Know When To Fold 'Em

Above: Maximum wrist folding for the theropods studied by Sullivan et al. 2010. Not to scale.

To continue talking about aspects of maniraptoran anatomy that can be a bit vaguely defined in the minds of paleoartists, I'm going to write a bit on the issue of wrist folding. As most of you will know, a major characteristic of maniraptorans is the semi-lunate carpal, the half-moon shaped bone in the wrist that allows the blade of the hand (metacarpal 3) to fold backward toward the forearm (ulna). While this is common knowledge among paleo buffs and artists, what seems to be less understood is exactly how tightly the hand (and in aviremigians, the wing) could actually fold up. I myself have never been too clear on the issue, and there don't seem to be many papers addressing this. But in the last few years, a few papers have come along that can help shed light on the subject. The first was Senter 2006, which studied the full range of motion in the forelimbs of two dromaeosaurs, Deinonychus and Bambiraptor. The second was Sullivan et al. 2010, which examined the range of motion in the wrist of several species representing each major group of non-avialan maniraptorans.

Both papers, however, present geometric data that can come across as a bit inaccessible for your average artist, so I'm going to try to break down their conclusions for those of us who are more visual thinkers. The Sullivan paper, in particular, discusses the degree to which the wrist could fold, but doesn't necessarily provide diagrams or even final angle between the metacarpals and ulna for each species that could be used as a simple reference. I've done my best to translate their findings into the image at the top of this post, using modified skeletal diagrams by Scott Hartman and Jaime Headden.

Above: Anatomy of a maximally folded wing of the Wild Turkey Meleagris gallopavo, modified from Sullivan et al. 2010

The degree of wrist folding is controlled by two wrist bones. The cuneiform, on the inside where the wrist meets the bottom of the distal ulna, provides an inner limit. The cuneiform blocks the hand from actually touching the ulna. The radialae, on the outside of the fold, forms the surface which the wrist cannot fold beyond. This is basically a little process anchored to the tip of the radius where the top part of the hand articulates. The hand can obviously not fold beyond the angle of the radialae, or the animal would dislocate its wrist. Therefore, the angle the articular surface of the radialae forms with the ulna is used as the key factor in determining maximum wrist folding by Sullivan et al. Again, see my interpretation at the top for how their results likely translate into life position.

The results show that in almost all maniraptorans, the wrist could not be folded to the same degree as modern birds (for comparison, see the photo of the turkey wing above, which is at its own maximum folding point). Note that in actual, functional angle of folding in the turkey is 57 degrees between MCII (where the feathers attach) and the ulna. To see how this translates into a live animal, here's a photo of wild turkeys nicely showing the way the feathers fold (photo by D. Gordon E. Robertson, from Wikipedia, licensed):

The wrist is located about where the coverts form the point of a triangle, following the line formed by the border of the the brown secondary (ulna) feathers and white banded primary (metacarpus) feathers. Note that with the wrist folded at a 57 degree interior angle, the feathers (especially the secondaries, which help cover the primaries when folded) are basically stacked one on top of the other with little to no fanning out at the tips. This is because the feathers also have some ability to move at their bases, and can themselves fold relative to their anchor bones through muscle and ligament action.

Looking at the aviremigians in the diagram up top, it is apparent that their wrists could not fold tightly enough to fold the wing feathers to the same degree as a modern turkey. Small deinonychosaurs like Sinovenator and Bambiraptor could achieve close to a 100 degree angle (see image of Bambiraptor wing folding above, from Senter 2006), but larger ones like Deinonychus seem to have lost some of that folding ability, presumably for increased use of the forelimbs in predation. Indeed, if Deinonychus retained long remiges, they would hardly have been able to fold at all, and would have been permanently fanned out (not that this would have gotten in the way of grabbing prey, as Senter pointed out). This lack of ability to tightly fold the wrists may have posed a significant problem for those species with very long remiges, like Microraptor gui. Dave Hone, who was a co-author of the Sullivan paper, discussed alternative ways they could have kept their remiges free of the ground at his blog last year.

