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Posts Tagged ‘dissection’

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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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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Deck the ‘Nets With PeerJ Papers— please sing along!

♬Deck the ‘nets with PeerJ papers,
Fa la la la la, la la la la.
‘Tis the day to show our labours,
Fa la la la la, la la la la.

Downloads free; CC-BY license,
Fa la la, la la la, la la la.
Read the extant ratite science,
Fa la la la la, la la la la.

See the emu legs before you
Fa la la la la, la la la la.
Muscles allometric’ly grew.
Fa la la la la, la la la la.

Follow the evolvin’ kneecaps
Fa la la la la, la la la la.
While we dish out ratite recaps 
Fa la la la la, la la la la.

Soon ostrich patellar printing
Fa la la la la, la la la la.
Hail anat’my, don’t be squinting
Fa la la la la, la la la la.

Dissections done all together
Fa la la la la, la la la la.
Heedless of the flying feathers,
Fa la la la la, la la la la♪

(alternate rockin’ instrumental version)

Stomach-Churning Rating: 5/10: cheesy songs vs. fatty chunks of tissue; there are no better Crimbo treats!

Today is a special day for palaeognath publications, principally pertaining to the plethora of published PeerJ papers (well, three of them anyway) released today, featuring my team’s research! An early Crimbo comes this year in the form of three related studies of hind limb anatomy, development, evolution and biomechanics in those flightless feathered freaks of evolutionary whimsy, the ratites! And since the papers are all published online in PeerJ (gold open access), they are free for anyone with internet access to download and use with due credit. These papers include some stunning images of morphology and histology, evolutionary diagrams, and a special treat to be revealed below. Here I’ll summarize the papers we have written together (with thanks to Leverhulme Trust funding!):

1) Lamas, L., Main, R.P., Hutchinson, J.R. 2014. Ontogenetic scaling patterns and functional anatomy of the pelvic limb musculature in emus (Dromaius novaehollandiae). PeerJ 2:e716 http://dx.doi.org/10.7717/peerj.716 

My final year PhD student and “emu whisperer” Luis Lamas has published his first paper with co-supervisor Russ Main and I. Our paper beautifully illustrates the gross anatomy of the leg muscles of emus, and then uses exhaustive measurements (about 6524 of them, all done manually!) of muscle architecture (masses, lengths, etc.) to show how each of the 34 muscles and their tendons grew across a more than tenfold range of body mass (from 6 weeks to 18 months of age). We learned that these muscles get relatively, not just absolutely, larger as emus grow, and their force-generating ability increases almost as strongly, whereas their tendons tend to grow less quickly. As a result, baby emus have only about 22% of their body mass as leg muscles, vs. about 30% in adults. However, baby emus still are extremely athletic, more so than adults and perhaps even “overbuilt” in some ways.

This pattern of rapidly growing, enlarged leg muscles seems to be a general, ancestral pattern for living bird species, reflecting the precocial (more independent, less nest-bound), cursorial (long-legged, running-adapted) natural history and anatomy, considering other studies of ostriches, rheas, chickens and other species close to the root of the avian family tree. But because emus, like other ratites, invest more of their body mass into leg muscles, they can carry out this precocial growth strategy to a greater extreme than flying birds, trading flight prowess away for enhanced running ability. This paper adds another important dataset to the oft-neglected area of “ontogenetic scaling” of the musculoskeletal system, or how the locomotor apparatus adapts to size-/age-related functional/developmental demands as it grows. Luis did a huge amount of work for this paper, leading arduous dissections and analysis of a complex dataset.

Superficial layer of leg muscles in an emu, in right side view.

Superficial layer of leg muscles in an emu, in right side view. Click any image here to emu-biggen. The ILPO and IC are like human rectus femoris (“quads”); ILFB like our biceps femoris (“hams”); FL, GM and GL much like our fibularis longus and gastrocnemius (calf) muscles, but much much bigger! Or, perhaps FL stands for fa la la la la?

