The morphological and genetic variation of a wide-ranging Secret Toad-headed agama, Phrynocephalus mystaceus that inhabits sand deserts of south-eastern Europe, Middle East, Middle Asia, and western China is reviewed. Based on the morphological differences and high divergence in COI (mtDNA) gene sequences a new subspecies of Ph. mystaceus is described from Khorasan Razavi Province in Iran. Partial sequences of COI mtDNA gene of 31 specimens of Ph. mystaceus from 17 localities from all major parts of species range were analyzed. Genetic distances show a deep divergence between Ph. mystaceus khorasanusssp. n. from Khorasan Razavi Province and all other populations of Ph. mystaceus. The new subspecies can be distinguished from other populations of Ph. mystaceus by a combination of several morphological features. Molecular and morphological analyses do not support the validity of other Ph. mystaceus subspecies described from Middle Asia and Caspian basin. Geographic variations in the Ph. mystaceus species complex and the status of previously described subspecies were discussed.
Keywords: Khorasan; Phrynocephalus mystaceus khorasanus; molecular phylogenetics; morphology; phylogeography; taxonomy.