Aquilops skull, take 3

December 12, 2018

Nothing really new here, not like a new skull recon or anything. The original version I did for Farke et al. (2014) had the jaw articulated and closed. Then in 2017 I posted a version with the lower jaw disarticulated. Obviously what was needed was one with the lower jaw articulated and open. Now it exists, here. I mean, since I posted the separate parts last year people have had everything they needed to make their own, but it’s nice to have one already built, so here you go.


Here’s a frozen pig head being hemisected with a band saw.

The head in question, and the other bits we’ll get to later on in this post, both came from Jessie Atterholt’s Thanksgiving pig. As soon as Jessie knew she was cooking a pig for Thanksgiving, she had a plan for the head and the feet: cut ’em in half, skeletonize one half (like Mike did with his pig head), and plastinate the other. Jessie has her own plastination setup and you can see some of her work in her Instagram feed, here.

Here’s the freshly hemisected head. At one time or another, about four of us were involved in checking the alignment of the cut, with the intention of just missing the nasal septum (it can be easier to see some of the internal nasal anatomy if the septum’s all on one side). But we were all wrong–not only did the saw hit the nasal septum dead on, it hemisected the septum itself. Which I guess is the next-best possible outcome. The septum is the big expanse of white cartilage behind the nose and in front of the brain. You have one, too–it separates your left and right nasal cavities–but yours is a lot thinner.

Here’s the left half washed off and cleaned up a bit.

I was completely entranced by the little blood vessels inside the nasal septum, seen here as tiny traceries of red inside the blue-white cartilage. Also notice the frontal sinus above the septum and in front of the brain.

Here’s the right half in a postero-medial oblique view. Shown well here are the first two cervical vertebrae, plus part of the third, and the intervertebral joints. This was a young pig and the remains of growth plates are still visible between the different ossification centers of the vertebrae. If I get inspired (= if I get time) I might do a whole post on that.

It wasn’t my pig or my show, but Jessie made me a gift of two pig feet, and I got a little time on the saw. Here I’m using a plastic tool to push one of the pig’s hind feet through the saw.

We had been dithering over how best to prep the feet but the lure of the band saw proved irresistable: we hemisected all four. We’re planning to do half skeletonized/half plastinated preps for all of them, a forefoot and a hindfoot set for each of us.

Jessie and I were joined by two other WesternU anatomists, Thierra Nalley and Jeremiah Scott. Here Thierra is explaining to Jeremiah, who works on primate dentition and diet, that mammals have more parts than just teeth.

That’s a good segue to this video I shot, in which Thierra gives a quick tour of the hemisected pig head. All four of us have just come off of teaching human head and neck anatomy, so it was cool to see in another mammal the same structures we’ve just been dissecting in humans.

From 1:40 to 1:55 in the video Thierra and I are discussing the prenasal bone, something pigs have that we don’t. It’s the separate bone at the end of the snout in this mounted skeleton:

Darren discusses and illustrates the prenasal bone in this Tetrapod Zoology post.

Parting shots: many thanks to Ken Noriega and Tony Marino of WesternU’s College of Veterinary Medicine for their guidance, assistance, and expertise. Jessie covered this dissection as an Instagram story, here–I believe you have to be signed in to see it. Update: Jessie added a regular stream post, with lots of features labeled, here. I’ll probably have more to say about this pig and its bits in the future. Stay tuned!

For more hemisected heads and skulls, see:

Coproliteposting time!

October 28, 2018

I wasted some time today making memes. I blame the Paleontology Coproliteposting group on Facebook.

Of course I started out by making fun of the most mockable sauropod. This one’s for you Cam-loving perverts out there. You know who you are.

This one was inspired by the thiccthyosaur meme, which irritatingly enough I cannot find right now. Oh no, wait, here it is.

I’m laughing through the tears.

For previous adventures in meme-ing, see this post.

In a comment on the last post, Mike wrote, “perhaps the pneumaticity was intially a size-related feature that merely failed to get unevolved when rebbachisaurs became smaller”.

Caudal pneumaticity in saltasaurines. Cerda et al. (2012: fig. 1).

Or maybe pneumaticity got even more extreme as rebbachisaurids got smaller, which apparently happened with saltasaurines  (see Cerda et al. 2012 and this post).

I think there is probably no scale at which pneumaticity isn’t useful. Like, we see a saltasaurine the size of a big horse and think, “Why does it need to be so pneumatic?”, as if it isn’t still one or two orders of magnitude more massive than an ostrich or an eagle, both of which are hyperpneumatic even though only one of them flies. Even parakeets and hummingbirds have postcranial pneumaticity.

Micro CT of a female Anna’s hummingbird. The black tube in the middle of the neck is the supramedullary airway. Little black dots in the tiny cervical centra are air spaces.

