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Upper Cretaceous deposits at Ukhaa Tolgod and adjacent localities in the Mongolian Gobi Desert have yielded a large number of superbly preserved lizard specimens, including representatives of several new taxa (described in this paper) and important supplementary material of several previously poorly known taxa. Study of these specimens gives important insight into the taxonomic diversity and systematics of the Late Cretaceous lizard fauna of the Gobi Desert. A preliminary survey indicates that the lizard assemblage from Ukhaa Tolgod and adjacent localities consists of some 30 species in four higher groups (Iguania, Gekkota, Scincomorpha, and Anguimorpha). The iguanians are documented by eight species, including three species newly recognized in this paper. The Scincomorpha are the most diverse group, represented by as many as 14 species including three new and 11 previously known species. The Anguimorpha are nearly as diverse as the Iguania, while the Gekkota is the least diverse group with a single species documented in the assemblage. The scincomorphs include forms that are highly specialized for burrowing life-styles, interpreted from their cranial morphology as possibly analogous to extant species. The anguimorphs include phylogenetically important basal members of several major anguimorph clades.
The paleoecological significance of these lizards cannot be overlooked. According to tooth morphology, most lizards are predatory in terms of habit, while true herbivorous species are rare. Most specimens are preserved as skulls articulated with mandibles, but virtually complete skeletons in situ are quite common. Delicate parts of the skull, such as the braincase and ear ossicles, are undistorted and the surfaces of the bones show no sign of sand abrasion. These observations indicate not only relatively quick burial but also burial under relatively mesic climatic conditions with low-energy water involved during the taphonomic process.