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Ancestor
of all modern crocodilians discovered in outback Queensland
14 June 2006
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Isisfordia duncani
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Fossils of the world's most
primitive modern crocodilian have been discovered near the
outback town of Isisford, in central-western Queensland,
Australia.
The new animal, named Isisfordia duncani,
is described today (June 14, 2006) in the prestigious Proceedings
of the Royal Society journal by an international team of
palaeontologists, headed by Dr Steve Salisbury from The
University of Queensland's (UQ) School of Integrative Biology.
“These are the most complete crocodilian fossils
yet discovered in Australia, and provide us with valuable new
insights into the early evolution of today's crocodilians and
their lifestyle as semi-aquatic ambush predators,” Dr
Salisbury said.
“What's more, their discovery in
Queensland suggests that the ancestor of all living crocodilians
was Australian.”
Dr Salisbury said it had been a
long-standing mystery as to where and when the immediate
ancestors of modern-day crocodilians – crocodiles,
alligators and gharials – originated.
“The
appearance of Isisfordia signaled the dawn of crocodilians
as we know them today,” he said.
“Living
98-95 million years ago, Isisfordia predates the first recorded
appearance of alligators and gharials by almost 20 million years,
and the first true crocodiles by over 30 million.
“The
discovery of Isisfordia in Australia indicates that the
precursors to all three groups of modern crocodilians may have
originated in Gondwana, rather than Europe or North America, as
was previously thought.”
Dr Salisbury said
Isisfordia was small compared with the majority of its
modern descendants and looked like a dwarf version of the
American alligator, but with a much flatter and longer snout.
“Adults appear to have been just over a meter in
length, and probably weighed no more than about three kilograms,”
he said.
“It may only have been small by today's
standards, but it represents a very important phase in the
evolutionary history of crocodilians.”
Discovered
by former Deputy Mayor of Isisford, Ian Duncan, after whom the
new species has been named, the first fossils of Isisfordia
were found in the mid-1990s in a dried-up creek bed on the
outskirts of town.
Initial preparation of the fossils was
undertaken at the Queensland Museum, with the remainder of the
work being completed in Dr Salisbury's Vertebrate Palaeontology
Laboratory at UQ.
Kerry Geddes, Dr Salisbury's Research
Assistant, carried out most of the delicate preparation work on
the more complete skeleton, which took two-and-half years and an
estimated 3000 hours to complete.
“Unfortunately,
the front portion of the skull was missing,” Dr Salisbury
said.
“It was the only part of the skeleton that
had been exposed to weathering.”
In April 2005,
after four years of systematic exploration in the Isisford
district, Dr Salisbury's team finally found a complete fossilized
skull that would put a face on the new crocodilian.
“Apart
from a slight difference in size, the rear of this new skull is
identical to the portion that is preserved on the first skeleton,
so we are sure that they belong to the same species,” he
said.
Dr Salisbury said Isisfordia had features
that are characteristic of modern crocodilians, such as vertebrae
that fit together via loose ball-and-socket joints, and a fully
formed bony secondary palate – a kind of second roof to the
mouth, that allows air to pass to the lungs without entering the
oral cavity.
The research team comprised Dr Steve
Salisbury (UQ), Dr Ralph Molnar (Museum of Northern Arizona), Dr
Eberhard ‘Dino' Frey (State Museum of Natural History,
Karlsruhe, Germany) and Dr Paul Willis (University of New South
Wales and ‘Catalyst', ABC TV).
Their research was
supported by funding from the Australian Research Council and was
conducted in association with Isisford Shire Council, the
Queensland Museum, Land Rover Australia and Winton Shire Council
as part of the Winton Dinosaur Project. Additional funding was
provided by UQ and the Frau von Ketter Foundation, Karlsruhe.
Source
/ Credit: Queensland University
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