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Bovids to the right of me, pinnipeds above, what's a guy to do but squee?

Bovids to the right of me, pinnipeds above, what’s a guy to do but squee?

I’ve been doing some osteological studies of the patella (bone in the major tendon in front of the knee; termed a sesamoid) that have included frequent visits to the Natural History Museum’s avian skeleton collection at Tring. It’s a cute little town, northeast of London, in the green county of Hertfordshire where I live and work. The museum at NHM-Tring is a great old school multi-storey display packed with skeletons and stuffed animals in dark wood cabinets, with many critters hanging from wrought iron railings or other suspensions above (see above). I blogged about the Unfeathered Bird exhibit (and book) that just finished up its tour there yesterday. And I’ll be blogging later, as I keep promising, about the cool things I’ve learned during the past year of my studies of the form, function, development and evolution of the patella.

As an aside, I heartily recommend doing research at the NHM-Tring. It’s away from the bustle (and arduous Tube trip) of the South Kensington NHM, and the curatorial staff are immensely helpful… and there is something else that makes the trip even more enjoyable, but you must read more below to find out about it.

Stomach-Churning Rating: 2/10; 150-year-old dry bones. But an advance warning to (1) diabetics and (2) pun-haters, for reasons that will become evident.

Dr Heather Paxton and Dr Jeffrey Rankin, postdoc researchers working on our collaborative BBSRC chicken biomechanics grant (see thechickenofthefuture.com), explain their science to an attentive Darwin.

Dr Heather Paxton and Dr Jeffery Rankin, postdoc researchers working on our collaborative BBSRC chicken biomechanics grant (see thechickenofthefuture.com), use the Structure & Motion Lab whiteboard to explain their science to an attentive Darwin.

Today I have a short pictorial exhibit of something wonderful I ran into while patellavating in the NHM collections. As often happens while doing museum research, I had a serendipitous encounter with a bit of history that blew my mind a little, and had me geeking out. These things happen because museum collections are stuffed with specimens that, to the right eyes or the right mindset, pack a profound historical whallop. As a scientist who is pretty keen on chickens (Gallus gallus), there are probably no museum specimens of chickens that would get me more excited about than the chickens Darwin studied in his investigations of artificial selection. In fact, most museum specimens of domestic chickens would not be that interesting to me, especially after seeing these ones.

Darwin wielded the analogy between artificial selection and his conceptual mechanism of natural selection in the first ~4 chapters of On the Origin of Species to clobber the reader with facts and try to leave them with no doubt that, over millennia, nature could craft organisms in vastly more complex and profound ways than human breeders could mould them over centuries. While people most often speak of Darwin’s pigeons when referring to Darwin and avians or artificial selection and variation, his chickens appear in The Origin and other writings quite often, too (most prominently, The Variation of Animals and Plants Under Domestication in 1868– more about that here). For example, from my 1st edition facsimile of The Origin from Harvard University Press, pp. 215-216:

Natural instincts are lost under domestication… It is not that chickens have lost all fear, but fear only of dogs and cats, for if the hen gives the danger-chuckle, they will run… and conceal themselves in the surrounding grass or thickets; and this is evidently done for the instinctive purpose of allowing, as we see in wild ground-birds, their mother to fly away. But this instinct retained by our chickens has become almost useless under domestication, for the mother-hen has almost lost by disuse the power of flight.”

Well told, Mr D!

I am also reminded of how chickens and Darwin have had darker relationships, such as this sad story. Or how evolution via Darwinian mechanisms crosses paths with pop culture in fowl ways, such as how tastes-like-chicken evolved, or how some say that chickens, over great periods of time, have been naturally selected in such a way that they are now heritably predisposed to cross roads, or that the amniote egg preceded the evolution of the genus Gallus by some 325+ million years. I see I am drifting and drifting further away from the topic at hand, so let me segue back to Darwin’s chickens. We’ll take this corridor there:

Inside the avian osteology collection at Tring. Sterlie at it might seem, places like this are  fertile breeding grounds for scientific discovery.

Inside the avian osteology collection at Tring. Sterile at it might outwardly seem, places like this are fertile breeding grounds for scientific discovery. And a sterile-looking collection means well cared-for specimens that will persevere for future discoveries.

So anyway, when museum curator Jo Cooper said to me something like “I have some of Darwin’s chickens out over on the other counter, do you want to have a look or shall I put them away?” my answer was quick and emphatic. YES! But only after lunch. I was hungry, and nothing stops me from sating that hunger especially when the sun is out and there are some fine pubs within walking distance! I settled on the King’s Arms freehouse, and had a delicious cheeseburger followed by a spectacularly good apple-treacle-cake with ice cream, expediently ingested while out on their sunny patio. Yum! I cannot wait to have that cake again. What a cake! Darwin’s bushy eyebrows would have been mightily elevated by the highly evolved flavour, which would have soothed his savage stomach ailments. He would have been like:

Damn, Emma! Holy s___ this is great apple-cake; here, try some! There is grandeur in this tasty cake, with its several flavours, having been originally cooked into a few baking trays or into one; and that, whilst this pub has gone on serving fine food according to the fixed hygiene laws of Tring, from so simple a beginning endless foods most beautiful and most wonderful have been, and are being, devoured.” And Emma, cake then firmly in hand, would have said something like, “My dear Charles, I shall try this enticing dessert, and I am glad to see you so enthused about something other than barnacles. Write a letter to Huxley or Lyell about that cake later. You need to focus on concocting an ending to that big species book of yours, not cakes. It’s been 20 bloody years, dude; cake can wait. End the book on a high note.” And so it must have happened.

Working at a museum collection is like having an extra home/office for a day or more. You get familiar with the environment while working there, and start to settle in and enjoy the local environs while taking work breaks. Or I do, anyway. So this post is also partly about how cake and other provisions are an important part, or even a perk, of life as a visiting museum researcher. Put in some good solid work, then it’s cake time, but where are the cakes? You explore, and you discover them– opening the door of an unfamiliar shop or pub near a museum can be like opening a museum cabinet to discover the goodness inside. Just don’t get them mixed up. Museum specimens: for research; subjects for science. Cakes: for eating; fuel for scientists. Got it?

But I digest digress. This post is not about my lunch. Not so much, anyway, although I did enjoy the cake quite a bit. Back to the chickens. Here, try some!

Darwins-chickens (1)Darwins-chickens (6)

Darwins-chickens (5) Darwins-chickens (4)

Above: Views of Darwin’s chickens laid out at the NHM-Tring.  (all photos in this post can be clucked to emchicken them)

The chickens, much like the pub lunch, did not disappoint in the least. Here I had before me Darwin’s own personal specimens, which I envisioned him dissecting and defleshing himself, studying them in deep introspection, then handing them over to the museum for curation once his lengthy researches were complete (all the ones I studied dated back to around 1863-1868, so they were curated shortly after The Origin was published (1859)). Perhaps the museum gave him some fine sponge-cake in return. There was at least one male and female adult of each of numerous breeds, many of them still bearing the dried flesh of centuries past. This was great for me, as the patella often gets removed and clucked chucked in the bin with its tendon when museum specimens of birds are prepared (much as elephant “sixth toe” sesamoids are). All of the specimens had their honking huge patellae on display, so that’s what a lot of my photos feature. I do so lament that I did not take a photo of the cake. Did I tell you about that cake? Oh… Check out these examples of Darwin’s chickens:

XXXX breed in right side view, with the patella indicated by a red arrow. It is still attached to the tibiotarsus by the patellar tendon (often misnamed the patellar "ligament", but it is just a continuation of the proximal tendon).

African rooster (wild variety? Darwin’s label was not clear) in right side view, with the patella indicated by a red arrow. That patella is still attached to the tibiotarsus by the patellar tendon (often misnamed the patellar “ligament”, but it is just a continuation of the proximal tendon).

