Pterosaur Perils!

Posted by Nima On Thursday, July 30, 2009 13 comments

Here we go - drawing pterosaurs the Paleo King way!

I thought I was going to be too busy to finish this for the ArtEvolved gallery, but I have, not one but THREE smokin' hot pterosaur restorations finished (better late than never lol....). I wanted to do more but I figured three high-grade ones are better than ten crappy ones any day.

Now pterosaurs are not my number one area of expertise, but I do know them better than a lot of other creatures (say, for example, Anomalocarids!)

So I had to do a lot of extra research before drawing these guys accurately. And along the way I perfected what you might call "accurate guesswork" - that is, inferring likely proportions of parts of animals based on their close relatives - with a good dose of personal aesthetic appeal thrown in. With some pterosaurs little is known but the skull, and with others good skeletal diagrams are not always available, so educated guesses are more necessary than with stuff I'm more familiar with. I am one of the few people willing to reconstruct a poorly known species in great detail, but I'm not gonna lie, it's anything but easy going.

Soon as I get started on titanosaurs this will become obvious. As for the pterosaurs.... guesswork and interpretation are everywhere.

Wing membranes are the main point of contention - did they attach to the leg, the ankle, or somewhere else? After a lot of debating (which you can see on ArtEvolved) and consulting as many sources as I could find, I settled on the efficient design proposed by Gregory S. Paul - wing membranes attached to the tail, with the legs having their own individual membranes. With Pterodactyliods, this is a good explanation for why the tail was reduced but not lost altogether.


Female Pteranodon "ingens" skeletal by Gregory Paul. The classic large crest was only present in the males.
Note the free legs and how the wing membranes attach to the tail - which wasn't useful for much else.


Of course the ankle-attachment faction will cite this or that fossil, but in the debates I established that none of their evidence is 100% conclusive, and it can in fact be interpreted many different ways (though this provoked some very heated opposition). Membrane stains in slab fossils are often something else entirely. Not every stain is even part of the animal. But many of them do look like squashed skin that was once attached to the tail. Needless to say, this would also make steering easier, whether the tail was used to steer, as in most Rhamphorhynchoids (excluding Anurognathids) or whether steering was done with the legs as rudders (as was likely in pterodactyloids). Ankle attachment works fine for bats, but it would likely be a clumsy, restrictive, and highly maladaptive system for pterosaurs, whose wing anatomy and lifestyle were in fact VERY different from bats.

So with some exotic choices for the creatures and settings, here are the pictures!




Thalassodromeus and other mid-Cretaceous pterosaurs over South America

Though Thalassodromeus was from Brazil, it's likely that it migrated long distances in search of feeding grounds and mates. Here they're flying over Argentina, overshadowing giant ornithocheirids flying below. A few Tapejara fly in the background near the mountain, while the ground is dominated by a herd of massive Argyrosaurus. (I plan to draw the 90-foot long Argyrosaurus as the main subject in a later work, which will definitely be a king-sized challenge).

I was fascinated by Thalassodromeus the moment I saw a picture of it (I think it was the one by Dr. Mark Witton), and I figured it was definitely on my list of pterosaurs for the gallery. This pterosaur has a gigantic head - the beak is deep and there's an obscenely huge crest. Thalassodromeus is a tupuxuarid, and unlike their relatives the tapejarids, they have crests of solid bone rather than a membrane supported by bony struts. The head was light and had low bone density, but still looks disproportionately large. The crest was almost certainly for sexual display, though it may have had some use for steering as well. Like many later pterodactyloids, this guy had no teeth, and was probably a fish eater - though whether it preferred freshwater or saltwater prey is impossible to tell.





Quetzalcoatlus - Sailors of the Sky

Here, some of the last and largest pterosaurs soar over a flooded river in Late Cretaceous New Mexico, passing over three Alamosaurus. I actually began this drawing almost 8 years ago as something to pass the boring empty hours between final exams and summer vacation, and it lay unfinished, hidden in a book... when I rediscovered it I decided to complete it but noticed that the arm proportions on the Quetzalcoatlus were ALL WRONG. So I plunged into several skeletals and papers on giant azdarchids and other large pterosaurs and figured out some more or less accurate proportions for the segments. I went for tail attached rather than ankle attached wings. No complaining, it makes more sense this way! I still think the legs didn't quite come out right, but overall I'm pleased with the look. The toughest part was by far the landscape - after all the time I put into the pterosaurs, the landscape commanded a lot more detail and shading.

Aside from the unique color patterns, these are pretty much your standard Quetz's. The top view was a bit tricky (grrr... projects that require perfect symmetry...) but I'd easily do it again now that I have more experience. I gave them small crests near the back of the head, which is consistent with the remains. Artists used to draw Quetz's without a crest, until Greg Paul and others corrected this trend in the '80s. (You can check out Greg Paul's Quetz here, fending off a tyrannosaur). Quetzalcoatlus had a small crest (which is mostly broken on the type skull, leading to the initial error), not a huge one like Pteranodon or Nyctosaurus.





Anurognathus ammoni - the Definitive Version

I've seen a few different illustrations of the tiny Jurassic pterosaur Anurognathus - all of them very different, and NONE of them looked like Anurognathus! I've seen this little guy drawn as a prehistoric bat (by Dr. Mark Witton and MANY others), a flying toad (no, I'm not joking), a winged shrew with the face of a seal, a vampire-like creature with bloodshot eyes (thank you Mr. Bogdanov), and an odd chimera of filaments and fanciful outgrowths not found in the fossils (*cough* David Peters *cough cough*).

