High-resolution computed tomography study of the cranium of a fossil anthropoid primate, Parapithecus grangeri: new insights into the evolutionary history of primate sensory systems.
Extant anthropoids have large brains, small olfactory bulbs, and high-acuity vision compared with other primates. The relative timing of the evolution of these characteristics may have important implications for brain evolution. Here computed tomography is used to examine the cranium of a fossil anthropoid, Parapithecus grangeri. It is found that P. grangeri had a relatively small brain compared with living primates. In addition, it had an olfactory bulb in the middle of the range for living primates. Methods for relating optic foramen area and other cranial measurements to acuity are discussed. Multiple regression is used to estimate retinal ganglion cell number in P. grangeri. Given currently available comparative data, P. grangeri seems to have had retinal ganglion cell counts intermediate for living primates, overlapping with the upper end of the range for strepsirrhines and possibly with the lower end for anthropoids.
Biology Division, California Institute of Technology, Pasadena, California, USA. ebush@bsd.uchicago.edu
Eliot C
EC
Bush
Elwyn L
EL
Simons
John M
JM
Allman
D000818:Animals; D005075:Biological Evolution; D001921:Brain / Q000033:anatomy & histology* / Q000502:physiology; D002452:Cell Count; D005580:Fossils; D000882:Haplorhini / Q000033:anatomy & histology* / Q000502:physiology; D007091:Image Processing, Computer-Assisted; D009830:Olfactory Bulb / Q000033:anatomy & histology / Q000502:physiology; D009833:Olfactory Pathways / Q000033:anatomy & histology* / Q000502:physiology; D009900:Optic Nerve / Q000033:anatomy & histology / Q000502:physiology; D010163:Paleontology; D012165:Retinal Ganglion Cells / Q000166:cytology / Q000502:physiology; D012886:Skull / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000502:physiology; D012903:Smell / Q000502:physiology; D014057:Tomography, X-Ray Computed; D014785:Vision, Ocular / Q000502:physiology; D014792:Visual Acuity / Q000502:physiology; D014795:Visual Pathways / Q000033:anatomy & histology* / Q000502:physiology