Skeletal Drawing

The evolution of (my) Acrocanthosaurus

2012-01-28T19:10:00.000-08:00

With Spinosaurus temporarily out of the way, we're going to take a closer look at Acrocanthosaurus. This series is going to include a post on what we know and don't know about Acrocanthosaurus, how to restore the skeletal in multiple views, and how to restore the muscles. At the end of that series I'll also comment on some areas of soft-tissue variation that artists should keep in mind when they envision "their" Acrocanthosaurus.

First though, I wanted to take a moment to look at how my own reconstruction of Acrocanthosaurus has changed over the last decade. With any luck some of my earlier errors in methodology might help others who want to do skeletals. Also I hope to provide some insight to how I update skeletals over time, and the importance of revising your work as new data is published.

Join me after the break for an in depth look at the evolution of (my skeletal reconstruction) of Acrocanthosaurus...

Although Acrocanthosaurus is hardly the best known theropod, it provides more than its share of challenges when attempting to reconstruct it. In my case, I attempted the original skeletals during what I'd call a methodological nexus - it was one of the first skeletals I attempted within an entirely digital environment, and to some degree the initial reconstruction suffered as a result. I had developed many techniques when I executed skeletals in pen and ink, and most of those translated fairly well during the years (roughly 2000-2004) when I used a hybrid method of digital and ink work. Alas, attempting to work entirely inside a computer forced me to rediscover how to accomplish the same things inside of Photoshop, and as a result the first couple of attempts were actually a step backward in some ways. Luckily I stuck with it, and the results are now far better then anything I accomplished in the "analog" world.

In the beginning...

Acrocanthosaurus itself is not a new dinosaur. It was described in 1950, and it was noted at the time that the specimen was a carnosaur with enlarged neural spines on the back. What really brought Acrocanthosaurus to my attention, however, was the reconstruction of NCSM 14345, the "Fran" specimen, which was prepared, molded, and mounted by Black Hills in the 1990s. One of those specimens became part of a travelling display that I contributed to, and I was inspired by the fully restored mount, as well as my ability to take lots of photographs of the mount.

Alas, that was in the "olden days" when cameras captured light on sheets impregnated with silver nitrate rather than CCDs, and I never did scan in those photos. I still had them in 2003, but they appear to be one of many casualties of moving around frequently.

I was also attending the University of Wyoming, and their Geology library had supplied valuable gifts: descriptions of Acrocanthosaurus specimens by Jerry Harris (1998), and Currie & Carpenter (2000). Armed with proto-pdfs (read: xeroxed copies), lots of photos, and an abundance of enthusiasm I sat down to create my first all-digital skeletal reconstruction.

The tomb of the unknown skeletal...

Directly above, what you don't see is my first Acrocanthosaurus skeletal. I'm not being shy, I just didn't back up the original very carefully, and eventually the hard drive it was on suffered a systemic failure. Cloud storage was a pie-in-the-sky dream at the time, so I've lost several "original" skeletal files during the course of computer failures over the years. Luckily I've been anal retentive enough to keep current versions of skeletal files on multiple hard drives, so I haven't totally lost a reconstruction (at least, not a digital one).

What I can say is that in many ways my first attempt was an unmitigated failure. For starters, I didn't actually have the papers I mentioned above in their entirety. I'd read them in Laramie, but at the end of the semester I only photocopied the parts I thought I'd need (hey, it took time and money to copy texts in those days!). And of course the photocopies didn't always do justice to the original figures.

Instead I had to rely strongly on the photographs I had taken of the Fran mount. Even that was fraught with uncertainty, as I hadn't been able to take orthographic photos of the mount. Also, there were errors in the fully restored mount, but without all of the text from Currie & Carpenter I didn't always recall what was restored and what was cast from original bone. The results were predictably poor.

You don't have to take my word for it though. I posted that first attempt to the Dinosaur Mailing List in early July of 2003. Jaimie Headden and Waylon Rowley made quick and (deservedly) pointed replies. I had missed several characteristic parts of the tail and neck vertebrae, and a bunch of other minor details had simply been missed.

What happened? For one thing I really didn't have enough data on hand. But more importantly, I was distracted by having to solve the technical problems of a new medium. Digital skeletal reconstructions have many advantages, but at the time they were lost on me as I struggled to figure out how to simply do the things I'd taken for granted in the "analog world".

The Acro strikes back

With a bit of work, I quickly produced the skeletal above, which addressed some of the basics. It wasn't a horrible attempt - it accurately captures almost all of the proportions, and many of the changes since have been either due to newer research getting published, or on changing interpretations in soft tissue reconstruction.

One thing mistake in this earlier version is that the neural spines were too tall - I had based their height on the mount of the Fran specimen, but it turned out that neural spines were not complete in that specimen (at least not the ones in the back, sacrum, or the front part of the tail). A review of other specimens ruled out such a grandiose neural spine height, and that also has implications for paleoartists wondering how to illustrate the back.

Two important papers were published on Acrocanthosaurus after that early skeletal. One was on the forearm, which showed that the arm couldn't actually reach as far forward as I'd illustrated it (and also clarified details of the size and shape of all the elements). Another paper was published in the last year that updated our understanding of the skull of Acrocanthosaurus. When I was asked if I could supply the skeletal to an upcoming book, it was clear that I had to revamp the skeletal before sending it along...

Back to the future

Which brings us back to my current skeletal. In addition to the new skull and arm data, the newfangled Acrocanthosaur naturally sports my new skeletal pose. So how crazy different is it? In some ways it's pretty similar - the overall dimensions really didn't change, and that's a good thing. A bunch of more subtle soft-tissue changes took place (at least some of which will get to star in their own post in the future), but a couple of obvious ones involve the tail and the neck.

The tail in the newer one has a heavier base, reflecting the research by Persons and Currie on tyrannosaur tails that I wrote about last year. The tail also is a bit less bouncy. The current skeletal is moving at a more sedate pace, and its tail is no longer bouncing along like a dropped garden hose. The neural spines on the tail have also been updated, with the spines on the front of the tail (near the hips) shorter to reflect other specimens, and the ones in the middle a bit taller, again based on other specimens.

Looking at the neck, the silhouette is no longer shrink-wrapped as tightly to the skeleton. I will probably address the "why" part of that in a later post, but suffice it to say that the newer Acro would have an easier time wolfing down large pieces of meat it tore off a carcass.

A final set of changes were made in the pectoral girdle (the shoulder region). I added a furcula which, while not found in Acrocanthosaurus, now appear to be a primitive feature found in all theropods. Additionally, I used to illustrate a large cartilaginous presternum that split the coracoids apart (you can see it poking out the bottom and front of the chest area on the older skeletal).

Reflecting the articulated chest regions of other non-maniraptoran theropods, I changed it to a smaller presternum, that would have ended sooner and allowed the coracoids to almost contact one another along the midline. This slightly changes the outline in side view, but in front or top view has the effect of narrowing the front of the torso across the shoulders. Now if only someone would produce multiple-angle skeletals of Acrocanthosaurus to show this off...

...tune in next week, for the exciting "surprise" reveal!

Dawn Thief

2012-01-24T09:53:00.000-08:00

A quick post (and a new skeletal) today, while I apply a bit more polish to the Acrocanthosaurus series. To satisfy all of your skeletal-drawing-based-amusement needs I give you Eoraptor lunensis, one of the most primitive dinosaurs yet discovered.

How primitive? So primitive that we can't actually answer that question with any certainty right now. Eoraptor is one of those taxa that bounces around a lot in different studies. When it was originally describe, it was thought to be one of the most primitive theropods known. Other studies suggested it might be more primitive than the split between theropods and sauropods. Recently, some have even found it to be on the line leading to sauropods!

All three positions have shown up in recent studies, so for now at least the answer is "we're not sure". Why all the trouble figuring out who is Eoraptor's closest relative? Basically what it boils down to is that Eoraptor is so primitive that this is what the common ancestor of theropods and sauropodomorphs would look like. No matter where Eoraptor ends up on the dinosaur family tree, the difference between it and animals at the other position will be very small indeed.

If you compare Eoraptor to Panphagia (which I examined in this post), which is a well-supported basal sauropodomorph, you can see just how similar the two are. The problem is sort of like being handed photographs of all of the Kennedy's when they were two years old and being asked which one was closest in age to JFK - there's a correct answer, but it's awfully hard to tell from the information you have.

As for the skeletal reconstruction, Eoraptor didn't present nearly as many challenges as some other taxa do. For one, it's know from fairly complete remains. It would have been nice to have a more detail description of the animal in print (the original papers leave something to be desired along those lines), but luckily the specimen is available in detailed orthographic photos, which do a nice job of supplementing the published data.

That's all for now!

The Great Skeletal Repose of 2011: A Retrospective

2012-01-20T22:27:00.000-08:00

Well, it's 2012, so the Great Skeletal Repose of 2011 must officially come to an end. Most of the bipedal skeletals in my collection have been reposed much like this Velociraptor. I had plenty of things to say, and we saw some great discussion by guest writers, but when it comes right down to it, the issue feels incomplete without some sort of summary as to how I got here, and what's left to do. So let's take a quick look at where things stand now...

