New hominin cranial and mandibular remains from Drimolen Main Quarry, South Africa

Background To date, the only specimens to have been comprehensively described from Drimolen Main Quarry (DMQ) are dental elements, well preserved crania (DNH 7, DNH 134, DNH 152, DNH 155), and 29 post-cranial elements. Consequently, a significant number of hominin fossils, some excavated over 30 years ago, remain completely or partially undescribed and therefore unavailable for study.Aim To describe the bony anatomy of a further 18 cranial specimens excavated between 1992 and 2019. We additionally utilise these newly described specimens to test existing hypotheses concerning the first appearance of H. erectus at DMQ ∼2.0 Ma, and the morphological distinctiveness of the DMQ P. robustus ukusa sample.Subjects and methods We adopt the methods of descriptive morphology by comparing DMQ hominin fossils to hominin fossil samples from SM1HR and KBM4-6. We utilise qualitative anatomical descriptions and comparisons, supplemented with quantitative measurements.Results Of the 18 previously undescribed DMQ hominin fossils, we assign one to Homo erectus, 14 to Paranthropus robustus, and three to Hominini gen. et sp. Indet. Additionally, we identify a new mandibular trait which may further discriminate DMQ P. robustus from SM1HR and KBM4-6.Conclusion: The morphology preserved by these additional Paranthropus robustus fossils is compatible with the hypothesis that the DMQ population is morphologically distinct from the SM1HR and KBM4-6 populations. Further, DNH 127 provides additional evidence for the presence of H. erectus in South Africa at ∼2.04-1.95 Ma.