Neutral Poses & Elmerfuddasaurus

Here's a quick look at another kind of pose: the neutral pose, which is more or less the equivalent of the standard anatomical poses used for extant animals.  I'm actually quite fond of the unassuming aesthetic of this type of pose, but alas I suspect it isn't a good candidate for a pose to standardize on.  To see why let's take a quick look at the strengths and weaknesses of the approach:

Strengths:

Better shows off the center of gravity (full-tilt running poses always look unstable...because of course they are).  A reduced burden for the author/illustrator to get a biomechanically plausible gait (although there would still be the need to get a realistic stance).  A pose like this is possibly better for some artists (e.g. 3D artists).  Certainly there's no distraction created by the pose.

Weaknesses:

 Some people might find this pose dull, although scientifically speaking that's not much of a criticism.  I suppose when used for education or popular media that could be a drawback, although arguably there's good reason for people to see dinosaurs portrayed as animals, rather than stylized carnage-machines, so the argument could be made both ways.

The biggest drawback to a pose like this is it shows off less of the anatomy, since the limbs from the far side are obscured.  It's easy-enough to fix that, by arbitrarily moving the limbs like this:

You can even show off some other pose (in this case the finders are lightly flexed), perhaps the other wrist could also demonstrate the degree of pronation that is possible (in the case of Archaeoceratops it more or less already is), which would then pack in a bit more information.  Of course if you move the other hind leg then you are pretty much back to putting the animal in a walk.

Of course you don't have to put the feet on the ground - if we're looking for poses that are more neutral about locomotion we could instead illustrate as if the animal were lying on a virtual dissection table:

Unfortunately, even if this were explicitly labeled, I suspect someone somewhere would take it as intending to show off biomechanical behavior.  Jumping.  Or dancing.  Or maybe sneaking along, saying "Be vewy vewy quiet, I'm hunting wabbits.":

So it seems to me that you probably can't have it both ways - to get the benefits of the neutral pose we'd have to sacrifice showing off as much morphological data.

Conclusions:

Neutral poses have a couple of advantages - they may benefit some types of artists, they reduce the amount of biomechanical inference that is required, and their lack of "visual excess" means they won't distract from the anatomy.  Unfortunately they also obscure more of the anatomy, and trying to correct this by moving the limbs around quickly sacrifices the very things that were an advantage to the neutral pose.

For this reason I think neutral poses may have limited appeal - and if that's the case, it probably isn't an ideal candidate for a new standard.

Skeletal Poses: Do they matter?

Ok, first stop chortling.  Then take a good look at the handstand allosaur up there.  In several respects it's scientifically accurate - the bone outlines reflect the actual morphology of the fossils, and the proportions are correct, so it's a "realistic" skeletal reconstruction.  The pose is certainly unusual, but none of the joints are disarticulated.  In these respects it's better than many of the skeletals that appear in peer-reviewed journals.  Yet I think it's safe to say that most researchers would consider that allosaur to be in a biologically implausible position.

Do skeletal poses matter?

 Is this pose just as good as any other, or are in fact some choices more useful?  After the break I'll try to make the case that choosing a pose is an important part of making a skeletal reconstruction, rather than a random after-thought.

I shouldn't have to say this, but just to be clear: I don't think Allosaurus could do a handstand.  Even attempting it would probably lead to a dramatic reduction in life expectancy. Yet if all a skeletal reconstruction is supposed to do is to show off the bones, then the only real complaint in the image above is that the left leg obscures the pelvis more than necessary.

So why not use this pose?  Certainly it would be easy to build up a "brand" around such a pose.  Yet I'd submit to you that skeletal reconstructions with inaccurate biomechanics undercut the value of a skeletal by virtue of the added theoretical "baggage". Mike Habib, clever gentleman that he is, anticipated this point in his comment on the previous article, which I'll quote below:

"...it is distracting from the point of the reconstruction if the viewer spends time trying to work out if the pose is realistic. Ideally, a "standard" pose should be a 'no-brainer' for most taxa, so that viewers can focus on, you know, the *skeleton*."

