High osteological variation in a terrestrial salamander (genus Salamandrina)

A comparative atlas of selected skeletal elements of European urodeles (Amphibia: Urodela) for palaeontological investigations

The osteology of European urodeles was studied extensively in the past, but comparative analyses of isolated bones are rare, despite being the most useful tool for the identification of fossil remains. The present work is focused on the most robust skeletal elements (therefore, common in the fossil record: otic–occipitum complexes and vertebrae) and provides taxonomically significant diagnostic characters at the genus level for European genera of urodeles, including some taxa whose osteology was poorly known (e.g. Euproctus and Calotriton). Characters subject to wide variability are identified, and their use is discouraged for diagnoses of extinct species. A selection of diagnostic characters is used herein to build an identification key for each studied skeletal element and for a phylogenetic analysis to understand whether these osteological elements can convey a genuine signal. The analysis under Bayesian inference resulted in a well-supported Salamandridae clade and Pleurodelinae tribe. Salamandrina was recovered as part of the Pleurodelinae, in agreement with previous morphological phylogenetic analyses, but in contrast to the conclusion of molecular studies.

Osteology of the Italian endemic spectacled salamanders, Salamandrina spp. (Amphibia, Urodela, Salamandridae): selected skeletal elements for palaeontological investigations

Salamandrina perspicillata, from Northern and Central Italy, and Salamandrina terdigitata, from Southern Italy, represent a unique case of endemism among the amphibians of Europe. Some efforts were made to study the biology and ecology of these species, but only few studies focused on their comparative osteology. In particular, detailed descriptions of isolated skeletal elements and comparisons with other European urodeles are not available in literature hindering the identification of their fossils that testify for an ancient much broader range. The correct identification of fossil remains, mostly based on careful osteological descriptions, is fundamental to study the evolution of the range of this genus through time and the origin of the current endemic condition. This work is focused on the description of selected skeletal elements (occipito-otic complex, limb bones, atlas, trunk, sacral, caudosacral and caudal vertebrae) of dry-prepared skeletons and CT-scans of wet preserved specimens, which are the most common in the fossil record. We provide osteological comparison of Salamandrina with other genera of Europe, yielding diagnostic characters which allow the identification of fossils at a generic level. No significant differences between the two species S. perspicillata and S. terdigitata were found in the described skeletal elements, thus, the identification of skeletal elements at the species level is, at the moment, impossible.