To some degree, the walking pose shown above was selected by acclimation. When I started to show off different types of poses, by far the most popular was the walking pose you see above. And I want this pose to be one that other scientific illustrators can feel free to adopt, so widespread can only enhance that proposition. But it wasn't just a popularity contest - there are several practical reasons why this walking pose became the winner:

The Good

1) Utility - Greg Paul of course will continue to use his pose, and a number of previously published skeletals by other authors (including all of mine up until last year) had adopted the same pose. By selecting the walking pose the retracted left leg remains unchanged, allowing for a easy comparison of the proportions. This was probably the biggest factor.

2) Functional Aesthetics - The old pose of animals sprinting along at a lively clip tended to impose a specific hypothesis of activity on the animals. While in some cases dashing along may have been quite likely, it still required that a research who wanted to use the skeletals to swallow that hypothesis, whether they agreed with it or not. With Velociraptor that wasn't unlikely, but with larger theropods it became needlessly controversial, and with graviportal taxa like therizinosaurs the results could be laughable.

3) Laziness - I prefer "efficient" over "lazy", but no matter what label you place on it, this pose required a minimal amount of alteration to my existing skeletals. And the stark reality is that when you have to repose hundreds of technical illustrations that time adds up. Quickly. Of course this reason would not have been sufficient if it weren't for the more important points 1 & 2, but it sure was a nice bonus.

Does that mean I'm thrilled with the outcome?

Yes and no. Since I'm starting with a blank slate, it would have been fun to come up with something truly distinctive. Yet the allure of the new wasn't worth sacrificing how useful the skeletals were for comparative purposes. Also, thanks to lots (and lots) of time spent pondering the issue, and to the extra stimulus provided by Mike Habib and Jon Conway's excellent guest posts, I've come to some unsettling questions that are still unresolved.

The Bad

1) Whither goest utility? - As I wrote way back in the halcyon days of...spring 2011, after I announced that I would relinquish the old pose and select a new one I got many requests that I refrain from this. Almost all of them were concerned with losing the ability to easily contrast my skeletals to others after the repose. I was (and am) sympathetic to that plight, and selected a pose that minimized the "damage".

Yet I also had a disconcerting realization: Both Greg Paul and myself had been varying the pose of the forelimbs for years and no one ever bothered to complain about the loss of utility. Sometimes we've both illustrated maniraptorans with the arms flexed into their folded-wing pose, sometimes not. Less advanced theropods obviously never adopted such a pose, so their arms often hang listlessly. My tyrannosaurs went from a similar "hanging out" pose to one that reflected the work done by Lipkin and Carpenter. Why was the issue never broached? Are forelimbs less important for comparative purposes than hind limbs? Or do we naturally gravitate towards the larger structure because of how our visual cortex's work? I don't know, but I'm unsatisfied by the discrepancy.

2) Is variety the spice of life? - Jon Conway also brought up a good point in his guest article, that there isn't a single pose that best serves every need. This is certainly true, and while I still feel that within groups making poses similar is useful, I also have to admit that in some ways the job has just begun.

3) That job has just begun - Oh yeah, and another thing. Turns out there are quadrupedal dinosaurs too. Who'd have thunk it, eh? Despite the obvious and objective superiority of theropods, prosauropods, and basal ornithiscians, there's still a lot of four-footed critters in my skeletal collection, and I'm going to have to come up with a pose for them as well. Two actually, since the graviportal species will need a pose that is different from the quadrupeds with flexed limbs. Ah well, that just means that 2012 will also need to have a Great Skeletal Repose as well.

An end and a beginning

So we've come full circle. I've adopted a pose for the bipedal dinosaurs, but still have to come up with (two!) new poses for quadrupeds. I still am very much interested in soliciting outside opinions on the subject, but I also want the blog to move back to posts about anatomy and reconstruction, rather than a continuing series of posts on the technical issues behind selecting a pose. So expect to see the occasional progress report on the quadrupeds, but don't expect it to dominate space on the blog this year.

If you have a strong opinion on the subject, don't hesitate to email me (or use that Gchat thing). In the mean time, I really do have a series of upcoming posts on Acrocanthosaurus and Spinosaurus anatomy, as well as the trials and tribulations of reconstructing skeletals in multiple views.

Stick around, won't you? 2012 should be an interesting year.

Just say no to SOPA and PIPA

2012-01-18T08:26:00.000-08:00

I've generally refrained from talking about subjects not directly related to paleontology and scientific illustration, but since our ability to have these conversations are now under attack, I've decided to make an exception today and add to the chorus of people opposing SOPA and PIPA.

Both are bills that are intended to protect intellectual property - and given what I do and how I make a living, believe me when I say that protecting intellectual property is an important subject to me. But the bills go (much) too far in crippling online commerce, removing the job of oversight away from the public eye (inviting the censorship of unpopular views, rather than illegal activity), and are unlikely to be effective in combating piracy.

In short, this bill was written by people who don't understand the internet, and are throwing lots of money and influence at Congress is part of a desperate wish to try and turn back the clock to before the web was available. It won't stop those who are breaking the law. It will legalize tools for government agencies to censor parts of the web. It would slow or stop the economic growth of online companies, including the ones that make blogging possible (both companies like Google's Blogger and WordPress, and also many companies that support paid bloggers with advertising).

Also, I wanted to point out that this is a bipartisan issue: members of both U.S. parties acted to delay the vote on SOPA in the House of Representatives, and members of both parties are threatening to bring PIPA to a vote in the Senate quickly before more opposition appears. And this will impact U.S. citizens (and the international community) regardless of party affiliation.

If you want to learn more about the legislation you can read about it here.

To find a representatives to contact, head over to Wikipedia's main page, or to sign a petition go here.

We'll get back to dinosaurs tomorrow!

Revisiting the Fisher King

2012-01-11T11:04:00.000-08:00

I know, I know, my last post promised a series on reconstructing Acrocanthosaurus in multiple views - bear with me, as this is actually part of that series. Remember that both animals have stuff sticking up on their backs, so I want to be able to compare and contrast those elongated neural spines...and how those differences should impact reconstructions of the animals. But to do that I had to update this skeletal, as new information had rendered the older one no longer tenable.

Besides, Spinosaurus is cool! For one, it's the only dinosaur in the Jurassic Park series to tangle with a T. rex and emerge victorious (no matter how unlikely that outcome was). It's probably the longest theropod we know of, and may have been the heaviest as well. Yet counter-intuitively it shows specialization for piscivory (fish-eating)...maybe in JP3 the spinosaur mistook the T. rex for a really large lung-fish?

Tongue firmly out of cheek now, Spinosaurus has lit up imaginations partially due to its size, but also because there was so much you had to imagine to try and reconstruct the animal. Until the last decade or two it was sort of a theropod Rorschach test where you could project any sort of oversized monster theropod onto its scant (and now lost) remains. This brings a thrilling "Sherlock Holmes" quality when trying to imagine the living animal, but for most of the last century serious attempts to reconstruct Spinosaurus have been more frustrating than titillating.

Darren Naish has an excellent write up of the history (and tragedy) of of the type specimen of Spinosaurus, which I won't duplicate here. The long and short of it is that WWII claimed the fossils as another victim of the conflict. The already-meager remains lost, paleontologists were stuck with the original description and some somewhat uninspired sketches as the only link to the past.

A series of fortunate events occurred in the latter half of the 20th century that allowed for a more accurate interpretation of Spinosaurus to emerge. For one, other spinosaurids were found. Baryonyx from the U.K., and Nigerian Suchomimus, started to paint a more complete picture of what these animals were like. They had bizarrely long snouts that seemed to resemble a gharial as much as a traditional theropod. Suchomimus even had a smaller version of the enlarged neural spines on the back:

The amusingly-named Irritator from South America further clarified the relationships and anatomy of spinosaurids. But the real breakthrough was the re-discovery of several photographic plates of the original material. While Spinosaurus wasn't the most complete specimen, having photographs at least made it possible to ensure that what was found is incorporated accurately into a reconstruction.

Among other details, the image also shows what had been the basis of attempts to restore the shape of the elongate sail or hump on the back: Stromer's original interpretation for the position of the elongated neural spines. In particular, notice that the tallest one is set directly in front of the sacrum here, while the only associated tail vertebra (at the far left of the picture) has a very short spine. That has lead most people to infer that the spine started quickly after the neck, grew to ridiculous heights over the pelvis, and then quickly dropped off again. Indeed, this is the interpretation that I used in my first attempt, and has been widely seen in such disparate and reputable scientific endeavors as Jurassic Park 3, the Carnegie Collection of "museum quality replicas", and Greg Paul's reconstruction in his Princeton Field Guide to Dinosaurs.

And they're in excellent company (whereby I arbitrarily define myself as "excellent company"). I had been concerned with Stromer's original interpretation for the placement of the tallest neural spinse - no vertebral body (centrum) was preserved, but the change in the angle of the spine seemed pretty extreme compared to the previous dorsals, especially right in front of the sacrum. My solution was to assume it was a sacral neural spine. This largely preserved the traditional appearance of the "sail", but provided a bit of breathing room for the change in orientation.

Luckily for us, Andre Cau and Jamie Headden were busy mulling over this specific issue, and came to a much more likely conclusion, that the backward-oriented neural spine was actually an anterior caudal. Looking at a host of dinosaurs with elongate neural spines, they noted that in general you never seen backward-canted spines in front of the hips, you always see them after it. There is a bit more detail to the argument (which I encourage you to read on their blogs), but in essence they make a very compelling case.

