The dragon down under

Not so long ago an enormous lizard dragged it claws through the dried, dead leaves deep in the Australian woodlands. Longer than a black cab, this was the largest lizard (so far discovered) ever to walk on land. Its teeth were around 2 inches long, curved back, and as sharp (and as big) as steak knives.

Fossils of this enormous lizard were first discovered in 1859 on the beautiful farmlands of Darling Downs, Queensland in Eastern Australia.  Named by the great Victorian scientist, Richard Owen (is there a beast he didn’t name?), the creature was called Megalania prisca which translates as the ‘roaming lizard’. Today the name of this giant should belong in the same Genus as monitor lizards, like the infamous Komodo Dragon, so should be called Varanus priscus. Both genus names are accepted, although Varanus is preferred. Megalania is accepted as the common name. Taxonomists can be a pernickety bunch sometimes.

A classic photo of a reconstructed skeleton of Varanus priscus at the Melbourne Museum, Australia. (Image from here)

This terrifying lizard is only known from a few scattered remains. Skull fragments, teeth, a few arm and leg bones, and vertebrae have been found at several sites across Eastern and Southern Australia. No complete skeleton has yet been found. Isolated fossils have been found in old stream and river bed sediment, and in cave sites: but these were not their natural habitats, the bones ended up there after falling into water or carcases being scavenged and dragged into caves. It is more likely that Megalania trundled through open woodlands and forests.

With such fragmented fossil remains, where Megalania sits within the family of monitor lizards (Varanidae) is difficult to ascertain. These extinct lizards may be closely related to Australia’s largest living lizard, the particularly cute looking perentie; the shape of the top of the skull shares similarities. However, studies of the brain case look like it may be a sister species to the Komodo Dragon. Until more complete specimens are found, the true relationship remains contentious.

As to it’s size, we can make a fairly educated guess by comparing the fossils to skeletons of monitor lizards alive today. This was a massive lizard; bone size calculations compared to other monitor lizards to work out the percentage size difference, place this giant to be somewhere between 4.5 meters and 7 meters. Working out sizes based on a few bones can be problematic, because individuals in populations vary quite dramatically. The Megalania fossils do not represent a fantastically significant sample. However, even based on ‘smaller’ size ranges, it shows that this was one pretty big lizard.

Two possible sizes of Megalania (3A and 3B) based on the fossil bones recovered. The Komodo dragon (1) is the biggest lizard alive today. Megalania was double, almost triple its size. (Image from here)

Megalania was like a giant Komodo Dragon, and would have been a ferocious creature to see in the flesh. (Image by Jan Freedman)

This was a terrifying predator roaming Australia for almost 2 million years. For such an enormous lizard there had to be some pretty big prey around. And there most certainly was. Australia was isolated for over 40 million years since the break up of Gondwana, and the animals there evolved into some incredible forms. During the Pleistocene, the continent was home to a rich and diverse mega-fauna including giant kangaroos, Diprotodon (a kind of massive wombat), and the mihirung (a giant flightless bird). All these strange animals, and many others would have supplied ample food for Megalania. The largest lizard alive today, the Komodo Dragon, has little trouble in taking down massive prey, like water buffalo, and there is no doubt that Megalania would have tackled a Diprotodon with ease. But how could they overcome such big animals?

It was thought that Komodo Dragons had extremely bad dental hygiene resulting in deadly bacteria building up around the rotting flesh stuck to their teeth, resulting in just one bite from this animal causing a slow, and painful death. Komodo Dragons actually have venom glands in their lower jaws. Around 5 glands push venom up, inbetween the teeth; when the Dragon sinks it’s teeth into it’s prey, the venom seeps into the open flesh. It is possible, although not confirmed with fossil evidence, that the huge Megalania also had venom glands: several other species of monitor lizards have venom glands, as well as many other types of lizards. For reptiles, venom makes a lot of sense. Reptiles can move pretty fast, but only in short bursts over small distances; they lack the ability to burn enough continuous energy for a good run. If a reptile can bite and inject venom, the job of seriously wounding (or even killing) it’s prey is done. Megalania may have used this technique, along with ambushing its prey. Fossil footprints preserved at Lake Callabonna, in South Eastern Australia, show evidence of the huge marsupial Diprotodon moving in herds. Animals move in herds for safety. For such large animals like Diprotodons to be travelling in groups means they were protecting themselves from something. Something big.

Contrary to cryptozoologist claims, it appears that this enormous lizard became extinct  about 40,000 years ago. Around this time, Australia’s climate was beginning to get warmer, and drier, resulting in less forested areas. The open lands would have been too hot for such a large lizard to survive in the intense heat (smaller lizards can easily scurry into little crevices for shade). Along with the vanishing safety of the wooded areas, the large herbivores that were once at home here, and also the food for Megalania, began to decline. This extinction coincides with many other of Australia’s mega-fauna. Some animals may have survived in small refugia, pockets where little populations were safe. The arrival of a new hunter, Homo sapiens, may have been the final blow to the big herbivores. And as the prey vanished, so did the last hope for these incredible, unique reptilian giants.

Written by Jan Freedman (@JanFreedman)

Further reading:

Nice post on the Australian Museum website: http://australianmuseum.net.au/Megalania-prisca

Fry, B. G. et al., (2009), ‘A central role for venom in predation by Varanus komodoensis (Komodo Dragon) and the extinct giant Varanus (Megalania) priscus’, Proceedings of the National Academy of Science. 106. p.8969-8974. [Full text]

Hecht, M. (1975). “The morphology and relationships of the largest known terrestrial lizard, Megalania prisca Owen, from the Pleistocene of Australia”. Proceedings of the Royal Society of Victoria. 87: 239–250.

Hocknull, S. A. et al. (2008), ‘Dragons paradise lost: palaeobiogeography, evolution and extinction of the largest-ever terrestrial lizards (Varanidae)’, PLoS ONE.  4(9). E7241. [Full article]

Lee MSY (1996). “Possible affinities between Varanus giganteus and Megalania prisca“. Memoirs of the Queensland Museum. 39: 232. [Full article]

Molnar, R,  E. (2004). Dragons in the dust: the paleobiology of the giant monitor lizard Megalania. Bloomington: Indiana University Press. [Book]

Reed, E, and Hutchinson, M. N. (2005), ‘First record of giant Varnaid (Megalania, Squamata) from the Pleistocene of Naracoorte, South Australia’, Memoirs of the Queensland Journal. 51 (1), 203-213. [Full article]