In addition to distraction, poses that are not feasible (or even just unlikely) create other problems; some authors will avoid such skeletals (perhaps even choosing a reconstruction that is otherwise less accurate).  There will inevitably be well-intentioned artists that introduce incorrect poses into their work.  And of course other scientific illustrators may be scared off of using the same pose, making comparisons between bodies of work more difficult.

If we only dealt with ludicrous poses, this may seem like a straw man argument.  So let's consider a less overt example:

That's Silesaurus, from the original description in JVP.  The shapes of the bones generally reflect the individual elements described in the manuscript, and the proportions are quite good; clearly it's intended as a realistic skeletal reconstruction. The pose is certainly not wrong in some over-the-top manner, yet there are several problems with it.  Some differences are due to different interpretations of rib orientation and pectoral girdle positioning (but that's another post...), while others are not so easily categorized.

The vertebral column in general is problematic; the flex in the base of the neck and the overly-straight back are positions that may be possible, but would not be terribly common for the animal.  The forearms are pronated to a degree that is unlikely in such a  primitive dinosauromorph.  Even more clear-cut is the position of the right forelimb.  The right humerus (the upper arm bone) is so far forward it would be completely dislocated from the shoulder socket.  Moreover, given the position of the visible part of the humerus the proximal part would be articulating with the center of the coracoid, rather than the glenoid fossa (the shoulder joint).

If the only thing you care about is the bones, then I admit that how distracting these issues are depends on how closely you pay attention to biomechanics.  But the pose isn't without repercussions; a quick image search shows that several derivative skeletal drawings have been produced that perpetuate the same errors, and a decent number of life reconstructions also exhibit those errors.

(Image from here; artist unattributed.)

To some degree this is where we get to the crux of disagreements - people are often quick to criticize as outlandish the problems that appear at the macroscopic level (Allosaurus can't do a handstand!) while ignoring the problems that are less obvious, or at least the ones that fall out of their area of expertise.  As a result I'd be willing to bet cold hard cash that the handstand allosaur at the top would not make it past the same reviewers that gave a pass to the Silesaurus paper, even though the skeletal in that paper is a less biologically plausible pose than the allosaur.

If people really want to present just the bones, and not make any statement about functional anatomy at all, perhaps researchers should consider exploded diagrams:

Exploded diagrams have a proud tradition in technical illustration, and can be done without making any statement what so ever on functional morphology.  I should note that the above diagram is a butchered version of my Styracosaurus skeletal; in a diagram prepared from the start to be an exploded diagram I would expect the limb bones and possibly even the vertebrae to not be connected as in life.  Providing all of the bones scaled (and revealing only the preserved portions) would accomplish the purely descriptive goals of a traditional skeletal (perhaps even be superior, since nothing is hidden by the limbs) and completely relieves authors/illustrators from making explicit claims about how the animal went together.

So in conclusion, the point I want to make is this:

People do not have to put realistic skeletal poses in their papers.  They can use schematic diagrams (which partially relieves the burden) or use exploded diagrams (which completely removes it).  The exploded diagram in particular conveys more morphological evidence then a traditional skeletal drawing, while being 100% agnostic about biomechanics.

If authors/illustrators do choose to do a realistic skeletal reconstruction, then they should accept the need to place them in biomechanically sound poses.  Inaccurate poses can distract from the other purposes of a skeletal diagram, and may mislead paleoartists.  Down the line if such diagrams get incorporated into educational diagrams they also play a role in confusing students and consumers of popular scientific media...but that, two, is another post.

In the mean time, remember: Poses are important!

The Great Skeletal Repose of 2011

As many of you are no doubt aware, earlier this year paleontologist and scientific illustrator Greg Paul made a fairly public hubbub when (among other demands) he requested that all other illustrators stop using the skeletal poses he popularized the last several decades.  There was quite a bit of consternation over the issues he raised, filled with both sympathy (it's hard to make a living from paleoart) and skepticism (most people don't believe Greg has any legal basis to try and lay claim to an anatomical pose - I suspect those people are correct).

None the less, on March 8th of this year I wrote:

Allowing Greg (Paul) to establish a branding around the poses he popularized is a request I'm inclined to grant; after corresponding briefly with Greg I've decided to embark on the process of reposing my 100+ skeletal reconstructions.