And so it was back to the virtual drawing board. I made some other corrections from my previous attempt - there had been some scaling issues with the neck vertebrae that had given my reconstruction a thinner Baryonyx-like profile in the neck. Also, it appears that the necks of these animal don't have as much of the traditional theropod S-curve, so that was changed as well (although I still don't buy the extreme hang-dog look that Greg Paul has started to restore his spinosaurs with). The results are a stockier animal, with a more elongate sail (or hump):

Looking at the rigorous reconstruction, it's clear that there's still quite a bit of uncertainty in the skeleton, although not all of the missing parts are created equal. Much of the pelvic girdle is known from Irritator, as is the back of the skull. Also, some unpublished specimens shed light on this, even if they aren't documented well enough to be official parts of the reconstruction. Still, there's a bit of ambiguity about the exact limb proportions, the length of the tail, and the exact shape of the sail.

Speaking of which, how should those tall neural spines be restored by artists doing life reconstructions? Is it a sail, was it supporting a hump of tissue like a bison, or was it simply a muscular ridge? We'll get back to that subject in a bit, after looking at Acrocanthosaurus.

Until then, best wishes to one and all for a wonderful 2012!

Happy Holidays!

2011-12-24T21:27:00.000-08:00

Happy holidays to one and all. We'll talk about that Acro skeletal and multi-view reconstructions in the New Year. Until then, be safe and enjoy the holiday season!

Please (properly) label your scale bars: Exhibit A

2011-12-20T18:15:00.000-08:00

As many of you know, I spend a lot of my time doing skeletal drawings. Not everyone does them, but I don't think I demand any special considerations in the papers I use as reference. Many of the critiques about measuring your dinosaur posted over at SVPOW are similar to what I think when I read a paper. Anyhow, in terms of typos making a scale bar useless, I think this next image speaks for itself:

That is all.

(If you're having trouble seeing what I'm talking about, read the image caption carefully)

Falcarius: bizarre sickle-cutter

2011-11-18T15:40:00.001-08:00

The truly strange looking animal above is Falcarius utahensis. It's an early, omnivorous member of the theropod clade known as therizinosaurs. Not only does it look weird, it's also a bit different from other skeletals you may have seen on the web. Join me after the break for a bit of a discussion about Falcarius, and the challenges I faced with this reconstruction.

I should warn you, this won't be a tutorial on how I make my skeletal reconstructions. That would certainly be a fun series, but it would require quite a lot of time to do properly, so for now it'll have to wait. But there are still several points worthy of discussion.

First off, the animal was discovered in a bone bed of disarticulated individuals. The good news is that most of the individual elements are known, but the down side is the bones aren't all from the same sized animals. That means that cross-scaling is needed to restore the skeleton, but even that presents a challenge; the usual method of cross-scaling involves double-checking the results against the proportions of close relatives. Alas, in this case the fossil record for the base of the therizinosaur family tree isn't well known, and what is known makes it clear that Falcarius has very different proportions than it's closest known relative: Beipiaosaurus.

When the original description of Falcarius was published in 2005, it came with the skeletal drawing at left. Obviously I don't agree with those proportions now, but at the time it had been done when fewer bones had been excavated, prepared, and described in detail, so Greg Paul had to try and scale them based on a smaller amount of material to compare with.

In fact, given the difficulty of restoring the proportions I intentionally avoided doing a Falcarius skeletal reconstruction for several years. I might have avoided it all together, but towards the end of my tenure at the WDC we mounted a cast of Falcarius that Gaston Design produced. Working on that skeleton I was able to not only measure and photograph all of the elements, but spend time looking at how the individual elements were matched up. Some parts of the cast's vertebral column are from different sized individuals (an unavoidable consequence of trying to piece together a skeleton from several different individuals). In other cases, vertebrae I had assumed to be from different sized animals were in fact crushed.

In addition to the hands-on data, Lindsay Zanno had been hard at work publishing more detailed information on Falcarius (this is actually notable, as not all researchers are as timely with getting more detailed descriptions of a new animal into print).

As the information piled up I felt that a skeletal was possible to be done. I still didn't tackle it though, as there were plenty of "low-hanging fruit" skeletals that could be done from less-challenging animals.

As luck would have it, I ended up being asked to produce a skeletal of Falcarius for a display in the new Utah Museum of Natural History building (side note: the new UMNH building just opened, and houses one of the most impressive natural history displays in North America, go see it!).

Since I was working with the UMNH, I got valuable input from several of the researchers who worked on the specimens. They were able to provide additional information - I won't go into the nitty-gritty of it (although you may if you would like), but I wanted to point out that the end result was quite a surprise to me. And little is more satisfying than when you are really surprised at the end of a skeletal reconstruction.

Resulting skeletal in hand, you can compare it to the most recent studies of the therizinosaur family tree, as well as the excellent research being done by Lindsay Zanno and Peter Makovicky on the origin of plant-eating in theropod dinosaurs, and Falcarius starts to tell an interesting tail about the order in which therizinosaur traits appeared.

Falcarius appears to already be specialized for browsing for high forage. Given the lack of an enlarged gut for fermentation it probably preferred to seek out higher-quality plant matter, like fruiting bodies or seeds. The partially upright stance appears concurrently with a widening of the passage through the pelvis (not visible in side view) allowing move guts into that area, causing the center of gravity to sit further back despite the elongation of the neck.

The large hand claws (from which the authors derived the name "sickle-cutter") may have allowed Falcarius to pick up small prey, but they also may have served as defense for a fairly slow animal with small teeth. The first toe is low and long enough to start interacting with the ground, perhaps to provide balance and stability when browsing high. All of these features would be carried to extremes in advanced therizinosaurs, but they seem to already be playing the same (albeit incipient) functional roles in Falcarius.

So with Falcarius we have an animal that at first glance appears inexplicably strange, but when viewed through the lens of where it was coming from (long-bodied small-headed meat eaters) and where it ends up (the upright, pot-bellied therizinosaurs) the combination of traits start to make a lot of sense.

Isn't science grand?

References:

Kirkland, J. I., Zanno, L. E., Sampson, S. D., Clark, J. M. & DeBlieux, D. D., 2005. A primitive therizinosauroid dinosaur from the Early Cretaceous of Utah. Nature, v435, pp 84-87.

Zanno, L. E. 2006. The pectoral girdle and forelimb of the primitive therizinosauroid Falcarius utahensis (Theropoda, Maniraptora): Analyzing evolutionary trends withing Therizinosauroidea. Journal of Vertebrate Paleontology, v26 n3, pp 636-650.

Zanno, L. E. 2010. Osteology of Falcarius utahensis (Dinosauria: Theropoda): characterizing the anatomy of basal therizinosaurs. Zoological Journal of the Linnean Society. v158, pp 196-230.

Zanno, L. E. & Makovicky, P. J., 2011. Herbivorous ecomorphology and specialization patterns in theropod dinosaur evolution. Proceedings of the National Academy of Sciences. v108 m1, pp 232-237.

Gauging stance in "wide-gauge" sauropods

2011-11-11T12:08:00.001-08:00

In 1999 Jeff Wilson and Matt Carrano published an excellent paper addressing the phenomena of "wide-gauge" sauropod trackways. For years researchers had been working to explain why sauropod trackways seemed to come in two very different flavors - some of them were very closely spaced...so much so that they would actually overlap on the midline of the track. Other sauropod tracks seemed to show animals walking with their feet spread much further apart.

What were paleontologists to make of this?

One explanation was that the trackways were made by the same type of sauropods that were engaging in different behaviors. In other words, perhaps sometimes a sauropod would walk with its legs close in, while at other times it would use a wide-gauge stance.

Wilson & Carrano proposed that instead the trackways were made by sauropods with different skeletal adaptations. They mustered quite a few lines of evidence, but perhaps the best was that there was a group of sauropods - titanosaurs - that in fact had a much wider pelvis than other sauropods. The paper created a framework for later workers to use when attempting to correlate track makers with fossilized trackways, and is generally a towering success.

But I did want to take issue with one figure of the paper - one that pops up repeatedly at SVP. It is figure 5, demonstrating their interpretation of hing leg stance:

That's Camarasaurus on the left and Opisthocoelicaudia on the right. The clever reader may have already surmised from the title of this post that I think the animal on the right has its legs spread too far apart. But I have a larger issue: both animals have their legs spread much too far apart.

Remember that narrow-gauged trackways actually have their feet fall so close together that they frequently overlap along the midline. There's no way even sauropod "A" could make those tracks in the stance as figured. And this is why I'm bringing this up, because animals generally don't walk around with their legs acting as perfectly vertical beams. If you spend time watching large animals walk away from you, you'd see something like this:

Elephant image from here, rhino image from here.

People also move like this, with our vertical limbs generally sloping in toward the midline when we walk or run. There are probably several reasons for this (including mechanical efficiency) but for our purposes here let's just setting on the fact that it happens. Large, straight-limbed graviportal animals tend to walk with the limbs angled inward, not down (and certainly not angled out).

And the trackways also demonstrate this. If you place place sauropods over the actual trackways in question, you end up with a stance more like this:

In this case I've put a diplodocid (Supersaurus) on the left, while the animal on the right is scaled to the pelvic dimensions of Opisthocoelicaudia as seen in the original paper. Both animals have the hind legs mostly vertical but gently sloping inward.

