The imagery on this page is the basis for a paper entitled Cranial Osteology of the African Gerrhosaurid Angolosaurus skoogi (Squamata; Gerrhosauridae), by H. A. Nance (2007, African Journal of Herpetology 56:39-75). The abstract is as follows:

       Phylogenetic relationships both within and between the scincomorph families Gerrhosauridae and        Cordylidae are in need of re-examination. Currently the basal gerrhosaurid is unknown, although        Angolosaurus skoogi previously was proposed as the sister taxon to mainland African gerrhosaurids.        Many details of the cranial osteology of A. skoogi are also unknown because of the rarity in museum        collections and elusive lifestyle of this dune-dwelling lizard, endemic to the Namib Desert. In this        study, High-Resolution X-ray Computed Tomography (HRXCT) was used to study in detail the cranial        osteology of A. skoogi. Results of this study enabled completion of the first anatomical description of        the skull and mandible of A. skoogi. Throughout the description, reference is made to a fully labeled        cross-sectional HRXCT data set, available online as supplementary material. Detailed information on        cranial osteology obtained from these data can help resolve the contentious placement of A. skoogi        within Gerrhosauridae. Unlike other Cordyliformes (Gerrhosauridae + Cordylidae), the postfrontal in A.        skoogi is not extensive and does not extend posteriorly beyond the orbital margin. The squamosal is        not bifurcated anteriorly in A. skoogi, unlike other gerrhosaurids. In the braincase of A. skoogi, there        is no separate foramen for passage of the glossopharyngeal nerve (cranial nerve IX). This        morphological study emphasizes the utility of both HRXCT scans and disarticulated skeletal material as        valuable sources of phylogenetically-informative data.

This specimen was collected near the Ondonduiergo River, Opuwo District, Kunene Region, Namibia by A.M. Bauer, A.C. Lamb, W.R. Branch and J.L. Wright on 27 July 1998. It was made available to The University of Texas High-Resolution X-ray CT Facility for scanning by Dr. Chris Bell of The University of Texas at Austin. Funding for scanning was provided by Dr. Bell. Funding for image processing was provided by a NSF Digital Libraries Initiative grant to Dr. Timothy Rowe of The University of Texas at Austin.

This specimen was scanned by Richard Ketcham and Matthew Colbert on 18 March 1999 along the coronal axis for a total of 300 slices. Each 512x512 pixel slice is 0.05 mm thick, with an interslice spacing of 0.05 mm and a field of reconstruction of 10 mm.

Literature

ANDERSSON, L.G. 1916. Notes on the reptiles and batrachians in the Zoological Museum at Gothenburg with an account of some new species. Göteborgs Kungliga Vetenskap och Vitter Hets-Samnalles Handlingar Sjatte Foljden, Ser. B, Vol. 4 (Issue 17, No 5): 1-41.

AVISE, J.C. 2004. Molecular Markers, Natural History, and Evolution; Second Editon. Sinauer Associates, Inc. Publishers, Sunderland.

BAIRD, I.L. 1960. A survey of the periotic labyrinth in some representative recent reptiles. Univ. Kansas Sci. Bull. 41: 891-981.

BARAHONA, F. & L.J. BARBADILLO. 1998. Inter- and intraspecific variation in the post-natal skull of some lacertid lizards. J. Zool. 245: 393-405.

BARAHONA, F., L.F. LÓPEZ-JURADO & J.A. MATEO. 1998. Estudio anatómico del esquelto en el género Gallotia (Squamata: Lacertidae). Rev. Esp. Herp. 12: 69-89.

BARAHONA, F., S.E. EVANS, J.A. MATEO, M. GARCÍAMÁRQUEZ & L.F. LÓPEZ-JURADO. 2000. Endemism, gigantism and extinction in island lizards: the genus Gallotia on the Canary Islands. J. Zool. 250: 373- 388.

BAUR, G. 1891. The lower jaw of Sphenodon. Am. Nat. 25: 489-490.

BELLAIRS, A.D’A. & A.M. KAMAL. 1981. The chondrocranium and the development of the skull in recent reptiles. Pp. 1-263. In C. Gans & T.S. Parsons, (Eds.), Biology of the Reptilia, Vol 11, Morphology F. New York, Academic Press.

BROCHU, C.A. 2003. Society of Vertebrate Paleontology Memoir 7: Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull. J. Vert. Paleo. 22 (Supp): 1-138.

BROCK, G.T. 1935. The temporal bones in lizards, birds and mammals. Anat. Anz. 80: 266-284.

BROOM, R. 1935. On the structure of the temporal region in lizard skulls. Ann. Transvaal Mus. 18: 13- 22.

