Salamandrina

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 : 589-590

SALAMANDRINA FITZINGER, 1826

Species: Salamandrina perspicillata * (Savi, 1821) and Salamandrina terdigitata * (Bonnaterre, 1789) .

Otic–occipitum complex ( Fig. 4B )

The prominentiae semicircularis anterioris and posterioris are well defined and rounded, whereas the prominentia semicircularis lateralis is less evident. Among the prominentiae, the deep middle depression is characterized by smaller foramina in its floor. The circular fenestra ovalis is visible in posterior view, and on the lateral surface a low crest connects the mid-length of the dorsal edge of the fenestra ovalis to the posterior end of the prominentia semicircularis lateralis. The parietal crest is absent or low, beginning from the mid-length of the proximal tectum synoticum and extending along the full length of the prominentia semicircularis anterioris. The parietal crest is more evident close to tectum synoticum, forming a variably developed tuberculum at the posterior edge of the prominentia semicircularis anterioris.The parotic crest runs along the anterior lateral half of the prominentia lateralis, meeting the parotic crest on the anterior edge of the prominentia semicircularis anterioris. A laterally extended parotic process is located at the mid-length of the prominentia lateralis, with a smooth and rounded surface posterior to it. The parotic process is laminar in dorsal view and vertical in lateral view, extending ventrally beyond the prominentia lateralis and sometimes reaching the ventralmost edge of the complex. In anterior and posterior views, the parotic process is sub-triangular and slightly concave ventrally. The tectum synoticum is extended medially beyond the hypochordal commissure and the prefacial commissure, and a small concavity is visible between the commissures. In medial view, the anterior edge of the tectum synoticum is posterior to the midlength of the complex. In lateral view, the elliptical postoticum foramen is surrounded posteriorly by the cotyle. The foramen faciale is posterodorsal to the processus basalis. In anterior view, the otic process is not anteriorly projecting, and its articular surface is irregular. The articular surface of the processus basalis has the shape of an ellipse with extreme dorsoventral compression. The prooticum foramen is surrounded completely or in part by bone. The auditory cavity is deep, with isolated foramina for the different branches of the acoustic nerve. The hypochordal commissure is as medially extended as the basicapsular commissure. The crista retrosellaris between the basicapsular and hypochordal commissures occupies less than half of the fenestra basicranialis. The latter is a wide concavity between the crista retrosellaris and the hypochordal commissure. On the ventral surface, the sulcus carotis crosses the high medial crest.

Atlas ( Fig. 6D )

The neural canal is circular in anterior view, twice as high as each occipital joint. In posterior view, the neural canal is twice as wide as the circular cotyle. The occipital joints are circular or elliptical, with a horizontal (or sub-horizontal) minor axis. 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 posteriorly forked, bears lateral lips (see also Macaluso et al., 2020) and originates posterior to the anterior edge of the neural arch, being gently rising, dorsally concave or convex in lateral view. The secondary crests and the neural spine are absent. The lateral surface of the atlas bears one or more foramina per side. The incisura vertebralis cranialis is wide and does not contact the occipital joints. The dorsal portion of the arch, dorsally marking the incisura cranialis, projects strongly in the anterior direction in lateral view. In the same view, the dorsal edge of the neural arch is sub-horizontal. The neural arch between the small incisura caudalis and the cotyle is 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 reach the quadrangular postzygapophyses and are extended laterally such that the incisura caudalis is variably covered by them. The inferior crests are present. In posterior view, a zygantrum is usually present, and the neural arch is dorsally convex (inverted U-shaped) or flat. Fewer than one-third of the postzygapophyses extend posteriorly beyond the cotyle in lateral view. In dorsal view, the neural arch is straight anteriorly. The posterior edge of the atlas bears a deep incisura dorsalis, largely formed by the neural crest. The cotyle is generally not visible in dorsal view or visible only slightly, in the middle of the incisura dorsalis. The ventral surface generally bears more than two foramina.