This is not to say that sauropods never adopted a pose with their legs spread out a bit; Wilson & Carrano point out that titanosaurs have adaptations that may have allowed them to evert their hind limbs more effectively. They suggest that titanosaurs may have done so when rearing up, or during other activities that require greater stability.

I don't take issue with that, and those sorts of differences in the legs and pelvis may make it possible to tease out further behavioral differences between sauropod groups. But when walking around in their day to day lives both the footprints and modern analogs make a strong case that the limbs should be vertical, and if anything sloping in towards the midline rather than spread away from it.

Reference:

Wilson, J. A, & Carrano, M. T. 1999. Titanosaurs and the origin of "wide-gauge" trackways: a biomechanical and systematic perspective on sauropod locomotion. Paleobiology, 25(2), pp. 252-267.

Um hey, Scientific American? Bird knees bend the same way as everyone else.

2011-09-30T21:08:00.000-07:00

Ok, time for a quick anatomy lesson: Despite what you may have heard, bird knees do not bend backward. Nor, in fact, do the knees of any tetrapod perform this trick. Given the role of the knee in locomotion, it's not even clear how such a reversal could evolve after the initial "knee bend" direction was settled upon several hundred million years ago.

Why bring the anatomical equivalent of a fairy tale? Well, it's a fairly common misconception. So common, in fact, that it was recently enshrined by none other than Scientific American. So let's see if we can clear this up after the break:

Really, it's not.

It's a surprisingly common mistake. When looking at living birds many people fail to realize that part of the leg is hidden on a bird; the upper leg barely moves, and along with the knee it is actually buried up under the feathers of the wing and body. Birds also have quite long ankles, leaving their ankle joints in roughly the position we'd expect the knees to be on a human. Like this:

The key here is that people are plantigrade animals, while all theropods (including birds) are digitigrade. That means that human ankles are flat on the ground, and in our case our knees are roughly in the middle of our legs. In birds and other digitigrade animals (most dinosaurs and many mammals, like dogs, deer, and horses) it's only the toes that contact the ground. The ankle joint is well up off the ground, and the knee is is actually in the upper 1/3rd of the leg. And in birds the thigh is actually even a smaller part of the leg, and as mentioned above is also mostly hidden under feathers. Here's a look comparing the same leg portions of a human (in two poses), a dog, and an extinct bird:

Presbyornis Copyright Scott Hartman, other skeletals modified after Charles Knight.

In the diagram the thigh bones (femora) are all colored red, the shin bones and proximal ankle bones are colored blue, the "foot bones" (the distal tarsals and the metatarsals) are green, and the individual toe bones are yellow. Notice that the femur of the Presbyornis is small and very high, and the knee (the joint between the red and blue bones) is up where it would be hidden by the body and wings. But please also notice...the knee is bending the same way as ours. And the same way as everything else that has a spine and walks on land.

Which brings us back to the article posted by Scientific American. I don't want to go too far with "gotcha" blogging; Scientific American is generally one of the more accurate popularizers of science on the web and in print. I took a look the other pieces published by the author, and she seems like a solid reporter that just happens to have made a mistake. Journalists don't get science degrees (and even if they did that would only be one subject), so this should not be construed as an attack.

But at the same time, this is a serious error. It's like reporting that September has 32 days in it, or that the Red Sox clinched a playoff spot this week. Only worse, as it's perpetuating a myth that gets passed around as "common knowledge". I attempted to bring this to the attention of the relevant parties shortly after it was reported, both on Google+, where SciAm blog editor Bora Zivkovic has been making effective use of the new social network, and the author's Twitter account (which is frequently used). Despite near real-time feedback, days have gone by with no correction.

Making a mistake is understandable, but failing to correct it is not. Scientific American has written hundreds of articles on the state of science education, and has often been an effective advocate for ways to improve it. But the authority they derive comes from their attention to scientific detail, so I hope we will now see a quick correction without further delay.

Talos: A troodontid with a leg up on the competition

2011-09-20T12:58:00.000-07:00

It's my pleasure to introduce the newest member of the troodontid family: Talos sampsoni. Named for paleontologist Scott Samspon, Talos was described by Lindsay Zanno and others in the wonderful open source journal Plos ONE. Talos is the first troodontid to be named from the Kaiparowits Formation of Utah, making it about 76 million years old. Cross-sections of the long bones suggest that the animal was between four and six years old, and while it hadn't stopped growing, it appeared to be reaching reproductive age at a smaller size than it's close relative Troodon. Of note is that the specimen had a bone in its second toe that was injured and partially healed. Since it appears to have been injured from violent trauma, it's consistent with with the idea that the "switchblade" toe was used in a way that could result in such an injury (presumably either attack or defense). Also, since the rest of the foot shows no indication of the sort of limping or other adjustments you see from a prolonged foot injury, it also reinforces the idea that troodontids walked with the second toe off the ground (as shown above).

I was producing the above skeletal reconstruction for the Utah Museum of Natural History, who has constructed a new building filled with exciting displays that will open this Fall. It should be a state of the art exhibit that everyone should go see if they get the chance. Dr. Zanno was working on describing Talos at the time, so I worked with her to incorporate the data into the skeletal. There is quite a bit of troodontid material from the Kaiparowits, but only a fraction of it can be confidently assigned to Talos at this time. Restricting ourselves to the type specimen looks something like this:

You could be forgiven if your first reaction is "that's not very complete!". But I was thrilled. Why? It's hard to remember sometimes, since Troodon is illustrated frequently, but the published material that Troodon is usually based on is really scrappy. Here is a quick and dirty example of what was published in Dale Russell's 1969 paper:

To create the reconstruction (then called Stenonychosaurus) of Troodon that inspired him to create his infamous dinosauroid sculpture, Dale Russell had to combine all of the material from the Asian taxa Saurornithoides (as seen below) just to create a usable composite:

That made the size of the head and pelvis more clear, and provided more back and tail vertebrae to scale from, but look at how "dotted" the outlines of the limbs are - there still wasn't a good guide for scaling the limbs of any of these advanced troodontids. A few unpublished specimens are out there, but none of those provided definitive limb proportions. Talos finally does that.

So in addition to the interesting conclusions on biogeography, ontogeny, and mode of life, Talos should be exciting to illustrators because it provides the first definitive glimpse of the limb proportions of advanced troodontids. They aren't radically different from the proportions Dale Russell speculated on in the 1960s (although the forelimbs are shorter than some people have speculated since then), but the good news is that we now know for sure. In fact at this point the only serious unknown is the neck, although there are plenty of more basal troodonts to base that on.

Running around like an Ornitholestes with it's head cut off!

2011-09-15T12:52:00.000-07:00

If you watched Episode II of Dinosaur Revolution, you may have laughed at this Ornitholetes, who I'll refer to as Ichabod. This may seem like an odd scene to pick for a scientific discussion, but I think it actually has something useful to teach. Also, I'm partially responsible. I should be clear, the story idea was not mine (that's above my pay grade), but it's something that was run by me, and I did not try to shoot it down (and still wouldn't).

Why? I think it's reasonable.

No wait, let me explain: I'll grant you that there isn't much in the professional literature on the subject on the subject of "headless running" in animals, but from some criticisms I've read I think people maybe thinking about this the wrong way (i.e., wondering about the distribution of "headless-running" in birds like the behavior it's an advanced condition).

Vertebrates as a group have one of the more centralized nervous systems among animals (with some arthropods and especially some cephalopods as the other contestants in the "flexibility over redundancy sweepstakes"), but tetrapod nervous system evolution in general is a story of progressive centralization that (so far) culminates in mammals. Even in humans, with our gobs of ridiculously calorie-hungry centralized gray matter, we still have autonomous reactions that don't require the brain to be involved (as anyone knows who's burned themselves and jerked their hand away before they felt the pain). That said, we have gone a long way down the path of nervous system centralization, and if you cut a mammal's head off you may get some twitching but it won't run around; our limbs literally cannot coordinate themselves without the brain's involvement (although morbidly it does appear that the head itself retains some coordination afterwards, if medieval reports are true that heads react for up to a 15 seconds after a beheading).

This degree of centralization is the derived condition, not the primitive one. So it seems unlikely that chickens are special here, except in as much as they more frequently get clean beheadings in the presence of human observers than most other birds (a quick Google search shows that turkey's exhibit this as well). This should be true of lizards, crocs, etc too (diapsids as a whole). So with enough experimental trials I'd fully expect an Ornnitholestes to do a good headless chicken impression. Now, I'll grant you that this would require a pretty clean bite on the allosaur's part, and the odds of observing it in the wild would not be very high. But the sequence was devised as be a surprising bit of humor in a scenario that was possible, not probable.

Given those parameters it seems reasonable enough to me.

Dinosaur Revolution Episodes III & IV on tonight on Discovery Science

2011-09-13T11:54:00.000-07:00

Just a quick note, for those looking forward to the last two episodes. They will be showing tonight on Discovery Science at 9 and 10pm (check local listings).

Reign of the Dinosaur Revolution

2011-09-08T14:46:00.000-07:00

One of the projects I've worked on the last two years was Dinosaur Revolution - although for most of that time it had the working name "Reign of the Dinosaurs" - which is still how I think of it in my head. I'm sure I'll get over it.

