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Reptiles Guide

Toxicofera

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Snake
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Iguana
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Monitor Lizard

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

Contents

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 monster and Mexican beaded lizard)

Background

In 2003 groundbreaking work by Dr. Bryan Grieg Fry was 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.

Before 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 phylogenetic reasons).

Toxicofera was described simply as the "venom clade" when first proposed to the scientific community by Fry, et al, in the Journal Nature in 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 duplicated and the copies found new use in the salivary glands.

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

External links

Papers

Dr. Fry


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