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Encyclopedia > Toxicofera
Toxicofera
Venomous snakes, such as the rattlesnake shown above, are the most well-known venomous squamates.
Venomous snakes, such as the rattlesnake shown above, are the most well-known venomous squamates.
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Sauropsida
Subclass: Diapsida
Infraclass: Lepidosauromorpha
Superorder: Lepidosauria
Order: Squamata
(unranked) Toxicofera
Beaded Lizard
Beaded Lizard
Agamid Lizard
Agamid Lizard
Monitor Lizard
Monitor Lizard

Toxicofera (Latin for "those who bear toxins"), is a hypothetical clade which represents about 4600 species (nearly 60%) of extant squamates (scaled lizards.)[1] It encompasses all venomous reptile species, as well as numerous related non-venomous species. Head of a Mexican Ridged Nosed Rattlesnake with one of two distinctive cranial pits (thermoreceptors common to all pit vipers) visible between the nostril and eye. ... Species 27 species; see list of rattlesnake species and subspecies. ... Scientific classification redirects here. ... For other uses, see Animal (disambiguation). ... Typical Classes Subphylum Urochordata - Tunicates Ascidiacea Thaliacea Larvacea Subphylum Cephalochordata - Lancelets Subphylum Myxini - Hagfishes Subphylum Vertebrata - Vertebrates Petromyzontida - Lampreys Placodermi (extinct) Chondrichthyes - Cartilaginous fishes Acanthodii (extinct) Actinopterygii - Ray-finned fishes Actinistia - Coelacanths Dipnoi - Lungfishes Amphibia - Amphibians Reptilia - Reptiles Aves - Birds Mammalia - Mammals Chordates (phylum Chordata) include the vertebrates, together with... Typical classes Petromyzontidae (lampreys) Placodermi - extinct Chondrichthyes (cartilaginous fish) Acanthodii - extinct Actinopterygii (ray-finned fish) Actinistia (coelacanths) Dipnoi (lungfish) Amphibia (amphibians) Reptilia (reptiles) Aves (birds) Mammalia (mammals) Vertebrata is a subphylum of chordates, specifically, those with backbones or spinal columns. ... Clades Subclass Anapsida Subclass Diapsida Infraclass Lepidosauromorpha Infraclass Archosauromorpha Sauropsids are a diverse group of mostly egg-laying vertebrate animals. ... Classes Ichthyosauria Sauropterygia Lepidosauria Archosauria Diapsids (two arches) are a group of tetrapod animals that developed two holes (temporal fenestra) in each side their skulls, about 300 million years ago during the late Carboniferous period. ... Orders Sphenodontia Squamata Eosuchia Conservation status: Fossil The Lepidosauria are a subclass of reptiles comprising the orders : Squamata Sphenodontia or Rhynchocephalia Eosuchia Conservation status: Fossil Lepidosaurians are the most successful of modern reptiles. ... Orders Sphenodontia Squamata Eosuchia Conservation status: Fossil The Lepidosauria are a subclass of reptiles comprising the orders : Squamata Sphenodontia or Rhynchocephalia Eosuchia Conservation status: Fossil Lepidosaurians are the most successful of modern reptiles. ... Suborders Lacertilia- Lizards Serpentes - Snakes Amphisbaenia - Worm lizards This article is about the Squamata order of reptiles. ... Image File history File linksMetadata Download high-resolution version (2560x1696, 3270 KB)Mexican Beaded Lizard from the loca reptile house. ... Image File history File linksMetadata Download high-resolution version (2560x1696, 3270 KB)Mexican Beaded Lizard from the loca reptile house. ... Download high resolution version (1000x717, 246 KB) Wikipedia does not have an article with this exact name. ... Download high resolution version (1000x717, 246 KB) Wikipedia does not have an article with this exact name. ... Image File history File links Varanus_benghalensis. ... Image File history File links Varanus_benghalensis. ... For other uses, see Toxin (disambiguation). ... Look up Hypothesis in Wiktionary, the free dictionary. ... A clade is a term belonging to the discipline of cladistics. ... In biology, extant taxon is commonly used in discussions of living and fossil species. ... Suborders Lacertilia- Lizards Serpentes - Snakes Amphisbaenia - Worm lizards This article is about the Squamata order of reptiles. ... It has been suggested that Snake poison be merged into this article or section. ... Reptilia redirects here. ... For other uses, see Species (disambiguation). ...

Contents

Cladistics

Toxicofera would combine the following groups from traditional classification:[1] For other uses, see Scientific classification (disambiguation). ...

