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Happy Darwin Day from the frozen tundra sunny but muddy, frosty lands of England! I bring you limb muscles as peace offerings on this auspicious day. Lots of limb muscles. And a new theme for future blog posts to follow up on: starting off my “Better Know A Muscle” (nod to Stephen Colbert; alternative link) series. My BKAM series intends to walk through the evolutionary history of the coolest (skeletal/striated) muscles. Chuck Darwin would not enjoy the inevitable blood in this photo-tour, but hopefully he’d like the evolution. Off we go, in search of better knowledge via an evolutionary perspective!

There is, inarguably, no cooler muscle than M. caudofemoralis longus, or CFL for short. It includes the largest limb muscles of any land animal, and it’s a strange muscle that confused anatomists for many years– was it a muscle of the body (an axial or “extrinsic” limb muscle, directly related to the segmented vertebral column) or of the limbs (an “abaxial” muscle, developing with the other limb muscles from specific regions of the paraxial mesoderm/myotome, not branching off from the axial muscles)? Developmental biologists and anatomists answered that conclusively over the past century: the CFL is a limb muscle, not some muscle that lost its way from the vertebral column and ended up stranded on the hindlimb.

The CFL is also a muscle that we know a fair amount about in terms of its fossil record and function, as you may know if you’re a dinosaur fan, and as I will quickly review later. We know enough about it that we can even dare to speculate if organisms on other planets would have it. Well, sort of…

Stomach-Churning Rating: 8/10. Lots of meaty, bloody, gooey goodness, on and on, for numerous species. This is an anatomy post for those with an appetite for raw morphology.

Let’s start from a strong (and non-gooey) vantage point, to which we shall return. The CFL in crocodiles and most other groups is (and long was) a large muscle extending from much of the front half or so of the tail to the back of the femur (thigh bone), as shown here:

Julia Molnar's fabulous illustration of Alligator's limb muscles, from our 2014 paper in Journal of Anatomy.

Julia Molnar’s fabulous illustration of Alligator‘s limb muscles, from our 2014 paper in Journal of Anatomy. Note the CFL in blue at the bottom right.

As the drawing shows, the CFL has a friend: the CFB. The CFB is a shorter, stumpier version of the CFL restricted to the tail’s base, near the hip. The “B” in its name means “brevis”, or runty. It gets much less respect than its friend the CFL. Pity the poor CFB.

But look closer at the CFL in the drawing above and you’ll see a thin blue tendon extending past the knee to the outer side of the lower leg. This is the famed(?) “tendon of Sutton“, or secondary tendon of the CFL. So the CFL has two insertions, one on the femur and one (indirectly) onto the shank. More about that later.

Together, we can talk about these two muscles (CFL and CFB) as the caudofemoralis (CF) group, and the name is nice because it describes how they run from the tail (“caudo”) to the femur (“femoralis”). Mammal anatomists were late to this party and gave mammal muscles stupidly unhelpful names like “gluteus” or “vastus” or “babalooey”. Thanks.

But enough abstract drawings, even if they rock, and enough nomenclature. Here is the whopping big CFL muscle of a real crocodile:

Huge Nile crocodile, but a relatively small CFL.

Huge Nile crocodile, but a relatively small CFL.

Bigger crocs have smaller legs and muscles.

Bigger crocs have smaller legs and thus smaller leg muscles, relatively speaking. CFL at the top, curving to the left.

The giant Nile croc's CFL muscle removed for measurements.

The giant Nile croc’s CFL muscle removed for measurements. 2.35 kg of muscle! Not shabby for a 278 kg animal.

However, maybe crocodile and other archosaur CFL muscles are not “average” for leggy vertebrates? We can’t tell unless we take an evolutionary tack to the question.

Where did the CFL come from, you may ask? Ahh, that is shrouded in the fin-limb transition‘s mysteries. Living amphibians such as salamanders have at least one CF muscle, so a clear predecessor to the CFL (and maybe CFB) was present before reptiles scampered onto the scene.

But going further back through the CF muscles’ history, into lobe-finned fish, becomes very hard because those fish (today) have so few fin muscles that, in our distant fishy ancestors, would have given rise eventually to the CF and other muscle groups. With many land animals having 30+ hindlimb muscles, and fish having 2-8 or so, there obviously was an increase in the number of muscles as limbs evolved from fins. And because a limb has to do lots of difficult three-dimensional things on land while coping with gravity, more muscles to enable that complex control surely were needed.

OK, so there were CF muscles early in tetrapod history, presumably, anchored on that big, round fleshy tail that they evolved from their thin, finned fishy one — but what happened next? Lizards give us some clues, and their CFL muscles aren’t all that different from crocodiles, so the CFL’s massive size and secondary “tendon of Sutton” seems to be a reptile thing, at least.

Courtesy of Emma Schachner, a large varanid lizard's very freshly preserved CFL and other hindlimb muscles.

Courtesy of Emma Schachner, a large varanid lizard’s very freshly preserved CFL and other hindlimb muscles.

Courtesy of Emma Schachner, zoomed in on the tendons and insertions of the CFL muscle and others.

Courtesy of Emma Schachner, zoomed in on the tendons and insertions of the CFL muscle and others. Beautiful anatomy there!

Looking up at the belly of a basilisk lizard and its dissected right leg, with the end of the CFL labelled.

Looking up at the belly of a basilisk lizard and its dissected right leg, with the end of the CFL labelled. It’s not ideally dissected here, but it is present.

An unspecified iguanid(?) lizard, probably a juvenile Iguana iguana, dissected and showing its CFL muscle at its end. The muscle would extemd about halfway down the tail, though.

An unspecified iguanid(?) lizard, probably a juvenile Iguana iguana, dissected to reveal its CFL muscle near its attachment to the femur. The muscle would extend further, about halfway down the tail, though.

Let’s return to crocodiles, for one because they are so flippin’ cool, and for another because they give a segue into archosaurs, especially dinosaurs, and thence birds:

A moderate-sized (45kg) Nile crocodile with its CFL muscle proudly displayed.

A moderate-sized (45kg) Nile crocodile with its CFL muscle proudly displayed. Note the healthy sheath of fat (cut here) around the CFL.

American alligator's CFL dominates the photo. Photo by Vivian Allen.

American alligator’s CFL dominates the photo [by Vivian Allen].

Black caiman, Melanosuchus, showing off its CFL muscle (pink "steak" in the middle of the tail near the leg).

Black caiman, Melanosuchus, showing off its CFL muscle (pink “steak” in the middle of the tail near the leg), underneath all that dark armour and fatty superficial musculature.

A closer look at the black caiman's thigh and CFL muscle.

A closer look at the black caiman’s thigh and CFL muscle.

Like I hinted above, crocodiles (and the anatomy of the CFL they share with lizards and some other tetrapods) open a window into the evolution of unusual tail-to-thigh muscles and locomotor behaviours in tetrapod vertebrates.

Thanks in large part to Steve Gatesy’s groundbreaking work in the 1990s on the CFL muscle, we understand now how it works in living reptiles like crocodiles. It mainly serves to retract the femur (extend the hip joint), drawing the leg backwards. This also helps support the weight of the animal while the foot is on the ground, and power the animal forwards. So we call the CFL a “stance phase muscle”, referring to how it mainly plays a role during ground contact and resisting gravity, rather than swinging the leg forwards (protracting the limb; i.e. as a “swing phase muscle”).

The “tendon of Sutton” probably helps to begin retracting the shank once the thigh has moved forward enough, facilitating the switch from stance to swing phase, but someone really needs to study that question more someday.

