Posted in caudal

New paper: Hart et al. 2025 on neural canal ridges in crocs

The dawn of a new era: AMNH FR 34089, a caudal vertebra of the giant extinct croc Thecachampsa, backlit to show the neural canal ridges. This is not just my favorite specimen with NCRs, it’s one of my favorite images of any fossil ever. Photo by William Jude Hart.

New paper out:

Hart, W.J., Atterholt, J., and Wedel, M.J. 2025. First occurrences of neural canal ridges in Crocodylia. Acta Palaeontologica Polonica 70(4): 749–753.

This one started last autumn. On October 2, 2024, I got an email from William Jude Hart, then an undergraduate at Hofstra University. At the time he was preparing to present a poster at the upcoming 2024 SVP meeting, on a caudal vertebra of a large extinct croc, Thecachampsa. Thecachampsa was a tomistomine gavialoid, closely related to the extant False Gharial, Tomistoma, which in turn is a member of Gavialidae and therefore a lot less “false” than we used to think. Thecachampsa lived on the east coast of North America in the Miocene, and it was bigger and scarier than any croc alive today. William had seen Atterholt et al. (2024), my paper with Jessie and a gang of other folks on neural canal ridges (NCRs) in non-avian dinosaurs — which we interpreted as bony spinal cord supports, following Skutschas and Baleeva (2012; see this post and this one). He had noted similar structures in his Thecachampsa caudal, and he offered to send photos.

OMNH RE 0215, a third dorsal vertebra of an alligator in anterior view showing the bilobed neural canal. Also used in Atterholt et al. (2024: fig. 9).

I was interested to see photos of the Thecachampsa vert, but I was trying to moderate my excitement. A lot of crocs have bilobed neural canals, shaped like a snowman or a numeral 8, with a larger lower passage for the spinal cord and its associated meninges, and a smaller upper passage for the large supraspinal vein (a character shared with many birds — see Atterholt et al. 2025 and this post). The two passages are often divided by longitudinal bony ridges, and these can mimic bony spinal cord supports. Criteria exist to distinguish the two, as we discussed in Atterholt et al. (2024), but it’s not always super clear-cut. I wondered if the structures in the Thecachampsa vert would just be elaborate ridges between the neural and vascular compartments.

Thecachampsa caudal AMNH FR 34089, close-up of the right NCR. Photo by William Jude Hart.

As the photo at the top of the post demonstrates, I should have had more faith in William’s perspicacity as a morphologist. When he sent the photos, my jaw hit the floor. These are the thinnest, spikiest, least ambiguous bony spinal cord supports I’ve seen in any amniote, extinct or extant. They’re up there with the rose-thorn-esque bony spikes in tuna vertebrae (see photos in this post).

Close-up of the right NCR in AMNH FR 34089. The morphology here is complex — there is a longitudinal ridgeline for the NCR itself (red highlight), but it doesn’t extend vert far at all. More interesting to me is the subtle ridge running dorsoventrally on the lateral wall of the canal (blue highlights).

I’m pretty confident that these have nothing to do with separating the supraspinal vein from the spinal cord. For one thing, this Thecachampsa vert does not have a bilobed neural canal. On the contrary, rather than having a longitudinal ridge on the side of the canal, the Thecachampsa caudal has a very subtle transverse ridge running up each side of the canal — highlighted in blue in the photo above — on which the neural canal ridge sits like a fairly abrupt summit. The photos above are closeups of the right NCR, but the same is true on the left, as you can see in the photo at the top of the post. That morphology looks a lot more consistent with bony spinal cord supports than with physically demarcating the canal into upper and lower halves.

My favorite sauropod NCRs, in MWC 10613, a Diplodocus caudal from Bone Cabin Quarry in Wyoming. Nice sharp little ridges about midway along the canal, visible to the naked eye, in CT slices (left), and in a hemisectioned digital model (right).

Also, the Thecachampsa spikes are at about the midpoint of the neural canal, where we tended to find the NCRs in sauropods and other dinosaurs. That makes perfect sense if the bony spinal cord supports are remnants of embryonic myosepta, as hypothesized by Skutschas and Baleeva (2012; see this post for more discussion). The neural arch pedicles form within those myosepta, so if the bony spinal cord supports are also myoseptal remnants, they should be located near the craniocaudal midpoint of each neural arch pedicle, which is just another way of saying “about halfway down the neural canal”. Et voila, so they are, in both Thecachampsa and non-avian dinosaurs.