Data for an extra set of emus studied by coauthor Russ Main in the USA, which grew their muscles similarly to our UK group. The exponents (y-axis) show how much more strongly the muscles grown than isometry (maintaining the same relative size), which is the dotted line at 1.0.

Data for an extra set of emus studied by coauthor Russ Main in the USA, which grew their muscles similarly to our UK group. The exponents (y-axis) show how much more strongly the muscles grew than isometry (maintaining the same relative size), which is the dotted line at 1. The numbers above each data point are the # of individuals measured. Muscle names are partly above; the rest are in the paper. If you want to know them, we might have been separated at birth!

2) Regnault, S., Pitsillides, A.A., Hutchinson, J.R. 2014. Structure, ontogeny and evolution of the patellar tendon in emus (Dromaius novaehollandiae) and other palaeognath birds. PeerJ 2:e711 http://dx.doi.org/10.7717/peerj.711

My second year PhD student Sophie Regnault (guest-blogger here before with her rhino feet post) has released her first PhD paper, on the evolution of kneecaps (patellae) in birds, with a focus on the strangeness of the region that should contain the patella in emus. This is a great new collaboration combining her expertise in all aspects of the research with coauthor Prof. Andy Pitsillides‘s on tissue histology and mine on evolution and morphology. This work stems from my own research fellowship on the evolution of the patella in birds, but Sophie has taken it in a bold new direction. First, we realized that emus don’t have a patella– they just keep that region of the knee extensor (~human quadriceps muscle) tendon as a fatty, fibrous tissue throughout growth, showing no signs of forming a bony patella like other birds do. This still blows my mind! Why they do this, we can only speculate meekly about so far. Then, we surveyed other ratites and related birds to see just how unusual the condition in emus was. We discovered, by mapping the form of the patella across an avian family tree, that this fatty tendon seems to be a thing that some ratites (emus, cassowaries and probably the extinct giant moas) do, whereas ostriches go the opposite direction and develop a giant double-boned kneecap in each knee (see below), whereas some other relatives like tinamous and kiwis develop a more “normal”, simple flake-like bit of bone, which is likely the state that the most recent common ancestor of all living birds had.

There’s a lot in this paper for anatomists, biomechanists, palaeontologists, ornithologists, evo-devo folks and more… plenty of food for thought. The paper hearkens back to my 2002 study of the evolution of leg tendons in tetrapods on the lineage that led to birds. In that study I sort of punted on the question of how a patella evolved in birds, because I didn’t quite understand that wonderful little sesamoid bone. And now, 12 years later, we do understand it, at least within the deepest branches of living birds. What happened further up the tree, in later branches, remains a big open subject. It’s clear there were some remarkable changes, such as enormous patellae in diving birds (which the Cretaceous Hesperornis did to an extreme) or losses in other birds (e.g., by some accounts, puffins… I am skeptical)– but curiously, patellae that are not lost in some other birds that you might expect (e.g., the very non-leggy hummingbirds).

Fatty knee extensor tendon of emus, lacking a patella. The fatty tissue is split into superficial (Sup) and deep regions, with a pad corresponding to the fat pad in other birds continuous with it and the knee joint meniscus (cushioning pad). The triceps femoris (knee extensor) muscle group inserts right into the fatty tendon, continuing over it. A is a schematic; B is a dissection.

Fatty knee extensor tendon of an emu, showing the absence of a patella. The fatty tissue is split into superficial (Sup) and deep regions, with a pad corresponding to the fat pad in other birds continuous with it and the knee joint meniscus (cushioning pad). The triceps femoris (knee extensor) muscle group inserts right into the fatty tendon, continuing on over it. A is a schematic; B is a dissection.

Sectioning of a Southern Cassowary's knee extensor tendon, showing: A Similar section  as in the emu image above. revealing similar regions and fibrous tissue (arrow), with no patella, just fat; and B, with collagen fibre bundles (col), fat cells (a), and cartilage-like tissue (open arrows) labelled.

