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Phrynosoma ditmarsi STEJNEGER, 1906

IUCN Red List - Phrynosoma ditmarsi - Data Deficient, DD

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Higher TaxaPhrynosomatidae, Phrynosomatinae, Phrynosomatini; Iguania, Sauria, Squamata (lizards)
Common NamesE: Rock Horned Lizard
S: Camaleón de Roca 
SynonymPhrynosoma ditmarsi STEJNEGER 1906
Phrynosoma ditmarsi — SMITH & TAYLOR 1950: 104
Phrynosoma ditmarsi — LINER 1994
Phrynosoma ditmarsi — PIANKA & VITT 2003: 161
Phrynosoma hernandesi ditmarsi — KÖHLER 2021 
DistributionMexico (Sonora)

Type locality: State of Sonora, not far from the boundary of Arizona.  
Reproductionovovivparous (Lambert & Wiens 2013). 
TypesHolotype: USNM 36022 
DiagnosisDefinition. Phrynosoma ditmarsi is a moderately sized (76-90 mm SVL) viviparous horned lizard with a red, brown, gray, or yellow dorsal ground color and dark crossbands posteriorly. The venter is whitish, with strongly keeled scales. These lizards have a single row of lateral abdominal fringe scales which are bluntly pyramidal. The tail is short. The head is wider than long with a high postorbital ridge extending from the tip of the orbital boss to the outer enlarged temporals. A postocular boss is present as a broad pyramid in which three edges are formed by the continuation of the superciliary, supraocular, and orbitotemporal ridges. Occipital and temporal horns are reduced to rounded, flaring expansions on either side of the head, which has a deep and narrow occipital notch. The nares are in the line of the canthus rostralis. Postlabials are slightly enlarged, convex, and triangular; the keeled edge of the row is directed nearly horizontally. Mandibles are greatly expanded posteriorly, exceeding the diameter of the orbit. Five to eight rugose sublabials separate chinshields from infralabials, which increase in size and are keeled posteriorly. Gular scales are small and keeled. The tympanum is bare and resides in the anterior neck fold posterior to a vertical row of four small spines. Posterior and dorsal surfaces of the hind legs and tail have large, scattered, bluntly keeled scales, the larger scale bases surrounded by rosettes of smaller scales. Males have enlarged postanal scales (Hodges 1995).

Diagnosis: Phrynosoma dirmarsi can be distinguished from all congeners by the combination of reduced occipital and temporal horns appearing as rounded, flaring expansions on either side of the head, a deep and narrow occipital notch, large vertical expansion of the mandibles, a high postorbital ridge, a single row of abdominal fringe scales, nares in the line of the canthus rostralis, and a bare tympanum in the anterior neck fold posterior to a vertical row of four spines (Hodges 1995). 
CommentHabitat: montane

Group: Belongs to the Tapaja clade fide LEACHE & MCGUIRE 2006.