(Why not just check in extant crocs and see what soft tissues are tethered to these things? We’re working on that. Even if we’re wrong about NCRs being bony spinal cord supports, they’re bony somethings, presumably related to interesting soft tissues, and with anatomical and phylogenetic distributions that are very far from being fully mapped.)

Deinosuchus caudal WSC 285.8 in anterior view. The left NCR is the lower of the two prominences visible on the right side of the canal (the upper is taphonomic damage, the edge of a crack).

Armed with the knowledge that NCRs were present in crocs, I drove out to Hemet to visit the Western Science Center. Andrew McDonald has been digging in the Menefee Formation of New Mexico for years, unearthing cool critters like the tyrannosaur Dynamoterror, the armored Invictarx, the hadrosaur Ornatops (which you’ve seen here before), some turtles (McDonald and Wolfe 2018, McDonald et al. 2018, 2021, Adrian et al. 2025) — and, oh yeah, the gigantic and terrifying Cretaceous croc Deinosuchus (Mohler et al. 2021). Thanks to the kind offices of Andrew and Alton Dooley, a good friend and Haplocanthosaurus partner in crime, I got my mitts on the Menefee Deinosuchus caudals. Two of the three vertebrae that I examined had an NCR preserved on at least one side. The third vertebra, by far the most complete externally, ironically had the worst-preserved neural canal. But the others were enough.

We had all the ammo for this paper about a year ago. William had the original discovery, the nicer specimen, and everything he needed to publish on his own, but he kindly invited me to contribute. We put together — well, William put together, with about 95% of the work — a presentation for the 5th Palaeontological Virtual Congress this spring. We looped in Jessie Atterholt for the paper, and she made a lot of improvements. And here we are.

Where will these things turn up next? Maybe you will be the one to find out. Modified from Hart et al. (2025: fig. 1).

(Incidentally, I created the silhouettes for Figure 1 myself, mostly tracing public domain images but drawing a few on my own. Why not use PhyloPic? Partly my own cussed persnickettiness, and partly because properly crediting 17 people was going to be cumbersome in such a short paper. I should make the originals available for everyone else — watch this space.)

Why do we find NCRs in some taxa but not others? Some animals are prevented from developing them: sharks don’t have a way to ossify their ligament attachments, and the denticulate ligaments of mammals don’t anchor to bone (see this post for more). Also, I suspect that NCRs are like the ossified traces of most muscle, tendon, and ligament attachments, in that they can be present but are not always present, even when the muscle, tendon, or ligament is. But that’s just kicking the can down the road — why do we see prominent NCRs in certain groups, and in certain regions of the vertebral column? We advance a hypothesis in the new paper (p. 752):

NCRs are prevalent in clades with laterally undulating locomotion (e.g., Teleosti; Skutchas and Baleev 2012), tail-driven femur retraction (e.g., Dinosauria; Atterholt et al. 2024), or both (e.g., Urodela; Wake and Lawson 1972), and absent in clades that have more rigid torsos, an absence of tail-driven femur retraction, or both, such as Anura, Aves, and Mammalia (Fig. 1A). This apparent distribution is consistent with the hypothesis that NCRs anchor the spinal cord against lateral undulatory motion.

That’s our best guess right now, but a LOT of work remains to be done. We hint at three fronts in the paper:

1. Discovery

NCRs are turning up all over the place. When we published the first NCR paper last year, they were known in salamanders but not in other lissamphibians. Now they’ve been documented in caecilians, by Santos et al. (2025), which we were able to cite in the new paper. The pace of discovery is rapid, but there is a lot of ground not yet covered. At this point, the number of non-sauropod archosaurs with published NCRs is very small — one individual each of Thecachampsa, Deinosuchus, Allosaurus, Ceratosaurus, Stegosaurus, and an indeterminate hadrosaur — but very suggestive, because Archosauria is a big, diverse clade. Not to mention all the other vertebrates. Someone is going to the be the first to document NCRs in, gosh, all the other things. Tyrannosaurs, anyone?

In particular, you may be thinking that it’s all very well for NCRs to be present in these giant extinct crocs, but what about mortal extant crocs? Stay tuned — we’re working on that, with William leading the charge. He’s a grad student now, pursuing his Master’s at East Tennessee State, and I’m confident you’ll be hearing a lot more about his work in the future.

Thecachampsa caudal AMNH FR 34089 in ventral view. This vert is just shy of four inches long, which if you know crocs, is up in *gulp* territory.

