Science Interviews


Fri, 4th May 2012

Reassembling the Remains of Ancient Sea Creatures

Espen Knutsen, Natural History Museum in Oslo, University of Oslo

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Chris -  Espen Knutsen is reassembling the remains of something you really wouldn’t want to swim with...

Espen -  If you think of a turtle maybe without the shell and you add a long neck to that and sometimes a small head and sometimes a large head, depending on what sort of plesiosaur we’re talking about, and you basically have the plesiosaur body plan sort of laid out.

Chris -  Were they vicious?

Espen - Some were.  Most of the ones we have here from our locality at leastplesiosaur are small-headed.  I mean, the head is probably about 30 centimetres long and the teeth are very slender up to maybe 2 centimetres long and very thin, perhaps it’s half a centimetre or so in thickness, and probably ate mostly squids and small fish.  And then you have the large-headed pliosaurs which is another group of plesiosaurs that had heads up to maybe 2 ½ to 3 metres.

Chris -  Metres?

Espen -  Yeah.

Chris -  And teeth.  How big?

Espen - And teeth like cucumbers basically, yeah.

Chris -  And probably quite a bit sharper too.  So they're eating things they would’ve found in the sea.

Espen -  Yeah, the pliosaurs obviously would probably eat anything they would come across - the plesiosaurs or ichthyosaurus which are the other group of marine reptiles you find there, and also larger fish.

Chris -  If they're living in the ocean, it would’ve been pretty cold here, wouldn’t it?

Espen -  Yeah, the temperature in the ocean 150 million years ago in Svalbard is estimated to have been about 10 degrees based on isotope analysis, which is obviously cold for a modern day reptile at least - if you put a snake in a 10-degree water, it’s not going to do much.  So obviously, these reptiles would’ve had some way of keeping themselves warm, whether they were endothermic or just stayed warm due to their large sizes.  It’s still unknown but maybe in the future, we’ll know something more about that.

Chris -  Big fish like salmon sharks are effectively warm-blooded because the core of the animal is so far from the outer part of the animal, where the water is cold, that just metabolism alone means that they're running at near human body temperature inside and stuff closer to the surface less so.  So do you think these plesiosaurus are probably similar?

Espen -  Yeah, possibly at least the large pliosaurs.  It’s a bit different with the smaller plesiosaurs because they have a fairly large surface area compared to body volume and they might even have migrated south, parts of the year.  Maybe the sea temperature was a bit warmer in the summer and obviously, that's comparable to faunas in England at the same time and they might have migrated back and forth through our locality and the English localities annually perhaps.

Chris -  When were they swimming around?

Espen -  All of our animals are from the late Jurassic which is right on the border to the Cretaceous. We’re talking about 150, 140 million years ago.

Chris -  Would they have evolved originally in the ocean and stayed there or could they have come out of the land and gone back into the water?  Do we know where they came from?

Espen -  We don't know too much about the origin of plesiosaurs, other than that they originated from land living tetrapods. So they were some sort of reptile that once in time, in the early to middle Triassic, started wondering into the water and adapted to an aquatic lifestyle there and we do have middle to late Triassic sauropterygia, which is this group of fossils from other places in the world, which are sort of a precursor group to these plesiosaurians.

Chris -  It’s quite interesting that the invasion of the land happens from water onto land and then the animals go back into the water obviously because there is some kind of niche there and now, here we are 100 million plus years later, finding them.  So how do you go and get these specimens?

Espen -  Well how this all started is basically, we go walk around on the Svalbard and it’s quite barren up there.  It’s basically an Arctic desert so there's not much vegetation so we can walk around and look at the surface for bones that are weathered out from the surface and roll down the hill, and then we follow these little bone pieces uphill and we can find the source sometimes and other times we don't.  And if we do find the source of the pieces then we can start brushing slowly and then maybe there's more coming out, and maybe there's not.  If there is, then we can start excavating whatever’s in there, based on what we can see from the preliminary excavations, we decide whether or not it’s worth starting to excavate because it’s quite an ordeal to remove tonnes and tonnes of overburden and every year, we remove by hand 100 tonnes or so of shale.  So, we want to be a bit picky about what we’re actually taking out.

Chris -  And when you spot one, how do you get it out?

