Megalania (Varanus priscus, formerly Megalania Prisca) was a giant monitor lizard that lived on the Australian continent.
Fossil records suggest the species went extinct about 40,000-50,000 years ago, during the Pleistocene epoch (c. 2.6 million-11,700 years).
Based on current estimates of an average body length of 18-23 feet and weight of 580-2,000kg (1,280-4,400lbs), paleobiologists consider Megalania the largest ever terrestrial lizard in the order Squamata.
Megalania is similar to the modern-day Komodo dragon (Varanus komodoensis). Thus, one may picture it as an oversized version of the Komodo dragon.
Research suggests that the first humans arrived on the Australian continent (then part of the Sahul landmass) about 50,000 years ago.
Thus, the first Australians (or Sahulians) might have shared the continent with Megalania and contributed to its extinction.
[Note: When humans arrived in Australia about 50,000 years ago, it was part of the paleocontinent landmass known as Sahul (also Meganesia or Greater Australia). Sahul included modern-day Australia, Tasmania, New Guinea, and the Aru Islands.]
Megalania was a giant monitor lizard
Megalania was a giant monitor lizard that belonged to the same genus as extant monitor lizards (genus Varanus).
Paleontologists obtained the first fossil remains of Megalania in the mid-19th century. The British paleontologist Sir Richard Owen first described the species based on vertebrae discovered in Australia.
Owen assigned the species to the genus Megalania (“giant wanderer”) and dubbed it Megalania prisca. But subsequent researchers realized the species was more closely related to extant species of monitor lizards. Thus, they reclassified it as a member of the genus Varanus.
However, Megalania remains the species’ common (non-scientific) name.
Members of the genus Varanus are known collectively as varanids (family Varanidae).
Several species of monitor lizards live in Africa, Asia, and Australasia.
Australia alone has more than 25 living species. Australians call monitor lizards goannas. The largest living goanna in Australia is the perentie (Varanus giganteus). It may reach lengths of more than 8 feet.
The genus is represented in West Africa by the West African Nile monitor (Varanus niloticus stellatus), a subspecies of the more widely distributed Nile monitor (Varanus niloticus).
The best-known representative of the genus in Asia is the Komodo dragon (Varanus komodoensis), native to the Indonesian islands of Komodo (from which it takes its name), Gili Motang, Flores, and Rinca,
The Komodo dragon is the largest extant member of the genus, reaching lengths of nearly 10 feet and weighing up to 70 kg.
Megalania was similar to the Komodo dragon
Megalania (Varanus priscus) was a giant monitor lizard similar to the Komodo dragon but larger.
Paleontologists haven’t found enough fossil remains of Megalania to construct a complete picture of what it looked like or how big it was. However, they have tried to use the available fossil evidence to estimate the creature’s dimensions, body weight, and appearance.
Researchers estimate that Megalania was about the size of modern-day saltwater crocodiles (Crocodylus porosus). Male saltwater crocodiles range in length from 15 feet to 23 feet.
Megalania individuals may have reached lengths of up to 23 feet and weighed up to nearly 2,000 kgs (4,400 lbs), according to some experts. However, other researchers proposed a more conservative estimate of about 18 feet and a weight of about 580kg.
Based on the estimates, paleobiologists consider Megalania as the largest ever squamate lizard
[Note: Dinosaurs were not squamate lizards (order Squamata). They were reptiles of the clade Dinosauria.]
Megalania had a heavily built body, with large jaws containing sharp serrated (saw-like) teeth. It had sturdy limbs that made it sufficiently agile on land. They were also likely good swimmers.
It lived in forests, dense woods, grasslands, and possibly along river banks in the north, south, and east of Australia during the Pleistocene.
Biologists rank the species among ancient Australia’s apex megafauna predators alongside the marsupial lion (Thylacoleo carnifex) and Quinkana (Quinkana sp.), another extinct genus of crocodylian monsters that terrorized Australia in the Pleistocene epoch, about 50,000 years ago.
