In short, no. I discussed this a bit in the first post of the Clash of the Dinosaurs saga, but it deserves a more thorough unpacking, so we can put this dumb idea to bed once and for all.

As Marco brought up in the comments on the previous post, glycogen bodies are probably to blame for the idea that some dinosaurs had a second brain to run their back ends. The glycogen body is broadly speaking an expansion of the spinal cord, even though it is made up of glial cells rather than neurons — simply put, help-and-support cells, not sensory, motor, or integration cells. When the spinal cord is expanded, the neural canal is expanded to accommodate it; as usual, the nervous system comes first and the skeleton forms around it. This creates a cavity in the sacrum that is detectable in fossils.

avian lumbosacral specializations - glycogen body

Giffin (1991) reviewed all of the evidence surrounding endosacral enlargements in dinosaurs (primarily sauropods and stegosaurs) and concluded that the explanation that best fit the observations was a glycogen body like that of birds. I agree 100%. The endosacral cavities of sauropods and stegosaurs (1) expand dorsally, instead of in some other direction, and (2) expand and contract over just a handful of vertebrae, instead of being more spread out. Of the many weird specializations of the spinal cord in birds, the glycogen body is the only one that produces that specific signal.

If any part of the nervous system of birds and other dinosaurs might be described as a ‘second brain’, it wouldn’t be the glycogen body, it would be the lumbosacral expansion of the spinal cord, which really is made up of neurons that help run the hindlimbs and tail (more on that in this previous post). But there’s nothing special about that, it’s present in all four-limbed vertebrates, including ourselves. Interestingly, that bulk of extra neural tissue in the sacral region of birds was referred to as a sort of ‘second brain’ by Streeter way back in 1904, in reference to the ostrich, but it’s clear that he meant that as an analogy, not that’s it’s literally a second brain.

So to sum up, a gradual expansion of the spinal cord to help run the hindlimbs and tail IS present in dinosaurs — and birds, and cows, and frogs, and us. But if that qualifies as a ‘second brain’, then we also have a ‘third brain’ farther up the spinal cord to run our forelimbs: the cervical enlargement, as shown in the above figure. These spinal expansions aren’t actual brains by any stretch and referring to them as such is confusing and counterproductive.

The sharp expansion of the neural canal over just a few vertebrae in birds does not house a ‘second brain’ or even an expansion of the neural tissue of the spinal cord. It contains the glycogen body, which is not made of neurons and has no brain-like activity. The sacral cavities of non-avian dinosaurs replicate precisely the qualities associated with the glycogen bodies of birds, and there’s no reason to expect that they contained anything else. That we don’t know yet what glycogen bodies do, even in commercially important species like chickens, may make that an unsatisfying answer, but it’s what we have for now.

The next installment will be way weirder. Stay tuned!


  • Giffin, E.B.,1991. Endosacral enlargements in dinosaurs. Modern Geology 16: 101-112.
  • Streeter, G.L. 1904. The structure of the spinal cord of the ostrich. American J. Anatomy 3(1): 1-27.

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.

My good friend, frequent collaborator, and fellow adventurer Brian Engh has won the John J. Lanzendorf Paleoart Prize for 2D paleoart (there are also categories for 3D paleoart and scientific illustration). He’s in august company; previous Lanzendorf winners include luminaries like John Gurche, Michael Skrepnick, Mark Hallett, Todd Marshall, and Julius Csotonyi (among many others–see the complete list of previous winners here). Naturally I’m happy as heck for Brian, and immensely proud of him, not only for the award, but also for what he’s doing now. Usually when we say “pay it forward” we mean metaphorically, but Brian is literally going to pay it forward. He’s created his own paleoart contest, the SummonENGH 2018, and he will award half of his October Patreon take to the winner.

He lays out the rules on his blog and in this video:

There’s a Facebook group, here, and a hashtag: #TheSummonEngh2018 (Facebook, Twitter).