Darwin's handwritten label and the well-endowed patella of the Spanish Cock. What? Oh, you. Stop it.

Darwin’s handwritten label and the well-endowed patella of the Spanish Cock. What? Oh, you. Stop it. That has nothing to do with cake, and only cake-related humour is allowed in this post.

Some other fascinating features exhibited by Darwin’s chickens, which he doubtless mulled over while nibbling on fine cakes, included the following:

The hindlimb of a Polish Silver Laced breed, nicely showing the ossified tendons (red arrow) along the tarsometatarsus. Why these tendons turn into bone is one of the great unsolved mysteries of bone biology/mechanics and avian evolution. Check out the famed feather crest here.

The hindlimb of a Polish Silver Laced breed, nicely showing the ossified tendons (red arrow) along the tarsometatarsus. Why these tendons turn into bone is one of the great unsolved mysteries of bone biology/mechanics and avian evolution.

Check out the famed feather crest of the Silver (Laced) Polish here; it gets so extreme in males that they have a hard time seeing, and can get beaten up by other cockerels when kept in mixed breed flocks.

Here on this blog, and of course on the companion blog “Towards the Chicken of the Future,” domestic chickens and wild junglefowl have often come up, most recently with the Dorking Chicken (another of Darwin’s own specimens that I studied) in the “Mystery Museum Specimen” poetry round of late. Dorkings are HUGE chickens; easily twice the weight of even a broiler chicken, up to 4-5kg. The Dorking-characteristic polydactyly featured in that post is also observed at a relatively high incidence in Silkie and Sultan breeds, I’ve learned. Like this one! (I was so patella-focused, or cake-somnolescent, that I missed it while studying at the museum and only noticed it now while browsing through my photos, bereft of cake)

Nice leg of a Sultan hen. There is an extra toe here as in the Dorking chicken; a duplicate hallux (first toe). This is not, as it might at first seem, a pathological condition as in modern "twisted toe"-suffering domestic chickens.

Nice leg of a Sultan hen. There is an extra toe here as in the Dorking chicken; a duplicate hallux (first toe). This is not, as it might at first seem, a pathological condition as in modern “twisted toe”-suffering domestic chickens.

Malays are another giant breed like the Dorking, but with longer and more muscular legs and longer necks, looking much more like a classic, badass wild junglefowl than a fancy, pampered chicken. But here, undressed to the bare bones, it just looks like a skinny chicken leg, albeit perhaps a bit svelte compared to the Dorking or Sultan.

Hindlimb of a Malay breed of chicken, which Wikipedia nicely tells the story of its misnomer (it may originate from Pakistan, not Malaysia!). Can you find the nice patella? Check out Darwin's lovely label, too.

Hindlimb of a Malay breed of chicken, which Wikipedia nicely tells the story of its misnomer (it may originate from Pakistan, not Malaysia!). Can you find the nice patella? Check out Darwin’s lovely label, too.

You may have come across wild-eyed news stories 5 years ago about “OMG Darwin was sooooooo wrong about chickens!”, referring to his writings on the origin of domestic chickens from Red junglefowl. As Greg Laden adeptly wrote, Darwin (say it with me) didn’t really get it very wrong after all. He did quite well, in fact. Some media outlets did get it more wrong, probably inspired by this press release. Oh well; the science they were reporting about definitely was interesting- modern chickens seem to have some of their yellow skin pigmentation-related genes from Grey junglefowl, although they are still largely descendants of Red junglefowl.

Here, have a JUMBLE-fowl, or rather a junglefowl cockerel, with another Darwin label:

Darwin's example of a wild-type chicken; a Red Junglefowl. As he suspected, these Asian birds were the ancestors of domestic chickens, but today evidence suggests that domestication occurred multiple times in Asia and with different wild varieties of junglefowl bred/mixed in different regions.

Darwin’s example of a wild-type chicken; a Red junglefowl. As he suspected, these Asian birds were the ancestors of domestic chickens, but today evidence indicates that domestication may have occurred multiple times in Asia and with different wild varieties of junglefowl bred/mixed in different regions.

Some breeds aren’t so funky inside, of course, but just have cool feather patterns on the outside, like the “pencilling” (dark streaks on white feathers) evident in pencil breeds; also called triple-laced. Like this fine chap below once would have had, before Darwin tore off his feathers and reduced him to a research-friendly naked skeleton:

A Golden Pencil Hamburgh breed of chicken (cockerel), whose skeleton features the leg and a fine articulated patella.

A Golden Pencil(led) Hamburg breed of chicken (cockerel), whose skeleton features the leg and a fine articulated patella.

Also known as the Holland Fowl, several European countries including the UK claim the Hamsburg as an original breed from their respective realm, and no surprise they do- it’s a lovely spangled chicken. Then, later in the 1800′s the Americans got involved in breeding them, too, and it’s all a big mess. They should get together, have some delectable cakes, and just sort it out.

Scaly, still-greasy foot and hindlimb of what Darwin labelled as the male of a "Game" breed.

Scaly, still-greasy foot and hindlimb of what Darwin labelled as the male of a “Game” breed.

We thus close with another leg of another chicken. Darwin was a bit naughty here, or else terminology of breeds has changed a lot since the 1850′s (very possible), as he just labelled this as a “Game” cockerel. Now, Gamefowl is a big category of breeds. I’m guessing this one was either (1) a Cornish/Indian Game variety or (2) an Old or Modern English Game Fowl. Maybe a person who knows their chicken breeding far better than me (that’s not hard!) will opine differently. The latter varieties were popular in Darwin’s time — the (Muffed) Old English version was mated with other breeds (Malay?) to produce the Modern English form as cockfighting “sports” became banned in 1849 and breeder attentions shifted to the polar opposite of producing showy, fancy birds instead. And thus the bufante, feathered-hair-adorned 1980s pop-rock group was created, to sing about mating or moulting or melting with people or something terribly disgusting and probably having nothing at all to do with chickens,  cake, or cockfighting, or other more seemly pursuits.

So, we have come to the end of my photos of Darwin’s chicken leg bones and such. If you’ve learned something here about chicken breeds, patellae, cake, or Darwin, that’s simply frabjous. Enough of those poncey pigeons, already! I’m crying fo… no, I won’t use that pun. Nevermind. Not even remotely cake-related. Let’s give Darwin’s chickens their just desserts, is the point– and a much better pun, too. Darwin’s chickens are an important part of Darwiniana, and an interesting evolutionary study in and of themselves. I’ve certainly become impressed during my researching for this blog post by the diverse, fascinating biology of chicken breeds. My copy of the “Complete Encyclopedia of Chickens” will be getting some more thorough reading shortly.

Today, however, I am off to return to the NHM-Tring and peruse their other, non-chickeny Galliformes and Anseriformes, with a detour to the mythical hoatzin. But… but… there may be a cake detour involved, too. I shall report back in due course. Off I go!

No, hopefully not that cake.

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Models of a basal dinosaur and bird, showing methods and key differences in body shape.

Our 3D computer models of a basal dinosaur and bird, showing methods and key differences in body shape. The numbers at the bottom are museum specimen numbers.

At about the moment I’m posting this, our Nature paper (our more formal page here, and the actual article here) embargo is ending, drawing a 14+ year gestation to a close. The paper is about how dinosaur 3D body shape changed during their evolution, and how that relates to changes in hindlimb posture from early dinosaurs/archosaurs to birds; “morpho-functional evolution” sums up the topic. We used the 3D whole-body computational modelling that I, Allen and Bates (among others) have developed to estimate evolutionary changes in body dimensions, rather than focusing on single specimens or (as in our last study) tyrannosaur ontogeny. We’ve strongly supported the notion (dating back to Gatesy’s seminal 1990 Paleobiology paper) that the centre of mass of dinosaurs shifted forwards during their evolution, and that this shift gradually led to the more crouched (flexed) hind leg posture that characterizes living birds. Here is a movie from our paper showing how we did the modelling:

And here is a summary of our 17 computer models of archosaur bodies, shown as one walks along the tips of the phylogeny shown in the video (the models are not considered to be ancestral to one another; we used a common computer algorithm called squared-change parsimony to estimate ancestral state changes of body dimensions between the 16 numbered nodes of the tree):

But we’ve done much more than just put numbers on conventional wisdom.

