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A Green River (Eocene) polychrotid (Squamata: Reptilia) and a re-examination of iguanian systematics

  • Jack L. Conrad (a1), Olivier Rieppel (a2) and Lance Grande (a2)

A pleurodontan iguanian from the Green River Formation (Eocene) is described in detail and named. The new taxon is known only from a single specimen preserving all areas of the body. Although many of the bone surfaces are eroded, almost all of the skeleton is present and some cartilaginous elements are preserved. The new taxon shares important characteristics with the extant anisolepines and leiosaurines, including the morphology and placement of the caudal autotomy planes, the postxiphisternal inscriptional ribs, and notched or fenestrated clavicles that are expanded proximally. This is the earliest complete iguanian known from the Americas and the earliest known iguanian that may be confidently referred to an extant “family.” A phylogenetic analysis including this taxon and other fossil and extant iguanians offers some support for the monophyly of Polychrotidae sensu lato, Tropiduridae sensu lato, and non-acrodont iguanians (Pleurodonta).

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Abdala, V. and Moro, S. A. 2003. A cladistic analysis of ten lizards families (Reptilia: Squamata) based on cranial musculature. Russian Journal of Herpetology, 10(1):5378.
Alifanov, V. R. 1989. New priscagamids (Lacertilia) from the Upper Cretaceous of Mongolia and their systematic postion among Iguania. Paleontological Journal, 1989(4):6880.
Alifanov, V. R. 1996. Lizard families Priscagamidae and Hoplocercidae (Sauria, Iguania): Phylogenetic position and new representatives from the Late Cretaceous of Mongolia. Paleontological Journal, 1996(3):100118.
Bell, G. L. Jr. 1997. A phylogenetic revision of North American and Adriatic Mosasauroidea. In Callaway, J. M. and Nicholls, E. L. (eds.), Ancient Marine Reptiles. Volume 293–332. Academic Press, San Diego.
Bell, T. 1843. The Zoology of the Voyage of the H.M.S. Beagle, Under the Command of Captain Fitzroy, R.N., During the Years 1832-1836, Pt. 5, Reptiles. Smith, Elder, and Co., London, 51 p.
Berthold, A. A. 1845. Über verschiedene neue oder seltene Reptilien aus Neu Granada und Crustaceen aus China. Abhandlungen der Gesellschaft der Wissenschaften zu Göttingen, 3:1828.
Borsuk-Białynicka, M. 1983. The early phylogeny of Anguimorpha as implicated by craniological data. Acta Palaeontologica Polonica, 28(1-2):5105.
Borsuk-Białynicka, M. and Alifanov, V. R. 1991. First Asiatic ‘iguanid’ lizards in the Late Cretaceous of Mongolia. Acta Palaeontologica Polonica, 36(3):325342.
Borsuk-Białynicka, M. and Moody, S. M. 1984. Priscagaminae, a new subfamily of the Agamidae (Sauria) from the Late Cretaceous of the Gobi Desert. Acta Palaeontologica Polonica, 29(1-2):5181.
Branch, W. R. 1982. Hemipeneal morphology of platynotan lizards. Journal of Herpetology, 16(1):1638.
Buchheim, H. P. 1994. Paleoenvironments, lithofacies and “varves” of the Fossil Butte Member of the Eocene Green River Formation, southwestern Wyoming. Contributions to Geology, University of Wyoming, 30(1):314.
Caldwell, M. W. 1999. Squamate phylogeny and the relationships of snakes and mosasauroids. Zoological Journal of the Linnean Society, 125:115147.
Conrad, J. L. 2006. An Eocene shinisaurid (Reptilia, Squamata) from Wyoming, U.S.A. Journal of Vertebrate Paleontology, 26(1):113126.
Conrad, J. L. and Norell, M. A. 2006. High-resolution x-ray computed tomography of an Early Cretaceous gekkonomorph (Squamata) from Öösh (Övörkhangai; Mongolia). Historical Biology, PrEview, online publication date May 18:
Cope, E. D. 1864. On the characters of the higher groups of Reptilia Squamata—and especially of the Diploglossa. Proceedings of the Academy of Natural Sciences of Philadelphia, 16:224231.
Cope, E. D. 1873. Synopses of new Vertebrata from the Tertiary of the plains. Palaeontological Bulletin, 15:16.
Cope, E. D. 1885. The White River beds of Swift Current River, Northwest Territory. American Naturalist, 19:163.
DeBraga, M. and Carroll, R. L. 1993. The origin of mosasaurs as a model of macroevolutionary patterns and processes. Evolutionary Biology, 27:245322.
de Queiroz, K., Ling-Ru, C., and Losos, J. B. 1998. A second Anolis lizard in Dominican amber and the systematics and ecological morphology of Dominican amber anoles. American Museum Novitates, 3249:123.