Why do I think this is cool? It’s no exaggeration to say that I am a paleontologist today because I was exposed to mind-bending paleoart from a young age. Brian cares about paleoart–he cares about making better paleoart, himself, and he cares about making paleoart better, for everyone. And now he’s putting his money where his mouth his and doing something to hopefully bring more visibility to the paleoart community, and help move the field forward. That’s admirable, and I’m happy to support the cause.

Also, when we visited the Aquilops display at Dinosaur Journey this summer, we were lucky enough to capture this single frame showing a 100% real paleo-energy discharge. I definitely felt something at the time, but I didn’t know the full extent of what had happened until Brian sorted through our photos after the trip. Apparently this was all fated to happen–some kind of transdimensional chronoparticle emission linking past and future–and who am I to argue with fate?

Now, go summon monsters!

I was back in Utah the week before last, looking for monsters with Brian Engh and Jessie Atterholt. It was a successful hunt – more about that another time.

We made a run to Fruita, Colorado, to visit Dinosaur Journey. I was just there in May, picking up Haplocanthosaurus caudals for CT scanning (and other fun things). We picked up another specimen this time, for a different project – more on that in another post, too.

Not this one, but like this one. An apatosaurine middle caudal vertebra, MWC 5742, in left lateral view.

There’s a nice ceratopsian exhibit up at Dinosaur Journey right now, with cast skulls from many of the new ceratopsians that have been described in the past couple of decades. My near-favorites were Zuniceratops and Diabloceratops, both of which are small enough that they must have been adorable in life (think pony-sized and big-horse-sized, respectively).

My absolute favorite, of course, was this little thing:

I can tell you exactly how Aquilops came to be on display there. Julia McHugh printed a copy of the holotype, because it’s freely available to the world. And she used Brian’s Aquilops head recon in the signage (correctly, with attribution), because it’s also freely available to the world. In fact, I’ve seen Aquilops on display at several museums now for just those reasons. So, folks, if you want your critters to be seen, make them open. Hiring a paleoartist to do some awesome artwork that can be released under a CC-BY license (because you paid them, not because you asked them to give their art away for “exposure”) is a huge help.

We had to geek out a little about unexpectedly finding ‘our’ dinosaur on display:

But of course it is not our dinosaur anymore – that’s the whole point. Aquilops belongs to the world.

For more on our trip, see Jessie’s posts herehere, and here.

I’ve known who Peter Doson was since I was nine years old. A copy of The Dinosaurs by William Stout and William Service, with scientific content by Peter, showed up at my local Waldenbooks around the same time as the New Dinosaur Dictionary – much more on The Dinosaurs another time. Then when I started doing research as an undergrad at the University of Oklahoma, Peter’s chapter on sauropod paleobiology in The Dinosauria (Dodson 1990) was one of the first things I read. At the SVP banquet in 2000, I ran into Peter and he shook my hand and said, “Sauroposeidon rocks!” I managed not to swoon – barely.

When I was in Philadelphia this March, Peter invited me to the UPenn vet school for an afternoon. He gave me a tour of the building with its beautiful lecture halls and veterinary dissection lab, and then we spent a couple of hours rummaging around in his office. That was one of the highlights of the trip, because it turns out that Peter and I are both comparative anatomy junkies. He’s been at it for longer, and he has more regular access to dead critters and more space to display them, so his collection puts mine to shame. But he kindly let me play with study whatever I wanted.


In fact, he went farther than that: he quizzed me. A lot. I take it that it’s a right of passage for people coming through Peter’s office. It was an enjoyable challenge, and I got photos of a few quiz items so you can play, too. This transversely-sectioned skull was one of the first mystery specimens. I figured it out pretty quickly, for reasons I’ll reveal in a future post. Can you? Post your IDs in the comments.

I don’t remember all of the quiz items. One of them was the dark skull lying upside down behind the ratite skeleton in the photo up top. I had to figure that one out without picking it up, so you have about as much information as I did. We’ll call that one quiz item #2. Embiggenate for all the clues you’ll need.

