Additional hominoid fossils from the early Miocene of the Lothidok Formation, Kenya

Objectives: Hominoid fossils are abundant at early Miocene fossil sites in the Lothidok Range, located directly west of Lake Turkana in northern Kenya. The West Turkana Miocene Project (WTMP) has worked in the Lothidok Range since 2008 with the goal of further elucidating the paleobiology of the hominoids through the recovery of new specimens and detailed documentation of their paleoecological context. To date our research has focused largely on the Kalodirr and Moruorot Site Complexes, both radiometrically dated to ~17.5–16.8 Ma. Materials and Methods: Our ongoing fieldwork at the Kalodirr Site Complex resulted in the discovery of new dentognathic specimens of the three previously identified species of fossil hominoids—Turkanapithecus kalakolensis, Simiolus enjiessi, and Afropithecus turkanensis. Results: A new mandible and an isolated M₃ of T. kalakolensis from Kalodirr further clarify the lower molar morphology of the species and permit identification of KNM-MO 1 as a mandible of T. kalakolensis. A new mandible of S. enjiessi provides evidence of the relative proportions of the first and second lower molars. A new male specimen of A. turkanensis shows unusual P₄ morphology that may be a developmental anomaly or a previously unknown morphological variant. Discussion: An improved understanding of the lower molar morphology of T. kalakolensis further strengthens its identification as a nyanzapithecine. Our new specimens and subsequent re-identification of existing collections makes it clear that all three Lothidok hominoids are known from both the Moruorot and Kalodirr Site Complexes. The Lothidok Range holds great promise for further documenting hominoid evolution.