Chioglossa

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 : 590-591

CHIOGLOSSA BOCAGE, 1864

Species: Chioglossa lusitanica *.

Otic–occipitum complex ( Fig. 4C )

The otic–occipitum complexes of the only specimen of Ch. lusitanica available for this study (MNCN 16099) are poorly preserved and poorly ossified, especially the left one. The crests are not visible, and some of the characters are difficult to interpret owing to the inadequate preservation. The prominentia semicircularis anterioris, posterioris and lateralis are evident and rounded. Among them, a deep middle depression shows a fourth, unnamed prominentia separated from the prominentia semicircularis lateralis by a deep groove. The prominentia semicircularis posterioris is extended posteriorly and ventrally between the cotyle and the parotic process. The elliptical fenestra ovalis is oriented posterolaterally, such that it is visible in posterior view; its anterior edge is anterior to the mid-length of the complex. The dorsal edge of the fenestra is not visible in dorsal view, because it is covered by the prominentia lateralis. In dorsal view, the parietal crest is poorly visible, but it seems to be present; its posterior part is severely damaged, and it is not possible to determine where its posterior margin lies, whereas anteriorly it reaches the anteriormost point of the prominentia semicircularis anterioris. The parotic crest is short and does not form a lateral parotic process. The tectum synoticum and the prefacial commissure seem not to be extended medially, and there is no concavity between them. These commissures are less medially extended than the hypochordal commissure. However, owing to the poor preservation, it is not possible to determine whether this structure is broken or poorly ossified; therefore, these character states are regarded as uncertain. The postoticum foramen is circular and surrounded posteriorly by the lamina of the tectum synoticum and the cotyle. In lateral view, a lamina posterior to the fenestra ovalis is present, connecting the postoticum foramen with the posterior end of the prominentia semicircularis lateralis. More anteriorly, the foramen faciale is visible. The subcircular articular surfaces of the otic process and the bean-shaped surface of the processus basalis are not separated by a deep sulcus petrosus. The otic process is not anteriorly projecting. The basicapsular commissure is medially extended beyond the prefacial commissure, 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. In the right complex, there is an anomalous ossification affecting the ventromedial surface, but in the left complex, the crista retrosellaris between the basicapsular and hypochordal commissures occupies part of the fenestra basicranialis, leaving a concavity close to the hypochordal commissure. The ventral surface is generally smooth, with one or two foramina in addition to the foramen faciale, and the sulcus carotis extends medially beyond the medial crest.

Atlas ( Fig. 6E )

The only available atlas is badly damaged, with the postzygapophyses and the neural and secondary crests poorly visible; some of the characters are therefore uncertain. The neural canal is circular in anterior view and twice as high as each occipital joint. In posterior view, the neural canal is two or three times as wide as the elliptical cotyle. The occipital joints are elliptical, with the minor axis being horizontal. The articular facets of the odontoid process are separated by a large 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 or absent. The posterodorsal area of the neural arch is poorly preserved, hence the presence of the neural spine cannot be assessed. The lateral surface of the atlas bears two or more foramina per side. The incisura vertebralis cranialis is small. In lateral view, the dorsal edge of the neural arch is sub-horizontal. The neural arch between the wide incisura caudalis and the cotyle is convex or inclined. The maximum concavity of the incisura vertebralis caudalis is dorsal to the horizontal plane containing the maximum concavity of the incisura cranialis. The lateral and inferior crests are absent or low. In dorsal view, the neural arch is anteriorly straight. The ventral surface bears small foramina.

Precaudal vertebrae ( Fig. 9F )

The vertebrae are opisthocoelous, longer than wide, and dorsoventrally flattened, meaning that in lateral view, only one-fifth of the height of the vertebrae is formed by the neural arch dorsal to the prezygapophyses. The neural canal is elliptical, with the major axis being horizontal. Diapophyses and parapophyses are connected by a lamina reaching their distal ends. The lamina is distally linear or only slightly concave. The neural crest is low, posteriorly enlarged, and starts anteriorly from the line connecting the posterior edge of the prezygapophyses or posterior to it. The neural spine is absent. The lateral surface of the vertebra shows more than one foramen. In anterior view, a foramen is visible in the ventral half of the proximal edge of the transverse processes (at the base of the parapophyses). The anterior zygapophyseal crests are low or absent; the posterior ones are absent or present but do not contact the transverse processes. In lateral view, the anterior edge of the neural arch dorsal to the prezygapophyses is generally not visible, and it is vertical between them and the condyle. The incisura vertebralis caudalis is deep and not covered by the transverse processes, and the neural arch between it and the cotyle is inclined. Less than half of the postzygapophyses extends posteriorly beyond the cotyle. In dorsal view, the incisura dorsalis is formed by the neural arch, and the dorsal edge of the neural arch is flat. In dorsal view, the anterior edge of the neural arch is concave, and the condyle is visible, whereas the cotyle is not visible. Pre- and postzygapophyses are elliptical, and the prezygapophyses are strongly concave dorsally. The ventral lamina is not wide and is, in general, irregular in shape (triangular, trapezoidal or asymmetrically rhomboidal). The posterior ventral crests do not reach the cotyle. The ventral surface is generally perforated.

Caudal vertebrae

In the only available specimen, the caudal vertebrae are missing.

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.