We’ve shown, to our own surprise, that the shift of the centre of mass was largely driven by evolutionary enlargements of the forelimbs (and the head and neck, and hindlimbs, to a less strong degree), not the tail as everyone including ourselves has assumed for almost 25 years. And the timing of this shift occurred inside the theropod dinosaur group that is called Maniraptora (or Maniraptoriformes, a slightly larger group), so the change began in animals that were not flying, but not long before flight evolved (depending on whom you ask, what taxonomy they favour and what evidence one accepts, either the smaller clade Eumaniraptora/Paraves or the bird clade Aves/Avialae).

Now, if you don’t like the cliche “rewriting the textbooks”, do have a look through texts on dinosaur/early avian palaeobiology and you probably will find a discussion of how the tail shortened, the centre of mass moved forwards as a consequence, the caudofemoral musculature diminished, and theropod dinosaurs (including birds) became more crouched as a result. We did that to confirm for ourselves that it’s a pretty well-accepted idea. Our study supports a large proportion of that idea’s reasoning, but modifies the emphasis to be on the forelimbs more than the tail for centre of mass effects, so the story gets more complex. The inference about caudofemoral muscles still seems quite sound, however, as is the general trend of increased limb crouching, but out paper approximates the timing of those changes.

Figure 3 from our paper, showing how the centre of mass moved forwards (up the y-axis) as one moves toward living birds (node 16); the funny dip at the end is an anomaly we discuss in the paper.

Figure 3 from our paper, showing how the centre of mass moved forwards (up the y-axis) as one moves toward living birds (node 16); the funny dip at the end is an anomaly we discuss in the paper.

A final implication of our study is that, because the forelimbs’ size influenced the centre of mass position, and thus influenced the ways the hindlimbs functioned, the forelimbs and hindlimbs are more coupled (via their effects on the centre of mass) than anyone has typically considered. Thus bipedalism and flight in theropods still have some functional coupling– although this is a matter of degree and not black/white, so by no means should we do away with helpful concepts like locomotor modules.

And in addition to doing science that we feel is good, we’ve gone the extra mile and presented all our data (yes, 17 dinosaurs’ worth of 3D whole body graphics!) and the critical software tools needed to replicate our analysis, in the Dryad database (link now working!), which should have now gone live with the paper! It was my first time using that database and it was incredibly easy (about 1 hour of work once we had all the final analysis’s files properly organized)– I strongly recommend others to try it out.

That’s my usual general summary of the paper, but that’s not what this blog article is about. I’ll provide my usual set of links to media coverage of the paper below, too. But the focus here is on the story behind the paper, to put a more personal spin on what it means to me (and my coauthors too). I’ll take a historical approach to explain how the paper evolved.


This paper’s story, with bits from the story of my life:

Embarassing picture of me before I became a scientist. Hardee's fast food restaurant cashier, my first "real job."

Embarassing picture of me before I became a scientist. Hardee’s fast food restaurant cashier, my first “real job”, from ~1999- no, wait, more like 1986. The 1980s-style feathered (and non-receding) hair gives it away!

Rewind to 1995. I started my PhD at Berkeley. I planned to use biomechanical methods and evidence to reconstruct how Tyrannosaurus rex moved, and started by synthesizing evidence on the anatomy and evolution of the hindlimb musculature in the whole archosaur group, with a focus on the lineage leading to Tyrannosaurus and to living birds. As my PhD project evolved, I became more interested and experienced in using 3D computational tools in biomechanics, which was my ultimate aim for T. rex.

In 1999, Don Henderson published his mathematical slicing approach to compute 3D body dimensions in extinct animals, which was a huge leap for the field forward beyond statistical estimates or physical toy models, because it represented dinosaurs-as-dinosaurs (not extrapolated reptiles/mammals/whatever) and gave you much more information than just body mass, with a lot of potential to do sensitivity analysis.

I struggled to upgrade my computer skills over the intervening years. I was developing the idea to reconstruct not only the biomechanics of T. rex, but also the evolutionary changes of biomechanics along the whole archosaur lineage to birds– because with a series of models of different species and a working phylogeny, you could do that. To me this was far more interesting than the morphology or function of any one taxon, BUT required you to be able to assess the latter. So Tyrannosaurus became a “case study” for me in how to reconstruct form and function in extinct animals, because it was interesting in its own right (mainly because of its giant size and bipedalism). (Much later, in 2007, I finally finished a collaboration to develop our own software package to do this 3D modelling, with Victor Ng-Thow-Hing and F. Clay Anderson at Honda and Stanford)

Me and a Mystery Scientist (then an undergrad; now a successful palaeontologist), measuring up a successful Cretaceous hypercarnivore at the UCMP; from my PhD days at Berkeley, ~2000 or so.

Me and a Mystery Scientist (then an undergrad; now a very successful palaeontologist!), measuring up a successful Cretaceous hypercarnivore at the UCMP; from my PhD days at Berkeley, ~2000 or so.

In all this research, I was inspired by not only my thesis committee and others at Berkeley, but also to a HUGE degree by Steve Gatesy, a very influential mentor and role model at Brown University. I owe a lot to him, and in a sense this paper is an homage to his trailblazing research; particularly his 1990 Paleobiology paper.

In 2001, I got the NSF bioinformatics postdoc I badly wanted, to go to the Neuromuscular Biomechanics lab at Stanford and learn the very latest 3D computational methods in biomechanics from Prof. Scott Delp’s team. This was a pivotal moment in my career; I became partly-an-engineer from that experience, and published some papers that I still look back fondly upon. Those papers, and many since (focused on validating and testing the accuracy/reliability of computer models of dinosaurs), set the stage for the present paper, which is one of the ones I’ve dreamed to do since the 1990s. So you may understand my excitement here…

Stanford's Neuromuscular Biomechanics Lab, just before I left in 2003.

Stanford’s Neuromuscular Biomechanics Lab, just before I left in 2003.

But the new paper is a team effort, and was driven by a very talented and fun then-PhD-student, now postdoc, Dr Vivian Allen. Viv’s PhD (2005-2009ish) was essentially intended to do all the things in biomechanics/evolution that I had run out of time/expertise to do in my PhD and postdoc, in regards to the evolution of dinosaur (especially theropod) locomotor biomechanics. And as I’d hoped, Viv put his own unique spin on the project, proving himself far better than me at writing software code and working with 3D graphics and biomechanical models. He’s now everything that I had hoped I’d become by the end of my postdoc, but didn’t really achieve, and more than that, too. So huge credit goes to Viv for this paper; it would never have happened without him.

We also got Karl Bates, another proven biomechanics/modelling expert, to contribute diverse ideas and data. Furthermore, Zhiheng Li (now at UT-Austin doing a PhD with Dr Julia Clarke) brought some awesome fossil birds (Pengornis and Yixianornis) from the IVPP in Beijing in order to microCT scan them in Londo. Zhiheng thus earned coauthorship on the paper — and I give big thanks to the Royal Society for funding this as an International Joint Project, with Dr Zhonghe Zhou at the IVPP.

That’s the team and the background, and I’ve already given you the punchlines for the paper; these are the primitive and the derived states of the paper. The rest of this post is about what happened behind the scenes. No huge drama or anything, but hard, cautious work and perseverance.

Me shortly after I moved to the RVC; video still frame from a dinosaur exhibit I was featured in. Embarassingly goofy pic, but I like the blurb at the bottom. It's all about the evolutionary polarity, baby!

