A Morrison stem gekkotan reveals gecko evolution and Jurassic biogeography

Geckos are a speciose and globally distributed clade of Squamata (lizards,
including snakes and amphisbaenians) that are characterized by a host of
modifications for nocturnal, scansorial, and insectivorous ecologies. They
are among the oldest divergences in the lizard crown, so understanding the
origin of geckoes (Gekkota) is essential to understanding the origin of
Squamata, the most species-rich extant tetrapod clade. However, the poor
fossil record of gekkotans has obscured the sequence and timing of the
assembly of their distinctive morphology. Here, we describe the first
North American stem-gekkotan based on a three-dimensionally preserved
skull from the Morrison Formation of western North America. Despite its
Late Jurassic age, the new species already possesses several key
characteristics of the gekkotan skull along with retained ancestral
features. We show that this new stem gekkotan, and several previously
named species of uncertain phylogenetic relationships, comprise a
widespread clade of early crown lizards, substantiating faunal homogeneity
in Laurasia during the Late Jurassic that extended across disparate
ecological, body-size, and physiological classes.