COPE, E.D. 1864. On the characters of the higher groups of Reptilia Squamata – and especially of the Diploglossa. Proc. Acad. Natl. Sci. (Phil.) 16: 224-231.

COPE, E.D. 1871. On the homologies of some of the cranial bones of the Reptilia, and the systematic arrangement of the class. Proc. Am. Assoc. Adv. Sci. 19: 194-247.

COPE, E.D. 1892. The osteology of the Lacertilia. Proc. Am. Phil. Soc. 30: 185-221.

DE BEER, G.R. 1937. The Development of the Vertebrate Skull. Oxford, Clarendon Press.

DE QUEIROZ, K. 1987. Phylogenetic systematics of iguanine lizards: a comparative osteological study. Univ. Calif. Publ. Zool. 118: 1-216.

EDMUND, A.G. 1969. Dentition. Pp 117-200. In C. Gans, A.d’A. Bellairs & T.S. Parsons (Eds.), Biology of the Reptilia, Vol 1, Morphology A. New York, Academic Press.

ESTES, R.D., K. DE QUEIROZ & J. GAUTHIER. 1988. Phylogenetic relationships within Squamata. Pp 119-281. In R. Estes & G. Pregill (Eds.), Phylogenetic Relationships of the Lizard Families: Essays Commemorating Charles L. Camp. Stanford, Stanford Univ Press.

EVANS, S. IN PRESS. The skull of lizards and Sphenodon. In C. Gans & A.S. Gaunt (Eds.), Biology of the Reptilia, Vol 20. New York, Academic Press.

FITZSIMONS, V. 1955. The Namib plated-lizard. Afr. Wildlife 9: 21-23.

GUGG, W. 1939. Der Skleralring der plagiotremen Reptilien. Zool. Jahr. 65: 339-416.

HAMILTON, W.J. & C.G. COETZEE. 1969. Thermoregulatory behaviour of the vegetarian lizard Angolosaurus skoogi on the vegetationless northern Namib Desert dunes. Sci. Papers Namib Desert Res. Stat. 47: 95-103.

KAMAL, A.M. 1965. The relation between the auditory capsule and the basal plate, and the commissures between them in Squamata. Zool. Anz. 175: 281-285.

KAMAL, A.M. 1966a. The sphenoid bone in Lacertilia. Anat. Anz. 118: 82-86.

KAMAL, A.M. 1966b. On the hypoglossal foramina in Squamata. Anat. Anz. 118: 91-96.

KAMAL, A.M. 1969. The relation between the glossopharyngeal nerve and the chondrocranium in Squamata. Proc. Zool. Soc. UAR 3: 23-29.

KETCHAM, R.A & W.D. CARLSON. 2001. Acquisition, optimization and interpretation of X-ray tomographic imagery: applications to the geosciences. Comput. Geosci. 27: 381-400.

LAMB, T., A.M. MEEKER, A.M. BAUER & W.R. BRANCH. 2003. On the systematic status of the desert plated lizard (Angolosaurus skoogi): phylogenetic inference from DNA sequence analysis of the African Gerrhosauridae. Biol. J. Linn. Soc. 78: 253-261.

LANG, M. 1991. Generic relationships within Cordyliformes (Reptilia: Squamata). Bull. Inst. R. Sci. Nat. Belg., Biol. 61: 121-188.

LOCHETTO, S. 2002. Phylogenetic analysis of Gerrhosaurus (Reptilia: Squamata: Gerrhosauridae) based on morphology. Unpubl. M.S. Thesis, Villanova Univ., Villanova.

MAISANO, J.A. 2001. A survey of state of ossification in neonatal squamates. Herpetol. Monogr. 15: 135- 157.

MAISANO, J.A. 2002. Terminal fusions of skeletal elements as indicators of maturity in squamates. J. Vert. Paleo. 22: 268-275.

MAISEY, J.G. 2001. CT-scan reveals new cranial features in Devonian chondrichthyan “Cladodus” wildungensis. J. Vert. Paleo. 21: 807-810.

MALAN, M.E. 1941. Cranial anatomy of the genus Gerrhosaurus. S. Afr. J. Sci. 37: 192-217.

MITCHELL, D., M.K. SEELY, C.S. ROBERTS, R.D. PIETRUSZKA, E. MCCLAIN, M. GRIFFIN & R.I. YEATON. 1987. On the biology of the lizard Angolosaurus skoogi in the Namib Desert. Madoqua 15: 201-216.

MOUTON, P. LE F.N. & J.H. VAN WYK. 1997. Adaptive radiation in cordyliform lizards: an overview. Afr. J. Herp. 46: 78-88.

NAGY, K.A., B.C. CLARKE, M.K. SEELY, D. MITCHELL & J.R.B. LIGHTON. 1991. Water and energy balance in Namibian desert sand-dune lizards Angolosaurus skoogi (Andersson, 1916). Funct. Eco. 5: 731-739.

