The hominid temporal bone: Ontogeny and phylogenetic implications

The temporal bone, because of the durability of the petrous and mastoid portions (thus increasing chance for recovery) and its proven utility in primate systematics, offers a valuable resource for those interested in hominid evolution. Most often, though, the developmental processes behind the adult form are neglected. The current work is a detailed examination of the development and anatomy of the hominid and pongid temporal bone. Recent fossil finds have initiated a reevaluation of species diagnoses for all hominid taxa. New approaches to paleospecies recognition will benefit from a thorough understanding of the anatomy and development of the areas under discussion. Ontogeny and the concept of homology have been historically linked since at least the time of Darwin. Recent anthropological work has again emphasized the value of ontogenetic data in determining homologous status primarily in aspects of dental growth (e.g., Martin 1985; Wood 1988). The current study focuses on three aspects of the temporal bone in both extant hominoids and fossil hominids: the developmental process of pneumatization; the anatomy of the mandibular fossa and surrounding region; and an analysis of sutural closure patterns. External morphology is examined in age-graded series of extant pongids and modern humans as well as African Plio-Pleistocene hominid fossils (from Kenya, Tanzania, Ethiopia, and South Africa). Detailed analysis of internal morphology was also performed using standard radiographs of extant and fossil material. Additionally, CT images were made on a developmental series of pongid skulls to examine the influence of temporal bone pneumatization. Special attention is paid to the range of variation present, and to the mechanisms which create that variation. Subsequent discussions focus on current methods of phylogenetic reconstruction and on the application of temporal bone anatomy to the reconstruction of hominid phylogeny.