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Sonora annulata (BAIRD, 1859)

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Higher TaxaColubridae, Colubrinae, Colubroidea, Caenophidia, Alethinophidia, Serpentes, Squamata (snakes)
SubspeciesSonora annulata annulata (BAIRD 1859)
Sonora annulata klauberi (STICKEL 1941) 
Common NamesColorado Desert Shovelnose Snake
klauberi: Tucson Shovelnose Snake 
SynonymLamprosoma annulatum BAIRD 1859
Chionactis occipitalis annulata — SMITH & HOLLAND 1971
Chionactis occipitalis saxatilis FUNK 1967
Chionactis occipitalis annulata — CROTHER 2000: 58
Chionactis occipitalis annulata — CROTHER et al. 2012
Chionactis annulata annulata — WOOD et al. 2014
Chionactis annulata — FELDMAN et al. 2015
Sonora (Chionactis) annulata — COX et al. 2018: 975
Chionactis annulata — LEMOS-ESPINAL et al. 2019
Sonora annulata — HERPMAPPER 2020

Sonora annulata klauberi (STICKEL 1941)
Sonora occipitalis klauberi STICKEL 1941
Chionactis occipitalis klauberi — CROTHER 2000: 58
Chionactis occipitalis klauberi — CROTHER et al. 2012
Chionactis annulata klauberi — WOOD et al. 2014
Sonora annulatus klauberi — COX et al. 2018 
DistributionUSA (SE California, Arizona, Baja California); Terra typica: “Colorado desert”, restricted to Holtville, Imperial County, California by SMITH & TAYLOR 1950.

klauberi: USA (SC Arizona: Sonoran Desert); Type locality: "Tucson, Pima County. Arizona”  
TypesSyntypes: USNM 2105a and 2105b
Holotype: SDNHM = SDSNH 29647, adult male; paratype SDNHM = SDSNH 17115 [klauberi]
Syntype: USNM 2105, 2106 [Lamprosoma annulatum] 
DiagnosisDiagnosis: Sonora annulata can be distinguished from all other Sonora, excepting S. occipitalis and S. palarostris, by the presence of a flattened, spadelike rostrum. Wood et al. (2014); distinguish S. annulata from S. occipitalis by the presence of black crossbands (as opposed to brown crossbands in S. occipitalis) and the presence of a red secondary crossband. Sonora annulata can be distinguished from S. palarostris by having more than 23 crossbands (as opposed to less than 23 in S. palarostris) according to Wood et al. (2014) (Cox et al. 2018: 975).

Variation: Wood et al. (2014) recognize two different subspecies of S. annulata, S. a. annulata and S. a klauberi. Sonora a. annulata is distinguished from S. a. klauberi by the absence of maculations on dorsal scales and the lower proportion of maculations in the centre of scales. Sonora a. annulata is restricted to the Colorado Desert basin, while S. a. klauberi is restricted to the remainder of the Sonoran desert (Cox et al. 2018: 975).

Klauber considered the composite character ‘‘number of dark bands on the body plus unmarked anterior band positions on the ventrum’’ to be the most important numerical character distinguishing C. o. annulata from C. o. occipitalis and arbitrarily assigned a threshold that defined C. o. annulata as having ‘‘usually fewer than 45’’. He further observed that about 20% of C. o. occipitalis specimens fell below this criterion and about 10% of C. o. annulata specimens have 45 or more. 
CommentSynonymy: mostly after Mahrdt et al. 2001. WALLACH et al. 2014: 160 listed this species as a synonym of Chionactis occipitalis.

Subspecies: Wood et al. (2008) concluded that “Neither molecular nor morphological data are concordant with the traditional C. occipitalis subspecies taxonomy. Mitochondrial sequences suggest specimens recognized as C. o. klauberi are embedded in a larger geographic clade whose range has expanded from western Arizona populations, and these data are concordant with clinal longitudinal variation in morphology.” Consequently, the subspecies of C. occipitalis should be rejected.
The subspecies are distinguished partly by ventral scale counts and number of dark bands encircling the body, but the most striking variation is in pattern and coloration of secondary bands (Stickel 1941; Klauber 1951).

Distribution: not in Sonora fide Lemos-Espinal et al. 2019 but in Sonora fide Cox et al. 2018 (map in Fig. 5). 
EtymologyThe name occipitalis is derived from the Latin occipit meaning the back of the head, in reference to "the occipital crescent blotch" (Baird 1859a). 
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  • Banta, Benjamin H. 1953. Some herpetological notes from southern Nevada. Herpetologica 9: 75-76 - get paper here
  • Barts, M. 2009. Chionactis occipitalis annulata (BAIRD). Sauria 31 (4): 2 - get paper here
  • Bezy, R. L., P. C. Rosen, T. R. Van Devender, and E. F. Enderson. 2017. Southern distributional limits of the Sonoran Desert herpetofauna along the mainland coast of northwestern Mexico. Mesoamerican Herpetology 4(1): 138–167 - get paper here
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  • Crother, B. I. (ed.) 2012. Standard Common and Current Scientific Names for North American Amphibians, Turtles, Reptiles, and Crocodilians, Seventh Edition. Herpetological Circular 39: 1-92
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  • Stickel, W.H. 1943. The Mexican snakes of the genera Sonora and Chionactis with notes on the status of other colubrid genera. Proc. Biol. Soc. Washington 56: 109-128 - get paper here
  • Stickel, William H. 1938. The snakes of the genus Sonora in the United States and Lower California. Copeia 1938 (4): 182-190 - get paper here
  • Stickel, William H. 1941. The subspecies of the spade-nosed snake, Sonora occipitalis. Bull. Chicago Acad. Sci. 6: 135-140
  • Werning, Heiko 2012. Die Reptilien und Amphibien des Südwestens. Draco 13 (50): 18-60 - get paper here
  • Wood DA, Fisher RN, Vandergast AG 2014. Fuzzy Boundaries: Color and Gene Flow Patterns among Parapatric Lineages of the Western Shovel-Nosed Snake and Taxonomic Implication. PLoS One 9 (5): e97494. doi:10.1371/journal.pone.0097494 - get paper here
  • Wood, D.A.; Meik, J.M.; Holycross, A.T.; Fisher, R.N. & Vandergast, A.G. 2008. Molecular and phenotypic diversity in Chionactis occipitalis (Western Shovel-nosed Snake), with emphasis on the status of C. o. klauberi (Tucson Shovel-nosed Snake). Conservation Genetics 9:1489–1507 - get paper here
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