Sectioning of a Southern Cassowary’s knee extensor tendon, showing: A, Similar section as in the emu image above. revealing similar regions and fibrous tissue (arrow), with no patella, just fat; and B, With collagen fibre bundles (col), fat cells (a), and cartilage-like tissue (open arrows) labelled.

Evolution of patellar form in birds. White branches indicate no patella, blue is a small flake of bone for a patella, green is something bigger, yellow is a double-patella in ostriches, and grey is uncertain. Note the uncertainty and convergent evolution of the patella in ratite birds, which is remarkable but fits well with their likely convergent evolution of flightlessness and running adaptations.

Evolution of patellar form in birds. White branches indicate no patella, blue is a small flake of bone for a patella, green is something bigger, yellow is a double-patella in ostriches, black is a gigantic spar of bone in extinct Hesperornis and relatives, and grey is uncertain. Note the uncertainty and convergent evolution of the patella in ratite birds (Struthio down to Apteryx), which is remarkable but fits well with their likely convergent evolution of flightlessness and running adaptations.

3) Chadwick, K.P., Regnault, S., Allen, V., Hutchinson, J.R. 2014. Three-dimensional anatomy of the ostrich (Struthio camelus) knee joint. PeerJ 2:e706 http://dx.doi.org/10.7717/peerj.706

Finally, Kyle Chadwick came from the USA to do a technician post and also part-time Masters degree with me on our sesamoid grant, and proved himself so apt at research that he published a paper just ~3 months into that work! Vivian Allen (now a postdoc on our sesamoid bone grant) joined us in this work, along with Sophie Regnault. We conceived of this paper as fulfilling a need to explain how the major tissues of the knee joint in ostriches, which surround the double-patella noted above, all relate to each other and especially to the patellae. We CT and MRI scanned several ostrich knees and Kyle made a 3D model of a representative subject’s anatomy, which agrees well with the scattered reports of ostrich knee/patellar morphology in the literature but clarifies the complex relationships of all the key organs for the first time.

This ostrich knee model also takes Kyle on an important first step in his Masters research, which is analyzing how this morphology would interact with the potential loads on the patellae. Sesamoid bones like the patella are famously responsive to mechanical loads, so by studying this interaction in ostrich knees, along with other studies of various species with and without patellae, we hope to use to understand why some species evolved patellae (some birds, mammals and lizards; multiple times) and why some never did (most other species, including amphibians, turtles, crocodiles and dinosaurs). And, excitingly for those of you paying attention, this paper includes links to STL format 3D graphics so you can print your own ostrich knees, and a 3D pdf so you can interactively inspect the anatomy yourself!

(A) X-ray of an ostrich knee in side view, and (B) labelled schematic of the same.

Ostrich knee in side view: A, X-ray, and (B) labelled schematic.

3D model of an ostrich knee, showing: A, view looking down onto the top of the tibia (shank), with the major collateral ligaments (CL), and B, view looking straight at the front of the knee joint, with major organs of interest near the patella, sans muscles.

3D model of an ostrich knee, showing: A, View looking down onto the top of the tibia (shank), with the major collateral ligaments (CL), and B, View looking straight at the front of the knee joint, with major organs of interest near the patella, sans muscles.

You can view all the peer review history of the papers if you want, and that prompts me to comment that, as usual at PeerJ (full disclosure: I’m an associate editor but that brings me £0 conflict of interest), the peer review quality was as rigorous at a typical specialist journal, and faster reviewing+editing+production than any other journal I’ve experienced. Publishing there truly is fun!

Merry Christmas and Happy Holidays — and good Ratite-tidings to all!

And stay tuned- the New Year will bring at least three more papers from us on this subject of ratite locomotion and musculoskeletal anatomy!