Me shortly after I moved to the RVC; video still frame from a dinosaur exhibit (c. 2004) I was featured in. Embarassingly goofy pic, but I like the blurb at the bottom. It’s all about the evolutionary polarity, baby!

The paper of course got started during Viv’s PhD thesis; it was one of his chapters. However, back then it was just a focus on how the centre of mass changed, and the results for those simple patterns weren’t very different from those we present in the paper. We did spot, as our Nature supplementary information notes,  a strange trend in early theropods (like Dilophosaurus; to a lesser degree Coelophysis too) related to some unusual traits (e.g. a long torso) and suggested that there was a forward shift of centre of mass in these animals, but that wasn’t strongly upheld as we began to write the Nature paper.

On the urging of the PhD exam committee (and later the paper reviewers, too), Viv looked at the contributions of segment (i.e. head, neck, trunk, limbs, tail) mass and centre of mass to the overall whole body centre of mass. And I’m glad he did, since that uncovered the trend we did not expect to find: that the forelimb masses were far more important for moving the centre of mass forwards than the mass (or centre of mass) of the tail was– in other words, the statistical correlation of forelimb mass and centre of mass was strong, whereas changes of tail size didn’t correlate with the centre of mass nearly as much. We scrutinized those results quite carefully, even finding a very annoying bug in the 3D graphics files that required a major re-analysis during peer review (delaying the paper by ~6 months).

The paper was submitted to Nature first, passing a presubmission inquiry to check if the editor felt it fit the journal well enough. We had 3 anonymous peer reviewers; 1 gave extensive, detailed comments in the 3 rounds of review and was very fair and constructive, 1 gave helpful comments on writing style and other aspects of presentation as well as elements of the science, and 1 wasn’t that impressed by the paper’s novelty but wanted lots more species added, to investigate changes within different lineages of maniraptorans (e.g. therizinosaurs, oviraptorosaurs). That third reviewer only reviewed the paper for the first round (AFAIK), so I guess we won them over or else the editor overruled their concerns. We argued that 17 taxa were probably good enough to get the general evolutionary trends that we were after, and that number was ~16 more species than any prior studies had really done.

Above: CT scan reconstruction of the early extinct bird Yixianornis in slab conformation, and then Below: 3D skeletal reconstruction by Julia Molnar, missing just the final head (I find this very funny; Daffy Duck-esque) which we scaled to the fossil’s dimensions from the better data in our Archaeopteryx images. Yixianornis reconstruction There is also the concern, which the reviewers didn’t focus on but I could see other colleagues worrying about, that some of the specimens we used were either composites, sculpted, or otherwise not based on 100% complete, perfectly intact specimens. The latter are hard to come by for a diversity of extinct animals, especially in the maniraptoran/early bird group. We discussed some of these problems in our 3D Tyrannosaurus paper. The early dinosauromorph Marasuchus that we used was a cast/sculpted NHMUK specimen based on original material, as was our Coelophysis, Microraptor and Archaeopteryx; and our Carnegie ??Caenagnathus?? specimen was based more on measurements from 1 specimen than from direct scans, and there were a few other issues with our other specimens, all detailed in our paper’s Supplementary Information.

But our intuition, based on a lot of time spent with these models and the analysis of their data, is that these anatomical imperfections matter far, far less than the statistical methods that we employed– because we add a lot of flesh (like real animals have!) outside of the skeleton in our method, the precise morphology of the skeleton doesn’t matter much. It’s not like you need the kind of quality of anatomical detail that you need to do systematic analyses or osteological descriptive papers. The broad dimensions can matter, but those tend to be covered by the (overly, we suspect) broad error bars that our study had (see graph above). Hence while anyone could quibble ad infinitum about the accuracy of our skeletal data, I doubt it’s that bad– and it’s still a huge leap beyond previous studies, which did not present quantitative data, did not do comparative studies of multiple species, or did not construct models based on actual 3D skeletons as opposed to artists’ 2D shrinkwrapped reconstructions (the “Greg Paul method”). We also did directly measure the bodies of two extant archosaurs in our paper: a freshwater crocodile and a junglefowl (CT scan of the latter is reconstructed below in 3D).

One thing we still need to do, in future studies, is to look more carefully inside of the bird clade (Aves/Avialae) to see what’s going on there, especially as one moves closer to the crown group (modern birds). We represented modern birds with simply 1 bird: the “wild-type chicken” Red junglefowl, which isn’t drastically different in body shape from other basal modern birds such as a tinamou. Our paper was not about how diversity of body shape and centre of mass evolved within modern birds. But inspecting trends within Palaeognathae would be super interesting, because a lot of locomotor, size and body shape changes evolved therein; ostriches are probably a very, very poor proxy for the size and shape of the most recent common ancestor of all extant birds, for example, even though they seem to be fairly basal within that whole lineage. And, naturally, our study opens up opportunities for anyone to add feathers to our models and investigate aerodynamics, or to apply our methods to other dinosaur/vertebrate/metazoan groups. If the funding gods are kind to us, later this year we will be looking more closely, in particular, at the base of Archosauria and what was happening to locomotor mechanics in Triassic archosaurs…

Clickum to embiggum:

Australian freshwater crocodile, Crocodylus johnstoni; we CT scanned it in 3 pieces.

Australian freshwater crocodile, Crocodylus johnstoni; we CT scanned it in 3 pieces while visiting the Witmer lab in Ohio.

A Red junglefowl cockerel, spotted in Lampang, Thailand during one of my elephant gait research excursions there. Svelte, muscular and fast as hell.

A Red junglefowl cockerel, spotted in Lampang, Thailand during one of my elephant gait research excursions there. Svelte, muscular and fast as hell. This photo is here to remind me to TAKE BLOODY PICTURES OF MY ACTUAL RESEARCH SPECIMENS SO I CAN SHOW THEM!

I’d bore you with the statistical intricacies of the paper, but that’s not very fun and it’s not the style of this blog, which is not called “What’s in John’s Software Code?”. Viv really worked his butt off to get the stats right, and we did many rounds of revisions and checking together, in addition to consultations with statistics experts. So I feel we did a good job. See the paper if that kind of thing floats your boat. Someone could find a flaw or alternative method, and if that changed our major conclusions that would be a bummer– but that’s science. We took the plunge and put all of our data online, as noted above, so anyone can do that, and that optimizes the reproducibility of science.

What I hope people do, in particular, is to use the 3D graphics of our paper’s 17 specimen-based archosaur bodies for other things– new and original research, video games, animations, whatever. It has been very satisfying to finally, from fairly early in the paper-writing process onwards, present all of the complex data in an analysis like this so someone else can use it. My past modelling papers have not done this, but I aim to backtrack and bring them up to snuff like this. We couldn’t publish open access in Nature, but we achieved reasonably open data at least, and to me that’s as important. I am really excited at a personal level, and intrigued from a professional standpoint, to see how our data and tools get used. We’ll be posting refinements of our (Matlab software-based) tools, which we’re still finding ways to enhance, as we proceed with future research.

Velociraptor-model-min Dilophosaurus-model-min00

Above: Two of the 17 archosaur 3D models (the skinny “mininal” models; shrinkwrapped for your protection) that you can download and examine and do stuff with! Dilophosaurus on the left; Velociraptor on the right. Maybe you can use these to make a Jurassic Park 4 film that is better, or at least more scientifically accurate, than Hollywood’s version! ;-) Just download free software like Meshlab, drop the OBJ files in and go!

Now, to bring the story full circle, the paper is out at last! A 4 year journey from Viv’s PhD thesis to the journal, and for me a ~14 year journey from my mind’s eye to realization. Phew! The real fun begins now, as we see how the paper is received! I hope you like it, and if you work in this area I hope you like the big dataset that comes with it, too. Perhaps more than any other paper I’ve written, because of the long voyage this paper has taken, it has a special place in my heart. I’m proud of it and the work our team did together to produce it. Now it is also yours. And all 3200ish words of this lengthy blog post are, as well!