That lead to a lot of questions.  I will be examining in greater detail skeletal poses and how we can make them as useful as possible, but first I wanted to address some of the common questions that came up from this.  Namely...

What was I thinking???

This is the main question I get.  While it's been phrased several different ways, the crux of it is some people are concerned whether the (substantial) time investment in changing the pose in all of my skeletals is worth it.  Of which the most substantive question is:

Will they will be less useful in another pose?

Several workers wrote to me with this concern - that by altering the pose it would make my skeletals less useful, since they would be more difficult to compare directly with Greg's.  I am a strong supporter of standards in science, so I'm sympathetic to this claim.  That said, due to the aforementioned hubbub the utility of those poses as a standard is rapidly eroding as several artists are now altering their poses, or actively advocating for everyone to use their own unique pose.  Since artists are frequently somewhat conflict-averse, I expect this exodus to continue, regardless of legal standing.

Given this larger perspective, I feel that we'd be better served to find a new pose to standardize on, perhaps one that can still be compared effectively with Greg's body of work.  An open standard by design, so that other researchers/illustrators can feel free to adopt it without fear upsetting someone else who uses it.  And by starting again we have an opportunity to "reboot" the standard skeletal pose, perhaps producing something even more useful then the original.

One obvious example: the "Greg Paul" pose for theropods, though iconic, is held back by its theoretical baggage.  The pushing off the left foot while dashing around at a full sprint pose is not something that all researchers agree is possible in all theropods.  Several times while providing a skeletal for another researchers publication I've been asked to alter the pose for this reason.  I've done this a couple of times due to my own incredulity; for example I illustrated Majungasaurus in a walking pose, since I'm skeptical that it could sprint:

So by undertaking this project we can take advantage of hindsight to create a standard that is both open and potentially solves some of the largest criticisms of Greg Paul's poses.

So what, you're just going to pick the new "standard"?

I do need to pick a new pose.  Or rather several (for various groups of dinosaurs).  But it won't be much of a standard if I am the only one using it.  Instead, I'm hoping to crowd-source this discussion, involving any individuals who have a stake and wish to participate.  To that effect I'm working on a series of articles on such subjects as: Do skeletal poses even matter?  And if they do, what is the best way to go about creating a pose?  Who are we serving with these poses?  And how can we balance the sometimes conflicting needs of the "consumers" of skeletal reconstructions?

I'm actively communicating with some people, and hope to engage others to pick up the torch.  I hope to get a wide range of responses on the blog, and perhaps to inspire others to create articles on the subject.  The best results can only be achieved if we get generate a robust conversation on the subject.  I hope you'll participate!

By the way, if for some reason you'd rather share an opinion privately, feel free to email me and I can incorporate your concerns into a future discussions anonymously.

Schematic vs realistic skeletals: Follow up

I'm happy to say I've received some excellent feedback on the previous blog post on schematic skeletal diagrams.  Several comments in particular share a similar feeling, which I'll repost here:

I don't see any reason someone would make a reconstruction more schematic than necessary (due to perspective, converting bones to lines, incompleteness or deformation, lack of available material, etc. that you mention). In the strat column and cell examples, there are obvious reasons not to make them realistic, but what about skeletons? Surely the only reason to not draw bones correctly is to save time, but in that case I'd argue it's better to not to include a reconstruction than to make a half-assed one. -Mickey Mortimer

This is a very.. charitable interpretation of what's going on. I agree that there is a place for schematics, but I think they should be made to look schematic (you see this sometimes, where bones are reduced to oblongs, and laid out in a vary schematic way). Just labelling skeletals as schematic will do little to stop artists using them I'm afraid.  -John Conway

I would have to side with John on the matter of schematic representations. You write "When writing a professional paper, which one of these styles is "better" depends on the needs of the authors, the time, ability, and access to the data that the illustrator has, and a host of other practical concerns. Far be it from any of us to dictate that one type of skeletal diagram is suitable in all cases." But I can't see any way in which is schematic diagram is better than a realistic one. In short, surely the only reason to put up with the schematic is when the data just isn't there to do the job right? -Mike Taylor

As you can see, they all raise a similar question - why would anyone want to publish a a skeletal diagram that isn't realistic (or in some cases, "correct").  I suspect that they aren't the only ones with this question, so I thought it would be worth addressing the issue with its own post.  So let's start at the beginning....

