United States
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Joint expeditions by the American Museum of Natural History and Mongolian Academy of Sciences have recovered significant new remains of the basal monstersaur Gobiderma pulchrum. We describe these new specimens in detail and also revisit the originally described material in order to more fully understand this pivotal anguimorph taxon.
The newly discovered specimens include skull and postcranial materials that add dramatically to the understanding of the osteology of Gobiderma pulchrum. We revise the diagnosis of this species, adding to the previously published diagnosis the following character states: premaxillary nasal process is narrowest mediolaterally; postfrontal and postorbital remain unfused; postorbital extends posteriorly for almost the entire length of the supratemporal fenestra; the Vidian canal is posteriorly enclosed by the parabasisphenoid; an anterior coracoid emargination is present; the pelvis is completely fused; and the lateral plantar tubercle is distally placed. A phylogenetic analysis confirms the placement of Gobiderma pulchrum as a non-helodermatid monstersaur. As such, the fact that it is known from reasonably complete remains makes it pivotal for understanding character evolution within Monstersauria. The Djadokhta Formation includes several carnivorous/insectivorous lizards and theropod dinosaurs – more than is usual for extant communities, but perhaps analogous in some ways to parts of modern Australia.
