CONRAD, J.L.*; SERENO, P.C.; Univ. of Chicago; Univ. of Chicago: An Early Cretaceous lizard skull from Mongolia and the early evolution of Gekkota

Fossil evidence of Gekkota, and particularly its stem taxa, remains scanty. The earliest records are nearly as derived as extant members and, consequently, phylogenetic uncertainty persists regarding the relationships of Gekkota. Suggested sister taxa among extant squamates have included dibamids, amphisbaenians, skinks, and a clade including skinks and anguimorphs. Additonally, constitution of ingroup Gekkota is ambiguous. Particularly problematic are the extinct ‘bavarisaurids’ and ‘ardeosaurids’, often considered stem gekkotans. We describe a well-preserved fossil skull from the Early Cretaceous of Mongolia that, like other putative �stem geckoes�, has large eyes, numerous small teeth, and no lacrimal. The new taxon is plesiomorphic in possessing a complete supratemporal arch, a pineal foramen, and in lacking an ectopterygoid-palatine contact. It differs from Hoburogekko (Early Cretaceous, Mongolia) in possessing paired frontals and an U-shaped frontoparietal suture. It is diagnosed from Gobekko (Late Cretaceous, Mongolia) in possessing an anteriorly narrow frontal, an open Meckelian canal, and in lacking a pineal foramen. Our cladistic analysis suggests that Gekkota includes Hoburogekko and shares successively more remote relationships with Gobekko and a clade including amphisbaenians, dibamids and snakes. The new fossil lizard lies just outside that radiation and is morphologically close to its common ancestor, offering some of the strongest evidence to date for the snake-amphisbaenian-gekko clade. ‘Bavarisaurids’ and ‘ardeosaurids’, in contrast, constitute a polyphyletic assemblage including basal scleroglossans and one species lying outside crown-group lizards.