Feathered dinosaurs changed definition of birds
Until 1997, birds were defined as animals with feathers, and any feather was supposed to come from a bird.
But that changed when a Chinese palaeontologist found a fossil dinosaur with feathers. Dr Ji Qjang’s fossil was about the size of a turkey, had the skeleton of a reptile, was a fast runner, and had quite long feathers on its forelegs and tail.
The feathers of protarchaeopteryx (sorry, all these dinosaurs have tongue-twisting names) probably served to signal potential mates or mating competitors.
The turkey-sized bird was unearthed in Liaoning province, north east of Beijing. The 120 million to 150m-year-old rocks there have yielded a fabulous collection of more than 100,000 fossil insects, fish, turtles, salamanders, lizards, bats, the earliest mammals, and the earliest known flowering plants. Their finest details were trapped by volcanic ash showers in an ancient lake bed, the site sometimes being called the Mesozoic Pompeii.
Another feathered dinosaur was soon discovered in Liaoning – the four-winged microraptor whose fore and hind limbs were covered in feathers, enabling it to glide on four wings. Subsequently, more than 20 more genera of feathered dinosaurs have been discovered in these rocks, many completely covered in downy feathers that probably insulated them against the cold. As chicks, these dinosaurs were probably the first creatures to feel the luxury of a fuzzy feather-lined nest or a feathered mother sitting on them. Some palaeontologists argue that even T. rex was probably covered in these downy feathers.
This month comes news of a bizarre feathered dinosaur entombed in 75-million-year-old Mongolian rock. The size of a mallard duck, it looks like a cross between a dinosaur and a goose.
For some years the specimen was traded on the fossil blackmarket in Britain and Japan before it fell into the hands of a specialist in Belgium. At first, the specialist thought it was a fake or a well-constructed hoax as it looked like a killer swan, had the skeleton of a dinosaur, teeth inside its beak, wings converted into flippers, large clawed feet, and a lizard’s tail.
A team of Italian specialists have given it the name halszkaraptor (Halszka Osmolska being the pioneer Polish palaeontologist who drew Mongolian fossils to world attention).
Dr Ji’s 1997 discovery forced a revision of the very definition of a bird, which is now defined as ‘‘An animal with flightworthy feathers’’. This taxonomic redefinition had some curious effects. The iconic archaeopteryx, for example, was demoted from a missing link between reptiles and birds to an evolutionary dead-end bird-like dinosaur.
None of these three dinosaurs could fly, as their feathers were the wrong shape. Not until dinosaur feathers became flightworthy did true birds evolve. Once birds were airborne they evolved quickly. Within a few million years, crowsized birds had shrunk to the size of sparrows, and they had developed good perching feet.
Some fossil dinosaur therapods discovered in the Ureweras and on the Chatham Islands were, like many of their family overseas, probably once covered in feathers.