If Gideon Mantell was alive today and able to visit various museums throughout the world, then he would be amazed at how much the appearance of his beloved dinosaurs has changed over the years. As he passed the various skeletons and reconstructions, he would wonder how on earth the appearance of creatures such as Iguanodon and Megalosaurus could have changed so much and probably the biggest shock to him would be the reconstructions of dinosaurs with feathers – feathers!
Think about it. How difficult would that be? To Mantell, dinosaurs were simply overgrown cold blooded lizards and, with the knowledge that was available at the time, this was a pretty reasonable assumption. They were seen as great ponderous reptiles, covered in scales, plodding around in the primordial swamps that routinely fought for their lives with tooth and claw. Feathers would never have crossed his mind.
We now know, of course, that Mantell, and all the other early workers, were a long way from the truth although we must also recognise that Richard Owen pointed out that dinosaurs were remarkably bird-like at a very early point in his initial studies. Even after the discovery of Archaeopteryx, feathered dinosaurs were a long way away even though various palaeontologists over the years highlighted the possible relationships between birds and dinosaurs. Without significant evidence of feathered dinosaurs, the majority of palaeontologists, and certainly the general public, recognised the dinosaurs as giant scaly reptilian superstars of the Mesozoic.
However, our perception of dinosaurs has changed. We used to think of sauropods as huge swamp dwellers, theropods as relatively slow moving cold blooded killers, stegosaurs with the brain the size of a walnut and a multitude of other stereotypical analogies. We were all pretty comfortable with this image throughout the twentieth century and dinosaurs remained this way in our minds for a very long time.
But the Renaissance changed all that. Sauropods became fully fledged terrestrial animals, theropods became swift and agile hunters while stegosaurs were suddenly able to turn on a sixpence and keep their flailing tail spikes in the face of their aggressors. Suddenly, other dinosaurs too became active energetic animals and the possibility that they were warm blooded really gathered momentum. The bird/dinosaur link was again brought to the fore and Bob Bakker reconstructed Deinonychus with integument suggesting that they had probably already developed feathers and that we should expect to find fossils of dinosaurs with such a covering. How prophetic that was!
During the nineties, the superb fossil localities in China burst onto the scene and we were (and continue to be) thrilled by each and every new specimen that is announced to the world. These specimens are truly remarkable and confirmed, once and for all, that birds are indeed living dinosaurs and, despite the various protestations of creationists and a few fringe scientists who continue to deny the truth, there can be no doubt as to the bird’s dinosaurian origins.
So far, so good but there has been a casualty in this race to the truth and that is the humble dinosaur with traditional reptilian scales. It appears that nearly every dinosaur is now being looked at for traces of feathers. For example we now have basal ornithischians and basal ceratopsians sporting fuzz, quills and bristles. Every fossilized skin impression is being screened for any signs of a covering that might be considered of feathered origin. This is not a bad thing, of course, but there is now a trend to cover every dinosaur in feathers even if there is only inferred phylogenetic evidence and no physical trace.
Now I am not a “feather denier” – far from it – but I have to admit to a certain sadness as the scaly dinosaurs that I grew up with have slowly been eroded down to almost being of no consequence and of no interest. Brian Switek, amongst others, suggested (tongue-in-cheek I hasten to add) that people such as myself should quit whining and get on with it but they misjudge us.
Those of us who like our dinosaurs scaly appear to be frowned upon – as if we don’t know what we are talking about and that we really ought to “get with it” and rejoice that the dinosaurs are covered in fuzz and feathers. Well that isn’t going to happen – certainly not by me and, I am sure, not for many others.
Again I reiterate that I am just as fascinated with feathered dinosaurs as any of you but I do feel a tinge of sadness every time another scaly lineage is consigned to the palaeo- rubbish bin. And now we have the impressive Yutyrannus and this one is just another step closer to assaulting that bastion of awesomeness – Tyrannosauridae.
I’ll be blogging properly about Yutyrannus at some point in the future but for now let us consider the one important factor about this interesting tyrannosauroid – its size. One of the considerations that many of us have been hanging on to with regards to tyrannosaurids not sporting feathers was size. It seemed likely that big tyrannosaurids may sport integument when they were young to add a protective insulation to their smaller bodies. After a while they would gradually lose this covering as they became adult animals to become fully loaded scaly tyrannosaurs. This was a get out clause for us whilst, at the same time, also accepting that feathers may have been involved at some point during ontogeny.
Yutyrannus has changed all this, and at nine metres long and approaching 1.5 tonnes in weight , is certainly not small and the fact now is that some big tyrannosauroids did indeed display a feathery /fuzzy covering and that the larger, more derived tyrannosaurids are now coming into range. My heart sinks at the thought.
Of course, Yutyrannus is still a basal tyrannosauroid and still possessed fairly large forelimbs with three large clawed digits as opposed to the more derived and reduced sized two digits of tyrannosaurids. It is also Barremian in age (Early Cretaceous – 125 million years old) and was alive at least 40 million years before the appearance of Tyrannosauridae proper. Despite this, and in a phylogenetic context, there is a real chance that proper tyrannosaurids may have at least been partially covered by integument of some form.
We scaly supporters will hang on the fact that Tyrannosauridae is still free of feathers – as far as we know of course. This may very well be a sampling bias since the Liaoning deposits represent a lacustrine environment with very fine sediments that aided superb preservation whilst the traditional tyrannosaurid beds of North America are not. Still, Tyrannosauridae remains an untouched bastion of scalyness - but the walls are certainly crumbling.
Perhaps I can best put it this way. The T.rex in Dinosaur Revolution was awesome. But anybody who saw the dancing Gigantoraptor sequence in Dinosaur Revolution can be left in no doubt – is this the kind of thing you want to see a T. rex perform? Do you really want the ultimate theropods, the megastars of the dinosaurian world - the tyrannosaurs - displaying colourful yet gaudy feathers and dancing like a demented turkey cock?
I think not. Like I said – I know the feathered phylogenetic tooth fairy is rattling the front door of Tyrannosauridae but at least let us enjoy the time that is left for our magnificent fully scaled heroes. And if not, there will always be the ankylosaurs…….