American Journal of Physical Anthropology 111:(S30): 212
Establishing the polarity of temporal bone morphology in African hominoids using geometric morphometrics.
The hominoid temporal bone offers a complex array of morphology and is often preserved in (he fossil record. It has demonstrated utility in systematics, but quantitative studies have been limited mainly to univariate comparisons. In this study we use techniques of 3D geometric morphometrics to 1) quantify differences among extant African hominoid species and 2) compare them to early hominins to establish which extant species, if any, most closely corresponds to the primitive morphotype for the hominin clade.
We chose 23 temporal bone landmarks based on repeatability and relevance to qualitative temporal hone characters commonly used in hominin systematics. Crania were digitized using a Microscribe 3D portable digitizer. Samples include 125 individuals divided equally between Homo sapiens, Gorilla g. gorilla. and Pan troglodytes, as well as five casts of fossil hominins, representing Australopithecus afarensis, A. africanus, A. boisei, and H. habilis.
Using the program Morphologika (O'Higgins and Jones, 1998), we conducted a relative warp analysis to establish interspecific differences and the bounds of intraspecific variation. This effectively discriminates among species, the major source of variation being between humans and apes. Thin plate spline analyses show that, for example, African ape temporal bones are relatively broader mediolaterally than those of humans. The tympanic element extends farther laterally in apes, especially in gorillas. The human glenoid fossa is larger relative to the size of the temporal bone as a whole. and deeper, but the anterior portion of the articular eminence is reduced. Great ape temporal bones are also distinct from each other. Gorillas lack the extensive preglenoid surface of chimpanzees, and their mastoid processes are less medially inflected. Thus, geometric methods express and quantify features hitherto discussed from a qualitative, often subjective, perspective. Fossil hominins are distributed roughly between the gorilla and human clusters. A.L. 444 2 of A. afarensis falls close to the gorilla female distribution. In addition to demonstrating that gorillas and chimpanzees are distinct in temporal bone morphology, we conclude that chimpanzees are autapomorphic in several ways and not a good model for early hominin temporal bone shape. Funded by Arizona State University and IHO.