2. Investigating soft tissues

We think the NCRs in crocs and dinos are bony spinal cord supports, but it would be very nice to have that confirmed via dissection. Also, where do the denticulate ligaments attach in vertebrae with bilobed neural canals? Could some of the longitudinal ridges in croc verts be doing double duty, dividing the vascular and neural compartments and anchoring denticulate ligaments at the same time? These are open questions, which are about one dead alligator away from being answered.

Also, as mentioned above, if the NCRs of crocs aren’t bony spinal cord supports, what the heck are they?

3. Biomechanical testing

Assuming NCRs are bony spinal cord supports, is lateral movement of the vertebral column the primary driver in their formation, just one factor among many, or a complete red herring? This is the kind of thing that could easily lend itself to logistically intensive approaches like 3D scanning and modeling, but might also get solved by just, like, pulling on things to see what happens (e.g., Baumel 1985).

Conclusion

If you want to get in on this, it’s a pretty straightforward gig: find some vertebrae, peer in the neural canals, document what you find, tell the world. If you don’t find NCRs you might find pneumatic cavities or blood vessel tracks or some totally new thing to add to the neural canal zoo. There are whole big clades of vertebrates about which we know basically nothing, neural-canal-wise, and opportunities for new discoveries abound — as our new paper shows. Come play.

References

 

doi:10.59350/tdtq9-kt434

Tutorial 48: my museum collections kit

I was on the road for most of August, September, and October, and in particular I made a ton of museum collections visits. When I visit a museum collection, I bring a specific set of gear that helps me get the photos, notes, and measurements that I want. All of this is YMMV — I’m not trying to predict what will work best for you, but to explain what has worked for me, and why. I’m reasonably happy with my current setup, but even after 28 years of museum visits, I’m still finding ways to improve it. Hence this post, which will hopefully serve as a vehicle for sharing tips and tricks.

A word about my program when I visit a collection, because not everyone needs or wants to do things my way. The closest museums with extensive sauropod collections are states away from where I live and work. If I’m in those collections at all, I’m traveling, and therefore on the clock. Time in collections is a zero-sum game: if I have the time to take 20 pages of notes, that could be 4 pages of notes of each of 5 specimens, 2 pages on 10, 1 page on 20, half a page on 40, etc. In practice, I usually make expansive notes early in the visit, one or two spreads per specimen with detailed sketches and exhaustive measurements of the most publication-worthy elements. I grade toward brevity over the course of the visit, and end with a mad desperate rush, throwing in crude sketches and rudimentary notes on as many newly-discovered (by me) specimens as possible. My collections visits are Discovery Time and Gathering Time, trying to get all the measurements and photographs I’ll want for the next year, or five, or forever. And, to the extent that I can suppress them, not Analysis Time or Graphing Time or Writing Time — I can do those things after hours and in my office back home, IF and only if I’ve spent my collections time efficiently gathering all the information I’ll need later.

The very first thing I do in any collection is a walking survey, to make sure I know roughly what specimens the collection contains and where to find them. For a sufficiently large collection — or even a single cabinet with 10 drawers of good stuff — I may draw a map in my notebook, on which I can note things I want to come back and document, and add new things as I find them.

Enough preamble, on to the gear. The first two or three entries here are in strict priority order, and after that things get very fuzzy and approximate.

1. Research Notebook

Seems obvious, right? Write stuff down, make sketches, capture the info that will be difficult or impossible to recapture later from photos. I have encountered people who don’t take a physical notebook, just a laptop or tablet, and take all their notes digitally. If that works for you, may a thousand gardens grow. For me, sketching is a fundamental activity — for fixing morphology in my mind, disciplining myself to see the whole object and its parts, creating a template on which to take further explanatory notes, and capturing the caveats, stray ideas, and odd connections that surround each specimen in a quantum fuzz in my mind (temporarily in my mind, hence the need for external capture). I also write priority lists in advance of specimens to document each day, and then cross them off, add new ones, and strike out duds with wild abandon in the heat of data collection.

I do a few specific things to increase the usefulness of my notebooks:

– Label the spines and covers with the notebook titles and years. These things live on the shelf directly over my desk, and I pull them down and rifle through them constantly. I also have notebooks for university service (committees, student advising, and so on), astronomical observations, and personal journaling, so “Research” is a useful tag for me.

– Number the pages, if they’re not already numbered, use the books chronologically from front to back, and create the table of contents retrospectively as I go — a tip I got from the Bullet Journal method.

– Paste a small envelope inside the back cover, if a pouch is not already built in, to hold all kinds of ephemera — index cards, scale bars, a bandage (just in case), stickers I acquire along the way, etc.