Espen -  Once we’ve finally decided which one to take out, we remove the older burden, brush clean the surface of the bone and then we add wet toilet paper, and some wet plaster, and a piece of burlap dipped in that plaster and then we cover the whole thing with plaster and iron and so on, until we have lid and then we dig down around the lid, around the specimen, cover the sides with more plaster. Eventually, we have sort of a mushroom of plaster, shale and bone that we flip over to the other side and then cover the other side with the same wet toilet paper and plaster again and we cocoon the whole thing in that and transport it back to the museum.

Chris -  So that's the summer job and then winter time comes and you're here in the lab, now picking apart that mushroom or that cocoon, that plaster cocoon to get the find out.  So how do you then process it?  What have we got here?  This looks like a bed of plaster.  Is this one that you've basically got going here?

Espen -  Yeah, so this is a plesiosaur lap.  We’ve already prepared from one side, so what we do when we come into the lab, we first let it dry for a couple of months because we can't glue it when the specimen is wet, and then have a little saw, we cut the cocoon open and start picking away with little tweezers and little brushes, so all the loose shale, and simultaneously glue and stabilise the bones.  And then once one surface is done, we can toilet paper and jacket, plaster jacket, that side and then we flip the whole thing, take the lid off the other side and do the same thing there.  Eventually, we get this nicer-looking specimen here with no shale and basically, stabilised bones and then Myalee is sitting here.  She has to prepare it, really - she scrapes away excess shale and gypsum crystals that sometimes grow on these bones, and stabilises these specimens further.

Chris -  Can you give us a guided tour of this one that we’re looking at?  So, there is in front of me, the size of a large dining table with – I can see some of the obvious bones.  There are vertebrae and things, all encased in here, but can you talk us through this fossil and just explain what the various bits are?

Espen -  Yes, so this is part of a plesiosaur that we excavated 2 years ago and what we have here is we have the whole vertebral column from the head which isn't here now, but we have that in separate jackets and through to the body and the shoulder, and then we have parts of the body and just before the hip, the rest of the skeleton has weathered out and we have...

Chris -  And ribs there?

Espen -  Yeah, all these. They're body ribs and then you have the neural arches which goes on top of the vertebra there, and then all these flat bones, the four flat bones here are from the shoulder girdle which is on the plesiosaur and is basically as a flat plate on the front of the chest. That connects the front limbs.  So we have the upper arm bones here and the lower arm bones are reduced to these very short triangular-looking things and then all the fingers are coming out nicely forming a flipper.

Chris -  Is that effectively the wrist there?  Are they sort of the equivalent of carpal bones?

Espen -  Yeah, all of these little round bits are the wrist, and this one and this one, these two triangular bones which are the size of...One is the size of a coin and the other one is twice that size.  They're the lower arm bones, so the radius and ulna that we have.

Chris -  And then these little ones, are they the equivalent of phalanges in me, the finger digits?

Espen -  Yeah, that's all phalanges.  So, what we have in plesiosaurs is something called hyperphalangy which means that they increase the number of phalanges within each digit, which is something they do to form this paddle shape of the limb.

Chris -  So what’s special about the dinosaurs that you're getting out or what's special about the Svalbard specimens compared with ones that we’d find elsewhere in the world?

Espen -  Faunal composition-wise, it’s basically the same.  We have the large headed pliosaurs, we have the long-necked plesiosaurus and ichthyosaurs, but all of these, when you look and go into detail, and look at all the details of the limbs and the vertebral column and the shoulder and so on are slightly different from what we see from other places like the Kimmeridge and Oxford plain in England for instance, and all actually constitute new species.  We have five new species of plesiosaurs and four new species of ichthyosaurs from this place and we still keep digging out more every year.  We have 30...

Chris -  And lots of them.

Espen -  Yeah, we have 31 specimens so far and probably another 60 out in the field that we have mapped already and we find another 10 or so every year as well.

Chris -  So, what do you think will be ultimate outcome for this one because I can see the bones have all been glued together?  Will you actually be able to assemble this?

Espen -  Well this one is actually special that it’s articulated.  All the bones are laying in the position that they were when the animal was alive.  The problem is that the animal has fallen onto its back when it’s at the sea bottom, so the rib cage and everything has collapsed on top of the vertebral column, but all of these bones go nicely together so what we’re going to do eventually when we get the room as well in the museum, this is a big animal, probably 4 or 5 metres long, we want to reassemble all the bits and lay it out nicely so people can come and view it.


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