Last but not least, enjoy the wonderful digital painting that Luis Rey did for this paper (another of my team’s many failed attempts to get on the cover of a journal!); he has now blogged about it, too!

Dinosaur posture and body shape evolving up the evolutionary tree, with example taxa depicted.

Dinosaur posture and body shape evolving up the evolutionary tree, with example taxa depicted. By Luis Rey.


News stories about this paper will be added below as they come out, featuring our favourites:

1) NERC’s Planet Earth, by Harriet Jarlett: “Dinosaur body shape changed the way birds stand

2) Ed Yong on Phenomena: “Crouching  bird, hidden dinosaur

3) Charles Choi on Live Science: “Crouching bird, hidden evolutionary purpose?

4) Brian Handwerk on Nat Geo Daily News: “Birds’ “Crouching” Gait Born in Dinosaur Ancestors

5) Jennifer Viegas on Discovery News: “Heavier dino arms led evolution to birds

6) Puneet Kollipara on Science News: “Birds may have had to crouch before they could fly

And some superb videos- we’re really happy with these:

1) Nature’s “Crouching Turkey, Hidden Dragon

2) Reuters TV’s “3D study shows forelimb enlargement key to evolution of dinosaurs into birds

Synopsis: Decent coverage, but negligible coverage in the general press; just science-specialist media, more or less. I think the story was judged to be too complex/esoteric for the general public. You’d think dinosaurs, evolution, computers plus physics would be an “easy sell” but it was not, and I don’t think we made any big errors “selling” it. Interesting– I continue to learn more about how unpredictable the media can be.

Regardless, the paper has had a great response from scientist colleagues/science afficionados, which was the target audience anyway. I’m very pleased with it, too– it’s one of my team’s best papers in my ~18 year career.

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frontcover

The Unfeathered Bird book by Katrina van Grouw proclaims immediately in its Introduction that it “is not an anatomy of birds.”  True– it is far more than that, and it would be a shame if it had just been a dry, technical avian osteology reference book. It is a unique blend of art and science- particularly avian anatomy, evolution, taxonomy, natural history and more. The Unfeathered Bird is written for a general audience; birders/twitchers or just natural history buffs would be ideal targets of its unfettered passion for all things avian. A 12-year-old who is very keen on animals could enjoy it, and it may ignite the flames of ornithological excitement in many young or older readers. I am glad it was not called “The Naked Bird” as that would have caused some serious misconceptions (badum-tish!). The book is dripping with illustrations (at least one every two pages, often more). Almost all of the illustrations (except some paintings in the style of the cover) are in the same brownish sketch style that, like much of the book, evokes a bygone era of dark wooden cabinets and shadowed halls packed with skeletons, with nary an interactive graphics display, animatronic dinosaur or hyperdetailed cladogram in sight. It feels like an homage to the Victorian naturalists’ joy for anatomical detail conveyed through painstakingly detailed woodcuts. And while many still think of feathers as “the defining feature of birds,” enough about feathers already. Seriously. This is a book is about what lies beneath, and how all that non-fluffy stuff is important for birds’ lives, too.

(image-intense post; all can be clicked to embiggritate)

Katrina with peacock feather headdress? (back cover pic and rear view of same skeleton)

Katrina with peacock feather headdress? (back cover pic and rear view of same skeleton)

Katrina with front cover framed pic and the peacock skeleton that went with it.

Katrina with front cover framed pic and the peacock skeleton that went with it.

The Introduction continues to explain that the book is truly about how the external anatomy of birds is linked to the bony anatomy, which might remind astute readers of modern approaches like the extant phylogenetic bracket. The rest of the book uses both skeletal and unfeathered, quasi-myological illustrations to get this point across vividly. The explanatory text is written at a basic enough level for the average reader and is just the right length, with interesting anecdotes and natural history facts that even the expert reader will find interesting or even inspirational (e.g. possibly a goldmine for research ideas). First there is a 26 page “Basic” section with an introduction to avian osteology, with bountiful sketches to illustrate key organs and text explaining how it all fits together in the fully accoutered bird. The decision to use classical Linnean taxonomy (defunct or re-arranged taxa from the Systema Naturae like Accipitres, Picae, Anseres, Grallae, Gallinae and Passeres; which are the six “Specific” chapters in the second section of the book) was a good one- it enhances the classical feel of the tome and gives the author a great opportunity to discuss convergent evolution and how that misled past ornithologists.

But for me, the book is most pleasurable for the visualizations and the passion for all things birdy that weaves through them and the accompanying text. The removal of feathers, or even all soft tissues, from bird bodies (posed in naturalistic behaviours) that van Grouw renders in her illustrations shows birds in a new light, emphasizing the strangeness and diversity that lie beneath. The author begins the book with a touching Acknowledgments section in which her husband Hein van Grouw, curator of birds at the Natural History Museum’s Tring collection, features very prominently, making it clear that the book was a team operation and comes from the heart after a 25-year journey. This gives the book a special warmth that is preserved throughout the remainder- although the illustrations are of flayed bodies or boiled / beetle-macerated skeletons, the tone is nothing less than an earnest love for birds of all kinds, and a zest for portraying those feelings to the reader in sketches and prose. It is a joyous celebration, not a somber litany, of the wonder of birds that can be gleaned from dead bodies. There is so much powerful, awesome imagery stuffed into those pages that it is hard to summarize. I’ll let five of my favourite images from the book (more are in her gallery and her book’s Facebook page; but even these are just the tip of the icebird) help get this across (used with permission of the author):

Naked kiwi in action.

Naked kiwi in action.

The unscaled bird: guineafowl feet.

The unscaled bird: guineafowl feet.

Deplumed sparrowhawk with dove trophy, exalting in its triumph.

Deplumed sparrowhawk with dove trophy, exalting in its triumph.

Budgerigar has made a friend? Or came to grips with its own mortality?

Budgerigar has made a friend? Or came to grips with its own mortality?

Trumpet Manucode WTF anatomy! Spiraling tracheal coil made me gasp in awe when I saw this image in the book.

Trumpet Manucode’s WTF anatomy! Spiraling tracheal coil made me gasp in awe when I saw this image in the book.

Now I’ll depart from this post just being a book review. I went to the Tring collection to do some research, and arranged my trip so I’d also get to see the debut of a Tring special exhibit featuring The Unfeathered Bird, and also to meet Katrina as well as Hein van Grouw. The placement of the exhibit at Tring is apropos, because Katrina was a curator at the museum until a few years ago and Hein still is. But the inspiration for the work and the specimens used (with a few exceptions, including from other museums) are Katrina’s. She (with Hein’s help) procured bodies of birds to dissect, macerate and sketch for the book over its 25 year fledging period, noting in the Acknowledgments that “no birds were harmed” to do this– do read those acknowledgments, as there are some amusing tales there of how she obtained some specimens.

I was fortunate to be able to take some photos of the exhibit while they set it up, and grabbed some candid images of Katrina and colleagues during that process. The following images show off the exhibit, which is all in one clean, bright, simply adorned room in the Tring that lets Katrina’s framed sketches be the focus. Here are some examples:

Poster advert for the book in the Tring collections.

Poster advert for the book in the Tring collections.

Tring exhibit setup, with Katrina, husband Hein, and helper finishing it up.

Tring exhibit setup, with Katrina, husband Hein, and helper finishing it up.

Tring exhibit now ready.

Tring exhibit now ready.

Tring exhibit case.

Tring exhibit case.

Framed sketches at Tring exhibit.

Framed sketches at Tring exhibit.

Framed sketches at Tring exhibit.

More framed sketches at Tring exhibit.

The exhibit is fun for people who are already Unfeathered Bird fans, and a good way of drawing in new ones. The book is a precious thing that any fan of birds, especially scientists, really needs to have a hard copy of. While it claims not to be an anatomy text, its illustrations provide ample opportunities to use it for that purpose. But really the point of owning all 287-plus pages is to bask in the warmth of true, pure appreciation for classic ornithology, which I found infectious. It is a book by and for bird lovers, but also for those that find the interface of art and science to be fascinating.

