What pterosaurs tell us about the evolution of feathers

2011 PR image for the 2014 description of Laquintasaura venezuelae, a basal ornithischian from Venezuela. Scales were the requested integument for this reconstruction, but how does that decision hold up today?

For the last two weeks I've been revising an image of the Jurassic ornithischian Laquintasaura venezuelae. The original (above) was produced in 2011, but a request to include it in an upcoming book was impetus to tidy up the art and update the anatomy. One significant question for updating this old piece was whether the animals should stay scaly or receive a coat of filaments. The systematic placement of Laquintasaura isn't certain, but it seems to lack features allying it to major ornithischian clades and, for now, is simply considered a basal member of Ornithischia (Barrett et al. 2014). This puts it in a controversial spot as goes interpretation of dinosaur integument: scales, filaments, or a mix of both?

The origins on filamentous integuments and feathers in reptiles remains an ongoing source of fascination and investigation for palaeontologists. It has been known that filamentous reptilian integuments extend deep into geological time since the 1800s, but research into these structures exploded in the 1990s and 2000s when fossils of many non-avian theropods - seemingly all coelurosaurs - were found adorned with feathers or filamentous feather precursors. Soon after, recovery of quills, filaments and strange, fibrous scales in ornithischians made a reality of once speculative ideas about filaments being widespread across Dinosauria. For years now, palaeontologists have been discussing the possibility that theropod filaments and feathers share ancestry with those of ornithischians. One implication of this is that bodies of dinosaur ancestors would be covered in fuzz instead of, as traditionally supposed, scales. Unravelling this conundrum is of key interest to those attempting to understand ancient reptile evolution and physiology, as well as for artists wanting to know how to credibly restore early dinosaurs. However, integument preservation, and particularly filamentous hide, is rare in the fossil record. Much as we might want to, we currently have insufficient data about the skin of early dinosaurs to address this issue directly.

All is not lost, however: some insight into dinosaur filament evolution can be provided by pterosaurs. Flying reptiles and dinosaurs are largely thought to form a more or less exclusive clade, the Ornithodira, which we now recognise as being characterised by a suite of anatomies - not just hindlimb features, as originally proposed - and commonalities of interpreted anatomy: postcranial pneumaticity, upright postures, elevated metabolisms, and filamentous integument. It's the latter which makes pterosaurs potentially useful to understanding the ancestral state of dinosaur skin. It's a little surprising that it's taken us so long to capitalise on this data, since we've had conclusive evidence of pterosaur filaments (we call them pycnofibres) since the 1970s (Sharov 1971). Suggestions that pycnofibres may have been homologous to dinosaur fuzz arrived much later, in the 2000s, when the evolutionary depth of dinosaurian filaments had become apparent and new discoveries of fuzzy pterosaur fossils were being reported (Czerkas and Ji 2002; Ji and Yuan 2002). Perhaps it was the coincidence of these events, the realisation that filaments were widespread in Pterosauria, and increased confidence in the sister relationship between dinosaurs and pterosaurs which lead to this idea finally being proposed.

Late Jurassic pterosaur Sordes pilosus, described in 1971, was one of the first pterosaurs confirmed to have a filamentous body covering. But are pterosaur filaments tied to those of dinosaurs, or independently evolved?

Studies into pterosaur and dinosaur filament homology remain thin on the ground, and much of what has been said thus far is reliant on gross filament morphology. Earlier this year, a team of researchers (Barrett et al. 2015) tackled the issue of ornithodiran filament evolution quantitatively, estimating the likelihood of homology between theropod, ornithischian and pterosaur integuments via their distribution on the ornithodiran tree. Using 18 different variations in methods, calculations and data values, they predicted the likelihood of ancestral integument states in dinosaurs and ornithodirans: were they scaly, filamentous, or feathered? The result, announced in not only the paper but also a subsequent media release, was that 12 of those 18 assessments suggested scales were ancestral to ornithodirans, and the filaments seen in pterosaurs, ornithischians and theropods were derived independently from a common scaly ancestor.

