Department of Anthropology, Stony Brook University, Stony Brook, NY 11794, USA.
Department of Anthropology, Washington University in St. Louis, St. Louis, MO 63130, USA.
J Hum Evol. 2024 Jul;192:103519. doi: 10.1016/j.jhevol.2024.103519. Epub 2024 Jun 5.
An ape partial postcranial skeleton (KNM-NP 64631) was recovered during the 2015-2021 field seasons at Napudet, a Middle Miocene (∼13 Ma) locality in northern Kenya. Bony elements representing the shoulder, elbow, hip, and ankle joints, thoracic and lumbar vertebral column, and hands and feet, offer valuable new information about the body plan and positional behaviors of Middle Miocene apes. Body mass estimates from femoral head dimensions suggest that the KNM-NP 64631 individual was smaller-bodied (c. 13-17 kg) than some Miocene taxa from eastern Africa, including Ekembo nyanzae, and probably Equatorius africanus or Kenyapithecus wickeri, and was more comparable to smaller-bodied male Nacholapithecus kerioi individuals. Similar to many Miocene apes, the KNM-NP 64631 individual had hip and hallucal tarsometatarsal joints reflecting habitual hindlimb loading in a variety of postures, a distal tibia with a large medial malleolus, an inflated humeral capitulum, probably a long lumbar spine, and a long pollical proximal phalanx relative to femoral head dimensions. The KNM-NP 64631 individual departs from most Early Miocene apes in its possession of a more steeply beveled radial head and deeper humeral zona conoidea, reflecting enhanced supinating-pronating abilities at the humeroradial joint. The KNM-NP 64631 individual also differs from Early Miocene Ekembo heseloni in having a larger elbow joint (inferred from radial head size) relative to the mediolateral width of the lumbar vertebral bodies and a more asymmetrical talar trochlea, and in these ways recalls inferred joint proportions for, and talocrural morphology of, N. kerioi. Compared to most Early Miocene apes, the KNM-NP 64631 individual likely relied on more forelimb-dominated arboreal behaviors, perhaps including vertical climbing (e.g., extended elbow, hoisting). Moreover, the Napudet ape partial postcranial skeleton suggests that an arboreally adapted body plan characterized by relatively large (here, based on joint size) forelimbs, but lacking orthograde suspensory adaptations, may not have been 'unusual' among Middle Miocene apes.
一个部分猿类后肢骨骼（KNM-NP 64631）是在 2015 年至 2021 年期间在肯尼亚北部中中新世（约 1300 万年前）的纳普杜特发现的。代表肩部、肘部、臀部和踝关节、胸腰椎柱以及手和脚的骨骼元素提供了关于中中新世猿类身体结构和姿势行为的宝贵新信息。从股骨头尺寸估计的体重表明，KNM-NP 64631 个体比东非的一些中新世分类群体型更小（约 13-17 公斤），包括 Ekembo nyanzae，可能还有 Equatorius africanus 或 Kenyapithecus wickeri，与体型较小的雄性 Nacholapithecus kerioi 个体更为相似。与许多中新世猿类一样，KNM-NP 64631 个体的髋部和跟骨跗跖骨关节反映了在各种姿势下习惯性的后肢承重，胫骨远端有一个大的内踝，肱骨滑车膨胀，可能有一个长的腰椎，以及相对于股骨头尺寸的长的拇指近节指骨。KNM-NP 64631 个体与大多数早中新世猿类不同，其桡骨头更陡峭倾斜，肱骨滑车区更深，反映了在肱桡关节处旋前-旋后能力增强。与早中新世的 Ekembo heseloni 相比，KNM-NP 64631 个体的肘关节（根据桡骨头大小推断）相对腰椎体的内外宽度更大，距骨滑车更不对称，在这些方面，它让人想起对 N. kerioi 的关节比例和距下关节形态的推断。与大多数早中新世猿类相比，KNM-NP 64631 个体可能更依赖于以前肢为主导的树栖行为，可能包括垂直攀爬（例如，伸展的肘部，提起）。此外，纳普杜特猿类部分后肢骨骼表明，一种以相对较大的前肢（这里基于关节大小）为特征的适应树栖的身体结构，但缺乏垂直悬挂的适应，在中中新世猿类中可能并不“罕见”。
