Fine osteological and morphological features support the taxonomic identity of the semaphore geckoes, Pristurus guichardi, P. obsti and P. sokotranus (Gekkota: Sphaerodactylidae)

The semaphore geckoes, known from northern Africa, the Arabian peninsula and the Socotra Archipelago, comprise a pool of 23-26 species, some of which phenotypically much similar, seven of them endemic to Socotra and surrounding islands. The Socotran Archipelago is part of the Yemen Republic and it is well known for its highly endemic flora and fauna, and the herpetofauna is extremely interesting since it includes also ancient lineages of Gondwanan origin. Furthermore, reptiles of Socotra are actually well known and studied, and their taxonomic status is fully asssessed. However, it seems that some species represent a complex of species. Using a high-resolution non destructive three dimensional imaging technique (micro-computed tomography, or micro-CT) especially suitable for bone imaging of small specimens, we have defined osteological traits of three target species, two of them (P. guichardi and P. obsti) quite similar in external morphology, all of them not still analyzed with this technique. All micro-CT images have been acquired with a scan time of 18 min per sample and reconstructed at the spatial resolution of 18 μm in the three dimensions. Worthy of note are the differences in teeth and angular-suprangular-quadrate lever system. Morphological features support a clear cut separation of trophic niche of the species, with P. guichardi more adapted to a food-crushing pattern, P. obsti strictly insectivorous, and P. sokotranus similarly nsectivorous, but with differently shaped teeth. Particularly interesting is the differentiation between P. guichardi and P. obsti, that share many external morphological characters and whose specific identity has recently been determined. The features listed above and the granular structure of nasal, prefrontal and parietal bones clearly separate the two taxa.