This conclusion was undoubtedly surprising to some and, indeed, a clear caveat accompanies it: scaly ancestral dinosaurs are "sensitive to the outgroup condition in pterosaurs". Support for ancestrally-scaly ornithodirans relies on the assumption that pterosaur ancestors were also scaly. This condition assumed for 50% of those 18 assessments to account for uncertain ancestral condition for pterosaur integument. In the 9 analyses where pterosaurs were treated as wholly filamentous - and thus consistent with what we see in existing pterosaur fossils - six returned results indicating an ambiguous scaly/filamentous ancestral condition for ornithodirans and dinosaurs, and only 3 supported a wholly scaly interpretation. Of those six 'ambiguous' results, most reported a strong likelihood of ornithodirans being ancestrally filamentous, and many gave dinosaurs a good chance of being ancestrally filamentous too. Moreover, treating pterosaurs as filamentous has knock-on effects through the dinosaur tree: suddenly, there are reasonable, or at least equivocal, chances that ornithichians and saurischians were also ancestrally filamentous. This is a different conclusion to the straighter story of ornithodirans and dinosaurs simply being ancestrally scaly.

What influence do fuzzy pterosaurs have on dinosaur skin evolution? Seemingly, quite a bit. The tree on the left shows integument likelihoods (pie charts) where pterosaurs are considered scaly, tree on the right shows a filamentous analysis.  Modified from Barrett et al. (2015).

Clearly, the crux of all this is the assumption that pterosaur ancestors were scaly: just how defendable is this? Because we know little about pterosaur origins, it's hard to say anything conclusive about the evolution of pterosaur integument with our current fossil record. The stratigraphically oldest pterosaur fossil with pycnofibres is from Middle/Late Jurassic deposits, and thus about 50-60 million years younger than the oldest pterosaur fossils - little help in determining if the first pterosaurs were fuzzy. Ongoing disagreements over pterosaur phylogeny complicate attempts to estimate the appearance of lineages with confirmed pycnofibres. Some schemes (those derived from Kellner 2003 and Unwin 2003) suggest pycnofibres must have appeared by the Triassic, close to or at the base of pterosaur ancestry, but others (e.g. Andres et al. 2010) indicate pycnofibres reliably extend no further than the Lower Jurassic. Of course, such assessments of filament distribution might not even be meaningful at this stage, given that pycnofibres are very rare components of pterosaur fossils. They are nowhere near as common as other soft-tissues, such as wing membranes, and we should probably be cautious about any assessment of their evolutionary pathways until we have more data. Perhaps the only significant observation we can make from our current, limited dataset is that, to date, no pterosaur is known with a scaly body covering, even when regionalised scalation - foot pads - preserves in their fossils (Frey et al. 2003).

A possible pterosaur relative with scaly hide is known: the Triassic archosaur Scleromochlus taylori. Benton (1999) described structures interpreted as thin, transversely orientated scales across the back of multiple specimens of this animal. This might provide vindication of the scaled pterosaur ancestor model, but, again, there are some caveats with this idea. For one, Scleromochlus fossils are not well preserved. The scales are feint sediment impressions, visible only in strong, low angle light, such that that they are only considered 'probable' integument impressions by Benton (1999). Previous workers have interpreted them in a different way (as gastralia). Clearly, the evidence for them being scales could be more compelling, and there's certainly not much to work with if we want to test their identification. Secondly, exactly how Scleromochlus is related to pterosaurs is not precisely agreed. Some workers consider it the sister taxon of Ornithodira, others as a member of the pterosaur branch, and others see it as more closely related to dinosaurs than pterosaurs. That might seem a minor issue, but we've already seen how sensitive models of ornithodiran integument are to changes of single variables at the base of the tree. We would probably need to run many variants of the integument probability calculations to account for all the uncertainty surrounding Scleromochlus. This might give more idea of the range of possible integuments at the base of ornithodiran evolution, but that's not much of an improvement on our current situation.

Was Scleromochlus taylori scaly? Maybe - weakly preserved structures on several specimens seem to suggest so. On this diagram, from Benton (1999), possible transverse scales can be seen on the left and middle specimen.

In all, I feel like we're hitting a bit of a wall here. It seems we just don't know enough, and have too many caveats with the limited data we have, to make even a half convincing best guess on this. Thus, how much weight we put on models of ornithodiran integument using scaly pterosaurs is almost a philosophical issue. From my end, I don't think they should be used to argue for scaly ornithodiran and dinosaurian ancestors, at least not with the same weight as tests made using a filametnous pterosaur lineage. When reconstructing ancestral states, characters objectively observed in fossils have to trump assumed character states, even if we know that our dataset is full of holes. After all, the whole point of attempting to figure out an ancestral state is establishing links between character data we have, so introducing opposing character states seems a little contrary to that objective. To be clear, I'm not saying that running models with scaly pterosaur ancestors is a waste of time. To the contrary, it's a good test of model robustness, and Barrett et al. (2015) certainly demonstrate how sensitive our models of ornithodiran integument evolution are by using this approach. Their hypothetical scaly pterosaurs demonstrate that we really do need more early ornithodiran fossils to understand ornithodiran skin evolution. However, I do not think that results of the scaled pterosaur analyses are as informative as their other assessments, as we have to overlook existing data to consider them equally valid.

