Toxicofera

Image:Mexican ridged nosed rattlesnake head.jpg Image:Iguana Costa Rica.jpg Image:Varanus benghalensis.jpg

Toxicofera (Latin for "those who bear toxins"), is a cladewhich represents about 4600 species (nearly 60%) of Squamates; it encompasses all venomousreptilespecies, as well as numerous related non-venomous species.

Details

Toxicofera combines the following groups from traditional classification:

• suborder Serpentes(snakes)
• suborder Iguania(anoles, chameleons, iguanas, etc.)
• infraorder Anguimorpha, consisting of:
  • family Varanidae(monitor lizards, including the Komodo dragon)
  • family Anguidae(alligator lizards, glass lizards, etc.)
  • family Helodermatidae(Gila monsterand Mexican beaded lizard)

Background

In 2003groundbreaking work by Dr. Bryan Grieg Frywas published that showed nearly all "non-poisonous" snakes produce venom to a certain extent. This suggested a far more ancient origin for venom in Serpentes than had been considered until then, laying the foundation for future research.

Prior to the publication of the Toxicofera hypothesis, venom in Squamates was only known in Serpentes and Helodermatidae. Part of the original research that led to the venom clade was the discovery of venom (or venom genes) in species from groups (Iguania and Varanidae) which were not previously known to produce it (Anguidae was included in the venom clade for phylogeneticreasons).

Toxicofera was described simply as the "venom clade" when first proposed to the scientific communityby Fry, et al, in the Journal Naturein 2005. It was given a formal name by his associates, Vidal and Hedges, in the Journal Comptes Rendus Biologies(CR Biologies) the same year.

Conclusions

It was estimated that the common ancestral species that first developed venom in the venom clade lived on the order of 200 million years ago, approximately 100 million years before snakes evolved.

The venoms are thought to have resulted after genes normally active in various parts of the body duplicatedand the copies found new use in the salivary glands.

The newly discovered diversity of Squamate species producing venoms is a treasure trovefor those seeking to develop new pharmaceutical drugs; many of these venoms lower blood pressure, for example.

External links

• Venom Hunt Finds 'Harmless' Snakes A Potential DangerDecember 16, 2003
• Lizards' poisonous secret is revealedNovember 16, 2005
• The Surprising Origin of Venom RevealedNovember 17, 2005
• Which Came First, the Snake or the Venom?November 21, 2005
• Genealogy of scaly reptiles rewritten by new researchNovember 22, 2005

Papers

• Molecular Evolution and Phylogeny of Elapid Snake Venom Three-Finger ToxinsJuly 2003
• The phylogeny of squamate reptiles (lizards, snakes, and amphisbaenians) inferred from nine nuclear protein-coding genesAvailable online October 27, 2005
• Early evolution of the venom system in lizards and snakesAvailable online November 16, 2005

Dr. Fry

• Homepage
• The Venom Cure: The Power of Poison
• Dr. Fry's Near Fatal Attraction
• Nature Podcast November 17, 2005(Dr. Fry's segment on Komodo dragonsbegins 22 minutes into the program)

This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Toxicofera Wikipedia article Toxicofera.