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Evolutionary Biomechanics of Dinosaur Legs

March 19, 2021 by John of the Freezers

The blog is back! Briefly. With dinosaurs. Back in 2005, I published a paper in which I used a “SIMM” 3D musculoskeletal biomechanical model of Tyrannosaurus rex to analyse its muscle actions and infer a relatively upright hindlimb pose. This was an outcome from my NSF-funded postdoctoral research at Stanford University, in which engineers kindly taught me how to use SIMM (handing me a loaded gun?). Part of my plan all along was to build multiple such models along a rough evolutionary sequence to revisit old questions I had with past, qualitative functional morphology papers from 2000 onwards, and see if biomechanics could quantitatively reveal more about the functional evolution of dinosaur hindlimb muscles. So I got data for modelling some extinct dinosaurs (theropods Dilophosaurus, Allosaurus, Velociraptor) and living birds (Struthio, others) and published nuggets of that but held others back…

Stomach-Churning Rating: -1/10; dinosaurs!

I handed these 3D model data off to my PhD student Vivian Allen in ~2007, charging him with the task of making more models to flesh out the phylogeny and finish what I’d started. And he sure did. He graduated, did a couple of postdocs with me, and we gradually massaged his thesis chapter on this topic into a draft paper. Easier said than done, though! That’s why 14 more years have passed.

Viv came up with some clever tools in MATLAB software code (from which he became a very competent programmer and went on to a successful career in that!) to boil complex data on muscle leverages (moment arms) across a wide range of joint motion for the hindlimbs for each taxon.

These data then were fed into further code that took the results from all models, ultimately 13 of them from an Australian freshwater crocodile to two living birds and 10 extinct dinosaurs plus close cousin Mara/Lagosuchus (Figure 1). The code expressed these leverages as changes in ancestral values along the main branch of the evolutionary tree from early (Triassic) “ruling reptile” Archosauria (represented here just by the croc as a proxy) to modern birds, and 9 main ancestral “nodes” in between. Our code tracked both how each of 35 hindlimb muscles we modelled evolved in its leverage, as well as overall “average” leverage of functional groups around the hip, knee and ankle joints.

So, back and forth we went for some 10 years playing with the models (see Video below), data and code, and the paper describing the whole thing, slowly closing in on a final version but also sometimes distracted by our other projects and Real Life Stuff like health and children, and concerns about how we conducted this study (i.e. a lot of fiddling).

Figure 1: Evolutionary tree of dinosaurs and their relatives as used in the study, showing all 13 models, species names, and names of groups along the bottom (red nodes) of the tree. Averostra and Avetheropoda were ancestral groups of theropod dinosaurs that the study inferred had particular specialisations of the hindlimb muscles. Right hindlimbs in side view. The limbs are all straightened vertically into a baseline reference posture but the study investigated variation in muscle function across a wide range of limb poses.

Then I got a new grant “DAWNDINOS” that changed the scene for me, refocusing my team’s energies onto the Triassic (and early Jurassic) and the evolutionary biomechanics of diverse archosaurs’ locomotion, assessed with both LOTS of experimental studies of living crocs and birds, and LOTS of predictive simulations of locomotion. Stay tuned for much more on that from our team, but we’ve already published some key steps here. Most notably, we developed an improved protocol for modelling and simulating our animals, as shown by Bishop et al.’s 2021 study of the early theropod Coelophysis bauri (also appearing in the current paper). Awkwardly for me, that new method rendered our old models and methods a bit obsolete (although still fine), so I pushed to publish this current paper with Viv, and brought collaborator Dr. Brandon Kilbourne on board to aid in some final stats, figures and more. That finally did it, and now we’ve published the paper in Science Advances. Deep breath.

Video: Rotating movies of 3 musculoskeletal models from this study. Models have been posed into representative limb orientations illustrating a gradual or stepwise transformation from more upright to more crouched.

Well what’s the paper about, then? We used our 13 models and processed evolutionary functional patterns to test three main questions (hypotheses) about muscle leverage, making educated guesses at what might prevail from early Archosauria to Aves:

  1. Hip extensor / flexor (i.e. femur retractor/protractor) moment arm ratios remained constant. We weren’t sure what to expect, as these antagonists both seem to change a lot on the whole lineage, so we went with this prediction.
  2. Knee flexor / extensor ratios decreased; i.e. the flexors (“hamstrings” etc.) weakened and/or extensors (equivalent of our quadriceps) strengthened their leverage. Anatomy of the knee joint and muscles around it suggests this, plus since Gatesy’s 1990-onwards studies we’ve expected archosaurs to shift from more ‘hip-based’ to more ‘knee-based’ locomotion as we get closer to avian ancestry.
  3. Hip medial (internal) long-axis rotator / abductor (i.e. pronators of the limb vs. those that draw the leg away from the body) ratios increased. This idea comes right from my paper w/Gatesy in 2000, where we surmised that archosaurs shifted from relying on hip adductors (in crocs/other quadrupeds) to abductors (in bipedal dinosaurs; like humans) to medial rotators (‘torsional control’ as in birds today) during weight support.

Moreover, we reconstructed the evolution of 35 muscles’ actions across ~250 million years, which was a new step.

Here’s a summary of what we found (Figure 2):

Figure 2: Short visualization/explanation of the study’s main insights. Pictures by palaeoartist Jaime Headden: https://qilong.wordpress.com/about/ in left side view, including “muscled” and silhouette images. Right side images include representative hip, knee and ankle muscles from the study. Changes such as the enlargement of muscles in front of the hip that straighten the knee, and reduction of the caudofemoralis longus muscle that runs from the tail to the back of the thigh, are evident.

So, overall hypothesis 1 about hip extensors/flexors ended up complicated; rejected because hip flexor leverage actually increased. Furthermore, we found that around the ancestral nodes for early theropod dinosaurs (Neotheropda through Avetheropoda; around 200 Mya), there were peaks in muscle leverage (size-normalized) that surprised us, and persisted despite many different analyses we threw at them over the years. As far as we could tell, these peaks that kept appearing for various muscles’ actions were “real” (estimates). Which meant these ancestors may have had specialised high leverage relative to both their own ancestors and descendants; the peaks got reversed in evolution. These ancestors had some other weird anatomical and functional traits, such as tightly articulated hip joints early on (which they lost later), increased body size in the later forms, more ‘macropredatory’ ecology (e.g. eating sauropods?), and a centre of mass of the body that was shifted forwards (due to big arms and heads/necks). This weirdness is a cool unexpected finding that showed up for the other hypotheses too, and it needs some more investigating. A ‘failed’ hypothesis test led to neat insights.

Figure 3. From the paper– showing our main results for changes in moment arm ratios across archosaurian ancestors. Hip extensors/flexors decreased then increased; knee flexors/extensors decreased; and hip medial rotators/abductors decreased then had a series of increases.

Hypotheses 2 and 3 found good support, on the contrary, overall (Figure 3). We seem to have been able to quantify the shifts from hip-based to knee-based, and abductor-based to medial-rotator-based, muscle actions. I find that very satisfying. Ankle weight support (extension) capacity also increased, which fits morphological changes fairly well. If you’re into archosaur limb muscle form and function, there’s a lot more food for thought in the paper.