With all that said, do pterosaur fossils really help us understand the evolution of dinosaur filaments? Playing the conservative card here, it seems they do not provide super strong evidence for an all-fuzzy Dinosauria, but they certainly make it difficult to defend ideas of entirely scaly dinosaur ancestors. Forcibly arguing for either scales or filaments at the base of Dinosauria seems premature at this stage, and, whatever our personal hunches are, it seems sensible to accept some ambiguity in this situation for now.

I began this article with my Laquintasaura conumdrum: how did that play out when, apparently, I can't make up my mind about this scales and filaments debate? Well, I've argued elsewhere that palaeoart can do no better than illustrate credible interpretations of the past and that, so long as the hypotheses they depict are sound, they're doing OK. When we have conflicting or ambiguous hypotheses, we just have to make a judgement call based on our own opinions, gut feelings and interpretations of existing arguments. With my own leaning being towards data showing that scales may not be ancestral to ornithodirans, but also knowing that some dinosaurs are mosaics of filaments and scales, I decided to partially enfluffen my Laquintasaura, while leaving their snouts, tails and limbs scaly. I'll leave you with the revised image.

Laquintasaura venezuelae 2015 edition: basically the same picture, but a bit fluffier, and a bit greener.

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References

• Andres, B., Clark, J. M., & Xing, X. (2010). A new rhamphorhynchid pterosaur from the Upper Jurassic of Xinjiang, China, and the phylogenetic relationships of basal pterosaurs. Journal of Vertebrate Paleontology, 30(1), 163-187.
• Barrett, P. M., Butler, R. J., Mundil, R., Scheyer, T. M., Irmis, R. B., & Sánchez-Villagra, M. R. (2014). A palaeoequatorial ornithischian and new constraints on early dinosaur diversification. Proceedings of the Royal Society of London B: Biological Sciences, 281(1791), 20141147.
• Barrett, P. M., Evans, D. C., & Campione, N. E. (2015). Evolution of dinosaur epidermal structures. Biology letters, 11(6), 20150229.
• Czerkas, S. A., & Ji, Q. I. A. N. G. (2002). A new rhamphorhynchoid with a headcrest and complex integumentary structures. Feathered Dinosaurs and the origin of flight, 1, 15-41.
• Frey, E., Tischlinger, H., Buchy, M. C., & Martill, D. M. (2003). New specimens of Pterosauria (Reptilia) with soft parts with implications for pterosaurian anatomy and locomotion. Geological Society, London, Special Publications, 217(1), 233-266.
• Kellner, A. W. (2003). Pterosaur phylogeny and comments on the evolutionary history of the group. Geological Society, London, Special Publications, 217(1), 105-137.
• Ji Q., & Yuan C. (2002) Discovery of two kinds of protofeathered pterosaurs in the Mesozoic Daohugou Biota in the Ningcheng region and its stratigraphic and biologic significances. Geol. Rev. 48, 221–224.
• Sharov A, G. (1971). New flying reptiles from the Mesozoic of Kazakhstan and Kirghizia. - Transactions of the Paleontological Institute, Akademia Nauk, USSR, Moscow, 130: 104–113 [in Russian].
• Unwin, D. M. (2003). On the phylogeny and evolutionary history of pterosaurs. Geological Society, London, Special Publications, 217(1), 139-190.

The Mysterious Mysteries of Feather Resistance

Three feathered dinosaurs: the famous dromaeosaurid Velociraptor mongoliensis chases a juvenile oviraptorosaur, Citipati osmolskae. The parent of the latter tries to intervene. Prints of this image are available.

So, the Jurassic Park 4 'No Feathers' controversy has continued to roll across the Internet, spilling out from the palaeo blogosphere (notable articles here and here) into mainstream media such as New Scientist, The Telegraph and the New Zealand Herald. As might be expected from such wide coverage, there are a lot of differing opinions about the decision to keep JP4's dinosaurs entirely scaly. As we all know, this decision is at odds with overwhelming evidence that all manner of coelurosaurian theropods, and possibly many other dinosaur species, were feathered. Although much about the film itself remains mysterious, it's director, Colin Trevorrow, has allegedly confirmed his tweet with another tidbit of info about the lack of feathers in the movie. The source for this confirmation has yet to be verified, but if he has, my hopes that the producers may be looking to the Internet to gauge reaction to the idea of feathery dinosaurs were in vain.

