Among extant reptiles only two lineages are known to have evolved venom delivery systems, the advanced snakes and helodermatid lizards (Gila Monster and Beaded Lizard)1. Evolution of the venom system is thought to underlie the impressive radiation of the advanced snakes (2,500 of 3,000 snake species)2,3,4,5. In contrast, the lizard venom system is thought to be restricted to just two species and to have evolved independently from the snake venom system1. Here we report the presence of venom toxins in two additional lizard lineages (Monitor Lizards and Iguania) and show that all lineages possessing toxin-secreting oral glands form a clade, demonstrating a single early origin of the venom system in lizards and snakes. Construction of gland complementary-DNA libraries and phylogenetic analysis of transcripts revealed that nine toxin types are shared between lizards and snakes. Toxinological analyses of venom components from the Lace Monitor Varanus varius showed potent effects on blood pressure and clotting ability, bioactivities associated with a rapid loss of consciousness and extensive bleeding in prey. The iguanian lizard Pogona barbata retains characteristics of the ancestral venom system, namely serial, lobular non-compound venom-secreting glands on both the upper and lower jaws, whereas the advanced snakes and anguimorph lizards (including Monitor Lizards, Gila Monster and Beaded Lizard) have more derived venom systems characterized by the loss of the mandibular (lower) or maxillary (upper) glands. Demonstration that the snakes, iguanians and anguimorphs form a single clade provides overwhelming support for a single, early origin of the venom system in lizards and snakes. These results provide new insights into the evolution of the venom system in squamate reptiles and open new avenues for biomedical research and drug design using hitherto unexplored venom proteins.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1.

    in Biology of the Reptilia Vol 8 (eds Gans, S. K. & Gans, C.) 43–162 (Academic, London, 1978)

  2. 2.

    Colubroid systematics: evidence for an early appearance of the venom apparatus followed by extensive evolutionary tinkering. J. Toxicol. Toxin Rev. 21, 21–41 (2002)

  3. 3.

    & Higher-level relationships of caenophidian snakes inferred from four nuclear and mitochondrial genes. C. R. Biol. 325, 987–995 (2002)

  4. 4.

    et al. Isolation of a neurotoxin (alpha-colubritoxin) from a ‘non-venomous’ colubrid: evidence for early origin of venom in snakes. J. Mol. Evol. 57, 446–452 (2003)

  5. 5.

    et al. LC/MS (liquid chromatography, mass spectrometry) analysis of Colubroidea snake venoms: evolutionary and toxinological implications. Rapid Commun. Mass Spectrom. 17, 2047–2062 (2003)

  6. 6.

    Development of the venom gland and trigeminal muscles in Vipera palaestinae. Acta Anat. 52, 49–89 (1963)

  7. 7.

    The development of the venom gland in the opisthoglyph snake Telescopus fallax with remarks on Thamnophis sirtalis (Colubridae, Reptilia). Copeia 2, 147–154 (1965)

  8. 8.

    The origin of snakes and evolution of the venom apparatus. Toxicon 25, 65–106 (1987)

  9. 9.

    Atractaspis (Serpentes, Atractaspididae) the Burrowing Asp; a multidisciplinary minireview. Bull. Nat. Hist. Mus. Lond. Zool. 68, 91–99 (2002)

  10. 10.

    & On the affinities of the burrowing asps Atractaspis (Serpentes: Atractaspididae). Zool. J. Linn. Soc. 107, 3–64 (1993)

  11. 11.

    in Venomous Snakes: Ecology, Evolution and Snakebite (eds Thorpe, R. S., Wüster, W. & Malhotra, A.) 1–13 (Symp. Zool. Soc. Lond. no. 70, Clarendon, Oxford, 1997)

  12. 12.

    The evolution of venom-delivery systems in snakes. Zool. J. Linn. Soc. 137, 337–354 (2003)

  13. 13.

    & Assembling an arsenal: Origin and evolution of the snake venom proteome inferred from phylogenetic analysis of toxin sequences. Mol. Biol. Evol. 21, 870–883 (2004)

  14. 14.

    & Molecular evidence for a terrestrial origin of snakes. Proc. R. Soc. Lond. B Suppl. 271, S226–S229 (2004)

  15. 15.