Funnily enough, ~20 years has been sufficient time that we could have had plenty more models in this study if we’d delayed it even longer and re-re-re-analysed our data. But we had to draw the line somewhere and not infinitely revise with every new model we’ve been creating. With the current state of musculoskeletal modelling in my group, we could have more than doubled our sample size and fleshed out the most important gaps such as in the crocodile-lineage (extinct Pseudosuchia) and other Triassic forms plus elsewhere. A big challenge remains having some nice 3D-preserved early fossil birds beyond Archaeopteryx; e.g. so many nice Chinese ones are too flat (e.g. joints we need) to reliably model here. It’s something that can still be done and is worth doing, but I suspect the general trends we’ve found along the dinosaur lineage are “correct”.

What’s personally important to me about this paper is (1) how it not only bridges a huge morphofunctional gap across archosaur evolution in scientific terms, and (2) how we’ve completed a long-delayed project with stubbornness (and during a pandemic!), but also (3) how it bridges my past career from my PhD and postdoc to the present work with DAWNDINOS. We’re now forging well beyond what this new paper has done in terms of truly testing, as best we can (estimate) so far, how limb muscles of archosaurs functioned and evolved, and how these contributed to particular behaviours and performance (maybe even palaeoecology and evolutionary success/extinction?). The current paper is just simple modelling of muscle leverage, but leverage is only one (very important!) piece of muscle function and performance. With fully dynamic, anatomically integrative, physiologically and physically representative biomechanical computer simulations that predict what living and extinct archosaurs could or could not do, we can do even better. So watch for that! Hopefully it won’t all take 20 years, or 250 million.

Posted in Better Know A Muscle, Biomechanics, Exalting Archosauria, Freezermas | Tagged , , , , , | 4 Comments »

Guest Post: The Strangest-Looking Animals of All Time

September 22, 2020 by John of the Freezers

Our special guest post this week comes from Dr. Liz Clark of Yale University in New Haven, Connecticut, USA. She continues to bring biomechanics-fu to echinoderms– the weird marine critters like seastars and sea urchins. Including fossils, as you’ll see today! You may remember her from blog posts such as “Guest Post: Brittle Star Arms Are Weird“.

Stomach-Churning Rating: 1/10; echinoderms are inoffensive.

Imagine that you’re stuck in a cardboard box on the beach, holding a small stick. Could you use the stick to move yourself forward? What would you do? You could try digging into the sediment ahead of you to pull yourself along. You could try rowing side to side, as if you were in a rowboat. Or maybe it’s not possible and you’d give up, decide to stay put, and wave your stick in the air for help.

Believe it or not, this is a strange-but-important dilemma that some paleobiologists- like me!- have been wrestling with for generations. My research specialty is in the biomechanics of locomotion– how organisms use their bodies to get from one place to the next (through walking or swimming, for instance). We can learn a lot about an animal by studying their locomotion, such as why their body is shaped the way that it is, or what role they occupy in their ecosystem. Animal motion is a major inspiration for robotic design, and I work with engineers to apply the novel insights on animal locomotion from my research to create new kinds of devices.

Studying the biomechanics of motion in living organisms is (relatively) straightforward. We can use high-speed cameras, motion capture software, and 3D imaging tools to visualize and understand how organisms move in real-time, informing our inferences about how they perform certain tasks. Inferring locomotion in fossil organisms, on the other hand, is tricky since we can’t observe the organism’s behavior like we could if the organism were alive. Instead of being able to watch the organism move, we’re left with a snapshot of the animal frozen in place in a rock. We’re also missing a lot of physical information: locomotion in most animals requires soft tissue and hard skeletal structures, but typically with fossils, only the hard structures get preserved.

However, we can often garner some insights from living organisms to determine the locomotion strategies that fossil organisms use. Most organisms in the fossil record look at least somewhat similar to organisms alive today. If our fossil has four legs, for instance, we can study locomotion in living tetrapods (four-legged animals) to help us create a framework for deriving inferences about locomotion in our extinct tetrapod fossil animal. But for some really strange-looking animals- ones without obvious modern analogues- we’re not so lucky. For me, this is where the fun begins.

Figure 1: Stylophorans! Here are four fossilized stylophorans from the Helderberg Group of the Early Devonian (YPM 036413)

So getting back to the cardboard box and the stick. These are metaphorical examples of the different locomotion strategies that have been proposed for a group of fossil animals known as stylophorans (Figure 1). Stylophorans are extinct organisms related to sea stars and sea urchins, but with a body structure unlike any organism on the planet today. They have a large, relatively flat body called a theca (i.e., the cardboard box), and a long, thin segmented tail known as the aulacophore (i.e. the stick) (Figure 2). They’re known in the paleontological community as some of “the strangest-looking animals of all time.”

Figure 2: Stylophoran anatomy. The “theca” is the body cavity, and the “aulacophore” comprises of the proximal aulacophore, the stylocone, and the distal aulacophore.

By reconstructing stylophoran locomotion, we can unlock the mechanics of a unique system for motion and its potential applications to engineering. We can also understand more about how this organism lived and functioned in its ancient ecosystem. And, by developing a new approach to understand locomotion in stylophorans, we can apply this strategy to analyze locomotion and movement in other unusual fossil animals as well!

For years, scientists have been documenting the incredible array of stylophoran diversity in the fossil record and making their best predictions about how they would have been able to move (or not!). These predictions are based on their morphology– the structure of an organism’s body. For stylophorans, that means the shape and structure of the theca and aulacophore. There are a variety of stylophoran thecal shapes, ranging from ovoid in Enopleura to trapezoidal in Ceratocystis to almost crescent-shaped in Cortnurnocystis. There’s a similarly wide array of aulacophore morphologies as well.

Figure 3: Left: One half of the concretion within which the stylophoran fossil we analyzed is preserved. Right: The 3D digital image of the stylophoran fossil, created by micro-CT scanning the fossil specimen.

We developed a new approach using 3D imaging (Figure 3) to create a digital model of a stylophoran specimen. We used the model to test if several different locomotion strategies that had been proposed before were physically possible or impossible for a stylophoran to actually perform.

First, we used a micro-CT scanner to image a fossil stylophoran. This outputs a digital 3D picture of the stylophoran fossil that we can look at and analyze on a computer. Next, we developed a program to calculate the joint centers- the point at which one skeletal structure rotates relative to another-within the digitized stylophoran’s aulacophore (Figure 4). This created a digital marionette– a rig of our stylophoran fossil that flexes at the junctures between aulacophore segments as it would have in life. We then rotated each segment at the joint center to calculate the aulacophore’s total range of motion– a reconstruction of how far the aulacophore could flex in each direction (Figure 5).

Figure 4: A look into some of the nuts and bolts of the 3D model we created. Tri-colored axes demarcate where the joint centers are in the proximal aulacophore. 

We used this 3D range of motion model to evaluate several locomotion strategies that had been previously hypothesized for this group of stylophorans. One hypothesis suggested that these stylophorans dug their aulacophores into the substrate– sediment on the ocean floor- to pull themselves forward. Another suggested that they moved the aulacophore side to side in order to push themselves along. We found that the first hypothesis would have been impossible to conduct based on the range of motion we calculated, but the second strategy was theoretically possible! We’ll need to do more work to see how likely it was that stylophorans would have actually used this technique. Nevertheless, through this investigation, our team produced the first objective, data-driven methodology for analyzing locomotion in fossil invertebrates, which is a big step in the right direction for the study of fossil invertebrate biomechanics! Our technique can be applied to study other organisms with rigid skeletons as well, like crabs, insects, or sea stars, for instance, and we’re looking forward to seeing our technique used to uncover more interesting locomotion strategies!