Two of the episodes aired this last Sunday(September 4th) and the last two air ~~this Sunday (Sep 11th)~~. (Note! The airing of episodes III & IV have been postponed, as Discovery felt that the show wasn't appropriate for September 11th. Thanks to Tom Holtz for point that out!) I'm sure there will be other showings. Anatomically-speaking, the dinosaurs will be the best to yet reach the screen (although there will be a few recent discoveries that couldn't get worked in on time). The artists working to create these dinosaurs were about as good as it gets when you need to combine talent and knowledge of dinosaurs into one package. The "story" in the episodes is more ambitious, attempting to hook viewers with no narration (although some minimal narration did get added late in production). How well it works for you is probably a matter of opinion, although I enjoyed it. Regardless, the show is well worth your time.

The reason I bring this up is over my long association with the project I've developed a new appreciation for how difficult it is to get anything on TV, let along maintain a specific scientific or artistic vision. That might actually make for a good post or two. But first I want to open this up for discussion.

So, who saw it, and what did you think? Some of you commented on Google+ - feel free to cut and paste your response over here if you want (or else come up with something even snazzier to say). I'll talk more about the experience, and the challenges, in the days to come.

Mike Habib's Great Flying Skeletals: Perspectives from Pterosaurs

2011-08-11T18:09:00.000-07:00

Today we get the second guest post on pterosaurs. In addition to his extensive background in biomechanics, Mike has started a blog with Justin Hall on biomechanics - you should check it out. Now, one with the main programming...

Great Flying Skeletals: Perspectives from Pterosaurs

Scott has graciously invited me to do a little guest post from the perspective of a biomechanist. While Skeletal Drawing focuses primarily on dinosaurs, I am going to depart a bit on this occasion and use pterosaurs to highlight some of the biomechanics issues that can occur with skeletal poses.

The Case of Running Pterosaurs
Many of you have probably seen pterosaurs reconstructed in the popular standard pose (particularly preferred by Greg Paul) where they are in mid-sprint, like so:

From here. Copyright Gregory S. Paul.

It's an impressive pose for a flying animal. A lot of people really like the look, and it lines up nicely with the same pose in birds, to which pterosaurs are often compared. There's just one (big) problem with it: pterosaurs probably never sprinted around on their hindlimbs like the reconstructions show.

In the case of pterosaurs, the "standard running pose" is typically presented as a launch pose. However, in the late 90's, Jim Cunningham made a strong case for quadrupedal launching in Quetzalcoatlus at a series of presentations for both engineers and biologists. In 2008, I published a manuscript on a sizable comparative study I ran on bone structural strength estimates in the forelimb and hindlimb, which demonstrated that most pterosaurs probably launched quadrupedally rather than bipedally.

Now, I know you're thinking "Oh c'mon, Mike, you just don't like those bipedal running pterosaurs because they conflict with your personal results. You're biased!" I may be biased in some sense, but actually, that's not the problem. I would not mind bipedal, sprinting pterosaurs if another study had used different data to support the idea. But the reality is that no analysis has ever produced support for bipedal launching in pterosaurs. In fact, so far as I am aware, my paper was the first attempt at testing between the two modes of launch. There have not been a great number of biomechanical analyses run on pterosaurs, but there were a handful back in the 1970's and again in the early 2000's. A few of these considered their performance during takeoff, and the authors all assumed a bipedal launch mechanism, as in birds. The key word there is assumed - those studies asked the question "if pterosaurs launched like birds, then how would it work out?", but they never actually tested if a bipedal run was likely. I think the first lesson here is this:

Don't reconstruct skeletal images in poses the animal was not known to reach, unless you are specifically trying to argue the plausibility in conjunction with the pose, with appropriate empirical data present.

Most viewers of a skeletal reconstruction will assume that the animal could (and did) the action shown by the skeletal pose. More discriminating viewers may consider the issue more thoroughly, but either way this gets in the way of the point of a typical reconstruction.

A typical skeletal is supposed to show off the anatomy. If the paper you are illustrating happens to be arguing for a specific dynamic action, then it makes sense to show the animal in that pose. If there is a dynamic pose that others have shown to be plausible, then that's fine, too - but not as a standard pose, because there will nearly always be some animal that you come across later that can't do it. Nearly all terrestrial vertebrates can manage a slow walk, but only some can sprint - so choosing sprinting as your standard is risky. Inevitably, something is going to end up sprinting in your illustrations that never did so in life.

We can make an animal do anything we want in an illustration. Scott made an Allosaurus do a handstand. We could make Quetzalcoatlus launch by vaulting on its beak. These extreme examples are obvious, but less extreme cases can be difficult to detect. The ability to render a good illustration is powerful, because it can make the action or anatomy suggested by the image seem plausible, even if it's completely false or fabricated. If you're an illustrator, use your powers wisely.

Where Does that Wing Go?

One really tricky issue with pterosaurs is the wings - we don't know for certain where the wings attached in most species, and even if we pick a particular attachment point, there are a range of potential resulting wing shapes (if you want to read more about this issue, check out the section on flight over at pterosaur.net).

From David Hone's blog.

Of course, the soft tissue extent need not affect a skeletal reconstruction, but the typical methodology for skeletal illustrations is to include a black body outline. Usually this can made relatively conservative and follow typical muscle contours for vertebrates, but there is still a certain amount of conjecture there. When there is a major soft tissue structure involved, like the wing of a pterosaur, this can get very tricky. Any wing profile you show will be taken much the same as a pose: the viewer will assume you are explicitly supporting that particular wing shape.

One way to get around this issue is to leave off the wing membrane. A simple black muscle contour can be drawn around the wing spar and then the wing itself can be left out. This is, from my perspective, probably the best option if one is trying to simply show pterosaur skeletal anatomy in a neutral manner. However, if your illustration is for wide audience, then be forewarned that you will probably need to make a note that the wing is left out somewhere in the caption, or else non-specialists will be very confused.

This same problem can arise with other taxa, of course, especially swimmers - flukes and fins tend to be largely soft tissue, and sometimes there is no exact match to a bony contour (look at the tails of cetaceans, for example). In those cases, leaving off the fin or fluke might be especially confusing, so some sort of estimate might be required - but again, there is a danger of extrapolation. I do not know what the best option in that case would be, though half-tone might be an option for showing speculative components.

Up and Away?

The last major challenge for pterosaur skeletal illustration is probably choosing whether to show them flying or walking. As already discussed, bipedal sprinting is not likely, but pterosaurs certainly walked around (quadrupedally, as it turns out, based on the trackways), so one could easily show them walking, which would tend to match other skeletal reconstructions and work well for the standardization aspect. However, it can be difficult to show off pterosaur anatomy well with a walking pose, because the folded wing gets in the way. Some illustrators may also prefer to remind the viewer that the reconstructed critter was a flying animal. As such, there are some good arguments for a flying pose. As a biomechanist, I tend to be happy seeing either or both options, but this does bring one final consideration for skeletal standardization, which is that any given illustrator will inevitably need multiple standards. You can't really show a mosasaur walking, for example. As such, it may be that a separate standard is needed for each major mode of locomotion - flyers, swimmers, and walkers, as it were.

There are additional concerns that could be raised for pterosaurs, and for biomechanics interests, but those three general issues (plausible posing, soft tissue suggestion, and multi-modal animals) are some of the factors that speak most quickly to biomechanists like myself. Happy reading! Thanks again to Scott for the guest slot.

--Mike Habib

John Conway's Note from Pterosaur-land: End the Lateral Tyranny!

2011-08-09T10:57:00.000-07:00

Today we have the first of two guest posts that look at skeletal reconstructions from a more pterosaur-centric point of view. I feel these posts (and there will be some more guest posts on other subjects in the not-too-distant-future) are really important. First, it helps break the stranglehold that dinosaurs have had on the subject matter thus far on SD Blog. And second it diversifies the voices heard on the issues that impact the science behind reconstructing extinct animals. And finally, they mean I can get by while doing less work.

First up is a message from John Conway, pterosaur skeletal drawing-er extraordinaire (all images belong to John), who also contributes to Pterosaur.net:

A Note from Pterosaur-land: End the Lateral Tyranny!

When I first started to draw skeletals, I still very much wanted to be Greg Paul when I grew up. But even so, I was not entirely happy with the sprinting pose he uses, I felt then, as I still do, that it’s too extreme, too hypothesis-laden, and unsuitable for many animals.

I tried walking poses and static poses, but never really settled on a standard. But its wasn’t until I started my first serious skeletals of pterosaurs that I really gave the matter of posing serious consideration. I gave it serious consideration because I had to: the running launch pose that Greg Paul was using is biologically inaccurate, and most walking poses for pterosaurs seriously obscure their anatomy.

Greg Paul notes that he ignores the slight foreshortening that would be apparent because of the bow in dinosaur legs. And that’s fine for dinosaurs, because the effect is tiny. Not so for pterosaurs, as their semi-erect stance would foreshorten the humerus (possibly) and the femur significantly, meaning lateral-view skeletals give misleading information about pterosaur proportions. I was still interested in a standards pose for all the animals I was interested in, but I just couldn’t think of one. So I gave up, and just went with something that would best elucidate pterosaur anatomy: a three-view skeletal with the limbs arranged in the only biologically plausible, non-foreshortened way I could think of.