In pygostylians, the degree of wrist folding began to approach that found in modern birds. Eoconfuciusornis, for example, could fold its wing to about the same degree as a turkey. Where it gets weird is in the oviraptorosaurs. As I mentioned in my post on the Ashdown maniraptoran, oviraptorosaurs (at least the small basal ones like Caudipteryx) seem to have been capable of folding their wings far beyond what is possible for even many modern birds. It's unclear why this is so, especially as the remiges of Caudipteryx, while clearly for display, are not exactly very long compared to the body. Certainly its wings were much smaller than those of paravians, which would have presumably had more need to fold them up. I've seen this mentioned as possible evidence in support of the hypothesis that oviraptorosaurs are in fact avialans, and that the extreme folding of the wrist was inherited from flying ancestors, though I can't think of where. Sullivan et al. do note that more than folding up the remiges to keep them safe from wear and tear, wing folding is an important part of the avian flight stroke, and it makes sense that it would have become more developed in flying forms.

Anyway, we've only got a handful of specimens that have been specifically studied in regards to the degree of wrist folding, and there may well be exceptions in each maniraptoran group, where certain lineages independently evolved a greater or lesser degree of wrist folding from their ancestors as seems to have happened in therizinosaurs, where the derived Alxasaurus can fold its wrist more than the basal Falcarius, and deinonychosaurs, where the relatively derived Deinonychus can fold its wrist less than the more basal Bambiraptor. So this guide shouldn't be considered as a set of hard and fast rules, but rather a starting point for artists who want to make their restorations as plausible as possible.

Finally, a few days ago I posted a teaser for this post challenging people to determine what aspect of the above Deinonychus illustration was incorrect. By now it should be clear that the wrist is folded too far back. Appropriately enough, the first one to nail it was the artist, Nobu Tamura, himself! Commenter A.G. came close, speculating that it was due to the orientation of the glenoid, but that has more to do with the range of motion of the upper arm and how far it could extend into a bird-like flapping position, rather than the way the wing folds up. Good job guys!

--Matt Martyniuk

References

* Senter, P. (2006). "Comparison of Forelimb Function Between Deinonychus And Bambiraptor (Theropoda: Dromaeosauridae)". Journal of Vertebrate Paleontology, 26(4): 897–906.
* Sullivan, C., Hone, D.W.E., Xu, X. and Zhang, F. (2010). "The asymmetry of the carpal joint and the evolution of wing folding in maniraptoran theropod dinosaurs." Proceedings of the Royal Society B, 277(1690): 2027–2033.

Reconstruction Tips: Flukes Part 3

We present for you yet another edition of...

Time for another installment of Craig's ongoing palaeo-art (mis?)adventure...

Flukes go on Whales... NOT in your Art!

Part:3

Previously on Flukes (imagine catchy suspense music, just like an awesome cliffhanger multi part TV show)
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Part 1- I decided to try and create some palaeo-art for New Zealand Palaeontologist Ewan Fordyce. This was unrequested art, and this is probably a good thing considering what I first produced! Find out the HUGE mistake I made and the first lesson you should learn from my folly.
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Part 2- After regrouping from my first embarrassing version of the Shark Toothed Dolphin, I proceeded to try and rework it. However with this second attempt my strengths and preferences from usually creating Dinosaurs created an odd reptilian-whale hybrid. This has yet another key lesson to learn here.
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Now the continuation...
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So after two months of playing with my Squalodon, I ended up with this the "Dolphinsauriod"...
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At the time, I just viewed this particular incarnation of the model as just another mistake.

Looking at it now, the Dolphinsauriod marked the end of an era in my art. This was my last truly amateur approaches to reconstructions. As of April 2009 onward I would use one sort of reference or another when recreating anything, and thus have some degree of credibility in it.

However when starting the project in early 2009 I did not have many references for Squalodons. Even now having done extensive research on the family I've only managed to come up with a dozen or so. Of those only a few are worth looking at.
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Bringing me to the first lesson of today's post...
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Rule #3 of Scientific Restorations: There is no such thing as "enough" references. Track down as many pictures, drawings, photos, and restorations of a prehistoric subject's skeleton, body, and fossils. There is always another aspect or idea to be found in a new reference (even if it is just not to do it like a different recreation), so get as many as you possibly can!
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This can be hard with less popular and obscure critters, like say Shark-Toothed Dolphins. So I'll take you through the useful references I managed to track down, and why I thought they were worth looking at.

There were several overly simplistic restorations, and of these I found this cover page by Alton Dooley for his description of Squalodon whitmorei to be any good.

Though the prey dolphins in this particular piece are a little too minimalist to reference, the Squalodon chomping down on them is surprisingly accurate. The overall proportions of the skull, fins, and body are all perfect. Making this useful for scaling my model.

