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Pelvic evidence for taxonomic heterogeneity within Australopithecus at Sterkfontein Member 4 (South Africa)

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Fornai C, Krenn V, Webb N, Haeusler M,
Project Birth and human evolution - implications from computer-assisted reconstructions
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Original article (peer-reviewed)

Journal American Journal of Physical Anthropology
Volume (Issue) 171(S69)
Page(s) 88
Title of proceedings American Journal of Physical Anthropology

Open Access

URL https://onlinelibrary.wiley.com/toc/10968644/2020/171/4
Type of Open Access Publisher (Gold Open Access)

Abstract

Recent debate on the StW 573 skeleton from Sterkfontein Member 2, South Africa, has reignited discussion regarding taxonomic heterogeneity within the Australopithecus africanus hypodigm. Here, we compare the alleged female Sts 14 pelvis and a new virtual reconstruction of the presumed male StW 431 pelvis from Sterkfontein Member 4 (2.6 to 2.1 Ma). After realignment of the fragments, the StW 431 ilium and ischiopubic ramus were restored using the Sts 14 and A.L. 288-1 (A. afarensis) hipbones as templates, based on landmark-based morphing techniques. The well-preserved upper sacrum and sacroiliac joint allowed us to con?dently align the pelvic elements. A preliminary GM analysis using 24 landmarks suggested that the morphological distance between the StW 431 and Sts 14 hipbones did not exceed the intraspeci?c variation of the extant species within a comparative sample of 40 adult and subadult modern humans, 34 chimpanzees, 44 gorillas and 29 orangutans. Nevertheless, based on our pelvic reconstruction, StW 431 and Sts 14 showed remarkable differences mainly in the cranio-caudal position of the sacroiliac joint and ventro-dorsal orientation of the ilia. This cannot be fully explained by allometry, different developmental age or sexual dimorphism and thus might re?ect distinct functional adaptations in the StW 431 and Sts 14 pelves. Combined with the profound morphological divergence between the StW 431 and Sts 14 sacra—which were larger only in 2% of all possible pairwise comparisons within a worldwide modern human sample of 76 sacra—our ?ndings suggest that these individuals were likely members of different taxa.
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