ARTICLES
A giant species of Trilobite inhabited Australian waters half a billion years ago (continued)
Exceptional fossil deposits
What is even more special about the Emu Bay Shale examples is
that because Redlichia rex was so big, the appendages are also
very large, making them easier to look at in detail.
Our most important understanding of life around the time of the
Cambrian explosion comes from a series of rare, exceptional
fossil deposits called Konservat-Lagerstätten (German for
“conservation storage-place”). These deposits preserve not only
the hard parts of organisms such as shells, but also the soft parts
such as eyes, muscles and guts. The most famous of these is the
Burgess Shale from Canada, although a number of other similar
deposits have been discovered in places such as China and
Greenland.
Australia also boasts one of these deposits – the only one in the
Southern Hemisphere. It is called the Emu Bay Shale and is found
on Kangaroo Island in South Australia. The most common fossils
within the Emu Bay Shale are trilobites.
The latest find
In our study, we describe a very large new trilobite from the
Emu Bay Shale. It’s one of the largest trilobites known from the
Cambrian Period.
A graphic reconstruction of the Redlichia rex appendage used
for shredding and crushing prey.
The most important feature of these is an enlarged inner side of
the base of each pair of legs, which was covered in short, robust
spines and worked as a nutcracker.
Carnivores of the sea
Unlike those of other trilobites, the morphology of the spines
suggests they may have been adapted to crushing shells of
other Cambrian animals. If this were the case, the most likely
food Redlichia rex would have been eating was other trilobites.
In the Emu Bay Shale we also find what are called coprolites
– fossilised poo. In these we have found pieces of crushed-up
trilobite.
A large specimen of the newly described trilobite Redlicha rex
from the Emu Bay Shale compared to a 20c coin.
Due to its exceptional size and armament, we decided Redlichia
rex would be an appropriate name. This is reminiscent of the name
Tyrannosaurus rex – rex means “king” in Latin. The Redlichia
part of the name is the genus (like the ‘Homo’ in Homo sapiens),
originally named in 1902 after palaeontologist Karl Redlich.
Because the Emu Bay Shale preserves the soft parts of organisms,
we find the appendages (or legs) of trilobites preserved as well
as the hard shell. These soft parts are extremely rare; complete
appendages are known for only six of the more than 20,000
described species.
Crushed-up pieces of trilobite were found in the coprolites, the
fossilised poo.
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SCIENCE EDUCATIONAL NEWS VOL 68 NO 3