Postcranial anatomy of the long bones of colobines (Mammalia, Primates) from the Plio-Pleistocene Omo Group deposits (Shungura Formation and Usno Formation, 1967-2018 field campaigns, Lower Omo Valley, Ethiopia)

Our knowledge of the functional and taxonomic diversity of the fossil colobine fauna (Colobinae Jerdon, 1867) from the Lower Omo Valley is based only on craniodental remains. Here we describe postcranial specimens of fossil colobines from the Usno and Shungura Formations, and provide in-depth insights into their functional anatomy and taxonomy. Comparisons with previously described fossil colobine specimens from eastern Africa led us to identify specimens similar to Paracolobus mutiwa Leakey, 1982 and Rhinocolobus turkanaensis Leakey, 1982. Our results highlight the mixed locomotor substrate preferences of Paracolobus mutiwa and add new insights regarding its locomotor behaviors by identifying anatomical characteristics of the forelimb associated with climbing. Postcranial remains reminiscent of Rhinocolobus confirm the peculiar elbow morphology of this taxon and its apparent preference for arboreal substrates. We also document femoral, humeral, and tibial specimens with arboreal traits similar in size and morphology to extant Colobus Illiger, 1811 in Member L of the Shungura Formation. By providing these new data on the colobine paleocommunity from Shungura, our results contribute to the understanding of the biotic context surrounding Plio-Pleistocene faunas of the Turkana Depression and pave the way for future ecomorphological analyses.