Figure 5: A snapshot of the 3D model where we can observe how dorsal and ventral range of motion compare to the originally preserved orientation of the aulacophore (highlighted in green).

Do you want to know more? You can! We published a paper on this topic here!

Posted in Biomechanics, Guestsicle | Tagged , , , , , , | 1 Comment »

Years Seven Through Eight of John’s Freezer

March 18, 2020 by John of the Freezers

We live in a weird future. In the Coronavirus pandemic anything seems possible; entropy has been set loose from its cage. Within this higgledy-piggledy universe, I realize that I have forgotten to write annual summaries for this blog for the past 2 years (2018-present). Physical distancing means that I can now make amends — will this pandemic mean the rebirth of the blog, as a means of social un-distancing? If only. Yet in this post, at least, I can take a nostalgic look back at different times. Everything was blissful in 2018 and 2019, right? Oh…

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From the Bone Church/Kutna Hora near Prague, Czech Republic. One of those posts I haven’t made. It was an amazeballs sight.

Stomach-Churning Rating: 4/10 bones (+ bird muscles and bone pathology below), and the years 2018+2019 to boot. May 2021 be more sane.

I’ve been distracted. The DAWNDINOS project has taken an increasingly tremendous amount of my time, energy and concentration, and while it has been fun at many times it also has been the hardest thing I’ve ever done as a scientist. I knew it was a HUGE task when I got the funding notice, I cussed profusely, and then we dove in… and it was huger than huge. It will keep me busy for the rest of my career, no joking. But in good ways, too.

What has happened on the blog? (For year 6 go here) In 2 years, about 14 posts have happened, which surprises me (as it always seems to when I write these summaries). I guess this blog is not dead. Good!

“A day in my life” still roughly applies. I have learned to be even more focused, organised and efficient. Because work/life forced me to. I’ve also learned to enjoy that feeling of intense focus. When I am in that groove, I let it rip; when I’m not, I let it slide.

Much as the “day in John’s life” post noted, my career has shifted to encompass new roles, differing balances of duties, and important lessons. I wrote about “learning by serving” to give some views on service and administration as a rewarding side of being a scientist.

The new UMZC in Cambridge became a theme on this blog: my first visit to the renovated exhibits and building were followed by a second, and then a third! Click those links to see the new-new-new UMZC. We’re lucky to have it in England.

Museum blog posts were popular for me (not so much for readers, it seemed?) over the past 2 years, including the venerable and still-awesome MNHN in Paris. I’ve also hit a few Bodyworlds-type exhibits for the blog over the years, and the big London/Piccadilly Circus one became a must-see, so take a peek here. Then I had the joy of seeing a short-lived Ray Harryhausen exhibit in London. Childhood me would have exploded with glee. Very messily, but a happy end nonetheless. And I happened to walk into a palace-museum in Lausanne — and wow! I will try to remember not to skip those opportunities. Not-so-famous museums can still floor you.

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Silly chimeric specimens at Museum of the Weird in Austin, Texas. Worth the ticket and time.

Post-publication peer review is great, but what about pre-submission publication planning for scientific papers? I gave some advice from my experience as author, reviewer, editor and mentor.

Publications? We got your publications right here. Dr. Liz Clark joined us to regale us with tales of wacky brittle star arms. Who knew how funky ophiuroids were? She did. Now we can.  For Darwin Day in 2019 I cut loose with three papers on evolutionary biomechanics! That was fun! And then Xmas came early with two smiley crocodiley papers. Expect plenty more crocodeliciousness in 2020 onwards.

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Chonky superficial muscles around the left thigh of a tinamou, from DAWNDINOS research-to-come-soon.

Finally, quite a few of the past years have had the quiet undertone for me of trying to make a change of location (i.e. moving back to the USA for another science job). Repeated failures were not fun, as for anyone in the academic job rat race. That long felt like a forbidden, lonely topic but I broke the silence as a form of self-therapy and it helped. I really appreciate the kind feedback I got on that post, too. It was a risky, vulnerable move to make but I am happy I did it. It’s one of my favourite posts on this blog.

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Peer back into the forbidden past of thrash metal and you’ll find screamy classics like this one.

Hmm. I notice in writing this that there haven’t been as many classic “hey here’s something cool I dissected, brace yourselves for the awesome anatomy!” posts on the blog as there used to be. That activity has shifted more to Twitter or else just not been shared, either because I am just dissecting the same old thing (groan, ANOTHER crocodile, another ostrich, another elephant foot!) or I am just out of time. Which is what I am now. Here, consider this pathological (osteomyelitic) ostrich fourth toe while I tiptoe away. Ouch!

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Posted in Uncategorized | 2 Comments »

Crimbo Crocodylian Capers

December 17, 2019 by John of the Freezers

Ho ho ho! The vagaries of the scientific publication system today brings forth TWO open access papers on crocodylian functional anatomy, evolution and biomechanics, from my team with others’; including our DAWNDINOS project in part. Get ready to bite down on the science! I’ve loved crocodylians throughout my life– “dacadile” was among my first words, for a beloved stuffed croc toy, and “Alligators All Around” was an early favourite song (it’s still GREAT).

One of the many large adult alligators in St. Augustine, Florida.

Stomach-Churning Rating: 1/10; bones and movies of awesome behaviours.

First, I am so relieved and pleased to finally publish an experimental study I began over 17 years ago. This is my most-delayed paper ever, due to my own perfectionism, overcommitment and failures at funding it more broadly. But published is published and I’m glad to see it out. We collected a large experimental dataset from 15 species of Crocodylia at the St Augustine Alligator Farm Zoological Park (a conservation/education centre) in Florida. (No matter how you species-ify them, that’s a good chunk of diversity; roughly half or more.) This was a non-invasive study of 42 individuals ranging from 0.5 to 43 kg in body mass (hatchlings to adults). Larger adults were too dangerous or too slow to work with. It took 3 years (2002, 2004, 2005) of data collection to assemble this, with some twists and turns (including a close brush with Hurricane Katrina), and then a lot of analysis and reanalysis; and I’d do it all very differently if I did it today but that’s a moot point. So what’s the paper about?

Adorable Siamese crocodile family “cuddling”. Crocs are great parents! IIRC, that is the father shown.

Some Crocodylia (the inclusive modern name for all crocs, caimans, gharials, gators) are known to use what we call asymmetrical gaits: “mammal-like” footfall patterns in which the left and right limbs do not move as mirror images of each other. In particular, these gaits include galloping (rotary or transverse; either way a “4-beat” pattern with left-right hind- followed by right/left forefoot contacts) and bounding or half-bounding (the former being the most extreme, with left-right hind- and then forefoot contacts as synchronous pairs). Often people just say that crocs can “gallop” but this confuses/conflates the issue and omits that they can use these faster bounding gaits. Regardless, we’ve known about these gaits at least since HB Cott’s 1961 photographic documentation of them in Nile crocodiles; and more detailed studies of Australian freshwater and saltwater crocodiles in the 1970s-2000s. But very often, scientists and popular natural history accounts ascribe the asymmetrical gaits to only a few species or young individuals.

“Freshie” croc bounding in the wilds of Australia; credit Kent Vliet.

Osteolaemus dwarf African crocodile getting marked up for study.

