PETER SCHOUTEN
NAT UR E
January–February 2014 21W
AS THIS ANIMAL for real?
It sounded more like
something from a poorly
scripted, low-budget horror film.
Could an ancient relative of everyone’s
favourite venomous, duck-billed,
egg-laying mammal really have grown
to epic proportions and had a taste
for flesh? I could picture the scene
through the Hollywood lens: maniacal
monotremes marauding through
the sewers of Sydney, ready to burst
out of drains and clamp their bills
around the ankles of unsuspecting
pedestrians, dragging them to
their untimely deaths.
Implausible as it all
sounded, this prehistoric
Platyzilla really did exist,
even if descriptions of it
were a little overblown in
the press. Researchers led by
Professors Mike Archer and
Sue Hand, at the University
of New South Wales
(UNSW), announced late last
year that they’d discovered
remains of a metre-long
species, which had powerful
teeth for preying upon
turtles, frogs and fish.
Obdurodon tharalkooschild inhabited
pools and rivers in the rainforests that
covered Queensland’s Riversleigh
region 5–15 million years ago.
The description of this animal
as “giant” in news reports conjured
images of an animal the size of a small
car, so I was disappointed to find it
had been much smaller. Nevertheless,
by monotreme standards this was
huge. Today’s platypus is about half
a metre in length and, as an adult,
doesn’t have teeth, instead relying
on horny pads in its bill to crunch
up invertebrates. Although O.
tharalkooschild was only twice as long as
a modern platypus, it is likely to have
been about four times the weight.Former UNSW student Rebecca
Pian, now at Columbia University in
the USA, discovered a fossil tooth at
the Riversleigh World Heritage Area
in 2012. The size and eating habits of
the new species were later determined
from a detailed study of the size, shape
and function of the tooth, which is yet
to be dated definitively.
Fossil discoveries over the past
40 years have given us snippets of
information about platypus evolution,
and have shown that similar animals
have been a part of the Australianstory for at least 110 million years.
The most ancient platypuses were also
found in Antarctica, South America
and possibly Madagascar. By around
25 million years ago, they were left
only in Australia, where up to three
species shared the streams of the lush
north and centre of the continent.
In 1975, the first known ancient
platypus was described from fossilised
teeth found in central Australia, by
Mike Archer and US palaeontologists
Michael Woodbourne and Richard
Tedford. They named the 26-million-
year-old species Obdurodon insignis.
Obdurodon means “persisting tooth”Platypuses with bite
The discovery of a prehistoric, supersized, carnivorous platypus helps
to fill in the family history of this unusual and iconic Aussie species.and distinguished this genus of
prehistoric toothed platypuses from
their modern descendants.
A second toothed platypus,
Obdurodon dicksoni, was discovered by
Mike Archer’s group at Riversleigh
in 1984 and dated to about 15 million
years ago. Even more exciting was
the discovery of the teeth of a
61-million-year-old South American
relative in 1992. Hailing from
Patagonia, Monotrematum sudamericanum
demonstrated how widespread these
early platypuses really were.
The newest species is
significant because it is
much larger than any of the
other five known relatives,
suggesting that the family
tree is more complicated
than we thought, with
unexpected side branches.
This hints that there may be
other weird and fascinating
platypus relatives waiting to
be discovered in Riversleigh’s
rich fossil deposits.
The species descriptor
tharalkooschild comes from
an Aboriginal creation
story about the platypus:
Tharalkoo was a disobedient female
duck who ignored her parents’
warnings and swam downstream,
where she was ravished by a water rat.
Later, when she laid her eggs along
with the other young ducks, she was
horrified to discover it contained
not a duckling but a platypus, with a
mixture of rat and duck features.
This indigenous cautionary tale
was then itself a horror story of sorts,
one which had been told and retold
over countless generations.JOHN PICKRELL is the editor of
AUSTRALIAN GEOGRAPHIC. Follow him on
Twitter at: twitter.com/john_pickrellPlatyzilla ambush. An ancient platypus
from Riversleigh had a taste for fl esh.