Komodo

 The Dragon’s Paradise Lost: Komodo Dragons Most Likely Evolved In Australia, Dispersed To Indonesia
OCTOBER 11, 2009

by publicanthropology


The Komodo Dragon is the world’s largest lizard, growing to an average length of 2 to 3 meters. It is

found almost entirely on the Indonesian islands of Rinca, Flores and Komodo. (Credit: iStockphoto/Alan

Tobey

ScienceDaily (Oct. 1, 2009) — The world’s largest living lizard species, the Komodo dragon (Varanus

komodoensis), is vulnerable to extinction and yet little is known about its natural history. New research

by a team of palaeontologists and archaeologists from Australia, Malaysia and Indonesia, who studied

fossil evidence from Australia, Timor, Flores, Java and India, shows that Komodo Dragons most likely

evolved in Australia and dispersed westward to Indonesia.

The research, which also details new fossil specimens indicating the presence of a new species of giant

varanid found on the island of Timor, is published September 30 in the open-access, peer-reviewed journal

PLoS ONE.

Author Scott Hocknull, Senior Curator of Geosciences at the Queensland Museum, said Australia is a hub

for lizard evolution.

“The fossil record shows that over the last four million years Australia has been home to the world’s

largest lizards, including a five metre giant called Megalania (Varanus prisca),” Mr Hocknull said.

“Now we can say Australia was also the birthplace of the three-metre Komodo dragon (Varanus komodoensis),

dispelling the long-held scientific hypothesis that it evolved from a smaller ancestor in isolation on

the Indonesian islands.

“Over the past three years, we’ve unearthed numerous fossils from eastern Australia dated from 300,000

years ago to approximately four million years ago that we now know to be the Komodo dragon.

“When we compared these fossils to the bones of present-day Komodo dragons, they were identical,” he

said.

The varanids are a group of giant monitor lizards, which are the world’s largest terrestrial lizards and

which were ubiquitous in Australasia for over 3.8 million years, having evolved alongside large-bodied,

mammalian carnivores, such as Thylacoleo, the ‘marsupial lion’. Growing to 2-3 metres in length and

weighing around 70 kilos, the Komodo dragon is the last of the truly giant monitor lizards. New fossil

discoveries show that the ancestor of the Komodo dragon evolved on mainland Australia, around 3-4 million

years ago and then dispersed west to Indonesia. Historically, Australia was home to many other giant

monitor lizards, including Megalania (Varanus prisca)—once the world’s largest terrestrial lizard but

which died out around 40,000 years ago.

“This research also confirms that both giant lizards, Megalania (Varanus priscus) and the Komodo dragon

(Varanus komodoensis) existed in Australia at the same time,” Mr Hocknull said.

Scott Hocknull and his international team have compared fossil evidence of Komodo dragons and other giant

varanids in order to reconstruct the palaeobiogeography of the world’s largest land-based lizards. The

researchers hope this will have implications for the conservation of the Komodo dragon, which is now

found on just a few isolated islands in eastern Indonesia, between Java and Australia, and vulnerable to

extinction, probably due to habitat loss and persecution by modern humans over the last few millennia.

It was previously thought that the Komodo Dragon evolved its large size as a response to insular island

processes, lack of carnivore competition, or as a specialist hunter of pygmy elephants called Stegodon.

However, Hocknull and colleagues report that the ancestor of the Komodo dragon most likely evolved in

Australia and spread westward, reaching the Indonesian island of Flores by 900,000 years ago. Comparisons

between fossils and living Komodo dragons on Flores show that the lizard’s body size has remained

relatively stable since then—a period marked by the extinction of the island’s megafauna, the arrival of

early hominids by 880,000 years ago, and the arrival of modern humans by 10,000 years ago. Within the

last 2,000 years, however, their populations have contracted severely.

Further support for the theory that the giant varanids dispersed to Indonesia from Australia comes from

the island of Timor, located between Australia and Flores. Three fossil specimens from Timor represent a

new (unnamed) species of giant monitor lizard, which was larger than the Komodo dragon (although smaller

than Megalania). More specimens of this new Timor-Australian giant lizard are needed before the species

can be formally described.

Journal reference:

Hocknull SA, Piper PJ, van den Bergh GD, Due RA, Morwood MJ, et al. Dragon’s Paradise Lost:

Palaeobiogeography, Evolution and Extinction of the Largest-Ever Terrestrial Lizards (Varanidae). PLoS