And thanks again to that same body of work by Gatesy (and some others too), we also understand how the CFL’s anatomy relates to the underlying anatomy of the skeleton. There is a large space for the CFL to originate from on the bottom of the tail vertebrae, and a honking big crest (the fourth trochanter) on the femur in most reptiles that serves as the major attachment point, from which the thin “tendon of Sutton” extends down past the knee.

Femur bones (left side) from an adult ostrich (Left) and Nile crocodile (Right).

Femur bones (left side; rear view) from an adult ostrich (left) and Nile crocodile (right). Appropriate scale bar is appropriate. The fourth trochanter for the CFL is visible in the crocodile almost midway down the femur. Little is left of it in the ostrich but there is a bumpy little muscle scar in almost the same region as the fourth trochanter, and this is where the same muscle (often called the CFC; but it is basically just a small CFL) attaches.

That relationship of the CFL’s muscular anatomy and the underlying skeleton’s anatomy helps us a lot! Now we can begin to look at extinct relatives of crocodiles; members of the archosaur group that includes dinosaurs (which today we consider to include birds, too), and things get even more interesting! The “tendon of Sutton”, hinted at by a “pendant” part of the fourth trochanter that points down toward the knee, seems to go away multiple times within dinosaurs. Bye bye! Then plenty more happens:

A large duckbill dinosaur's left leg, with a red line drawn in showing roughly where the CFL would be running, to end up at the fourth trochanter. Many Mesozoic dinosaurs have skeletal anatomy that indicates a similar CFL muscle.

A large duckbill dinosaur’s left leg, with a red line drawn in showing roughly where the CFL would be running, to end up at the fourth trochanter. Many Mesozoic dinosaurs have skeletal anatomy that indicates a similar CFL muscle.

We can even go so far as to reconstruct the 3D anatomy of the CFL in a dinosaur such as T. rex ("Sue" specimen here; from Julia Molnar's awesome illustration in our 2011 paper), with a fair degree of confidence.

We can even go so far as to reconstruct the 3D anatomy of the CFL in a dinosaur such as T. rex (“Sue” specimen here; from Julia Molnar’s awesome illustration as part of our 2011 paper), with a fair degree of confidence. >180kg steak, anyone?

As we approach birds along the dinosaur lineage, the tail gets smaller and so does the fourth trochanter and thus so must the CFL muscle, until we’re left with just a little flap of muscle, at best. In concert, the hindlimbs get more crouched, the forelimbs get larger, flight evolves and voila! An explosion of modern bird species!

Ozburt (72)

Left femur of an ostrich in side view (hip is toward the right side) showing many muscles that attach around the knee (on the left), then the thin strap of CF muscle (barely visible; 2nd from the right) clinging near the midshaft of the femur.

Another adult ostrich's CF muscle complex, removed for study.

Another adult ostrich’s CF muscle complex, removed for study. Not enough ostrich myology for you yet? Plenty more in this old post! Or this one! Or this one… hey maybe I need to write less about ostriches? The CF muscle complex looks beefy but it’s no bigger than any other of the main hindlimb muscles, unlike the CFL in a crocodile or lizard, which puts everything else to shame!

STILL not enough ostrich for you yet? Take a tour of the major hindlimb muscles in this video:

And check out the limited mobility of the hip joint/femur here. No need for much femur motion when you’re not using your hip muscles as much to drive you forwards:

But I must move on… to the remainder of avian diversity! In just a few photos… Although the CF muscles are lost in numerous bird species, they tend to hang around and just remain a long, thin, unprepossessing muscle:

Chicken's right leg in side view. CFC (equivalent of CFL) muscle outlined and labelled.

Chicken’s right leg in side view. CFC muscle (equivalent of CFL; the ancestral CFB is confusingly called the CFP in birds, as it entirely resides on the pelvis) outlined and labelled.

A jay (species?) dissected to show some of the major leg muscles, including the CF. Photo by Vivian Allen.

A jay (species? I forget) dissected to show some of the major leg muscles, including the CFL-equivalent muscle; again, smallish. [Photo by Vivian Allen]

Finally, what’s up with mammals‘ tail-to-thigh CF-y muscles? Not much. Again, as in birds: smaller tail and/or femur, smaller CF muscles. Mammals instead depend more on their hamstring and gluteal muscles to support and propel themselves forward.

But many mammals do still have something that is either called the M. caudofemoralis or is likely the same thing, albeit almost always fairly modest in size. This evolutionary reduction of the CF muscle along the mammal (synapsid) lineage hasn’t gotten nearly as much attention as that given to the dinosaur/bird lineage’s CFL. Somebody should give it a thoroughly modern phylogenetic what-for! Science the shit outta that caudofemoralis…

Yet, oddly, to give one apparent counter-example, cats (felids) have, probably secondarily, beefed up their CF muscle a bit:

Cats have a pretty large CF muscle in general, and this jaguar is no exception! But mammals still tend to have fairly wimpy tails and thus CF muscles, or they even lose them (e.g. us?).

Cats have a pretty large CF muscle in general, and this jaguar is no exception! But mammals still tend to have fairly wimpy tails and thus CF muscles, or they even lose them (e.g. us?). [photo by Andrew Cuff, I think]

In summary, here’s what happened (click to embeefen):

Better Know A Muscle: The Evolution of M. caudofemoralis (longus)

Better Know A Muscle: the evolution of M. caudofemoralis (longus).

I hope you enjoyed the first BKAM episode!
I am willing to hear requests for future ones… M. pectoralis (major/profundus) is a serious contender.

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Tonight is the debut of the ballyhooed BBC1 programme “Attenborough and the Giant Dinosaur“, featuring Sir David and The Titanosaur-With-No-Name, at 6:30pm. Furthermore, this week I presided over a showing of “T. rex Autopsy” to our RVC undergrad Zoological Society, with a very enjoyable Q&A afterwards. So it seemed timely for me to do a post about a theme that links these two documentaries that I helped with, my own research, and science communication and palaeontological research more generally. But first let’s get this out of the way:

It was great.

It was great. I could gush more but that’s not what this post is about.

Stomach-Churning Rating: ~7/10; mainly the elephant leg dissection that’s not far below, which is a bit messy.

For the titanosaur documentary with Sir David, and the incomparable Ben Garrod as well, we had an old elephant “friend” of mine (subject of many biomechanics studies we’d done) walk across a pressure pad to demonstrate how the elephant locomotion works and some of the basic similarities with how a giant sauropod dinosaur might walk:

A broader feature of that documentary, which elephants are linked into, is how we can use the skeleton to reconstruct some general aspects of the soft tissue anatomy, and thereby the physiology or even behaviour, of a giant titanosaur. Which brings me to this post’s subject: We dig up dinosaurs all the time, but what about digging into dinosaurs and using what’s preserved to reconstruct what isn’t? 

The "G-suit" compressive stocking that the fascia wrapped around elephant, and other large mammals, creates, and the underlying, interwoven muscles and tendons (hindlimb of a young Asian elephant).

Some of the “G-suit” compressive stocking that the fascia wrapped around elephant, and other large mammals, creates, and the underlying, interwoven muscles and tendons (hindlimb of a young Asian elephant that sadly died in captivity). Did some larger dinosaurs have something like this? I’d expect so.

Another view, more superficially, of that G-suit/stocking under the thick, tight skin of an elephant's leg.

