Jansenii / Oxycephalum
By Freight Freitas
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. oxycephala, and three in G. janseni. The supralabial at the posterior eye is highly arched around the back of the eye. The loreal scale is thin and elongate, and appears stretched between the preoccular and the nasal. Other diagnostic features include an elongate left rudimentary lung (70-141mm), and a distinct hemipenes structure (Schulz 1996).
These snakes have the ability to laterally compress and inflate the first 3rd 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. oxycephala (Schulz 1996). In combination these adaptations impose a most ominous threat! There has also been some documentation of musking in G. oxycephala, but I cannot confirm this through my own experiences. There is, however, a distinct and pleasant odor similar to unsweetened baker’s chocolate that is emitted when stressed by many of my snakes.