Goode’s Horned Lizard (Phrynosoma goodei)

Goode's Horned Lizard, Mohawk Dunes, AZ. Photo by Jim Rorabaugh

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Goode’s Horned Lizard (Phrynosoma goodei) was described by Leonhard Stejneger in 1893, but because of its close resemblance to the Desert Horned Lizard (P. platyrhinos), Klauber (1935) designated it a subspecies of P. platyrhinos. Using mitochondrial DNA, Mulcahy et al. (2006) discovered significant divergence among P. platyrhinos” populations north and south of the Gila River, and east and west of the Colorado River, and elevated goodei to species.  They also found that Desert Horned Lizards north of the Gila River in Arizona differed significantly from those in California, but Arizona samples were too few in number to warrant assigning a new name to those populations.

Goode’s Horned Lizard is of moderate size (< 90 mm SVL), it has three temporal horns on each side of the head, and two elongated occipital horns between them that point upward and to the rear.  One or two rows of enlarged fringed scales are found at the margin between the dorsum and venter on the body (in the second row, if present, the fringed scales are relatively small and the row is often incomplete; this second row is below the primary row). The tympanum is completely covered by scales. The dorsal ground color, which often matches the local substrate, ranges from gray to orange, and usually two longitudinal rows of paired dark spots are present on each side of the mid-dorsal line (may be faint or diffuse), often overlain with wavy dark crossbands. The dorsal aspect of the tail is banded, and most lizards show dark shoulder patches. In a few specimens, a diffuse mid-dorsal stripe, not highly contrasting with the rest of the dorsal pattern can be discerned (see image gallery). Some individuals are nearly patternless. The venter is immaculate white or cream with or without small black spots.  Spots may be limited to the chin and chest.  In the Yuma Desert, specimens higher on the bajada are more likely to have spotted venters.

Goode’s Horned Lizard is most similar to the Desert Horned Lizard, which occurs north of the Gila River in western Arizona, elsewhere in a number of the western United States, and northeastern Baja California. The latter species has one row of fringed scales at the margin of the abdomen, the occipital horns are oriented more to the rear rather than upwards, the dorsum of the body has wavy dark crossbands, the tympanum is usually not covered by scales, and the venter is speckled with black spots.  But character overlap is common with P. platyrhinos and P. goodei specimens, and individual lizards may defy assignment to species based on morphology and coloration alone. Geography is currently the best way to distinguish between these two horned lizards.

Goode’s Horned Lizard occurs south of the Gila River from the eastern Yuma Desert eastward to Casa Grande, the vicinity of Coolidge, and the Avra Valley, and southward into Sonora through the Gran Desierto de Altar and the Pinacate Region to Punta Sargento, Sonora. It may occur in northeastern Baja California, as well. It is a species of valleys and bajadas primarily within the Colorado River subdivision of Sonoran desertscrub, although it occurs sparingly into the Arizona Upland subdivision in the eastern portions of its range (e.g. Waterman Mountains) and into the Central Gulf Coast subdivision of Sonoran desertscrub in the southern end of its distribution. Substrates where it is found are often fine to gravelly sands. It is common on the edges of the Mohawk Dunes and dunes at Pinta Sands in Yuma County, but is not likely to be found in the larger dunes of the Gran Desierto and the Yuma Desert. The species ranges from near sea level on the coast of Sonora to 700 m in the Waterman Mountains. In the 100-Mile Circle, it is usually found from 400 to 700 m elevation.

Goode’s Horned Lizard is diurnal and active from February into November, although most lizards observed after late August are hatchlings. During the heat of summer, the species’ activity is bimodal, mornings and evenings. Sexual maturity is attained at about 65 mm SVL. Males are distinguished from females by enlarged postanal scales, prominent femoral pores, and a wider tail base. Females grow to a larger size than males. Mating occurs in the spring, and possibly into July, and clutches of 2-10 (mean = 5.6) eggs are laid from April into early August. One or two clutches are produced per year. Hatchlings resemble small adults and are 20-30 mm SVL. The diet is primarily harvester ants, however other insects are taken as well.  Although it eats ants, Goode’s Horned Lizards do not appear to spend a lot of time in the vicinity of ant nests. This species is not known to squirt blood from its eyes.

In the Yuma Desert and the western Gran Desierto de Altar, Goode’s Horned Lizard occasionally hybridizes with the Flat-tailed Horned Lizard (Phrynosoma mcallii), resulting in lizards with confusing mixes of morphological characters. Goode’s Horned Lizard is morphologically and ecologically intermediate between the Flat-tailed Horned Lizard and the Desert Horned Lizard.  All three are closely related, and Goode’s Horned Lizard may have arisen through hybridization between the other two.

Suggested Reading:

Brennan, T.C., and A.T. Holycross. 2006. Amphibians and Reptiles in Arizona. Arizona Game and Fish Department, Phoenix, AZ.

Howard, C.W.  1974.  Comparative reproductive ecology of horned lizards (Genus Phrynosoma) in southwestern United States and northern Mexico.  Journal of the Arizona Academy of Sciences 9:108-116.

Lara-Resendiz, R.A., T. Jezkova, P.C. Rosen, and F.R. Méndez-de la Cruz. 2014. Thermoregulation during the summer season in the Goode’s horned lizard Phrynosoma goodei (Iguania: Phrynosomatidae) in Sonoran Desert. Amphibia-Reptilia 35(2):161-172.

Mulcahy, D.G. 2009. Goode’s Horned Lizard Phrynosoma goodei Stejneger, 1893. Pages 174-177 in Jones, L.L.C., and R.E. Lovich (eds.), Lizards of the American Southwest: A Photographic Field Guide.  Rio Nuevo Publishers, Tucson, Arizona.

Mulcahy, D.G., A.W. Spaulding, J.R. Mendelson III, and E.D. Brodie Jr. 2006. Phylogeography of the flat-tailed horned lizard (Phrynosoma mcallii) and systematics of the P. mcallii-platyrhinos mtDNA complex. Molecular Ecology 15(7):1807-1826.

Pianka, E.R., and W.S. Parker. 1975. Ecology of horned lizards: A review with special reference to Phyrnosoma platyrhinos. Copeia 1975 (1):141-162.

Sherbrooke, W.C. 2003. Introduction to Horned Lizards of North America. University of California Press, Berkeley, CA.

Author: Jim Rorabaugh

For additional information on this species, please see the following volume and pages in the Sonoran Herpetologist: 2005 May:54-55.


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