Diet: With 11% of its diet being ants this species seems to be the least dependent and specialized on ants (Fabian 2014). 
EtymologyNamed after Dr. Raymond Lee Ditmars (1876-1942), Curator of Reptiles at the Bronx Zoo, New York (1899-). Ditmars also worked in the Department of Entomology at the American Museum of Natural History (1893-1897) and as a reporter for the New York Times (1898). 
  • Aguilar-Morales, Cecilia and Thomas R. Van Devender 2018. Horned Lizards (Phrynosoma) of Sonora, Mexico: Distribution and Ecology. Sonoran Herpetologist 31 (3): 40-50 - get paper here
  • Baur, B. 1986. Die Felsen-Krötenechse. Herpetofauna 8 (40): 27 - get paper here
  • Beolens, Bo; Michael Watkins, and Michael Grayson 2011. The Eponym Dictionary of Reptiles. Johns Hopkins University Press, Baltimore, USA - get paper here
  • Burkhardt, Timothy R. and Scott Trageser. 2015. Geographic Distribution: Phrynosoma ditmarsi (rock horned lizard). Herpetological Review 46 (1): 60 - get paper here
  • Enderson, Erik F.; Thomas R. Van Devender, Robert L. Bezy 2014. Amphibians and reptiles of Yécora, Sonora and the Madrean Tropical Zone of the Sierra Madre Occidental in northwestern Mexico. Check List 10 (4): 913-926 - get paper here
  • Fabian, B. F 2014. Überlegungen zur Ernährung von Krötenechsen. Reptilia (Münster) 19 (107): 24-29
  • Hodges W L. 1995. Phrynosoma ditmarsi. Catalogue of American Amphibians and Reptiles (614): 1-3. - get paper here
  • Jones, L.L. & Lovich, R.E. 2009. Lizards of the American Southwest. A photographic field guide. Rio Nuevo Publishers, Tucson, AZ, 568 pp. [review in Reptilia 86: 84] - get paper here
  • Lambert, Shea M. and John J. Wiens 2013. EVOLUTION OF VIVIPARITY: A PHYLOGENETIC TEST OF THE COLD-CLIMATE HYPOTHESIS IN PHRYNOSOMATID LIZARDS. Evolution 67 (9): 2614–2630 - get paper here
  • Leaché, Adam D. and Jimmy A. McGuire 2006. Phylogenetic relationships of horned lizards (Phrynosoma ) based on nuclear and mitochondrial data: Evidence for a misleading mitochondrial gene tree. Molecular Phylogenetics and Evolution 39 (3): 628-644 - get paper here
  • Lemos-Espinal JA, Smith GR, Rorabaugh JC 2019. A conservation checklist of the amphibians and reptiles of Sonora, Mexico, with updated species lists. ZooKeys 829: 131-160 - get paper here
  • Lowe, Charles H., Jr;Robinson, Michael D.;Roth, Vincent D. 1971. A population of Phrynosoma ditmarsi from Sonora, Mexico. Journal of the Arizona Academy of Science 6 (4): 275-277 - get paper here
  • Meyers, J.J.; Herrel, A. & Nishikawa, K. 2006. Morphological correlates of ant eating in horned lizards (Phrynosoma). Biological Journal of the Linnean Society 89: 13–24 - get paper here
  • Molina-Padilla, G; Van Devender, T R & Salazar-Martínez, J A; 2019. Geographic Distribution: Phrynosoma ditmarsi (Rock Horned Lizard) Mexico: Sonora: Municipality of Bacoachi. Herpetological Review 50 (3): 527 - get paper here
  • Pianka, E.R. & Vitt, L.J. 2003. Lizards - Windows to the Evolution of Diversity. University of California Press, Berkeley, 347 pp. [review in Copeia 2004: 955] - get paper here
  • Presch,W. 1969. Evolutionary osteology and relationships of the horned lizard genus Phrynosoma (family Iguanidae). Copeia 1969 (2): 250-275 - get paper here
  • Reeder,T.W. & Montanucci,R.R. 2001. Phylogenetic analysis of the horned lizards (Phrynomomatidae: Phrynosoma): evidence from mitochondrial DNA and morphology. Copeia 2001 (2): 309-323 - get paper here
  • Roth, V.D. 1997. Ditmars' Horned Lizard (Phrynosoma ditmarsi) or the case of the lost lizard. Sonoran Herpetologist 10 (1):2-6. - get paper here
  • Sherbrooke, Wade C. 2003. Introduction to Horned Lizards of North America. University of California Press, Berkeley, 178 pp. - get paper here
  • Sherbrooke, Wade C.;Martin, Brent E.;Lowe, Charles H. 1998. Geographic Distribution. Phrynosoma ditmarsi. Herpetological Review 29 (2): 110-111 - get paper here
  • Stejneger, Leonhard 1906. A new lizard of the genus Phrynosoma, from Mexico. Proc. US Natl. Mus. 29 (1437): 565-567 - get paper here
  • Turner, D. S., T. R. Van Devender, H. Silva-Kurumiya, N. León Del Castillo, C. Hedgcock, C. Roll, M. Wilson, and F. I. Ochoa-Gutierrez. 2017. Distribution of Phrynosoma ditmarsi Stejneger, 1906, with notes on habitat and morphology. 2017. Mesoamerican Herpetology 4(4): 979–985 - get paper here
  • Turner, D. S., Van Devender, T. R., Hale, S. F., Zach, R., Martínez, R., Van Devender, R. W., ... & Paholski, C. 2022. Amphibians and reptiles of Rancho Las Playitas area, Sonora, Mexico. Sonoran Herpetologist, 35, 50-59 - get paper here
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