The El Sidrón teeth are large, with crenulated enamel and accessory cusps. Neandertal lineage incisive features (16) observed in the sample include shovel-shaping, marked labial convexity, and strongly developed lingual tubercles. On the premolars (17), an asymmetric lingual contour, strong transverse crests, a metaconid lingually located, and accessory lingual cusps are present (e.g., SD-763). The posterior dentition shows some cases of a noticeable taurodontism (e.g., SD-531). No upper face skeletal remains have been recovered, but three mandibles are well preserved (Fig. 2). The mandibular body tends to be high and thick. The mental trigone is strongly developed without any sign of a submental notch. Interestingly, the retromolar space is short in these mandibles. Other characteristic Neandertal lineage features include mental foramen below M1, deep pterygoid fossa, and inclined mylohoid line.
The neurocranium is well represented in the sample but fragmentary. Overall, the anatomy of these fossils corresponds to the set of features detected in Late Pleistocene Neandertals. The SD-436 frontal preserves a portion of the right squama and part of the supraorbital torus, with the superciliary region preserved. It shows a marked anterior projection with the development of a supraglabellar fossa, and the supratoral sulcus is well defined; there is a rounded torus with apparent lateral continuity among the three elements and a high degree of pneumatization reaching the lateral trigone. SD-438 is an immature right supraorbital torus and a portion of the squama. It shows a marked projection of the supraorbital torus and a clear supratoral sulcus. The temporal bones (SD-315 and SD-359) are still covered by concretions, but several diagnostic features (18) can be distinguished, including a low projection of the mastoid process, flattened glenoid fossa, and an inclined anterior wall of this fossa. Two occipital bones have been recovered. SD-1219 is a reasonably complete occipitomastoid region (Fig. 3), with the upper occipital scale and temporal petrosal in good condition but a badly fragmented basilar part. The occipital is large, with a marked nuchal torus and open sutures connecting with a well preserved temporal pyramid. A large suprainiac fossa is present (Fig. 3). SD-1149 is smaller and partially covered by thin breccia. Right transverse sinuses are observed in both cases.
The postcranial skeleton is principally represented by hand and foot metapodials and phalanges, the latter being the most abundant bones in the assemblage (Table 1). Size and robustness of the first metacarpal and the enlarged distal tuberosity in the distal hand phalanges are among the diagnostic features. Included in a block (SD-437) are several bones of an adult foot in anatomical connection. Humeri (one complete), as well as fibulae and radii are also represented in the sample. The lower limb is poorly preserved, with an immature coxal fragment and remains of femora and tibiae, with thick cortical bone.