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A Production of

Eosaniwa koehniFossil, 'Necrosaur'
Dr. Olivier Rieppel - Field Museum of Natural History
Jack L. Conrad, Jessica A. Maisano
Eosaniwa koehni
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skull
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Geiseltal Museum (GM XXXVIII/57) - holotype

Image processing: Dr. Jessie Maisano
Publication Date: 18 Jun 2007

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The imagery on this page is the basis for a paper entitled New Morphological Data for Eosaniwa koehni Haubold, 1977 and a Revised Phylogenetic Hypothesis, by O. Rieppel, J.L. Conrad, and J.A. Maisano (2007, Journal of Paleontology 81:760-769). The abstract is as follows:

       Eosaniwa koehni is an enigmatic platynotan that differs from related varanoids in the possession of a        very long snout resulting in extremely elongate nasals and vomers; a robust and broad jugal; the        presence of denticles on palatines, pterygoids, and vomers; the presence of a subdental shelf on the        dentary; and a strongly twisted retroarticular process on the mandible. Phylogenetic analysis suggests        that Eosaniwa is a derived varanoid platynotan, nested within a clade also including mosasauroids,        Coniasaurus, and Paravaranus.

About the Species

This specimen, the holotype and only known specimen of Eosaniwa, was collected in 1964 in the Middle Eocene Geiseltal deposits near Neumark Süd. It comprises a skull (approximately 190 mm long) exposed in ventral view, associated with fully disarticulated and poorly preserved postcranial remains that are tightly lumped together with elements from a crocodile (Diplocynodon sp.). The specimen is transfer prepared on an epoxy plate. Only the portion of the slab containing the skull was scanned.

The specimen was made available to The University of Texas High-Resolution X-ray CT Facility for scanning by Dr. Olivier Rieppel of the Field Museum of Natural History and Dr. Jessie Maisano of The University of Texas at Austin. Funding for scanning and image processing was provided by Dr. Rieppel and by a National Science Foundation Assembling the Tree of Life grant (EF-0334961), The Deep Scaly Project: Resolving Squamate Phylogeny using Genomic and Morphological Approaches, to Drs. Jacques Gauthier of Yale University, Maureen Kearney of the Field Museum, Jessie Maisano of The University of Texas at Austin, Tod Reeder of San Diego State University, Olivier Rieppel of the Field Museum, Jack Sites of Brigham Young University, and John Wiens of SUNY Stonybrook.

Dorsal view of specimen (ventral aspect of skull)

About this Specimen

Download a Winzipped, unreduced, cropped, 8-bit TIFF version of the original CT dataset here (83mb).

The specimen was scanned on the P250D high-energy subsystem at the High-Resolution X-ray CT Facility by Matthew Colbert on 30 November-1 December 2004. It was scanned along the long axis of the slab for a total of 691 slices. Each slice is 0.25 mm thick with an interslice spacing of 0.20 mm, resulting in a slice overlap of 0.05 mm. The field of reconstruction was 189 mm. The images were exported as 16-bit, 1024x1024 pixel TIFF images.

Additional scanning parameters were as follows: 420 kV, 1.8 mA, 160% offset, no filter, empty container wedge, S.O.D. 580 mm, 1340 views, 1 ray per view, reconstruction offset 8000, reconstruction scale 2000.

About the
Scan

Literature

ALIFANOV, V. R. 2000. The fossil record of Cretaceous lizards from Mongolia, p. 368-389. In M. J. Benton, M. A. Shishkin, D. M. Unwin, and E. N. Kurochkin (eds.), The Age of Dinosaurs in Russia and Mongolia. Cambridge University Press, Cambridge.

BAUR, G. 1890. On the characters and systematic position of the large sea-lizards, Mosasauridae. Science, 16:262.

BELLAIRS, A. 1949. Observations on the snout of Varanus, and a comparison with that of other lizards and snakes. Journal of Anatomy, 83:116-146.

BORSUK-BIALYNICKA, M. 1984. Anguimorphans and related lizards from the Late Cretaceous of the Gobi Desert, Mongolia. Palaeontologia Polonica, 46:5-105.

