A new, but probably extinct, species of Cnemidophorus (Squamata, Teiidae) from Uruguay

A new species of Cnemidophorus related to the lacertoides group is described. The new taxon is distinguished from all other species of the genus by the following combination of character states: 81-98 granular dorsal scales across midbody; 201-206 dorsal scales along midline from nape to rump in males, 208-229 in females; 10 longitudinal rows of ventral scales in both sexes; 19-22 femoral pores in total; 13-15 subdigital lamellae under fourth finger, 20-25 lamellae under fourth toe; 3-4 supraoculars on each side; reduced expression of the "lacertoides pattern", which may be absent and replaced by a broad greenish mid-dorsal stripe on a brownish-grey background; ventral surfaces of head, body, limbs and tail pearly white, with the most lateral ventral scales of the body completely dark along the belly. The new species also exhibits some anatomical differences from its most closest related species, C. lacertoides. The hyobranchial apparatus of Cnemidophorus new sp. has a pair of short cartilaginous second ceratobranchials, articulated behind the basihyal-first ceratobranchial joint. This structure is absent in the hyobranchial apparatus of C. lacertoides sensu stricto which, moreover, has hypohyals that are relatively longer than in the new species. The new taxon is known only from the type locality, Cabo Polonio, Rocha Department, on the Atlantic coast of Uruguay, in a habitat of rocky grassland. Records of individuals are lacking from three decades to date and detailed field surveys in recent years in search of the lizard were unfruitful. We assume that this taxon is probably extinct. The pressure of increased human presence on the limited suitable habitat in the Cabo Polonio region could have caused its extinction.