♬Should auld palaeognathans be forgot, 
And never brought for scans? 
Should publications be soon sought, 
For auld ratite fans!♪

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It has been a long time since we had some Mystery Anatomy fun here, so I am cutting loose with a double-barrelled blast of images– dive for cover!

I’m also giving out a Crimbo present as a bigger post, on a special day coming soon, count on that. This is just an advent snack.

Stomach-Churning Rating: 2/10 and 7/10: digital body and glistening, snotty.

Mystery Anatomy 2014same rules as before; remember that the scoreboard has been reset.

Identify (1) the animal shown in the four-panel top images (CT scan/reconstruction), and (2) the DIFFERENT animal (and/or the main central, pink structure) shown in the big, gooey bottom image (Dissection). No special rules. Potential for double points!

And someone will get these, I am sure. This might be the final round of 2014’s Mystery Anatomy game.

Difficulty: Plenty.

Mystery CT 14

Mystery CT 14

Mystery Anatomy 15

Mystery Anatomy 15

Go forth!

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I’ve described our “Walking the Cat Back” Leverhulme Trust-funded project with Dr. Anjali Goswami and colleagues before, but today we really got stuck into it. We’re dissecting a 46kg male Snow Leopard (Panthera uncia) as the first “data point” (actually several hundred data points, but anyway, first individual) in our study of how limb and back muscles change with size in felids. No April Fools’ pranks here; real science-as-it-happens.

Stomach-Churning Rating: 7/10 for skinned leopard and globs of fat. Much worse in person, hence the downgrading from what could be a higher score. Don’t click the photos to emkitten them if you don’t want to see the details.

This leopard is the same one that Veterinary Forensics blogged about. It died in a UK cat conservation/recovery centre. Today is simply a short post, but it is the first in what will surely be a continued series of posts on felid postcranial anatomy and musculoskeletal biomechanics by our felid research team, with bits of natural history and evolution thrown in when we can manage. As befits one of my curt “Anatomy Vignette” posts, pictures will tell the story.

Skinned and mostly de-fatted snow leopard, with fat piled up on the lower left hand corner near the hind feet. Here we are identifying and then removing and measuring the individual muscles. Project postdoc Andrew Cuff is hard at work on the forelimb while I'm mucking around with the hindlimb.

Skinned and mostly de-fatted snow leopard, with fat piled up on the lower left hand corner near the hind feet. Here we are identifying and then removing and measuring the individual muscles. Project postdoc Andrew Cuff is hard at work on the forelimb while I’m mucking around with the hindlimb. The fat here is about 3kg subcutaneous fat, so around 6.5% of body mass. And as the cat has been around for a while, that fat has gone a bit rancid and that is not nice. Not nice at all, no… Usually smells do not bother me, but this took some adjustment. Fortunately, the muscles are still OK, and work is coming along well.

UCL PhD student Marcela Randau,, carving up our cat's limb muscles. As usual in comparative biomechanics, we measure the "architecture"- parameters of the muscle that relate in a somewhat straightforward fashion to function.

UCL PhD student Marcela Randau, carving up our cat’s limb muscles. As usual in comparative biomechanics, we measure the “architecture”- parameters of the muscle that relate in a somewhat straightforward fashion to function. This muscular architecture includes things like muscle mass, the lengths of the fibers (fascicles) that make up the muscles, and the angle of the fascicles to the muscle’s line of action. These parameters correlate reasonably well with the force and power that the muscle can develop, and its working range of length change. Other posts here have discussed this more, but by measuring the architecture of many muscles in many felids of different sizes, we can determine how felids large and small adapt their anatomy to support their bodies and move their limbs. This will help to solve some lingering mysteries about the odd ways that cats move and how their movement changes with body size.

This research is being driven forward mainly by Andrew and Marcela, shown above, so I wanted to introduce them and our odoriferous fat cat. Upcoming dissections: 1-2 more snow leopards, tiger, various lions, ocelot, black-footed cat, leopard, and a bunch of moggies, and whatever else comes our way. All were EU zoo/park mortalities (there are a LOT of big cats out there!).

