 |
Scientific News  Hypotheses Historical hypotheses EXTINCT REPTILE SPECIES LIVED ON IN AUSTRALIA
EXTINCT REPTILE SPECIES
LIVED ON IN AUSTRALIA
|
|
|
A restoration of the dicynodont by Mr
Laurie Beirne (the beast would have been about 2 m long). |
An ancient hippo-like reptile, extinct elsewhere,
existed in Australia for another 110 million years – alongside the
dinosaurs that wiped them out in other places, palaeontologists have found.
The clumsy animals with a turtle beak and tusks, known as dicynodonts, were
thought to have gone extinct when the dinosaurs turned up. But an Australian
husband and wife team argue that dicynodonts existed well into the age of the
dinosaurs – at least in a small enclave in the northern Australian state of
Queensland.
In this week’s issue of Proceedings
of The Royal Society of London, Dr Tony Thulborn and Dr Susan Turner,
honorary associates at Monash
University in Melbourne, document part of what they say would have been a 40 cm
skull of a dicynodont – a group of mammal-like reptiles named after their
single pair of dog-like canine teeth.
“We thought dicynodonts lived for 60 million years but really they lived
for nearly three times that long,” Thulborn told ABC Science Online.
Dicynodonts were the first common terrestrial plant eaters and dominated the
world’s landscape before the rise of the dinosaurs. They spread worldwide and
to date were believed to have lived for 60 million years before declining
to extinction around 223 million years ago in the Late Triassic – around
the time when dinosaurs came into prominence.
|
|
|
The most significant piece of fossil
evidence – a fragment of the upper jaw bone about 10 cm across.
Note the stump of the tusk projecting downwards; the tip of the snout
would have been to the left. Researchers estimate the whole skull would
have been about 40 cm long. |
What most amazed Thulborn and Turner was that
these fossils had been found in Cretaceous rocks that were only 105 million
years old – which means dicynodonts lived through the age of the
dinosaurs.
“During the age of dinosaurs, if you ran into a big land animal it was a
dinosaur," said Thulborn. “But not in Queensland. If you bumped into a
big animal there it might have been a dicynodont. It was the only place in the
world where the dinosaurs didn’t rule.”
“It’s only in this really remote corner of Gondwana that they seem to have
lingered on. They hung on for at least another 110 million years longer
than we thought.”
Thulborn described dicynodonts as an example of a “Lazarus taxon – risen
from the dead”. He said another example of this was Latimeria, a
coelacanth fish, which was supposed to have been extinct for 65 million
years until a living specimen was found off South Africa in the 1930s.
“The dicynodont is the mother of Lazarus taxa," said Thulborn, adding the
discovery was "as surprising as finding a Pteradactyl squawking around in
your back garden."
Thulborn reported the first and only other fossil of an Australian dicynodont in
Nature during the 1980s. This previous specimen was from the Early
Triassic and in keeping with previous dicynodont records.
The recently identified Cretaceous dicynodont fossil had actually been sitting
in the Queensland Museum for 90 years after being excavated near the town of
Hughenden in central Queensland. Previous assistant director of the Museum,
Heber Albert Longman, had the ‘feeling’ it might be a dicynodont but
wasn’t sure.
“It’s only an accident of history that Longman wasn’t the person to
announce the discovery of a Cretaceous dicynodont,” said Thulborn.
Source of the given news and the copyrights
belong to a ABC
Online News
Publishing date: April 2, 2003
Back
|  |
