What was the first dinosaur discovered?

Chris Smith put this question to Jason Head from Cambridge University...

Jason - The first dinosaurs found probably are the mythological origins of griffins. And so it is thought that actually the fossils of a particular dinosaur Protoceratops andrewsi from Mongolia, which has kind of an almost bird-like face, was thought to be the original kind of impetus for that myth.

In the 1670s, there was a fossil described from the UK that was the lower half of a femur of probably a Sauropod dinosaur. It was not recognised as being a dinosaur, it was thought to be a giant. And, in fact, in 1768 right after Linnaeus had established binomial nomenclature, coming up with the genus and the species name because this bone actually had two rounded edges to it it was given the binomial name Scrotum humanum, for exactly why you would think.

Chris - Indeed, yeah.

Jason - The first dinosaur names that actually stick are Megalosaurus, and Iguanodon, and Halosaurus which are based on fossils from the United Kingdom that were discovered around the 1820s.

Chris - And is that when people first became comfortable with the concept of a dinosaur? When did people begin to realise that there was this very long evolutionary timeline on Earth going back millions and millions and millions of years, and that these were clearly antecedents of the life we see on earth today?

Jason - That’s by, I think, about the early 1700s people start to realise that actually there is life preserved through deep time. And the fossil record, the connectivity of it through time is not recognised until much much later.

Chris - Because people didn’t know how old the Earth was at that time, did they?

Jason - That’s exactly right.

Chris - They had no idea the Earth was 4,500 million years old until relatively recently so they had no idea how quick these things had evolved or how long they hadn’t been here for?

Jason - The recognition of superposition of layers of rock does kind of informally come in fairly early, but recognising that what we’re looking at is a succession of related organisms is much later. So dinosaurs, that construct is really Richard Owen in 1842 when he puts the name to the group formally, and is recognised as being this particular group of extinct giant reptiles.

Chris - And what about the meat eating question: how do we know when they tuck into a burger versus prefer to eat grass?

Jason - The shape of their teeth is an excellent indicator of diet. Just like you can look at the teeth in our own mouths and watch their functions, or look at the teeth of a cat or a dog and see how they can slice meat or grind food, the teeth of dinosaurs had the same thing. Meat eating dinosaurs had almost steak knife-like teeth running along the mouths. Herbivorous dinosaurs have evolved these numerous strategies for complex grinding of food akin to what we would see in ruminant mammals today.

Chris - Matt, you were going to say something…

Matt - Yeah, just going to come in on the age of the Earth thing. This is quite an interesting bit from astronomy from that point of view. The age of the Earth also has to be the age of the Sun as well and for a long time we didn’t know how old the Sun was because we didn’t know what powered it, so before we understood stellar nucleosynthesis like the process that’s powering the Sun right now. Our best guess, it was powered by some kind of gravitation and if the sun is powered gravitationally, it can only be about 15 million year old. So, in the late 19th century, some pre-eminent physicists, particularly Lord Kelvin, one of the most famous physicists of his day used this fact to argue against Darwin right. He said the Earth and the Sun can only be about 15 million years old because that’s how old the Sun has to be.

Chris - What changed his mind?

Matt - I’m not sure if his mind was ever changed actually. I think the scientific community’s mind was changed because we came to understand stellar nucleosynthesis, this process that can power stars for billions and billions of years.