Precaudal vertebrae ( Fig. 9E )

The precaudal vertebrae are opisthocoelous, with a variably developed zygosphene–zygantrum complex. The neural canal is circular, triangular or dorsoventrally compressed in anterior view, slightly higher or lower than the condyle. The condyle is elliptical, with a horizontal major axis and slightly flattened dorsal edge. In lateral view, the neural arch between the condyle and the quadrangular prezygapophyses is strongly inclined or vertical. Diapophyses and parapophyses are distinguishable, connected by a lamina (with anterior and posterior foramina and concavities in variable numbers), generally reaching their distal ends. The transverse processes have a slightly posterior orientation, but they do not cover the posterior edge of the neural arch in lateral view. In the same view, the neural arch, dorsal to the prezygapophyses, is visible and projects anteriorly to a variable extent. One-third of the height of the vertebrae is formed by the neural crest, which is high, enlarged posteriorly and forked from the mid-length of the vertebra. The neural crest bears lateral lips and starts posterior to the anterior edge of the neural arch. The neural spine is absent. The anterior and posterior zygapophyseal crests are equally developed, horizontal or slightly concave ventrally. The ventral crests form a symmetrically rhomboidal ventral lamina. The posterior ventral crests reach the posterior edges of the cotyle. The lateral surface of the vertebrae is not smooth, with at least two foramina per side (but often more). In lateral view, the dorsal edge of the neural arch is anteriorly horizontal or dorsally concave. The incisura vertebralis caudalis is deep and generally reaches the centrum. In posterior view, the neural crest is horizontal dorsally. In lateral view, the neural arch dorsal to the postzygapophyses is vertical or sinusoidal. Less than half of the postzygapophyses is extended posteriorly beyond the cotyle in lateral view. In dorsal view, the neural arch is flat or anteriorly projecting. Both the cotyle and the anterior edge of the condyle are visible in dorsal view. The ventral surface is generally perforated.

Remarks: The zygosphene and zygantrum are variably developed and are entirely absent in MDHC 300. The neural crest of MDHC 326 shows small lateral lips. Some specimens (MNCN 16274, MNCN 16276 and MDHC 300) show a crest dorsal to the diapophysis.

Caudal vertebrae ( Fig. 12D )

The caudal vertebrae are not particularly high (height/ length ratio <1.25). The neural canal is circular, triangular or pentagonal, whereas the haemal canal is triangular. The neural canal is wider and lower than the haemal canal. The transverse processes are triangular in anterior view, giving the vertebra a rhomboid shape in this view. The neural crest is high, as in the precaudal vertebrae. Lips of the neural arch and the zygosphene–zygantrum complex are variably present. Zygapophyseal and ventral crests are present and form a typical M-shape, with one anterior concavity and two posterior concavities with the transverse processes (see Fig. 12D ). The posterior ventral crests arise from the posteroventral tip of the haemal crest. In lateral view, anterior and posterior ventral crests form an angle of <130°. The anterior ventral crests project anteriorly beyond the haemal arch. The lateral surface is not smooth; it bears variable numbers of crests and small foramina, but no large foramen occurs in the haemal arch. In lateral view, the anterior edge of the haemal arch is concave or posteriorly inclined, whereas the posteroventral edge of the haemal arch forms a sharp tip. In ventral view, the posterior end of the haemal arch is forked. The haemal crest is high, forked from the mid-length of the vertebra and, in general, more anteriorly projected than the haemal arch, forming a sharp or rounded tip in lateral view.

Remarks: The neural arch of MDHC 300, which does not show a zygantrum or zygosphene in the precaudal vertebrae, possesses them in the caudal vertebrae, except for the anterior ones.

Figures

Figure 4. Otic–occipitum complexes of European urodeles (Plethodontidae, Salamandrininae and Salmandrinae). A, left complex of Speleomantes strinatii (MDHC 225). B, left complex of Salamandrina perspicillata (MDHC 407). C, right complex of Chioglossa lusitanica (MNCN 16099; ventral view of the left complex because the right one is anomalous; see main text). D, right complex of Mertensiella caucasica (MNCN 23821). E, left complex of Salamandra salamandra (MDHC 227). From left to right: dorsal, ventral, anterior, posterior, medial and lateral views. Scale bars: 1 mm.

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.