Endocranial hyperostosis in Sangiran 2, Gibraltar 1, and Shanidar 5

Sangiran hominid 2 (S-2), Gibraltar hominid 1 (G-1), and Shanidar hominid 5 (SH-5) exhibit previously undescribed bilateral, paramedian hyperostosis of the endocranial frontal squama that spares the frontal crest, sagittal sinus, and ectocranial surface. The hyperostosis is localized to the frontal (usually the middle third) and parietal and is consistent with a diagnosis of hyperostosis calvaria interna (HCI), inclusive of hyperostosis frontalis interna. The hyperostosis in these specimens is compared to fossil hominids from Indonesia and Europe and to modern human cases of HCI. The three cases of HCI reported here documented the existence and frequency of HCI in fossil hominids and push the antiquity of the disease back to nearly 1.5 million years. The relatively great incidence of HCI in fossil hominids adds another confounding factor to the problematical issue of the taxonomic significance of cranial vault thickness.