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Wednesday, 24 April 2013

They're reptiles Jim, but not as we know them

A couple of Therizinosaurus cheloniformis in a Cretaceous woodland,  one of whom is making the loudest 'coo coo' noise you've ever heard, and one of whom couldn't care less.
There is no 'saur like a therizinosaur. That should be a well-known saying among palaeontologists, but it's not. They're all too busy doing science to come up with silly puns, no doubt. This painting of these magnificent animals came as a response to my previous post concerning 'Feather Resistance' (the fact that some people just don't like the idea of feathered dinosaurs) which featured a photo of the feathered remains of the small Chinese therizinosaur Beipiaosaurus. The neck vertebrae of this specimen thread through an extensive, posteriorly-expanding wedge of neck feathers in a fashion very reminiscent of diagrams of pigeon anatomy that we've all seen in textbooks, and it's fairly easy to see where my mind went from there (makes a change from all the cassowary-inspired paleoart on the internet, a trope which I'm guilty of myself). The composition of the image is something of an homage to the brilliant Crystal Palace sculptures constructed by Benjamin Waterhouse Hawkins between 1852 and 1855. Many species reconstructed by  Hawkins were shown with individuals in both reclining and standing poses, often with the standing animals looking rather more spectacular than those resting alongside. You can see this arrangement in several dioramas, including his famous Iguanodon, as well as his pterosaurs, Anoplotherium, Palaeotherium and Megaloceros (see below). I've always thought this enhanced the believability of Hawkin's work, showing his reconstructions as individual animals with distinct attitudes and personalities rather than species which simply engaged in one activity. Their poses are also frequently enhanced with the local topography, giving the impression the more active animals have ventured to higher ground to survey their surroundings or intimidate their audience. There's a lot to like about Hawkins' work and I think we may overlook him somewhat when considering the Great Palaeoartists, but that's a story for another day.

A gypsy-russel of Hawkins Crystal Palace sculptures, showing his flair for juxtaposed reclining and standing animals. Clockwise from left, Anoplotherium; Megaloceros (including bonus imagery of pterosaur researcher Michael O'Sullivan); Pterodactylus(?), and Iguanodon. If you've not visited these sculptures but are reading a blog like this one, you owe yourself a visit to Crystal Palce. Photos by Witton.

Behind the lousy wordplay attempted above lies an element of truth: is there a group of dinosaurs that undermines the classic concept of dinosaurs more than therizinosaurs, the feathered, pot-bellied, herbivorous theropods? Perhaps more than any other group, therizinosaurs highlight how much our understanding of dinosaurs has progressed not only since Hawkin's day, but even within the last few decades. Dinosaur concepts of the  1980s and 1990s stressed the more reptilian aspects of their nature, even in light of the undeniable birdiness of dromaeosaurs and other maniraptorans. Back then, dinosaur books and television shows presented lizards and crocodiles as the best modern analogues for dinosaurs, and birds were only mentioned as distant dinosaur relatives. We were told that dinosaurs weren't just reptiles in the taxonomic sense, but were reptilian in terms of their appearance and lifestyles, which echoed sentiments expressed as  long ago as the early 1800s. As we all know, early concepts of dinosaurs saw them as little more than gigantic super-reptiles, an idea best embodied by the models discussed above (and shown again, below), which were clearly primarily generated by wrapping modern reptiles around a few dinosaur fossils.

What's in a name?
Despite the advances in our concept of dinosaur palaeobiology since Hawkins' superlizards first roamed south London, we still use reptiles as modern points of reference for dinosaurs. If asked to concisely summarise Dinosauria in a single sentence for a lay audience, most of us would use the word 'reptile' somewhere. But, strange as it may seem to say, it doesn't really make much sense to introduce dinosaurs as 'reptiles' any more, and I think we do out of habit rather than good reason. Taxonomically speaking, the word 'reptile' is somewhat nebulous, with different definitions depending on its use. If you're old fashioned, you may define Reptilia as an artificial group containing all amniotes which are neither mammals or birds, but that doesn't work for dinosaurs as it excludes birds. Others would take the word 'reptile' as indicating most members of 'Sauria', a natural group containing all amniotes except for the synapsids. That's fine, but Sauria is a big and diverse group, so labelling dinosaurs as 'reptiles' is an incredibly loose taxonomic address. It may have worked several decades ago, when concepts of reptile evolution were pretty murky, but not in today's world of cladograms and robust sauropsid phylogeny. Introducing dinosaurs as reptiles is correct, but not very informative. It's also inconsistent with the way we describe modern dinosaurs. We don't typically introduce birds as a group of reptiles: they're simply a type of animal. Why aren't other dinosaurs just described as 'animals' then? It seems that introducing dinosaurs as reptiles is either wrong, imprecise or inconsistent with the way we treat modern dinosaurs.

