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Megalania prisca

Megalania prisca is the largest lizard to have walked this earth and it came from Australia. It existed between 26,000 to 19000 years ago during the Pleistocene (Pianka, 1995). It could reach lengths double that of the extant Komodo Dragon, Varanus komodoensis, approximately 4.5-5.5 m with some estimates exceeding 7 m. Weighing as much as 600 kg, these lizards had curved teeth 2 cm long with a rear serrated edge used for cutting and tearing flesh (Pianka, 1995). Monitor lizards will hunt by chasing prey with attributes that include speed and stamina. On comparison with V. komodoensis, there is a possibility that M. prisca (closely related to V. komodoensis), could have used the same technique to kill prey as Komodo dragons do today: ‘anticoagulant and hypotension-inducing venom’ (Fry et al., 2009).

This species of monitor lizard ‘achieved gigantism by sustaining juvenile growth rates for a longer period and delaying the onset of somatic adulthood’ (Erickson et al., 2003). For the first 13 years of life of the specimen studied by Erickson et al., 2009, the growth rate was 14 cm/year. This then decreased to 10 cm/year in the last 2 years of its life. By delaying maturation to become large in size, this allowed it to feast upon the large megafauna, such as giant kangaroos, that it existed alongside.

Figure 1: 5.5m skeletal mount of Megalania prisca at Queensland Musuem, Brisbane, Australia. The top right hand image shows vermiform bones from the skin of the extant monitor lizard Varanus Salvator in comparison to a dermal ossicle from Megalania prisca (bottom right). Note that the ossicle is incomplete due to fracturing during diagenesis. Sourced from Erickson et al. (2003).

References and Resources

  • Erickson, G.M. et al.. 2003. Vermiform bones and the evolution of gigantism in Megalania – How a reptilian fox became a lion. Journal of Vertebrate Paleontology. 23, 966-970.
  • Fry, B.G. et al.. 2009. A central role for venom in Varanus komodoensis (Komodo dragon) and the extinct giant Varanus (Megalania) prisca. PNAS. 106, 8969-8974.
  • Pianka, E.R. 1995. Evolution of body size: Varanid lizards as a model system. The American Naturalist. 146, 398-414.

  • Authored by Emma Kerridge & Chris Rogers

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