Another view, more superficially, of that G-suit/stocking under the thick, tight skin of an elephant’s leg. You’ll hear more about this in the Attenborough show…

Once the documentary airs, I may be able to share some more images from it showing what they did for the titanosaur, but this BBC photo gives a good idea.

Once the documentary airs, I may be able to share some more images from it showing what they did for the titanosaur, but this BBC photo gives a good idea. Here, blood vessels and other tissues surrounding the skeleton. How would a titanosaur pump blood around its body? A good question.

I’ve covered the science behind these reconstructions before, along with the art (in numerous posts, actually). Here I want to inspect how it’s communicated through the media: what are good (and not so good?) ways to cover it, especially now that displaying raw anatomy is more tolerable on TV and other media? I’m not writing about Thanksgiving dinner dinosaur dissections; not really; or in technical terms how we build a dinosaur to dissect/depict internally (digitally or physically).

I wanted to focus more on the end product; the imagery or even physical object; and how it conveys what we think we know about dinosaur anatomy. I’ll do that via examples, using photos of dinosaur anatomy that I’ve collected over the years from museums or other media. There won’t be any profound points or long musings; it’s mainly a photo blog:

What your (inner?) child most needs is a dinosaur to dissect yourself! Why not a T. rex toy like this?

What your (inner?) child most needs is a dinosaur to dissect yourself! Why not a T. rex toy like this?

I could quibble, but for the price they did a good job.

For the price (~$30 in USA), the 4D Vision dinosaurs deliver a pretty good bargain, and the anatomy is satisfactory. I’ve been collecting this series. I could quibble, but hey: it’s a dinosaur you get to build/dissect yourself, and with many major organs in reasonable positions! Not so easy to put/keep together, but it’s fine. I would not pay a ton for it, though.

Poster of Velociraptor's anatomy I've had since grad school, adorning my office. For ~1996, it's damn good, mostly... (placeholder photos until I get to the office tomorrow and take better ones!)

Poster of Velociraptor’s anatomy I’ve had since grad school, adorning my office. For ~1996 (no feathers; “zombie hands“), it’s damn good, mostly… Closer views below (sorry, photo quality is crap– taking photos of wall poster turned out to be harder than I expected! Bad lighting.) :

Closeup of the leg muscles- hey, not bad!

Closeup of the leg muscles- hey, not bad! Pretty much the right muscles in the right places more or less, and plausible proportions. No air sacs in the torso, but again, this is mid-1990’s science shown. BUT…

I was happy with this poster until I got it home and read this final bit of text... Oh, America! You silly place.

I was happy with this poster until I got it home from the western-USA museum I bought it at and read this final bit of text… Oh, America! You silly place. (And unfortunately, these dinosaurs are not from the very end of the Cretaceous anyway, so “global catastrophe” is not implicated.)

Ornithomimid in Barcelona natural history museum. This was unexpected and got me excited when I first saw it.

Ornithomimid in Barcelona natural history museum. This was unexpected and got me excited when I first saw it.

Looking down onto the opened torso of the Barcelona ornithomimid. Strikingly realistic!

Looking down onto the opened torso of the Barcelona ornithomimid. Strikingly realistic! Breastbone, heart, liver, intestines; not unreasonable positions and sizes. No feathers, but again hey– this was made in the earlier days.

Skinned Albertosaurus from the Drexel Academy of Sciences. I forget where I got this pic but I like the display.

Albertosaurus from the Drexel Academy of Sciences. I forget where I got this pic but I like the display– this is an impressive full-scale physical model. The transition from skeleton-only on the left to skinned in the middle to fully-fleshed and popping out atcha on the right is clever.

?T. rex? leg, photo that I took ages ago as a PhD student, if memory serves. Can anyone remind me where this was? California Academy of Sciences?

?T. rex? leg, photo that I took ages ago as a PhD student, if memory serves. Can anyone remind me where this was? California Academy of Sciences? I am embarrassed that I cannot recall. I remember geeking out about it. It has a toy-ish look, but I reckon they had to build this to withstand kids touching it.

Perhaps the best example I've seen in a museum: the AMNH's sauropod with internal organs and their functions projected onto it. Bravo!

Perhaps the best dino-dissection example I’ve seen in a museum: the AMNH’s sauropod Mamenchisaurus with internal organs and their functions projected onto it, in the “World’s Largest Dinosaurs” exhibit. Bravo! I stood and watched it for quite a while.

This is far from comprehensive– just several kinds of imagery that I mostly like. There’s the tension between showing too much realism, which science simply can’t back up, and being too cartoonish, losing the viewer’s immersion in the time-travelling fantasy. I do, however, like other kinds of more abstract, schematic depictions of dinosaur anatomy that simplify the details to focus on the basics of what organs should have been where and how they may have worked, such as this depiction from T. rex Autopsy, which also took the other extreme favouring ultra-realism (but with physical models, not so much with the CGI):

AIr flow through a T. rex: simplified but clear.

Air flow through a T. rex: simplified but clear. CGI used to explain, not abused. The real air sac anatomy would be too complex to show. You may see something similar with the titanosaur show.

That’s enough for now. I’ve stuck with relatively recent examples; of course in my particular field I also think back to Romer’s wonderful 1920’s drawings, which I covered in this post.

So, blog readers, help me out here: what examples of dinosaur internal, squishy anatomy from museums, documentaries or other not-entirely-done-by-nitpicky-scientists venues do you like, or not like so much? What works for you, or at least is memorable in some way?

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Greetings Freezerinos, and Happy New Year! I have been quiet on this blog for health and other reasons but those will pass and there will be new posts in 2016. However, behind the scenes there have been super-cool things afoot. I am very happy to bring one of them to you now:

(but first: Stomach-Churning Rating: 6/10; video below shows a dissected sea turtle foot in motion)

We have just debuted our new social media “presence” (for lack of a better word) that is a sister blog to this one. It is called Anatomy To You (http://anatomytoyou.com/), as its intent is to bring a wide array of science about animal anatomy to “you”, the general public. This John’s Freezer blog will continue with it’s style of rambling longer posts targeted at a fairly geeky scientifically literate audience and focusing on my team’s research and my own disparate thoughts about science and related issues. Anatomy To You will bring you shorter posts, even just images, completely focused on celebrating the structure of organisms, and not just presenting my team’s research but also a wide array of anatomical science from around the globe. It will also be much more regular and frequent in its posts. We’ll welcome guest posts and I encourage you to get in touch with us if you want to jump on the bandwagon early, or have us feature your research for you!

More about the ATY blog is here, but there is also a Twitter feed and Facebook account. Our first major posts are on what skeletons are, and on a dissection of some sea turtles. Please follow us and join in the celebration of anatomy! My team’s scientific communicator/technician Dr. Lauren Sumner-Rooney is spearheading this ATY effort with me, so please follow her too!

Anatomy To You will continue to evolve over this coming year, so please stay with us and give us feedback; join in the morphological conversations with us. I am SUPER excited to see where this goes– it is an experiment that has a lot of potential, we think.

Sea turtle from our ATY dissection, foot muscles in action (found dead in the wild; don’t be ridiculous, we don’t kill sea turtles for our research)

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Seeking adaptations for running and swimming in the vertebral columns of ancient crocs

A guest post by Dr. Julia Molnar, Howard University, USA (this comes from Julia’s PhD research at RVC with John & colleagues)

Recently, John and I with colleagues Stephanie Pierce, Bhart-Anjan Bhullar, and Alan Turner described morphological and functional changes in the vertebral column with increasing aquatic adaptation in crocodylomorphs (Royal Society Open Science, doi 10.1098/rsos.150439). Our results shed light upon key aspects of the evolutionary history of these under-appreciated archosaurs.