Hawkins' awesome model of a super-reptile Megalosaurus. Note the modern dinosaurs at the top of the photo, which give me an excuse to link to this. Photo by Witton.
Compounding this is the fact that, anatomically speaking, modern reptiles aren't a great match for dinosaurs, and there is an obviously superior alternative. Sure, many dinosaurs were scaly-skinned, terrestrial animals which laid eggs, so the 'reptile' reference still has some merit, but modern birds are far closer anatomical and behavioural analogues to Mesozoic dinosaurs. Birds also offer scaly skin, terrestrial habits and egg laying to dinosaurs, as well as filamentous integuments, rapid growth, extensive systems of air sacs in the body and neck, erect stances, long necks, and long limbs with digitigrade extremities (among many more detailed aspects of their anatomy). Because of this, we're all pretty happy that Mesozoic dinosaurs were a lot more like birds than lizards, snakes or crocodiles, but we still preferentially mention reptiles rather than birds when introducing the group.

So why is the word 'reptile' at the heart of our basic concept of Mesozoic dinosaurs, when using birds as an immediate point of reference would make more sense both anatomically and taxonomically? Maybe it's simply because the word 'reptile' got there first. The reptilian nature of dinosaur fossils was appreciated before their birdiness, so we labelled them 'fossil reptiles'. And it stuck. We probably would not be in this position if the first dinosaur discoveries had been of deinonychosaurs, oviraptorosaurs or another, obviously bird-like species, rather than fragments of megalosaurs or ornithischians. What if evidence of feathered non-avian dinosaurs had been available to early dinosaur workers? It could have happened that way. Feather impressions are now known to occur in multiple fossil sites around the world, including some deposits which may not, at first, seem likely to preserve them. Even in sites where feathers do not preserve, the forelimbs of some dromaeosaurs preserve feather-anchoring quill knobs. It's not inconceivable, therefore, that the birdiness of dinosaurs could have been revealed much earlier on in dinosaur research history, and that the concept of dinosaurs as fossil reptiles may never have been established. Perhaps, given how essential the reptilian nature of dinosaurs seems to their popularity, dinosaurs would never have become anywhere near as popular if this version of history had played out. Just think: we may never have had Jurassic Park.

So there we have it, then: introducing dinosaurs as reptiles is a bit silly but, like a lot of language, we stick with it because of its established nature and ease of use. With hundreds of years of momentum behind this idiosyncrasy, I doubt we'll ever see dinosaurs labelled as anything else. However, that's not to say that educators or science communicators wouldn't benefit from occasionally tweaking the way that they introduce Mesozoic dinosaurs to their audiences. Perhaps replacing the word 'reptiles' with 'bird-relatives' every now and then will jar a few minds awake, and especially if said educators are trying to put some distance between modern dinosaur concepts and those of the past.

Friday, 19 April 2013

Pterosaurs will launch this Autumn


Get out your diaries, calendars and stone circles to set a date, folks: Pterosaurs: Natural History, Evolution, Anatomy (or P:NHEA, presumably pronounced 'ne-ah', what with the silent 'P' and all) is scheduled for a launch event at the Natural History Museum, London, on September 10th of this year (2013 for those of you in the future, reading this in your flying cars. How about you pay attention to the road instead of reading this, flyboy?). We're still putting together the details of what the launch will entail, but expect at least an evening lecture and probably some drinks after, either at the NHM or at an adjacent emporium.

