Nature’s CT machine

January 28, 2020

Because I’ve worked a lot on the anatomy and evolution of air-filled bones in sauropod dinosaurs, I’ve spent most of my career looking at images like this:

CT sections through a cervical vertebra of an apatosaurine (Apatosaurus or Brontosaurus), OMNH 1094. Wedel (2003b: fig. 6). Scale bar is 10cm.

…and thinking about images like this:

Physical sections through pneumatic vertebrae of Giraffatitan. Janensch (1950: figs. 71-73).

Turns out, that’s pretty good practice for fossil prospecting in the Salt Wash member of the Morrison Formation, where we frequently find things like this:

That’s a bit hard to read, so let’s pull it out from the background:

This is almost certainly a pneumatic vertebra of a sauropod, sectioned more-or-less randomly by the forces of erosion to expose a complicated honeycomb of internal struts and chambers. The chambers are full of sandstone now, but in life they were full of air. I say “almost certainly” because there is small chance that it could belong to a very large theropod, but it looks more sauropod-y to me (for reasons I may expand upon in the comments if anyone is curious).

I’m not 100% certain what section this is. At first I was tempted to read it as a transversely-sectioned dorsal, something like the Allosaurus dorsal shown in this post (link) but from a small, possibly juvenile sauropod. But the semi-radial, spoke-like arrangement of the internal struts going to the round section at the bottom looks very much like the inside of the condyle of a sauropod cervical or cervico-dorsal–compare to fig. 71 from Janensch (1950), shown above. And of course there is no reason to suspect that the plane of this cut is neatly in any of the cardinal anatomical directions. It is most likely an oblique cut that isn’t purely transverse or sagittal or anything else, but some combination of the above. It’s also not alone–there are bits and bobs of bone to the side and above in the same chunk of sandstone, which might be parts of this vertebra or of neighboring bones. Assuming it is a sauropod, my guess is Diplodocus or Brachiosaurus, because it looks even more complex than the sectioned cervicals and dorsals I’ve seen of Haplocanthosaurus, Camarasaurus, or the apatosaurines.

Sometimes we can do a little better. This is one of my favorite finds from the Salt Wash. This boulder, now in two parts, fell down out of a big overhanging sandstone cliff. When the boulder hit, it broke into two halves, and the downhill half rolled over 180 degrees, bringing both cut faces into view in this photo. And there in the boulder is what looks like two vertebrae, but is in fact the neatly separated halves of a single vertebra. I know I refer to erosion and breakage as “Nature’s CT machine”, but this time that’s really on the nose. Let’s take a closer look:

Here’s what I see:

It’s a proportionally long vertebra with a round ball at one end and a hemispherical socket at the other end: a cervical vertebra of a sauropod. Part of the cervical rib is preserved on the upper side, which I suspect is the left side. The parapophysis on the opposite side is angled a bit out of the rock, toward the camera. Parapophyses of sauropod cervicals tend to be angled downward, and if we’re looking at the bottom of this vertebra, then the rib on the upper side is the left. The right cervical rib was cut off when the boulder broke. All we have on this side are the wide parapophysis and the slender strut of the diapophysis aiming out of the rock toward the missing rib, which must still be embedded in the other half of the boulder–and in fact you can see a bit of it peeking out in the counterpart in the wide shot, above.

Can we get a taxonomic ID? I think so, based on the following clues:

  • The cervical ribs are set waaay out to either side of the centrum, by about one centrum diameter. Such wide-set cervical ribs occur in Camarasaurus and the apatosaurines, Apatosaurus and Brontosaurus, but not typically in Diplodocus, Brachiosaurus, or other Morrison sauropods.
  • The cervical rib we can see the most of is pretty slender, like those of Camarasaurus, in contrast to the massive, blocky cervical ribs of the apatosaurines (for example).
  • We can see at least bits of both the left and right cervical ribs in the two slabs–along with a section right through the centrum. So the cervical ribs were set wide from the centrum but not displaced deeply below it, as in Camarasaurus, and again in contrast to the apatosaurines, in which the cervical ribs are typically displaced far below (ventral to) the centrum (see this).
  • This one is a little more loosey-goosey, but the exposed internal structure looks “about right” for Camarasaurus. There is a mix of large and small chambers, but not many small ones, and nothing approaching the coarse, regular honeycomb we’d expect in Apatosaurus, Brontosaurus, or Diplodocus, let alone the fine irregular honeycomb we’d expect in Barosaurus or Brachiosaurus (although I will show you a vert like that in an upcoming post). On the other hand, the internal structure is too complex for Haplocanthosaurus (compare to the top image here).
  • As long as Camarasaurus is on the table, I’ll note that the overall proportions are good for a mid-cervical of Cam as well. That’s not worth much, since vertebral proportions vary along the column and almost every Morrison sauropod has cervicals with this general proportion somewhere in the neck, but it doesn’t hurt.