Stomach-Churning Rating: 5/10; a juicy croc torso in one small photo but that’s all.

Phylogenetic relationships of the three crocodylomorph groups in the study and our functional hypotheses about their vertebrae. * Image credits: Hesperosuchus by Smokeybjb, Suchodus by Dmitry Bogdanov (vectorized by T. Michael Keesey) http://creativecommons.org/licenses/by-sa/3.0

Phylogenetic relationships of the three crocodylomorph groups in the study and our functional hypotheses about their vertebrae. * Image credits: Hesperosuchus by Smokeybjb, Suchodus by Dmitry Bogdanov (vectorized by T. Michael Keesey) http://creativecommons.org/licenses/by-sa/3.0

As fascinating as modern crocodiles might be, in many ways they are overshadowed by their extinct, Mesozoic cousins and ancestors. The Triassic, Jurassic, and early Cretaceous periods saw the small, fast, hyper-carnivorous “sphenosuchians,” the giant, flippered marine thalattosuchians, and various oddballs like the duck-billed Anatosuchus and the aptly named Armadillosuchus. As palaeontologists/biomechanists, we looked at this wide variety of ecological specializations in those species, the Crocodylomorpha, and wanted to know, how did they do it?

Of course, we weren’t the first scientists to wonder about the locomotion of crocodylomorphs, but we did have some new tools in our toolbox; specifically, a couple of micro-CT scanners and some sophisticated imaging software. We took CT and micro-CT scans of five fossil crocodylomorphs: two presumably terrestrial early crocodylomorphs (Terrestrisuchus and Protosuchus), three aquatic thalattosuchians (Pelagosaurus, Steneosaurus, and Metriorhynchus) and a semi-aquatic modern crocodile (Crocodylus niloticus). Since we’re still stuck on vertebrae (see, e.g., here; and also here), we digitally separated out the vertebrae to make 3D models of individual joints and took measurements from each vertebra. Finally, we manipulated the virtual joint models to find out how far they could move before the bones bumped into each other or the joints came apart (osteological range of motion, or RoM).

 

Our methods: get fossil, scan fossil, make virtual fossil and play with it.

Our methods: get fossil (NHMUK), scan fossil, make virtual fossil and play with it.

Above: Video of a single virtual inter-vertebral joint from the trunk of Pelagosaurus typus (NHMUK) showing maximum osteological range of motion in the lateral direction (video). Note the very un-modern-croc-like flat surfaces of the vertebral bodies! (modern crocs have a ball-and-socket spinal joint with the socket on the front end)

While this was a lot of fun, what we really wanted to find out was whether, as crocodylomorphs became specialized for different types of locomotion, the shapes of their vertebrae changed similarly to those of mammalian lineages. For example, many terrestrial mammals have a lumbar region that is very flexible dorsoventrally to allow up-and-down movements during bounding and galloping. Did fast-running crocodylomorphs have similar dorsoventral flexibility? And did fast-swimming aquatic crocodylomorphs evolve a stiffer vertebral column like that of whales and dolphins?

Above: Video of how we modelled and took measurements from the early crocodylomorph Terrestrisuchus gracilis (NHMUK).

Our first results were puzzling. The Nile croc had greater RoM in side-to-side motions, which makes sense because crocodiles mostly use more sprawling postures and are semi-aquatic, using quite a bit of side-to-side motions in life. The part that didn’t make sense was that we found pretty much the same thing in all of the fossil crocodylomorphs, including the presumably very terrestrial Terrestrisuchus and Protosuchus. With their long limbs and hinge-like joints, these two are unlikely to have been sprawlers or swimmers!

So we started looking for other parts of the croc that might affect RoM. The obvious candidate was osteoderms, the bony scales that cover the back. We went back to John’s Freezer and got out a nice frozen crocodile to measure the stiffness of its trunk and found that, sure enough, it was a lot stiffer and less mobile without the osteoderms. If the fairly flexible arrangement of osteoderms in crocodiles had this effect on stiffness, it seemed likely that (as previous authors have suggested; Eberhard Frey and Steve Salisbury being foremost amongst them) the rigid, interlocking osteoderms running from head to tail in early crocodylomorphs would really have put the brakes on their ability to move their trunk in certain ways.

Testing stiffness of crocodile trunks to learn the effects of osteoderms, skin, muscles, and ribs. We hung metric weights from the middle of the trunk and measured how much it flexed (Ɵ), then removed bits and repeated.

Testing the stiffness of (Nile) crocodile trunks to learn the effects of osteoderms, skin, muscles, and ribs. We hung metric weights from the middle of the trunk and measured how much it flexed (Ɵ), then removed bits and repeated. Click to em-croccen.

Another cool thing we found was new evidence of convergent evolution to aquatic lifestyles in the spines of thalattosuchians. The more basal thalattosuchians, thought to have been near-shore predators, had stiffness and RoM patterns similar to Crocodylus. But Metriorhynchus, which probably was very good at chasing down fast fish in the open ocean, seems to have had greater stiffness. (The stiffness estimates come from morphometrics and are based on modern crocodiles; see here again, or just read the paper already!) A stiff vertebral column can be useful for a swimmer because it increases the body’s natural frequency of oscillation, and faster oscillation means faster swimming (think tuna, not eel). The same thing seems to have happened in other secondarily aquatic vertebrate lineages such as whales, ichthyosaurs, and mosasaurs.

So, our results were a mixed bag of adaptations particular to crocs and ones that seem like general vertebrate swimming specializations. Crocodylomorphs are important because they are the only group of large vertebrates other than mammals that has secondarily aquatic members and has living members with a reasonably similar body plan, allowing us to test hypotheses in ways that would arguably be impossible for, say, non-avian dinosaurs and birds. The take-home message: crocodylomorphs A) are awesome, and B) can teach us a lot about how vertebrates adapt to different modes of life.

Another take on this story is on our lab website here.

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I was recently featured on Daily Planet, a great Canadian science show on TV that lamentably is not broadcast more globally. It is always high quality science communication, aided by the superb hosts Ziya Tong and Dan Riskin (and a talented crew!). What were we doing? Dissecting an elephant’s foot, of course!

Stomach-Churning Rating: 9/10; no-holds-barred dismantling of elephant feet, from the video onwards, and this post is heavy on moist, goopy photos afterwards, with some nasty pathologies. Not nice at all. I’ll give you a chance to turn around while contemplating the cart that we use to carry elephant feet around campus (each foot is 20-30kg; up to 70lbs; so we need the help!), before the video.

no_poo

Here is a snippet of the full segment from Daily Planet:

And here is more of some of my recent dissections. I’ll walk you through two dissections, via photos. This goes back to the roots of this blog: unflinching, gritty examinations of real anatomy! Of course, no elephants were harmed for this work. They died at EU zoos/parks and were sent to me for postmortem examination and research, so we hope that this benefits the future care of elephants. We’re currently finishing up a grand overview paper that describes all of the odd pathologies we’ve observed in elephant feet, for the benefit of zoo keepers and vets who are trying to detect, diagnose and monitor any foot problems.

As the post’s title alludes, elephant feet (and more proximal parts of the limbs) are no stranger to this blog. If you’ve forgotten or are unfamiliar, here are some of my past proboscidean-posts: on elephant foot pathologies (a close sister post to this one), our “six-toed” elephants paper, how to make a computer simulation of an elephant’s limb (umm, paper yet to come!), how we boil and bleach bones to clean them up, and a few others. Last but not least, there was the post that went viral in the early #JohnsFreezer/WIJF days: dissecting an elephant with the “Inside Nature’s Giants” show.