That’s where we came in. We had access to a huge collection of captive Crocodylia and a very supportive institution (with coauthors from there as a result). I wanted to know which Crocodylia do use asymmetrical gaits, having a very strong suspicion from the literature that Alligatoroidea, the alligator and caiman lineage, don’t use them, whereas their cousins the “true crocodiles” in Crocodyloidea do. And I wanted to test how body size interacted with this ability, as prior accounts hinted that asymmetrical gaits got lost with increasing size or in adults. Finally, I was interested in what the benefits of asymmetrical gaits were– did they give those that used them marked boosts in performance, especially maximal speed? Answering that would help understand why these gaits are used.

Cuban crocodile Crocodylus rhombifer in preparation. A gorgeous but aggressive species that we handled carefully.

So we walked and ran our subjects across some platforms past video cameras and collected about 184 useful trials or strides of gait across level ground at a wide range of speeds; and a LOT of not-so-useful data (mostly subjects just sitting and pouting). We found that, yes, most Crocodyloidea we studied could bound or gallop; and no Alligatoroidea did. In the latter case, we didn’t use as large a sample of subjects as we could have, partly because it already seemed evident that alligators did not use asymmetrical gaits, and partly because those alligatoroids we did try to coax to move quickly either only used symmetrical gaits (e.g. trotting) or would only sit and fight or hiss. And we found that bigger animals moved at least relatively more slowly and less athletically, and perhaps even more slowly in absolute terms (metres/second).

Most intriguingly to me, it didn’t matter what gait alligatoroids or crocodyloids used. They all could move at roughly similar top speeds if they wanted to; less than 5 m/s or 11 mph. It’s just that crocodyloids tended to use asymmetrical gaits, especially bounding, at top speeds– but not always: some even chose to trot at their top speeds. We don’t know why, and we still don’t know why asymmetrical gaits are chosen but they likely have other benefits such as acceleration and manoeuvrability.

It’s a thrill to finally be able to share the huge dataset, including a gigantic file of videos (with some highlights shown here), with the paper, closing this study at last. It should be very useful to anyone studying Crocodylia or wanting to educate people about locomotion. I’m a bit tired of hearing that galloping is a mammalian behaviour when we know so well that many species of animals do it, or something like it. And it was absolutely thrilling to see five species of Crocodylia bound or gallop when they hadn’t been properly documented to do it before– enough anecdotes, here’s cold hard facts from video on what happens. What remains is a mystery: did Crocodylia have this ability to use asymmetrical gaits as an ancestral trait, as almost everyone assumes (and thus alligators and caimans have lost or essentially never express the ability), or did crocodiles uniquely evolve this ability more recently? I would join most scientists in wagering on the former; and there are good reasons to suspect the ability goes deeper into extinct Crocodylomorpha.

(my favourite video is below!)

Want more cool videos? Try my Youtube channel— or if you want ALL of the videos, go here!

Next, Torsten Scheyer was kind enough to invite me to join his team in studying a fossil I’ve long been fascinated by: the “giant caiman” Purussaurus mirandai, from the Miocene (~6 million years ago?) of Venezuela, in the Urumaco Formation‘s very weird biota. Purussaurus has been known of for >125 years but Torsten’s team noticed that Purussaurus (mirandai) specimens tended to add one of their trunk vertebrae to their hip girdles (sacrum; normally only two vertebrae in Crocodylia but here three), and that the shoulder and hip girdles had unusual bone morphology (straighter, more vertical relative to the body). So they asked me to help interpret these features. And here’s the paper!

Infographic by Torsten Scheyer’s team– click to emcroccen!

Three-vertebra sacrum and other traits of Purussaurus; with living caiman bones for comparison. E (bottom): inwards-facing femur head. (see paper for more info)

It became evident that, together, those odd traits conveyed a signal that the skeleton was transformed to aid in supporting the huge body against gravity. For example, I found it quite interesting how the head of the femur (thigh bone) was oriented more directly into the hip socket in multiple specimens, more like a dinosaur’s hip, and specialised for support and fore-aft motions. I used Haley O’Brien et al’s data to estimate just how big P. mirandai might have been and it came out as perhaps 3000 kg and 8 metres total length; as we’d thought, among the largest Crocodylia (and there are larger Purussaurus known, too).

Reconstruction of Purussaurus and morphology of the girdles. (see paper for more info)

The team also put a cool “evo-devo-biomechanics” spin on the study. It is well known that the regional identities of vertebrae (e.g. neck, trunk, sacrum, tail) are largely determined by Hox (homeobox) regulatory genes, early in development. So changes of vertebral identity intimate changes of genetic controls. Crocodylia don’t normally add a trunk vertebra to their sacrum, and only a few fossil crocodyliforms (extinct cousins) ever did either, but we noticed that some specimens of Crocodylia would at least partially make this transformation in pathological states (below). Hence the controls to make these changes exist and sometimes manifest in living crocs, but it’s probably not an “easy” transformation to achieve. One could speculate that under intense selection, such as that imposed by giant body size and some degree of activity on land, that transformation could more easily get permanently “fixed” in a species.

Palaeosuchus palpebrosus (Cuvier’s dwarf caiman) with pathological partial-three-vertebra-sacrum; and lots more morphology. (see paper for more info)

As a nice tie-in to the asymmetrical gait study above, we can safely infer that the giant Purussaurus wasn’t a fast animal on land, by any means. But its skeleton is consistent with it having found novel ways to maintain the ability to stand and move on land, even if slowly.

Happy holidays! Santa Jaws is watching you– be good!

Posted in Croc-cicles, Exalting Archosauria | Tagged , , , , , , | 3 Comments »

My Kind of Palace

August 29, 2019 by John of the Freezers

If you go into central Lausanne, Switzerland, you’re likely to pass the Palais du Remine, and if you do, I recommend you go inside. I was happy I did while visiting Lausanne for the AMAM2019 conference. A luxurious palace has been given over to house five (!) free (!) museums on science and culture. These include the canton’s (~state’s) museums of palaeontology and zoology, which I’ll showcase here (also a little of geology and archaeology museums). Tripadvisor’s reviews were good but not as glowing as I’d make mine, so I will remedy that. I’m a sucka for old-school museums, and that’s what these are. So if that sounds right for you, journey onward!

It’s nice.

As you may be expecting by now if you’ve been here before, it’s time for another museum photo blog!

Stomach-Churning Rating: 5/10 for bones, preserved organs, taxidermy aplenty, and animal developmental deformities.

Nice cathedral nearby, w/great view of the city.

Nice interior architecture. There’s lots of nice to behold.

Posters That Get You Excited 101. But you must wait. Like I did.

Quadrupedal human at Zoology museum entry.

Tomistoma, false gharial.

Not a bad collection of taxidermied Crocodylia!

Visually arresting cobra display.

I’ve never seen three Draco gliding lizards on display together!

Bipedal lizard taxidermy displays, freezing the dynamic in the static, are no easy feat.

Plenty of stuffed animals like these raptors/other large birds. Classical zoology museum style. Minimal signage. Just specimen labels, mainly.

Coelacanth!

Sperm whale jaw.

Open space with big specimens. A ~4m long great white shark included.

Second zoology hall: bones!

Gorilla standing tall next to human.

Ostrich skeleton up close, amongst the mammalz.

Cassowary skeleton.

Emu shoulder/arm bones in right side view.

Walrus skeleton in what seems like an odd pose to me, but then they are odd on land.

Alligator skeleton in repose.

Giant anteater, “knuckle-walking”.

Pangolin skeleton! And mounted digging into a nest– very well done!

