The early Cretaceous lizard genus Yabeinosaurus from China: resolving an enigma

摘要

The lizard genus Yabeinosaurus was originally described more than 60 years ago from deposits of the Early Cretaceous Jehol Group of northeastern China. Its morphology and phylogenetic position have remained enigmatic for several reasons, not least the inaccessibility of the type and figured material, now lost, and the immaturity of all previously documented specimens. Recent work on the Jehol Biota has yielded a series of well-preserved Yabeinosaurus skeletons, ranging from juvenile to adult. Contrary to previous interpretations, Yabeinosaurus was not a small, weakly ossified lizard with gekkotan affinities. The adult reached a size in excess of 300 mm snout-pelvis length and had a large, heavily ossified and strongly sculptured skull. Phylogenetic analysis highlights some of the difficulties involved in determining the systematic positions of early squamate taxa. Nevertheless, the overall results suggest a position close to the iguanian-scleroglossan dichotomy (just above or just below). As such, Yabeinosaurus may represent a relict taxon in the Jehol Biota, a survivor of the Pan-Laurasian lizard fauna of the Jurassic.