The imagery on this page was the basis for a paper entitled Cranial anatomy of the extinct amphisbaenian Rhineura hatcherii (Squamata, Amphisbaenia) based on high-resolution X-ray computed tomography by M. Kearney, J. A. Maisano and T. Rowe (Journal of Morphology 264:1-33, 2005). The abstract is as follows:
The fossilized skull of a small extinct amphisbaenian referable to Rhineura hatcherii Baur is described from high-resolution X-ray computed tomographic (HRXCT) imagery of a well-preserved mature specimen from the Brule Formation of Badlands National Park, South Dakota. Marked density contrast between bones and surrounding matrix and at bone-to-bone sutures enabled the digital disarticulation of individual skull elements (see Additional Imagery). These novel visualizations provide insight into the otherwise inaccessible three-dimensionally complex structure of the bones of the skull and their relationships to one another, and to the internal cavities and passageways that they enclose. This study corrects several previous misidentifications of elements in the rhineurid skull and sheds light on skull construction generally in shovel-headed amphisbaenians. The orbitosphenoids in R. hatcherii are paired and entirely enclosed within the braincase by the frontals; this is in contrast to the condition in many extant amphisbaenians, in which a large azygous orbitosphenoid occupies a topologically distinct area of the skull, closing the anterolateral braincase wall. Rhineura hatcherii retains a vestigial jugal and a partially fused squamosal, both of which are absent in many extant species. Sculpturing on the snout of R. hatcherii represents perforating canals conveying sensory innervation; thus, the face of R. hatcherii receives cutaneous innervation to an unprecedented degree. The HRXCT data (available at www.digimorph.org) corroborate and extend previous hypotheses that the mechanical organization of the head in Rhineura is organized to a large degree around its burrowing lifestyle.
DigiMorph Account of Rhineura hatcherii
Rhineura is a member of Amphisbaenia, a lineage (160 species) of mostly limbless burrowing squamates. The amphisbaenian skull classically has been difficult to study due to its small size (this specimen measures just 1.5 cm in length) and largely closed construction, but high-resolution industrial CT offers a solution to these problems.
There are four major amphisbaenian groups: Bipedidae, the only one to have forelimbs; Amphisbaenidae, the most diverse (149 species) and widespread lineage (see Anops kingii and Loveridgea ionidesii); Trogonophidae, whose members use an oscillating excavation pattern (see Diplometopon zarudnyi); and Rhineuridae, to which Rhineura belongs. Amphisbaenians occur in northern and sub-saharan Africa, southwest Asia, the Mediterranean, South America east of the Andes, the West Indies, western Mexico, Baja California, the southeasternmost United States, and Cuba. They are poorly represented in collections, and little is known of their life history, because of their burrowing lifestyle.
Rhineuridae includes a number of fossil forms (all restricted to western North America) but only one living species – Rhineura floridana – which occurs in central Florida and Georgia. The specimen featured here is referable to Rhineura hatcherii, known from the Middle to Upper Oligocene of South Dakota, Nebraska, and Colorado. Rhineura hatcherii is very similar to R. floridana, but differs in part in having up to seven maxillary and dentary teeth and a sagittal crest. |
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Literature
Baur G. 1893. The discovery of Miocene amphisbaenians. American Naturalist 27:998–999.
Bellairs Ad'A, Gans C. 1983. A reinterpretation of the amphisbaenian orbitosphenoid. Nature (London) 302:243–244.
Berman DS. 1973. Spathorhynchus fossorium, a Middle Eocene amphisbaenian (Reptilia) from Wyoming. Copeia 1973:704–721.
Berman DS. 1976. A new amphisbaenian (Reptilia: Amphisbaenia) from the Oligocene-Miocene John Day Formation, Oregon. Journal of Paleontology 50:165–174.
Cope ED. 1900. Crocodilians, lizards and snakes of North America. Annual Report of the US National Museum 1898:153–1270.
deBeer GR. 1937. The development of the vertebrate skull. Oxford: Oxford University Press. 552 p.
Eigenmann CH. 1902. The eyes of Rhineura floridana. Washington Academy of Sciences Proceedings 4:533–548.
Estes R. 1983. Sauria terrestria, Amphisbaenia. Handbuch der Paläoherpetologie, Teil 10A. Stuttgart: Gustav Fischer Verlag. 249 p.
Estes R, de Queiroz K, Gauthier J. 1988. Phylogenetic relationships within Squamata. In: Estes R, Pregill G, editors. Phylogenetic relationships of the lizard families: essays commemorating Charles L. Camp. Stanford: Stanford University Press. p 119–281.
Gabe M, Saint Girons H. 1976. Contribution a la morphologie comparée des fosses nasales et de leurs annexes chez les lépiodsauriens. Mémoires du Muséum National d'Histoire Naturelle A98:1-87 (+ plates).