But I don't want to talk about that
To me, the most surprising aspect of the discussions over JP4's 'No Feathers' has been the commonality of argument from some contributors. Specifically, there is a body of people who seem to strongly dislike the idea of feathery dinosaurs. We're not talking about people ignorant of fossil evidence indicating that feathered Mesozoic dinosaurs were as real as blue sky and gravity, but those people who personally prefer their dinosaurs scaly, irrespective of fossil evidence. Interestingly, these individuals almost always bring up the same reasoning.

1. Feathered dinosaurs look stupid
2. [linking to some awful tarred-and-feathered reconstruction] "Do we want dinosaurs to look like this?"
3. Feathered dinosaurs aren't scary
4. Feathered dinosaurs look like giant turkeys/chickens/parrots!
5. Feathers equate to bright colours and lurid display structures

I've been wondering if the similarity of these comments suggests a common cause. If there is, it's clearly not informed by modern depictions of feathered dinosaurs. The feathered dinosaurs depicted at the top of this post are pretty typical of modern reconstructions: whether they look stupid or scary is a matter of opinion, but we can at certainly agree that neither is brightly coloured, chaotically feathered, or resembles a parrot. If this is a typical modern representation of feathered Mesozoic dinosaurs, where are the animals suggested by the 'Feather Resistance' resistance coming from? What is the source of these common comments, and, more broadly, why are a number of people still so adverse to the notion of feathered dinosaurs?

Soft touch
Let's start with a possible root cause for Feather Resistance, from deep within the popular characterisation of dinosaurs. Moreso than any other extinct species, dinosaurs are depicted as hardcore 'superanimals'. Ancient, real-world dragons that lived in a turbulent and violent world of volcanoes, sparse, sharp-leaved vegetation and perpetually-hungry predators. We get the impression that our modern fauna wouldn't last two minutes in this time of voracious killer reptiles. If popular depictions of dinosaurs are anything to go by, they were only vulnerable to two things: other dinosaurs, and giant rocks from space. Modern animals, by contrast, struggle when someone redirects a river or we build a new supermarket. Dinosaurs could not only take that, and they'd eat your mother just for suggesting otherwise.

With this in mind, it makes total sense for dinosaurs to have scaly hides. Scales provide tough armour plating. They wrap every dinosaur, big or small, in biker leathers and reinforce their status as the hardcore mofos we expect them to be. This is why we're secretly glad that some dinosaurs are extinct: their enormous power and resilience would be a terrifying force if unleashed in our modern, tranquil world.

Fossil of the feathered therizinosaur Beipiaosaurus, borrowed from here. Note that, like Sinornithosaurus, below, this fossil shows very avian-like feather contours around the neck.

The suggestion from stupid-old scientific evidence that we need to swap the armour and scales of some dinosaurs for soft, strokeable feathers just doesn't sit right with this interpretation. In fact, it undermines the popular concept of Dinosaur Awesomeness, big time. Feathered hides aren't about protection from teeth and claws, but instead lame things like keeping warm, camouflage, display and perhaps locomotion. The sort of things that real animals are concerned with, but that make-believe fantasy animals aren't. Feathers make dinosaurs seem more vulnerable, which makes them harder to idolise and fear. The fantastic interpretation of dinosaurs is alluring to many, while the reality is, by necessity, somewhat less fantastic.

Compounding this perceived loss of awesomeness is the removal of mystery surrounding dinosaurs: their feathered hides make them a lot more familiar to our eyes. Scaly, bipedal theropods are unusual to us: "they look a bit like birds, but they're kind of reptilian". By contrast, feathery theropods, and large fuzzy animals generally, are well known to all, and many modern birds probably look very similar to their extinct, non-avian ancestors. More convincing reconstructions of feathered maniraptorans converge with animals like roadrunners, emus and corvids so much so that they could be mistaken for these modern species at casual glances. Suddenly, most of their mystery is gone. A lot of the appeal with dinosaurs concerns the many unanswered questions we have about their lives and appearance, but if these can be answered - even if only roughly - by pointing at a modern animal, then we'll have satisfied the curiosity of many casual interests in extinct life. Adding feathers doesn't just replace mythical dinosaur badassery with boring-old reality then, but also makes dinosaurs more familiar, and thus more 'boring' to some eyes.