    , , & Molecular phylogenetics of Squamata: The position of snakes, Amphisbaenians, and Dibamids, and the root of the squamate tree. Syst. Biol. 53, 735–757 (2004)

  16. 16.

    & Données histologiques sur les glandes salivaires des lépidosauriens. Mém. Mus. Natl Hist. Nat. Paris 58, 1–118 (1969)

  17. 17.

    & in Toxins of Animal and Plant Origin (eds de Vries, A. & Kochva, E.) 65–68 (Gordon & Breach, London, 1971)

  18. 18.

    Entwicklung, Bau und Funktion der Giftdruse (Duvernoy's gland) von Natrix tessellata. Acta Trop. Zool. 28, 225–274 (1971)

  19. 19.

    From genome to ‘venome’: Molecular origin and evolution of the snake venom proteome inferred from phylogenetic analysis of toxin sequences and related body proteins. Genome Res. 15, 403–420 (2005)

  20. 20.

    et al. Molecular evolution of elapid snake venom three finger toxins. J. Mol. Evol. 57, 110–129 (2003)

  21. 21.

    & Effect on human platelet aggregation of phospholipase A2 purified from Heloderma horridum (beaded lizard) venom. Biochim. Biophys. Acta 1211, 61–68 (1994)

  22. 22.

    et al. Electrospray liquid chromatography/mass spectrometry fingerprinting of Acanthophis (death adder) venoms: taxonomic and toxinological implications. Rapid Commun. Mass Spectrom. 16, 600–608 (2002)

  23. 23.

    et al. Novel natriuretic peptides from the venom of the inland taipan (Oxyuranus microlepidotus): Isolation, chemical and biological characterization. Biochem. Biophys. Res. Commun. 327, 1011–1015 (2005)

  24. 24.

    , , & A case of intoxication by a bite of the gray monitor (Varanus griseus). Izv. Akad. Nauk Turkm. SSR. Ser. Biol. Nauk 87, 78 (1987)

  25. 25.

    About the toxicity of the saliva of the gray monitor. Izv. Akad. Nauk Turkm. SSR. Ser. Biol. Nauk 71, 74 (1971)

  26. 26.

    , & The evolution of Helodermatid squamates, with description of a new taxon and an overview of Varanoidea. Trans. San Diego Soc. Nat. Hist. 21, 167–202 (1986)

  27. 27.

    , & Estesia mongoliensis, a new fossil varanoid from the Late Cretaceous Barun Goyot Formation of Mongolia. Am. Mus. Novit. 3045, 1–24 (1992)

  28. 28.

    At the feet of the dinosaurs: the origin, evolution and early diversification of squamate reptiles (Lepidosauria: Diapsida). Biol. Rev. Cambr. 78, 513–551 (2003)

  29. 29.

    & SWISS-MODEL and the Swiss-PdbViewer: an environment for comparative protein modeling. Electrophoresis 18, 2714–2723 (1997)

  30. 30.

    , & MOLMOL: a program for display and analysis of macromolecular structures. J. Mol. Graph. 14(1M), 51–55 (1996)

Download references


We thank the following persons and institutions who helped us or contributed tissue samples used in this study: A. Fry, Alice Springs Reptile Centre, Australian Reptile Park, M. A. G. de Bakker, R. L. Bezy, B. Branch, J. Campbell, N. Clemann, C. Clemente, C. Cicero, K. Daoues, A. S. Delmas, B. Demeter, J. Haberfield, A. Hassanin, Healesville Sanctuary, M. Hird, Louisiana State University Museum of Zoology, P. Moler, T. Moncuit, P. Moret, National Museum of Natural History Naturalis Leiden (J. W. Arntzen), T. Pappenfus, J.-C. Rage, C. Skliris, J. Smith, S. Sweet, Ultimate Reptiles (South Australia), University of California Museum of Vertebrate Zoology (Berkeley), J. Walker, R. Waters, J. Weigel and B. Wilson. We also thank A. Webb and T. Purcell for providing HPLC access; N. Williamson for help with preliminary mass spectrometry characterization; E. V. Grishin for help in obtaining the references in Russian; S. Edwards for comments; and T. van Wagner and V. Wexler for artwork. This work was funded by the Service de Systématique moléculaire of the Muséum National d'Histoire Naturelle, Institut de Systématique (N.V.) and by grants from the Australian Academy of Science (B.G.F.), Australian Geographic Society (B.G.F.), Australia & Pacific Science Foundation (B.G.F.), Australian Research Council (B.G.F.), CASS Foundation (B.G.F.), Commonwealth of Australia Department of Health and Aging (B.G.F.), Ian Potter Foundation (B.G.F.), International Human Frontiers Science Program Organisation (B.G.F.), Leiden University (F.J.V., M.K.R.), NASA Astrobiology Institute (S.B.H.), National Science Foundation (S.B.H.) and University of Melbourne (B.G.F.). We thank the relevant wildlife departments for granting the scientific permits for field collection of required specimens.

