DOI: 10.15468/da6tg7
title: A Complete Late Cretaceous Iguanian (Squamata, Reptilia) from the Gobi and Identification of a New Iguanian Clade

description: This dataset contains the digitized treatments in Plazi based on the original journal article CONRAD, JACK L., NORELL, MARK A. (2007): A Complete Late Cretaceous Iguanian (Squamata, Reptilia) from the Gobi and Identification of a New Iguanian Clade. American Museum Novitates 3584 (1): 1-48, DOI: 10.1206/0003-0082(2007)3584[1:ACLCIS]2.0.CO;2, URL: http://www.bioone.org/perlserv/?request=get-abstract&doi=10.1206%2F0003-0082(2007)3584%5B1%3AACLCIS%5D2.0.CO%3B2ABSTRACTIguania is a diverse clade with an incompletely known fossil record. Here, we describe and name the earliest iguanian known from a complete skeleton. The specimen (IGM 3/858) comes from Ukhaa Tolgod (Upper Cretaceous of Mongolia) and offers important insights into the evolutionary history of iguanian osteology. The new taxon is diagnosed by a combination of character states, including the presence of a frontoparietal fontanelle, absence of an enlarged nuchal fossa, and unflared tooth crowns. We performed a cladistic analysis including 54 taxa scored for 202 informative morphological characters. A strict consensus of 46 shortest recovered trees reveals that the new taxon is a basal member of a previously unidentified clade of Cretaceous iguanians, probably endemic to the Gobi. This clade of Gobi iguanians is nested within a monophyletic Pleurodonta (non-acrodontan iguanians).INTRODUCTIONIguania is a remarkably diverse squamate clade spanning five continents and occupying a variety of ecological niches and habitat types (Frost and Etheridge, 1989; Bauer, 2003; Uetz, 2006). Despite their extant diversity of form and the large number of species represented in modern faunas (Frost and Etheridge [1989] reports 993 extant species; Uetz’s [2006] count suggests 1,442), the iguanian fossil record is very incomplete, especially prior to the Neogene.The past decade has seen a dramatic increase in the discovery of fossil iguanian material. Especially surprising is the large amount of diversity from continental Asia. Gao and Hou (1995) described Anchaurosaurus gilmorei based on an incomplete skeleton in 1995. Later, Gao and Norell (2000) described a wealth of new1 Division of Paleontology, American Museum of Natural History (jconrad@amnh.org).2 Division of Paleontology, American Museum of Natural History (norell@amnh.org).material from the Mongolian Late Cretaceous relating to previously described taxa (Isodontosaurus gracilis, Mimeosaurus crassus, Phrynosomimus asper, Priscagama gobiensis, and Polrussia mongoliensis) and several new taxa (Ctenomastax parva, Temujinia ellisoni, and Zapsosaurus sceliphros) discovered as part of the Mongolian Academy of Science–American Museum of Natural History expeditions. Consequently, our knowledge of the Cretaceous iguanian fauna from the Gobi and our understanding of iguanian morphology have increased dramatically.Many fossil lizards are known from Ukhaa Tolgod, a ‘ ‘Djadockhta-like’’ locality whose geology recently has been reviewed and summarized (Loope et al., 1998; Gao and Norell, 2000; see also references therein). Ukhaa Tolgod has been and continues to be an immensely productive ‘ ‘fossil bonanza’’ (Gao and Norell, 2000: 7), yielding the remains of numerous tetrapods, including mammals; many saurischian and ornithischian dinosaurs; and thousands of lizard specimens. Among the most breathtaking of the lizard specimens collected on these recent expeditions is a complete iguanian (fig. 1). Although it was illustrated in Gao and Norell (2000: fig. 37), we describe this new taxon here for the first time.In addition to naming the new Ukhaa Tolgod iguanian, we present a phylogenetic data matrix to identify its placement on the iguanian family tree. The new taxon shares important characteristics with some other Cretaceous iguanians from the Gobi. Together, these early iguanians offer new insights into the evolutionary history of Iguania.