Phrynosoma modestum, the round-tailed horned lizard, ranges from the western half of Texas north to Albuquerque, New Mexico, west to southeastern Arizona, south through northeastern Sonora, most of Chihuahua, through the northern third of Durango, to northern Zacatecas and northeastern Nuevo Leon, Mexico. P. modestum can be dinstinguished from other horned lizard species by the following: tail round in cross-section; no lateral abdominal fringe scales; four occipital horns short and equal in length; ear concealed in some, exposed in other; chin shields contact infralabials throughout; solid, pale coloration, white, tan or pink; dorsal marks restricted to dark neck patches, dark tail bands, some shadowing around limbs; and unique rock mimicry behavior.
About the Species
This specimen (TNHC 48520) was collected by Dr. Wendy Hodges on the foothills of Glass Mountain, 30.6 km north of Marathon, Brewster County, Texas. It was made available to the University of Texas High-Resolution X-ray CT Facility for scanning by Dr. Hodges of the Department of Biology, University of California, Riverside. Funding for scanning was provided by a National Science Foundation grant (DBI-0204459) to Dr. Hodges. Funding for image processing was provided by a National Science Foundation Digital Libraries Initiative grant to Dr. Timothy Rowe of the Department of Geological Sciences, The University of Texas at Austin.
About this Specimen
The specimen was scanned by Matthew Colbert on 28 May 2003 along the coronal axis for a total of 594 slices, each slice 0.0243 mm thick with an interslice spacing of 0.0243 mm.
Frost, D. R., and R. Etheridge. 1989. A phylogenetic analysis and taxonomy of iguanian lizards (Reptilia: Squamata). University of Kansas Museum of Natural History Miscellaneous Publication 81.
Pianka, E. R., and W. S. Parker. 1975. Ecology of horned lizards: A review with special reference to Phrynosoma platyrhinos Copeia 1975:141-162.
Presch, W. 1969. Evolutionary osteology and relationships of the horned lizard genus Phrynosoma (Family Iguanidae) Copeia 1969:250-275.
Reeve, W. L. 1952. Taxonomy and distribution of the horned lizard genus Phrynosoma. University of Kansas Science Bulletin 34:817-960.
Smith, H. M. 1946. Handbook of Lizards: Lizards of the United States and of Canada. Comstock Publishing Co., Ithaca, New York.
More on horned lizards from Eric Pianka and Wendy Hodges
Phrynosoma modestum page on the Texas Memorial Museum's Herps of Texas
The Horned Lizard Conservation Society