Bernard Heuvelmans display, about the (in)famous cryptozoologist. This was quite a surprise to me. I’m sure I’d read his English-translated book “On the Track of Unknown Animals” as a kid, during my long stint as an avid reader of much zoology, crypto- and otherwise. He bequeathed a lot of his work to the museum.

Bernard’s handwritten CV!? With a “sea serpent” sketch.

A “sea serpent” vertebra… but if you know any anatomy, it’s not a snake’s vertebra at all but a fish’s, such as a basking shark‘s.

Are you ready for more weirdness? How about some “mutants”- congenital deformities of animals? Fascinating errors of developmental anatomy… somehow this two-headed calf survived awhile. Plenty more where that came from, as follows:

And then there’s all kinds of wonderful comparative anatomy. To be a student of this subject in Lausanne would be a lucky thing, with this museum’s collection at hand. These are valuable specimens, made with love and skill.

Jaws

Fish head anatomy. Some vertebrae on the left, too.

Developmental regions of the head: a lovely wax(?) model of an Echidna skull. A treasure.

Brains: alligator vs. pigeon.

Salamander muscles.

Pigeon muscles.

More spotted felids than you can shake a jar of catnip at.

Another pangolin!

Giant armadillo.

Petaurus: flying phalanger (a gliding marsupial).

Second zoology hall open area: left side.

Second zoology hall open area: right side.

A final hall with a more new-fangled display, on the topic of evolution and extinction. Attractive phylogeny graphic here. Birds at the “top”, of course. Poor lowly mammals!

Taxidermied giant auk- not a common sight! (Extinct)

The extinct southern pig-footed bandicoot. Also a rare sight of a whole specimen- in a Swiss museum, too.

NOW ON TO THE FOSSILS!

You’ve been very patient. Here, have a Toblerone.

Palaeo museum entry. Already there are cool things visible. Inside, we find it just like I prefer my zoo/palaeo museums (as above): stuffed with specimens and leaving plenty for you to wonder about and investigate. Not frilly; a well-stocked museum that mostly lets its specimens speak for themselves.

Sauriermuseum (Aathal) specimen of Plateosaurus: sculpt/cast. A very good, big skeleton of this common dinosaur, rearing up.

Rear view of same.

Real bones of same; vertebrae and pelvic (this is the “Frick specimen”).

Metaxytherium (current name), an ancient and large fossil dugong/seacow. Skull is in left side view. (that may help, as their skulls are odd!)

Anthracotherium upper jaw: ancient hippo-cousin.

Prolagus: the “Sardinian hare” (recently extinct; old lineage).

Potamotherium: to some an early otter-like mammal, more recently thought to be an ancient seal.

“Broke-ulum”: a walrus broke its penis bone (baculum) and was surely not pleased about it, but lived to heal— physically if not mentally. Yeesh!

Glyptodont tail club and armour.

Aepyornis elephant bird legs!

A partial/reconstructed skeleton of the dodo.

Velociraptor preparing to pounce from above. It’s too late for you!

Rhamphorhynchus fossil (2D slab) and sculpt/cast coming alive in 3D– good stuff.

Anhanguera pterosaur watches the chaos from above, fish snagged in its teeth.

Not-shabby metriorhynchid marine croc fossils, from Britain.

Lovely 3D plesiosaur bones (flippers, neck, etc.) from near RVC: Peterborough!

Mesosaur; early reptile.

The museum clearly is proud of its excellent “Mammoth of Brassus” skeleton, essentially complete.

Ice Age elk/moose, a 10,000 year old skeleton in fine shape.

Cave bear skull rawr

Purty ammonites!

Spiky ammonite!

Cretaceous sponge colony from France. I hadn’t seen something like this before, so here it is.

Trilobites, brittlestars and friends.

Well I did wander through the geology and archaeology museums too, and while I liked them I did not take so many photos. My non-human organismal bias is apparent. But check these final ones out:

Splendid cross-section of the stratigraphy of the Alps around Lausanne. I gazed at this for quite a few minutes, trying to figure out what was where in the landscape I’d seen and how old, how deformed, etc.

Slab of “dinosaur” tracks but it was not clear to me what dinosaurs/archosaurs/whatever made them. I wish my French was better. Closeup below shows two footprints superimposed.

At last, the coup de grace! What museum would be complete without a diorama!? (I love them) This one, with a goat sacrifice and early Stone Age people praying to heathen deities/spirits at an elaborate petroglyph array rocked my world. And so it makes a perfect final image. Enjoy, and conduct the proper rites.  \m/

 

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The Forbidden Academic Tale

August 10, 2019 by John of the Freezers

I’ve written some soul-searching posts here before, but the topic I’ve long held back from addressing is the one that feels most forbidden as a senior-level academic. Today I’ve relented and written on it. Well, anyway I wrote this about 4 months ago and sat on it, and now’s the time. To hell with the forbidden — it is that nature which has been a torment. In academia we hear many stories, and are encouraged to talk openly about, the trials and tribulations of securing a permanent faculty (or similar; e.g. curator) post. I could write about my experience as an early career scientist, which wasn’t easy, but it wouldn’t be as contemporary or as fraught with emotion as this one is. This post is about the next step, one we hear so little about: attempting a mid-career transition between institutions.

I’ve bottled these thoughts up long enough but realized they are a teachable moment that others may benefit from, as I will loop back to at the end. The point of the post is not to seek pity or sympathy, or convey that doom and gloom about academia that pervades the internet, or even to hope for empathy, but to simply state this how it has been for me so far (SPOILER: it’s a story of failure), if one is headed down this path it might help, or at least the tale might be of interest in some other way, even having parallels with some non-academic careers.

Stomach-Churning Rating: me 1010/10; yours will vary

It is probably a good idea, and I don’t know the statistics but I imagine it is common, to move between institutions at least once in a scientist’s career, and not uncommonly twice; thrice enters a bad dimension and four or more times is either pathological or purposefully peripatetic (which might be fun!). Sooner or later one wants a change of pace: one may seek to move up the ladder to a better institution, more salary or other benefits, more desirable geographic location, escape poor working conditions for anything else, and/or other factors. New adventure, mid-life crisis, whatever. At mid-career, the temporal window is closing to find that place you finish your career at, hoping for ultimate stability and satisfaction. The pressure begins mounting, but while the opportunities to transition at assistant professor level are small (with much competition), the opportunities to do so at associate professor, let alone full professor level, approach the nadir. It varies among fields and geographic regions (and how choosy one is), but there may be only 1-2 jobs in one’s field in a year. Competition may be smaller than at junior level, or just hard to even compare, but a qualitatively different factor emerges.

Early career scientists (ECSs) are evaluated in job interviews for faculty-level posts in terms of their potential to grow to become what the institution needs; with evidence of already being on that trajectory important. But it’s less about who you are as how you convince the institution that you can become that dream academic they need most. At a mid-career level, everything is in plain sight. You have a track record. You probably know 1+ people in the institution or they might never give your application a second look. So as a known quantity, the question switches to how the person fits what is needed now and in the immediate future. They are less malleable. They probably won’t do a major pivot to change their research or other direction; that’s hard at a senior level (and an uphill battle to convince committees of). Once the few candidates have been interviewed, it’s probably clear to the search committee who fits their needs. There is less likely to be the “what if?” mystery with the ambiguous future of ECSs that may leave the committee more uncertain. It’s like being handed a puzzle to put together, vs. handed a batch of ingredients to cook freestyle.

