Some additional morphological and metrical observations on Pan brain casts and their relevance to the Taung endocast

Using an increased sample of chimpanzee brains and brain casts, 32 hemispheres were measured to determine the variability of OP-FP (occipital-pole) and OP-LS (occipital pole-lunate sulcus) arc dimensions and their ratios. The Taung endocast was remeasured to test Falk's assertions that the lunate sulcus is in a pongid position. The average ratio for the chimpanzee brains was 0.218, a value more than 2+ S.D.'s posterior to Falk's placement of the lunate sulcus on the Taung specimen. It is suggested that the chimpanzee and Taung occipital poles have a different morphometric pattern, the former being coincident with the caudal end of the LC (lateral calcarine) fissure. The Taung OP-LS arc consistently measured at least 42 mm, and not 40 mm as claimed by Falk.