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Red-tailed Green Ratsnake Gonyosoma oxycephala toronto zoo.jpg
Gonyosoma oxycephalum
at the Toronto Zoo
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Family: Colubridae
Subfamily: Colubrinae
Genus: Gonyosoma
Wagler, 1828

Six species, see text.

Gonyosoma is a genus of colubrid snakes.


There are a few distinct morphological characteristics that distinguish Gonyosoma from Elaphe. In scutellation there are 2-3 supralabials that contact the eye, with typically two in G. oxycephalum, and three in G. jansenii. The supralabial at the posterior of the eye is highly arched around the back of the eye. The loreal scale is thin and elongate, and appears stretched between the preocular and the nasal. Other diagnostic features is an elongate left rudimentary lung (70–141 mm), and a distinct hemipenes structure.[1]


These snakes have the ability to laterally compress and inflate the first third of their bodies when threatened. The inflated region is typically recoiled into an S, which is elevated above the horizontal forming a typical striking position. The inflation of the body exposes the black and white diagonal bands of the interstitial skin, which is particularly distinct in G. oxycephalum (Schulz 1996). In combination these adaptations impose a most ominous threat!


The following six species are recognized as being valid.[2]

Nota bene: A binomial authority in parentheses indicates that the species was originally described in a genus other than Gonyosoma.

The species formerly known as Gonyosoma cantoris and Gonyosoma hodgsoni have been assigned to the genus Othriophis as Othriophis cantoris and Othriophis hodgsoni, respectively.


  1. ^ Schulz, Klaus-Dieter. 1996. A Monograph of the Colubrid Snakes of the Genus Elaphe Fitzinger. Havlickuv Brod, Czech Republic: Koeltz Scientific Books. 439 pp. ISBN 80-901699-8-8.
  2. ^ "Gonyosoma ". The Reptile Database. www.reptile-database.org.

Further reading[edit]

  • Wagler J. 1828. Descriptiones et Icones Amphibiorum. Munich, Stuttgart and Tübingen: J.G. Cotta. Plates I-XXXVI + 81 unnumbered pages. (Gonyosoma, new genus, Plate IX + 2 unnumbered pages). (in Latin and German).