A Glyptosaurine Lizard from the Eocene (late Uintan) of San Diego, California, and Implications for Glyptosaurine Evolution and Biogeography

Glyptosaurine lizards (family Anguidae) are known exclusively from the Paleogene of North America and Eurasia. In North America these lizards are largely restricted to the intermontane basins along the Rocky Mountains, with only sparse, indeterminately-identified skeletal elements known from outside of this region. In this study I describe a new specimen assignable to G. sylvestris, notable for being recovered from the late Uintan of the Santiago Formation in southern California, significantly outside the known geographic range of well-preserved glyptosaurine fossils. The presence of Glyptosaurus in southern California at a time of widespread geographic change and regional endemism in mammalian faunas, when also considering the results other studies of Eocene lizards, indicates a pattern of evolution for lizards different from the turnovers and regional restrictions observed in mammals. The specimen described here shows features consistent with ontogenetic variation and may help to provide insight into the life history of glyptosaurine lizards.