New hominin cranial remains from the Shungura Formation, Lower Omo Valley (Ethiopia)

  1. Amelie Beaudet
  2. Blade E. Redae
  3. Tomas Getachew Bedane
  4. Jerome Surault
  5. Jean-Renaud Boisserie

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Abstract

The formations of the Lower Omo Valley, south-western Ethiopia, have played a key role in our understanding of Plio-Pleistocene hominin taxic diversity and biogeography. Here, we describe two hominin cranial fragments excavated from Shungura Member L (Unit L-9) in 2016 and dated to ca. 1.15 million years ago (Ma). The two cranial fragments, OMO 342-10248a and OMO 342-10248b, were photographed, scanned, physically and digitally measured and compared to extant humans as well as Plio-Pleistocene hominin specimens. Based on the morphology of the ectocranial and endocranial surfaces, OMO 342-10248a and OMO 342-10248b are identified as a right parietal bone and an occipital bone, respectively. The average cranial thickness measured in OMO 342-10248a falls within the range of Asian Homo erectus and closely approximates individual values measured in some specimens of African Homo erectus, in particular the one of the remain P 996-17a from Unit K-3 of the Shungura Formation. The average cranial thickness measured in OMO 342-10248b falls within the range of Australopithecus africanus, Paranthropus boisei and African Homo erectus. The inner structural arrangement of both specimens is diploë-dominated and medical CT scans reveal the presence of the posterior temporal diploic vessels in OMO 342-10248a. The endocranial surface of OMO 342-10248a preserves imprints of the middle branch of the middle meningeal vessels and reveals substantial anastomoses. Overall, both specimens share similarities with Homo, and more particularly with Homo erectus. Resemblances with P 996-17a further support the possibility of Homo erectus-like hominins being present in the Lower Omo Valley 1.15 Ma.

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  1. Peer Community in Paleontology

    Early hominin cranial vault remains are rare, and any addition to the sample of known specimens is welcome and has the potential to contribute to our understanding of their variation and evolution. Specifically, for many decades there has been discussion in paleoanthropology about potential differences between Homo erectus individuals from Africa compared to those from Asia and whether early Pleistocene representatives of the former should be recognized as a distinct species, Homo ergaster (e.g., Wood, 1991; Anton, 2003). A new preprint presents two specimens, OMO 342-10248a and OMO 3042-10248b, representing a right parietal and occipital respectively of an early hominin (Beaudet et al., 2026). They derive from the youngest horizon of the Shungura Formation, Unit L-9, dated to approximately 1.15 Ma (De Heinzelin, 1983; Gardin et al., 2024).

    Based on the thicknesses of the squamae, with a relatively large contribution from the diploe, and the complexity of diploic vessels, Beaudet et al. (2026) attribute OMO 342-10248a and OMO 342-10248b to Homo, and more specifically, tentatively to H. erectus. Methodologically, they estimated the thickness of the Omo specimens using both caliper measurements and those derived from medical CT imaging and found the results sufficiently similar to be compared directly, a point the reviewers emphasized. The thickness of OMO 342-10248a is greater than that for most, but not all, African H. erectus/ergaster individuals and is more typical of H. erectus from Asia. If OMO 342-10248 is correctly allocated to H. erectus, then it implies more overlap in this feature between African and Asian individuals than had been previously known.

    Interestingly, Beaudet et al. (2026) propose developmental plasticity as a possible contributor to variation in cranial vault thickness and the amount of cranial thickness constituted by diploe, perhaps in response to thermoregulatory pressures. This is an intriguing hypothesis that merits further study, and if supported would add to the growing list of hominin morphological traits where developmental plasticity contributes a significant component of non-neutral variation (e.g., Ruff and Hayes, 1983; Richmond, 2007; Green and Alemseged, 2012; Kivell et al., 2018; Turley et al., 2018).

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  2. Version published to 10.31233/osf.io/be43y_v3 on OSF Preprints
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