Historical Perspective: 

As I showed in the earlier 3 part series on dinosaur skeletals, the reality is in the history of paleontology it simply has never been a standard requirement to invest the time and effort that goes into producing realistic skeletal reconstructions for publication.  Yes, for a period of time realistic skeletals were used by some paleontologists in Europe in the middle of the 19th century, but hardly all.  Concerns with improving the anatomical posture of mounts saw a brief return to publications in the U.S. in the 1920s and '30s, but neither of these periods saw anything close to a universal adoption of realistic skeletal reconstructions, nor did either period produce published guidelines on how to produce such skeletals - and don't forget that they make good examples by virtue of how unusual they are in the history of paleontology.  

So point 1: It may be be true in some objective sense that realistic skeletal drawings are preferable, but it's never been a standard in scientific publications.  Sure, several decades of skeletals by Greg Paul and others may have created an expectation in artists that realism should be the default, but that hasn't translated to professional publications.  In my opinion it's neither fair nor realistic to expect all researchers to start including realistic skeletals (especially given the issues discussed below) in published papers cold-turkey, but it is fair to ask them to label their diagrams more explicitly (indeed, better labeling is something we should always strive for).  Why isn't it fair?  Well, there's a host of...

Practical Concerns:


Writing a paper takes a while.  While the process isn't really the mysterious and inaccessible dark art that some assume, it does take time and effort.  And unfortunately producing realistic skeletal drawings largely has been a mysterious dark art, without explicit guidelines, and with only a couple of people that produce them (and there isn't any universal consensus on who those people are).  The result is that a paleontologist that wants to get a paper out on a new dinosaur could be looking at a really significant investment of time (and possibly money) to try and include a realistic skeletal reconstruction.

Also remember that many researchers don't have research specialties that lend themselves to supervising the creation of a realistic skeletal reconstruction; even at the best of times it can be hard for technical and artistic professionals to find a common language, but for an expert in stratigraphy or systematics it may be even more difficult to direct a staff artist or art student on how to produce a realistic skeletal drawing.  This wouldn't be so bad if scientific illustrators had a set of guidelines they could follow when producing realistic skeletal reconstructions, but hey, that brings me to the last point....

Skeletal reconstructions need to stop being a dark art!

Let's all have a moment of honesty here; how is a young scientific illustrator supposed to go about learning to produce a realistic skeletal reconstruction?  Greg Paul has written a single, traditionally hard to attain article on the subject, and has written several guides to how he interprets common debates on dinosaur functional morph.  That's about it; the result was that many young artists took the "make it look like Greg Paul's" strategy, but there are several problems with this.  First, it's not always clear to illustrators when something is a well-established anatomical consensus, or whether it's an interpretation largely unique to Greg.  Making this worse is that Greg has (somewhat notoriously) issued a mass cease and desist request for people to stop copying his look.  Since there aren't many sources to tease out which parts are science (and therefore not copyrightable) and which are stylistic (and therefor subject to his copyright), many artists are probably feeling like throwing their arms up in surrender.

It's my hope that through several projects (including a modest contribution from this blog) that the science behind this process can be better documented, become better subject to testing, and generally move from the realm of dark art to the evidence-driven process it should be.  But I also think we need to be realistic about what stage we're at.  Right now there aren't even a handful of people who regularly publish on the subject, and the publications that do exist often are often made in the gray literature and are not subject to further testing.

So what can we do?


I think first and foremost we have to be realistic about the size of the challenge in front of us.  Given the name of this site it shouldn't surprise the reader to learn that I think skeletal reconstructions can (and generally should) be done to realistic standards.  I also believe the creation of them should be a data-driven activity, with a methodology that is transparent and subject to testing by others.