As time goes by, I’ve come thing think I made a good decision. Every single time a sit down to do a skeletal, I find that the doing three or more views requires me to correct errors that I would have missed if I were just doing lateral or dorsal views. It works for just about any vertebrate (be it a sprawler, a strider, a hopper, or what ever)

However, I will admit that these skeletals aren’t exactly the most space efficient things in the world, and they may be a little dry for some contexts. However:

Gentlemen, We Can Repose Him, We Have the Technology!

Most people these days are using vector drawing programs like Illustrator to create skeletals (and if they aren’t, they should be). It is trivially easy to move these skeletals into just about any pose we like.

When I’m making a skeletal, usually it’s for my own reference, as a base for a life-reconstruction. For this purpose, multiple views are critical, posing much less so. Posing may be more important when we are trying to make a biomechanical point, or in popular works were we are trying to get across more information about the biology of the animal. Different contexts lend themselves to different poses, and perhaps we should be working with that, not against it.

So to end, I think it very doubtful that we will be able to come up with a standard pose that works for all vertebrates—and nor, perhaps, should we. Perhaps it is good enough to aim for clearly and accurately elucidating anatomy, posing depending on context.

-John Conway

Neutral Poses & Elmerfuddasaurus

2011-07-22T10:01:00.000-07:00

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.

What do you guys think?

Skeletal Poses: Do they matter?

2011-07-19T17:46:00.000-07:00

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.

From here; artist unattributed.

To some degree this is where we get to the crux of disagreements - people are often quick to critisize as outlandish the problems that appear at the macroscopic level (Allosaurus can't do a handstand!) while ignoring the problems that are less overt, or at least the ones that fall out of their range of knowledge. 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

2011-07-16T17:07:00.000-07:00

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 afore-mentioned 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 just with me, feel free to email me and I can incorporate your concerns into a future discussions.

Schematic vs realistic skeletals: Follow up

2011-07-15T09:59:00.000-07:00

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

2011-06-16T08:48:00.000-07:00

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 is inaccurate, which is odd because 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 scienntists 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 paleo art 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 parasagital 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...

2011-06-12T09:37:00.000-07:00

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

2011-03-29T13:54:00.000-07:00

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!

We'll figure out how to avoid this gruesome mistake after the break...

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:

The dromaeosaur is apparently snarling in pain (from here)

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 TM) the image would look something like this:

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 th 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.

A History of Skeletal Drawings: Part 3 - Dino Renaissance to the present

2011-03-26T15:00:00.000-07:00

We saw in Part 2 that the modern convention of skeletal illustration had largely been invented by the 1950s. Alas, it didn’t immediately catch on like wildfire, and in other ways the 1950s represents a nadir in terms of published skeletals. Yet starting in the 1960s would see steady progress up to the modern era. How did it all happen? Let’s take a look!

Dinosaur Renaissance, Skeletal Evolution:

Most accounts of the Dinosaur Renaissance start in the late 1960s. And it’s true that this period saw rapid change in the peer-reviewed literature on dinosaur biology; John Ostrom, Robert Bakker, Peter Galton and others helped drive a period of time that saw paleontologists unite dinosaurs back into a single evolutionary group, add birds to that group, and re-evaluate the metabolism and growth rates of dinosaurs. Certainly the renaissance witnessed a push to make dinosaur reconstructions more accurate, and a revival of interest in functional morphology. Yet the seeds of that change were sown in the early 1960s.

Of course scientific ideas also have historical backdrops. Ostrom is generally credited with ushering in the idea of endothermic dinosaurs with his 1969 paper (enticingly titled: Terrestrial vertebrates as indicators of Mesozoic climates). Yet it was preceded by papers by L. Russell (1965), Currey (1965), and Wieland (1942), all discussing endothermic dinosaurs. Not that their work diminishes the impact that Ostrom and other architects of the modern era had in the 1970s, but as both scientists and scientific illustrators it behooves us to always be aware of context. So let’s jump back to see the beginning of the skeletal renaissance:

Young's 1954 Mamenchisaurus. Not real renaissance-y.

Much of the worlds' economy was recovering nicely in the post-war era, and the world had just seen its first black-silhouetted skeletal drawings. Yet there seems to have been a general malaise in the realm of dinosaur reconstructions in the 1950s. Professor Young continued to push out an outlined skeletal or two, but if anything his outlines seemed to get less accurate as time wore ont By 1960 he dropped the convention altogether in his description of Shansisuchus.

Young’s example is in many ways symbolic of the problems that plagued the field. There were no current anatomical guidelines for producing soft-tissue outlines; earlier attempts by Romer and others to reconstruct muscles were ignored or forgotten. Even the articulation of major skeletal elements varied between researchers without apparent rhyme or reason. In short, there was implicit cynicism about even attempting scientific rigour with skeletal reconstructions.

So Young to be so cynical

The 1960s brought the beginnings of revolution. Not the flower-powered one you may be thinking of, but anatomical reconstructions that deserve our admiration and respect. The first (and perhaps most overlooked) of the proto-renaissance workers was Alick Walker. Often maligned due to his stance on bird origins, Walker was a true comparative anatomist, and took great effort in his descriptive monographs. He also happened to be an excellent scientific illustrator.

When he published his dissertation on Stagonolepis it contained not one, but two multiple view skeletal reconstructions, demonstrating both the anatomy and the armor of the aetosaur (armored one shown below). Perhaps even more importantly the text of the paper includes an entire section entitled "Reconstruction of the skeleton" in which he explicitly lays out the assumptions he worked from.

Walker's 1961 Stagonolepis, an uncelebrated progenitor of the modern era

In many ways this humble aetosaur is the first skeletal reconstruction of the modern era. Not because the anatomical details are unassailable, but because great care was taken to provide all of the relevant information for others to study and improve upon. And really, who doesn't like multi-view skeletal reconstructions?

Walker's career was typified by a small number long descriptive works, so his skeletal reconstructions were not great in number. He did produced a few more skeletals of note; his 1964 Ornithosuchus (while in a Godzilla pose) was well proportioned and fairly modern. He also continued the Huene/Wright school of schematic skeletal reconstructions for his Hallopus paper. This style of skeletal reconstruction was about to make a comeback, and it’s hard to imagine that Walker’s use of it wasn’t influential.

Walker's 1970 Hallopus in the Walker/Wright style

Of course Walker wasn’t the only one publishing archosaur papers in the 1960s. John Ostrom named a new species of Parasaurolophus in 1963, and Ewer’s monograph on Euparkeria provided a skeletal of a sprightly Euparkeria in a bipedal dash. Neither was as inspired as Walker’s reconstructions, but Ostrom's work was to have a larger impact on the public conscience in 1969, when a skeletal reconstruction of his new dromaeosaur was published:

Ostrom's 1969 Terrible Claw skeletal reconstruction

Deinonychus inspired many of Ostrom’s changing views on dinosaur metabolism, and its discovery is rightly seens as pivotal event in the Dinosaur Renaissance. But things were moving quickly now on the skeletal drawing front. 1969 also saw Dale Russell publish an excellent description (and skeletal reconstruction) of Troodon. The reconstruction was well proportioned, and he appears to have taken a page from the Huene/Wright/Walker playbook when he had to outline missing portions of the vertebral column.

Sure Russell's 1969 Troodon looks nice, but how
would it look with a giant head and lacking a tail?

Dale Russell published several new skeletal reconstructions during the 1970s (and up till today), and they were excellent examples of an exciting new trend. In the past it was notable if a skeletal drawing got either the shape of the bones right, or the general proportions. Russell somehow managed to both provide accurate skeletal proportions and accurate representations of individual bones. If you compare Dale Russell’s Daspletosaurus to that of Greg Paul, you’ll see that the the only substantive difference is that Russell arched the back up, while Paul arched his down (Greg is correct in this case).

Hot on the heals of Dale Russell's debut, Peter Galton started a prolific career of skeletal reconstructions in 1970. Like Russell, his reconstructions were accurate at both capturing the general proportions of the skeleton, as well as the specific shapes of individual bones.

Galton's 1970 Edmontosaurus and 1971 "prosauropods" are accurate in both proportion and detail. What a show off.

Let's pause to catch our breath; Galton and Russell were producing some of the finest dinosaur skeletal reconstructions ever seen, Ostrom was finding crazy new theropods and stirring the pot on dinosaur energetics...honestly it feels like an embarrassment of riches were suddenly heaped upon dinosaur paleontology in the blink of an eye. Yet things were about to get kicked up a notch; Ostrom’s student (and frequent Galton collaborator) Robert Bakker published a series of papers - not to mention skeletal drawings - throughout the 1970s that really put the "Bam!" in the Dinosaur Renaissance

Much has been said about Bakker’s scientific role, but here we will concern ourselves with his contributions to the evolution of modern skeletal reconstructions. That story begins in his 1971 reply to critics in the journal Evolution, where he provides multi-view skeletal reconstructions of Struthiocephalus and Centrosaurus. Interestingly, they are comprised of solid black bones, with only a partial outline around the centrosaur. In some ways a style reminiscent of Scheele’s alternate skeletons in Prehistoric Animals (only without the eyeballs!).

From Bakker's 1971 Evolution reply.

