Paul Barrett sees himself as a detective, but the clues he is seeking can be up to 150 million years old.  Paul is a dinosaur scientist at the Natural History Museum in London and he sits in an office surrounded by model dinosaurs, some of which look like they have just escaped from a cornflakes packet.  ‘I love them, there’s nothing like the dinosaurs in the world today.  You often have to try and reconstruct what they did, what they looked like, how they behaved from very limited evidence, from the fossils that we see today.  It’s a bit like being Sherlock Holmes and trying to solve a mystery from very few clues.’  Paul specialises in dinosaur feeding, and he does that by studying dinosaur poo.

 

Figuring out what dinosaurs ate millions of years ago is not an easy job.  Today, scientists will often examine an animal’s poo to find out what it has been eating, sifting through it to find particles of plants or small bones of animals or birds.  Paul’s job is less smelly, because dinosaur poo looks like the real thing, but has fossilised and is called coprolite (meaning dung stone). ‘I’m glad I don’t have to work with a clothes peg on my nose,’ he says laughing, ‘Dino poo fossils are quite common if you know what you are looking for, especially those of meat eaters’.  Asked why, he says, ‘Think of the different consistency of a meat eating dog’s poo, and the runny green mess left behind by a  grass eating cow.  The meat eater’s contains much more of an element called phosphorous which comes from bones and makes the poo quite stiff.  If your dog has been crunching on a bone, the fact will be obvious later when you take him out.’  This difference makes it easier for the poo to become fossilised.  But imagine trying to work out which kind of dog left one particular brown mess on the pavement.  

 

Scientists have only been able to positively connect only one gigantic coprolite with the animal that left it behind.  The king sized piece of rocky dung was found in Canada in the mid 1990’s. This, the biggest fragment of dino poo ever found  is almost 30 cms long, but over 200 other smaller bits discovered nearby would have made up the original two and a half litre dump/poop.  Its great size combined with the age of the rocks in which it was found (65 million years old) indicate a top carnivore, and Tyrannosaurus rex was the only dinosaur of that time capable of producing such a large coprolite.  By slicing the coprolite thinly and examining it under the microscope the researchers found that the T rex’s most recent meal had been a young herbivorous or plant-eating dinosaur called Triceratops.

 

Even better evidence of what the dinosaurs ate comes from fossilised dinosaur stomachs or guts and these are very very rare, because the guts are the bits that start to rot first. Basically the animal has to die and be buried very quickly, and also not be discovered by other scavenging dinosaurs.  For this to happen the corpse either has to be covered in volcanic ash during an eruption and sealed away, or be sunk in an environment where there are few bacteria or worms to cause decay; a low oxygen environment like a swamp.  Only 20 to 25 stomachs or guts have ever been found, and most of these were discovered in China.  But one was found in the UK, in a brick pit in Surrey, 30 miles from London by an amateur fossil collector called Bill Walker in 1981. These precious fossils give the only direct clues of dinosaur diet because they are still attached to the animal they belonged to.

 

The Surrey dinosaur is so far the only known fish-eating dinosaur in the world.  Called Baryonyx, it lived 125 million years ago.  It’s stomach contained fish scales and bones, plus the remains of its last meal, a young Iguanadon lizard. Almost 10 metres long and 2.5m high, Baryonyx weighed in 1.5 – 2 tonnes.  It was equipped with claws a third of a metre long and crocodile-like jaws crammed full of 96 jagged teeth.  Fish eater or not, you would not have wanted to bump into one.  Baryonyx probably waded in rivers and shallow seas to catch fish like today’s brown bears catch salmon. There must have been many other fish eating dinosaurs but since their stomachs have not been found we can only guess which might have preferred a fishy morsel by comparing their skeletons and teeth with living animals.  ‘The jaws gave us a clue, even if we had not found one with a stomach,’ says Paul, ‘the teeth of all living animals are adapted to be as effective as possible in dealing with their specific diets.  Baryonyx had teeth very similar to those of modern crocodiles, conical shaped, and lots of them in a long jaw to maximise the chances of grabbing a passing fish.’ Even Sherlock Holmes would have been impressed how much can be learned about dinosaur habits and behaviour from fossils.