Internal carotid supply to the parietal meninges: a comparative study based on cranio-orbital vascular traces in modern humans and Indonesian Homo erectus

The recurrent branch of the ophthalmic artery which originates from the internal carotid artery, or the recurrent meningeal artery (RMA), often extends to the parietal meninges in non-human haplorrhines. The RMA usually enters the cranial cavity via the superior orbital fissure (SOF) in modern humans and generally via the cranio-orbital foramen (COF) in non-human haplorrhines. The present study aimed to clarify how often the RMA extends its territory to the parietal meninges and via which pathway it enters the cranial cavity in Indonesian Homo erectus . This study also aimed to enhance our knowledge of cranial vascular traces in modern humans. The caliber of the COF and the associated vascular trajectories were examined in 156 sides of 78 modern Japanese crania and 12 sides of eight Indonesian H. erectus specimens. The results showed that two Indonesian H. erectus crania (Sambungmacan 4 and Ngawi) had a large COF unilaterally, via which the RMA probably extended its territory to the parietal region. The prevalence of RMA reaching the parietal region in Indonesian H. erectus (16.7%) was not as high as that in the extant great apes, but significantly higher than that in Homo sapiens (0.6% in this study; 3% at most in general). These results suggest that the SOF-related RMA became predominant in H. sapiens or the ancestor sometime in the Pleistocene, while the middle meningeal artery (MMA) arising from the external carotid–maxillary artery might not have been so enhanced in H. erectus and their ancestral hominins versus modern humans. The possible Influence of encephalization and other factors on the evolutionary changes of the RMA and MMA can be hypothesized based on ontogenetic and hemodynamic assumptions.