There are two feet in this post, both front right feet (manus is the technical term; singular and plural). The first one is the messier (unhealthy and bloodier, less fresh and clean) one, from the show/video. It is an Asian elephant (Elephas maximus). I kick off with photos I took after the filming, so the foot is already deconstructed:

Skinned foot, oblique front/inside view.

Skinned foot, oblique front/inside view. The wrist is on the right side of the photo; the toes on the left.

Sole ("slipper"), with a hole on the fourth toe showing where the abscess is that let infection in/pus drain out.

Sole (“slipper”), with a hole on the fourth toe showing where the abscess is that let infection in/pus drain out. The slipper here is upside-down.

Top-down view of the sole of the foot, once the slipper is removed.

Top-down view of the sole of the foot, once the slipper is removed; flipped over and rotated 90 degrees clockwise from the above photo. Some of the fat pad of the foot is on the right side of the image; it’s very hard to separate from the keratinous sole of the foot.

Looking down into the fourth toe's abscess on the other side of the above view.

Looking down into the fourth toe’s (ring finger) abscess on the other side of the above view.

Looking down into the third (middle) toe, same view as above. Some redness and greyness where this toe had some of its own pathological issues.

Looking down into the second toe (index finger), same view as above. Some redness and greyness where this toe had some of its own pathological issues like infection and a smaller abscess.

Looking up from the slipper at the fat pad and toes of the foot, where they interface with the sole/slipper. The fat pad is toward the bottom and left side; the five toes are on the upper/right side (knobby subcircular regions on the perimeter of the foot).

Looking up from the slipper (removed) at the fat pad and toes of the foot, where they interface with the sole/slipper. The fat pad is toward the bottom and left side; the five toes are on the upper/right side (knobby subcircular regions on the perimeter of the foot). The very bad infection on the fourth toe is visible on the bottom right.

The sproingy fat pad is worth a video!

And one good wiggle deserves another!

A view down onto the wrist joint. The carpal (wrist) bones are visible at the bottom of the image, whereas the flexor (palmar) tendons and muscles on the back of the "hand" are at the top. There is a LOT of musculotendinous tissue on the back side of an elephant's foot.

A view down onto the wrist joint. The carpal (wrist) bones are visible at the bottom of the image, whereas the flexor (palmar) tendons and muscles on the back of the “hand” are at the top. There is a LOT of musculotendinous tissue on the back side of an elephant’s foot. As you will see in my dissection of the second foot, further below!

Looking down onto the medial (inner/"thumb") border of the foot, where I've exposed the prepollex, or false "sixth finger" by removing the first metacarpal (knuckle) bone.

Looking down onto the medial (inner/”thumb”) border of the foot, where I’ve exposed the prepollex, or false “sixth finger”, by removing the first metacarpal (knuckle) bone.

Removed the prepollex from the foot. The white oval structure is the top of the prepollex; white is cartilage, whereas the red "islands" are blood vessels that have invaded the cartilage and are starting to turn it into patches of bone. So this prepollex is at a very early stage of bone formation, still almost entirely cartilaginous, whereas some older elephants have the prepollex largely formed of bone.

I’ve removed the prepollex from the foot. The white oval structure (bottom right) is the top of the conical prepollex, where it connected to the rest of the foot. White is cartilage, whereas the red “islands” are blood vessels that have invaded the cartilage and are starting to turn it into patches of bone. So this prepollex is at a very early stage of bone formation, still almost entirely cartilaginous, whereas some older elephants have the prepollex largely formed of bone. The fleshy pink tissue adhering to the surface of the prepollex here is a remnant of “abductor” muscle that connects it to the thumb and thus could allow some active control of the prepollex’s mobility.

Well, that was one very pathological elephant’s foot; one of the worst I have ever seen. Every foot I dissect is different and tells me a unique story about that animal’s development, history and health. This one told a very sad tale. What does a somewhat normal elephant’s foot look like? I thawed one out for comparison, and to thin out my overstuffed freezer stock. This one starts off from an intact (if severed) foot so you can witness the stages of dissection:

Whole foot. African elephant (Loxodonta africana).

Whole foot. African elephant (Loxodonta africana). You may spot in later photos that the second and fourth toes’ nails are cracked longitudinally. This happens sometimes in elephants without any obvious health problems such as infection, but if it lasts long enough and conditions are bad enough (e.g. unsanitary conditions getting bacteria into the crack; spreading the crack to let them into the foot tissue), it could worsen.

Nice clean sole.

Nice clean sole. No abscesses or other problems. You can faintly see the cracked toenails here.

Gorgeous white cartilage surfaces of the wrist joints. Nice and healthy-looking. A young animal, in this case.

Gorgeous white cartilage surfaces of the wrist joints. Nice and healthy-looking. A young animal, in this case.

Removing the skin; nice soft whitish connective tissue underneath.

Removing the skin; nice soft whitish connective tissue underneath.

Skinned foot; rear view. The yellowish fat pad is wonderfully visible through the connective tissue sheath.

Skinned foot; rear view. The yellowish fat pad is wonderfully visible through the connective tissue sheath.

Skinned foot; front view. The thin, broad extensor tendons that would draw the fingers forward in life are visible here as longitudinal lines along the foot's surface, running to the toes.

Skinned foot; front view. The thin, broad extensor tendons that would draw the fingers forward in life are visible here as longitudinal lines along the foot’s surface, running to the toes.

Ahh, my favourite thing! I've cut around the prepollex and am pointing at it. It's almost impossible otherwise to see through all the fatty tissue of the fat pad that surrounds it.

Ahh, my favourite thing! I’ve cut around the prepollex and am pointing at it. It’s almost impossible otherwise to see through all the fatty tissue of the fat pad that surrounds it.

Removing the prepollex. It's tiny and enmeshed in connective tissue; harder to see than in the first elephant (photos above).

Removing the prepollex. It’s tiny and enmeshed in connective tissue; harder to see than in the first elephant (photos above).

There is the prepollex! Maybe 12cm long. A little bit of cartilage (white) visible where it connected to the foot. These "sesamoid bones" vary tremendously in elephants I've inspected. I am still getting my head around that, after >10 years of staring at them in >75 feet!

There is the prepollex! Maybe 12cm long. A little bit of cartilage (white) visible where it connected to the foot. These “sesamoid bones” vary tremendously in elephants I’ve inspected. I am still getting my head around that, after >10 years of staring at them in >75 feet!

Gap left by removal of the prepollex, on the median border of the foot; thumb region. Imagine having a little extra thumb growing off the base of your thumb and sticking toward your palm. That's what elephants have.

Gap left by removal of the prepollex, on the median border of the foot; thumb region. Imagine having a little extra thumb growing off the base of your thumb and sticking toward your palm. That’s what elephants have.

Here, removing the slipper/sole of the foot, from the back side forwards. Hard work!

Here, removing the slipper/sole of the foot, from the back side forwards. Hard work!

The slipper. Compare with the image above (same orientation). Nothing wrong here that I could see.

The slipper. Compare with the image above (same orientation). Nothing wrong here that I could see.

Front view of the toes, where they connect to the toenails. This specimen was so fresh that they were surprisingly easy to cut through and remove the foot from the sole.

Front view of the toes, where they connect to the toenails. This specimen was so fresh that they were surprisingly easy to cut through and remove the foot from the sole.