– Affix a section of measuring tape to the outer edge of the front or back cover. I got this tip from the naturalist John Muir Laws, whose Laws Guide to Nature Drawing and Journaling is wonderfully useful and inspiring (UPDATE: that book is now covered in its own post, here). The scale-bar-permanently-affixed-to-research-notebook has been a game-changer for me. Do you know how many times I’ve accidentally left a scale bar on a museum shelf, and then gotten to my next stop and had to borrow or fabricate one? I myself lost count long ago. But never again. If I’m in a hurry, small specimens go straight onto the notebook to be photographed, like the baby apatosaurine tibia above, and the notebook itself goes into the frame with large specimens. (This comes up again — if possible, and it’s almost always possible, put the specimen label in the photo with the specimen. No reason not to, and sometimes a lifesaver later on.)

Behold the thinness of the eminently pocketable IKEA paper tape. Folding instructions, because this seems to bedevil some folks: hold up one end, fold in half by grabbing the other end and bring it up in front, then do that three more times. Finished product is 65mm long, 25.4mm wide, and about 1mm thick when folded crisply and left under a heavy book overnight.

2. Measuring tapes

I find the flexible kind much more convenient and useful than retractable metal tape measures. I like the 1-2mm thick plastic type used by tailors and fabric sellers, because they have just enough inertia to stay where I put them, or drop in a predictable fashion when draped over something sufficiently large, as when measuring midshaft circumference of a long bone.

I LOVE the little plasticized paper tapes that hang on racks, free for the taking, near the entrances of IKEA stores. I tear them off by the dozen when I go to IKEA, cram them in my pockets, fold them flat when I get home, and stash them everywhere, including in my wallet. A few specific reasons they’re great:

– Folded flat, they’re about the thickness of a credit card, so there’s just no reason to be without one. I usually have one in my wallet, another in the envelope at the back of my research notebook, a couple more stashed in my luggage, a couple more stashed in my car, desk, tookbox, nightstand, etc.

– I can write on them. Especially handy if:

– I’ve torn off a section to serve as an impromptu scale bar. Which I never hesitate to do, because they’re free and I have dozens waiting in my toolbox and desk drawers at any one time. Torn off bits also make good bookmarks, classier, more cerebral, and less implicitly gross than the traditional folded square of toilet paper.

– I give them away to folks I’m traveling with, or that I meet in my travels, and they’re usually well-received.

I would NOT have figured out all these laminae if I hadn’t had a way to make them stand out.

3. Writing instruments in various colors

Up until about 2018 my notebooks were always monochrome pen or pencil. Then I realized that color is an extremely helpful differentiator for Future Matt, so now I highlight and color-annotate willy-nilly.

4. Calipers

I borrowed the digital calipers from Colin Boisvert to get the photo up top, having forgotten my own at home. As a sauropod worker, I don’t need sub-millimeter accuracy all the time. But digital calipers have three exceedingly useful functions: measuring the thickness of very thin laminae and bony septa; measuring the internal dimensions of small fossae and foramina; and measuring the depth of fossae and of concave articular surfaces. I also have a little titanium caliper on a lanyard that goes with me most places.

5. Small brush on a carabiner

This is the newest addition to the kit. I got the idea from Matthew Mossbrucker at the Morrison Museum in Morrison, Colorado. Colin and I visited him in September, immediately before our week-long stint in the collections at Dinosaur Journey. Matthew keeps a little brush carabinered to his belt at all times, and the utility was so instantly obvious that when Colin and I rolled into Fruita later that same day, I went to the hardware store and got my own. Cheap, weighs nothing, clips to anything, compact enough to cram in a pocket, good for lab and field alike. Genius!

6. Scale bar

Yes, I have my scale-bar-enhanced research notebook and my hoarder stash of IKEA paper tapes, but good old-fashioned scale bars are still useful, and I use them constantly. And lose them constantly, hence my multiple redundant backup mechanisms.

(Aside: I can’t explain why I hold onto some objects like grim death, but let others fall through my fingers like sand grains. I’ve only lost one notebook of any kind in my entire life — set it on top of the car while packing and then drove off [grrrr] — so I have no problem investing in nice notebooks and treating them like permanent fixtures. But I can’t hang onto pens and scale bars to save my life, hence my having gravitated to Bic sticks and IKEA paper tapes.)