So the balance of the evidence points toward Camarasaurus. In one character or another, every other known Morrison sauropod is disqualified.

When it’s too dark to hunt for sauropods, you can look at other things.

Now, Camarasaurus is not only the most common sauropod in the Morrison, it’s also the most common dinosaur of any kind in the formation. So this isn’t a mind-blowing discovery. Still, it’s nice to be able to get down to a genus-level ID based on a single vertebra fortuitously sectioned by Mother Nature. In upcoming posts, I’ll show some of the more exciting critters that we’ve been able to ID out of the Salt Wash, ‘we’ here including Brian Engh, John Foster, ReBecca Hunt-Foster, Jessie Atterholt, and Thuat Tran. Brian will also be showing many of these same fossils in the next installment of Jurassic Reimagined. Catch Part 1 here (link), and stay tuned to Brian’s paleoart channel (here) for more in the very near future.


The Man Himself, taking notes on what look like Giraffatitan caudals.

Here’s how I got my start in research. Through a mentorship program, I started volunteering at the Oklahoma Museum of Natural History in the spring of 1992, when I was a junior in high school. I’d been dinosaur-obsessed from the age of three, but I’d never had an anatomy course and didn’t really know what I was doing. Which is natural! I had no way of knowing what I was doing because I lacked training. Fortunately for me, Rich Cifelli took me under his wing and showed me the ropes. I started going out on digs, learned the basics of curatorial work, how to mold and cast fossils, how to screenwash matrix and then pick microfossils out of the concentrate under a dissecting microscope, and—perhaps most importantly—how to make a rough ID of an unidentified bone by going through the comparative element collection until I found the closest match.

All set, right? Ignition, liftoff, straight path from there to here, my destiny unrolling before me like a red carpet.


It could have gone that way, but it didn’t. I had no discipline. I was a high-achieving high school student, but it was all to satisfy my parents. When I got to college, I didn’t have them around to push me anymore, and I’d never learned to push myself. I went off the rails pretty quickly. Never quite managed to lose my scholarships, without which I could not have afforded to be in college, period, but I skimmed just above the threshold of disaster and racked up a slate of mediocre grades in courses from calculus to chemistry. I even managed to earn a C in comparative anatomy, a fact which I am now so good at blocking out that I can go years at a time without consciously recalling it.

After three years of this, I had the most important conversation of my life. Because I was a zoology major I’d been assigned a random Zoology Dept. faculty member as an undergrad advisor. I was given to Trish Schwagmeyer, not because we got on well (we did, but that was beside the point) or had similar scientific interests, just luck of the draw. And it was lucky for me, because in the spring of 1996 Trish looked at my grades from the previous semester, looked me in the eye, and said, “You’re blowing it.” She then spent the next five minutes explaining in honest and excruciating detail just how badly I was wrecking my future prospects. I’ve told this story before, in this post, but it bears repeating, because that short, direct, brutal-but-effective intervention became the fulcrum for my entire intellectual life and future career.

The holotype specimen of Sauroposeidon coming out of the ground in 1994.

Roughly an hour later I had the second most important conversation of my life, with Rich Cifelli. While I’d been lost in the wilderness my museum volunteering had petered out to zero, and Rich would have been completely justified in telling me to get lost. Not only did he not do that, he welcomed me back into the fold, in a terrifyingly precise recapitulation of the Biblical parable of the prodigal son. When I asked Rich if I could do an independent study with him in the next semester, he thought for a minute and said, “Well, we have these big dinosaur vertebrae from the Antlers Formation that need to be identified.” Which is how, at the age of 21, with a rubble pile of an academic transcript and no real accomplishments to stand on, I got assigned to work on OMNH 53062, the future holotype of Sauroposeidon proteles.

I was fortunate in four important ways beyond the forgiveness, patience, and generosity of Richard Lawrence Cifelli:

  • OMNH 53062 was woefully incomplete, just three and a half middle cervical vertebrae, which meant that the project was small enough in concept to be tractable as an independent study for an undergrad. Rich and I both figured that I’d work on the vertebrae for one semester, come up with a family-level identification, and maybe we’d write a two-pager for Oklahoma Geology Notes documenting the first occurrence of Brachiosauridae (or whatever it might turn out to be) in the vertebrate fauna of the Antlers Formation.
  • Because the specimen was so incomplete, no-one suspected that it might be a new taxon, otherwise there’s no way such an important project would have been assigned to an undergrad with a spotty-to-nonexistent track record.
  • Despite the incompleteness, because the specimen consisted of sauropod vertebrae, it held enough characters to be identifiable–and eventually, diagnosable. Neither of those facts were known to me at the time.
  • All of Rich’s graduate students were already busy with their own projects, and nobody else was about to blow months of time and effort on what looked like an unpromising specimen.