Looking up at the palm. You can see the bulbous fat pad (yellower tissue) bulging out in the centre of the palm, and segments of it extending between each finger, separated by fibrous tracts. I love this anatomy. I can stare at it for hours and still be fascinated after all these years. So complex!

Looking up at the palm. You can see the bulbous fat pad (yellower tissue) bulging out in the centre of the palm, and segments of it extending between each finger, separated by fibrous tracts. I love this anatomy. I can stare at it for hours and still be fascinated after all these years. So complex!

Looking down onto the inside of the toenails, toes 3 and 4. Healthy, relatively intact tissue; no swelling or bleeding or other pathology.

Looking down onto the inside of the toenails, toes 3 and 4. Healthy, relatively intact tissue; no swelling or bleeding or other pathology.

Skinned foot, oblique front/inside view again, as above.

Skinned foot, oblique front/inside view again, as above.

Fat pad removed, looking up through where it was at the palm of the "hands", where the tendons and ligaments connect to the five toes. Each arc-like structure is a toe; the "thumb" (first toe) is on the upper left.

Fat pad removed, looking up through where it was at the palm of the “hands”, where the tendons and ligaments connect to the five toes. Each arc-like structure is a toe; the “thumb” (first toe) is on the upper left.

Elephant's-eye-view looking down onto the fat pad, where the palm of the foot in the image below would be placed in life.

Elephant’s-eye-view looking down onto the fat pad, where the palm of the foot in the image below would be placed in life (i.e. the limb would be coming down vertically, perpendicular to the plane of the image). The fat pad of the foot is visibly thicker toward the back of the foot (bottom of the image), as you’d expect, because the toes occupy most of the front parts.

Palmar tendons and muscles; the common digital extensor muscle group. Clenches the toes. Not a small muscle, either!

Palmar tendons and muscles; the common digital extensor muscle group, which clenches the toes. Not a small muscle, either!

Tendons of the digital flexor muscle exposed.

Tendons of the digital flexor muscle exposed.

Removed the digital flexor muscle so the three major tendons can be seen (the two short side branches to the first and fifth toes have been cut off).

I removed the digital flexor muscle so the three major tendons can be seen (the two short side branches to the first and fifth toes have been cut off).

Forefoot with flexor tendons removed, revealing the channels that they coursed through.

Forefoot with flexor tendons removed, revealing the channels that they coursed through.

Closeup of the glistening channels for the flexor tendons. They are lined with lubricative tissue to help the tendons glide through them. And the tendons do need to be able to glide- although elephant feet look very solid from the outside, and are to an extent, but we've done studies showing that they do move if you apply even a moderate load to them in a cadaver, and thus would move in life, too.

Closeup of the glistening channels for the flexor tendons. They are lined with lubricative tissue to help the tendons glide through them. And the tendons do need to be able to glide- although elephant feet look very solid from the outside, and are to an extent, but we’ve done studies showing that they do move if you apply even a moderate load to them in a cadaver, and thus would move in life, too.

Let’s finish off with some osteology, shall we? First the unhealthy Asian elephant, then the healthy African elephant; same front right feet, just the bones (from my CT scans):

Ouch, indeed!

Much better. And that’s the end!

Wow, that was an elephantine post! I wanted to take yet another opportunity to share the amazing anatomy of elephant feet with you. You’re all now qualified experts if you made it this far!

Any questions?

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Goat morphology is cool! (from work with local artist)

I posted the above photo once before, but didn’t explain any of the fun details of artist-designer Thomas Thwaites‘s visit to the RVC to dissect a goat with us. Now his show has just finished in London, celebrating the end of his project and the near-completion of his book about his experience trying to live life as a goat. This week, I went to his east side gallery and had some time to chat with Thomas about his transhuman experiences. Because the project has a strong biomechanics, anatomy, art and science theme to it, I’m posting a photo-blog post about all of that. It’s goat to be seen to be believed! I for one wouldn’t mind being a goat right now; I could use a break from my decrepit body…

Stomach-Churning Rating: Too late, there’s the goat pic above and more like it below. I’d give those a 8/10; no kidding. The puns make it worse, too.

The context

The context. Thomas never did get to gallop (sorry, spoiler!) but he did manage a trot, and some other capricious behaviours. I forgot to ask him if he’d tried the Goat Simulator. I have; it’s good for an hour of fun hircosity.

Starting the dissection at the RVC.

Starting the dissection at the RVC, to get inside a goat.

Hide.

Hide.

Fore- and hindlimbs.

Fore- and hindlimbs; comparative design for inspiring prosthetics.

Dissections!

Dissections on display!

Prototype goat-suits. Their mobility was too limited.

Prototype goat-suits. Their mobility was too limited.

The prototype in the foreground could not move without falling down.

The prototype in the foreground could not move without falling down.

Goat-suit shots.

Inhabited-goat-suit shots.

The Goat-Suit: custom made prothetics, a helmet, and some form-fitting casts.

The final Goat-Suit: custom prosthetics, a helmet, and some form-fitting casts.

Thomas Thwaites with the goat-suit.

Thomas Thwaites with the goat-suit.

The forelimb prosthesis. I was worried it would hurt his wrists but apparently it transferred the loads mainly to the forearms.

The forelimb prosthesis. I was worried it would hurt his wrists but apparently it transferred the loads mainly to the forearms. It was made by a prosthetics clinic up in Salford.

Showroom

Photos from rambling around the Swiss Alps in the goat-suit with goats.

Trip-trap-trip-trap...

Trip-trap-trip-trap… (but no trolls)

Goat-suit in action!

Goat-suit in action! With Goat-Pro camera, I see.

Acceptance?

Acceptance?

And the goat that we had dissected, skeletonized at RVC and re-articulated by Thomas:

Do goats wish they were human?

Do goats wish they were human?

What are you looking at?

What are you looking at?

Close-up of goat head.

Close-up of goat head and shoulders.

Goat hooves-on-hips

Goat hooves-on-hips; a gruff pose.

So like us.

So like us.

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I have an impression that there is a large disparity between how the public views museums and how scientists who use museums view them. Presumably there are survey data on public attitudes, but surely the common impression is that museums mainly exist to exhibit cool stuff and educate/entertain the public. Yet, furthermore, I bet that many members of the public don’t really understand the nature of museum collections (how and why they are curated and studied) or what those collections even look like. As a researcher who tends to do heavily specimen-oriented and often museum-based research, I thought I’d take the opportunity to describe my experience at one museum collection recently. This visit was fairly representative of what it’s like, as a scientist, to visit a museum with the purpose of using its collection for research, rather than mingling with the public to oggle the exhibits — although I did a little of that at the end of the day…

Stomach-Churning Rating: 4/10; mostly bones except a jar of preserved critters, but also some funky bone pathologies! Darwin hurls once, totally blowing chunks, but only in text.

Early camel is sitting down on the job at the NHMLA.

Early camel is sitting down on the job at the NHMLA.

About two weeks ago, I had the pleasure to spend a fast-paced day in the Ornithology collection of the Natural History Museum of Los Angeles County (NHMLA or LACM). I arranged the visit (you have to be a credible researcher to get access; luckily I seemed to be that!) via email, took an Uber car to the museum, and was quickly cut loose in the collection. I was hosted by the Collections Manager Kimball Garrett, who is an avid birder (adept at citizen science, too!) and a longtime LA native.