I confess I used to hate birds. I found them annoying and boring; all that flitting and twitting and pretentious feathers. “Get over yourselves, already, and calm down too!” was my reaction to them. When I started grad school, I had an open disdain for birds, even moreso than for mammals (OK, except cats). I was a “herp” fan through and through, for most of my life (childhood spent catching anoles in Florida, or stalking frogs in Ohio; during visits to my grandparents). What won me over was studying birds (and eventually mammals, too) as a young scientist, and learning how incredible they are– not just as endpoints in the story of theropod dinosaur evolution, as my thesis focused on, but as amazing animals with spectacular form-function relationships.  The Unfeathered Bird is saturated with that amazement, so we’re birds of an unfeather.

Framed sketch of dodo head at Tring exhibit.

Framed sketch of dodo head at Tring exhibit.

Entirely unfeathered Indian peafowl in matching views.

Entirely unfeathered Indian peafowl in matching views.

Painted Stork and Toco Toucan sketches.

Painted Stork and Great Hornbill sketches.

Red junglefowl, wild ancestor of domestic chickens (and the book ends with several such breeds illustrated),

Red junglefowl, wild ancestor of domestic chickens (and the book ends with several such breeds illustrated).

Katrina told me that she is already deep into writing the next book, whose subject I won’t spoil for you here but maybe we will be lucky enough to have her appear in the Comments and plug it? :) (Her website does say “It was Hein’s stroke of genius to include domestic birds and they’ve provided the inspiration for my next project.” so the cat is out of the bag and amongst the pigeons!) It is great to hear that the book has done quite well sales-wise and critically, such as ~#67 on the Amazon sales list at one point– I hope this paves the way for more such books not only from Katrina, but from others engaged in lateral thinking (and still others) on the boundaries of science-art.

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…a daily picture of anatomy! And today it is three pictures, scoob-a-dee!

Welcome back again to Freezermas! 

For the previous days of Freezermas we first had 1 picture, then 2, now guess how many we have today? Right, we’ve settled into a groove and have three (plus one silly one). Today is fresh beefy anatomy day! No focus on bones, but on soft tissues– however, once again, I’m representin’ bird legs! And this time, no mystery things to identify; sorry. But if you want to muscle in on some myology, today is the day for you. I will unwrap the thigh of an ostrich and consider the major muscles that power rapid running in this biped, and how they illuminate the evolution of bipedal motion along the line of descent to birds. For more ostrich escapades, see this old post. And we’re off!

Stomach-Churning Rating: 7/10; plenty of fresh, red, meaty meat from ostrich leg muscles.

Ostrich thigh muscles 1

Here you are looking at a right hindlimb of an ostrich, in side/lateral view. To help orient yourself, the hip lies deep in the middle of the image and the knee is the rounded bump near the bottom right corner, with the shank angling sharply back toward the bottom left.

I’ve labelled six muscles in yellow. As usual for sauropsid (bird/reptile) pelvic limb muscles, they have sensible names that reflect their attachments. They don’t have so many silly old mammalian names like pectineus or latissimus, which tell you rather little about the muscles themselves. We can thank 19th century anatomists like two of my anatomist heroes, Hans Gadow and Alfred Romer (who refined Gadow’s earlier work and made it more popular among English-speakers and palaeontologists), for that enlightened nomenclature.

The six muscles seen above are the IC (iliotibialis cranialis), IL (iliotibialis lateralis), “AMB2?” (one of the ambiens muscles– correctly identified; ignore the ?), ITC (iliotrochantericus caudalis), CFP (caudofemoralis pars pelvica) and FCLP (a mouthful to say: flexor cruris lateralis pars pelvica). The ambiens is the one oddly, non-anatomically named muscle, and has nothing to do with helping you sleep (pssst– wake up! Muscles are exciting!), but everything to do with the state of total awesomeness, which is what “ambiens” means. Maybe. Or I am making shit up.

Amazed ostrich

The IC, IL and AMB2 are parts of the triceps femoris group (discussed in my 1st Freeezermas post), or for mammal fans the quadriceps. The IC and AMB are in front of the hip so they flex it (move the thigh forward; protract it); the IL is right around the hip so it can flex or extend the hip (protract/retract the femur); all three of these can extend (straighten) the knee joint to varying degrees. The IC is fairly typical for a bird except for its size, and helps to quickly swing the leg through the air between steps. Some birds have multiple parts of the IL, but ostriches and many others have simplified it to one major mass; regardless, it is a major muscle used to support the weight of the body.

The AMB2 is a remarkable muscle unique to ostriches; it can also be called the dorsal ambiens muscle. Typical birds just have a single head of the AMB sitting on the preacetabular (pubic) tubercle, so in front of and below the hip. It has a crazy tendon that snakes past the knee (in some birds, perforating/grooving the patella) into the lower leg muscles and may be able to even pull on the toes. But ostriches, for some reason, added a second head of this muscle that was shifted way up onto the front of the pelvis (the ilium; dorsal bladelike bone). Crocodilians also have a 2nd ambiens muscle but in a different position, and almost certainly as an example of convergent evolution. The function of the ambiens is mysterious, but this muscle has featured prominently in avian systematics/taxonomy, evolution (invoked as a key muscle used in perching) and more.

These muscles of the triceps femoris group are easily identifiable in crocodiles and other reptiles because they are remarkably similar in their attachments. The main changes these muscles experienced during the evolution of bipedalism, dinosaurs and later birds are simply proportional– they got bigger, with stronger, larger attachments on the pelvis and the front of the knee (the CC/LC, if you remember from Freezermas day 1).

The ITC is a muscle that is very dear to me. I’ve written a lot about it, and I love saying the name “Iliotrochantericus caudalis”- it is musical to me. For mammal fans, think gluteal muscles (medial gluteal in particular). It is a huge, pennate muscle (short and strongly angled muscle fibres in a “sandwich” with a tendinous sheet between the two layers of fibres). It has a short, broad tendon that wraps around the trochanteric crest (a structure on the upper front end of the femur with a history that goes wayyyy back into dinosaurs; long story!) to insert in a scarred depression. The ITC seems to mainly rotate the femur around its long axis to help support the body. I could go on and on about this muscle, which is part of the enigmatic “deep dorsal” thigh muscle group — the homologies of this group among land vertebrates are still controversial and confusing. But I will spare you the on-and-on. Incidentally, the ITC  is the “oyster” in birds that is the best cut of meat. And in ostriches it makes a massive steak.

The CFP also has a cool evolutionary history. It runs from the back of the pelvis to the middle of the femur, closely adjoined to the caudal head of the muscle (CFC), which is more vestigial. In birds the CFP is usually not a large muscle, but in other sauropsids/reptiles it can be fairly hefty, although almost never as hefty as its more famous counterpart the caudofemoralis longus (= CFC in birds). Probably any dinosaur specialist is familiar with its origin and its insertion: respectively, the “brevis fossa” on the back of the ilium; a big shelf of bone; and the fourth trochanter of the femur; a crest of bone that is reduced to a scar/tubercle in birds. Much like its tail-based counterpart, the CFP became progressively reduced closer and closer to birds. This is related to a reduction in the amount of movement of the femur/thigh during locomotion, as birds shortened their tails and shifted their balance forward, as Steve Gatesy showed in a classic 1990 paper. Hopefully there will be more about this subject in a future paper from my team…

The FCLP is another muscle that didn’t change much, except by getting larger as we trace its evolution from early reptiles to birds. It is a “hamstring” muscle that is an important power source during locomotion in birds like the ostrich, because it retracts the lower limb (flexes the knee; hence flexor cruris in its name) as well as the femur/thigh (extends the hip). Your semitendinosus muscle is a good comparison to it. Indeed, these two differently named muscles are homologous– our very distant tetrapod ancestor had the same single muscle, and its descendants didn’t change it that much on our lineage or on the avian/reptile one.

