Anomalies of the postcranial skeleton of rock lizards (Lacertidae: Darevskia)

Abstract Anomalies of the postcranial skeleton of nine taxa of the genus Darevskia belonging to the Darevskia ( caucasica ) and Darevskia ( saxicola ) complexes were studied for the first time on representative samples. Several groups and subgroups were identified: (1) asymmetric structure of ribs and/or transverse processes of vertebrae (anomaly of sacral vertebrae; and anomaly of the ribs in the presacral vertebra); (2) reduction of the ribs; (3) fusion of the vertebrae; and (4) anomalies of the sternum: xiphisternal rib formula. The Darevskia ( caucasica ) complex showed fewer anomalies than the Darevskia ( saxicola ) complex, in the latter we did not observe specimens with two ribs on one side of the vertebra or a reduction of the ribs on the 4th vertebra. At the same time, the highest number of anomalies was found in D. c. caucasica , the lowest in D. alpina , D. c. vedenica and D. b. myusserica . The most common anomaly is the asymmetric structure of the ribs at the level of the 21st, 22nd or 23rd presacral vertebra, the rarest are the reduction of the ribs at the level of the 4th presacral vertebra and the presence of two ribs on the left side at the level of the 16th presacral vertebra. The presence of a large number of anomalous specimens in rock lizard populations is not necessarily associated with parthenogenetic reproduction and hybridisation. Extreme environmental conditions (especially living in high mountains) are also not a necessary condition for the occurrence of anomalies in the structure of their postcranial skeleton.