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Phrynosoma diminutum MONTANUCCI, 2015

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Higher TaxaPhrynosomatidae, Phrynosomatinae, Phrynosomatini; Iguania, Sauria, Squamata (lizards) 
Common NamesSan Luis Valley Short-horned Lizard 
SynonymPhrynosoma diminutum MONTANUCCI 2015
Phrynosoma douglassi — GENTRY 1885: 140 (part)
Phrynosoma douglassii hernandesi — COPE 1900: 413 (part)
Phrynosoma douglassii ornatissimum — VAN DENBURGH 1922: 377(part)
Phrynosoma douglassii ornatissimum — SMITH 1946: 305 (part)
Phrynosoma douglassii ornatissimum — REEVE 1952: 927 (part)
Phrynosoma hernandezi — ZAMUDIO et al. 1997: 302 (part) 
DistributionUSA (Colorado, probably N New Mexico)

Type locality: Medano Road, just outside Medano Ranch, Alamosa County, Colorado.  
TypesHolotype. UCM 61895, adult female, collected from Medano Road, just outside The Nature Conservancy’s Medano Ranch, 2,308 m., Alamosa County, Colorado, by A. Schneider and A. Mitchell on 4 August 2006 (Fig. 14).
Paratypes. LSUMZ 13834–37, 13839–40, MEL 1013, 1015, 1016, MVZ 27042, UCM 3894, 3898, 48465– 66, 51268, 61896, UMMZ 62242, 62244, 62247–52, 62255–58, 62261–64, USNM 8558, 44888, 44890. See Appendix I for locality data. 
CommentDistribution: see map 9 in Montanucci 2015: 169.

Diagnosis. Phrynosoma diminutum sp. nov. can be distinguished from other members of the P. douglasii species complex by the following combination of adult characters: (1) snout short, 45% ± 1.87 (38.8–50%) of orbit to rostral scale distance; (2) rostrofrontal profile rounded or angular with a steep incline; (3) frontal rim not elevated, or only slightly elevated above the occipital shelf; (4) enlarged frontal rim scales 1.63 ± 0.23 (0–3) / 1.60 ± 0.22 (0–3); (5) temporal shelf short, 10.1% ± 0.95 (7.1–13.0%) in males, 11.7% ± 0.99 (6.2–15.8%) in females; (6) temporal shelf weakly to strongly convex; (7) cephalic horns short, third temporal horn length 10.4% ± 0.57 (6.7–13.5%); (8) cephalic horns slightly elevated to nearly vertical; (9) tympanum elliptic, moderately broad; (10) tympanum exposed; (11) tail moderately short, 215% ± 11.04 (180–239%) in males, 179% ± 4.94 (159–209%) in females; (12) dorsal spots small, wedge-shaped to slightly rounded; (13) light-colored borders of dorsal spots confined to posterior edges; (14) dorsolateral white spots absent, but white dots, flecks, and vermiculations may be present; (15) gular area with scattered melanistic spots and/or vermiculations (melanin-dispersed phase); (16) abdomen with large melanistic spots or extensive dark suffusion (melanin-dispersed phase); (17) melanistic subcaudal bands absent or interrupted bands present distally (melanin-dispersed phase).