Now begins my personal story. It’s maybe the worst-kept secret I have, I realize. And now I’m OK with that. When I came to the RVC, I was told that I’d probably remain for 5-7 years and then move back to the USA, and that was fine — even expected. I thought as much, too, and by the end of that time period I’d been applying for jobs to make that return voyage as prophesized. 10 years later, after almost 16 years, I’m still here. I’ve hit the wall of the mid-career transition and had to come to grips with its harsh reality. With few jobs and slim odds, I worry that I’m near an event horizon. I’m an academic straddling some fields that makes me somewhat of a square peg for many jobs. What am I? Do I fit into conventional labels and needs? This has been my career-long identity struggle — an evolutionary biomechanist is a weird mix. Having a large grant, too (the DAWNDINOS one), could be seen as an impediment as I’m still set on a major research project for 2 more years. Yet who knows… the rest is personal and remains uncertain.

Before I finish I must address the forbidden nature of such concerns. As mid-career academics, we’re enormously privileged. We have a job, perhaps a family, a home, relative stability and security, and so forth. ECSs might give anything for that! But we have our own lives to live, and the existential crisis of time-is-running-out only gets more intense. The prizes of tenure and other success may not come with happiness. We may feel “forbidden” to speak of our experiences not only because of such privilege, but also because of massively complex socio-political interactions that face us when trying to move institutions. I am fortunate that my institution has had my back throughout my process — others would not be so kind. I’ve heard of some universities that will sack their academics if they mention to senior administrators that they are contemplating a move! That’s just evil.

It can cause deep anxiety, uncertainty, political chicanery and other trouble for the news of seeking a mid-career transition to reach the wrong ears at the wrong time — particularly as it tends to be a prolonged, uncertain process. Seeking a job vs. moving with a signed contract are different things! Far, far, far apart on the spectrum of certainty are they. Moreover, the choice to seek to move jobs is a personal and private one. We may not want to become the topics of idle gossip, or even misinformation and undermining. These factors make the journey a lonely and unique one, and it would be a grotesque understatement to say that the personal (e.g. family, health) dynamics involved will compound the stresses. Together these can impact not just life outside of work but performance at and enjoyment of work itself.

The learning opportunity that I most want to share is this: if you’re on this kind of career track, plan to move early and get started early. Apply to jobs sooner (i.e. as an assistant professor) than later (i.e. tenure onwards) even if you’re not sure about wanting to move. Talk to your partner, peers or those that matter most about this; have a trusted, private support network and advice. Get some irons in the fire and see what opportunities arise. Expect that it may take much longer than you thought, so be strategic. Have a plan B, C and D; think about how flexible you can be. And, while you might do well getting interviews and hear nice things about how amazing you are (cold comfort at times), get used to the answer that you just don’t fit what a search committee was looking for. “Fit” is that Swiss army knife of words we use in such situations in academia, to embrace a wide range of reasons we don’t want to (or can’t, for HR/legal concerns) get into at the time for why a job decision is made. A lack of “fit” is a hard word to hear and accept, as we might see it otherwise, but it is the reality and we must accept it. By accepting such realities, perhaps the forbidden will become bearable.

Posted in RANT | Tagged , , , | 4 Comments »

Zoology Museum: Take 3

August 4, 2019 by John of the Freezers

I heard that the UMZC has some new exhibits open, so back I went! For the prior posts see here (mammals/basement) and here (everything else). Another photo tour! There’s a special (art) exhibit, too, so stick around to the end.

All images can be clicked to mu-zoom in on them.

Stomach-Churning Rating: 3/10 mainly skeletons, some preserved critters in jars.

The first new section is an elaborated display on reptiles.

Clevosaurus, a Triassic relative of the living tuatara reptile, Sphenodon. Nice fossil hindlimbs!

Tuataras (Sphenodon), skeletal and preserved.

Tuatara embryos!

Nice chameleon mount w/tongue extended.

Thorny devil (Moloch), de-thorned and in the flesh.

Skull (cast) of Ninjemys, the giant turtle.

Pipe snakes! Snakes with vestigial hindlegs.

Istiodactylus pterosaur snout-tip (real fossil) from the Isle of Wight, UK. Nice 3D fossil.

The gharial (Gavialis), male with protuberance on snout (mating-related).

I dub thee Dinosaur Corner! For dinosaurs, the Sedgwick Museum across the street (also free; also classic and awesome) is the place to go but this corner does a good job fighting for the scientific conclusion that birds are dinosaurs.

And now a change of pace. On to the special exhibit!

A nice surprise to see naturalist superstar Jonathan Kingdon‘s scientific illustrations and nature-inspired artwork displayed here. I’ve added photos of ones I liked the most.

As the caption explains, Kingdon used art to explain the value of nature; via realistic images of life, dissections, and creative abstractions drawn from them.

Hammerhead bats: even freakier when skinned.

Begone if ye find not joy in aardvarks!

White-toothed shrew looking extra-ghoulish with flensed face.

Skinned sengis in action.

More sengis (elephant shrews); with a note explaining that they are not rodents/insectivores but afrotheres, cousins of aardvarks, elephants and kin.

Bronze Jackson’s chameleon bust.

Asian barbet faces: this was fascinating. Kingdon used the paintings to explain how barbet faces vary across species as recognition devices to aid in territorial defense, especially of their nest-holes in trees, in which they face outwards to display their coloured faces. The middle image shows one lone species that has no such territorial competitors and has evolved back into brown colour, perhaps due to relaxed selective pressure for colour. Neat!

Oh my, this took my breath away! Mixed media depicting the varied forms of facial ornaments in vultures; soft tissues used in communcation. And here mounted on a butcher’s rack. Do vulture bits mimic their grisly food?

Posted in Museums are Cool, Two-Dog-Night Tetrapods | Tagged , , , , , | 6 Comments »

These Are A Few of Mon Préféré Things

March 3, 2019 by John of the Freezers

To me, there is no question that the Galerie de Paléontologie et d’Anatomie comparée of Paris’s Muséum national d’Histoire naturelle (MNHN) is the mecca of organismal anatomy, as their homepage describes. Georges Cuvier got the morphological ball rolling there and numerous luminaries were in various ways associated with it too; Buffon and Lamarck and St Hiliaire to name but a few early ones. It is easy to think of other contenders such as the NHMUK in London (i.e., Owen), Jena in Germany, the MCZ at Harvard (e.g. Romer) and so forth. But they don’t quite cut the dijon.

As today is John’s Freezer’s 7th blogoversary, and I was just at the MNHN in Paris snapping photos of their mecca, it’s time for an overdue homage to the magnificent mustard of that maison du morphologie. The exhibits have little signage and are an eclectic mix of specimens, but this adds to its appeal and eccentricity for me. I’ve chosen some of my favourite things I saw on exhibit on this visit, with a focus on things that get less attention (NO MESOZOIC DINOSAURS! sorry), are just odd, or otherwise caught my fancy. It’s a photo blog post, so I shall shut up now, much as I could gush about this place. I could live here.

Need plus-grand images? Clic!

Stomach-Churning Rating: 7/10 for some potentially disturbing anatomical images such as viscera, preserved bits, models of naughty bits etc.

Greetings. Note the stomach-churning rating above, please.

Right. We’ll get the amazing first view as one steps into the gallery done first. Mucho mecca. Anatomy fans simply must go here at least once in their life to experience it, and one cannot ever truly absorb all the history and profound, abundant details of morphology on exhibit.

Less-often-seen views from the balcony; one more below.

