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Tantilla gracilis BAIRD & GIRARD, 1853

IUCN Red List - Tantilla gracilis - Least Concern, LC
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Higher TaxaColubridae, Colubrinae, Colubroidea, Caenophidia, Alethinophidia, Serpentes, Squamata (snakes)
Subspecies 
Common NamesE: Flathead Snake
G: Schlanke Schwarzkopfschlange
S: Culebra Cabeza-plana 
SynonymTantilla gracilis BAIRD & GIRARD 1853: 132
Tantilla hallowelli COPE 1860: 1111
Homalocranion gracile — JAN 1866
Tantilla gracilis — GARMAN 1884: 87
Tantilla gracilis gracilis — BURT 1935
Tantilla gracilis hallowelli — KIRN et al. 1949: 241
Tantilla gracilis gracilis — KIRN et al. 1949
Tantilla gracilis gracilis — TANZER 1966
Tantilla gracilis — CONANT & COLLINS 1991: 221
Tantilla gracilis — LINER 1994
Tantilla gracilis — ERNST & ERNST 2003: 346
Tantilla gracilis — BARTS 2006
Tantilla gracilis — WILSON & MATA-SILVA 2014: 34
Tantilla gracilis — WALLACH et al. 2014: 701 
DistributionUSA (Texas, C/E Oklahoma, SE Kansas, S Missouri, Illinois, Arkansas, NW Louisiana), Mexico (NE Coahuila)

Elevation: 0-610 m (WILSON & MATA-SILVA 2014)

Type locality: Indianola, Calhoun Co., Texas, USA.  
Reproductionoviparous 
TypesHolotype: UMMZ 3781 (Kluge 1984); previously USNM 4500, a number for a lot of 11 specimens, two of which are still in the USNM collection. It is likely that the real holotype is either USNM 2040 or 2041, both of which are indicated in the USNM catalogue to be from Indianola, Texas, and to have been collected by J. D. Graham. Neither of these specimens, however, currently can be located (Steve W. Gotte, cited in WILSON 1999). The status of these specimens is uncertain: while UMMZ 3781 is in good conditions, the catalogue entry for USNM 4500 says “poorly preserved body fragments” (M. Salimian, pers. comm., 1 June 2023).
Holotype: ANSP 3365 [hallowelli] 
DiagnosisUnfortunately we had to temporarily remove additional information as this was scraped by multiple AI companies who sell that data to their customers. These details, e.g. detailed descriptions or comparisons (about 2540 characters), are available for collaborators and contributors. Please contact us for details. 
CommentSynonymy: partly after WALLACH et al. 2014. Hardy & Cole 1968 synonymized T. g. hallowelli with T. gracilis. 
EtymologyNamed after Latin “gracilis”, meaning “slender or thin”, or small or lanky, or gracile. 
References
  • Baeza-Tarín, F., Hernández, T., Herr, M., Giovanetto, L., Lazcano, D., & Graham, S. P. 2025. NEW DISTRIBUTION RECORDS OF AMPHIBIANS AND REPTILES OF MADERAS DEL CARMEN, COAHUILA, MEXICO. The Southwestern Naturalist, 68(4), 257-262 - get paper here
  • Baird, S. F. and C. Girard. 1853. Catalogue of North American Reptiles in the Museum of the Smithsonian Institution. Part 1.-Serpents. Smithsonian Inst., Washington, xvi + 172 pp. - get paper here
  • Barts, M. 2006. Herpetologische Beobachtungen im US-Bundesstaat Oklahoma. Reptilia (Münster) 11 (61): 43-50 - get paper here
  • BASSETT, LAWRENCE G.; SHASHWAT SIRSI & MICHAEL R.J. FORSTNER. 2021. TANTILLA GRACILIS (Flat-headed Snake). PREDATION. Herpetological Review 52 (1): 172. - get paper here
  • Blanchard, Frank N. 1938. Snakes of the genus Tantilla in the United States. Zoological Series of Field Museum of Natural History 20 (28): 369-376 - get paper here
  • Bogosian, Victor; Eric C. Hellgren, and Raymond W. Moody 2012. Assemblages of Amphibians, Reptiles, and Mammals on an Urban Military Base in Oklahoma. Southwestern Naturalist 57 (3): 277-284. - get paper here
  • Burt, Charles E. 1935. Further records of the ecology and distribution of amphibians and reptiles in the middle west. American Midland Naturalist 16 (3): 311-336 - get paper here
  • Cobb, V.A. 2004. Diet and Prey Size of the Flathead Snake, Tantilla gracilis Copeia 2004 (2): 397-402. - get paper here
  • Collins, J.T. & Collins, S.L. 2006. A pocket guide to Kansas snakes. Great Plains Nature Center, Wichita, 69 pp.