But a lot of work has to be done before we get there.  In the mean time, properly labeling a published skeletal as either schematic or realistic will be useful to the process; by making it clear when a skeletal isn't intended as realistic it will increase the accuracy of paleoart (since artists won't use it), make it more obvious which taxa are still in need of a realistic skeletal, and improve the "signal to noise ratio" when people try to understand what are common anatomical assumptions.

Proper labeling is also easy to do, making it a reasonable request of anyone getting ready to submit a manuscript (or reviewing them), as it requires a minimal investment of time and improves the usefulness of the paper itself.  Yes, this may be the "low-hanging fruit" in a larger revamp of skeletal reconstructions, but that doesn't mean it isn't worth pursuing.  

Skeletal reconstructions: Schematic vs Realistic

Above you see two skeletal reconstructions of the basal sauropodomorph Panphagia.  The one on the bottom was published with the original description, while the one on top I just finished a couple days ago.  What is worth noting is how extremely different they are.

Some of the differences can be chalked up to errors in scaling (compare the length of the tails).  Other differences stem from the underlying anatomical assumptions, such as how rib cages articulate and the placement of the shoulder blade (definitely topics for future posts).

But if you look closely you'll see that the very shapes of the bones differ.  And in every case where the known bones differ in shape it is the skeletal that was published in the original description that is inaccurate. This strikes me as odd, since the bones themselves were figured correctly in the same paper.*

At least that's odd if you assume that the skeletal reconstruction on the bottom is meant to be a literal representation of the bones, when in fact it appears to be a schematic skeletal diagram.

What, you may ask, is a schematic diagram? Here's the Wikipedia definition: 

A schematic diagram represents the elements of a system using abstract, graphic symbols rather than realistic pictures. A schematic usually omits all details that are not relevant to the information the schematic is intended to convey, and may add unrealistic elements that aid comprehension.

The artists among you may have just suffered an involuntary shiver.  And you should; as detailed in my three part series on the history of skeletal reconstructions, it has been the norm rather than the exception for peer-reviewed papers to publish schematic skeletal diagrams.  That is, rather than attempt to represent the bones exactly as they were in life, the skeletal emphasizes key features of the anatomy (sometimes literally "emphasizing" them) while perhaps demonstrating other key information, such as which bones are preserved.  This is actually a common practice across the sciences.  Any of you remember reading about cell structures in your high school biology class?  Those illustrations of cells are not intended to be realistic, they're meant to convey the salient information effectively to the reader so you can learn the parts.

Even within the very papers we eagerly search through to discover those skeletal drawings there's a universal type of schematic image: the stratigraphic column.

No one mistakes these for literal representations of the outcrop.  No artist would think that they could translate this image into a lovely landscape illustration that would match what you would see if you traveled to the dig site.  This sort of pictorial short-hand is both common and necessary in science.

As a scientist you want your diagrams to convey the important information, whether it's the placement of the specimen within its local stratigraphy, or the major anatomical characters and the completeness of a specimen.  That data is generally seen as more vital to a description than whether the diagram is showing the information necessary for an artist to use.

That's not to say that paleontologists don't want their published skeletal diagrams to be realistic, it's just frequently not the top concern.  But the way people view skeletal reconstructions has a profound impact on how we view dinosaurs.

Over the last two decades Greg Paul's skeletal reconstructions redefined our expectations of skeletal drawings, and the consistency with which he produced them has (in)famously refined and narrowed the range of depictions of dinosaurs, a fact that Greg Paul himself has recently lamented. As we enter a sort of Post Paulian Period, one of the lasting expectations of laymen, artists, and even many scientists is that skeletal reconstructions should by default be seen as realistic portrayals of extinct animals; a sort of virtual x-ray of extinct life forms.

And why not?  Greg Paul may not want people to base their paleoart on his skeletals, but he's produced more skeletal reconstructions than anyone else, and he obviously intends his skeletals to be realistic depictions of extinct animals, right?  

Right?!!!