If for nothing else, this picture also gave me some confidence. If this was among the top 50% of Squalodons out there, then I had a good shot at creating a new addition to this elite group of artwork.

Perhaps the most influential of all Squalodon recreations was this one by Geoffrey Cox. This comes from his amazing little popular science book Prehistoric Animals of New Zealand. (Though sadly out of print, this book is by far one of the best ever released on New Zealand fossils, and definitely has the best palaeo-art to accompany it. So if you are interested in the subject try to track down a copy).

I consider this the "type specimen" artwork of Squalodon from which most other palaeo-art restorations are based. Often in palaeo-art I find that someone will do one key version of an animal, and then 90% of later artists approaching the same subject tend to copy or borrow heavily from this first "type specimen". I'm planning on doing a post on this phenomenon later, but that is the general idea.

One of the most clear examples of this derivative referencing (which is not necessarily a bad thing, I point out, but it is just important to acknowledge) is Arthur Weasley's Squalodon from wikipedia. It is a nice piece, but where it is accurate it incorporates all of Cox's features.

Weasley's body and fin proportions are not very well measured, and so I didn't really use this picutre at all. It is worth crediting this piece with a pretty accurate skull though. At the same time I didn't use it as it rehashs all of Cox's ideas. It has the same skinny long slender snout, and the relatively spherical melon organ (what makes a whales forehead) as Cox's.

My favourite of the "Cox"ian Squalodons is Rob van Assan's version here. Again we see the same general head configuration with the long beak and very small round melon organ.

Not that I'm saying one has to reinvent the wheel with palaeo-art, especially if a pioneer artist captures something scientifically critical to an animal in their earlier version. However Squalodons' heads did not necessarily look like this. Dr. Fordyce has directed me to create a completely novel vision of Squalodon compared to the Cox idea (wait for this in Part 4).

Highlighting the fact that the look of Squalodons is not completely agreed upon, you'll notice Mr. Assan has put his own spin on the Dolphin. Instead of a dorsal fin he has added a river dolphin (the closest living relatives of Squalodons) ridge along the back. This gave some food for thought, and prompted Dr. Fordyce's opinion on the fin (again coming in Part 4).

A radical departure from the Cox model, is this rather Bottlenose Dolphin looking Squalodon by the Aquaheart Museum (as the majority of this site is in Japanese which I don't read, I couldn't find an artist's name. If you know the artist who created this piece of art please let us know in the comment section or email us at artevolved@blogspot.com.)

Though pretty much everything about this piece runs against what we know of the Shark Toothed Dolphins (in particular the lack of said shark-like teeth) as it is trying to mimic a modern Dolphin, the extant looking melon organ turns out to make this one of the key Squalodons I came across.

The best two sets of references I found combined aspects of both styles. The one set of pieces by Chris Gaskin I was asked not to post, as they are the property of Otago University. Chris Gaskin created the pieces for Dr. Fordyce in the 1990's, and so I found them a good guide to what the good doctor would want in his renditions (though as I'd find out, Dr. Fordyce's views on Squalodons have changed in the last 15 years).

The other pictures, such as the Waipatia above (a relative of Squalodons), came from a book accompanying a fossil whale exhibit from Japan. Sadly I only had access to Dr. Fordyce's copy, and the majority of the writing was in Japanese, so I was unable to get the artists name. If you know the artist who created this piece of art please let us know in the comment section or email us at artevolved@blogspot.com.

In both sets of pieces the long unusual snout of Squalodon and its enormous teeth are mixed with a much more modern Dolphin face (unlike the basketball Cox look).

Of course had I not been working with Dr. Fordyce my decisions as what to take from these different interpretations would have been difficult. It illustrates the common problem with palaeo-restorations already covered here at ART Evolved. When looking at references with no proper scientific input, it can be tricky.

The most trust worth reference you are ever going to get is the fossil material itself. In my case this was just the skull. Only a few complete Squalodon skeletons have ever been collected, and none were from NZ or easy to access from here.

With each new approach I've taken on the whale since the first (in Part 1 of Flukes) I have ended up referring to the skull more and more. By my last rendition of the Squalodon (coming up in Part 4) the skull was my centre referral point. Which would be my other key piece of advice...