Ostrich thigh muscles 3

I’ve reflected the IL muscle out of the way so we can see the second layer of muscles underneath it. Now we see two more muscles of the thigh, and large ones at that– the FMTL (femorotibialis lateralis) and ILFB (iliofibularis).

The FMTL simply is a part of the triceps femoris group that only comes from the femur and hence only, but due to its large size powerfully, straightens the knee. Unlike the other muscles in this group, it has no action about the hip joint. It is very similar to your vastus lateralis muscle: its fleshy origin dominates the surface of the femur (thigh bone). There are two other parts of that muscle, hidden in this figure, much like our vastus group has multiple parts. Again, this is a muscle that enlarged on the lineage leading to modern birds.

And that evolutionary enlargement applies, too, to the ILFB, whose prominent insertion I discussed on day 1 of Freezermas. This huge “biceps” muscle (it is single-headed unlike in humans, so the name “biceps” does not apply well) is the most powerful of the “hamstring”-type muscles that extend the hip and flex the knee. Therefore it is important for the “knee-driven” locomotion of birds. And hence the ILFB enlarged during avian evolution– which is very evident from changes of both its bony origin on the back of the pelvis/ilium and its insertion on the fibula.

Ostrich thigh muscles 2

Here, for the terminus of today’s trio of struthious tributes and tribulations, I’ve moved the ILFB  out of the way so you can see the various inner/medial layer of thigh muscles. Some of the former muscles are more exposed now, and we can see three new ones: the FCM (flexor cruris medialis), PIFM+(PIF)L (the tongue-twisting puboischiofemoralis medialis et lateralis), and tiny ISF (ischiofemoralis).

The FCM (~mammalian semitendinosus) is merely another, smaller part of the FCLP’s “hamstring” group, and its thin tendon blends with that of the FCLP, so it very much works with that muscle in locomotion, and has a similar evolutionary history.

The PIFM+L are “adductors”, but in birds they don’t really do any adduction (drawing the legs inwards) because they are right behind, rather than below or inside, the hip. They act as hip extensors/retractors of the femur, and probably aid more in holding the femur steady (“postural muscles”) than playing a major role in producing power for locomotion like the ILFB/hamstring group does. In earlier reptiles, they were much more important, for preventing the legs from splaying too far away from the body.

The ISF is usually quite a large muscle in birds, but ostriches and some other ratites have reduced it to a thin slip of muscle– often mistaken for other muscles (indeed, like a few other muscles I’ve described here, modern anatomists still get confused by this muscle– an otherwise superb recent description by Gangl et al., among others, mis-identifies this and some other muscles— an error an upcoming paper from my group will rectify). Normally the ISF sits atop a bone-free window on the outer surface of the pelvis, the ilio-ischiadic fenestra (literally a window in Latin) in birds; in ostriches it has moved more onto the ischium. In contrast, in other sauropsids it lies inside the pelvis, so during its evolution it became more lateral, but the insertion on the upper femur was maintained. It is a weak rotator and extensor of the hip, especially in ostriches in which its role is probably proportionately puny.

And there you have read a healthy chunk of my 2001 PhD thesis, condensed into less jargonious language. You might now know almost half of the key muscles of the avian hind limb. If you made it this far, you are one awesome anatomical enthusiast. If you eat meat, apply this lesson to the next chicken thigh you consume, to consumate this enthusiasm.

A broader point I’d like to make here is that anatomy is best conveyed not only along with the functional narrative (How does anatomy work?) but also the evolutionary tale (Where did anatomy come from and What were the consequences of its changes? Why did it change?). This takes it away from dry memorization of terms and locations, and carries it into the realm of explaining why nature is the way it is, and how every organism’s biology has a richly detailed and complex background. This style portrays nature as much more like that tangled bank that Darwin so enchantingly envisioned. I’ve tried to do that justice here, using this one ostrich whom we affectionately called Twinkletoes, or Twinkie, when we dissected it back in 2002.

Happy Freezermas! Sing it: “On the third day of Freezermas, this blo-og gave to me: one tibiotarsus, two silly pictures, a-and three muscle layers from Twinkie!”

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…a daily picture of anatomy!

Welcome to Freezermas! In the dead of winter, the WIJF blog jumps down your internet to deliver mind-warming science, and images, and evolution! To celebrate Charles Darwin’s birthday (204th = tomorrow Feb 12, 2013), I’m bringing you one Anatomy Vignette each day this week (we’ll see if I can manage the weekend or not)! Let’s do this!

Stomach-Churning Rating: 2/10; just bones; one picture of them, and then a lot of discussion of muscle anatomy but no pictures of it.

Hutch02-Fig4

The above image comes from one of my old, somewhat obscure anatomy papers (link to pdf here), from 2003. It’s possibly the first figure I made, entirely by myself, that I’m sort of proud of. It doesn’t totally suck compared with some of my other attempts. I did the stippled line drawing on the left, and on the right is one of my first usages of a digital photo in a paper (digital cameras were finally up to the task around that time; I used my new Nikon Coolpix 900, if memory serves). It was a greatly improved figure over what I’d submitted for this paper originally, which was a rushed, half-baked manuscript for a SICB conference symposium on tendons. I’ll never forget one of the peer reviews of the manuscript, which said something like “the text of this paper is a joy to behold, but the figures are a horror.” They were right, and luckily the images in the paper I submitted changed a lot in revision. (I’m still embarrassed by the incident, though!)

Anyway, the picture is of  the lower hind limb of two theropod dinosaurs: (a,c) an adult Tyrannosaurus rex, and (b,d) a wild turkey (Meleagris) from my personal collections of dissected-then-skeletonized animals (this turkey became a biomechanical model in a 2004 paper of mine, too!).  In both cases we’re looking at a right hind limb; in (a) and (b) from a caudal/posterior/rear view, and in (c) and (d) from a lateral/side-on/profile view.

If you’re having trouble visualizing these bones in the real animal, check this T. rex skeleton in rear and side views and try to find these bones. You can do it! You might also want to look back at my paroxysmic outburst of love for knee joint anatomy.

The thicker long bone is the tibia (your main shank bone; or in a lamb shank, chicken drumstick, etc); the thinner outer bone is the fibula. Together with some smaller bones, for brevity we can call them the tibiotarsus – but only in theropod dinosaurs, or you will anger the freezer gods.

The labels show some cool anatomical features, as follows:

CC” the cranial cnemial crest of the tibia (a projection of bone unique to the knees of birds);

CF” the crista fibularis; or fibular crest; of the tibia (more about this below);

FT” the fibular tubercle (insertion of the big hamstring/biceps muscle M. iliofibularis);

LC” the lateral cnemial crest of the tibia (a big arching swath of bone that both birds and non-avian theropods like Tyrannosaurus have; the CC is just pasted on top of this in birds); and

MF” which denotes a muscle fossa (depression) on the inner surface of the upper end of the fibula, which presumably housed a muscle (M. popliteus) binding the fibula to the tibia in earlier dinosaurs, but is vestigial in birds.

The CF, or fibular crest, is a feature that only theropod dinosaurs, among reptiles, develop like this. It evolved early in their history and thus was passed on to birds with other ancient features like hollow bones and bipedalism. It binds the fibula closely appressed to the tibia, making those bones act more like a single functional unit –and sometimes they even fuse together. The CF also transmits forces from the whopping big M. iliofibularis muscle’s insertion (the FT label) across the puny fibula onto the robust tibia. The MF once held a muscle that also helped keep those two bones together, but additionally it could have contracted to move them relative to each other a little bit, as in other living animals (many mammals and reptiles have a big M. popliteus and/or M. interosse[o]us). So these features all have a common functional, anatomical and evolutionary (and developmental; different story for evo-devo fans) relationship. By binding the fibula and tibia together, these structures helped early bipeds (the first theropods and kin) support themselves on one leg at a time during standing and moving, and also helped begin to reduce the limbs to lighten them for easier, faster swinging. So we can think of these features as specializations that helped theropod dinosaurs, and ultimately birds, get established as bipedal animals.

