New insights into the Neanderthal pelvis morphology based on a partial os coxae from El Sidrón (Asturias, Spain).

The Neanderthal pelvis exhibits distinctive features compared to modern humans, including wider and more flared iliac blades, a more anteriorly positioned sacrum, and a longer and thinner, outwardly oriented pubic bone. Each new addition to the pelvic fossil record is significant for enhancing our understanding of Neanderthal morphology and variation. Here, we present SD-1663, the most complete adult os coxae fragment recovered from the El Sidrón site in Asturias (Spain), dated to approximately 49 ka. We carried out a detailed description and quantitative analysis of SD-1663 within a comparative framework that includes other notable pelvic fossil specimens. Utilizing traditional and three-dimensional morphometric techniques, we assessed the morphological characteristics of SD-1663 focusing on dimensions and anatomical landmarks that distinguish Neanderthal pelves from those of other hominins. The analyses reveal that SD-1663 was a young adult male with features and size that clustered with other Neanderthals in our comparative sample. However, SD-1663 also shares significant morphological affinities with earlier Pleistocene Homo specimens such as KNM-ER 3228 (Homo erectus), suggesting a broader range of pelvic variation within Neanderthals than previously recognized. This discovery contributes to expanding the Neanderthal range of anatomical diversity, indicating that the Neanderthal pelvis may have been more variable than the current fossil record suggests. It also underscores the importance of continued excavation and analysis of Neanderthal remains to fully comprehend the scope of their anatomical adaptations and evolutionary history. SD-1663 thus represents a valuable addition to the fossil record, offering new perspectives on Neanderthal pelvis morphology and its variation.