Bioacoustics of Salamandra

Otic–occipitum complex ( Fig. 4E ) The prominentia semicircularis anterioris is covered by the high parietal crest, whereas the prominentiae semicircularis posterioris and lateralis are rounded and easily recognizable. Among the prominentiae, a deep middle depression shows no foramina in its floor. The prominentia semicircularis posterioris is not extended posteriorly and ventrally between the cotyle and the parotic process. The circular fenestra ovalis is almost perpendicular to the vertical, and its anterior edge is anterior to the mid-length of the complex. The high parietal crest begins from slightly posterior to the mid-length of the distal edge of the tectum synoticum and extends obliquely on the tectum synoticum and on the prominentia semicircularis anterioris until the anterior end of the otic process. It is higher anteriorly, with its anterior tip forming an angle of 70–90° with the vertical. The parotic crest starts from the dorsolateral edge of the cotyle, extends along the lateral edge of the prominentia lateralis and meets the parietal crest in the anterior part, forming a variable angle. The parotic process is represented by a small tip, although it can be absent in some cases. In more detail, the parotic crest can be interrupted or not, depending on the position of the fenestra ovalis; when the fenestra ovalis has a dorsal position, the parotic crest is interrupted in its middle part, and the parotic process is not present (e.g. in MNHN 1888.651). The parotic crest is developed variably between the parotic process and its anteriormost part and, in some specimens, it is absent in this area (e.g. in the left capsule of HNHM 2001.75.24). The tectum synoticum is enlarged distally, and its anterior edge in medial view is posterior to the midlength of the complex.The tectum synoticum is extended medially beyond the prefacial commissure, but a small concavity is visible between them. The tectum is almost as medially extended as the hypochordal commissure. The postoticum foramen is elliptical, with the vertical major axis being not much longer than the minor one, and surrounded posteriorly by the lamina of the tectum synoticum and the cotyle. The articular surfaces of the otic process and of the processus basalis are kidneyshaped and separated by a deep sulcus petrosus. The otic process is slightly more developed anteriorly than the processus basalis, forming a short, irregular anterior process. The basicapsular commissure is extended slightly medially beyond the prefacial one, and the foramen prooticum is not surrounded by bone. The auditory cavity is deep, with isolated foramina for the different branches of the acoustic nerve. In ventral view, a low medial crest runs along the medial side of the ventral surface of the complex. The crista retrosellaris between the basicapsular and hypochordal commissures occupies most of the fenestra basicranialis, leaving only a small triangular concavity close to the hypochordal commissure. The ventral surface is smooth or bearing a couple of foramina, with the sulcus carotis not reaching the low medial crest. Remarks: In the right complex of HNHM 2001.75.24, the parietal crest is less developed than in the other specimens. Atlas ( Fig. 6G ) The neural canal is generally triangular or subtriangular in anterior view and is as high as each occipital joint. In posterior view, the neural canal is slightly wider than the cotyle; the cotyle is elliptical, with the major axis being horizontal. The occipital joints are circular or elliptical, with the minor axis being horizontal (or sub-horizontal). The articular facets of the odontoid process are separated by a wide groove on the ventral surface. In ventral view, the base of the odontoid process is wider than each occipital joint. The neural crest is low and thick or blade-like, starts posterior to the anterior edge of the neural arch and is posteriorly forked, and in lateral view, it is horizontal or gently concave. The secondary crests are parallel to the anterior edge of the neural arch (running transversely across the neural arch roof), and their posterior end corresponds to the anterior margin of the neural crest. In lateral view, these crests can or cannot cover the anterior edge of the neural arch. The neural spine can be present or absent. The lateral surface of the atlas bears more than one foramen per side. The incisura vertebralis cranialis is wide and does not contact the occipital joints. In lateral view, the dorsal edge of the neural arch is strongly inclined, forming an angle of 50–60° relative to the horizontal axis. The neural arch between the incisura caudalis and the cotyle is inclined or concave. The maximum concavity of the incisura vertebralis caudalis lies almost in the horizontal plane containing the maximum concavity of the incisura vertebralis cranialis. The low lateral crests do not reach the elliptical postzygapophyses. The inferior crests are low. In posterior view, the neural arch is dorsally convex (inverted U-shaped). Less than one-third of the postzygapophyses extends posteriorly beyond the cotyle in lateral view. In dorsal view, the neural arch is anteriorly straight or concave (V-shaped concavity), and the incisura dorsalis (formed by the neural arch) can be observed posteriorly. The cotyle may or may not be visible in dorsal view. The ventral surface is smooth or bears more than two foramina.