The CC and LC have a similar story to tell; for one, they are muscle attachments, again mainly for thigh muscles. And again, the LC dates back to early theropods (and some other dinosaurs had a version of it; usually smaller). These crests serve mainly as insertions for the “quadriceps” (in human/mammal terms) or triceps (in reptile/bird terms) muscle group’s major tendon, spanning from the pelvis/femur across the thigh and knee to this region. In birds, we call this structure of insertion the patellar tendon or (less appropriately) ligament. But dinosaurs had no patella, ever, so the triceps femoris tendon would be the proper technical term. Regardless, that crest (LC, and later LC too) helped the attached muscles to straighten the knee joint or support body weight during standing/moving, by giving them better leverage. So it would have been important for early bipeds, too, like the CF, MF and other features above. Your cnemial crest (tibial tuberosity) is pathetic by comparison. Don’t even look at it. Droop your knees in primate shame!

Bumps and squiggles on bones might seem puny details just for anatomists to study and describe in long, tedious monographs, but each is part of the great story of evolution, and each has a story to tell that fits into that story. Back in Darwin’s day, some of the world’s greatest scientists of the age (Richard Owen and Thomas Huxley being but two spectacular examples) pored over these seemingly innocuous features, and so they became part of nascent evolutionary theory even then. This week, I’ll be celebrating a lot of those details, which I still feel are important today, and the stories they help to tell.

Happy Freezermas! Sing it: “On the first day of Freezermas, this blo-og gave to me: a tibiotarsus with a CF and FT!”

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Hey, Americans and others happening to be gobbling down Meleagris gallopavo today– don’t forget to practice your anatomy! Such a great opportunity. Dig in to that carcass and horrify/amaze your family and friends! This pic might help you get started (info below if you want it), and is my WIJF blog wish of happiness to you all, today.

Stomach-Churning Rating: 6 out of 10; a small picture of some fresh turkey leg muscles, but not that bad really.

Click to embiggen.

Wondering what’s shown here?

On the left: an ossified (turned into bone!) tendon, probably part of the M. flexor perforans et perforatus group (a wickedly complex set of muscles that go from the knee region to the toes, and act mainly to flex the knee, extend the ankle and (plantar)flex the toes; i.e curl the toes up). What’s particularly cool is that, towards the top, you can see the divisions where the pennate (angled) fibers of the short, meaty muscle belly sat. If you are eating a turkey drumstick, you will be picking some of these out of the meat, although many turkeys seem to have fewer bony tendons due to human breeding and young age at slaughter.

In the middle, top: a crude experiment where we hung a frozen turkey’s body in a few different orientations to determine its centre of mass, important for biomechanical calculations. Mad science, but simple science.

In the middle, bottom: the right hip joint of a turkey in lateral (side) view, showing a few of the key muscles of the thigh. The ITC is M. (abbreviated Latin for Musculus) iliotrochantericus caudalis. Practice saying that (ill-ee-oh-tro-kan-tare-ick-us caw-dahl-iss) to impress your friends. It sits in a depression in the ilium (top pelvic bone), in front of the hip joint. The ITC is also important for helping birds to support their weight, as Steve Gatesy and I discussed in our 2000 Paleobiology paper. The ITC leaves a lovely crescent-shaped scar on the top of the femur (thigh bone). Show off your culinary skills by noting to your dinner party that this muscle is the best bit of the bird, AKA the “oyster”. (A little tip is here for how to find it; in a chicken but the anatomy is almost the same in a turkey)

The OM is the obturatorius medialis (obb-turr-ahh-tor-ee-us mee-dee-ahl-iss), an antagonist to the ITC, used to swing the leg. It is mostly hidden inside the pelvis so you just see its tendon (dotted line), and especially in turkeys (seriously, they have very nicely visible muscle attachments on their leg bones, for any bird!), a little knobby bit of bone that helps guide the tendon to keep it in its little groove on the femur. Unless you’re very industrious and break open the body cavity to excavate into the pelvis, you won’t be eating this muscle.

The IFE; M. iliofemoralis externus (ill-ee-oh-fem-oh-rahl-iss ex-ter-nuss); arching over the ITC and OM tendons, is a vestigial muscle, often lost in birds, and having little major function but helping a bit to draw the leg away from the body (abduction). Even though it is a puny muscle, it still has a nice little pit for its insertion on the femur. Turkeys are just cool that way. But it’s not much in the way of eating.

And now you know three of the ~40 main muscles of the avian leg, well done! 

I love these muscles not only because I did a lot of my PhD (and later) research on them, but also because they leave great scars on bird and other dinosaurian bones that allow us to reconstruct how muscles evolved. I better stop here or I’ll be writing for days… don’t wind me up further! :)

On the right: the foot of a turkey in front and back views. Lots of ossified tendons are visible if you squint. Why do birds only have ossified tendons below their knee joints, and why only some muscles in some birds, and not so commonly in most other species of land animals? This is one of those cool mysteries that remain for people doing evolutionary or biomechanics research to sort out.

Hope you enjoyed a quick anatomy tour with our pal Meleagris!

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And so we return to the series of posts on non-frozen, but still anatomically awesome, specimens from the RVC’s Anatomy Museum. Refer to posts on dissections, skulls and the introduction if you missed the last three.

Today is for the birds. Feel free to cry fowl if you feel this post is a poultry sum of images. Oh I could go on with lame puns, but I am merciful…

We’ll start with what is presumably not a Norwegian Blue; presumably neither resting and certainly bereft of beautiful plumage, but nonetheless a remarkable bird and great fodder for a wide range of silly jokes:

Which provides us with a segue into our series of nicely mounted skeletons of domestic poultry, first with the super-sized American variety termed Meleagris:

And then with the less titanic but still impressive, fast-growing, large-breasted Gallus:

Which is a reminder of the non-defunct poultry that the RVC maintains, including a sporadic series of chickens that our lab hosts for our research (blog to come soon!), first shown in the fluffy 2 week old stage:

And what a difference 2 weeks makes!

But back to the museum. Perhaps in sympathy for the plight of broiler chickens, a local raptor hangs, wings akimbo, to display various external features:

Plodding along, and missing the cranial end of the skeleton in this photo (in John’s typical photography/research style; d’oh!) is a nice big Maribou stork:

Keeping the birds company is a fellow archosaur, which reminds me of WIJF’s previous post on pelvic differences in archosaurs; here an Alligator:

Nearby there is an ostrich pelvis for a similar comparison as in the latter post. And not far from that is a nice view of an ostrich foot, along with other birds’ feet in a display on perching/pedal adaptations:

For a really stunning image of an ostrich foot, check out this plastinated specimen (more pics like it here). We really like ostriches, so we also have an ostrich head and neck:

These ratite displays remind me of our emu flock that we are maintaining (not at the museum!), which is 13 strong at the moment and very cute at ~8 weeks of age (intriguingly, a similar ~3kg body mass to a 6-week old broiler chicken! But much leggier.):

If you happen to visit the Anatomy Museum to peruse plastinated poultry or oggle other oddities, save time for a stroll to the nearby Grant Museum of Zoology; one of London’s greatest natural history treasures (edit- see recent TetZoo blog post on this) — and one that is drenched in history. Great flightless bird exhibits, too, such as this kiwi:

Or a stunning assortment of dodo bones:

Or, coming full circle, an emu (or so I think… naughty John’s headless-photo bias at play again!).

And the emu will escort you to the exit. Thanks for visiting! We’re nearing the end of this series, so I hope you have enjoyed it.

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