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.
About the Species
About this 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.
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.