Rule #4 of Scientific Restorations: No matter how other references you find and how much you like other artists takes on a subject, always make sure the original fossils are your main guide. This way you can separate the "facts" in your other references from the "artistic licence and/or style" flavouring the artists may have injected into their piece.

So coming back to my art. This was the Dolphinsauriod. Despite its reptilian flavour, many of the key Squalodon features were starting to take form. I had the long snout, I had the large teeth (though at this stage they were a little too exaggerated), I had something of a melon organ (though not correct in Dr. Fordyce's opinion).

A rough comparison between the Dolphinsauriod and the skull showed that my snout was not quite long enough, and a new factor not mentioned on the other restorations before (as they all got it correct) was the eye was far too high on the face.

The other key issue, causing my whale to look more like a marine reptile, was how I was lacking a proper Dolphin cheek.

After referencing the Japanese artwork and Gaskin, plus some modern Dolphins, this is the fix I came up with.

Though it is quite rough in these early pics, already my Squalodon was looking a lot more mammalian. It was these finer tune details that I would learn much more about in the coming months and attempts.

For the time being (at the time) putting the teeth back into the skull made difference between mammal version 1 and Dolphinsauriod quite remarkable, despite the lack of polish on version 1.

Using my very crude model to fossil comparison, the new model was looking good. This technique however was very crude, and i was going to find out that I needed a lot more fine tune work. You can check out a preview of my new method of art to fossil comparisons here.

Finally I was onto the base of the good copy...

Of course that still wasn't quite the same as having the good copy...

More on that in Part 4!

Reconstruction Tips: Extant Referencing

Welcome to yet another edition of...

Today we bring you the first ever self contained Reconstruction Tips.

I [Craig if your wondering] share some tricks that helped with my biggest palaeo-art achievement yet.

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I owe it all to this piece by Julius Csotonyi entitled "Tylosaur and KT Event".

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I have been obsessed with Mosasaurs for the past decade or so. I just find the idea of marine Monitor Lizards (and/or possibly limbed Snakes...) fascinating. I mean come on, a Komodo Dragon with flippers that swam around taking on sharks, how is that not the coolest thing ever?

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The thing is I had never found a restoration of a Mosasaur I was ever been 100% happy with. Don't get me wrong, there are some great Mosasaur recreators out there. Dan Varner in particular deserves special mention, as do the CG ones from both Nigel Marvin's BBC Sea Monsters and National Geographic's Sea Monsters (apparently you have to name any moving picture project with a Mosasaurs in it Sea Monsters... not that I disapprove ;P ). Yet few recreations of these marine reptiles have ever completely satisfied me.

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Then I found this Csotonyi piece, and the reason for this dissatisfaction slammed me in the visual cortex. No one (until Csotonyi) had ever tried to completely tie a Mosasaur to its Monitor Lizard roots. Despite the bold new direction he'd taken, I felt that Mr. Csotonyi's concept could be taken a little further...

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Of course a concept is easy to picture in ones head. Getting it out of the mind and into the material world for others to see, that is the trick.

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How was I to take my friend here, the Australian Perentie Monitor (Varanus giganteus), and essentially turn him into a Mosasaur? (I choose the Perentie as I have several great reference pictures of a stuffed one in the Sydney's museum, and I love its colouration. If I had better pics of the Nile Monitor (Varanus nilotictus) it would have been in close contending).

This is the answer I came up with to this challenge.

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Now as I'm sure many of you know, I am typically dislike to outright hate my own work. With my Tylosaur here I'm not just pleased with this critter, I'm down right proud of it. I somehow managed to arrive at nearly the exact point I aimed for!

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It was not outright luck that brought me to this conclusion either. Rather using a combination of artistic skills (I've been building through the motivation provided by ART Evolved), and more importantly the judicious application of referencing and scientific research.

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Though this Tylosaur model is miles ahead of my Squalodontid whale, it owes its existence to the lessons I have been learning through my whale mistakes (read about those in my Flukes series of articles). I'm jumping the gun a bit, and this article is essentially a preview Flukes part 3 (coming soon), but with better illustrations.

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As a quick aside for you more technical minded people, I accidental refer to my Tylosaurid here as a "Mosasaur" a lot. This is a force of habit from tour guiding, where I simplify rather then specify things. I use the term Mosasaur in the overall family sense, and by this logic I am correct as Tylosaurs were just a specific branch of this family. In cases where specifics I mention are only true about Tylosaurs and not other Mosasaur subfamilies compared to Monitor Lizards, please keep this habit of mine before losing it at me. Thanks :p

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Before I could start on Monitor Lizarding a Mosasaur, I had to understand how both animals were put together. What were their similarities and their differences?

