Endocranial occipito-temporal anatomy of SD-1219 from the Neandertal El Sidrón Site (Asturias, Spain).

We addressed the brain drainage system as inferred by the endocranial morphology of the occipito-temporal region of the El Sidrón Neandertal specimen SD-1219. Morphological details of the endocranial surface and its anatomical implications were analyzed for the reconstruction of the dural sinus drainage pattern and its comparison with Neandertals and other hominids. The specimen SD-1219 shows a pattern in which the superior sagittal sinus goes into the right transverse sinus. Comparative analyses with a large sample of fossil hominids reveal a pattern of the SD-1219 fossil that is typical for Neandertals. The analysis of the proportions of the occipital lobes prints within the occipital fossae reveals that the left occipital pole projects toward the right. This possibly indicates brain asymmetry (petalia) in this Neandertal individual, similar to that observed in some modern human brains. Conversely, no such asymmetry was observed in the cerebellar fossae. A particular feature of this fossil is the presence of two crests, located at the middle of the left cerebellar fossa that can be related to either an imprinting of a cerebellar fissure or some bone response to mechanical influence on internal bone surface morphology during cerebellar development. Specific aspects of the paleoneurology of Neandertals are discussed. Further quantitative studies on the endocranial morphology of the occipito-temporal and -mastoid region will shed light on the paleoneurological significance of this important anatomical region for the understanding of human evolution.