Gans C. 1960. Studies on amphisbaenids (Amphisbaenia, Reptilia). 1. A taxonomic revision of the Trogonophinae and a functional interpretation of the amphisbaenid adaptive pattern. Bulletin of the American Museum of Natural History 119:129–204.
Gans C. 1974. Biomechanics. An approach to vertebrate biology. Philadelphia: JP Lippincott. 261 p.
Gans C. 1978. The characteristics and affinities of the Amphisbaenia. Transactions of the Zoological Society London 34:347–416.
Gans C, Wever E. 1972. The ear and hearing in Amphisbaenia (Reptilia). Journal of Experimental Zoology 179:17–34.
Gans C, Wever E. 1975. The amphisbaenian ear: Blanus cinereus and Diplometopon zarudnyi. Proceedings of the National Academy of Sciences 72:1487–1490.
Gilmore CW. 1928. Descriptions of new and little-known fossil lizards from North America. Proceedings of the US National Museum 86:11–26.
Jollie MT. 1960. The head skeleton of the lizard. Acta Zoologica 41:1–64.
Kearney M. 2003. Systematics and evolution of the Amphisbaenia (Reptilia: Squamata) based on morphological evidence from fossil and living forms. Herpetological Monographs 17:1-74.
Kearney M, Maisano JA, Rowe T. 2005. Cranial anatomy of the extinct amphisbaenian Rhineura hatcherii (Squamata, Amphisbaenia) based on high-resolution X-ray computed tomography. Journal of Morphology (in press).
Kesteven L. 1957. Notes on the skull and cephalic muscles of the Amphisbaenia. Proceedings of the Linnean Society New South Wales 82:109–116.
Kritzinger CC. 1946. The cranial anatomy and kinesis of the South African amphisbaenid Monopeltis capensis Smith. South African Journal of Science 42:175–204.
Lakjer T. 1927. Studien über die Gaumenregion bei Sauriern im Vergleich mit Anamniern und primitiven Sauropsiden. Zoologische Jahrbucher (Anatomie) 49:57–356.
McMahon T, Bonner JT. 1983. On size and life. New York: Scientific American Library. 255 p.
Montero R, Gans C. 1999. The head skeleton of Amphisbaena alba Linnaeus. Annals Carnegie Museum 68:15–80.
Montero R, Gans C, Lions M. 1999. Embryonic development of the skeleton of
Amphisbaena darwini heterozonata (Squamata:Amphisbaenidae). Journal of Morphology 239:1–25.
Oelrich TM. 1956. The anatomy of the head of Ctenosaura pectinata (Iguanidae). Miscellaneous Publications Museum of Zoology University of Michigan 94:1–122.
Olson EC. 1995. Introduction to Thrinaxodon, digital atlas of the skull. In: Rowe T, Carlson W, Bottorff W, editors. Thrinaxodon: digital atlas of the skull. CD-ROM (Second Edition). Austin: University of Texas Press. 547 megabytes.
Patterson C. 1977. Cartilage bones, dermal bones and membrane bones, or the exoskeleton versus the endoskeleton. In: Andrews S, Miles M, Walker AD, editors. Problems in vertebrate evolution. London: Academic Press. p 77–121.
Rieppel O. 1981. The skull and the jaw adductor musculature in some burrowing scincomorph lizards of the genera Acontias, Typhlosaurus and Feylinia. Journal of Zoology 195:493–528.
Romer AS. 1956. Osteology of the reptiles. Chicago: University of Chicago Press. 772 p.
Rowe T. 1986. Homology and evolution of the deep dorsal thigh musculature in birds and other Reptilia. Journal of Morphology 198:327–346.
Rowe T, Kappelman J, Carlson WD, Ketcham RA, Denison C. 1997. High-resolution computed tomography: a breakthrough technology for Earth scientists. Geotimes 42:23–27.
Schwenk K. 1993. Are geckos olfactory specialists? Journal of Zoology London 229:289-302.
Starck D. 1979. Vergleichende Anatomie der Wirbeltiere auf evolutionsbiologischer Grundlage. Volume 2. Das Skeletsystem Allgemeines, Skeletsubstanzen, Skelet der Wirbeltiere einschlieblich Lokomotionstypen. Berlin: Springer Verlag. 776 p.
Taylor EH. 1951. Concerning Oligocene amphisbaenid reptiles. University of Kansas Science Bulletin 34:521–579.
Vanzolini PE. 1951. Evolution, adaptation and distribution of the amphisbaenid lizards (Sauria: Amphisbaenidae). Thesis, Harvard University. 148 p.
Zangerl R. 1944. Contributions to the osteology of the skull of the Amphisbaenidae. American Midland Naturalist 31:417–454.
Links
More information on the geology of the White River Formation and Badlands National Park from the National Park Service
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