Podcast: Walking with dinosaurs on Britain's Jurassic Coast

Dinosaur tracks

Dorset dinosaur tracks

3 March 2015 by Richard Hollingham

This week in the Planet Earth podcast, Phil Manning, Victoria Egerton and Bill Sellers of the University of Manchester are joined by local geologist Paul Ensom at the Isle of Purbeck on Britain's Jurassic Coast to talk about some dinosaur tracks recently found in the area.

To assist those who find text-based content more accessible than audio, a transcript of this recording is available below.

Richard Hollingham: This time in the Planet Earth podcast: walking with dinosaurs in Dorset. I'm Richard Hollingham and I've come to the beautiful Isle of Purbeck on Britain's Jurassic coast to an area of exposed dinosaur tracks. They are being studied and mapped by a team from the University of Manchester. We will talk to them in just a moment. But first I'm joined by Paul Ensom. You're a local geologist and let's just talk about this area here because we're surrounded here by fields, but this is really a shallow dish of exposed rock and within that dish there are these depressions. So what are we looking at?

Paul Ensom: We're standing on a surface of Purbeck limestone. It was exposed in the late 1990s by a local quarryman, Mr Kevin Keats, and spotted by another quarrying family, the Hasomes, when they were out for a walk. It caused quite a sensation. At the time a team came down taken on by the National Trust who own the site. They surveyed it and came to certain conclusions about what had made the tracks and what sort of track they were. Dinosaur tracks are not always straight forward.

Richard Hollingham: These are dinosaur tracks though?

Paul Ensom: They are indeed dinosaur tracks - an unusual set for this area. This is at the moment a unique site on the Isle of Purbeck.

Richard Hollingham: Each one of these is about, what, four times the size of a human foot, maybe even more than that. Large dishes, they are circular, there's no obvious footprint there.

Paul Ensom: No. One of the things we've discovered in the Isle of Purbeck with dinosaur tracks is that sometimes the animals were walking at a higher level and their tracks were being transmitted downwards onto lower levels of limestone. So, in fact, one dinosaur could produce several levels of track all in one go. A sort of wonderful replication system, which of course was quite good from the quarryman's point of view, they got more for their buck.

Richard Hollingham: So these aren't footprints? We've got to be very careful, these are tracks.

Paul Ensom: Yes they are. They are evidence that dinosaurs walked across this area but not necessarily exactly this level.

Richard Hollingham: Well let me introduce the team from the University of Manchester: Phil Manning, Victoria Egerton and Bill Sellers. Phil, what are we looking at here in terms of what size of animal walked across this landscape?

Phil Manning: You're looking at these enormous long-tailed, long-necked, barrel-bodied quadrupeds, the sauropod dinosaurs. These track ways are a fantastic insight, not only into the preservation and what they can tell us about where the animals were walking, but even the geometry of the tracks can tell us something about how they walked, so we can learn something about the locomotion of dinosaurs. So if you want to walk with dinosaurs this is the perfect place to study them.

Richard Hollingham: Now, Bill, we've got a field of cows behind us, a grazing field of cows. Is this the dinosaur equivalent? You could imagine grazing dinosaurs?

Bill Sellers: It's very hard to work out exactly what the animals would have been doing when they made these tracks. I mean when you look at it, just standing here, it's very hard to spot any sort of pattern and it looks like it might just be a herd of trampling dinosaurs, but actually what we're hoping is when we've done the mapping properly that we will be able to identify some specific track ways, because it is actually much more interesting in terms of working out what the animals might have been doing. If we can identify an individual and follow it's path through the tracks that we have in front of us.

Richard Hollingham: Victoria: what are you trying to do here? Because this has been exposed, as Paul said, since the late 1990s but you are now mapping it in detail.

Victoria Egerton: Yes, so what we're trying to do now is to create this 3D reconstruction digitally, so that we can then measure how big these footprints really are, how deep they go in and the depressions that they make so that we can really understand more about what the sediment underneath was doing at the time that these animals made their footfalls.

Richard Hollingham: So if you can work backwards, what, from these shallow, these dish-like depressions in the ground, you work backwards up to the animal and how it was moving?

Victoria Egerton: Yes we hope so, but we know that some of this is rather limited so we will just do the best that we possibly can.

Richard Hollingham: So, Phil, talk me through how the scanning works. You've got here a tripod, a surveyor's tripod really, but on the top is a box which looks like two shoeboxes stuck together with a computer screen on one side, and in the centre almost a camera - something like that.

Phil Manning: This is an astoundingly expensive shoebox for the simple reason when you're looking for a laser scanner that is going to operate outside in all conditions you want the best of the best, so we tend to use this particular type of kit because it produces astoundingly high resolution scans.

Richard Hollingham: And what's it doing? It's firing a laser out and that's reflecting back off the rock and it's recording that?

