Table 2.

Position and orientation of foramen magnum. Index calculated as the projected length opisthion–opisthocranion/projected length glabella–opisthocranion. Negative value for foramen orientation indicates anteroinferior orientation.

taxon/specimenFM position index (%)FM orientation (°)
Australopithecus afarensis
 A.L. 444-22416
 A.L. 333-45 (recon.)19
 A.L. 822-12314
Australopithecus africanus
 Sts. 51920
Australopithecus boisei
 OH 5247
 KNM-ER 4061813
 KNM-ER 13 75020
Australopithecus aethiopicus
 KNM-WT 17 00021
Homo sapiens (n = 10)31−8
Pan troglodytes male (n = 10)1218
Pan troglodytes female (n = 10)1420
Gorilla gorilla male (n = 10)727
Gorilla gorilla female (n = 10)1330