The Chinese or green water dragon, Physignathus cocincinus, is a large arboreal lizard that inhabits the forests of eastern Thailand, Laos, Vietnam, Malaysia, Cambodia, and southern parts of China. Water dragons live in the immediate vicinity of fresh water. They are aptly named as they are strong swimmers and can remain submerged for 25 minutes or more. Water dragons use their swimming abilities and facultative bipedality to escape predators. Today, Physignathus cocincinus is one of the most popular lizards in the pet trade, which is where this specimen originated.

Physignathus is a member of Agamidae, a lineage of iguanian lizards that also includes the Australian thorny devil, Moloch horridus. Agamidae is the Old World counterpart of the New World iguanids, such as the Mexican spinytail iguana (Ctenosaura pectinata) and the Texas horned lizard (Phrynosoma cornutum). Agamidae includes 12 genera distributed throughout Africa, Asia and Australia. Relationships within Agamidae remain problematic, but an analysis of mitochondrial DNA (Macey et al., 2000) suggests that Physignathus cocincinus is the sister taxon to a clade containing all taxa from Australia and New Guinea. Thus, Physignathus was CT scanned because it appears to be a relatively basal member of Agamidae.

This frozen specimen originated in the pet trade and no locality information is available. It was made available to the University of Texas High-Resolution X-ray CT Facility for scanning by Dr. Jessie Maisano of The University of Texas and Dr. Jacques Gauthier of Yale University. Funding for scanning was provided by an NSF grant (DEB-0132227) to Dr. Jack Sites of Brigham Young University. Funding for image processing was provided 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.

Lateral view of the scanned specimen.

The specimen was scanned by Richard Ketcham on 28 March 2003 along the coronal axis for a total of 690 slices. Each slice is 0.0546 mm thick, with an interslice spacing of 0.0546 mm and a field of reconstruction of 24 mm.

Literature

Barbour, T. 1912. Physignathus cocincinus and its subspecies. Proceedings of the Biological Society of Washington 25:191-192.

Frost, D. R., R. Etheridge, J. Daniel, and T. A. Titus. 2001. Total evidence, sequence alignment, evolution of polychrotid lizards, and a reclassification of the Iguania (Squamata: Iguania). American Museum Novitates 3343:1-38.

M., O. Hidetoshi, K. Mari, N. Jarujin, Y. Hoi-Sen, S. Showichi, and H. Tsutomu. 2000. Phylogenetic relationships of the family Agamidae (Reptilia: Iguania) inferred from mitochondrial DNA sequences. Zoological Science (Tokyo) 17:527-537.

Macey, J. R., J. A. Schulte, II, A. Larson, N. B. Ananjeva, Y. Wang, R. Pethiyagoda, N. Rastegar-Pouyani, and T. J. Papenfuss. 2000. Evaluating trans-tethys migration: an example using acrodont lizard phylogenetics. Systematic Biology 49:233-256.

Mader, D. R. 1994. Chinese water dragons (Physignathus cocincinus). Reptiles 2:48-61.

Three-dimensional volumetric renderings of the skull with the scleral ossicles, hyoid and jaw removed, and of the isolated left mandible. All are 2mb or less.

Skull pitch movie	Skull roll movie
Mandible yaw movie	Mandible pitch movie	Mandible roll movie