Dingerkus, G. and Uhler, L. D. 1977. Enzyme clearing of Alcian blue stained whole small vertebrates for demonstration of cartilage. Stain Technology, 52:229232.
Estes, R. 1964. Fossil vertebrates from the Late Cretaceous Lance Formation eastern Wyoming. University of California Publications in Geological Sciences, 49:1180.
Estes, R. 1983. Sauria Terrestria, Amphisbaenia, 10. Gustav Fischer Verlag, New York, 249 p.
Estes, R., de Queiroz, K., and Gauthier, J. 1988. Phylogenetic relationships within Squamata, p. 119281. In Estes, R. and Pregill, G. (eds.), Phylogenetic Relationships of the Lizard Families. Stanford University Press, Stanford.
Etheridge, R. and de Queiroz, K. 1988. A phylogeny of Iguanidae, p. 283367. In Estes, R. and Pregill, G. (eds.), Phylogenetic Relationships of the Lizard Families. Stanford University Press, Stanford.
Evans, S. E. 1980. The skull of a new eosuchian reptile from the Lower Jurassic of South Wales. Zoological Journal of the Linnean Society, 70:203264.
Evans, S. E. 1994. A new anguimorph lizard from the Jurassic and Lower Cretaceous of England. Palaeontology, 37(1):3349.
Evans, S. E. 1998. Crown group lizards (Reptilia, Squamata) from the Middle Jurassic of the British Isles. Palaeontographica; Beiträge zur Naturgeschichte der Vorzeit, Abt. A, 250:123154.
Evans, S. E. 2003. At the feet of the dinosaurs: The early history and radiation of lizards. Biological Reviews, 78(4):513551.
Evans, S. E. and Barbadillo, L. J. 1998. An unusual lizard (Reptilia: Squamata) from the Early Cretaceous of Las Hoyas, Spain. Zoological Journal of the Linnean Society, 124:235265.
Fitzinger, L. J. 1843. Systema Reptilium (Fasiculus primus). Amblyglossae. Vindobonae, Apud Braumüller, and Seidel, Vienna, 106 p.
Frost, D. R. and Etheridge, R. 1989. A phylogenetic analysis and taxonomy of iguanian lizards (Reptilia: Squamata). University of Kansas Museum of Natural History, Miscellaneous Publications, 81:165.
Frost, D. R., Etheridge, R., Janies, D., and Titus, T. A. 2001. Total evidence, sequence alignment, evolution of polychrotid lizards, and a reclassification of the Iguania (Squamata: Iguania). American Museum Novitates, 3343:138.
Gao, K.-Q. and Fox, R. C. 1996. Taxonomy and evolution of Late Cretaceous lizards (Reptilia: Squamata) from western Canada. Bulletin of Carnegie Museum of Natural History, 33:1107.
Gao, K.-Q. and Hou, L. 1995. Iguanians from the Upper Cretaceous Djadochta Formation, Gobi Desert, China. Journal of Vertebrate Paleontology, 15(1):5778.
Gao, K.-Q. and Hou, L. 1996. Systematics and taxonomic diversity of squamates from the Upper Cretaceous Djadochta Formation, Bayan Manahu, Gobi Desert, People's Republic of China. Canadian Journal of Earth Sciences, 33(4):578598.
Gao, K.-Q. and Nessov, L. A. 1998. Early Cretaceous squamates from the Kyzylkum Desert, Uzbekistan. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen, 207(3):289309.
Gao, K.-Q. and Norell, M. A. 1998. Taxonomic revision of Carusia (Reptilia: Squamata) from the Late Cretaceous of the Gobi Desert and phylogenetic relationships of anguimorphan lizards. American Museum Novitates, 3230:1-5(1)
Gao, K.-Q. and Norell, M. A. 2000. Taxonomic composition and systematics of Late Cretaceous lizard assemblages from Ukhaa Tolgod and adjacent localities, Mongolian Gobi Desert. Bulletin of the American Museum of Natural History, 249:1118.
Gauthier, J. A. 1982. Fossil xenosaurid and anguid lizards from the early Eocene Wasatch Formation, southeast Wyoming, and a revision of the Anguioidea. Contributions to Geology, University of Wyoming, 21(7):754.
Gauthier, J. A., Estes, R., and de Queiroz, K. 1988. A phylogenetic analysis of Lepidosauromorpha. In Estes, R. and Pregill, G. (eds.), Phylogenetic Relationships of the Lizard Families. Stanford University Press, Stanford.
