Two New Species of Night Lizards (Xantusia) from Mexico

Two lineages of Xantusia occurring in northwestern Mexico are each deeply divergent in mitochondrial and nuclear DNA, mutually exclusive relative to other members of the genus, and morphologically diagnosable. They are formally described here as new species. The new species from Sonora resembles its nearest relative, Xantusia arizonae, in that females lack well-developed femoral pores, but it differs in numbers of dorsal scales around midbody and in color pattern. It is found near the Sea of Cortez in a unique microhabitat, fallen Pachycereus pringlei (cardon), whereas X. arizonae occurs in rock crevices in central Arizona. The new species from Baja California Sur differs from its nearest relative, Xantusia gilberti, in color pattern and in having small scales bordering the labium behind the fifth infralabial. It is found in Yucca valida (datilillo) on the Magdalena Plains near the Pacific Coast, whereas X. gilberti occurs in pine-oak woodland of the Sierra La Laguna, 350 km to the south.