This week, the second episode of the much-anticipated new series of the BBC’s Doctor Who saw two of the Doctor’s friends battling a group of Velociraptors on a spaceship (it’s Doctor Who, just go with it). What most excited me about this turn of events in the episode was that clearly the effects artists on the show have been keeping up to date with research on the presence of feather-like structures on dinosaurs like Velociraptor (see image).
Back in 1993, when the Velociraptors of Jurassic Park were scaring the bejesus out of kids (and adults) around the world, it was generally agreed that while species like Velociraptor were ancestors of modern birds, feathers were a classifying feature of birds as a group, and so their dino great-granddaddies didn’t have them.
The idea that birds descended from dinosaurs has been around since Thomas Henry Huxley proposed it after examining the fossils of Archaeopteryx (originally considered to be the ‘first bird’) and Compsognathus, a chicken-sized theropod dinosaur in the early 1860s, and found many corresponding anatomical features. His theory didn’t really take off however, until the discovery and description of Deinonychus (that means ‘terrible claw’ in Greek) a hundred years later. Palaeontologist John Ostrom described skeletal similarities between Deinonychus and modern birds like a fused wishbone, and similarities in the wrist and the pubic bones, which strongly suggested that birds were, in fact, living dinosaurs.
But where did their feathers come from? The place to look is the fossil record, but the problem with determining if a fossilised creature had feathers, or scales or fur, is that these features don’t tend to fossilise very well, being made of more delicate stuff than bone. This is why the ‘clever girl’ Velociraptors in Jurassic Park were shown to just have scaly skin – examples of feathered non-avian dinosaurs had simply not been found in 1993. All this changed in 1998 with the discovery of the Late-Jurassic Liaoning formation in China, and the description of two dinosaurs found there – Protoarchaeopteryx and Caudipteryx. The Liaoning formation is made up of a sediment known as Lagerstätte, a very fine-grained sediment that, conveniently, preserves features like feathers in detail (it was in this same type of sediment in Germany that the original Archaeopteryx fossil was found, along with its feathers).
This discovery was followed by many others, including the description in 2007 of characteristic quill knobs on the bones of a Velociraptor specimen, closely resembling those found in modern birds for attaching feathers.
But the question of why non-avian dinosaurs had feathers remains to be resolved. Many of them are no more than barb-like protofeathers, and their wearers could certainly not have flown. Perhaps they were for insulation – they tend to be found only in the smaller theropods, rather than the larger species like Tyrannosaurus or Allosaurus. Or perhaps they were used for display, much like the frills seen in modern lizards. This is the theory the effects artists on Doctor Who went with, showing the raptors flaring up the barbs along their back and arms when threatening Amy and Riddell.
So to what extent were species like Velociraptor covered with feathers? Did they just have a light covering of barb-like feathers (as we saw in Doctor Who), or were they larger and more extensive, like the full covering of modern-looking feathers seen in species like Archaeopteryx and Microraptor? The jury’s still out. But who knows, maybe by the time Jurassic Park IV comes out (yes, really – it’s due out in 2014), they will have given the raptors, and several of the other dinosaurs, their appropriate feathered jackets. They’ll still be just as terrifying.