Families Acrochordidae Aniliidae Anomalepididae Anomochilidae Atractaspididae Boidae Bolyeriidae Colubridae Cylindrophiidae Elapidae Hydrophiidae Leptotyphlopidae Loxocemidae Pythonidae Tropidophiidae Typhlopidae Uropeltidae Viperidae Xenopeltidae Snakes are cold blooded legless reptiles closely related to lizards, which share the order Squamata. ... Iguania is the suborder of Squamata that contains the iguanas, anoles, etc. ... For other members of the family Iguanidae, see Iguanidae. ... Genera Many: see text Agamas or Agamids are the Agamidae family of lizards, containing more than 300 species in Africa, Asia, Australia and a few in Southern Europe. ... For other uses, see Chameleon (disambiguation). ... Species Many, see text. ... Species Many, see text. ... Genera Anguis Ophisaurus Pseudopus Celestus Diploglossus Ophiodes Abronia Barisia Coloptychon Elgaria Gerrhonotus Mesaspis Classification Family Anguidae Subfamily Anguinae Genus Anguis Genus Ophisaurus Genus Pseudopus Subfamily Diploglossinae Genus Celestus Genus Diploglossus Genus Ophiodes Subfamily Gerrhonotinae Genus Abronia Genus Barisia Genus Coloptychon Genus Elgaria Genus Gerrhonotus Genus Mesaspis Categories: Lizards | Anguids ... The subject of this article might not be notable enough for inclusion in Wikipedia. ... Species see text The Glass Lizards, genus Ophisaurus, are a group of reptiles that resemble snakes, but are actually lizards. ... Classification Genus Heloderma Heloderma horridum: Mexican beaded lizard Heloderma suspectum: Gila monster Categories: Lizards | Helodermas ... Binomial name Cope, 1869 The gila monster (pronounced HEE-la, IPA pronunciation: ) (Heloderma suspectum) is a species of venomous lizard native to the southwestern United States and northern Mexico. ... Binomial name Heloderma horridum Wiegmann, 1829 The beaded lizard or Mexican beaded lizard (Heloderma horridum) is found in Mexico and the southern United States. ...

Research

Venom in squamates has historically been considered a rarity; while it has been known in Serpentes since ancient times, the actual percentage of snake species considered venomous was relatively small (around 25%). Following the classification of Helodermatidae in the 19th century, their venom was thought to have developed independently. The origin of venom in squamates was thus considered relatively recent in evolutionary terms and the result of convergent evolution among the seemingly-polyphyletic venomous snake families. European asp, Vipera aspis Asp is the modern Anglicization of the word Aspis, which in Antiquity referred to any one of several venomous snake species found in the Nile region. ... A venomous snake is a snake that uses modified saliva, venom, delivered through fangs in its mouth, to immobilize or kill its prey. ... This article is about evolution in biology. ... In evolutionary biology, convergent evolution is the process whereby organisms not closely related, independently evolve similar traits as a result of having to adapt to similar environments or ecological niches. ... In biology, a taxon is polyphyletic if it is descended from more than one root form (in Greek poly = many and phyletic = racial). ... The hierarchy of scientific classification In biological classification, family (Latin: familia, plural familiae) is a rank, or a taxon in that rank. ...


In 2003 however, a study was published that described venom in snake subfamilies previously thought to lack it.[2] Further study claimed nearly all "non-venomous" snakes produce venom to a certain extent, suggesting a single, and thus far more ancient origin for venom in Serpentes than had been considered until then.[3][4] As a practical matter, Dr. Bryan Fry cautioned:[5]

Some non-venomous snakes have been previously thought to have only mild 'toxic saliva'. But these results suggest that they actually possess true venoms. We even isolated from a rat snake [Coelognathus radiatus (formerly known as Elaphe radiata)[3]], a snake common in pet stores, a typical cobra-style neurotoxin, one that is as potent as comparative toxins found in close relatives of the cobra. These snakes typically have smaller quantities of venom and lack fangs, but they can still deliver their venom via their numerous sharp teeth. But not all of these snakes are dangerous. It does mean, however, that we need to re-evaluate the relative danger of non-venomous snakes. For the band, see Saliva (band). ... Rat snakes are a type of snake that are members of the Elaphe, Bogertophis, or Senticoli genera. ... Binomial name (F. Boie, 1827) Radiated Ratsnakes or Copperhead Rat Snake Elaphe radiata is a species of snake. ... Egyptian Cobra, Naga haje This article is about snakes. ... A neurotoxin is a toxin that acts specifically on nerve cells – neurons – usually by interacting with membrane proteins such as ion channels. ...

This prompted still further research, which led to the discovery of venom (and venom genes) in species from groups which were not previously known to produce it, e.g. in Iguania (specifically Pogona barbata from the Family Agamidae) and Varanidae (from Varanus varius).[1] It is thought that this was the result of descent from a common venom-producing squamate ancestor; the hypothesis was described simply as the "venom clade" when first proposed to the scientific community.[1] The venom clade included Anguidae for phylogenetic reasons and adopted a previously suggested clade name: Toxicofera.[6] This stylistic schematic diagram shows a gene in relation to the double helix structure of DNA and to a chromosome (right). ... Binomial name Pogona barbata Cuvier, 1829 The Eastern Bearded Dragon (Pogona barbata) is a lizard found in wooded parts of eastern Australia, except for the regions of Cape York. ... Genera Many: see text Agamas or Agamids are the Agamidae family of lizards, containing more than 300 species in Africa, Asia, Australia and a few in Southern Europe. ... This article does not cite any references or sources. ... A phylogeny (or phylogenesis) is the origin and evolution of a set of organisms, usually of a species. ...


