A Critique of the Toxicoferan Hypothesis

  • Adam D. Hargreaves
  • Abigail S. Tucker
  • John F. Mulley
Living reference work entry
Part of the Toxinology book series (TOXI)


Historically, venom was believed to have evolved twice independently in squamate reptiles, once in the advanced snakes and once in venomous lizards. The presence of putative toxin proteins in the saliva of species usually regarded as non-venomous, and the expression of venom gene homologs in their salivary glands, led to the hypothesis that venom evolved a single time in reptiles. As the single, early origin of venom is synonymous with the Toxicofera clade (Serpentes, Anguimorpha and Iguania), it will subsequently be referred to as the Toxicofera hypothesis. This hypothesis has proved to be remarkably pervasive for almost a decade, but has until recently never been tested. Here, evidence used in support of the Toxicofera hypothesis is reviewed and critically evaluated. Taking into account both new and old data, it appears that this hypothesis is unsupported, and should be subject to further scrutiny and discussion. Finally, the implications of the rejection of the Toxicofera hypothesis are discussed, with respect to the knowledge of venom evolution in the Reptilia and also the practical implications of this knowledge.


Toxicofera Reptiles Venom Oral glands Venom glands 


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Copyright information

© Springer Science+Business Media Dordrecht 2015

Authors and Affiliations

  • Adam D. Hargreaves
    • 1
  • Abigail S. Tucker
    • 2
  • John F. Mulley
    • 3
  1. 1.Department of ZoologyUniversity of OxfordOxfordUK
  2. 2.Department of Craniofacial Development and Stem Cell BiologyKing’s College London, Guy’s HospitalLondonUK
  3. 3.School of Biological SciencesBangor UniversityBangorUK

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