7. Index cards

I try to get as much information into each photograph as possible. Ideally alongside the specimen I will have:

– a scale bar at the appropriate depth of field;

– the specimen tag with the number, locality, and other pertinent info;

– my notebook open to my sketch of the specimen, for easy correlation later (I don’t do this for every single view, just the ones that I think are particularly publication-worthy, or have info I’m likely to forget later);

– anything else I might want — serial position, anatomical directions, whether the photo is part of an anaglyph pair, and so on — written on an index card, which being a standard size will itself serve as an alternate/backup scale bar.

8. Pencil case

To hold all the smaller fiddly bits you see in the photo up top. I can’t now fathom why, but I resisted getting one of these for a loooong time. I was young and foolish then. Pretty useful all the time, absolutely clutch when it’s 4:58 pm and I’m throwing stuff in bags, caught between the Scylla of working as late as possible and the Charybdis of wanting to be polite to whatever kind, patient person is facilitating my visit. That is also when the pocket in the back of the notebook comes in especially handy.

Headlamp in action, casting low-angle light on a pneumatic fossa on the tuberculum of this sauropod rib. Note also the scale bar, elevated on a specimen box to be the same depth of field, and the notebook open to my sketch of the specimen.

9. Artificial lighting

This was another very late discovery for me — I don’t think I was regularly bringing my own lights prior to 2018. For me, portable, rechargeable lighting is useful in many circumstances and absolutely critical in two: casting low-angle light to pick out subtle pneumatic features, as in the photo above, and lighting up big specimens that I don’t have the time, energy, or space to pull off the shelves, as in the photo below.

I’m particularly taken with the big orange fan/light combo. It charges using a USB-C cable, has four settings for fan speed (handy when it’s hot, humid, or just oppressively still) and three for light intensity, a rotating hook that folds flat, and a USB power-out socket for charging phones, headlamps, fitness trackers, and what have you. I use it practically every day whether I’m on the road or not.

Magnetic flashlight hanging from steel shelving to illuminate Camarasaurus cervical vertebrae in the Utah Field House collections.

Whether it’s a hook or a magnet, some kind of mechanism for suspending a light at odd heights and angles is super useful. I usually have a strong flashlight with an integral seat-belt cutter and window-smasher in the door pocket of my car, and its magnetic base makes it omnidirectionally functional in collections spaces, which are usually liberally supplied with steel in the form of shelving and cabinets.

Haplocanthosaurus CM 879 caudal 2 in left lateral view, with rolled-up paper neural canal visualizer and scale-bar-stuck-to-flashlight.

Sometimes I use a bit of blue tack to stick a scale bar to a flashlight, to create a free-standing, truly vertical scale bar that I can rapidly place at different distances from the camera. Beats leaning the scale bar against a stack of empty specimen boxes or a block of ethofoam (which in turn beats nothing at all).

What else?

USUALLY — Laptop

Not for recording notes or measurements — all of that goes into the notebook, which I scan and upload new stuff from every evening. Mostly for displaying PDFs of descriptive monographs, and hugely useful in that regard.

MAYBE — Monographs

When I have the freedom (= baggage allowance) to do so, I find it handy to bring hardcopies of descriptive monographs, both for quick reference and so I can photograph specimens alongside the illustrations. Doesn’t even have to be the same specimens, just comparable elements. In the photo above, MWC 7257, a partial sacral centrum of Allosaurus from the Mygatt-Moore Quarry, is sitting next to a plate from Madsen (1976), illustrating the same vertebra in a specimen from Cleveland Lloyd Dinosaur Quarry. Thanks to Colin Boisvert for bringing the specimen to my attention — I’ve got a longstanding thing for sacrals — and for loaning me his copy of Madsen (1976) for this photo.

OUT — Camera and tripod

I suspect that some folks will shake their heads in mute horror, but after a couple of decades of lugging dedicated cameras and tripods everywhere, I stopped. For the past few years I’ve been rolling with just my phone, which is objectively better than any dedicated camera I owned for the first half of my career. Sometimes I brace it in an ad hoc fashion against a chair or shelf or cabinet, but mostly I just shoot freehand. For my purposes, it does fine, and any minor improvements in field curvature or whatever that I’d get from a dedicated camera don’t outweigh the logistical hassle. Again: YMMV!

Over to you

So, that’s what I roll with right now. It was different six months ago, and will almost certainly be a little different six months hence, hopefully as a result of people responding to this post. With all that said: what’s in your kit?

P.S. Many thanks to Matthew Mossbrucker and Julia McHugh for their hospitality and assistance in their collections, and to Colin Boisvert for being such a great travel companion, research sounding board, and generous loaner-of-things-I’d-forgotten. The Wedel-Boisvert Morrisonpocalypse 2025 deserves more blogging.