NANCE, H. 2003. The Cranial Osteology of Angolosaurus skoogi (Squamata: Gerrhosauridae) with Comments on the Morphology and Phylogeny of Cordyliformes. Unpubl. M.S. Thesis, Univ. of Texas at Austin, Austin.

OELRICH, T.M. 1956. The anatomy of the head of Ctenosaura pectinata (Iguanidae). Univ. Mich. Mus. Zool. Misc. Publ. 94: 1-122.

PIETRUSZKA, R.D. 1988. Observations on sexual dimorphism and social structure in the lizard Angolosaurus skoogi (Cordylidae) of the northern Namib Desert dunes. S. Afr. J. Zool. 23: 47-51.

PIETRUSZKA, R.D., S.A. HANRAHAN, D. MITCHELL & M.K. SEELY. 1986. Lizard herbivory in a sand dune environment: the diet of Angolosaurus skoogi. Oecologia 70: 587-591.

POLCYN, M.J., J.V. ROGERS, JR., Y. KOBAYASHI & L.L. JACOBS. 2002. Computed tomography of an anolis lizard in Dominican amber: systematic, taphonomic, biogeographic, and evolutionary implications. Palaeo. Electron. 5: 1-13.

RIEPPEL, O. 1999. Variation of cranial characters in Cymatosaurus ‘gracilis’ Schrammen 1899 (Reptilia, Sauropterygia), and its implications for systematics. Paläontol. Z. 73: 369-375.

RIEPPEL, O. & C. CRUMLY. 1997. Paedomorphosis and skull structure in Malagasy chamaeleons (Reptilia: Chamaeleoninae). J. Zool. 243: 351-380.

ROWE, T., J. KAPPELMAN, W.D. CARLSON, R.A. KETCHAM & C. DENISON. 1997. High-resolution computed tomography: a breakthrough technology for earth scientists. Geotimes 42: 23-27.

ROWE, T., C.A. BROCHU & K. KISHI. 1999. Society of Vertebrate Paleontology Memoir 6: Cranial morphology of Alligator mississippiensis and phylogeny of Alligatoroidea. J. Vert. Paleo. 19 (Supp.): 1- 100 with CD-ROM.

SÄVE-SÖDERBERGH, G. 1946. On the fossa hypophyseos and the attachment of the retractor bulbi group in Sphenodon, Varanus, and Lacerta. Arch. Zool. 38A: 1-24.

SÄVE-SÖDERBERGH, G. 1947. Notes on the brain-case in Sphenodon and certain Lacertilia. Zool. Bidrag. Från. Uppsala 25: 489-516.

SEELY, M.K., D. MITCHELL, C.S. ROBERTS & E. MCCLAIN. 1988. Microclimate and activity of the lizard Angolosaurus skoogi on a dune slipface. S. Afr. J. Zool. 23: 92-102.

SIEBENROCK, F. 1892. Zur Kenntniss des Kopfskelettes der Scincoiden, Anguiden und Gerrhosauriden. Ann. K. K. Naturhistorischen Hofmuseums 7: 163-196.

STEYN, W. 1963. Angolosaurus skoogi (Andersson) – a new record from South West Africa. Cimbebasia 6: 8-11.

TYKOSKI, R.S., T.B. ROWE, R.A. KETCHAM & M.W. COLBERT. 2002. Calsoyasuchus valliceps, a new crocodyliform from the early Jurassic Kayenta Formation of Arizona. J. Vert. Paleo. 22: 593-611.

UNDERWOOD, G. 1970. The eye. Pp. 1-98. In C. Gans & T. Parsons (Eds.), The Biology of the Reptilia, Vol 2, Morphology B. New York, Academic Press.

UNDERWOOD, G. 1984. Scleral ossicles in lizards: an exercise in character analysis. Pp. 483-502. In M.W.J. Ferguson (Ed.), Symposia of the Zoological Society of London, Number 52: The Structure, Development and Evolution of Reptiles, A Festschrift in Honour of Professor A. d’A. Bellairs on the Occasion of his Retirement. London, Academic Press.

VAN PLETZEN, R. 1946. The cranial morphology of Cordylus with special reference to the cranial kinesis. Ann. Univ. Stellenbosch 24A: 41-68.

VERSLUYS, J. 1912. Das Streptostylie-Problem und die Bewegungen im Schädel bei Sauropsiden. Zool. Jahr. 2: 545-714.

WEVER, E.G. 1978. The Reptile Ear: Its Structure and Function. Princeton Univ. Press, Princeton.

Links

Gerrhosauridae page on The Reptile Database

Front page image.