Indian Rhinoceros from Versailles’s royal menagerie; came to the MNHN in 1792.

Brown bear hindlimb bones.

Brown bear forelimb bones and pelvis.

Two baby polar bears; part of the extensive display of ontogeny (too often missing in other museums’ exhibits).

Asian elephant from Sri Lanka.

Lamb birth defect. Like ontogeny, pathology was a major research interest in the original MNHN days.

Wild boar birth defect.

Fabulous large Indian gharial skull + skeleton.

“Exploded” Nile crocodile skull to show major bones.

Let’s play name-all-the-fish-skull-bones, shall we?

Rare sight of a well-prepared Mola mola ocean sunfish skeleton.

Diversity of large bird eggs.

Asian musk deer (male), with tooth roots exposed.

Freaky gorilla is here to say that now the really odd specimens begin, including the squishy bits.

Freaky tamandua, to keep freaky gorilla company. Displaying salivary glands associated with the tongue/pharynx. These are examples of anatomical preparations using older analogues of plastination, such as papier-mâché modelling. I’m not completely sure how the preservation was done here.

Tamandua preserved head, showing palate/tongue/pharynx mechanism.

Chimp ears. Because.

Why not add another chimp ear?

Many-chambered ruminant stomach of a sheep.

Simpler stomach of a wolf. Not much room for Little Red Riding Hood, I’m afraid.

Expansive surface area of a hippo’s stomach; but not a multi-chambered ruminant gut.

Cervical air sacs of a Turquoise-fronted Amazon parrot.

Heart and rather complex pulmonary system of a varanid lizard.

It’s pharynx time: Keratinous spines of a sea turtle’s throat. All the better to grip squids or jellies!

Pharynx convergent evolution in a giraffe: keratinous spines to help grip food and protect the pharynx from spiny acacia thorns while it passes down the long throat.

Tongue/hyoid region of the pharynx of a varanid, showing the forked tongue mechanism.

Palaeontological awesomeness on the upper floor (the 2nd part of the gallery’s name). Here, the only Siberian woolly mammoth, I’m told, to have left Russia for permanent display like this. Frozen left side of face, here, and 2 more parts below.

Mammuthus primigenius freeze-dried lower ?left forelimb.

Skeleton that goes with the above 2 parts. It’s big.

But “big” is only relative- my large hand for scale here vs. a simply ginormous Mammuthus meridionalis; full skeleton below.

Four-tusked, moderate-sized Amebelodon elephantiform.

Naked woolly rhinoceros Coelodonta.

Extinct rhino Diaceratherium, with a pathological ankle (degenerative joint disease). I love spotting pathologies in specimens- it makes them stand out more as individuals that lived a unique life.

Glyptodont butt and thagomizer, to begin our tour of this business-end weaponry.

Eutatus leg bones, from a large fossil armadillo; Argentina. Really odd morphology; Xenarthrans are so cool.

Giant ground sloth (Megatherium) foot; ridiculously weird.

Giant ground sloth hand is full of WTF.

Metriorhynchus sea-crocodile from the Cretaceous: hind end.

Odobenocetops one-tusked whale that I still cannot get my head around, how it converged so closely on the morphology of a walrus.

Thalassocnus, the large marine sloth… few fossils are so strange to me as this one. But modern sloths swim well enough so why not, evolution says!

Rear end of the sea-sloth.

Megaladapis, the giant friggin’ lemur! Not cuddly.

A basilosaurid whale Cynthiacetus, one of the stars of the show, as the denouement of this post. Plan your visit now!

Posted in Museums are Cool, Voyages | Tagged , , , , , , , , , | 6 Comments »

Darwin Day 2019: Some Papers In Evolutionary Biomechanics

February 12, 2019 by John of the Freezers

Today is the 210th anniversary of Charles R. Darwin’s birthday so I put together a quick post. I’d been meaning to blog about some of our latest scientific papers, so I chose those that had an explicit evolutionary theme, which I hope Chuck would like. Here they are, each with a purty picture and a short explainer blurb! Also please check out Anatomy To You’s post by Katrina van Grouw on Darwin’s fancy pigeons.

Stomach-Churning Rating: 1/10 science!

First, Brandon Kilbourne at the Naturkunde Museum in Berlin kindly invited me to assist in a paper from his German fellowship studying mustelid mammals (otters, weasels, wolverines, badgers, etc.; stinky smaller carnivorous mammals). Here we (very much driven by Brandon; I was along for the ride) didn’t just look at how forelimb bone shape changes with body size in this ecologically diverse group. We already knew bigger mustelids would have more robust bones, although it was cool to see how swimming-adapted and digging-adapted mustelids evolved similarly robust bones; whereas climbing ones had the skinniest bones.

The really exciting and novel (yes I am using that much-abused word!) aspect of the paper is that Brandon conjured some sorcery with the latest methods for analysing evolutionary trends, to test how forelimb bone shapes evolved. Was their pattern of evolution mostly a leisurely “random walk” or were there early bursts of shape innovation in the mustelid tree of life, or did shape evolve toward one or more optimal shapes (e.g. suited to ecology/habitat)? We found that the most likely pattern involved multiple rates of evolution and/or optima, rather than a single regime. And it was fascinating to see that the patterns of internal shape change deviated from external shape change such as bone lengths: so perhaps selection sometimes works independently at many levels of bone morphology?

Various evolutionary models applied to the phylogeny of mustelids.

Then there, coincidentally, was another paper originating in part from the same museum group in Berlin. This one I’d been involved in as a co-investigator (author) on a Volkswagen (yes! They like science) grant back about 8 years ago and since. There is an amazing ~290 million year old fossil near-amniote (more terrestrial tetrapod) called Orobates pabsti, preserved with good skeletal material but also sets of footprints that match bones very well, allowing a rare match of the two down to this species level. John Nyakatura’s team had 3D modelled this animal before, so we set out to use digital techniques to test how it did, or did not, move—similar to what I’d tried before with Tyrannosaurus, Ichthyostega and so forth. The main question was whether Orobates moved in a more “ancestral” salamander-like way, a more “derived” lizard-like way (i.e. amniote-ish), or something else.

The approach was like a science sledgehammer: we combined experimental studies of 4 living tetrapods (to approximate “rules” of various sprawling gaits), a digital marionette of Orobates (to assess how well its skeleton stayed articulated in various motions), and two robotics analysis (led by robotics guru Auke Ijspeert and his amazing team): a physical robot version “OroBOT” (as a real-world test of our methods), and a biomechanical simulation of OroBOT (to estimate hard-to-measure things in the other analyses, and matches of motions to footprints). And, best of all, we made it all transparent: you can go play with our interactive website, which I still find very fun to explore, and test what motion patterns do or do not work best for Orobates. We concluded that a more amniote-like set of motions was most plausible, which means such motions might have first evolved outside of amniotes.

OroBOT in tha house!

You may remember Crassigyrinus, the early tetrapod, from a prior post on Anatomy To You. My PhD student Eva Herbst finished her anatomical study of the best fossils we could fit into a microCT-scanner and found some neat new details about the “tadpole from hell”. Buried in the rocky matrix were previously unrecognized bones: vertebrae (pleurocentra; the smaller nubbins of what may be “rhachitomous” bipartite classic tetrapod/omorph structure), ribs (from broad thoracic ones to thin rear ones), pelvic (pubis; lower front), and numerous limb bones. One interesting trait we noticed was that the metatarsals (“sole bones” of the foot) were not symmetrical from left-to-right across each bone, as shown below. Such asymmetry was previously used to infer that some early tetrapods were terrestrial, yet Crassigyrinus was uncontroversially aquatic, so what’s up with that? Maybe this asymmetry is a “hangover” from more terrestrial ancestry, or maybe these bones get asymmetrical for non-terrestrial reasons.