 

doi:10.59350/c21vr-f8727

5th Palaeontological Virtual Congress: Neural canal ridges in crocs

When our paper on neural canal ridges came out last year (Atterholt et al. 2024), I hoped that it would inspire other people to go peer inside neural canals and discover a lot more of them. My wish was granted, and quickly. In early October I was contacted by William Jude Hart, then an undergrad at Hofstra University in New York (he graduated in December). He was making a poster for the upcoming SVP meeting on a specimen of the large tomistomine crocodilian Thecachampsa, specifically an anterior caudal vertebra with pretty darned unambiguous neural canal ridges:

Since then we’ve found more examples, in both extinct and extant crocodilians, and William invited me to be his coauthor on the description. Our first salvo, Hart and Wedel (2025), is a slide presentation at the 5th Palaeontological Virtual Congress, which is going on right now. Find us in the thematic session, “Unraveling crocodylomorph evolution: insights from fossils and new methodologies“. All of the 5PVC presentations will be up for another week, and registration is measly 5 Euros, so if you’re curious about our findings — and a great many other fascinating paleo things — go check it out.

More 5PVC news shortly. And if you’re interested in neural canal ridges, or neural canal anything, or pretty much any kind of anatomy whatsoever, I have good news: there are tons of things waiting to be discovered by curious folks. I mean, heck, the first neural canal ridges in crocs — not an obscure or understudied clade — were found by an observant undergrad.

Come play.

References

 

doi:10.59350/emkfz-7sa26

My Constant Reader, and staying close to the work

A middle caudal vertebra of a diplodocid, presumably Tornieria africana, on display at the Museum fur Naturkunde Berlin, in left lateral view.

Quick backstory: this post at Adam Mastroianni’s Experimental History led me to this post at Nothing Human, and poking around there led me to another good’un: “Shallow feedback hollows you out”. That post really hit for me, and it made me think about SV-POW! Especially this bit:

Suppose you don’t want to lose your ability to think new thoughts and see new things. What are your options?

The best remedy is to write to the single smartest person you know who cares a lot about your topic of interest.

I have two thoughts about this. The first, which dovetails nicely with the thesis of that post, is that SV-POW! staying relatively small is probably a good thing. We’ve never written with the goal of growing our readership, and I think that’s kept us from being tempted by a lot of bad habits whose deleterious effects you can see play out over and over again across the whole internet. Our habit of posting on a completely irregular schedule on whatever topics we like has been doubly beneficial: it’s kept us sane (for reasons explored in this post), and it’s probably kept our readership low,* which has kept the temptation to write for marginal readers from ever getting off the ground. In case that sounds insulting or dismissive to our readers, let me clarify: we love our readers, and we’d rather have our little community of dedicated weirdos than any other set.

(Don’t get me wrong, I like it when one of our posts goes viral, but I like it in the same sense that I like watching a comet: it’s a cool phenomenon that I feel is beyond my influence. I enjoy it, but it doesn’t affect how I conduct myself.)

*Having written that, I wonder now if our irregular posting schedule has possibly deepened the dedication of those readers who can tolerate it — it could be a form of intermittent reinforcement, which has been implicated in gambling addiction.

That leads to my second thought: at any given time in the 17-year history of this blog, we’ve had a small but dedicated cadre of commenters, but the makeup of that group has changed over time. This has also had a salutary effect: for every post I’ve ever written here, I could be pretty sure that at least some of the regulars would see it and comment, but the one thing of which I could be absolutely certain is that the post would be seen and read by Mike. For most posts, Mike probably cares as much or more about what I’m writing than anyone else in the world, he will absolutely call me to account if he catches any weaknesses of evidence or reasoning, and he’ll do it publicly, in our own comment section. These are all good things! As my Constant Reader, Mike’s helped enforce the good habits of mind and of writing that are the subject of that Nothing Human “Shallow feedback” post.

The same Tornieria vertebra in dorsolateral oblique view, showing some pneumatic features on the lateral aspect of the neural spine. The pocks on the centrum are also raising my pneumaticity antennae, but I can’t be sure from my limited set of 16-year-old photos. When Diplodocus caudals have pneumatic features this far back in the tail, they’re more commonly on the centrum than the arch, but diverticula gonna diverticulate.

Speaking of, I also really liked this bit from the first comment on that post, by Mo Nastri:

…the details change but the general pattern is the same. In each case the [once great] intellectual in question is years removed from not just the insights that delivered fame, but *the activities that delivered insight*.