BULLET, P. 1941. Beiträge zur Kenntnis des Gebisses von Varanus salvator Laur. Viertejahresschrift der Naturforschenden Gesellschaft in Zurich, 87:139-192.

CALDWELL, M. W. 1999. Squamate phylogeny and the relationships of snakes and mosasauroids. Zoological Journal of the Linnean Society, 125:115-147.

CALDWELL, M. W. 2000. On the aquatic squamate Dolichosaurus longicollis Owen, 1850 (Cenomanian, Upper Cretaceous), and the evolution of elongate necks in squamates. Journal of Vertebrate Paleontology, 20(4):720-735.

CAMP, C. L. 1923. Classification of the lizards. Bulletin of the American Museum of Natural History, 48:289-481.

CONRAD, J. L. 2004a. Re-analysis of anguimorph (Squamata: Reptilia) phylogeny with comments on some problematic taxa. Journal of Vertebrate Paleontology, 24 (suppl. 3):47A.

CONRAD, J. L. 2004b. Skull, mandible, and hyoid of Shinisaurus crocodilurus Ahl (Squamata, Anguimorpha). Zoological Journal of the Linnean Society, 141:399-434.

ESTES, R. 1983. Sauria terrestria, Amphisbaenia. Gustav Fischer Verlag, New York, 10, 249 p.

EVANS, S. E., AND L. J. BARBADILLO. 1998. An unusual lizard (Reptilia: Squamata) from the Early Cretaceous of Las Hoyas, Spain. Zoological Journal of the Linnean Society, 124:235-265.

FÜRBRINGER, M. 1900. Zur vergleichenden Anatomie Brustschulterapparates und der Schultermuskeln. Janaische Zeitschrift für Naturwissenschaft, 34:215-718.

GAO, K.-Q., AND M. A. NORELL. 1998. Taxonomic revision of Carusia (Reptilia: Squamata) from the Late Cretaceous of the Gobi Desert and phylogenetic relationships of anguimorphan lizards. American Museum Novitates, 3230:1-51.

HAUBOLD, H. 1977. Zur Kenntnis der Sauria (Lacertilia) aus dem Eozän des Geiseltales, p. 107-122. In H. H. Matthes and B. Thaler (eds.), Eozäne Wirbeltiere des Geiseltales.Volume 2. Wissenschaftliche Beiträge, Wittenberg.

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, 65:369-453.

LEE, M. S. Y. 2000. Soft anatomy, diffuse homoplasy, and the relationships of lizards and snakes. Zoologica Scripta, 29(2):101-130.

LEE, M. S. Y., AND M. W. CALDWELL. 2000. Adriosaurus and the affinities of mosasaurs, dolichosaurs, and snakes. Journal of Paleontology, 74(5):915-937.

NORELL, M., AND K.-Q. GAO. 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, 3211:1-25.

PREGILL, G. K., J. A. GAUTHIER, AND H. W. GREENE. 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, 21:167-202.

SWOFFORD, D. L. 2001. PAUP. Smithsonian Institution, Washington, DC.

WU, X.-C., D. B. BRINKMAN, AND A. P. RUSSELL. 1996. Sineoamphisbaena hexa tabularis, an amphisbaenian (Diapsida: Squamata) from the Upper Cretaceous redbeds at Bayan Mandahu (Inner Mongolia, People's Republic of China), and comments on the phylogenetic relationships of the Amphisbaenia. Canadian Journal of Earth Sciences, 33(4):541-577.

ZAHER, H., AND O. RIEPPEL. 1999. Tooth implantation and replacement in squamates, with special reference to mosasaur lizards and snakes. American Museum Novitates, 327:1-19.

Literature
& Links
Additional
Imagery

To cite this page: Dr. Olivier Rieppel, Jack L. Conrad, Jessica A. Maisano, 2007, "Eosaniwa koehni" (On-line), Digital Morphology. Accessed November 23, 2014 at http://digimorph.org/specimens/Eosaniwa_koehni/.

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