Salamandrella

Macaluso, Loredana, Wencker, Lukardis C M, Castrovilli, Maria, Carnevale, Giorgio & Delfino, Massimo, 2023, A comparative atlas of selected skeletal elements of European urodeles (Amphibia: Urodela) for palaeontological investigations, Zoological Journal of the Linnean Society 197 (3), pp. 569-619 : 578-586

SALAMANDRELLA DYBOWKI, 1870

Species: Salamandrella keyserlingii * Dybowski, 1870 .

Otic–occipitum complex

In hynobiids, the prootic and opisthotic–exoccipital remain unfused in morphologically mature specimens; therefore, there is no otic–occipitum complex ( Jia et al., 2019).

Atlas ( Fig. 6A )

The neural canal is triangular in anterior view and is at least twice as high as each occipital joint. In posterior view, the neural canal is two or three times as wide as the circular cotyle. The occipital joints are elliptical, with the major axis horizontal (or subhorizontal). The articular surfaces of the odontoid process contact each other, such that in ventral view no groove is visible between them. In ventral view, the base of the odontoid process is wider than each occipital joint. The neural crest is absent. Based on the literature, in the completely ossified atlantes, a bulge should be present in its place ( Ratnikov & Litvinchuk, 2009); however, in all specimens examined in this work, the walls of the neural arch do not contact each other at the dorsal midline, and two articular surfaces are present in the middle. These are visible in dorsal view and articulated through cartilage. The secondary crests and the neural spine are absent. The lateral surface of the atlas bears only the foramen of the first spinal nerve. The incisura vertebralis cranialis is generally absent or small. In lateral view, the dorsal edge of the neural arch is sub-horizontal. The posterior margin of the lateral wall of the neural arch, ventral to the wide incisura caudalis in lateral view, is concave, inclined or sub-vertical. The maximum concavity of the incisura vertebralis caudalis is dorsal to the horizontal plane containing the maximum concavity of the incisura cranialis. The lateral crests are absent, and the inferior crests are low or also absent. In posterior view, the neural arch is dorsally convex (inverted U-shaped). In lateral view, the postzygapophyses extend posteriorly beyond the cotyle for more than half of their length, and in posterior view, these structures are sub-horizontal. In dorsal view, the neural arch is anteriorly and posteriorly concave (with V-shaped concavities). The cotyle is generally not visible in dorsal view, or only slightly visible in the middle of the incisura dorsalis. The ventral surface generally bears more than one foramen.

Precaudal vertebrae ( Fig. 9A )

The precaudal vertebrae are amphicoelous. The neural canal is pentagonal or circular in anterior view, slightly higher or lower than the cotyle. The cotyles are circular or slightly elliptical, with the major axis horizontal. In lateral view, the anterior edge of the neural arch between the cotyle and prezygapophyses is concave or vertical. Diapophyses and parapophyses are usually fused and not recognizable (unicipital transverse processes). The transverse processes are rectangular in anterior view and slightly pointed posteroventrally. The transverse processes do not cover (or cover only in part) the posterior edge of the neural arch in lateral view. In lateral view, the vertebrae are dorsoventrally compressed, and most of the height of the vertebrae is formed by the centrum and the neural canal (only one-fifth of the height of the vertebra is formed by the neural arch dorsal to the postzygapophyses). In lateral view, the neural arch dorsal to the prezygapophyses is not visible or only slightly visible. The neural crest is absent. The neural spine is present in the form of a low and thick bulge that is posteriorly convex and extends posteriorly as far as the postzygapophyses. The anterior and posterior zygapophyseal and ventral crests are absent. The lateral surface of the vertebrae is smooth. The only foramen present is visible in anterior and lateral views, in the ventral half of the proximal edge of the transverse processes. In lateral view, the dorsal edge of the neural arch is anteriorly sub-horizontal. The incisura vertebralis caudalis is not deep and only present as a small posterior concavity (wider in the first precaudal vertebrae), and the neural arch between the centrum and postzygapophyses is slightly concave or convex. In posterior view, the neural arch is dorsally flat or convex (inverted U-shaped). In lateral view, the postzygapophyses extend posteriorly beyond the cotyle for more than half of their length, and in posterior view, postzygapophyses are sub-horizontal. In dorsal view, the neural arch is anteriorly concave (U-shaped), and posteriorly, the incisura dorsalis is not visible. The edge of the anterior cotyle is visible in dorsal view, whereas the posterior cotyle is not visible. In lateral view, the ventral profile of the centrum is strongly concave. The ventral surface is generally smooth.

Caudal vertebrae ( Fig. 12A )

The caudal vertebrae are not particularly high (height/length ratio <1.25). The neural canal is pentagonal or circular, whereas the haemal canal is elliptical or U-shaped. The neural canal is wider and lower than the haemal canal, and the haemal arch is generally slender. The transverse processes are long and slender, sub-cylindrical and pointing ventrally. The neural crest is absent or low; a posterodorsal bulge is present. Zygapophyseal and ventral crests are absent. The lateral surface is smooth, with a single foramen visible at the base of the haemal arch. In lateral view, the anterior edge of the haemal arch is variably inclined, convex or concave, whereas the posteroventral edge of the haemal arch forms a sharp tip in lateral view. In ventral view, the posterior edge of the haemal arch is not forked. The haemal crest is either low or absent.

Figures

Figure 6. Atlantes of European urodeles. A, Salamandrella keyserlingii (BSPGM 5451), most probably not completely ossified (see the Material section). B, Proteus anguinus (BSPGM 4538). C, Speleomantes strinatii (MDHC 225), most probably not completely ossified (see the Material section). D, Salamandrina perspicillata (MDHC 407). E, Chioglossa lusitanica (MNCN 16099). F, Mertensiella caucasica (MNCN 23821). G, Salamandra salamandra (MDHC 396). From left to right: anterior, dorsal, lateral (right lateral for A–C, E, F; left lateral for D, G), posterior and ventral views. Scale bars: 1 mm.

Figure 9. Precaudal vertebrae of European urodeles. A, Salamandrella keyserlingii (BSPGM 5451). B, Proteus anguinus (BSPGM 4539). C, first precaudal vertebra of Speleomantes strinatii (MDHC 225). D, precaudal vertebra of Speleomantes strinatii (MDHC 225) close to the pelvis. E, Salamandrina perspicillata (MDHC 228). F, Chioglossa lusitanica (MNCN 16099). From left to right: anterior, dorsal, lateral (right lateral for A, C–F; left lateral for B), posterior and ventral views. Scale bars: 1 mm.

Figure 12. Caudal vertebrae of European urodeles. A, Salamandrella keyserlingii (BSPGM 5451). B, Proteus anguinus (BSPGM 4538). C, Speleomantes strinatii (MDHC 225). D, Salamandrina perspicillata (MDHC 407). E, Mertensiella caucasica (BSPGM 2730). F, Salamandra salamandra (MDHC 234). G, Salamandra salamandra (MDHC 396). From left to right: anterior, dorsal, lateral (right lateral for A, B, D–F; left lateral for C, G), posterior and ventral views. Scale bars: 1 mm.