Comparisons. P. diminutum sp. nov. differs discretely from P. brevirostris in having irregular rows of large, melanistic spots or extensive dark suffusion on the abdomen and widely interrupted subcaudal bands (as paired spots) during the melanin-dispersed phase. P. diminutum sp. nov. is further differentiated from P. brevirostris and from P. bauri sp. nov. in having a shorter, more convex temporal shelf and a relatively short tail. In P. diminutum sp. nov. and P. brevirostris the frontal rim is not elevated or only slightly elevated above the occipital shelf, but in P. bauri sp. nov. the frontal rim is usually well defined and elevated above the occipital shelf. P. diminutum sp. nov. also has a significantly lower number of enlarged frontal rim scales and a shorter third temporal horn than P. bauri sp. nov. (Table 3). P. diminutum sp. nov. differs further from P. bauri sp. nov. in lacking conspicuous white, rounded dorsolateral spots, although it may have small, white dots, vermiculations and flecks.
P. diminutum sp. nov. is characterized by small adult size (Hahn, 1968; Hammerson, 1999). Hammerson (1999:222) calculated a mean snout-vent length of 43 mm for males and 54 mm for females, with a maximum of 51 mm and 66 mm for males and females respectively. His comparisons with samples from northeastern, southeastern, and western Colorado revealed that all exceeded the size of the San Luis Valley specimens. The greatest size disparity was found between San Luis Valley samples and those from western and southwestern Colorado, and this is likely explained by the inclusion of P. hernandesi.
The males of P. diminutum sp. nov. and P. brevirostris are similar in mean snout-vent length although males of P. brevirostris exceed males of the former by 12 mm in maximum size. Males of both taxa are smaller than males of P. bauri sp. nov. Snout-vent length comparisons among females reveal that females of P. diminutum sp. nov. average smaller snout-vent length than females of P. brevirostris, and the latter are smaller than P. bauri sp. nov. (Table 5).
P. diminutum sp. nov. is distinguished from P. h. hernandesi and P. h. ornatum by a smaller adult size, a rounded or angular and steeply inclined rostrofrontal profile, a frontal rim not elevated or only slightly elevated above the occipital shelf (except P. h. ornatum), a shorter temporal shelf, and shorter occipital and temporal horns. P. diminutum sp. nov. can be distinguished from P. o. ornatissimum and P. o. brachycercum by its smaller adult size, a frontal rim not elevated or only slightly elevated above the occipital shelf, a shorter temporal shelf, shorter occipital and temporal horns, a relatively longer tail, small wedge-shaped or rounded dorsal spots, absence of a discrete white and/or yellow line along the medial border of each dorsal spot (except P. o. brachycercum), and a gular pattern of scattered spots and vermiculations with or without gray suffusion and black spots on the abdomen (melanin-dispersed phase). P. diminutum sp. nov. is distinguished from P. douglasii by a gular pattern consisting of melanistic spots and/or vermiculations and melanistic spots on the abdomen (melanin-dispersed phase), a less convex temporal shelf, and a moderately broad, elliptic, and exposed tympanum. 
EtymologyThe subspecific epithet diminutum, Latin perfect participle of dēmĭnŭo, dēmĭnuěre, meaning “diminutive,” is in reference to the small adult size of this species. 
  • Cope, E.D. 1900. The crocodilians, lizards and snakes of North America. Ann. Rep. U.S. Natl. Mus. 1898: 153-1270 - get paper here
  • Gentry, A.F. 1885. A review of the genus Phrynosoma. Proc. Acad. Nat. Sci. Philad. (ser. 3) 37: 138-148 - get paper here
  • MONTANUCCI, RICHARD R. 2015. A taxonomic revision of the Phrynosoma douglasii species complex (Squamata: Phrynosomatidae) Zootaxa 4015 (1): 001–177
  • Reeve, Wayne L. 1952. Taxonomy and distribution of the horned lizard genus Phrynosoma. Univ. Kansas Sci. Bull. 34 (14): 817-960 - get paper here
  • Smith, Hobart M. 1946. Handbook of Lizards: Lizards of the United States and of Canada. Comstock, Ithaca, NY, xxii + 557 pp.
  • Van Denburgh, John 1922. The Reptiles of Western North America. Volume I. Lizards and Volume II. Snakes and Turtles. Occ. Pap. Cal. Acad. Sci. (10): 1–612; 613-1028 - get paper here
  • Zamudio, Kelly R., Jones, K. Bruce & Ward, Ryk H. 1997. Molecular systematics of Short-horned lizards: Biogeography and taxonomy of a widespread species complex. Systematic Biology 46 (2): 284-305 - get paper here
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