First hominin fossils from Milner Hall, Sterkfontein, South Africa.
Sterkfontein (South Africa) is famous for its large samples of hominin fossils, including an immense store of Australopithecus specimens (Broom et al., 1950; Clarke, 2013) from Member 4 of the cave's sedimentary sequence, which is designated as the Sterkfontein Formation (Partridge, 1978). In addition, Member 5 of the Sterkfontein Formation has yielded fossils of Homo ergaster and Paranthropus (Australopithecus) robustus, as well as behaviorally informative assemblages of Oldowan and Acheulean artifacts (Kuman, 1994a,b; Kuman and Clarke, 2000).
Less well-known than Members 4 and 5 are the fossil- and artifact-bearing deposits of Milner Hall (MH), a deep underground chamber of Sterkfontein that extends ~100 m in a roughly easte west direction (Wilkinson, 1983; Martini et al., 2003, Fig. 1). The Central Underground Deposits (CUD) comprise an expansive area at the eastern end of MH, where the convergence of several dolomitic faults (Wilkinson, 1983) has resulted in the development of numerous, closely spaced openings that articulate the MH with other parts of the underground network and the landscape surface. The deposits formed through these openings preserve a record of multiple generations of sediment infilling, erosion and collapse, as well as speleothem deposition (Stratford, 2011, Stratford et al., 2012, Stratford et al., 2014). Stratford (2011) began excavations in the CUD in 2008–2009, which exposed three stratigraphically distinct fossil assemblages, with faunal elements that indicate a mid-Pliocene to early Pleistocene age for each (Stratford, 2011, Stratford et al., 2012, Stratford et al., 2014). Here, we report on two hominin fossils excavated recently from the T1 depositional unit of the CUD excavation site, STK-MH1, during a new round of work in December 2014. These specimens are not only the first hominin fossils to be recovered in situ from MH, but their evocative morphologies present intriguing taxonomic and functional possibilities and emphasize the continuing paleoanthropological productivity of Sterkfontein.
