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Crotalus concolor WOODBURY, 1929

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Higher TaxaViperidae, Crotalinae, Colubroidea, Caenophidia, Alethinophidia, Serpentes, Squamata (snakes)
Common NamesE: Midget Faded Rattlesnake 
SynonymCrotalus concolor WOODBURY 1929
Crotalus confluentus decolor KLAUBER 1930 (nom. subst.)
Crotalus viridis concolor — KLAUBER 1936
Crotalus viridis decolor — GLOYD 1940
Crotalus confluentus decolor — WOODBURY & SMITH 1951
Crotalus viridis concolor — KISSER 1980
Crotalus viridis concolor — CROTHER 2000: 60
Crotalus oreganus concolor — ASHTON et al. 2001
Crotalus concolor — DOUGLAS et al. 2002
Crotalus concolor — HOUSTON 2006
Crotalus oreganus concolor — CAMPBELL & LAMAR 2004
Crotalus oreganus concolor — BEAMAN & HAYES 2008
Crotalus concolor — HOSER 2009
Crotalus viridis concolor — WERNING 2012
Crotalus oreganus concolor — CROTHER et al. 2012
Crotalus concolor — WALLACH et al. 2014: 189
Crotalus concolor — DAVIS et al. 2016 
DistributionUSA (Utah: basins of the Colorado and Green Rivers)

Type locality: “King’s Ranch, Garfield Co., at base of the Henry Mtns.” [= Utah, USA].  
TypesHolotype: UMNH 306 (Natural History Museum of Utah, Drew Dittmer, pers. comm., 24 March 2021), given as UTAH 306 by Gloyd 1940: 216; also see comment. 
DiagnosisDescription: Rather small in size, the length measuring 70 cm. Slender, the body, as usual, being thickest in the middle and tapering slightly in both directions; neck constricted; head broad and flat. The rattles small and delicate; six rattles present, of which the sixth is broken, these measuring 8.5 x 20 mm.
Scale rows twenty-five over middle and caudal part of anterior region, reducing in number caudad; all keeled excepting those of the first row; heavy dorsally but weaker on the sides. Abdominal plates 175; the tail plates numbering 25-j-2, mostly in a single series. Top of head covered by small irregular scales except for the large supraoculars; anterior nasal large, in contact with the rostral which is higher than wide (6:5); upper labials 13, separated from eye by 3-4 rows of small scales; lower labials 15; first pair of genials very small, the second pair enlarged (Woodbury 1929).

Coloration: General appearance, a reddish-yellow brown. A faint or almost obsolete pattern of slightly darker brown rhombs of which there are about 40 along the dorsum difficult to trace but mostly connecting with spots of similar color on the sides, these spots reaching the first row of scales; this pattern giving way on the tail to faint cross-bands which are ten in number. Indications of an extremely faint postocular line passing horizontally to the posterior edge of the mouth. Abdominal plates more yellow but in most cases grading to a slightly darker yellowish brown peppered with spots of darker color at each end of the plate (Woodbury 1929).

For a redescription of the Holotype see Halm et al. 2022. 

Synonymy: Note that Klauber 1930 created a new name (”decolor”) as he believed that Crotalus concolor was pre-occupied by Jan 1859: 153, a nomen nudum which originally appeared as a variety of C. durissus [horridus], and was later placed in the synonymy of C. horridus by Garman (1883: 175) and by Stejneger (1895: 427) fide Gloyd 1940: 216. Jan’s specimen was supposedly deposited in Munich (ZSM) but is now lost.

Distribution: see map in Davis et al. 2016 (Fig. 2).

SIZE: up to 63 cm 
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