Amongst museum curators and collections managers (there can be a distinction between the two but here I’ll refer to them all as “curators”), there is a wide array of attitudes toward and practices with museum collections, regarding how the curators balance their varied duties of not only making the museum collection accessible to researchers (via behind-scenes studies) and the public (via exhibits and behind-scenes tours etc.), but also curation (maintaining a record of what they have in their collection, adding to it, and keeping the specimen in good condition), research, admin, teaching and other duties.

Most curators I’ve known, like Kimball, are passionate about all of these things, and very generous with their time to help scientists make the most of the collection during their visit, offering hospitality and cutting through the bureaucracy as much as possible to ensure that the science gets done. There are those few curators that aren’t great hosts because they’ve had a bad day or a bad attitude (e.g. obsession with paperwork and finding obstacles to accessing specimens for research; or just not responding to communication), but they are few and far between in my experience.

Regardless, the curator is the critical human being that keeps the wheels of specimen-based museum research rolling, and I am appreciative of how deeply dedicated and efficient most curators are. Indeed, I enjoy meeting and chatting with them because they tend not only to be fun people but also incredibly knowledgeable about their collection, museum, and area of expertise. Sadly, this trip was so time-constrained that I didn’t get much time at all for socializing. I had about five hours to get work done so I plunged on in!

Images, as always, can be clicked to emu-biggen them. Thanks to the NHMLA for access!

My initial look down the halls of the osteology storage. Rolling cabinets (on the right) are a typical sight.

My initial look down the halls of the osteology storage. Rolling cabinets (on the right) are a typical sight.

Freezers ahoy!

Freezers ahoy! With Batman watching over them.

A jar of bats? Why not? Batman approves.

A jar of bats? Why not? Batman approves.

The curator cleared a space on a table for me to set bones on. Then the anatomizing and photographing began!

The curator cleared a space on a table for me to set bones on. Then the anatomizing and photographing began!

On entering a museum collection, one quickly gets a sense of its “personality” and the culture of the museum itself, which emerges from the curator, the collection’s history, and the museum’s priorities. There are fun human touches like the ones in the photos below, interspersed between the stinking carcasses awaiting skeletonization, the crumbling bone specimens on tables that need repair or new ID tags, or the rows upon rows of coffee cups ready to fuel the staff’s labours.

Yet another reason why Darwin kicks ass.

Yet another reason why Darwin kicks ass. And fine curator-humour!

Ironic bird pic posted on the wall.

Ironic bird pic posted on the wall.

Below a typical wall-hanging of a bovid skull, an atypical display of a clutch of marshmallow peeps. Contest to see whether the mammalian or pseudo-avian specimens last longest?

Below a typical wall-hanging of a bovid skull, an atypical display of a clutch of marshmallow peeps. Contest to see whether the mammalian or pseudo-avian specimens last longest?

The NHMLA’s collection is a world-class one, which I why I chose it as the example for this post. When I entered the collection, I got that staggering sense of awe that I love feeling, to look down the halls of cabinets full of skeletonized specimens of birds and be overwhelmed by the vast scientific resource it represents, and the effort it has taken to create and maintain it. Imagine entering a library in which every book had the librarian’s hand in writing and printing it, and that those books’ contents were largely mysteries to humanity, only some of which you could investigate during your visit. Museum collections exist to fuel generations of scientific inquiry in this way. Their possibilities are endless. And that is why I love visiting them, because every trip is an adventure into the unknown– you do not know what you will find. Like these random encounters I had in the collection’s shelves:

Sectioned moa thigh bones, showing thick walls and spars of trabecular bone criss-crossing the marrow cavities.

Sectioned moa thigh bones, showing thick walls and spars of trabecular bone criss-crossing the marrow cavities.

My gut reaction was that this is a moa wishbone (furcula)- not often seen! It is definitely not a shoulder girdle (scapulocoracoid), which would be larger and more robust, and have a proper shoulder joint. It could, though, be a small odd rib, I suppose.

My gut reaction was that this is a moa wishbone (furcula)- not often seen! It is definitely not a shoulder girdle (scapulocoracoid), which would be larger and more robust, and have a proper shoulder joint. It could, though, be a small odd rib, I suppose. EDIT: Think again, John! See 1st comment below, and follow-ups. I seem to be totally wrong and the ID of scapulocoracoid is right.

A cigar box makes an excellent improvised container for moa toe bones- why not?

A cigar box makes an excellent improvised container for moa toe bones- why not?

Moa feet: all the moa to love!

Moa feet: all the moa to love!

May the skull of the magpie goose (Anseranas semipalmata) haunt your nightmares.

May the skull of the magpie goose (Anseranas semipalmata) haunt your nightmares.

Double-owie: headed shank (tibiotarsus) bone of a magpie goose (Anseranas semipalmata). No mystery why this guy died: vet staff at the zoo tried to fix a major bone fracture, and it had time to heal (frothy bone formation) but presumably succumbed to these injuries/infection.

Healed shank (tibiotarsus) bone of the same magpie goose as above. It had its own nightmares! No mystery why this guy died: vet staff at the zoo tried to fix a major bone fracture (bracing it with tubes and metal spars), and it had time to heal (see the frothy bone formation) but presumably succumbed to these injuries/infection.

Kiwi (Apteryx australis mantelli) hand, showing feather attachments and remnant of finger(s).

Kiwi (Apteryx australis mantelli) hand, showing feather attachments and remnant of finger(s).

Now that I’m in the collection shelves area, it brings me to this trip and my purpose for it! I wanted to look at some “basal birds” for our ongoing patella (kneecap) evolution project, to check which species (or individuals, such as juveniles/adults) have patellae. Every museum visit as a scientist is fundamentally about testing whether what you think you know about nature is correct or not. We’d published on how the patella evolved in birds, but mysteries remain about which species definitely had a patella or how it develops. Museum collections often have the depth and breath of individual variation and taxonomic coverage to be able to address such mysteries, and every museum collection has different strengths that can test those ideas in different, often surprising, ways. So I ventured off to see what the NHMLA would teach me.

Shelves full of boxes, begging to be opened- but unlike Pandora's box, they release joyous science!

Shelves full of boxes, begging to be opened- but unlike Pandora’s box, they release joyous science!

Boxes of kiwis, oh frabjous day! A nice sample size like this for a "rare" (to Northern hemispherites) bird is a pleasure to see.

Boxes of kiwis, oh frabjous day! A nice sample size like this for a “rare” (to Northern hemispherites) bird is a pleasure to see.

Well, in my blitz through this museum collection I didn’t see a single damn patella!

As that kneecap bone is infamously seldom preserved in nice clean museum specimens, this did not surprise me. So I took serendipity by the horns to check some of my ideas about how the limb joints in birds in general develop and evolve. One thing I’ve been educating myself about with my freezer specimens and with museum visits (plus the scientific literature) is how the ends (epiphyses) of the limb bones form in different species of land vertebrates (tetrapods). There are complex patterns linked with evolution, biomechanics and development that still need to be understood.

Left side view of the pelvis of a very mature, HUGE Casuarius casuarius (cassowary). The space between the ilium (upper flat bone) and ischium (elongate bone on middle right side) has begun to be closed by a mineralization of the membrane that spanned those bones in life. A side effect of maturity, most likely. But cool- I've never seen this in a ratite bird before, that I can recall.

Left side view of the pelvis of a very mature, HUGE Casuarius casuarius (cassowary). The space between the ilium (upper flat bone) and ischium (elongate bone on middle right side) has begun to be closed by a mineralization of the membrane that spanned those bones in life. A side effect of maturity, most likely. But cool- I’ve never seen this in a ratite bird before, that I can recall.