Gilmore, C. W. 1938. Descriptions of new and little known fossil lizards from North America. Proceedings of the United States National Museum, 86(3042):1126.
Gilmore, C. W. 1943. Fossil lizards of Mongolia. Bulletin of the American Museum of Natural History, 81:361384.
Grande, L. 1984. Paleontology of the Green River Formation, with a review of the fish fauna. Geological Survey of Wyoming, Bulletin, 63:1133.
Grande, L. 1994. Studies of paleoenvironments and historical biogeography in the Fossil Butte and Laney Members of the Green River Formation. Contributions to Geology, University of Wyoming, 30(1):1532.
Grande, L. 2001. An updated review of the fish faunas from the Green River Formation, the world's most productive freshwater Lagerstatten, p. 138. In Gunnell, G. F. (ed.), Eocene Biodiversity: Unusual occurrences and rarely sampled habitats. Kluwer Academic/Plenum Publishers, New York.
Grande, L. and Buchheim, H. P. 1994. Paleontological and sedimentological variation in Early Eocene fossil lake. Contributions to Geology, University of Wyoming, 30(1):3356.
Gray, J. E. 1827. A synopsis of the genera of saurian reptiles, in which some new genera are indicated and the others reviewed by actual examination. Annals of Philosophy, New Series, 2(2):5458.
Greer, A. E. 1985. The relationships of the lizard genera Anelytropsis and Dibamus. Journal of Herpetology, 19(1):116156.
Hanken, J. and Wassersug, R. 1981. The visible skeleton. Functional Photography, 16:2226.
Harvey, M. B. 1993. Microstructure, ontogeny, and evolution of scale surfaces in xenosaurid lizards. Journal of Morphology, 216:161177.
Hoffstetter, R. 1967. Coup d'oeil sur les Sauriens (lacertiliens) des couches de Purbeck (Jurassique supérieur d'Angleterre Résumé d'un Mémoire). Colloques Internationaux du Centre National de la Recherche Scientifique, 163:349371.
Kearney, M. 2003. Systematics of the Amphisbaenia (Lepidosauria: Squamata) based on morphological evidence from recent fossil forms. Herpetological Monographs, 17:174.
Kluge, A. G. 1967. Higher taxonomic categories of gekkonid lizards and their evolution. Bulletin of the American Museum of Natural History, 135(1):160.
Kluge, A. G. 1987. Cladistic relationships in the Gekkonoidea (Squamata, Sauria). Miscellaneous Publications: Museum of Zoology, University of Michigan, 173:154.
Lazell, J. D. Jr. 1965. An Anolis (Sauria, Iguanidae) in amber. Journal of Paleontology, 39(3):379382.
Lee, M. S. Y. 1998. Convergent evolution and character correlation in burrowing reptiles: Towards a resolution of squamate relationships. Biological Journal of the Linnean Society, 65:369453.
Lee, M. S. Y. and Caldwell, M. W. 2000 Adriosaurus and the affinities of mosasaurs, dolichosaurs, and snakes. Journal of Paleontology, 74(5):915937.
Leidy, J. 1870 (Description of Emys jeansi, E. haydeni, Bàëna arenosa, and Saniwa ensidens). Proceedings of the Academy of Natural Science, Philadelphia, 1870:123124.
Macey, J. R., Larson, A., Ananjeva, N. B., and Papenfuss, T. J. 1997. Evolutionary shifts in three major structural features of the mitochondrial genome among iguanian lizards. Journal of Molecular Evolution, 44:660674.
McDowell, S. B. Jr. and Bogert, C. M. 1954. The systematic position of Lanthanotus and the affinities of the anguinomorphan lizards. Bulletin of the American Museum of Natural History, 105(1):1142.
Norell, M. and Gao, K.-Q. 1997. Braincase and phylogenetic relationships of Estesia mongoliensis from the Late Cretaceous of the Gobi Desert and the recognition of a new clade of lizards. American Museum Novitates, 3211:125.
Oppel, M. 1811. Die Ordnungen, Familien, und Gattungen der Reptilien als Prodrom einer Naturgeschichte Derselben. Joseph Lindauer, München, 86 p.
Polcyn, M. J., Rogers, J. V. II, Kobayashi, Y., and Jacobs, L. L. 2002. Computed tomography of an Anolis lizard in Dominican amber: Systematic, taphonomic, biogeographic, and evolutionary implications. Palaeontologia Electronica, 5(1):113.
Potthoff, T. 1984. Clearing and staining techniques, p. 3537. In Moser, H. G., Richards, W. J., Cohen, D. M., Fahay, M. P., Kendall, A. W. Jr., and Richardson, S. L. (eds.), Ontogeny and Systematics of Fishes. Volume 1. American Society of Ichthyologists and Herpetologists Special Publication, Lawrence.
