Roadless Areas
Home/Species/ Round-tailed Horned Lizard

Phrynosoma modestum

Girard in Baird and Girard, 1852

Round-tailed Horned Lizard

G5Secure Found in 7 roadless areas NatureServe Explorer →
G5SecureGlobal Rank
Least concernIUCN
LowThreat Impact
Identity
Unique IDELEMENT_GLOBAL.2.104144
Element CodeARACF12050
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryVertebrate Animal
IUCNLeast concern
Endemicoccurs (regularly, as a native taxon) in multiple nations
KingdomAnimalia
PhylumCraniata
ClassReptilia
OrderSquamata
FamilyPhrynosomatidae
GenusPhrynosoma
Other Common Names
round-tailed horned lizard (EN) Roundtail Horned Lizard (EN)
Concept Reference
Reeve, W. L. 1952. Taxonomy and distribution of the horned lizards genus Phrynosoma. University of Kansas Science Bulletin 34:817-960.
Taxonomic Comments
.
Conservation Status
Review Date2005-07-13
Change Date1996-10-28
Edition Date2005-07-13
Edition AuthorsHammerson, G.
Threat ImpactLow
Range Extent200,000-2,500,000 square km (about 80,000-1,000,000 square miles)
Number of Occurrences81 to >300
Range Extent Comments
The range extends from southeastern Arizona, New Mexico (Degenhardt et al. 1996), southeastern Colorado (Hammerson 1999, Rondeau 2002), and northern Texas (Bartlett and Bartlett 1999, Dixon 2000) south to San Luis Potosi, Mexico (Stebbins 2003). Elevational range extends from 210 to 2,200 meters (700-7,220 feet) (Degenhardt et al. 1996, Stebbins 2003).
Occurrences Comments
This species is represented by hundreds of collection sites (Degenhardt et al. 1996, Whiting and Dixon 1996).
Threat Impact Comments
No major threats have been identified. Locally, populations have been reduced or eliminated as a result of urbanization or agricultural development.
Ecology & Habitat

Habitat

This lizard occupies various desert grassland and desert shrubland habitats, generally areas of sparse scrub vegetation and gravelly to rocky soils, such as bajada slopes, edges of washes, desert flats, arid and semiarid hills (Degenhardt et al. 1996, Bartlett and Bartlett 1999, Stebbins 2003). When not active or resting on the ground surface, it burrows into the soil or occupies rodent burrows. Eggs are laid in soil/underground.

Ecology

Research in southern Arizona indicates that single-season home range size is quite variable and averages a little more than 0.1 ha in females and about 0.4 ha in males (Munger 1984). Home range length extends up to about 205 m but generally is less than 100 m.

Reproduction

Lays clutch of 9-18 eggs, June-July. Eggs hatch July-August (Stebbins 1985, Behler and King 1979).
Terrestrial Habitats
Shrubland/chaparralGrassland/herbaceousDesert
Other Nations (1)
United StatesN5
ProvinceRankNative
ColoradoS1Yes
ArizonaS3Yes
OklahomaS1Yes
New MexicoS5Yes
TexasS4Yes
Roadless Areas (7)
Arizona (2)
AreaForestAcres
ChiricahuaCoronado National Forest76,876
PinalenoCoronado National Forest130,920
New Mexico (5)
AreaForestAcres
Contiguous To Black & Aldo Leopold WildernessGila National Forest111,883
Little Dog And Pup CanyonsLincoln National Forest25,412
Ortega PeakLincoln National Forest11,545
South Guadalupe MountainsLincoln National Forest20,930
West Face Sacramento MountainsLincoln National Forest41,176
References (19)
  1. Bartlett, R. D., and P. P. Bartlett. 1999a. A field guide to Texas reptiles & amphibians. Gulf Publishing Company, Houston, Texas. xviii + 331 pp.
  2. Behler, J. L., and F. W. King. 1979. The Audubon Society field guide to North American reptiles and amphibians. Alfred A. Knopf, New York. 719 pp.
  3. Collins, J. T. 1990. Standard common and current scientific names for North American amphibians and reptiles. 3rd ed. Society for the Study of Amphibians and Reptiles. Herpetological Circular No. 19. 41 pp.
  4. Conant, R., and J. T. Collins. 1998. A field guide to reptiles and amphibians: eastern and central North America. Third edition, expanded. Houghton Mifflin Co., Boston, Massachusetts. 616 pp.
  5. Crother, B. I. (editor). 2008. Scientific and standard English names of amphibians and reptiles of North America north of Mexico, with comments regarding confidence in our understanding. Sixth edition. Society for the Study of Amphibians and Reptiles Herpetological Circular 37:1-84. Online with updates at: http://www.ssarherps.org/pages/comm_names/Index.php
  6. Crother, B. I. (editor). 2012. Scientific and standard English names of amphibians and reptiles of North America north of Mexico, with comments regarding confidence in our understanding. 7th edition. SSAR Herpetological Circular 39:1-92.
  7. Crother, B. I. (editor). 2017. Scientific and standard English names of amphibians and reptiles of North America north of Mexico, with comments regarding confidence in our understanding. 8th edition. SSAR Herpetological Circular 43:1-104. [Updates in SSAR North American Species Names Database at: https://ssarherps.org/cndb]
  8. Degenhardt, W. G., C. W. Painter, and A. H. Price. 1996. Amphibians and reptiles of New Mexico. University of New Mexico Press, Albuquerque. xix + 431 pp.
  9. Dixon, J. R. 2000. Amphibians and reptiles of Texas. Second edition. Texas A & M University Press, College Station. 421 pp.
  10. Hammerson, G. A. 1999. Amphibians and reptiles in Colorado. Second edition. University Press of Colorado, Boulder. xxvi + 484 pp.
  11. Leaché, A.D., and C.W. Linkem. 2015. Phylogenomics of horned lizards (Genus: <i>Phrynosoma</i>) using targeted sequence capture data. Copeia 103(3):586-594.
  12. Munger, J. C. 1984. Home ranges of horned lizards (Phrynosoma): circumscribed and exclusive? Oecologia 62:351-360.
  13. Nicholson, K. E. (ed.). 2025. Scientific and Standard English Names of Amphibians and Reptiles of North America North of Mexico, with Comments Regarding Confidence in Our Understanding. Ninth Edition. Society for the Study of Amphibians and Reptiles. 87pp. Online database available at: https://cnah.org/SSARnames.aspx
  14. Reeder, T. W., and R. R. Montanucci. 2001. Phylogenetic analysis of the horned lizards (Phrynosomatidae: <i>Phrynosoma</i>): evidence from mitochondrial DNA and morphology. Copeia 2001:309-323.
  15. Reeve, W. L. 1952. Taxonomy and distribution of the horned lizards genus <i>Phrynosoma</i>. University of Kansas Science Bulletin 34:817-960.
  16. Rondeau, R. 2002. Geographic distribution: Phrynosoma modestum. Herpetological Review 33:226.
  17. Stebbins, R. C. 1985a. A field guide to western reptiles and amphibians. Second edition. Houghton Mifflin Company, Boston, Massachusetts. xiv + 336 pp.
  18. Stebbins, R. C. 2003. A field guide to western reptiles and amphibians. Third edition. Houghton Mifflin Company, Boston.
  19. Whiting, M. J., and J. R. Dixon. 1996. <i>Phrynosoma modestum</i>. Catalogue of American Amphibians and Reptiles 630:1-6.