Hatchling ostrich thigh bones (femora), showing the un-ossified ends that in life would be occupied by thick cartilage.

Hatchling ostrich thigh bones (femora), showing the pitted, un-ossified ends that in life would be occupied by thick cartilage.

A more adult ostrich's femora, with more ossified ends and thinner cartilages.

A more adult ostrich’s femora, with more ossified ends and thinner cartilages.

Rhea pennata (Darwin's rhea) femora (thigh bones), left (top) one with major pathology on the knee end; overgrown bone. Owie!

Rhea pennata (Darwin’s rhea) femora; right (top) one with a major pathology on the knee end; overgrown bone (osteoarthritis?). Owie!

Also very-unfused knee joints of a Darwin's rhea. Cool Y-shape!

Also very-unfused knee joints of a Darwin’s rhea hatchling. Cool Y-shape!

In birds, most of the bones don’t have anything that truly could be called an epiphysis– the bone ends are capped with thick cartilage that only gradually becomes bone as the birds get older, and even old-ish birds can still have a lot of cartilage (see photos above)– no “secondary centre” (true epiphysis) of bone mineralization ever forms inside that cartilage. However, there are two curious apparent exceptions to this absence of true epiphyses in avian limbs:

(1) in the knee joint, something like an epiphysis forms on the upper end of the tibia (shank bone) and fuses during growth (shown below). Sometimes that unfused epiphysis is confused with a patella, as our recent paper discussed; in any case, where that “epiphysis” came from in avian evolution is unclear. But also:

(2) in the ankle joint, several bones on both sides (shank and foot) of the joint fuse to the long-bones of the limbs, acting like epiphyses. It is well documented by the fossil record of non-avian and avian dinosaurs that these were the tarsals: at least five different bones (astragalus, calcaneum and distal tarsals) were individual bones for millions of years in various dinosaurs, then these all fused to form the “epiphyses” of the shank and foot, eventually completing this gradual fusion within the bird lineage. Modern birds obliterate the boundaries between these five or more bones as they grow.

These are worthwhile questions to pursue because they show us (1) how odd, little-explored features of the avian skeleton came to be; and (2) potentially more generally why limb bones develop the many ways they do in vertebrates, and how they might develop incorrectly — or heal if damaged.

Images below from the NHMLA collections show how this is the case. Fortunately(?) for me, they supported how I thought the “epiphyses” of avian limbs develop/evolved; there were no big surprises. But I still learned neat details about how this happens in individual species or lineages, especially for the knee joint.

Juvenile kiwi's shank (tibiotarsus) bones viewed from the top (proximal) ends, showing the bubbly nubbins of bone (very bottom of each bone image) that are the "cranial tibial epiphyses" often mistaken for patellae.

Juvenile kiwi’s shank (tibiotarsus) bones viewed from the top (proximal) ends, showing the bubbly nubbins of bone (very bottom of each bone image; lighter region) that are the “cranial tibial epiphyses” often mistaken for patellae.

Subadult kiwi's tibiotarsi in same view as above, showing the epiphyses fusing onto the tibiae.

Subadult kiwi’s tibiotarsi in same view as above, showing the smooth triangular epiphyses fusing onto the tibiae.

Adult kiwi's tibiotarsi (sorry, blurry photo) in which all fusion is complete.

Adult kiwi’s tibiotarsi (sorry, blurry photo) in which all fusion is complete.

Looking down at the top/ankle end of the tarsometatarsal (sole) bones in a hatchling ostrich: the three bones are separate and hollow, where "cartilage cones" would have filled them in.

Looking down at the top/ankle end of the tarsometatarsal (sole) bones in a hatchling ostrich: the three bones are separate and hollow, where “cartilage cones” would have filled them in. The left and right bones have different amounts of ossification; not unusual in such a young bird.

Ossified tendons (little spurs of long, thin bone) on the soles of the feet (tarsometatarsal bones) of a brush-turkey (Alectura lathami)- seldom described in this unusual galliform bird or its close relatives, and thus nice to see. These would be parts of the toe-flexor tendons.

Ossified tendons (little spurs of long, thin bone) on the soles of the feet (tarsometatarsal bones) of a brush-turkey (Alectura lathami)- seldom described in this unusual galliform bird or its close relatives, and thus nice to see. These would be parts of the toe-flexor tendons. Another nice thing about these two tarsometatarsus specimens is that their fusion is basically complete- each is one single bone unit, as in normal adult birds, rather than five or more.

My visit to the NHMLA bird bone collection was a lot of fun, because I got to do what I love: opening box after box of bone specimens, with bated breath wondering what would be inside. In this case, familiarity was inside, but my knowledge of avian bone development and evolution still improved. I got to look at a lot of ostriches, rheas, cassowaries and kiwis, more than I’d seen in one museum before, and that broadened my sample of young, juvenile and adult animals that I’d seen for these species. Their knees and ankles all grew in grossly similar ways, supporting this assumption in my prior work and building my confidence in published ideas. It’s always good to check such things. Each box opened takes some careful observation and cross-checking against all the facts and ideas swirling around in your head. You take notes, scale photos, measurements, do comparisons between specimens, and just explore; letting your curiosity run unleashed as you assemble knowledge, Tetris-like, in your mind.

And I had a lot of fun because a museum collection visit is like swimming in anatomy. You’re surrounded by more specimens than you could ever fully comprehend. Sometimes you run across an odd specimen whose anatomy tells you something about its life, like pathologies such as the terrible fractured magpie goose leg shown above. Or you see some curatorial touch that makes you chuckle at an apparent inside joke or mutter respect for their careful organization in tending their charges. That feeling of pulling open a museum drawer or box lid and peering inside is like few others in science — there might be disappointment inside (e.g. “Crap, that specimen sucks!”), boredom (“Oh. Another one of these!?”) or the joy of discovery (“Holy *@$£, I’ve never seen that before!”). My first scientific publication (in 1998) came from rummaging through the UCMP museum collections as a grad student and spotting an obscure pelvic bone that turned out to be highly diagnostic for the equally obscure clade of bird-like dinosaurs called alvarezsaurids. I happened to open that drawer with the alvarezsaurid specimen at the right time, shortly after the first ever specimen of that dinosaur had been described in the literature (~1994). Before then, no one could have identified what that bone was!

There is time for hours of quiet introspection during museum collection studies, immersed in this wealth of anatomical resources and isolated in a silent, climate-controlled tomb-like hall. It is relaxing and overwhelming at the same time. Especially in my case with just five hours to survey numerous species, you have to budget your time and think efficiently. It’s a unique challenge to explore a museum collection as a researcher. If you don’t learn something — especially in a good museum collection — you’re doing it wrong. In this time of tight finances and trends to close museums or stow away precious collections, it is important to vocally celebrate what a vast treasure museum collections are, and how the people that maintain them are vital stewards of those treasures.

I set the cat amongst the pigeons by also visiting the Page Museum at the La Brea Tar Pits in LA, to study fossil cats-- like this American lion (Panthera atrox) code-named "Fluffy", that we CT scanned during my LA visit-- more about that later!

I set the cat amongst the pigeons by also visiting the Page Museum at the La Brea Tar Pits in LA, to study fossil cats– like this American lion (Panthera atrox), code-named “Fluffy”, that we CT scanned during my LA visit– more about that later!

EDIT: I hurried this post off during my free time today, and still feel I didn’t fully capture the deep, complex feelings I have regarding museum collections and the delight I get from studying them. Other freezerinos, please add your thoughts in the Comments below!

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