We’re coming around to the idea that the proper way to state the dinosaur size question is, “Why are mammals so lousy at being big on land?” Similarly, the proper way to state the pneumaticity question is probably not “Why is small sauropod X so pneumatic?”, but rather “Why aren’t some of the bigger sauropods even more pneumatic?”

Another thought: we tend to think of saltsaurines as being crazy pneumatic because they pneumatized their limb girdles and caudal chevrons (see Zurriaguz et al. 2017). Those pneumatic foramina are pretty subtle – maybe their apparent absence in other sauropod clades is just because we haven’t looked hard enough. Lots of things have turned out to be pneumatic that weren’t at first glance – see Yates et al. (2012) on basal sauropodomorphs and Wedel and Taylor (2013b) on sauropod tails, for example.

Back of the skull of a bighorn sheep, showing the air spaces inside one of the broken horncores.

Or, even more excitingly, if the absence is genuine, maybe that tells us something about sauropod biomechanics after all. Maybe if you’re an apatosaurine or a giant brachiosaurid, you actually can’t afford to pneumatize your coracoid, for example. One of my blind spots is a naive faith that any element can be pneumatized without penalty, which I believe mostly on the strength of the pneumatic horncores of bison and bighorn sheep. But AFAIK sauropod girdle elements don’t have big marrow cavities for pneumaticity to expand into. Pneumatization of sauropod limb girdles might have come at a real biomechanical cost, and therefore might have only been available to fairly small animals. (And yeah, Sander et al. 2014 found a pneumatic cavity in an Alamosaurus pubis, but it’s not a very big cavity.)

As I flagged in the title, this is noodling, not a finding, certainly not certainty. Just an airhead thinking about air. The comment thread is open, come join me.


Juvenile Tomistoma schlegelii, LACM Herpetology 166483, with me for scale. It wasn’t until I picked up the skull that I realized it was the same specimen I had looked at back when. I was looking at its neck in 2011, and its tail today, for reasons that will be revealed at the dramatically appropriate moment. I was only playing with the skull because it’s cute, an intricate little marvel of natural selection. Photos by Vanessa Graff (2011) and Jessie Atterholt (2018). Many thanks to collections manager Neftali Camacho for his hospitality and assistance both times!

John Yasmer, DO (right) and me getting ready to scan MWC 8239, a caudal vertebra of Diplodocus on loan from Dinosaur Journey, at Hemet Valley Imaging yesterday.

Alignment lasers – it’s always fun watching them flow over the bone as a specimen slides through the tube (for alignment purposes, obviously, not scanning – nobody’s in the room for that).

Lateral scout. I wonder, who will be the first to correctly identify the genus and species of the two stinkin’ mammals trailing the Diplo caudal?

A model we generated at the imaging center. This is just a cell phone photo of a single window on a big monitor. The actual model is much better, but I am in a brief temporal lacuna where I can’t screenshot it.

What am I doing with this thing? All will be revealed soon.

We don’t post on pterosaurs very often, but I’m making an exception for Caelestiventus. Mostly because I had the unusual experience of holding a life-size 3D print of its skull a few days before it was published. Brooks Britt and George Engelmann are both attending Flugsaurier 2018 in Los Angeles, and Brooks gave a talk on the new pterosaur on Friday. It’s from the Upper Triassic Saints & Sinners Quarry in far northeastern Utah, which has also produced theropods, sphenosuchian crocs (like 80 individuals to date, no exaggeration), drepanosaurs (I’ve seen the material and that paper is going to be mind-blowing whenever it arrives), and other assorted hellasaurs. Some of that material is figured in the Britt et al. (2016) paper on the Saints & Sinners Quarry (a free download from the link below). As far as I know, the Caelestiventus paper is the second big volley on the Saints & Sinners material, out of what will probably be a long stream of important papers.

Anyway, since we’ve just been discussing the utility of 3D printing in paleontology (1, 2), I thought you’d like to see this. Brooks did caution us that the 3D model was a work in progress, and he now thinks that Caelestiventus had a more convex dorsal skull margin, with the downward forehead dip in the version that got printed being less prominent or absent. You can see a slightly different version in the skull recon drawn by second author Fabio M. Dalla Vecchia, which he kindly released into the public domain here.

Otherwise the 3D print is pretty good. The big plate below the orbit is weird and from what I gather not present in other dimorphodontids. Because the Saints & Sinners material was buried in sand, which is relatively incompressible compared to mud and clay, it’s all preserved in three dimensions with essentially no crushing. Caelestiventus therefore yields new information about Dimorphodon micronyx, which has been known since 1859 but mostly from pancaked material.

Stay tuned (in general, not here necessarily) for more on the remarkable tetrapods of the Sants & Sinners Quarry – the next few years are going to be very exciting. And since this may be my first and last Flugsaurier post, many thanks to the organizers for making it such an engaging and enjoyable experience, especially Mike Habib, Liz Martin-Silverstone, and Dave Hone.