Browsing by Author "Rossie, B. James"

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    Additional hominoid fossils from the early Miocene of the Lothidok Formation, Kenya
    (Wiley, 2022-07-24) Rossie, B. James; Cote, Susanne
    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.
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    Oldest evidence of abundant C4 grasses and habitat heterogeneity in eastern Africa
    (Science, 2023-04-13) Peppe, J. Daniel; Cote, M. Susanne; Deino, L. Alan; Fox, L. David; Kingston, D. John; Kinyanjui, N. Rahab; Lukens, E. William; MacLatchy, M. Laura; Novello, Alice; Strömberg, A.E. Caroline; Driese, G. Steven; Garrett, D. Nicole; Hillis, R. Kayla; Jacobs, F. Bonnie; Jenkins, E.H. Kirsten; Kityo, Robert; Lehmann, Thomas; Manthi, K. Fredrick; Mbua, N. Emma; Michel, A. Lauren; Miller, R. Ellen; Mugume, A.T. Amon; Muteti, M. Samuel; Nengo, O. Isaiah; Kennedy, O. Oginga; Phelps, R. Samuel; Polissar, Pratigya; Rossie, B. James; Stevens, J. Nancy; Uno, T. Kevin; McNulty, P. Kieran
    The assembly of Africa’s iconic C4 grassland ecosystems is central to evolutionary interpretations of many mammal lineages, including hominins. C4 grasses are thought to have become ecologically dominant in Africa only after Ma. However, paleobotanical records older than 10 Ma are sparse, limiting assessment of the timing and nature of C4 biomass expansion. This study utilizes a multiproxy design to document vegetation structure from nine Early Miocene mammal site complexes across eastern Africa. Results demonstrate that, between ~21–17 Ma, C4 grasses were locally abundant, contributing to heterogeneous habitats ranging from forests to wooded grasslands. These data push back the oldest evidence of C4 grass5 dominated habitats in Africa – and globally – by more than 10 Myr, calling for revised paleoecological interpretations of mammalian evolution.