To the extent that this blog has escaped enshittification, it’s probably because Mike and I are not removed from the activities that deliver insight. We care more about sauropod vertebrae (and pig skulls, etc.) than we do about clicks. And at this point, I’m confident that we always will. If we were ever in danger of click-maximizing behavior, it was probably back in the early days, and even then the risk was minimal. We love our weird little niche blog just as it is, weird and niche-y and little.

The possibly-surprising conclusion I’m building toward is that we’ve probably made SV-POW! a better experience for our readers (minimally, in that it still exists to be read) by not caring about our readership, and by not writing to please or impress anyone other than ourselves and each other. And that in turn has kept SV-POW! viable for us as well.

So if you’re here, great! We’re happy to have you — as an interested person, rather than a click. If you like what we’re doing, stay tuned. We’re gonna do a lot more of the same.

 

doi:10.59350/sbt1j-ttm80

If I could dissect a sauropod…

Luke Horton asked in a comment on a recent post:

Given the chance to examine a titanosaur cadaver with your hypothetical army of anatomists, what would you look for first?

*FACEPALM* How we’ve gone almost 17 years without posting about a hypothetical sauropod dissection is quite beyond my capacity. I am also contractually obligated to remind you that the TV show “Inside Nature’s Giants” shows dissections of a whale, elephant, giraffe, tiger, anaconda, giant squid, etc., so it’s probably the closest we’ll ever get. Go look up photos of Dr. Joy Reidenberg standing, um, amidst a partially-dissected whale, or just watch that episode, and your sauropod-dissection-visualizer will be properly calibrated.

To get back to Luke’s question, there are loads of interesting things that could be dissected in a sauropod, but since the remit here is Matt Wedel x titanosaur, there’s only one possible answer: the lung/air sac system and its diverticula. For several reasons:

Hypothetical reconstruction of the lungs (red) and air sacs (blue, green, and gray) in Haplocanthosaurus CM 879. I’d love to know how close this is to reality. Wedel (2009: fig. 10).

First and most obviously, I’ve spent the last quarter-century trying to infer as much as possible about the respiratory systems of sauropods based on the patterns of pneumaticity in their skeletons, and I’d kill for the opportunity to check the accuracy of my inferences — and those of all my fellow-travelers in the sauropod and dinosaur respiration biz, like Daniela Schwarz and Emma Schachner and Tito Aureliano and many others.

Sauropod respiratory system modeled on that of a bird. I’ll bet the correspondence wasn’t this close. (Also, since making this figure 20 years ago, I’ve learned that the abdominal air sacs of ostriches are actually rather small, although the perirenal, femoral, and subcutaneous diverticula of the abdominal air sacs are extensive; see Bezuidenhout et al. 1999). Wedel and Cifelli (2005: fig. 14).

Second, I am intrigued/haunted by the possibility that extant birds might not represent the apex of saurischian lung/air sac evolution. Birds survived the K-Pg disaster because they were small; respiratory efficiency had little or nothing to do with it (evidence: all the other small-bodied tetrapods that survived, like the many, many squamate and mammalian lineages). To me it would be a wild coincidence if the tiny dinosaurs that survived also just happened to be The Bestest (TM) at some anatomical/physiological thing unrelated to their survival. In fact, given how sensitive birds are to airborne dust and ash, I wonder if their fancy lungs weren’t more of a hindrance than a help in the dusty, sooty, iridium-laced post-impact world. Anyway, there are interesting clues that the air sac systems of extant birds are just one subset of a much greater original diversity, like most (all?) birds starting out embryologically with a dozen or so air sacs, which get simplified to the usual 9 or fewer by fusions. What did other dinosaurs do with their 12 (or more?) air sacs? If any dinosaurian clade was going to push the capabilities of the “avian” lung/air sac system in interesting directions and to fascinating extremes, sauropods seem like a good bet.

Rib articulation angles in the dorsal vertebrae of (a) Lufengosaurus, (b) Diplodocus, (c) Haplocanthosaurus, (d) Tyrannosaurus, and (e) an ostrich. Anterior is to the right. Diplodocus and Haplocanthosaurus are pretty wildly different considering they coexisted in the Morrison. I really gotta write a whole post about that. Boisvert et al. (2024: fig. 12).