Author information


  1. Australian Venom Research Unit, Level 8, School of Medicine, University of Melbourne, Parkville, Victoria 3010, Australia

    • Bryan G. Fry
    •  & S. F. Ryan Ramjan
  2. Population and Evolutionary Genetics Unit, Museum Victoria, GPO Box 666E, Melbourne, Victoria 3001, Australia

    • Bryan G. Fry
    •  & Janette A. Norman
  3. Department of Biology and Astrobiology Research Center, 208 Mueller Lab, Pennsylvania State University, University Park, Pennsylvania 16802-5301, USA

    • Nicolas Vidal
    •  & S. Blair Hedges
  4. UMS 602, Taxonomie et collections, Reptiles-Amphibiens, Département Systématique et Évolution, Muséum National d'Histoire Naturelle, 25 Rue Cuvier, Paris 75005, France

    • Nicolas Vidal
  5. Institute of Biology, Leiden University, Kaiserstraat 63, PO Box 9516, 2300 RA, Leiden, The Netherlands

    • Freek J. Vonk
    •  & Michael K. Richardson
  6. Department of Structural Biology and Bioinformatics, University of Geneva and Swiss Institute of Bioinformatics, Centre Médical Universitaire, 1 Rue Michel-Servet, 1211 Geneva 4, Switzerland

    • Holger Scheib
  7. SBC Lab AG, Seebüelstrasse 26, 8185 Winkel, Switzerland

    • Holger Scheib
  8. Monash Venom Group, Department of Pharmacology, Monash University, Clayton, Victoria 3800, Australia

    • Sanjaya Kuruppu
    •  & Wayne. C. Hodgson
  9. Molecular and Health Technologies, CSIRO, 343 Royal Parade, Parkville, Victoria 3010, Australia

    • Kim Fung
  10. Department of Pathology, University of Melbourne, Parkville, Victoria 3010, Australia

    • Vera Ignjatovic
    •  & Robyn Summerhayes
  11. Murdoch Children's Research Institute, Royal Children's Hospital, Flemington Road, Parkville, Victoria 3052, Australia

    • Vera Ignjatovic
    •  & Robyn Summerhayes
  12. Department of Zoology, Tel Aviv University, Tel Aviv 69978, Israel

    • Elazar Kochva


  1. Search for Bryan G. Fry in:

  2. Search for Nicolas Vidal in:

  3. Search for Janette A. Norman in:

  4. Search for Freek J. Vonk in:

  5. Search for Holger Scheib in:

  6. Search for S. F. Ryan Ramjan in:

  7. Search for Sanjaya Kuruppu in:

  8. Search for Kim Fung in:

  9. Search for S. Blair Hedges in:

  10. Search for Michael K. Richardson in:

  11. Search for Wayne. C. Hodgson in:

  12. Search for Vera Ignjatovic in:

  13. Search for Robyn Summerhayes in:

  14. Search for Elazar Kochva in:

Competing interests

The sequences of the cDNA clones have been deposited in GenBank (accession numbers DQ139877–DQ139931 and DQ184481), as have the nuclear gene sequences (DQ119594–DQ119641). Reprints and permissions information is available at The authors declare no competing financial interests.

Corresponding author

Correspondence to Bryan G. Fry.

Supplementary information

PDF files

  1. 1.

    Supplementary Figures

    This file contains 13 Supplementary Figures, including the molecular phylogenetic analysis of squamate nuclear genes, the phylogenetic analyses and sequence alignments of the toxin types analysed in this study as well as the liquid chromatography-mass spectrometry analysis of Varanus varius (Lace monitor) venom.

Word documents

  1. 1.

    Supplementary Methods

    This file contains detailed descriptions of materials and methods not already described in the main article.

About this article

Publication history





Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.