Pough, F. H., Andrews, R. M., Cadle, J. E., Crump, M. L., Savitzky, A. H., and Wells, K. D. 2001. Herpetology. Prentice Hall, Upper Saddle River, 612 p.
Pregill, G. K., Gauthier, J. A., and Greene, H. W. 1986. The evolution of helodermatid squamates, with description of a new taxon and an overview of Varanoidea. Transactions of the San Diego Society of Natural History, 21:167202.
Renous-Lécuru, S. 1968. Etude des variations morphologiques du sternum, des clavicules et de l'interclavicule des lacertiliens. Annales des Sciences Naturelles, Zoologie, Paris, 10:511544.
Rieppel, O. 1980a. Green anole in Dominican amber. Nature, 286:486487.
Rieppel, O. 1980b. The Phylogeny of Anguinimorph Lizards. Naturforschenden Gesellshaft, Basel, 86 p.
Rieppel, O. 1980c. The postcranial skeleton of Lanthanotus borneensis (Reptilia, Lacertilia). Amphibia-Reptilia, 1:95112.
Rieppel, O. 1994. The Lepidosauromorpha: An overview with special emphasis on the Squamata, p. 2337. In Fraser, N. C. and Sues, H.-D. (eds.), In the Shadow of the Dinosaurs: Early Mesozoic Tetrapods. Cambridge University Press, Cambridge.
Rieppel, O. and Zaher, H. 2000. The braincases of mosasaurs and Varanus, and the relationships of snakes. Zoological Journal of the Linnean Society, 129(4):489514.
Rossmann, T. 1999. Messelosaurine lacertilians (Squamata: Iguanoides) from the Pelaeogene of France and North America. Neues Jahrbuch für Geologie und Paläontologie, Monatshefte, 1999(10):577592.
Rossmann, T. 2000. Osteologische Beschreibung von Geiseltaliellus longicaudus Kuhn, 1944 (Squamata: Iguanoidea) aus dem Mittleren Eozän der Fossillagerstätten Geiseltal und Grube Messel (Deutschland), mit einer Revision der Gattung Geiseltaliellus. Palaeontographica Abteilung a Palaeozoologie Stratigraphie, 258(4-6):117158.
Rossmann, T. 2001. Geiseltaliellus longicaudus Kuhn (Lacertilia: Iguanoidea) aus dem Eozän von Mitteleuropa: Neue Erkenntnisse zur Paläobiologie und Paläobiogeographie [Geiseltaliellus longicaudus Kuhn (Lacertilia: Iguanoidea) from the Eocene of central Europe: New palaeobiological and palaeobiogeographical results]. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen, 221(1):133.
Schulte, J. A. II, Valladares, J. P., and Larson, A. 2003. Phylogenetic relationships within Iguanidae inferred using molecular and morphological data and a phylogenetic taxonomy of iguanian lizards. Herpetologica, 59(3):399419.
Schwenk, K. 1988. Comparative morphology of the lepidosaur tongue and its relevance to squamate phylogeny, p. 569597. In Estes, R. and Pregill, G. (eds.), Phylogenetic Relationships of the Lizard Families. Stanford University Press, Stanford.
Swofford, D. L. 2001. PAUP. Smithsonian Institution, Washington, DC.
Titus, T. A. and Frost, D. R. 1996. Molecular homology assessment and phylogeny in the lizard family Opluridae (Squamata: Iguania). Molecular Phylogenetics and Evolution, 6(1):4962.
Torres-Carvajal, O. 2004. The abdominal skeleton of tropidurid lizards (Squamata: Tropiduridae). Herpetologica, 60(1):7583.
Townsend, T. M., Larson, A., Louis, E., and Macey, J. R. 2004. Molecular phylogenetics of Squamata: the position of snakes, amphisbaenians, and dibamids, and the root of the squamate tree. Systematic Biology, 53(5):735757.
Uetz, P. 2005. The EMBL Reptile Database. European Molecular Biology Laboratory, Heidelberg.
Vidal, N. and Hedges, S. B. 2004. Molecular evidence for a terrestrial origin of snakes. Proceedings of the Royal Society of London: series B (biological sciences), 271 (suppl.):S226S229.
Voigt, L. 1832. p. 71, Das Thierreich von Cuvier, übersetz und durch Zusätze erweitert. Leipzig. Volume 2.
Whiteside, D. I. 1986. The head skeleton of the Rhaetian Sphenodontid Diphydontosaurus avonis gen. et sp. nov. and the modernizing of a living fossil. Philosophical Transactions of the Royal Society of London, Series B: Biological Sciences, 312:379430.
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