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Polyglyphanodontia
Polyglyphanodontia is an extinct clade of lizards from the Cretaceous that includes around a dozen genera. Polyglyphanodontians were the dominant group of lizards in North America〔Longrich, N. R., A.-B. S. Bhullar, et al. (2012). "Mass extinction of lizards and snakes at the Cretaceous-Paleogene boundary." Proceedings of the National Academy of Sciences 109(52): 21396--21401.〕 and Asia〔Gao, K. and L. Hou (1996). "Systematics and taxonomic diversity of squamates from the Upper Cretaceous Djadochta Formation, Bayan Mandahu, Gobi Desert, People's Republic of China." Canadian Journal of Earth Sciences 33(4): 578-598.〕 during the Late Cretaceous. Most polyglyphanodontians are Late Cretaceous in age, though the oldest one, ''Kuwajimalla kagaensis'', is known from the Early Cretaceous (Valanginian to Hauterivian) Kuwajima Formation (Japan). Early Cretaceous South American taxon ''Tijubina'', and possibly also ''Olindalacerta'', might also fall within Polyglyphanodontia or be closely allied to the group, but if so, they would be the only known Gondwanan examples of an otherwise Laurasian clade. They produced a remarkable range of forms. Chamopsiids, including ''Chamops'', were characterized by large, blunt, crushing teeth, and were most likely omnivores. ''Macrocephalosaurus'', from the Gobi Desert, was a specialized herbivore; it grew to roughly a meter long and had multicusped, leaf-shaped teeth like those of modern iguanas. ''Polyglyphanodon'', from the Maastrichtian of Utah, was another herbivore, but its teeth formed a series of transverse blades, similar to those of ''Trilophosaurus''. ''Peneteius'' had remarkable, multicusped teeth, similar to those of mammals. The polyglyphanodontids first appear in the latter part of the Early Cretaceous in North America, and became extinct during the Cretaceous-Paleogene extinction event. Polyglyphanodontians closely resembled the teiid lizards, and purported teiid lizards from the Late Cretaceous appear to be polyglyphanodontians.
A large-scale phylogenetic analysis of squamates conducted by Conrad (2008) found polyglyphanodontians (called Polyglyphanodontidae by Conrad) to be closely related to teiid lizards. In the strict consensus tree recovered in the analysis, polyglyphanodontids were part of a polytomy (unresolved evolutionary relationship) with teiids, gymnophthalmids, ''Chamops'' and lacertids; in the Adams consensus tree polyglyphanodontids were the sister group to teiids. (Some other studies that recognize a close relationship between polyglyphanodontians and teiids use the name Borioteiioidea rather than Polyglyphanodontia, although Borioteiioidea encompasses only North American polyglyphanodontians.) Conrad's analysis also recovered ''Sineoamphisbaena'', a Cretaceous lizard that resembles legless amphisbaenian lizards, as a member of Polyglyphanodontidae.〔 On the other hand, a later large-scale phylogenetic analysis of fossil and living squamates published in 2012 by Gauthier ''et al.'' found that Polyglyphanodontia was not particularly closely related to teiids, but rather that it was the sister taxon of the clade containing the extinct marine mosasaurs, their closest relatives and the major lizard group Scleroglossa. Because the first scleroglossans appear in the Late Jurassic, polyglyphanodontians must also have originated in the Late Jurassic if this phylogeny is correct. However, polyglyphanodontians are limited to the Cretaceous, meaning that a long ghost lineage may exist.〔 The primary analysis of Gauthier ''et al.'' (2012) did not find polyglyphanodontians and ''Sineoamphisbaena'' to be closely related; however, the authors noted that when all snake-like squamates and mosasaurs were removed from the analysis, and burrowing squamates were then added individually to it, ''Sineoamphisbaena'' grouped with polyglyphanodontians. Gauthier ''et al.'' (2012) considered it possible that ''Sineoamphisbaena'' was a burrowing polyglyphanodontian,〔 though, agreeing with.〔 Subsequent analyses based on 〔 have also supported ''Sineoamphisbaenia'' as a polyglyphanodontian (the combined molecular and morphological analysis of Müller et al.;〔Johannes Müller, Christy Hipsley, Jason Head, Nikolay Kardjilov, André Hilger, Michael Wuttke, & Robert Reisz. Eocene lizard from Germany reveals amphisbaenian origins. Nature 473: 364-367 (2011).〕 in the morphology only analyses carried out by Wiens et al. but not their combined molecular and morphological analyses;〔 and in morphology only analyses carried out by 〔Mo J-Y, Xu X, Evans SE. 2010. The evolution of the lepidosaurian lower temporal bar: new perspectives from the Late Cretaceous of South China. Proc Roy Soc B 277:1679: 331–336.〕〔XU, L., WU, X., Junchang, L., JIA, S., ZHANG, J., PU, H. and ZHANG, X. (2014), A New Lizard (Lepidosauria: Squamata) from the Upper Cretaceous of Henan, China. Acta Geologica Sinica, 88: 1041–1050. doi: 10.1111/1755-6724.12271〕 who were describing new polyglyphanodontians from Asia (and ''Tianyusaurus'' )).
A phylogenetic analysis conducted by Reeder ''et al.'' (2015) based on combined molecular and morphological data (based on 〔) recovered Polyglyphanodontia as members of Toxicofera; specifically, it was recovered as the sister group of Iguania. Lee (2009) analyzed a combined molecular and morphological data set (based on earlier studies by Lee〔Michael S.Y. Lee. Squamate phylogeny, taxon sampling and data congruence. Org Divers Evol 5: 25-45 (2005).〕〔Michael S.Y. Lee. Molecular evidence and marine snake origins. Biology Letters 1: 227-230 (2005).〕) and also had found polyglyphanodontians as the sister to iguanians but Lee's finding was not acknowledged by.〔 Combined molecular and morphological data analyses using Conrad's data 〔〔John Wiens, Caitlin Kuczynski, Ted Townsend, Tod Reeder, Daniel Mulcahy, and Jack Sites, Jr. Combining phylogenomics and fossils in higher-level squamate reptile phylogeny: molecular data change the placement of fossil taxa. Syst Biol 59 (6), 674-688 (2010).〕 consistently found polyglyphanodontians as the sisters to teiioids.
==References==
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