In 1974 Bakker and Galton wrote a paper with the modest goal of reuniting ornithischia and saurischia back into a single Dinosauria. Not only where they very successful, but in the process they provided a figure with not one, or even two, but three skeletal reconstructions with black profile silhouettes. The animals are all posed similarly for ease of comparison - pushing off on their left foot in a fast run. The pose isn't identical to the one eventually adopted by Greg Paul, but the influence seems clear.

From Bakker & Galton's 1974 Nature paper.

About this time a young Greg Paul had started to experiment with making skeletal and muscle reconstructions. In a trip to Robert Bakker’s lab in the late 1970’s he saw Bakker’s silhouetted multi-view skeletal reconstruction of a galloping Triceratops. Clearly it made an impression on him, and he started to put together skeletal reconstructions in a similar style soon thereafter.

Galloping Triceratops, Copyright Robert Bakker, image from here.

Bakker continued to produce skeletal reconstructions, including ones in the black-silhouetted mold. His 1986 book The Dinosaur Heresies is filled with different twists on this convention. One consistency Bakker has shown is a preference for stippling or line shading to convey depth to the bone structure, rather than the more minimalist white on black adopted by Greg Paul and others.

Bakker’s book did much to inspire another generation of dinosaur enthusiasts (not to mention researchers), but it was another book that really introduced the modern skeletal reconstruction a wider audience: Greg Paul's Predatory Dinosaurs of the World. To a degree I expect reading this part is sort of like watching Star Wars: The Phantom Menace since you already know how it will end. And 20 years later it's easy to be cynical about it. But he impact of the book on people interested in dinosaur anatomy, especially artists, is hard to overestimate; at the time no one had every assembled such a large collection of modern skeletal reconstructions between the covers of a single book. But it wasn’t just numerical count that impressed; the skeletal reconstructions were of closely related animals (theropods, it turns out) and were all in the same pose following the same set of anatomical assumptions. That made it possible to observe subtle differences in proportions, morphology, etc., without having your eye be mislead by inconsistenties of interpretation (shoulder blade placement, for example).

Elaphrosaurus in PDW, copyright G.S. Paul.

Professional reaction to the science in the book was mixed, but the long term impact on the field of skeletal reconstructions is incontrovertible. Combined with Paul's 1986 article on how to draw dinosaurs and his 1989 article explaining his technique for producing skeletal reconstructions, the popularization of the style would extend far and wide. Established researchers began to adopt the convention as well; just two years later in his 1990 memoir on basal archosaur relationships Paul Sereno adopted the black silhouette convention, as well as posing his skeletals consistently in a left-foot-pushing-off pose. His half dozen new dinosaur species described over the coming decade would all sport similar skeletal reconstructions.

Sankar Chatterjee, who had been producing line skeletal reconstructions for some time, also adopted the black silhouette convention (albeit with no consistent pose) in 1997 and has largely stuck to it as well.

Chatterjee's "optimistic" 1997 reconstruction of Protoavis

It was in this environment that I started attempting skeletal reconstructions. I started in the mid 1990s (there was a little known dinosaur movie that had helped to reignite my interest in dinosaurs), but it would take 4-5 years before I was producing skeletals I would view now as “professional”, and not until 2002 that I started to adopt the format using the inset rigorous version. That format evolved from an idea that I picked up from Russell Hawley.

This hack's artwork keeps popping up on my blog

Today of course the black silhouette is the norm rather than the exception. When new animals are described is has become de rigueur for a skeletal reconstruction to be published along side it, and more often than not it has a black silhouette around it. The primitive theropod Tawa is an excellent example of this. From established paleoartists like Mark Hallett, to more recent ones like John Conway, Jaimie Headden, and others too numerous to mention, it has become the standard way to represent skeletons. I should also note that many excellent artists around the globe have adopted this technique, with strong showings in South America and continental Europe in the last five years. Last year Greg Paul released a field guide of all of his dinosaur skeletals, making it feel like a true golden age for the study (and representation) of dinosaur anatomy.

Yet all is not well, and storm clouds have recently gathered on the horizon. Several weeks ago Greg Paul made a public statement that outlined stricter and less generous guidelines on who could use his work as a basis for life reconstructions (a refined official statement can be found on his website that I expect supercedes any other posts), and laid claim to the pose that his skeletal reconstructions popularized. Many of his complaints reflect a reasonable desire to not be ripped off by others who simply copy what he has done and call it their own. Some other requests are perhaps more dubious, but not being a copyright lawyer I will refrain from taking them up here. The take home message is that it is already impacting the field of skeletal reconstructions, and not always in good ways.

This concludes the history of skeletal drawings. For those who would have liked a more detailed look at the last decade, all I can say is we're still living that history, and I'm somewhat gun-shy about making claims about how influential a given event or artist when so little time has passed. I doubt many realized the importance of Knights book on animal illustration for paleontology, nor did many recognize Walker's work on Stegonolepis as anything more than an excellent monograph. It's after the fact that it becomes clear where the inflection points are in history. So hurry up and do your best work, so that future generations of bloggers may include our names in a favorable light.

Instead it's time to look to the future, post Paulageddon. It's time to take a hard look at what it means for skeletals, and what we can do as a community to produce some good from all of this. I will probably have a couple of anatomy posts in the interm, as they are quicker to produce (and let's face it, what the blog is really about), but fear not; skeletal reconstructions and the issues that surround them will be on a reoccurring theme here at SD Blog.

Happy paleoarting!

References

Bakker, R.T. (1971) Dinosaur bioenergetics - A reply to Bennett and Dalzell, and Feduccia, Evolution. v28, n3, pp 497-503.

Bakker R.T. & Galton, P.M. (1974) Dinosaur monophyly and a new class of vertebrates, Nature v248, pp 168-172.

Currey, J.D. (1962) The histology of the bone of a prosauropod dinosaur. Palaeontology. v5, n2, pp 238-246.

Ewer, R.F. (1965). Anatomy of the thecodont reptile Euparkeria capensis Broom, Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences. v248, n751, pp 379-435.

Galton, P.M. (1970) The posture of hadrosaurian dinosaurs, Journal of Paleontology. v44, n3, pp 464-473.

Ostrom, J. (1969) Terrestrial verebrates as indicators of Mesozoic climates. Proceedings of the North American paelontological convention, Field Museum of Natural History.

Paul, G.S. (1986). The Science and Art of Restoring the Life Appearance of Dinosaurs and Their Relatives: A Rigorous How-To Guide. Dinosaurs Past and Present Volume II (eds. Czerkas, Olson), Natural History Museum of Los Angeles County Press.

Paul, G.S. (1988). Predatory Dinosaurs of the World: A Complete Illustrated Guide. Simon & Schuster, pp 464.

Paul, G.S. & Chase, T.L. (1989). Reconstructing extinct vertebrates. In The Guild Handbook of Scientific Illustration, Van Nostrand Reinhold, pp 239-256.

Russell, L.S. (1965) Body Temperatures of Dinosaurs and its relationships to their extinction. Journal of Paleontology, v39, n3, pp 497-501.

Walker, A.D. (1961). Reptiles of the Elgin area: Stagonolepis, Dasygnathus and their allies, Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences. v244, n709, pp 323-373.

Walker, A.D. (1970) A revision of the Jurassic reptile Hallopus victor (Marsh), with remarks on the classification of crocodiles. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences. V. 257, N. 816, pp 103-204.

Wieland, G.R. (1942) Too hot for the dinosaur! Science, New Series, V.96 N.2494, pp359.

Young, C. (1960) The pseudosuchians in China, Palaeontologica Sinica. New Series C, N. 19.

A History of Skeletal Drawings: Part 2 - Bone Wars to the 1950's

2011-03-20T19:12:00.000-07:00

As we saw in Part 1, the 19th century saw the rise of many of the modern conventions we see in skeletal reconstructions. Yet the last two decades of the century closed without any innovations, and at times a retreat from proportional accuracy. In short, skeletal reconstructions became more schematic in nature. Yet the creation of the modern silhouette skeletal reconstruction evolved in the first half of the 20th century. Why did skeletal drawings see an initial fall? And when did the modern form get invented? Let’s take a look...

The Fall and Rise of Skeletal Restorations

Before we begin with the doom and gloom, I want to take care not to give off the wrong impression about the Bone Wars. It was a fascinating and productive time in the history of paleontology, and the results were a treasure trove of fossils that still delight artists and scientists more than a century later. Yet the time period had a chilling effect on the field of producing skeletal reconstructions. No body outlines were put on skeletal reconstructions for decades, and the skeletals that were published often were erroneous in their general proportions.

Marsh's Stegosaurus, sporting a bodacious mohawk

So what happened? There seem to have been several factors at play. As the 19th century closed Europe was coping with the social, economic, and political issues that would eventually lead to WWI. As intellectual giants like Cuvier and Owen died, scientists of similar calibre were not stepping into the field to replace them. The U.S. on the other hand was rapidly pushing back their western boundaries post Civil War and was eager to demonstrate its growing scientific prowess. With the increase in publications during the Bone Wars, the bulk paleontology publications started to shift to North America. The U.S. had a different (and shorter) set of academic traditions than Europe, and one area it lacked was in comparative anatomists. Cope, for example, was very interested in evolutionary mechanisms (his 1897 book The Primary Factors of Organic Evolution is a fascinating insight into how trivialized natural selection had become to most biologists by the late 19th century), but he did not spend his free time dissecting modern animals to learn their soft tissue anatomy.