Megalania preyed on medium-sized animals such as deer, wild pigs, and goats. It also likely preyed on larger animals, such as the extinct marsupial Diprotodon (D. optatum) and Procoptodon (the giant short-faced kangaroo).
Megalania’s size may have contributed to its eventual extinction because it required large prey to sustain it. Thus, scarcity due to human and climactic factors around 40,000 years ago made it vulnerable to extinction.
Sightings and Tales
Was Megalania the whowie?
Humans might have hunted Megalania. However, when the first settlers arrived in Sahul, Australia had such diverse fauna that it was unlikely they needed the reptile for food.
Although they were large and fierce creatures, they weren’t sufficiently agile on land. Thus, early human hunters armed with crude but deadly weapons would have found them easy prey.
Some folklorists speculated that confrontations between early Australians and the Megalania may have inspired aboriginal folktales about the legendary whowie.
The whowie was a cryptid in aboriginal folklore identified as a giant monitor lizard (goanna). The natives said the legendary monster was about 23 feet long. It had a frog-like head and six legs.
According to the legends, it lived in a cave (allegedly the Punyelroo Cave) along the Murray River in South Australia and prowled the banks looking for prey.
The whowie had such a big appetite that it could at once swallow several humans.
Its predatory ways proved a nuisance to its human neighbors. So they teamed up to kill it. They used dried sticks to light a fire at the mouth of the whowie’s cave to smoke it out. When the beast emerged, they attacked it with spears and arrows and killed it.
Was Megalania venomous?
Some researchers proposed in 2009 that Megalania may have possessed glands in its mouth that produced venom that helped it kill prey.
The proposal that Megalania may have been a venomous reptile derived inspiration from the results of research that showed that some lizards of the genus Varanus, such as the lace monitor (Varanus varius), Komodo dragon, and the Nile monitor, have oral glands that secrete venomous substances.
Other lizards of the order Squamata, such as the Gila Monster (Heloderma suspectum) native to the U.S. and Mexico, are also venomous.
Australian researchers from the University of Melbourne (Fry et al. 2009) reported they discovered glands in the Komodo dragon’s lower jaws that produced toxic proteins. The toxins prevented blood clotting (anticoagulation) and caused vasodilation (relaxation of blood vessel walls).
The researchers claimed that the Komodo dragon’s venom speeds up death by causing profuse bleeding due to its anticoagulant effects. Profuse bleeding and vasodilation lead to a rapid drop in blood pressure, muscle paralysis, and systemic shock.
The scientists also proposed that the Australian monitor lizard perentie (Varanus giganteus) produced venom that reduced blood clotting and caused local swelling and pain.
They then suggested that the extinct Megalania may also have used venom to kill prey.
However, the suggestion that lizards used venom to kill prey proved controversial. Experts, such as Kurt Schwenk, University of Connecticut evolutionary biologist, contested the claim.
Schwenk argued that the Komodo dragon’s venom might play a different role besides envenomating prey.
Biologists had previously believed that the Komodo dragon’s saliva contained toxic bacteria that quickened death by inducing sepsis (blood poisoning).
Dragons in the Dust: The Paleobiology of the Giant Monitor Lizard Megalania by Ralph E. Molnar (2004).
Myths and Legends of the Australian Aborigines by W. Ramsay Smith (1970).
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https://web.archive.org/web/20090606045519/http://www3.signonsandiego.com/stories/2009/may/25/1c25komodo183628-venom-may-be-boost-dragons-bite/?uniontrib, “Venom might boost dragon’s bite,” accessed on March 31, 2023.
https://www.bushheritage.org.au/species/goannas, “Goannas (Monitor Lizards),” accessed on March 31, 2023.
https://ecoevocommunity.nature.com/posts/61740-megafauna-extinction, “Life and death in tropical Australia, 40,000 years ago,” accessed on March 31, 2023.
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