Comparative characteristics of the postcranial skeleton of Rock lizards from the Darevskia (caucasica) and Darevskia (saxicola) complexes

Abstract

Anatomical-morphological features of the postcranial skeleton of nine taxa of the rock lizards of the genus Darevskia Arribas, 1999 belonging to the Darevskia (caucasica) and Darevskia (saxicola) complexes were studied for the first time on representative samples. Specimens with the rib formula 3+1 were found in both complexes (previously, only two variants were known for the genus Darevskia 3+2 and 3+3). Differences between supraspecific groups and their members were described with the use of type specimens or topotypes of each taxon. The studied complexes are differentiated by the range of variability of presacral vertebrae (in the D. (caucasica) their minimum number is 26, in the D. (saxicola) – 27), the number of the posterior presacral vertebrae with ribs (the average value of this trait in the D. (caucasica) is less than 6, in D. (saxicola) – more than 6). B-type of the tail vertebrae in 5 times more common in the D. (saxicola) than in the D. (caucasica). In turn, the latter group is characterized by a larger share of individuals with ossified ribs at the third cervical vertebra and a greater variability of the sternal-xiphisternal costal (rib) formula. Skeletal morphology of D. alpina indicates its greater similarity with representatives of the D. (caucasica) complex. A certain originality of D. c. vedenica was recorded. The study of D. saxicola specimens from the zone of sympatry with D. c. caucasica (Chegem Gorge) did not reveal their similarity with the latter, except for the presence of two variants of the sternal-xiphisternal formula. Cryptic forms within D. lindholmi differ at least in two traits: the minimum number of posterior presacral vertebrae with short ribs and the presence of individuals with caudal vertebrae of B-type.