Phil Manning: Yeah, it's near infrared laser that you're firing out and because it fires out... we know the speed of light and it's reflecting back from a surface. The detector picks up that reflection and it does 50,000 of those points per second. So think of it as a 3D colour photocopier. Because the really cool thing about it is this has a high dynamic range camera built in as well, so after it has taken the laser scan of the surface it then takes photographs which can overlay, so you've got a perfect colour 3D representation of your landscape, your skeleton or of your person holding a microphone doing a recording in the middle of field. It's the ultimate three dimensional capturing device.

Richard Hollingham: Right - off it goes again.

Phil Manning: You can hear the whir of the engine kicking in.

Richard Hollingham: Now this area is, what, about the size of one or maybe two tennis courts, something like this, an exposed depression of rock that we're looking at with these prints. Presumably there are prints everywhere under this landscape are there?

Bill Sellers: Well they're not everywhere. It's a pretty rare thing to find but you can certainly see the way the soil hasn't been cleared from the rest of the side, so this is certainly a bigger area of footprints and if we had a vast team of people and time to do it we could probably expose a lot more. But, no, tracks like this are extremely rare.

Richard Hollingham: And my doing this detailed mapping, what can you can tell that you can't tell by simply getting down on your hands and knees and measuring it with a tape measure or whatever.

Bill Sellers: It's really hard to get 3D data from just a tape measure and the 3D data is what we need to understand the mechanics that Phil was mentioning earlier on, and that's what we need if we're going to try and reconstruct what these animals were like when they were alive.

Paul Ensom: Can I just come back on something Bill said just now as well about the rarity of this. I mean the site certainly is a very rare event and occurrence to get such a superb extent of tracks exposed. But within the Purbeck sequence we've discovered over the last twenty or thirty years that there are actually numerous horizons with tracks and I've always had this feeling that it's a bit like a carpet, if you could only roll back each layer, like another layer of of carpet, you would find an amazing number of track ways. And just to add a final bit of colour from my perspective, we're looking at a site which is around 140 million years old, so this is a real snapshot of the past.

Richard Hollingham: So, creatures have left this mark from 140 million years ago. You are building up a picture of what these creatures were like and how that picture has changed over the decades, thanks to this technology.

Phil Manning: Well the fossil record is this incredible mosaic of information which has got lots and lots of pieces missing and whenever you find something as beautiful as this, this thousand ton carpet, we can piece together a few more parts of the tesserae, as it were, to make much better conclusions and deductions about how these animals might have functioned, how they might have walked, but more importantly where they lived, because dinosaur bones can be transported miles away from the point of death. This is actually a dinosaur when it was alive, wandering around in a very constrained environment. So we can learn a huge amount from that.

Richard Hollingham: So, Bill, what was this area like?

Bill Sellers: Well, so, this is a sort of lagoon area, so it's interesting because it means that you get both land dwelling animals and you also get marine animals and so, obviously, this was a shoreline area that the animal was moving along and presumably there were food sources that were nearby and that's what the animal was taking advantage of.

Victoria Egerton: One of the nice things about footprints is that they are evidence of behaviour, something we don't get in the fossil records. With skeletons we can only tell so much but this tells us about behaviour. This tells us about these living, breathing animals that walked across this landscape and that's just absolutely incredible to have that record.

Richard Hollingham: And what sort of picture are you building up? Presumably there was more than one. At the very least you can tell that they were moving together.

Victoria Egerton: Not necessarily.

Richard Hollingham: Okay! That's why you're the expert and I'm not! Okay.

Victoria Egerton: You do have lots of different footprints going on here. Now, if could be from one individual, it could be from multiple, but right now we can't really say.

Richard Hollingham: Paul, you've been coming to this site for, what, almost twenty years now since it was discovered.

Paul Ensom: Well, yes. The interesting thing about the site is that having been discovered and initially described, it was actually buried to protect the surface and it's only because Dorset County Council, the Jurassic Coast team, are in discussions with the National Trust as to whether this can now take on a new purpose and actually be opened up to the public and exactly how the public can visit it, that this has now been re-cleared and is now being re-assessed. The new survey, new technologies being used, new ideas about dinosaurs, new thoughts or re-thinking our thoughts about the nature of these tracks, all makes this a very important bit of study that we're doing now.

Phil Manning: This is an amazing resource for research, but also it can be used to inspire future generations of scientists and we're really pleased to be working with the Jurassic Coast Project and they've got this fantastic idea, the Jurassic classroom, and they're bringing primary school teachers here to see what we're doing and so that kids all over the UK can learn something about the research we're doing here and how it can help us understand more about dinosaurs, but more importantly how they can actually get involved with looking at this kind of data and getting much closer to literally walking with dinosaurs.

Richard Hollingham: Paul Ensom, Phil Manning, Victoria Egerton and Bill Sellers - thank you all very much. And next time we'll have more from Phil he will be recording an audio diary from the Badlands of South Dakota 'Looking for Dinosaurs.' We will share some pictures of the tracks here on Twitter and Facebook and do visit Planet Earth online for more news of NERC funded research. And that's the Planet Earth podcast from the Natural Environment Research Council. I'm Richard Hollingham from the Isle of Purbeck in Dorset, thanks for listening.