This wasn’t a quiz item, just something cool: the skull of a large dog with the top of the cranium removed. In the paired cavities at the top, we’re looking down through the frontal sinuses to see the respiratory turbinates in the nasal cavities. The single large space behind is the braincase. At the very front, in the shadowed recess, you can see the cribriform plate of the ethmoid bone, perforated with dozens of holes to let the olfactory nerve endings through from the back of the nasal cavities. We have the same thing on a smaller scale a centimeter or two behind our brows, and oriented horizontally. But what really drew my attention were the linear arrays of paired foramina arcing across the floor of the braincase – holes to let cranial nerves and the internal jugular veins out of the skull, and the internal carotid arteries in. We have the same structures in our heads, of course, but the layout isn’t as neat – our big brains, bent forward at such a sharp angle from the spinal cord, have squished things around a bit.

Here are more skulls, garnished with a human femur and a ratite pelvis and synsacrum. Peter quizzed me on the Archaeoceratops (front) and Auroraceratops (back) skulls on the far right. I IDed them correctly, but only because I spent some quality time with the Alf Museum’s casts when I was reconstructing the skull of Aquilops. On the far left is an alligator skull with injected arteries, which is definitely worth a closer look.

Here’s a dorsal view of the injected alligator skull. The arteries have been injected with red resin, and then all of the soft tissue has been macerated away, leaving just the bone and the internal cast of the arterial tree. Some of the midline bone has been removed here to reveal the courses of the cerebral, ethmoid, and nasal arteries. Also note the artery looping around in the left supratemporal fenestra.

Here’s a look into the right side of the back of the skull, where the lateral wall of the braincase has been Dremeled away to show the course of the internal carotid artery. It’s a very cool demonstration of a bit of anatomy that I had never seen before. For more on cranial blood vessels in crocs, check out the obscenely well-illustrated recent paper by Porter et al. (2016).

To my chagrin, that’s all the good photos I got from Peter’s office – we were too busy passing specimens back and forth and frankly geeking out like a couple of kids. One of my favorite specimens from his office was the mounted foot skeleton of a horse, which Jessie Atterholt had prepared for him when she was his student at UPenn. It’s such a cool preparation that it captured my imagination, and when I got back I warned Jessie that if she didn’t get her own articulated horse foot posted soon, I was going to make something similar for myself and steal her thunder. A couple of months later, her horse foot is up on Instagram – I featured it in this post – and my cow foot is still sitting in pieces, waiting for me to put it together. Here’s a shot of Jessie’s, to hopefully prod me into action:

I didn’t get all of Peter’s quiz questions correct. I knew that the endocast of the pharyngeal pouch in a horse was an endocast, but of what I didn’t know, although I did correctly identify the hyoid apparatus of a horse, mounted separately. And there was a partial cetacean jaw that I misidentified as a shark (in my defense, it was from one of the small, short-faced weirdos). Still, Peter said that I’d done as well as anyone else ever had. That was nice to hear, but I was already happy to have gotten to see and talk about so many cool things with a fellow connoisseur. Thanks, Peter, for a wonderful afternoon, and for permission to post these pictures. I am looking forward to a rematch!


  • Dodson, P. 1990. Sauropod paleoecology. In: D.B. Weishampel, P. Dodson, P., & H. Osmolska, (eds), The Dinosauria, 402-407. University of California Press, Berkeley.
  • Porter, W.R., Sedlmayr, J.C. and Witmer, L.M., 2016. Vascular patterns in the heads of crocodilians: blood vessels and sites of thermal exchange. Journal of Anatomy 229(6): 800-824.
  • Stout, W., Service, W., and Preiss, B. 1984. The Dinosaurs: A Fantastic View of a Lost Era. Bantam Dell Publishing Group, 160pp.

