StW 505

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StW 505, known as Mr. Ples, is the most complete Australopithecus africanus skull found at Sterkfontein Member 4 in Gauteng, South Africa. Discovered in 1989, it was found in the rock and is larger than most Sterkfontein skulls with similar parts. The fossil has suffered breakage and deformation, especially on the face and the top, but many diagnostic features remain visible.

Key traits—such as the strong front of the face, the straight lower edge of the cheekbone, and the skull base pattern—match A. africanus and help distinguish it from other ancient humans. Some features overlap with early Homo and/or A. robustus, but the full set of traits fits A. africanus best. StW 505 adds new variation to Sterkfontein material, including pronounced eyebrow ridges and a prominent forehead area, probably due to sexual dimorphism. Overall, the skull shows similarities between A. africanus and early Homo and suggests that differences between A. afarensis and A. africanus may be smaller than previously thought.