Is it a dinosaur, a bird or both?
Luis Chiappe describes some of the amazing dinosaur exhibits at the Los Angeles County Museum. One, a plesiosaur, the giant marine dinosaur, shows the remains of a foetus. This was a reptile that gave birth to live young rather than laying eggs. The collection includes many ancient birds which are now known to have evolved from dinosaurs. There was a large range and diversity of birds which lived at the same time as dinosaurs. Some specimens illustrate the evolution of these creatures as seen in some 20 species of feathered dinosaurs.
Robyn Williams: And so to birds, and feathers. But are they really birds? Meet Luis Chiappe, director of the Dinosaur Institute at the Los Angeles County Museum. He's the one who found the baby in that giant marine reptile, as published last year.
Luis Chiappe: This is a plesiosaur, not a dinosaur, one of those giant marine reptiles that swam when dinosaurs were alive, in this case 75 million years ago, in Kansas actually because at the time Kansas was flooded by a shallow sea.
Robyn Williams: But how did you find out that there was the remains of a foetus there?
Luis Chiappe: Well, that required a close inspection of the specimen. When you look at the specimen you can notice that there are bones of two different animals, but when you look closely you see that the bones are of the same kind. There is a perfect match between the vertebrae of the big one and the small one, or the humerus of the big one and the small one. So that allowed us to determine that they were both of the same species.
At the same time we've noticed that the bones of the small animal were inside those of the big animal, and you can tell that because the bones of the small animal are adhered to the inside of the bones of the big one, indicating that it was contained within the body of the big one. You can then connect the dots and figure out that this is essentially a baby.
And the other element...because you can say, well, how do you know that it is not food? Well, we looked carefully at the bones also and we didn't find any indication of digestion, any evidence of gastric acids that could have acted on the specimen.
Robyn Williams: We're talking about something that is, if you like, the Loch Ness monster, that's the kind of image we have, a very big animal, and nonetheless a reptile, and most people would imagine that a reptile lays eggs, but not like a mammal keeps the offspring inside to be born later. So how come?
Luis Chiappe: Well, that is actually correct and indeed most reptiles lay eggs, but many of them give birth to live young as well. To begin with, it's remarkable that we did not know this about the plesiosaurs essentially, or it least we had no direct evidence of them giving birth to live young, and this is the first time that we've been able to document that.
But also the other thing that is remarkable is that you have a single and a very large baby. So we're talking about an enormous investment from the side of the mother into this enormous baby. We calculated that the baby would have been about 40% of the length of the mother, who was already very big, when he was born. That led us to argue that these animals probably extended their care for a prolonged period of time. So there was essentially an extended period of maternal care after the baby was born. A similarity or something that evokes the behaviour and strategies of living marine mammals, like whales and dolphins that also give birth to one single very large baby and remain with the baby, in the case of a mammal, nursing. In the case of the reptile, that wouldn't have happened, but they remain with the baby for a long time.
Robyn Williams: Fascinating science, isn't it, and one of the main lines of research in your lab here at the Museum in Los Angeles is of course the other branch of what the dinosaurs and reptiles led to, and that's birds. And in front of me you've got this vast number of specimens you've collected...from where?
Luis Chiappe: They're from all over the world. Here in front of us we have some Chinese specimens, we also have specimens from Argentina. But in the last 20 years we have made discoveries in Madagascar, in North America, even in Australia, a few of them. All of these discoveries are revealing an enormous diversity of ancient birds, the birds that live with the dinosaurs.
Robyn Williams: Yes, we've got a vague idea that there were just one or two or three, you know, Archaeopteryx, a few famous birds, but not that many. The picture you're getting is that there is a huge number of different species of birds living at the same time as dinosaurs latterly.
Luis Chiappe: Yes, they diversified and occupied many of the ecological niches that we see birds occupying today, and they were replaced by modern birds, the birds that eventually would evolve into the penguins and the hummingbirds and the pigeons that we see around us.
Robyn Williams: For how many millions of years was it? How long were they there?
Luis Chiappe: For a long time. I mean, Archaeopteryx, which is the earliest known bird, is 150 million years old. So the Mesozoic came to an end at around 65 million years ago, so you're talking about 85 million years or so of early bird evolution.
Robyn Williams: What was the fuss last year about the Archaeopteryx, suggesting it wasn't necessarily the original bird? It was being questioned, wasn't it?
Luis Chiappe: Sure. It all relates to essentially what I think is the most significant breakthrough in the history of dinosaur palaeontology which is the realisation that birds are living dinosaurs, that birds evolved from the dinosaurs. And then you have a very primitive bird, in my opinion, like Archaeopteryx, that at the same time is very dinosaur-like. So it is right in that rather murky line of is it a dinosaur or a bird, is it on this side of the fence or on the other side of the fence?
Robyn Williams: What sort of story is the Chinese work giving you at the moment? Obviously there are so many of them and they are finding feathers. What sort of picture are they giving you at the moment?
Luis Chiappe: A tremendous picture. In other words, the fossils that are coming from the north-eastern corner of China and date back to between 130 and 120 million years old are exceptional, they're beautifully preserved, as you said. We have a variety of birds with their feathers. We have a variety of dinosaurs that are not birds, that are closely related to the birds, but they are also feathered. We know of at least 20 species of feathered dinosaurs, and it's just a very compelling piece of evidence that birds are the descendants of some of these dinosaurs. It's just a perfect view of an ancient ecosystem, a view like we've never had before.
Robyn Williams: What does it look like? Imagine that you can go in your time machine to one of the places where you've been excavating. What sort of pictures do you get of what the ecology was like back then?
Luis Chiappe: Well, in north-eastern China if you were to be there, say, 125 million years ago, you would be in the middle of a forest with very tall cone-bearing trees, supported by lakes, and a wealth of animals living in both the canopy and the lakeshore; dinosaurs, early mammals, a variety of birds, lizards, turtles, all sorts of insects. It was a time with a substantial amount of volcanism. So volcanoes were in the area, and they were erupting. And you have deposits of ash and lava, essentially basalt. And it is believed that some of the eruptions are probably responsible for the mass mortality that you find in the fossils that are found there, because sometimes you get, say, a slab that contains three, four, five specimens of a bird. How is it that they died altogether at the same time and that they are not scavenged, they are just perfectly preserved?
Robyn Williams: Including their feathers. Dr Luis Chiappe at the Dinosaur Institute, Los Angeles County Museum. And those feathers on great big dinos make them look like champion wrestlers wearing tutus. But the feathers were first of all converted scales for keeping warm. Flight came later.
- Luis Chiappe
- Curator and Director
Natural History Museum of Los Angeles County
Los Angeles CA USA
- Robyn Williams
- David Fisher