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Thamnophis unilabialis TANNER, 1985

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Higher TaxaColubridae (Natricinae), Colubroidea, Caenophidia, Alethinophidia, Serpentes, Squamata (snakes)
Common NamesE: Madrean Narrowheaded Garter Snake
S: Jarretera Cabeza-angosta 
SynonymThamnophis rufipunctatus unilabialis TANNER 1985: 648
Thamnophis unilabialis — WOOD et al. 2011
Thamnophis unilabialis — WALLACH et al. 2014: 727 
DistributionMexico (E Sonora, Chihuahua, Durango)

Type locality: 0.5 mi SW of Bocoyna, Chihuahua, Mexico.  
TypesHolotype: BYU 14217, adul female; paratypes: BYU, ASU, UAZ, NMMZ, AMNH, UTEP 
DiagnosisDiagnosis: A subspecies of rufipunctatus that differs from both r. rufipunctatus and r. nigronuchalis in having only the 4th supralabial contacting the eye by reason of the lower postocular having a firm contact with the 4th labial; ventral reduced and ventral-caudal averages 13-15 scales fewer than in r. rufipunctatus. Ventral color pattern with anterior margins of scales usually pigmented, forming alternating dark and light transverse bands. (Tanner 1985) 
CommentSynonymy: The subspecific distinctness of T. r. unilabialis was based on its having only one supralabial contacting the orbit (usually two in T. r. rufipunctatus), fewer ventrals and subcaudals than T. r. rufipunctatus, and a different ventral pattern than T. r. rufipunctatus. Rossman (1995) showed that only the differences in ventral and subcaudal numbers are reasonably consistent, and he concluded that this seemed an insufficient basis for taxonomic recognition of the Mexican populations. (Rossman et al. 1996: 39, 245)

Distribution: see map in Wood et al. 2011: 3838. 
EtymologyNot explicitly given by Tanner but apparently named after the 4th supralabial which is the only supralabial contacting the eye. 
  • Heimes, P. 2016. Snakes of Mexico. Chimaira, Frankfurt, 572 pp
  • Lemos-Espinal JA, Smith GR, Gadsden-Esparza H, Valdez-Lares R, Woolrich-Piña GA 2018. Amphibians and reptiles of the state of Durango, Mexico, with comparisons with adjoining states. ZooKeys 748: 65-87 - 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
  • Rorabaugh, J C; Turner, D; van Devender, T R; Hugo-Cabrera, V; Maynard, R J; Van Devender, R W; Villa, R A; Hamilton, P; Hale, S F; Aguilar-Morales, C; Blanco-Gutiérrez, A; Wallace, E & Hedgcock, C; 2019. Herpetofauna of the Mesa Tres Ríos area in the Northern Sierra Madre Occidental of Sonora, Mexico. Herpetological Review 50 (2): 251-259 - get paper here
  • Tanner, Wilmer W. 1985. Snakes of Western Chihuahua. Great Basin Naturalist 45 (4): 615-676 - get paper here
  • Wallach, Van; Kenneth L. Williams , Jeff Boundy 2014. Snakes of the World: A Catalogue of Living and Extinct Species. [type catalogue] Taylor and Francis, CRC Press, 1237 pp.
  • Wood, Dustin A.; A. G. Vandergast, J . A. Lemos Espinal, R. N. Fisher & A. T. Holycross 2011. REFUGIAL ISOLATION AND DIVERGENCE IN THE NARROWHEAD GARTER SNAKE SPECIES COMPLEX (THAMNOPHIS RUFIPUNCTATUS) AS REVEALED BY MULTILOCUS DNA SEQUENCE DATA. Molecular Ecology 20: 3856–3878 - get paper here
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