Tracheloptychus petersi, the Malagasy plated lizard, occurs in southwestern Madagascar where it inhabits riverbanks of tropical forests. It is a heat-loving lizard, living where temperatures are often up to 40 deg C, even in the shade, during the hottest part of the year. T. petersi is becoming increasingly popular in the pet trade, which is where this specimen originated.

Tracheloptychus is a member of Scleroglossa (see also Varanus, Lanthanotus), one of the two major squamate clades (the other being Iguania, e.g., Ctenosaura, Phrynosoma). Within Scleroglossa, Tracheloptychus resides in Gerrhosauridae (see also Gerrhosaurus major and G. nigrolineatus), the hypothesized sister taxon to Cordylidae. Gerrhosauridae is diagnosed, in part, by the following (from Lang, 1991): nasal and prefrontal bones in broad contact; palatine and jugal bones in contact or overlap at the infraorbital foramen; postfrontal not forked medially; supratemporal fenestra entirely closed by postfrontal and squamosal; median posterior processes of parietal bone deeply forked bracing the supraoccipital ridge; skull darkly pigmented; and pterygoid teeth present. Tracheloptychus is the only gerrhosaurid to have sharply keeled scales.

The cranial osteoderms in gerrhosaurids have long hampered the study of their cranial bones, and it is difficult to remove the osteoderms that actually coossify with the dorsal cranial bones without damaging the skull. CT scanning makes it possible to digitally erase the osteoderms and render the skull without them. Animations of Tracheloptychus petersi with the osteoderms digitally removed, making it easier to see the features discussed above, can be found in 'Additional Imagery'.

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 and image processing was provided by an NSF grant (DEB-0132227) to Dr. Jack Sites of Brigham Young University.

The specimen was scanned by Matthew Colbert on 18 July 2002 along the coronal axis for a total of 420 slices, each slice 0.0514 mm thick with an interslice spacing of 0.0514 mm.

Literature
Cordyliformes Bibliographie, containing over 1100 citations on cordylids and gerrhosaurids

Brygoo, E. R. 1985. Les Gerrhosaurinae de Madagascar Sauria (Cordylidae). Mémoires du Muséum National d'Histoire Naturelle, Série A, Zoologie 134 1-65.

Estes, R. 1983. Sauria terrestria, Amphisbaenia. Handbuch der Paläoherpetologie, Part 10A. Gustav Fischer Verlag, Stuttgart, 249 pp.

Lang, M. 1991. Generic relationships within Cordyliformes (Reptilia: Squamata). Bulletin de L'Institut Royal des Sciences Naturelles de Belgique, Biologie 61:121-188.

Rogner, M. 1994. Echsen 2: Warane, Skinke und andere Echsen sowie Brückenechsen und Krokodile. Stuttgart: Eugen Ulmer Verlag, 270 S.

Links
Tracheloptychus petersi care sheet from N. Tenny

plated lizard page from the Cyberlizard

Three-dimensional volumetric renderings of the skull with the osteoderms digitally removed. The 'scratched' sections indicate where the osteoderms contact the skull. All are 2-3mb.

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