EDIT: Had to add a photo of the CLAWS! Whoa dude.

CLAWS

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(John: here’s a guest post from my former PhD student, soon to be 100% legit PhD, Dr., and all that jazz, Julia Molnar!)

This is my first guest post, but I have been avidly following what’s in John’s freezer (and the blog too) for quite a while. I joined the lab in 2009 and left a month ago on the bittersweet occasion of surviving my PhD viva (oral exam/defense), so I’d like to take a moment here to thank John and the Structure & Motion Lab for a great 4 years!

Moving on to freezer-related matters; specifically, a bunch of frozen crocodile spines. It was late 2011, and the reason for the spines in John’s freezer was that John, Stephanie Pierce, and I were trying to find out more about crocodile locomotion. This was anticipated to become my first major, first-author research publication (but see my Palaeontologia Electronica paper on a related subject), and I was about to find out that these things seldom go as planned; for example, the article would not be published for more than three years (the research took a long time!). Before telling the story of how it lurched and stumbled toward eventual publication, I’ll give you some background on the project.

Stomach-Churning Rating: 3/10; x-ray of dead bits and nothing much worse.


A stumbly sort-of-bounding crocodile. They can do better.

First of all, why crocodiles? For one thing, they’re large, semi-terrestrial animals, but they use more sprawling postures than typical mammals. Along with alligators and gharials, they are the only living representatives of Crocodylomorpha, a 200+ million year-old lineage that includes wolf-like terrestrial carnivores, fish-like giants with flippers and a tail fin, even armored armadillo-like burrowers. Finally, crocodiles are interesting in their own right because they use a wide variety of gaits, including bounding and galloping, which are otherwise known only in mammals.

Nile croc

Nile crocodile skeletal anatomy

OK, so why spines? Understanding how the vertebral column works is crucial to understanding locomotion and body support on land, and inter-vertebral joint stiffness (how much the joints of the backbone resist forces that would move them in certain directions) in particular has been linked to trunk movements in other animals. For this reason, vertebral morphology is often used to infer functional information about extinct animals, including dinosaurs. However, vertebral form-function relationships have seldom been experimentally tested, and tests on non-mammals are particularly scarce. So we thought the crocodile spines might be able to tell us more about the relationship between vertebral morphology, mechanics, and locomotion in a broader sample of vertebrate animals. If crocodile spine morphology could be used to predict joint stiffness, then morphological measurements of extinct crocodile relatives would have some more empirical heft to them. Several skeletal features seem to play roles such as levers to mechanically stiffen crocodile spines (click to emcroc’en):

Croc vertebra-01

Anatomy of a crocodile vertebra

We decided to use a very simple technique that could be replicated in any lab to measure passive stiffness in crocodile cadavers. We dissected out individual joints were and loaded with known weights. From the movement of the vertebrae and the distance from the joint, we calculated how much force takes to move the joint a certain number of degrees (i.e. stiffness).

Julia w vertebra (480x640)

Me with crocodile vertebra and G-clamp

Xray

X-ray of two crocodile vertebrae loaded with a metric weight to calculate their joint’s stiffness

Afterwards, we boiled the joints to remove the soft tissues – the smell was indescribable! We took 14 measurements from each vertebra. All of these measurements had been associated with stiffness or range of motion in other studies, so we thought they might be correlated with stiffness in crocodiles also.

morphometrics

Some of the vertebral measurements that were related to stiffness

Despite my efforts to keep it simple, the process of data collection and analysis was anything but. I recall and exchange with Stephanie Pierce that went something like this:

Stephanie: “How’s it going?”

Me: “Well, the data are messy, I’m not seeing the trends I expected, and everything’s taking twice as long as it was supposed to.”

Stephanie: “Yes, that sounds like science.”

