Discovery of two new species of Phymaturus (Iguania: Liolaemidae) from Patagonia, Argentina, and occurrence of melanism in the patagonicus group

Comprehensive studies recently published on the evolution and systematics of Phymaturus (morphological and molecular ones, respectively) revealed not only a historical pattern and subclades within the traditional palluma and patagonicus groups but also a still not fully understood unsuspected diversity. Several populations in northern and southern Argentina may represent independent lineages that deserve formal description. Two of these populations were studied in the present contribution and are easily distinguished from all the other species in the genus. One of these populations is from Río Negro province and belongs to the patagonicus group; it exhibits a particular dorsal colouration pattern and several individuals are melanic, a characteristic never reported before for the genus, with the exception of P. tenebrosus. A careful examination of melanic individuals revealed the same dorsal pattern as that of non-melanic ones, although it is hidden. We also report the discovery of melanic individuals of two other species that are probably closely related: P. ceii and P. sitesi. The melanism found in the patagonicus group differs from the head melanism of males in certain species of the palluma group because in the former group melanism is not ruled by sexual dimorphism and involves the whole animal. The other population studied in this contribution belongs to the palluma group and is described as a new species because its colour pattern and scalation differ from those of all the other members of the palluma group. Finally, we discuss the position of these new lizard species in the context of the available phylogenetic hypothesis and the occurrence and evolution of melanism in the patagonicus group.