The oddly asymmetrical metatarsals of Crassigyrinus.

Finally, Dr. Peter Bishop finished his PhD at Griffith University in Australia and came to join us as a DAWNDINOS postdoc. He blasted out three of his thesis chapters (starting here) with me and many others as coauthors, all three papers building on a major theme: how does the inner bone structure (spongy or cancellous bone) relate to hindlimb function in theropod dinosaurs (including birds) and how did that evolve? Might it tell us something about how leg posture or even gait evolved? There are big theories in “mechanobiology” variously named Wolff’s Law or the Trajectorial Theory that explain why, at certain levels, bony struts tend to align themselves to help resist certain stresses, and thus their alignment can be “read” to indicate stresses. Sometimes. It’s complicated!

Undaunted, Peter measured a bunch of theropod limb bones’ inner geometry and found consistent differences in how the “tracts” of bony struts, mainly around joints, were oriented. He then built a biomechanical model of a chicken to test if the loads that muscles placed on the joints incurred stresses that matched the tracts’ orientations. Hmm, they did! Then, with renewed confidence that we can use this in the fossil record to infer approximate limb postures, Peter scanned and modelled a less birdlike Daspletosaurus (smaller tyrannosaur) and more birdlike “Troodon” (now Stenonychosaurus; long story). Nicely fitting many other studies’ conclusions, Peter found that the tyrannosaur had a more straightened hindlimb whereas the troodontid had a more crouched hindlimb; intermediate between the tyrannosaur and chicken. Voila! More evidence for a gradual evolution of leg posture across Mesozoic-theropods-into-modern-birds. That’s nice.

Three theropods, three best-supported postures based on cancellous bone architecture.

If you are still thirsty for more papers even if they are less evolutionary, here’s the quick scoop on ones I’ve neglected until now:

(1) Former PhD student Chris Basu published his thesis work w/us on measuring giraffe walking dynamics with force plates, finding that they move mostly like other quadrupeds and their wobbly necks might cost them a little.

(2) Oh, and Chris’s second paper just came out as I was writing this! We measured faster giraffe gaits in the wilds of South Africa, as zoo giraffes couldn’t safely do them. And we found they don’t normally go airborne, just using a rotary gallop (not trot, pace or canter); unlike some other mammals. Stay tuned: next we get evolutionary with this project!

(2) How do you safely anaesthetize a Nile crocodile? There’s now a rigorous protocol (from our DAWNDINOS work).

(3) Kickstarting my broad interest in how animals do “extreme” non-locomotor motions, we simulated how greyhounds stand up, finding that even without stretchy tendons they should, barely, be able to do it, which is neat. Expect much more about this from us in due time.

(4) Let’s simulate some more biomechanics! Ashley Heers, an NSF research fellow w/me for a year, simulated how growing chukar birds use their wing muscles to flap their way up steeper inclines (“WAIR” for devotees), and the results were very encouraging for simulating this behaviour in more detail (e.g. tendons seem to matter a lot) and even in fossil species; and finally…

(5) Hey did you ever think about how bone shape differs between hopping marsupials (macropods) and galloping artiodactyl (even-toed) mammals? We did, in long-the-making work from an old BBSRC grant with Michael Doube et al., and one cool thing is that they mostly don’t change shape with body size that differently, even though one is more bipedal at faster speeds—so maybe it is lower-intensity, slower behaviours that (sometimes?) influence bone shape more?

So there you have the skinny on what we’ve been up to lately, messing around with evolution, biomechanics and morphology.

Posted in Biomechanics, Exalting Archosauria, Freezermas, Frozen Mammals, Two-Dog-Night Tetrapods | Tagged , , , , , , , , , | 1 Comment »

Learning by Serving

January 14, 2019 by John of the Freezers

I had the privilege and pleasure of serving for the past 2 years as Chair of the Division of Vertebrate Morphology at the Society for Integrative and Comparative Biology, and that service just ended. So I had the showerthought to briefly post about the broader messages from that experience, with the hope that other scientists might benefit. But first, a little backstory.

Stomach-Churning Rating: 0/10

I’d only done some minor service before this, in scientific societies. At the time I ran for Chair-Elect 5 years ago, I felt it was time to try something new; to give back to science, as one should do. And so I did. It was a challenging and thus rewarding experience of learning the ropes- the Chair position is fairly open-ended to allow one to contribute what new things and leadership one envisions and can manage. In a short 2 years I felt I gained just enough momentum that I could have run the role more smoothly if I’d had a 3rd year, but that’s hindsight. The details don’t matter here but they lead to the messages of this post.

wink-wink musical interlude 1

First, the simple message that service, like the Holy Ghost, is the oft-forgotten third component of the trinity of professional science/academia; teaching and research being the other two (and science communication, to me, bridging all of these). As one moves along in one’s career, service tends to become increasingly expected—and the wisdom accumulated aids its conduct.

Second, service should be done because:

  • It’s the right thing to do
  • You learn things about your professional society, discipline, colleagues, leadership and self (skills and limits)
  • It’s not necessarily just boring bureaucracy (more about that below)
  • It will aid your career (CV, promotion, connections, future service, etc.) and you can aid others along the way

I think a common misconception is that service is boring. Yes, hearing the minutes of prior meetings read to you, or a long screed about minutia of health-and-safety, can be boring at times. But pay attention and find things that interest you and new vistas can open. This depends on the position one serves in and how it fits you. In my case, I found it a fun challenge to run meetings (i.e. try to follow the standard protocol of devising an agenda, checking minutes, etc.; standard bureaucracy) – especially the key activity of raising and voting on issues to consider taking the division in new directions. That allowed some creativity and made for energetic discussions on issues that mattered.

Another contrast to “boring” is resolving crises that arise (in my case, quite a few arose that felt serious to me). Yes, they’re stressful, but they also teach you things about how to handle crises, and you learn about your own ability to do so; and how others interface with that dynamic process. As I tend to emphasize on this blog, doing science is HUGELY about human interactions and foibles, and in service, as everywhere, such things are especially prominent and complex.

wink-wink musical interlude 2

Service comes in many forms. Students and postdocs can and should take part—many societies such as SICB tend to allow or encourage early career researcher participation. At a minimum, scientists should vote on elections (participation tends to be low among student/postdoc members) and attend their societies’ business or other meetings to see how the machine of a professional society works inside. It may even learn to serendipitous outcomes! And lessons learned will serve you well in many forms of future career.

One can do many other forms of service. Minimally in research, one is expected to participate in peer review; and that experience can lead to editor roles at journals, which I’ve found very interesting. Certainly in academic and other departments, there are numerous committee and other roles analogous to those in professional societies that are opportunities to serve.

I’ve surely left out other important lessons learned from serving. I’m still processing my experiences, reflecting and thinking forward. Now I’ve moved on to new service at SICB as Chair of the Student-Postdoc Affairs Committee, so there’s lots more for me to learn and share in that role.

What have you learned from serving? Do you have questions about service in science? Please chime in below.

More links of interest:

DVM-DCB Twitter feed

DVM Facebook page (members+affiliates)

SPDAC Facebook page (anyone!)

SPDAC Twitter feed

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