Long story short, none of these drawings looked anything like the real animal, so I decided to do my own restoration - not to brag but this is probably the first HIGHLY ACCURATE life restoration of this critter anywhere. I consulted Mike Hanson's skeletals as the main reference for proportions, though I added a few of my own touches such as the membrane shape and the skull proportions (which have been interpreted at least 2 or 3 different ways due to the skull being badly squashed in both known specimens as well as close relatives Jeholopterus and Batrachognathus - I tried for a compromise between the skull proportions restored by Hanson and those from other skeletal artists). I also put some fuzz around the ankles which is apparent on Jeholopterus and was likely also present on Anurognathus. Same goes for the whiskers preserved in the same fossil. Anurognathids all had very long whiskers, presumably for sensing air movement and catching insects. This feature is not found on any other group of pterosaurs.

The wings attach to the tail, and interestingly unlike other rhamphorhynchoids, the anurognathids had short stubby tails - a trait converging on the more advanced pterodactyloids. Anurognathus was probably a fast and highly agile flyer which used its leg membranes for steering rather than relying on a long rudder-like tail. This design also made it capable of zig-zagging through tight spaces in dense Jurassic forests. Based on its small size and pointy teeth, it lived mostly on bugs, though it may have also gobbled up the occasional Jurassic fruit here and there. Like many insect-eating birds today, some cryptic coloration was probably present. The wing pattern turned out a bit too much like giraffe spots, but I ended up liking it.

***

I didn't put any progress pics or "making of" stuff because there just wasn't enough time to scan all the stages, and I was working on all three of the projects at once. However, just by looking at them I'm sure at least a FEW of my artistic secrets may reveal themselves to the insightful.


New Material - Australian titanosaurs!

Posted by Nima On Friday, July 24, 2009 10 comments

I know this is a bit late in coming, but as pterosaurs consumed most of my attention, I almost missed this exciting piece of news.

Three new species of dinosaurs have been discovered in Australia and described in a groundbreaking new paper! And two of them are giant sauropods of the titanosaur sort- and they provide a lot of useful information for restoring these often poorly understood giants. Most of all it will be a lot of fun to draw these creatures. Sauropods never cease to fascinate, and titanosaurs are by far the most interesting of them all.

Meet the new giants: (in vertical order)


  • Australovenator wintonensis, an allosauroid possibly close to Carcharodontosauridae;
  • Wintonotitan wattsi, a basal titanosauriform (though the hand material in the paper looks like a true titanosaur);
  • Diamantinasaurus matildae, a lithostrotian titanosaur.

Scale bar = 2m (I think..... so then the Allosaur would be ~30 ft (10m) and the sauropods would both be around 80-90ft. Pretty impressive! Those of you who want to see the entire paper can download it for FREE right here. Of course the guys at SV-POW beat me to it (here's their post on it if you haven't already seen it.)

Now as much as I like these preliminary restorations, I know the artist could have done better. I can do better. There are several anatomical errors in the painting and the titanosaurs don't even look like convincing titanosaurs (not even by the over-simplified standards of Ken Carpenter and many others in the field who assume every titanosaur looked like Saltasaurus [credit: Brian Franczak]).

Now check out some of the gorgeous fossils - here's the hand of Diamantinasaurus:




All four views show the titanosaur's right hand. C and D show it with the associated thumb claw and a mirror-replica of the first metacarpal based on the one found with the left hand (the one for this hand was missing).

Did I just say thumb claw? Yes. The authors of this paper make a convincing argument it's authentic. And the hand includes phalanges. This specimen goes a LONG way towards clearing up the confusion among lithostrotian titanosaurs.

I think we are beginning to see good evidence that highly derived titanosaurs DID indeed retain their thumb claws and phalanges, instead of losing them as was long believed. The enlarged bottoms of the metacarpals indicate that the phalanges were actually quite well-cushioned with cartilage and used to support the creature's weight. Indeed, it may be the loose phalange attachments of titanosaurs that led the phalanges to often be washed away, resulting in things like Opisthocoelocaudia, which APPEARS to have no phalanges, but the type specimen is simply missing them as a result of incomplete sedimentation or decomposition (plus, the skeleton appears to have been scavenged, so it was probably still exposed and the soft tissue was likely decomposing for a while before the whole thing was buried in sediment, which explains the loss of the phalanges and thumb claws...)

This also fits with Janenschia, one of the oldest titanosaurs, having thumb claws (painting by Andrey Atuchin).

Here's the pelvis of Diamantinasaurus. MASSIVE!




By the way, thanks to everyone that participated in guessing the identity of our mystery dinosaur. It is Dacentrurus. Congratulations to Darthsantuzzo for getting it right!

I figured the scale bar would make it pretty obvious, though this creature is not as widely known as I expected - Dacentrurus is the only stegosaur other than Stegosaurus itself to reach a length of 9m (~3o feet). Which is ironic considering that John Sibbick and many other artists often illustrate it as a much smaller dwarf species along the lines of Lexovisaurus or Kentrosaurus (Sibbick's Dacentrurus is the all-spiked creature on the bottom right - the spikes themselves are inaccurate).

The Dacentrurus project is well under way, but first the pterosaurs will have to be finished. Stay tuned for more soon.