To be frank, the answer is both yes and no.  Any line illustration is necessarily somewhat schematic, since you are sacrificing details for the clarity of solid lines.  Greg Paul himself documents some of the areas where his skeletals are more schematic than literal (interested readers are directed to pages 226-228 of Predatory Dinosaurs of the World).  Among the shortcuts Greg takes are simplifying the gastralia basket (something I do as well) and rendering the limbs in side view as if they are in a perfect parasagittal plane, even though in life the elbows and knees would bow out.

Does that mean that paleo artists need to throw their arms up in the air and quit?  Not at all.  We may  not be able to establish a black and white dichotomy between schematic and realistic skeletal drawings, but there are clear differences in practice.  The short cuts Greg takes are intended to balance saving him time while having a minimal impact on how realistic the skeletal is overall.

As an example I offer up my experience when describing Supersaurus with my colleagues; not surprisingly I was working on a skeletal reconstruction of the critter as part of my contribution.  As with all of my skeletal reconstructions, I wanted the supersaur skeletal to be an accurate and realistic representation of the animal, not a purely schematic one.  Alas, Supersaurus is only known from two specimens, and both of them leave a lot to be desired in the category of completeness.  This made the process a lot more difficult than it is when restoring an animal known from more complete remains.  But all was not lost.  We spent a lot of time evaluating which species were best suited to pattern missing parts after, and did lots (and lots) of cross-scaling; not just of individual bones, but also in proportional relationships.  That is to say I was able to constrain the unknown portions of the animal from comparative and phylogenetic data.  The upshot?  Have a look at this:

What is particularly noteworthy is that the two distal vertebrae were not known when I first made this diagram.  We only had ~10% of the tail, but with careful scaling and proper selection of taxa to model the bones on, I didn't have to make any changes to the skeletal after the additional bones were excavated and prepared.  

Obviously things don't always work out this well - sometimes it's less clear which taxa should be used to constrain missing elements, or an animal might have truly novel proportions.  But missing data and margins of error are simply a fact of life in paleontology.  What I hope is clear is that regardless of the possibility for error, this skeletal is intended to be a realistic portrayal of the animal, not a purely schematic one.

While the degree to which a skeletal drawing is schematic or realistic isn't always black and white, the impact they have on paleo art is.  When an artist bases a life reconstruction on a skeletal they need to have the real proportions and shape of the animal, which are just not available in schematic skeletal diagrams.  And it's not just art - for better or worse researchers sometimes cull data such as relative limb proportions from published skeletal drawings.  If, for example, a researcher was interested in comparing relative tail lengths in basal dinosaurs, it would matter very much which skeletal of Panphagia was evaluated.

For some dinosaurs only a single skeletal reconstruction exists.  Sometimes when when there are two or more they are quite different.  So how is one to know which (if any) of the skeletals are meant to be more literal, and which are schematic?  This brings me to the main issue of the day:

We need more transparency in skeletal drawing labels!

The two drawings of Panphagia at the beginning of this post are quite different (especially if you are trying to draw the beast), yet they both convey accurate and useful information.  They just aren't intended to convey the same types of information (although there is overlap).  When writing a professional paper, which one of these styles is "better" depends on the needs of the authors, the time, ability, and access to the data that the illustrator has, and a host of other practical concerns.  Far be it from any of us to dictate that one type of skeletal diagram is suitable in all cases.

What is needed is for authors (and their scientific illustrators) to label their skeletal diagrams more precisely.  Skeletal drawings are not like the schematic diagrams of stratigraphic columns, as there are large bodies of published skeletal diagrams that are intended to be realistic portrayals.  Because there are multiple visually similar types of skeletal diagrams, we need proper labeling so that the viewer's expectations match the authors' intent.

Proper labeling is a basic part of science; papers are rightly rejected for not documenting the confidence interval in a study, or for failing to be precise in the use of significant figures.  In fact most of these practices become second nature long before getting a graduate degree.  So why not with skeletal drawings?

There actually are a few stumbling blocks.  For one, there aren't any published guidelines to differentiate between the two.  Another problem is that not all authors are actually aware of the difference - I know of cases where the artist has been largely left to produce a skeletal on his or her own with little instruction ("it's like taxon A but with a bigger nose and longer tail").  Yet other researchers simply don't think any extinct animal can be reconstructed with this degree of accuracy ("too many assumptions") so they feel all skeletal reconstructions are schematic.  This last view may not be correct, but many of the techniques that render it incorrect are not published in a peer-reviewed journal.