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Skeletal references are the only way to understand these, and as of such I tracked down as many of these for both groups as possible. Fortunately Monitor Lizards and Mosasaurs have a healthy representation on the net. Not all non-Dinosaur prehistoric creatures enjoy this (like say Squalodontid whales!), and it can really slow you down with obscure critters.

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When acquiring these references from the internet it can be quite hard to find pictures of the right or comparable angles for direct creatures and fossils.

Hint! Whenever you are visiting a zoo or museum take as many of your own reference photos as you can! Of anything and everything that you find interesting, as people on the web may not have the same tastes as you!
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I focused most of my effort on the skulls, as I've been learning 75% of a solid restoration relies on its head, and Mosasaur and Monitor Lizards differ post cranially in some drastic ways (especially in the neck region).

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As I was aiming for my Mosasaur to look as much like a Monitor Lizard as possible, I also required a fleshed out Monitor Lizard to visual focus my effort on.

So here is a rough flow chart of my initial findings of Tylosaurs vs. Monitor Lizards.

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Hint! Before comparing references make sure you pick one common parameter to scale them on. In this case I picked the length of the skull, but I could have instead chosen the height. It is important to pick a single parameter, especially when using more than two references. Otherwise you may get some of the details wrong.

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Modern Monitors' heads are much taller proportionally then the Mosasaur. You can see this in the middle of the chart where I have overlay en the Mosasaur skull over both the Monitor's skull and head. To accurately use the Monitor as base of a believable Mosasaur I was going to have to alter it to match the Mosasaurs dimensions.

Photoshop-like programs are an incredibly helpful tool in comparative anatomy research. I'm talking about before you ever tackle the art end of a project mind you, no matter your medium. There is just so much you can do to your references within these programs.

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Hints!

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Here are some of the good things to keep in mind when bring your references into Photoshop:

• Always copy and paste your references into a new file. This way if you screw up or heavily alter anything you don't have to re track down your baseline reference. This might sound simply, but forgetting it even just once can be devastating (especially with your own personally collected references!)

• Put each element into its own [raster] layer. This way you can easily control and manipulate each reference without effecting the others!

• Remember when saving these files to make a Photoshop file version so that your layers remain separate. If you forget to do this, and save them as a jpeg of gif your elements will merge, and you will have to separate them again (if they don't overlap!)

So the Monitor lizards were too tall (with my chosen parameter of skull length). Easy enough. I went in with photoshop and reduced the height of my Monitor so that it roughly matched my Mosasaur. You can be as picky or accurate as you like matching these up, but I just needed approximate.

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All I was trying to see was how and where the skulls matched and mismatched. They had their mismatching areas I had to keep in mind, but overall they aligned spectacularly.

Hint! To really see how things align, remember your layer transparency settings! These are incredibly handy for looking through one reference onto others directly behind it. If you keep your references on separate layers, transparencies do not have to be permanent either. You can just lower or restore the transparency as needed.

A similar adjustment to the fleshed out monitor skull, and I had a solid visual of what I was aiming to create.

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Here is the flow chart of the various comparisons I did with the Mosasaur skulls. I omit here the same tests and checks I did with the photoshopped Monitor Lizard skull.

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With my altered fleshed out Monitor Lizard head reference I got to work sculpting and modelling this counterpart 3D Mosasaur. To follow this artistic process click here to follow my WIP posts of this work.

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Along the way I of course did several double checks to ensure my Mosasaur, though modelled after a Monitor Lizard's head was still matching my Tylosaur skull. (The overhang on the chin is my saving a bad version of this comparison. The Mosasaur skull overlay is slightly too big, in both length and height in this particular image. I forgot to save one of the good takes, but you get the idea I'm hoping).

All things considered, I think I did a pretty good job. Not perfect mind you, but that is partially lighting (this Mosasaur is currently bathed in modelling light, unlike the artistically lite stuffed Monitor Head in the museum), and I still have some fine tune modelling of wrinkles and folds to do.

So look for this fellow in the upcoming Palaeo-Environment!

Hope this look at using extant references was a help, and gives you some ideas for your own restorations!