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Tooth shows 5m-long pliosaurs swam in Austral -

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Robyn Williams: So it's not just Queensland where the big finds are being made, go to Museum Victoria and you'll see a big room underground chock-full of bony treasures are being identified. That's where Erich Fitzgerald shows me a very large tooth.

Okay, you've got something in front of you that looks a bit like a brown tooth. Erich, what is it?

Erich Fitzgerald: It's actually a tooth that is about the size of your thumb or an average human thumb, and it's the tooth of an ancient reptile that swam in the rivers of Victoria about 110 million years ago.

Robyn Williams: And what would you call it?

Erich Fitzgerald: We've identified it as a pliosaur, which is a relative of the more well-known plesiosaur. And plesiosaurs of course are the almost snake-necked marine reptiles with four flippers that have been described as what you would get if you took a turtle's body and then stuck a snake through the shell. So you have a little tail and a long neck with a small head. But the pliosaurs are a different beast. The pliosaurs were a similar body form to a plesiosaur, so four flippers, not too unlike a seal or a sea lion, but with a relatively short neck and a crocodile-like head or skull.

Robyn Williams: So we're not talking dinosaur.

Erich Fitzgerald: Most definitely not. Plesiosaurs and pliosaurs and things like ichthyosaurs or fish lizards are often confused with dinosaurs, but they are quite unrelated.

Robyn Williams: From this tooth how can you tell what it belongs to?

Erich Fitzgerald: Well, that's a really great question because for a long time, in fact since 1994 until just this year, it had remained unidentified, and there was a question mark; was it a dinosaur tooth, was it a crocodile tooth, was it maybe even the tusk of a strange early relative of mammals, something called a dicynodont? And we weren't really sure, and that's because this tooth is quite different to any other animals we would anticipate (and that's a key word, 'anticipate') finding in sandstones that formed at the bottom of a river.

What we finally worked out, and it was thanks to an insight from a visiting researcher, Roger Benson from the University of Oxford, was when looking at it we realised that there were some certain ridges on the enamel and a general conical shape to it that you only tend to see in aquatic reptiles, not crocodiles, not some kind of bizarre fish-eating dinosaur, but these pliosaurs. Until now, pliosaurs had primarily been known from marine deposits, so rocks that were formed at the bottom of shallow seas. So what's really surprising here is that this is a pliosaur that swam up a river and probably was living in a river.

Robyn Williams: What river? Where?

Erich Fitzgerald: Well, the rivers that were formed in what was basically a rift valley that formed at the southern end of Australia while it was just in the initial stages of separating from Antarctica. And those sandstones where the fossils were found were actually in South Gippsland in the state of Victoria.

Robyn Williams: What are the chances of you going back and finding more?

Erich Fitzgerald: Well, there are other hints. We have bits of rib, we have some fragments of vertebrae which suggest this kind of animal. Future fieldwork is really now directed at finding more of this animal. I like to think that it is really these pliosaurs that were living in ancient rivers of southern Australia that are, to me at least, far more interesting than the dinosaurs that were roaming the land around them.

Robyn Williams: I'm sure you've thought of this, but give me a picture of what it might have looked like.

Erich Fitzgerald: Well, from the tooth we can tell that it represents an animal that is at least four metres long. How have we worked that out? Well, we've taken the measurements of this one tooth we have and compared it with the smallest teeth in a range of pliosaur species, and it most closely corresponds in its proportions to the teeth of pliosaurs found in the UK actually…

Robyn Williams: Like the Loch Ness monster.

Erich Fitzgerald: Well, a bit like the Loch Ness monster but actually represented by evidence. The Loch Ness monster is all fine and good but I want to see a body. So this is a so-called Loch Ness monster-like animal, represented by solid evidence, and those pliosaurs that it most closely corresponds to in proportions are about 4 to 5 metres long.

Robyn Williams: And it would have been swimming around fishing all day.

Erich Fitzgerald: I would suspect so. However, as we know from crocodiles, which are today a reasonable ecological analogue for a pliosaur, they will feed on anything really that is smaller than them, and indeed some prey that is the same size. So it's not within the realms of impossibility, if you like, that this pliosaur may even have fed on dinosaurs that came to the river's edge to feed or drink.

Robyn Williams: How special is it in terms of a find for this region?

Erich Fitzgerald: It is special because until this point the only aquatic reptiles found in these rocks were relatively small plesiosaurs, probably no more than about two metres long. This is an animal twice the size with quite different teeth. Those plesiosaurs have really needle-like teeth, almost something you'd expect to see in, say, a small dolphin. So animals that were specialised for catching small fish. The pliosaur has these much more robust bruisers of teeth, and that's really an animal that is specialised for feeding on larger prey with larger bones in the body. So what this is telling us is that there are two distinct species of plesiosaur-like animals swimming in these rivers, and that's surprising. Everyone else around the world where you have these pliosaurs or plesiosaurs in riverine deposits, they are represented by just the one species. So this indicates that we have two quite disparate types of these swimming in the same environment.

Robyn Williams: Erich, we're beginning to see with all these ancient creatures that whereas…I actually had somebody from the American Museum of Natural History a few years ago on The Science Show saying that, well, there are no real dinosaurs in Australia, no, there's nothing particularly big. Now in northern Queensland and around Dinosaur Cove near Geelong you are finding huge monsters, and now in Gippsland. What's going on?

Erich Fitzgerald: There's a couple of things going on here. Fossils here are hard-won, particularly fossils from the age of dinosaurs, the Mesozoic era. So we have to work much harder in Australia to get relatively little reward. Furthermore, there just aren't that many palaeontologists in Australia, and there probably never will be. It's a big area to cover, and there's not the same population size, budget et cetera, to support a vast number of palaeontologists, as there are in, say, North America.

However, people have come up with new ways of finding fossils, and in Queensland around Winton they've worked out how to find at least some dinosaur fossils of a particular size range price, so larger dinosaurs in that area. Here in Victoria we use the approach of really going to areas where we know the geology is probably conducive to preserving these sorts of fossils and then having at it with hammer and chisel, rock saw, jackhammer, and really finding whatever we can. And that's why often they are fragments. The geology rarely preserves more complete associated skeletons that you might have classically found in China or the western United States, Canada, or say the Gobi Desert in Mongolia. But what we do find is quite different to elsewhere, that's what makes it really worthwhile.

Robyn Williams: Erich Fitzgerald curates pliosaurs and various terrible giant lizards in Museum Victoria. He's also got some pretty large diprotodons, but that's for another day.

Erich FitzgeraldCurator of Vertebrate Palaeontology
Museum Victoria

Further Information
Erich Fitzgerald at Museum Victoria

PresenterRobyn Williams ProducerDavid Fisher