But don't we make all of this up, anyway?
Moving away from imaginary concepts of  dinosaurs towards efforts to reconstruct them in art, we may encounter our second factor in Feather Resistance: a lack of awareness about the fossil evidence used to constrain reconstructions of extinct species. A lot of folks seem to think that palaeontologists and palaeoartists make up dinosaur appearance as they go along, perhaps with a few scraps of evidence to point them in the right direction, but otherwise work within almost limitless possibilities. In such a scenario, personal choice about attributes like integument would play a large role. Of course, this could not be further from the truth. A good palaeoartist reconstructs extinct animals as rigorously as possible, with as much information as possible, using increasingly good fossil data and phylogenetic analyses to inform animal proportions, musculature, integuments, environments and behaviour. A lot of folks would be very surprised at how much data can be obtained from one fossil nowadays, and how much of that can be used to inform a reconstruction. It doesn't seem unfair to say that our dinosaur knowledge is advanced enough now that we can make some inferences about the integument possibilities for most major groups, so there's normally good reason behind the choice for scales, quills and feathers on different dinosaur reconstructions. Much of this work is probably unknown to much of the public, however, who may think that feathers are just fashionable possibilities in a sea of poorly-constrained, speculative artworks.

The learning curve
The points made above may not matter so much, however, if dinosaur PR had convinced us that feathered dinosaurs were still cool, even in their new threads. The need for reconstructing extensive feathering on at least some non-avian theropods became inescapable in the mid-nineties thanks to discoveries of Chinese dinosaur fossils surrounded by fuzzy halos of feathers. As such, feathered dinosaurs have been a mainstay of palaeoart for around 15 years at least. With hindsight, I think we can say that it has taken a little practise to produce convincing-looking reconstructions of these animals. I'll go so far to say that many of the first reconstructions of feathered non-avian theropods were pretty awful, and certainly not reflective of the integument details preserved in the then-new Chinese fossils. Clinging to the once-fashionable concept of shrink-wrapping, many depictions of dromaeosaurs sported lank, greasy-looking feathers draped over painfully skinny bodies, while others wore veritable explosions of fibres and fluff; big, shaggy masses of feathers that drowned the contours of the animals beneath them. Something of a halfway house between these extremes was struck when patches or rows of feathers were set across a primarily scaly body. Interestingly, whichever of these three approaches was used, dinosaur heads were frequently left scaly, despite good evidence that they shouldn't be (check out the feathers on the face of the fossil below, for instance).

Sinornithosaurus, one of the first dromaeosaur fossils known to show extensive feathering across its entire body. Note the very avian-like feather contours around the neck and the feathers adorning the snout. Image borrowed from here.

Irrespective of the technical skill involved, many of these illustrations produced pretty goofy-looking, almost cartoony animals. It doesn't help, of course, that many palaeoartists insisted - and still do - on portraying Mesozoic reptiles in perspective-heavy, hyperferocious postures, leaping or running towards the viewer with mouths agape, teeth exposed and arms outstretched. The garish colour schemes of many reconstructions didn't help, either. The result was an Internet awash with downright weird and freakish feathered theropods, many of which still float about today or are being perpetually copied by illustrators under the impression that they represent plausible models of dinosaur appearance.

With this in mind, it's not surprising that many laymen think that feathered theropods look silly. Many of the more memorable and longest-lived reconstructions of them are, and perhaps these are what most folks think of when the words 'feathered dinosaur' come to mind. Scaly theropods undeniably looked more intuitively plausible, not to mention more aesthetically pleasing, than a lot of the weird imagery once thrown about by palaeoartists. A definitive move away from this craziness can be seen in more recent works, resulting in much more convincing depictions of feathered Mesozoic theropods (check out those by Emily Willoughby, John Conway and Julius Csotonyi for examples). These chaps have clearly gone back to the fossil data, looked at the mechanics and proportions of feathers in modern birds and abandoned overly-dynamic poses to recreate feathered dinosaurs which look like genuine, real animals. Unfortunately, displacing the prevalence of earlier, zanier reconstructions of feathered theropods with more plausible models may not be easy, even with these new artworks. By necessity, the newer, more realistic restorations of feathered dinosaurs are more subdued and muted than the crazier reconstructions that preceded them, so may not make comparable impressions in public minds. Even if these new styles of feathered theropod reconstruction become the norm, we may find it hard to step out of the oddly-shaped shadow set by earlier restorations of feathered theropods.

