THE CENTER FOR NORTH AMERICAN HERPETOLOGY

Reptilia    Squamata (part-other lizards)    Phrynosomatidae  

Flat-tailed Horned Lizard
Phrynosoma mcallii (Hallowell, 1852)
FRY-noh-SOH-mah — mak-AL-ee-eye

SSAR 9th Edition Comments:
 Gottscho et al. (2024, Molecular Ecology 33: e17308) found subdivision of P. mcalli into genetic clusters on either side of the Colorado River as well as further subdivision of the northwestern cluster by the Salton Sea; however, they considered the differentiation of these clusters insufficient to warrant their recognition as species or subspecies. (de Queiroz, Kevin and Lauren M. Chan. 2025. Squamata (excluding snakes) – Lizards. Pages 23-37 in Kirsten E. Nicholson (Editor), Scientific and Standard English Names of Amphibians and Reptiles of North America North of Mexico, with Comments Regarding Confidence in Our Understanding, 9th Edition. Society for the Study of Amphibians and Reptiles, Lawrence, Kansas. 87 pp.)

Range maps are based on curated specimens and provided gratis by CNAH.
(Created by Travis W. Taggart; Version: 2023.04.10.08.04.18)
Download GeoJSON polygon range file: - 1 MB

Province/State Distribution:
United States: Arizona California

Taxonomic Etymology:
Named in honor of a 19th-century army surgeon and naturalist.
Phrynosoma — From Greek phrynos (φρῦνος), meaning “toad,” and sōma (σῶμα), meaning “body,” referring to the toad-like, squat appearance of these lizards.
mcallii — A patronym honoring George Archibald McCall (1802–1868), a U.S. Army officer and naturalist who explored the American Southwest.

First instance(s) of published English names:
McCall's Horned Toad (Doliosaurus mccallii: Cooper, James G. 1869. The fauna of California and its geographical distribution. Proceedings of the California Academy of Sciences 4():61-81); MacCall's Horned Lizard (Phrynosoma maccallii: Yarrow, Henry C. 1876. List of Skeletons and Crania in the Section of Comparative Anatomy of the United States Army Medical Museum for use during the International Exhibition of 1876 in Connection with the Representation of the Medical Department U.S. Army. Army Medical Museum, Washington, D. C. pp.); McCall's Horned Lizard (Phrynosoma maccalli: Yarrow, Henry C. 1882. Check list of North American Reptilia and Batrachia with catalogue of specimens in U. S. National Museum. Bulletin of the United States National Museum (24):1-249); Flat-tailed Horned Toad (Phrynosoma m'callii: Van Denburgh, John. 1897. The reptiles of the Pacific Coast and Great Basin: An account of the species known to inhabit California, and Oregon, Washington, Idaho, and Nevada. Occasional Papers of the California Academy of Sciences 5():9-236); Flat-tailed Horned Toad (Phrynosoma m'calli: Schmidt, Karl P. 1953. A Check List of North American Amphibians and Reptiles. 6th Edition. University of Chicago Press, Chicago, Illinois. 280pp.);

Taxon Links:

  
Catalog of American Amphibians and Reptiles
  
The Reptile Database
  
NatureServe
  
iNaturalist
  
GenBank
  
USGS - Nonindigenous Aquatic Species Database

Selected References:
1852 Hallowell, Edward. Descriptions of new species of reptiles inhabiting North America. Proceedings of the Academy of Natural Sciences, Philadelphia 6:177-182
1932 Klauber, Laurence M. The flat-tailed horned toad in Lower California. Copeia 1932(2):100
1963 Lynn, R. T. Comparative behavior of the horned lizards, genus Phrynosoma, of the United States. Dissertation. University of Oklahoma, Norman, Oklahoma. 76pp.
1965 Lynn, R. T. A comparative study of the display behavior in Phrynosoma (Iguanidae). Southwestern Naturalist 10(1):25-30
1981 Funk, Richard S. Phrynosoma mcallii. Catalogue of American Amphibians and Reptiles (281):1-2
1982 Turner, Frederick B. and P. A. Medica. The distribution and abundance of the flat-tailed horned lizard (Phrynosoma mcallii). Copeia 1982(4):815-823
1987 Montanucci, Richard R. A phylogenetic study of the horned lizards, genus Phrynosoma, based on skeletal and external morphology. Natural History Museum of Los Angeles County, Contributions in Science (390):1-36
1993 Wiens, John J. Phylogenetic relationships of phrynosomatid lizards and monophyly of the Sceloporus group. Copeia 1993(2):287-299
1996 Montanucci, Richard R. Morphological variation in the gular fold in the horned lizard genus Phrynosoma (Iguania: Phrynosomatidae). Herpetologica 52(1):46-55
2001 Reeder, Tod W., and Richard R. Montanucci. Phylogenetic analysis of the horned lizards (Phrynosomatidae: Phrynosoma): Evidence from mitochondrial DNA and morphology. Copeia 2001(2):309-323
2004 Hodges, Wendy L. Evolution of viviparity in horned lizards (Phrynosoma): Testing the cold-climate hypothesis. Journal of Evolutionary Biology 17:1230–1237
2017 Bezy, Robert L., Philip C. Rosen, Thomas R. Van Devender, and Erik F. Enderson. Southern distributional limits of the Sonoran Desert herpetofauna along the mainland coast of northwestern Mexico Mesoamerican Herpetology 4(1):138-167
2024 Pillod, David S., Michelle I. Jeffries, Robert S. Arkle, and Deanna H. Olson. Climate futures for lizards and snakes in western North America may result in new species management issues Ecology and Evolution 14(10):1-23

THE CENTER FOR NORTH AMERICAN HERPETOLOGY — Accessed: Friday 05 December 2025 15:54 CT