The specimens themselves were also frequently different, especially in their mode of preservation. Many (though not all) of the fossils we looked at in Part 1 were of the type that are embedded in slabs, or otherwise excavated with their buried position largely intact. The fossil finds at Como Bluff and Hell Creek were the opposite; they usually come out of the ground one bone at a time. Quarry maps were a nascent field and not generally as precise as we see today. It's also worth noting that most of the dinosaurs named during the bone wars were not actually mounted until midway through the first decade of the 20th century. All of these factors would have made it more difficult to judge and measure proportions.

Cope's Camarasaurus on the left, Compsognathus on the right. I admit it, Cope had it harder (images from here and here)

So in short; both the fossils and the scientists that starred in the Bone Wars were very different from what had come before, and the results were less than satisfying skeletal reconstructions. And it would take several decades before things would fully recover.

That’s not to say there weren’t skeletal reconstructions that were published. But for the first couple decades they tended to resemble those popularized in the Marsh and Cope monographs. Below are the first two published skeletal reconstructions of everyones favorite dinosaur, Tyrannosaurus rex:

Godzilla... I mean. T. rex, from the 1905 and 1906 papers on the beast.

One significant change that did arise in the opening years of the 20th century was photos. Thanks to the relentless march of technology photographic cameras became more widely available to scientists (and their assistants) in the early 20th century. As a result many of the monographs that traditionally would have included illustrated skeletal reconstructions instead sported photographs of the mounts. An early example is Brown’s 1905 description of Champsosaurus.

Not a stickin' drawing, but at least it comes in two different views

While the appearance of photography may have hindered the number of skeletal drawings executed, there were certainly benefits; individual bones could be represented more accurate (and eventually at less cost) than traditional plate illustrations. In the 1910s several skeletal reconstructions were made not from observation of the bones directly, but from projections made from photographs. Our good friend T. rex demonstrates this new fad in Osborn’s 1917 paper:

Still posed like Godzilla, but the bones are proportionately accurate!

Several classic skeletal reconstructions were published in the 1910s, including Brown’s 1914 “Monoclonius” and Lambe’s 1917 Gorgosaurus, but all looked eerily like those you see above. In the highly productive 40 years of American paleontology that started with the Bone Wars very little was done to expand the boundaries of the formal skeletal drawing; in the end the largest innovation was to start using photographs as a way to get the proportions correct...as they had largely been before the Bone Wars.

Over in Europe there were a few hints of what might have been. As discussed in Part 1, Seeley’s Dragons of the Air did contain modern looking skeletal reconstructions of pterosaurs (some with outlines) in 1901. In 1909 Othenio Abel drew such a giant skeletal reconstruction with body outline for the Frankfurt Senckenberg Museum of Natural History to help the staff understand how the bones of Diplodocus went together. The extremely colorful Baron Franz Nopcsa was taking an interest in the physiology of dinosaurs and would eventually contribute outlined skeletal reconstructions.

From Ilja Nieuwland's The colossal stranger (1910) - kindly supplied by the author. Original published with kind permission by the Senckenberg Museum of Natural History, Frankfurt am Main, Germany

Had the situation in Europe been more conducive to paleontology, perhaps we would have seen a continuation of the thought begun in the 19th century. But it was not to be, and World War I put paleontology on the back burner for most of the decade. Ideas must have been fomenting on both sides of the Atlantic, as almost immediately after the war we see a strong re-emergence of the outlined skeletal reconstruction, and widespread interest in paleobiology. Nopcsa produced a remarkably wrong reconstruction of Tanystropheus, which he mistook to be a pterosaur relative and named Tribelesodon in 1922. Heilman also contributed outlined skeletal drawings in his The Origin of Birds. But the real champion of the Roaring ‘20s was Friedrich von Huene. The entire decade was filled with his skeletal reconstructions; in addition to reviving the body outline, von Huene also demonstrated a strong concern for proportional accuracy. Some of his sauropods show a fairly modern feel.

Huene's remarkably modern-looking Titanosaurus skeletal reconstruction

This time the United States was not totally left behind. Richard Lull published what was probably the first American skeletal reconstruction with an outline in his 1921 redescription of Nodosaurus, and a couple of years later Gilmore did the same for his 1924 description of Stegoceras.

Huene's Procomsognathus standing and crouching - note the style of the crouched illustration

Alfred Romer made a different sort of contribution to the field, when he started to publish his systematic restorations of the muscles of extinct animals. It’s easy to imagine his comparative anatomical work making the ghosts of Cuvier and Owen smile. The idea of reconstructing muscles explicitly like this was mostly a haphazard affair for decades, but it was the sort of work necessary if the outlines around skeletons were ever to be more than artistic doodles.

Romer's restoration of the thigh muscles of T. rex

The 1930s saw the Great Depression, and with it a corresponding decrease in paleontological publications. Once again attempts to scientifically restore the functional anatomy of dinosaurs stagnated. In Lull’s 1933 Revision of the Ceratopsia there is a wealth of photographs and illustrations of fossils, but only a single skeletal reconstruction:

The lone(ly) skeletal drawing in Lull's revised Ceratopsia monograph

Von Huene continued to publish, but at a reduced rate. Gilmore put out a landmark osteology on Apatosaurus, with a skeletal reconstruction reminiscent of the monographs of Cope and Marsh (which to some degree was probably intentional). Loris Russell did a Romer-esque full-body muscle reconstruction of Chasmosaurus, but for the most part it was a lost decade.

L. Russell's flayed Chasmosaurus, understandably cringing in terror

World War II further depressed the rate of paleontological publications, yet what was published shows that things had started to perk up. In China C. C. Young showed he was influenced by Huene's skeletal reconstructions, although anatomically-speaking the outlines sometimes appeared to be afterthoughts.

Well, at least he's trying (Young, 1942)

When Lull and Wright put out their monograph on hadrosaurs in 1942 it was in stark contrast to Lull’s ceratopsian monograph of the previous decade; it was chock full of skeletal reconstructions, including several illustrations by Nelda Wright that hearkened back to Huene's 1921 crouching Procomsognathus. She polished the idea, and the images were to directly influence the dinosaur renaissance in the 1970s.

Nelda Wright channels von Huene

In the mid 1940s came an event that would have massive influence down the road. The famous paleoartist Charles R Knight put out a book called...well, actually there’s a bit of a small mystery there. Most everyone refers to the book as Animal Drawing: Anatomy and Action for Artists. But the hardback copy I have from 1947 is actually called Animal Anatomy & Psychology for the Artist and Layman. Really, here’s a scan of the cover:

See?

As near as I can tell the title that is common today was given to the reprints done in the 1950’s, and has carried over to the present. Regardless, inside the book - which has nothing to do with prehistoric animals at all - are images that can amaze and astound us in the present.

Chaz Knight's skeletal of an Asian elephant

That’s right, full blown skeletal reconstructions with black silhouettes for the muscles was invented by none other than Charles Knight, paleoart superstar!

More of Knights black-silhouetted skeletal drawings

The book also contains many lovely drawings of the musculature of living animals. Given the preeminent role played by Knight in the history of paleoart, the work in Drawing Animals seems both brilliantly ahead of its time and also a lost opportunity. Romer had started to publish his muscle restorations of dinosaurs (and other extinct animals) in the 1920s - one can easily imagine a world where fully illustrated muscle reconstructions and black-silhouetted skeletal drawings of dinosaurs had been with us for 6 decades.

Of course the marriage of Knights paleoart and his drawing conventions for living animals did not take place. The Knight-look was first applied (with several variations) to paleontology by William Scheele in his 1954 book Prehistoric Animals.

Scheele's Struthiomimus....sloooowly pushing off on its right foot

At times Scheele seemed to be channeling a bit of Nelda Wright as well, as he experimented with different forms of outlined skeletal reconstructions throughout the book.

Scheele's Ornitholestes, complete with eyeball (!) in the skull

To understand how rapidly this unfolded, remember that from the 1880s to 1940 very modest progress was made with skeletal reconstructions. Most came from Europe (and particularly from von Huene). Perhaps the kindest thing that could be said 60 years after the Bone Wars began was that skeletal drawings had gotten back to the variety and accuracy seen leading up to the Bone Wars. Yet during and immediately after WWII (despite an overall decrease in the number of paleo publications) we saw rapid innovation. Outlined skeletal drawings show up on three different continents, new forms are invented and/or resurrected by Nelda Wright, Charles Knight, and those conventions are synthesized a little later William Scheele.

What happened? There is no obvious answer for this burst of creativity. Knight had actually been moving away from paleoart after the death of Henry Fairfield Osborn in 1935. It seems clear that Scheele was influenced by both Knight and Wright, but there are no direct records and now it's too late to ask anyone. The rest of the 1950's played out fairly quietly. But the stage had been set for the great flowering of skeletal reconstructions we have today. In Part 3 we'll (finally) get to the modern period, and see how skeletal drawings were influenced by the Dinosaur Renaissance, and vice versa.

References: WIP

Knights, C (1947) Animal Anatomy & Psychology for the Artist and Layman.
Rudwick, M.J.S. (1995) Scenes from Deep Time. University of Chicago Press, 294 pages.
Seeley, H.G. (1901) Dragons of the Air. William Brendon & Son, Plymouth.