But that doesn't mean we can't start to work to make it better.  To facilitate this (or at least a healthy discussion) I will make the following suggestions for researchers and illustrators:

For researchers:

1) No matter how talented an illustrator, people cannot consistently render accurate proportions without measurements.  If measurements are not available (or not made available) the diagram must be assumed to be schematic.

2) People can (obviously) not draw accurate bone profiles if they have never seen the bones in question.  Ideally an illustrator would see the original material, but if this isn't practical be sure to get photos, the more the merrier.  If this is also not practical, label the skeletal diagram as schematic.

3) Sometimes there just are not enough bones to justify a new skeletal reconstruction, so skeletals of related animals are modified just enough to show of the new bone (or bones).  Please label them "Schematic skeletal of Taxon A, modified after Smith (2010)".

4) Remember there is no more shame in using a schematic skeletal diagram then there is in using a strat column.  But please label the convention you are using!

5) If a skeletal is intended to be a realistic reconstruction of the animal, then it should also be treated as a form of data that needs updating.  If new finds or a more complete description uncovers some inaccuracy, update/amend the image it in a future publication, as you would with a description or phylogenetic analysis.

For Illustrators: 

1) Ask up front what sort of skeletal drawing is being asked of you.  You should also know what you need in order to produce the requested image - if you don't have enough information to produce the type of drawing that is desired, ask for it.

2) Illustrations are often used outside of professional papers - in books, museum displays, on this fancy world wide web thingy.  Maintain proper labeling wherever possible (I realize that illustrators may have little control over some projects, but maintain best practices whenever possible - this will also encourage book editors and museum directors to adopt more explicit labels).

3) If you are producing a realistic skeletal reconstruction, take responsibility for updating it as necessary.  If there isn't time to make changes, put that in the label (e.g. "Executed before additional information about the elongated neural spines was available.")

4) There's no shame in making a schematic diagram.  It's a useful contribution to science, so don't feel like you're producing a "second class citizen" of the illustration word and decide to not label it precisely.  

5) Finally, if you are trying to do a life reconstruction of a dinosaur, be sure to find out if the skeletal drawing available to you is schematic or not.  If it is, you may need to do more work before illustrating it.  That is, unfortunately, the nature of our work.

Conclusions?

I feel like this issue has been a "dirty little secret" in both scientific and paleo art circles.  Hopefully this provides some food for thought.  A lot of work needs to be done if we're going to continue to move the "science" in scientific illustration forward, but more accurate labeling of images should be something that can be universally embraced, and something we should all be aware of.

* I want to be very clear that I'm not criticizing the illustrator of the original Panphagia skeletal reconstruction (there isn't specific credit given in the Martinez & Alcober paper, so I presume it was done by one of the authors).  It's a perfectly good schematic, and demonstrates the key features of Panphagia as well as which bones are preserved.  This also in no way should cast aspersions on the paper itself, which is an excellent example of the value of publishing longer format descriptions in journals like PloS ONE, rather than the glorified abstracts required by certain high impact journals.

I chose this example because it was recent enough and high profile enough to make an excellent jumping off point for the larger discussion of schematic skeletals, not because there is anything wrong or unusual about it.

Back to our regularly scheduled blog posts...

Apologies for my multi-week absence.  I had to finish up some large projects.  I'm embarking some new cool ones as well, and I'll tell you about them as soon as I can.  In the mean time, I'll be getting back to posting blogs on dinosaur anatomy, as well as another series I have in mind on skeletal poses.  If you have any ideas of topics you'd like to see, please leave them below.  In the meantime, enjoy this skeletal drawing of Stokesosaurus, a tyrannosauroid that lived during the Late Jurassic of North America:

Tails of Woe

Welcome back!  This will be a shorter article that continues the concern for tails that we established in the inaugural T. rex tail post a couple weeks ago.  There is an all too common error that artists make when they attempt to impart a sense of to dynamic motion to their dinosaurs - and in particular to the dromaeosaurs.  They flex the tail up at the base so sharply that it would break the tail...if not break the pelvis!