  • Collins, J.T. & Collins, S.L. 2009. A pocket guide to Kansas snakes, 2nd ed. Great Plains Nature Center, Wichita, 69 pp.
  • Collins, J.T. & Collins, S.L. 2010. A pocket guide to Kansas snakes, 3rd ed. Great Plains Nature Center, Wichita, 69 pp.
  • Conant,R. & Collins,J.T. 1991. A Field Guide to Reptiles and Amphibians of Eastern/Central North America, 3rd ed. Houghton Mifflin (Boston/New York), xx + 450 p.
  • Cope, E.D. 1900. The crocodilians, lizards and snakes of North America. Ann. Rep. U.S. Natl. Mus. 1898: 153-1270 - get paper here
  • Cox, Christian L; Joel F Stringer, Matthew A Moseley, Paul T Chippindale, Jeffrey W Streicher 2018. Testing the geographical dimensions of genetic diversity following range expansion in a North American snake. Biological Journal of the Linnean Society 125 (3): 586–599 - get paper here
  • 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
  • Dixon, James R. 2000. Amphibians and reptiles of Texas, second edition. Texas A&M University Press, 421 pp.
  • Dundee, H.A., & Rossman, D.A. 1989. The amphibians and reptiles of Louisiana. Louisiana St. Univ. Press, Baton Rouge 300 pp.
  • Duran M 2021. An annotated checklist of the amphibians and reptiles of North Padre Island, Texas, USA, with comparisons to adjacent barrier island and mainland herpetofauna. ZooKeys 1073: 119-175 - get paper here
  • Edmond, Brian S. 1993. Tantilla gracilis (Flathead Snake). USA: Missouri. Herpetological Review 24 (2): 68-69 - get paper here
  • Ernst, C.H. & Ernst, E.M. 2003. Snakes of the United States and Canada. Smithsonian Inst. Press, Washington, 668 pp.
  • Ernst, C.H., & Barbour, R.W. 1989. Snakes of eastern North America. George Mason Univ. Press, Fairfax, VA 282 pp.
  • Fisher, Clyde B. 1973. Status of the Flat-Headed Snake, Tantilla gracilis Baird and Girard, in Louisiana. Journal of Herpetology 7 (2): 136-137 - get paper here
  • Force, Edith R. 1934. A local study of the opisthoglyph snake Tantilla gracilis Baird and Girard. Papers of the Michigan Academy of Science, Arts, and Letters 20: 645-659
  • Garman, Samuel 1884. The reptiles and batrachians of North America. Mem. Mus. comp. Zool, Cambridge (Massachusetts), 8 (3): xxxiv + 185 pp. [1883] [CNAH reprint 10] - get paper here
  • Goldberg, S.R. 2015. Reproduction in the Flat-headed Snake, Tantilla gracilis (Serpentes, Colubridae). Sonoran Herpetologist 28 (4):35-37. - get paper here
  • Hardy, Laurence M.;Cole, Charles J. 1968. Morphological variation in a population of the snake, Tantilla gracilis Baird and Girard. University of Kansas Publications Museum of Natural History 17 (15): 613-629 - get paper here
  • Heimes, P. 2016. Snakes of Mexico. Chimaira, Frankfurt, 572 pp
  • Irwin, Kelly J. 2004. Arkansas Snake Guide. Arkansas Game & Fish Commission, Little Rock, 50 pp.
