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Rediscovering
hilangnya naga
Paradise : Komodo Dragon kemungkinan berkembang di Australia, yang tersebar ke
Indonesia
Rediscovering The Dragon's Paradise Lost: Komodo Dragons Most Likely
Evolved In Australia, Dispersed To Indonesia
Date:
October 1,
2009
Source:
Public Library of Science
Summary:
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 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.
Story
Source:
The above
story is based on materials provided by Public Library of Science. Note: Materials may be edited
for content and length.
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 ONE, 2009; 4(9): e7241 DOI: 10.1371/journal.pone.0007241