The first skull of Australopithecus boisei

Australopithecus boisei was first described from a cranium recovered in 1959 from Olduvai Gorge, Tanzania. This and subsequent finds, mostly from Kenya's Turkana basin, resulted in its characterization as a specialized Australopithecus species with a hyper-robust masticatory apparatus. A distinct A. boisei facial morphology has been emphasized to differentiate robust Australopithecus lineages from East and South Africa. A preference for closed and/or wet habitats has been hypothesized. Here we report some new A. boisei specimens, including the taxon's first cranium and associated mandible, from Konso, Ethiopia. These fossils extend the known geographical range of A. boisei. They provide clear evidence for the coexistence of A. boisei and Homo erectus within a predominantly dry grassland environment. The A. boisei specimens from Konso demonstrate considerable morphological variation within the species. The unexpected combination of cranial and facial features of this skull cautions against the excessive taxonomic splitting of early hominids based on morphological detail documented in small and/or geographically restricted samples.