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.[1] 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.[2] Schematic of a region of a chromosome before and after a duplication event Gene duplication occurs when an error in homologous recombination, a retrotransposition event, or duplication of an entire chromosome leads to the duplication of a region of DNA containing a gene [1]. The significance of this process for... The salivary glands produce saliva, which keeps the mouth and other parts of the digestive system moist. ...


Among snake families traditionally classified as venomous, the capacity seems to have evolved to extremes more than once by parallel evolution; 'non-venomous' snake lineages have either lost the ability to produce venom (but may still have lingering venom pseudogenes) or actually do produce venom in small quantities (e.g. 'toxic saliva'), likely sufficient to assist in small prey capture, but not normally cause harm to humans if bitten. Bee hovering in flight In evolutionary biology, parallel evolution refers to the independent evolution of similar traits in closely related lineages of species, while convergent evolution refers to the appearance of striking similarities among lineages of organisms only very distantly related. ... A pseudogene is a nucleotide sequences that is similar to a normal gene, but is not expressed as a functional protein. ...


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.[1] Previously known venomous squamates have already provided the basis for medications such as Ancrod, Captopril, Eptifibatide, Exenatide and Tirofiban. A treasure-trove is gold, silver, gems, money, jewellery, etc found hidden under ground or in cellar or attics, etc. ... Pharmacology (in Greek: pharmacon is drug, and logos is science) is the study of how chemical substances interfere with living systems. ... A sphygmomanometer, a device used for measuring arterial pressure. ... This article does not cite any references or sources. ... // Basic Chemical, Pharmacological, and Marketing Information Ancrod (also known under its former brand name Arwin® and recently Viprinex®) is an anticoagulant with a triple mode of action. ... Captopril is an Angiotensin-Converting Enzyme inhibitor (ACE inhibitor) used for the treatment of hypertension and some types of chronic heart failure. ... Eptifibatide (Integrilin®, Millennium Pharmaceuticals, also co-promoted by Schering-Plough/Essex), is an anti-coagulant that selectively blocks the platelet glycoprotein IIb/IIIa receptor. ... Exenatide (also Exendin-4, marketed as Byetta) is the first of a new class of medications approved for the treatment of type 2 diabetes. ... Tirofiban (INN, trade name Aggrastat®) is an anticoagulant drug. ...


References

  1. ^ a b c d e f Fry, B. et al (February 2006). "Early evolution of the venom system in lizards and snakes" (PDF). Nature 439: 584–588. doi:10.1038/nature04328. 
  2. ^ a b Fry, B. et al (July 2003). "Molecular Evolution and Phylogeny of Elapid Snake Venom Three-Finger Toxins" (PDF). Journal of Molecular Evolution 57 (1): 110–129. doi:10.1007/s00239-003-2461-2. 
  3. ^ a b Fry, B. et al (October 2003). "Isolation of a Neurotoxin (α-colubritoxin) from a Nonvenomous Colubrid: Evidence for Early Origin of Venom in Snakes" (PDF). Journal of Molecular Evolution 57 (4): 446–452. doi:10.1007/s00239-003-2497-3. 
  4. ^ Fry, B. and Wüster, W. (May 2004). "Assembling an Arsenal: Origin and Evolution of the Snake Venom Proteome Inferred from Phylogenetic Analysis of Toxin Sequences" (PDF). Molecular Biology and Evolution 21 (5): 870–883. doi:10.1093/molbev/msh091. 
  5. ^ Venom Hunt Finds 'Harmless' Snakes A Potential Danger December 16, 2003
  6. ^ Vidal, N. and Hedges, S. (October-November 2005). "The phylogeny of squamate reptiles (lizards, snakes, and amphisbaenians) inferred from nine nuclear protein-coding genes" (PDF). Comptes Rendus Biologies 328 (10-11): 1000–1008. doi:10.1016/j.crvi.2005.10.001. 

A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ...

External links


  Results from FactBites:
 
Ticuna Indians (770 words)
They live by hunting and fishing, and the preparation and sale of the curari poison, here call from them the "Ticuna" poison, for use upon blow-gun arrows.
In this manufacture they are recognized experts and hold the process a secret, although it is known the Strychnos castelneana and Cocculus toxicofera are among the ingredients.
The poison is kept in cane tubes or clay pots of their making, and is the chief object of intertribal trade throughout the upper Amazon region.
Toxicofera Toxicology (414 words)
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.
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.
  More results at FactBites »

 
 

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