Dinosaur eggs have been found in nests, and groups of nests were found in one extraordinary site, suggesting that dinosaurs nested together. Then, the fossilized footprints of the tiny dinosaur Compsognathus, a species belonging to the clade called theropods — criss-crossing and moving together — were found, showing they flocked and lived together. So dinosaurs were social animals, and they took care of their young.
One major question about dinosaurs concerns how such large animals, purportedly reptiles, managed to maintain their body temperature. Since they are so reptilian, it was assumed that they would be cold-blooded, requiring external heat sources to give them energy. But this wasn’t really feasible, given the size of many dinosaurs, and the fact that many clearly lived in cold climates. So how did they maintain their body temperature? Scientists hadn’t yet found fossils that could answer this question.
Then, in 1996, Li Yumin, a farmer and part-time palaeontologist from Northeast China, discovered a feathered dinosaur.
Sinosauropteryx prima was the first dinosaur to be found with a downy fuzz covering its entire body. Until this fossil was discovered, the idea that dinosaurs were related to birds remained in the realm of theory. But here, in this exquisite fossil of a small dinosaur with a very long, curving tail, was evidence of primitive feather-like filaments, rather than the feathers of modern birds. The fossil was so well preserved that there was evidence of colour, and that the tail was striped. It was said that when John Ostrom saw the first photos of the fossil, he went into shock. Perhaps some dinosaurs did evolve into birds.
Upwards of 500 species of dinosaurs have been found: from small bird-sized creatures to the giant Tarbosaurus and Brachiosaurus. One fossil hunter found a single vertebra 2m in height. It suggested that a gargantuan animal, more than 30m in length, once walked the earth. But the bone, already so fragile and delicate, crumbled away into nothing, and no other bone of similar size has been found since.
While the vast majority of early dinosaurs were found in the Americas, China is now proving to be an important fossil hunting ground. Sinosauropteryx was found in the Yixiang Formation, a geological formation made up of volcanic ash and river sediments. One is tempted to imagine dinosaurs fleeing from volcanic eruptions en masse, only to be caught by the ash, to be preserved for millennia until curious humans went searching for their remains in hope. Astonishingly, many of the feathered dinosaurs found thus far come from this formation.
This year, the Yixiang Formation came up with another win. Xiu Xing, a famous Chinese palaeontologist who has described many new species of dinosaurs, reported the discovery of the largest feathered dinosaur found to date: Yutyrannus huali. Not only was this dinosaur larger than the feathered dinosaurs found thus far — Sinosaruopteryx, Caudipteryx and many others — but it is related to Tyrannosaurus rex, the most feared and beloved predator. T Rex also belongs to the theropod group, and the evidence for a feathered relative suggests the tantalising possibility that T Rex might have had feathers, even if only as juveniles. Y. huali (an elision-portmanteau of the Latin and Chinese meaning “beautiful feathered tyrant”) has a fine, downy fuzz — much finer than that found on Sinosauropteryx — all over its body. Its size suggests that larger dinosaurs could also have had feathers, that they had more complex ways of maintaining body temperature. But best of all, it tells us that a branch of the dinosaurs did evolve into birds. Suddenly, the traditional image of a T. rex, Stegosaurus, Triceratops and Brachiosaur in halcyon volcanic meadow was gone, changed forever. Some monstrous creature, half bird and half reptile must take its place.
Apart from bones and feathers that have turned to stone, scientists have other evidence that dinosaurs evolved into birds. One of the best ways we have of working out how different species are related is by comparing proteins and DNA of different species to see how closely they are related. So far, it’s proven difficult to obtain DNA or proteins from fossils; after all, the youngest fossils of dinosaurs are 65 million years old. The proteins and DNA would largely have broken down, but a few scientists claim to have obtained and observed proteins in T Rex bones, Dr Mary Schweitzer among them. When the proteins were analysed, they were found to contain collagen, an important, if common, structural protein. And these proteins were found to be most similar to collagen found in the common backyard-farmyard Gallus gallus — the chicken.
As more well-preserved fossils emerged and as our understanding of anatomy increased, scientists began to look at some of these fossils with fresh eyes. One of the key characteristics of birds is air sacs; a complex system by which birds breathe and retain oxygen. It’s now apparent that dinosaurs did have air sacs, they were just located in an unexpected part of the animal.
So dinosaurs, who seemed wondrous and strange animals to begin with, turned out to be more wondrous and strange than we could have imagined — bizarre bird-like reptiles, unlike anything we know today. Their descendants developed feathers, sometimes of gorgeous plumage, and their songs and calls have entranced us for centuries.
The dinosaurs are still with us.