That was the biggest lesson for me: going into the project, I had been unprepared for the amount of bumbling around and re-thinking of methods when the results were coming up implausible or surprising. In this case there were a couple of cool surprises: for one thing, crocodiles turn out to have a very different pattern of inter-vertebral joint stiffness than typical mammals: while mammals have stiff thoracic joints and mobile lumbar joints, crocodiles have stiffer lumbar joints. Many mammals use large lumbar movements during bounding and galloping, so crocodiles must use different axial mechanics than mammals, even during similar gaits. While that’s not shocking (they did evolve their galloping and bounding gaits, and associated anatomy, totally independently), it is neat that this result came out so clearly. Another unexpected result was that, although several of our vertebral measurements were correlated with stiffness, some of the best predictors of stiffness in mammals from previous studies were not correlated with stiffness in crocodiles. The study tells a cautionary tale about making assumptions about extinct animals using data from only a subset of their living relatives or intuitive ideas about form and function.

Finally, the experience of doing the experiments and writing the paper got me interested in other aspects of crocodilian functional anatomy. For instance, how does joint stiffness interact with other factors, such as muscle activity and properties of the ribs, skin, and armor in living crocodiles? Previous studies by Frey and Salisbury had commented on this, but the influence of those factors is less tractable to experiment on or model than just naked backbones with passively stiff joints. In the future, I’d like to study vertebral movements during locomotion in crocodiles – especially during bounding and galloping – to find out how these patterns of stiffness relate to movement. In the meantime, our study shows that, to a degree, crocodile backbone dimensions do give some clues about joint stiffness and locomotor function.

To find out more, read the paper! It was just featured in Inside JEB.

Julia Molnar, Stephanie Pierce, John Hutchinson (2014). An experimental and morphometric test of the relationship between vertebral morphology and joint stiffness in Nile crocodiles (Crocodylus niloticus). The Journal of Experimental Biology 217, 757-768 link here and journal’s “Inside JEB” story

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I Can’t Remember Freezermas…
Can’t Tell Dissection from a CT.
Deep down Inside I Feel to Freeze.
These Wonderful Scenes of Anatomy!
Now That the Week Is Through with Me,
I’m Waking up; Ratites I see
And There’s Not Much Left of These:
Nothing remains but bones now

(digested from Metallica’s “One“, in …And Justice For All, the pummeling, slickly produced, huge-sounding, Jason Newsted-bass-playing leviathan of a thematic album (1988). It was all downhill for Metallica after this one, but it was a good year for rock! The song is about a soldier who had traumatic injuries and was left paralyzed, “locked-in” to his own mind. Themes/footage from “Johnny Got His Gun” (1939 book/1971 movie) are interspersed. Did you see this track coming? If so, you’re just as demented as I am; congrats!)

And so another year ends; we’re at the final post of Freezermas 2014: The Concept Album. We had 7 tracks involving leitmotifs of ostriches and cats and 2 vs. 4 legs, and CTs and x-rays, and epic dissections, and disturbing pathologies, and some twisted lyrics that mangled classic albums. There are so many more concept albums I could have touched on- great ones by Rush, Yes, Savatage, Helstar, Mastodon… many more. But I’ll give you a chance to sit in the DJ’s seat in this post!

Stomach-Churning Rating: 6/10. Some internal organs.

Today’s one mystery dissection photo is of two things, and the Mystery Anatomy challenge is to identify both (the 2-part brown thing and the 1-part whitish thing). They are from our friend the ostrich.

Your task is to weave your answer into the lyrics of a song from any concept album (2 lines or more)– you must identify the song, artist and album with your answer so we can figure out the tune. Any genre is OK as long as it is clearly a concept album (music, that is). You have freedom. Use it wisely! As always, bonus points for extra cleverness.

Whazzat?

We’ll let Maytagtallica sing us out:

♫Hold my breath as I wait for points
Oh Please John, blog more?♫

no

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