Playing chicken
The freakishness of some feathered theropod reconstructions may explain why some folks immediately imagine giant, outlandishly dressed birds - parrots, turkeys and the like - when feathered dinosaurs are mentioned. A lot of those brightly coloured reconstructions do resemble these birds more than any others, and their overly dynamic, unusual postures only strengthen these comparisons to birds considered to be a little dim (poultry) or capable of silly behaviours (parrots). I wonder if we could go as far to say that, when used with tight shrink wrapping, the sparse feathering of some reconstructions are also reminiscent of  plucked bird carcasses seen in supermarkets? Either way, although palaeontologists may argue that raptors, ratites and shoebills are ideal kindling for imagining Mesozoic animals, these animals may not have been invoked enough in widely-seen reconstructions to have shaped public imagination. And of course, imagining giant chickens instead of giant birds of prey contributes further to the undermining of dinosaurs as creatures to be idolised and feared.

Real dinosaurs vs. celebrity dinosaurs
Much of what we've covered here could be summed up as a bit of a PR fumble for feathered theropods, and it may seem that a concerted effort by artists and scientists could sway public opinion in coming years. This could be the case, but it will be a bit of an uphill struggle. A century of popular dinosaur books, movies and documentaries have cemented the appearance of some species so solidly that, for some, they have become definitive, final versions. This contrasts markedly with the way that palaeoart traditionally works. Our reconstructions vary with developments in scientific thinking, palaeoartistic fashions and with the individual flourishes of different artists, so it's hard to crystallise definitive concepts of given species. But a popular film, TV programme or book can set the appearance and behaviour of its creatures by making them cool, memorable and iconic, and then spawn a host of imitators which solidify the mould further.

The quill knobs on the ulna of Velociraptor, betraying the presence of large, vaned feathers along its forearms. Image borrowed from here.

Of course, the catalyst for this post, the Jurassic Park franchise, is particularly liable here. The JP Tyrannosaurus and Velociraptor have become well-known movie characters, with expected behaviours and appearances for not just Jurassic Park but any mention of them in other media. Tyrannosaurus is typeset as an unstoppable tank of a dinosaur with an armour-piercing bite. Velociraptor is forever a man sized, cunning hunter. Both have transcended their status as actual animals to share ranks with Pinhead, Dracula and Freddy Kruger. We know how to recognise them and what they're going to do in a given scenario. As with any iconic character, suggested changes to their well-loved formulas are not welcomed. Fans are instinctively wary of change to these animals as they are with alterations to any characters of a major franchise. The fickleness of some fans is mind blowing: remember the ridiculous backlash to Daniel Craig taking over the James Bond mantle because, among other reasons, he has blonde hair?

The upshot of these attitudes is that palaeontologists hoping to make feathery theropods popular have to win over fans of recognisable and marketable characters. This includes convincing television and movie producers that feathery reconstructions are not only more credible, but also as marketable as scaly variants. We have to remember that fans of dinosaur franchises constitute a much greater revenue source than those with interests in credible portrayal of palaeontological science, and they therefore hold a lot more sway with media production companies than scientists ever will. This is where the points made above combine to a critical mass: the push for wider depiction of feathered dinosaurs is being perceived through shonky reconstructions, with a public largely naive to recent palaeontological discoveries, and argues for the removal of perceived awesomeness from well known and loved 'characters'. Palaeontologists singing the praises of feathers are being greeted with the same warmth as someone suggesting that we swap the head of Geiger's Alien creature with that of Alf, or that the next Terminator assassin would look better in a turtle neck and slacks instead of biker leathers.

So, where does this leave us?
The irony of so much Feather Resistance being exposed in the light of Jurassic Park 4 is that a major movie featuring well-rendered, plausible reconstructions of feathered dinosaurs could silence a lot of feather critics. This needs to happen eventually. Feathered Mesozoic dinosaurs are fact. Feathered coelurosaurs, the dinosaurs people are interested beyond all others, are fact. Products and people that do not embrace this are at least 20 years out of date, and, so far as I can see, there is no good reason for staying so far behind the times. Naive concepts of dinosaurs and their world, ignorance of palaeoartistic methods, a dislike of change and the fumbling of early attempts to bring feathered dinosaurs to life are poor reasons to keep popular depictions of dinosaurs decades out of date. How long will it take for people to relinquish the idea that their favourite dinosaurs were scaly, fantastic dragons and accept them, and their feathers, for what they actually were?