The event does, of course, take place some time after the book will be available, which you already know is June 23rd. While we lose the element of surprise with the September date, it does give you plenty of time to order a copy so you can bring it along to get it signed by the author, making it marginally more valuable for when you decide to sell it on Ebay. The image above is another teaser for the content of the book, showing one of the 23 combined life and skeletal reconstructions that accompany the latter section, all of which are displayed in a quad-launch pose (book launch/quad launch... geddit?). This particular one shows Tupuxuara leonardii, a thalassodromid pterodactyloid from Brazil with a 4 m wingspan. Half of the image has already made it onto the Intertoobs, where it christened my Pterosaur.Net blog post on working as a palaeoartist, but you can now see the skeleton underlying the soft-tissues. It's largely based on the near-complete T. leornardii specimen IMCF 1052, with some assistance from other thalassodromid specimens to fill in the missing bits.

And finally...
In further PR related news, I've recently become a citizen in the land of Twitter, where you can follow me at the imaginative moniker @MarkWitton. My feed promises to relay all manner of pterosaur and palaeo news, blog updates and shiny new bits of art. Or maybe I'll just moan a lot about things. Or a bit of both. See you over there, in any case.

Monday, 15 April 2013

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 WilloughbyJohn 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?

Thursday, 4 April 2013

Phat Air meets wide gauge

So, here's something you don't see every day: giant azhdarchid pterosaurs and sauropods, living together in peace and harmony. Well, living together, anyway. This azhdarchid looks like a bit of a jerk, what with his swooping down to buzz the local titanosaurs for no obvious reason. They don't seem to like him very much. 

We can be confident that giant azhdarchids and gigantic sauropods once coexisted. Both are known from Maastrichtian age rocks in North and South America, and two celebrity Mesozoic species, the famous titanosaur Alamosaurus sanjuanensis and giant azhdarchid Quetzalocatlus northropi are denizens of the  Javelina Formation of Texas. Newly discovered vertebrae of Alamosaurus have boosted its maximum size estimates considerably, demonstrating it attained similar proportions to the gigantic titanosaurs of South America, Argentinosaurus and Puertasaurus (Fowler and Sullivan 2011). But while we can be certain that these giant animals occupied the same landscape, there's a lot of slop in trying to reconstruct them. Accordingly, I should stress that the animals depicted here are fairly generalised because, hand on heart, we don't know much about their appearance at all. Even basic attributes like their overall size are difficult to pin down. I thought Fowler and Sullivan (2011) were sensible for not including some shonky estimates of length or mass in their recent work on the new giant Alamosaurus material. Being simply content to say it was 'as big as Argentinosaurus and Puertasaurus' and 'among the largest sauropods in the world' works for me. Mike Habib and I took the same approach for the giant pterosaur Arambourgiania in our 2010 paper on giant pterosaur flight (Witton and Habib 2010). Arambourgiania is a probably the least known giant pterosaur among laymen, and is only represented by a few scrappy bones from Maastrichtian deposits of Jordan. The most impressive and discussed of these is its incomplete, 660 mm long neck holotype vertebra. But how does that link into the rest of its anatomy? Despite the propensity and popularity of reconstructions of giant pterosaurs, the truth is that we actually have very little idea of their dimensions and scaling regimes. Even the widely reported 10 m span for Quetzalcoatlus northropi is based on (unpublished) extrapolation from an animal half its size. Accordingly, it's difficult to say for certain how large Arambourgiania was, other than that it clearly had a very long neck (2.9 m is my most recent estimate for the combined length of Arambourgiania cervicals III-VII) and was probably among the largest pterosaurs we know of. That's not as cool as saying we know it spanned 11-13 m or whatever, but it's probably more honest.

Size is, of course, only one aspect to consider. Specific proportions and anatomies are pretty much impossible to reconstruct for many giant species, so I figure there's no point pretending that we really know what they look like. In 99% of cases, we're better off not kidding ourselves by saying "I'm painting [precise giant species]", but instead just acknowledging that we're rendering fairly generalised giant variants of their probable anatomy until we can refine them with new fossil data. 

Righto, blogging time is over. Back to work.

References
  • Fowler, D. W., and Sullivan, R. M. 2011. The first giant titanosaurian sauropod from the Upper Cretaceous of North America. Acta Palaeontologica Polonica, 56, 685-690.
  • Witton, M. P., and Habib, M. B. 2010. On the size and flight diversity of giant pterosaurs, the use of birds as pterosaur analogues and comments on pterosaur flightlessness. PLoS One, 5, e13982.