In his new book The Tyrannosaur Chronicles, palaeontologist Dr David Hone tracks the rise of the most famous dinosaur in the world; Tyrannosaurus. Here, her explores some of the most recent research into the secrets of their biology, from feathers to cannibalism.
Arguably the most famous of the long extinct dinosaurs are the tyrannosaurs – the evolutionary group that contains the legendary Tyrannosaurus rex and its nearest relatives. First discovered in 1905, the tyrannosaurs have been a mainstay of popular culture ever since, and have also attracted a great deal of scientific interest with their unusual body plan. The anatomy of the giants like T. rex– a large bipedal animal with an oversized head, bull neck, surprisingly small arms and powerful hind legs – is probably well familiar. Still, there is much more to these animals than large size and big heads, and although science does have a nice habit of progressing and improving our knowledge over time, the dramatic leaps in our understanding of tyrannosaurs in recent years has been phenomenal.
In total there are around 30 known species of tyrannosaur and yet a full half of these have been identified since 2000. This has included quite a range of new forms that are different to the ‘classic’ tyrannosaurs. Early forms, perhaps unsurprisingly, were much smaller than their later cousins and also lagged the oversized head and reduced arms, but some of the earliest tyrannosaurs had large, bony crests on the tops of their heads that likely served as some kind of signalling structure. We have seen the discovery of desert-dwelling animals with long and narrow skulls and in the far north, Alaska has yielded what appears to be a new and dwarf species called Nanuqsaurus. We now have increasingly good records of tyrannosaurs not just from the traditional hotspots of North America and Asia, but also Europe, and with some possible remains from South America and even Australia.
It’s not just new species either, new specimens of already well-known animals or re-examination of specimens in museums are adding still more to our knowledge. Recent discoveries have included some very small and young specimens of Tyrannosaurus and there’s an almost complete young Tarbosaurus (a Mongolian relative) found which gives us exciting new information on how these animals changed as they grew. Like early tyrannosaurs, the young of the later giants lacked the big heads and associated bone-crushing bite of their adult counterparts, suggesting they hunted and fed in a different way. Perhaps these animals filled different ecological niches as they grew effectively taking the space of several different carnivorous options over time as they went from 1 m long hatchlings to 12 m long beasts.
We also have a much better idea of how, and what, these animals were biting. Various bones of other dinosaurs have been found with various bite marks in them from tyrannosaurs, and even some with tyrannosaur teeth wedged into them that show signs of healing – these animals survived tyrannosaur attacks. Other dinosaurs were not the only victims, there’s evidence of cannibalism between tyrannosaurs, including a Tyrannosaurus toe bone with bites on it. And it wasn’t just what they were eating that got bitten. Numerous tyrannosaurs show evidence of healed bites on their snouts suggesting these animals fought each other perhaps even in ritualistic combats over territory or mates.
Perhaps the biggest change in our understanding of the tyrannosaurs has been the discovery of feathered tyrannosaurs. In addition to the numerous bird-like dinosaurs that have now been discovered with feathers, two different species of tyrannosaur have now been recovered with evidence of feathers including the 1 ton Yutyrannus, and it’s likely all of them had at least some feathers on them.
New discoveries and new techniques and ideas will always continue to help improve our understanding of extinct animals, but the tyrannosaurs are perhaps first among equals. They are as popular with researchers as the public and that means that more research has gone into these animals than any other ancient dinosaur group. This in turn makes them ideal candidates for further study since we know more about them. Even so, our knowledge of these ancient and fascinating carnivores is increasing ever more rapidly and it is an extremely exciting time for tyrannosaur biology. Long may it continue.
The Tyrannosaur Chronicles by David Hone will be published by Bloomsbury Sigma on 21 April 2016.