Insights into the lower torso in late Miocene hominoid <i>Oreopithecus bambolii</i>.

Abstract

<i>Oreopithecus bambolii</i> (8.3-6.7 million years old) is the latest known hominoid from Europe, dating to approximately the divergence time of the <i>Pan</i>-hominin lineages. Despite being the most complete nonhominin hominoid in the fossil record, the <i>O. bambolii</i> skeleton IGF 11778 has been, for decades, at the center of intense debate regarding the species' locomotor behavior, phylogenetic position, insular paleoenvironment, and utility as a model for early hominin anatomy. Here we investigate features of the IGF 11778 pelvis and lumbar region based on torso preparations and supplemented by other <i>O. bambolii</i> material. We correct several crucial interpretations relating to the IGF 11778 anterior inferior iliac spine and lumbar vertebrae structure and identifications. We find that features of the early hominin <i>Ardipithecus ramidus</i> torso that are argued to have permitted both lordosis and pelvic stabilization during upright walking are not present in <i>O. bambolii</i> However, <i>O. bambolii</i> also lacks the complete reorganization for torso stiffness seen in extant great apes (i.e., living members of the Hominidae), and is more similar to large hylobatids in certain aspects of torso form. We discuss the major implications of the <i>O. bambolii</i> lower torso anatomy and how <i>O. bambolii</i> informs scenarios of hominoid evolution.