So I’m intrigued by the idea that extant birds show us one way that a saurischian lung/air sac system can work, but don’t exhaust the territory, anymore than kangaroos show us all the ways that mammals can reproduce. Maybe sauropods had even better lungs than birds! Or maybe not. Likely they were doing their own weirdly specialized thing — or many weirdly specialized things — that left few to no diagnostic traces in their skeletons. We can be pretty confident that at least some of the pneumatic diverticula of sauropods worked essentially identically to how they do in birds (see Woodruff et al. 2022 and this post), and mid-dorsal pneumatic hiatuses in juvenile sauropods — predicted by me in 2003, found by Melstrom et al. (2016) and Hanik et al. (2017) — suggest that their air sac systems were broadly comparable. On the other hand, the variety of rib articulation angles just within Morrison sauropods tells us they weren’t all ventilating their air sacs in quite the same way (Boisvert et al. 2024), despite broad similarities with other dinos at the levels of rib osteology (Wang et al. 2023) and whole-thorax construction (Schachner et al. 2009, 2011). (Aside: why the hell didn’t I work a citation of Wang et al. 2023 into the Dry Mesa Haplo paper? I can only conclude that I am at least occasionally an idiot.) Whatever was going on, I’m pretty sure sauropods didn’t look exactly like 60-ton turkeys on the inside, but we don’t have a ton of real data on how they differed. It would be amazing to find out.

The mounted Rapetosaurus skeleton at the Field Museum, traced from a photo. Specific weird things to note: neck about twice as long as tail, cervical vertebrae about twice as tall as dorsals, and smallish pelvic bones relative to hindlimbs (= skinny posterior abdomen, at least dorsoventrally). See this post for details.

Third, if any sauropods were going to rival or exceed birds in fancy under-the-hood anatomical and physiological adaptations, my money would be on titanosaurs. They were morphologically disparate, phylogenetically diverse, geographically widespread, they independently evolved to giant size more times than any other sauropod clade, and their growth rates were wild. I’d dissect any sauropod I got access to (uh duh), but a titanosaur would be particularly appealing. Which titanosaur? Probably Rapetosaurus: we know it grew very fast early on (Curry Rogers et al. 2016, and see implications for the nervous system in Smith et al. 2022), it had a highly pneumatic vertebral column (O’Connor 2006), its body proportions were pretty wacky, and it had other features of interest to me, like expanded neurocentral joints (see Wedel and Atterholt 2023 and this post) and neural canal ridges (see Atterholt et al. 2024 and this post).

I used this photo of a Rapetosaurus caudal vertebra a few posts ago to illustrate the neural canal ridges, but — like many other sauropods — it also has very expanded neurocentral joints forming boutons. From Curry Rogers (2009: fig. 27).

Oh, and if I got to dissect more than one sauropod, the rest of my top 5 choices in order would be:

  • the owner of BYU 9024 (Supersaurus? Giant ancient individual of Barosaurus? Are those even different things? Dissecting this critter could tell us!), Barosaurus being the most diplodocid-y and least titanosaur-y neosauropod I know of, and BYU 9024 being from a hellaciously big individual no matter what its classification;
  • the Snowmass Haplocanthosaurus, because I have just so many questions about all the weird stuff going on with its tail (see Wedel et al. 2021 and this post for starters); 
  • Omeisaurus or Xinjiangtitan, to represent a maximally derived-but-also-weird non-neosauropod;
  • Sauroposeidon, for obvious emotional reasons (but not enough to dethrone the others).

After that? Probably Isanosaurus or Melanorosaurus or something else waaaay down the tree, so I could see how much of the sauropod kit was in place from the get-go (probably most of it).

Bone vs joint space in the proximal caudals of the Snowmass Haplocanthosaurus. I’d give one non-essential organ to dissect that tail!

And after the respiratory system, next up for me would be the spinal cord and any related morphological specializations of the neural canal — see Table 3 in Atterholt et al. (2024) for a running tally, and this page. Then intervertebral joints, digestive tract, and reproductive system (neither of the last two leave anything useful in the way of skeletal traces), in that order. Arguably the intervertebral joints would be a bigger score for sauropod paleobiology than spinal cord stuff, but maybe not, and having squelched my emotional pick among sauropod taxa, I’m letting my emotions rule when choosing body systems to dissect. I also am intensely interested in the possibility of protofeathers in sauropods, but you don’t have to dissect those, you can just see if any are present, so I’d cheat a little and note any integumentary specializations en passant. (Remember than an animal can have hairs without being hairy [naked mole rats, rhinos, manatees, dolphins], ditto for feathers.)

So that’s the sauropod and the body system I’d dissect first, if given the chance. What’s your answer?

References

 

doi:10.59350/ajsh7-42642