two distinct large species of Plesiogulo in Africa during the Mio/Pliocene, P. botori in the Late Miocene of Eastern Africa (6.1–5.5 Ma) and Plesiogulo aff. monspessulanus at the beginning of the Pliocene in southern Africa (5.2 Ma). Lastly, we report for the first time the presence of both Sivaonyx and Plesiogulo in MPPM and LQSM at Langebaanweg, suggesting that the differences observed from the locality may be produced by sedimentation or sampling biases instead of temporal replacement within the carnivoran guild.