  • Jan, G. 1866. Iconographie générale des ophidiens. 15. Livraison. J.B. Bailière et Fils, Paris - get paper here
  • Kirn, Albert J.; Burger, W. Leslie; Smith, Hobart M. 1949. The subspecies of Tantilla gracilis. American Midland Naturalist 42 (1): 238-251 - get paper here
  • Lazcano D, Nevárez-de los Reyes M, García-Padilla E, Johnson JD, Mata-Silva V, DeSantis DL, Wilson LD. 2019. The herpetofauna of Coahuila, Mexico: composition, distribution, and conservation status. Amphibian & Reptile Conservation 13(2) [General Section]: 31–94 (e189) - get paper here
  • Marcou, Zachary John 2018. Delineating Metrics of Diversity for a Snake Community in a Rare Ecosystem. MSc Thesis, Stephen F. Austin State University - get paper here
  • McAllister, Chris T., Christa Brummett and Henry W. Robison. 2010. Geographic distribution: Tantilla gracilis. Herpetological Review 41 (3): 382 - get paper here
  • PANDELIS, GREGORY G.; COREY E. ROELKE & NEIL R. BALCHAN. 2021. Eleven New County Records for Reptiles and Amphibians in Texas, USA. Herpetological Review 52 (1): 101–102.
  • Savitzky, Alan H. and Joseph T. Collins 1971. Tantilla gracilis, a Snake New to the Fauna of Mexico. Journal of Herpetology 5 (1-2):86-87 - get paper here
  • Smith, C.C. & Acker, G. 1940. A Collection of Reptiles from Logan County, Oklahoma. Proceedings of the Oklahoma Academy of Science 20: 65 - get paper here
  • Smith, Hobart M.;Leonard, Arthur B. 1934. Distributional records of reptiles and amphibians in Oklahoma. American Midland Naturalist 15: 190-196 - get paper here
  • Smith, Philip W. 1956. Extension of known range of the flat-headed snake. Herpetologica 12: 327 - get paper here
  • Tanzer, Ernest C.;Morrison, Eston O.;Hoffpauir, Charles 1966. New locality records for amphibians and reptiles in Texas. Southwestern Naturalist 11 (1): 131-132 - get paper here
  • Taylor, Edward H. 1937. Notes and comments on certain American and Mexican snakes of the genus Tantilla, with descriptions of new species. Transactions of the Kansas Academy of Science 39 [1936]: 335-348 - get paper here
  • Tennant, A. 2003. Snakes of North America - Eastern and Central Regions, revised edition. Lone Star Books, 605 pp.
  • Tennant, A. & Bartlett, R.D. 2000. Snakes of North America - Eastern and Central Regions. Gulf Publishing, Houston, TX, 588 pp.
  • 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.
  • Weidler, J M 2019. Protected areas of Texas in relation to Texas reptiles. Herpetological Review 50 (3): 462-473 - get paper here
  • Werler, John E. & James R. Dixon 2000. Texas Snakes. University of Texas Press, 544 pages
  • Wilgers, D.J.; Horne, E.A.; Sandercock, B.K. & Volkmann, A.W. 2006. Effects of rangeland management on community dynamics of the herpetofauna of the Tall-grass Prairie [Flint Hills, Kansas/Oklahoma]. Herpetologica 62 (4): 378-388 - get paper here
  • Williams, John T. and Thomas A. Sinclair. 2013. Geographic Distribution: Tantilla gracilis (flat-headed snake). Herpetological Review 44 (3): 478 - get paper here
  • Wilson, L.D. 1999. Checklist and key to the species of the genus Tantilla (Serpentes: Colubridae), with some commentary on distribution. Smithsonian Herp. Inf. Serv. (122): 1-34 - get paper here
  • Wilson, Larry David and Vicente Mata-Silva 2015. A checklist and key to the snakes of the Tantilla clade (Squamata: Colubridae), with comments on distribution and conservation. Mesoamerican Herpetology 2 (4): 418 - get paper here
  • Wilson, Larry David and Vicente Mata-Silva. 2014. Snakes of the genus Tantilla (Squamata: Colubridae) in Mexico: taxonomy, distribution, and Conservation. Mesoamerican Herpetology 1 (1): 5-95 - get paper here
 
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