Tail Tales: Break Dancing

We all like lively dancing dinosaurs; after a century of seeing moribund dinosaurs in swamps it's understandable that modern artists want to convey the "awesomeness" of their subjects.  If you ask me it can go too far sometimes - animals don't live their lives at 90 miles an hour - but we can all grasp the excitement of making a dynamic composition.  One way to impart motion is to have the tail doing something dramatic.  Alas, enhancing your dancing dinosaur this way without considering the anatomy may lead to an image where the animal has its tail disarticulated, or worse.

I mentioned dromaeosaur images tend to be among the worse offenders, and I know some of you are thinking "I've read that dromaeosaur tails can flex upwards at a 90 degree angle at the base of the tail!!!".  And it's true, the first several tail vertebrae are modified in such a way as to provide an expanded degree of flexibility (for up and down motion...not so much side to side), which means they have the ability to tilt the tail up sharply, to intimidate a rival, or just to better fit on your piece of paper.  But it's important to note that this tilt up takes place over the course of several vertebrae, meaning it can't happen like this:

At least it can't happen more than once unless the animal has good health insurance.  Now I certainly don't want to pick on Chris Srnka here - he's a fine artist and a lot of people make this mistake - this was just a great image to demonstrate the problem.  If you look at the image in handy-dandy X-ray format (as provided by Photoshop.

That red arrow is the steepest possible angle the tail could take emerging from the pelvis.  Why?  Dinosaur pelves have many vertebrae built into the sacrum (adding vertebrae to the sacrum is actually one of the characters that define what is and what isn't a dinosaur).  That sacrum fuses together and to the pelvis in adults, but even in juveniles there are no moving parts involved.

Front is to the left, the tail would be to the right (Carpenter & Wilson, 2008)

See?  There's just nothing that could move, even hypothetically.  In the case of dromaeosaurs the tail flexes up by spreading that 80 or so degrees of motion over 6+ joints, so none is flexing more than 14 degrees.  Here is a diagram of it:

So no more dromaeosaurs with tails growing out of their sacrum, please.

This isn't just a dromaeosaur problem either.  Many artists try to arch the tail base up on dinosaurs who don't naturally do this, and in so doing end up disarticulating the tail (or breaking the sacrum).  Even

Greg Paul's early Daspletosaurus painting fell prey to this temptation.

(Daspletosaurus, copyright Greg Paul, image from here.)

The problem is a bit more subtle in this painting, but the line of the vertebral column should extend gently down from the pelvis, while in this case it is flexed up right at the sacrum/tail juncture.  This would require a 25-30 degree flexure right at the first tail vertebrae (or else some flexing of the sacrum), which isn't going to happen without making the animal wince in sharp pain and reach for some Advil poste haste - and tyrannosaurs have horribly adapted arms for taking pain killers.

There are some important exceptions here.  Many sauropods, stegosaurs, and hadrosaurs have a bit of an upwards arch naturally at the tail base as it exits the pelvis.  Obviously those should have a bit of an arch (how much depends on the species in question).  But for most other dinosaurs, an arch of that magnitude isn't possible that immediately after the pelvis.

Sauropods like Mamenchisaurus have a natural flex in the tail base...but it still happens after the pelvis!

So remember, dinosaur tails may be flexible (depending on the group), but they aren't silly putty.  The vertebrae still need to articulate, and any motion you put into the tail needs to start after the hips, as the sacrum just can't bend.

Till next time, don't create your own tails of woe!

References:

Barsbold, R. (1983). Carnivorous dinosaurs from the Cretaceous of Mongolia, Transactions of the Joint Soviet-Mongolian Paleontological Expedition v19, pp 5–119.

Carpenter, K. & Wilson, Y. (2008) A New Species of Camptosaurus (Ornithopoda: Dinosauria) from the Morrison Formation (Upper Jurassic) of Dinosaur National Monument, Utah, and a Biomechanical Analysis of Its Forelimb, Annals of Carnegie Museum, v76 n4, pp 227-263.