So, here’s a cool thing that happened at Norwescon. On Saturday afternoon, there was an autograph signing session. Probably to the surprise of no-one, a lot more people were interested in having things signed by the other two guests of honor, Galen Dara and Ken Liu, than by me. But happily I was situated between them so I coasted a bit on the interest they drew. There was quite a bit of downtime in the two-hour session, so I had the chance to chat with both Galen and Ken. That was actually a highlight of the con for me – I was hoping for a chance to get to know my fellow guests of honor a bit, instead of just passing them in the hallways as we all went off to our separate scheduled activities.

Whenever Galen Dara wasn’t signing autographs, she was drawing. Makes sense, right? You probably don’t get to be as professionally successful as she is if making art isn’t compulsive. And it was just my luck that the proximate cool thing around to draw was the skull of Aquilops – I was signing prints of my skull recon, and I had along the reconstructed cast skull that I use for education and outreach. So I had the fairly trippy experience of watching an award-winning artist at the top of her game draw ‘my’ critter.

As you can see from Galen’s Instagram, she draws and paints a lot of skulls, and she spends a lot of time exploring the geometric underpinnings of skulls. She warned me at the outset that her Aquilops skull would be more impressionistic than photo-realistic – her interpretation of Aquilops as organic art. I think it looks pretty great; I have to trace stuff to get the proportions that close on the first go. And as I recently mentioned in another post, it’s always mesmerizing for me to see how a visual artist can conjure form, weight, and texture one pencil-stroke at a time.

Many thanks to Galen for permission to post these pics, and for her interest in my favorite non-sauropod.

Old drawings (of heads)

June 25, 2017

I was organizing my files in DropBox and I found a folder of old drawings I’d almost forgotten about. I drew this back in the late 90s. It was used on a t-shirt by the OU Zoology Department. I got the general idea of making a head out of animals, and the specific idea of using a butterfly wing for the ear, from Wayne Douglas Barlowe’s cover for the novel Wild Seed by Octavia Butler. The snake I stole from ancient Egypt. I think everything else is in there just because I thought it was cool. Note that inverts, fish, herps, birds, and mammals are all represented, with a good balance of aquatic, terrestrial, and volant forms. It looks awfully hippie-dippie from 20 years out, but heck, what doesn’t?

“Solitude” by Mathew Wedel. CC BY-NC 4.0.

Well, this, I suppose.

I drew this about the same time. I was reading The Gnostic Gospels by Elaine Pagels and lots of stuff about ancient monastic traditions and thinking that if the world is an illusion that must be penetrated, then the evidence of one’s senses can only mislead. Also, Vicki was working for the state medical examiner in Oklahoma City and they used wooden dowels to represent the paths of bullets when reconstructing the skulls of those killed by gunfire. So here’s the skull of a monk, with all of the lethal pathways of distraction and temptation clearly marked as such. At last he can contemplate the eternal mysteries in perfect solitude.

Obviously I didn’t get on board the world-is-an-illusion, sensation-is-bad train – skewed pretty hard in the opposite direction, in fact. Possibly because years earlier the Chessmen of Mars by Edgar Rice Burroughs had shown me that pursuing ‘pure’ intellectual and spiritual inquiry would ultimately lead one to a pathetic existence as a disembodied head living in a cave (high culture, meet low culture). Anyway, whatever interest I might have had in that philosophy I exorcised through this drawing. Stripped of any art-making-a-point baggage, I still think it’s pretty bitchin’. I should make t-shirts.

Actually, I probably will make t-shirts of this one if there’s any interest. Hence the CC BY-NC license I put on it, as opposed to the normal CC BY for almost everything else on this site. Look at me, boldly experimenting with new licenses.

This, obviously, is a lot more recent. I was collating all of my scanned drawings and I realized that I’d gone to the trouble of drawing the cranium and lower jaw of Aquilops separately, but I’d never posted the version from before I composited them back into articulation. It is very unlike me to do work and then hide it, so here it is.

It wasn’t until I the post mostly written that I realized that all three drawings are of heads, none of them are saurischians (although the first includes a saurischian, but not the cool kind), and two are stinkin’ mammals (and not the cool kind). I stand ready for your slings and arrows.

For previous posts on my drawings, see: