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Non-front-fanged Colubroid Snakes

A large number of colubroid species have been traditionally and inaccurately grouped in an artificial family, the Colubridae. The family Colubridae was first defined in 1758 by the Swedish natural historian and founder of systematic zoology/taxonomy, Carl Nilsson Linnaeus (Carl von Linné or Carolus Linnaeus; 1707-1778). The name, “Colubridae”, is derived from the rather non-descript Latin, “coluber”, the general term for “snake” or “serpent”. Of the approximately 3,350 species of extant (living) snakes, the previous definition of the Colubridae included about 70% of these taxa (e.g. about 2,345 species). A significant number of these were included in the family because their relationships to other snakes were unclear or un-established, and placement in the Colubridae served to provide a kind of “interim” status. Of course, this resulted in the Colubridae assuming the identity of an artificial assemblage, rather than a true taxonomic grouping.

On the basis of several morphological and/or molecular systematics investigations (some of which disagree), the number of previous sub-families included under the Colubridae have been markedly re-defined with several raised to full family status, while others have been retained within the original family that is now comprised of an estimated 1,750 species (about 74% of the previous assemblage). As currently defined, these snakes are represented by taxa with relatively wide distribution in the Neotropics, North America, Africa, Southeast Asia, Europe, with the least representation in Australia, which include newly defined families that previously were included as “colubrids”. These are now collectively and more accurately termed, “non-front-fanged colubroids” (NFFC), as these are all “advanced snakes” that do not possess the canaliculated (hollow or lumenate) venom apparatus located on the anterior maxillae (forward part of the upper jaw) as found in front-fanged colubroids such as elapids, viperids and Atractaspis spp.

Most NFFC are not known to be venomous biologically or clinically, although bites from some of its species have produced effects in humans. These effects range from insignificant or trivial injuries to death. However, a few species have evolved fangs towards the back of the mouth, which deliver venom from venom glands.

FIGURE: Diagramatic representation of a "typical" NFFC snake head, showing the fang placed towards the back of the mouth.

FIGURE: Approximate distribution of NFFC snakes globally.

Several of these species have caused human fatalities or major envenoming.

TABLE: NFFC snakes reported to have caused major or lethal envenoming.

Scientific name Common name Effect
Dispholidus typus Boomslang Coagulopathy & haemorrhage
Thelotornis spp. Vine snakes Coagulopathy & haemorrhage
Rhabdophis spp. Yamakagashi, red necked keelback Coagulopathy & haemorrhage
Malpolon monspessulanus Montpelier snake Mild neurotoxicity (Cranial nerve palsy)
Philodryas olfersii    
Boiga irregularis Brown tree snake Local swelling, plus respiratory distress & possible mild paralysis in infants only

A further group of Colubrid snakes have evolved toxic oral secretions, inoculated during the biting process, though not using fangs. There is increasing evidence that at least some of these species can cause significant injury to humans. Some other Colubrids reported to cause effects in humans are listed below. This list is not exhaustive and most Colubrids should be considered as having some potential to cause at least local envenoming, whether via back-fangs or inoculation of toxic oral secretions.

TABLE: Some Colubrid snakes reported capable of causing mild envenoming (this list is not exhaustive).

Scientific name Common name Effect
Ahaetulla nasuta Asian green whipsnake Local swelling, ± discolouration, lymphangitis.
Amplorhinus multimaculatus African many spotted snake Local swelling, ±, headache, nausea.
Balanophis ceylonensis Sri Lankan keelback Local swelling, ± discolouration, bleeding, lymphangitis.
Boiga spp. (eg. blandingii, ceylonensis, dendrophila, forsteni) Tree snakes from Africa & Asia Local swelling, ± discolouration, bleeding, lymphangitis; headache, nausea.
Cerberus rhynchops Indian dog faced water snake Local swelling, ± discolouration, lymphangitis.
Coluber spp. (eg ravergieri, rhodorachis) African racer Local swelling, ± discolouration, bleeding, lymphangitis.
Crotaphopeltis hotamboeia African herald snake Local swelling.
Enhydris enhydris Asian rainbow water snake Local swelling, ± discolouration, lymphangitis.
Madagascarophis meridionalis Madagascan snake Local swelling, ± discolouration, bleeding, blistering, necrosis, lymphangitis, headache, nausea.
Malpolon moilensis African hooded malpolon Local swelling, ± discolouration, lymphangitis.
Psammophis sibilans African racer Local swelling, ± discolouration, bleeding, lymphangitis, headache, nausea.
Psammophylax spp. (selected) African skaapstekers Local swelling, ± discolouration, bleeding, lymphangitis, headache, nausea.
Telescopus semiannulatus African tiger snake Local swelling, ± discolouration, bleeding, lymphangitis, headache, nausea.

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