NB: this guy is not a prodigy.

There is a risk here, in that I come off looking like some kind of kid genius for grasping the importance of OMNH 53062, and Rich’s other students look like fools for not seeing it themselves. It ain’t like that. The whole point is that nobody grasped the importance of the specimen back then. It would take Rich and me a whole semester of concentrated study just to come to the realization that OMNH 53062 might be distinct enough to be diagnosable as a new taxon, and a further three years of descriptive and comparative work to turn that ‘maybe’ into a paper. People with established research programs can’t afford to shut down everything else and invest six months of study into every incomplete, garbage-looking specimen that comes down the pike, on the off chance that it might be something new. Having the good judgment to not pour your time down a rat-hole is a prerequisite for being a productive researcher. But coming up with a tentative ID of an incomplete, garbage-looking specimen is a pretty good goal for a student project: the student learns some basic comparative anatomy and research skills, the specimen gets identified, no existing projects get derailed, and no-one established wastes their time on what is most likely nothing special. If the specimen does turn out to be important, that’s gravy.

So there’s me at the start of the fall of 1996: with a specimen to identify and juuuust enough museum experience, from my high school mentorship, to not be completely useless. I knew that one identified a fossil by comparing it to known things and looking for characters in common, but I didn’t know anything about sauropods or their vertebrae. Rich got me started with a few things from his academic library, I found a lot more in OU’s geology library, and what I couldn’t find on campus I could usually get through interlibrary loan. I spent a lot of time that fall standing at a photocopier, making copies of the classic sauropod monographs by Osborn, Hatcher, Gilmore, Janensch, and others, assembling the raw material to teach myself sauropod anatomy.

The sauropod monographs live within arm’s reach of my office chair to this day.

In addition to studying sauropods, I also started going to class, religiously, and my grades rose accordingly. At first I was only keeping up with my courses so that I would be allowed to continue doing research; research was the carrot that compelled me to become a better student. There was nothing immediate or miraculous about my recovery, and Rich would have to give me a few well-deserved figurative ass-kickings over the next few years when I’d occasionally wander off course again. But the point was that I had a course. After a few months I learned—or remembered—to take pride in my coursework. I realized that I had never stopped defining myself in part by my performance, and that when I’d been adrift academically I’d also been depressed. It felt like crawling out of a hole.

(Aside: I realize that for many people, depression is the cause of academic difficulty, not the reverse, and that no amount of “just working harder” can offset the genuine biochemical imbalances that underlie clinical depression. I sympathize, and I wish we lived in a world where everyone could get the evaluation and care that they need without fear, stigma, crushing financial penalties, or all of the above. I’m also not describing any case here other than my own.)

What fresh hell is this? (Apatosaur dorsal from Gilmore 1936)

Out of one hole, into another. The biggest problem I faced back then is that if you are unfamiliar with sauropod vertebrae they can be forbiddingly complex. The papers I was struggling through referred to a pandemonium of laminae, an ascending catalog of horrors that ran from horizontal laminae and prespinal laminae through infraprezygapophyseal laminae and spinopostzygapophyseal laminae. Often these features were not labeled in the plates and figures, the authors had just assumed that any idiot would know what a postcentrodiapophyseal lamina was because, duh, it’s right there in the name. But that was the whole problem: I didn’t know how to decode the names. I had no map. SV-POW! tutorials didn’t exist. Jeff Wilson’s excellent and still-eminently-useful 1999 paper codifying the terminology for sauropod vertebral laminae was still years in the future.

Then I found this, on page 35 of Werner Janensch’s 1950 monograph on the vertebrae of what was then called Brachiosaurus brancai (now Giraffatitan):

It was in German, but it was a map! I redrew it by hand in my very first research notebook, and as I was copying down the names of the features the lightbulb switched on over my head. “Diapophyse” meant “diapophysis”, and it was the more dorsal of the two rib attachments. “Präzygapophyse” was “prezygapophysis”, and it was one of the paired articular bits sticking out the front of the neural arch. And, crucially, “Präzygodiapophysealleiste” had to be the prezygodiapophyseal lamina, which connected the two. And so on, for all of the weird bits that make up a sauropod vertebra.

It’s been 22 years and I still remember that moment of discovery, my pencil flying across the page as I made my own English translations of the German anatomical terms, my mind buzzing with the realization that I was now on the other side. Initiated. Empowered. I felt like I had pulled the sword from the stone, found Archimedes’ lever that could move the world. In the following weeks I’d go back through all of my photocopied sauropod monographs with my notebook open to the side, reading the descriptions of the vertebrae for the second or third times but understanding them for the first time, drawing the vertebrae over and over again until I could call up their basic outlines from memory. This process spilled over from the fall of 1996 into the spring of 1997, as Rich and I realized that OMNH 53062 would require more than one semester of investigation.

Interlude with a left femur of the Oklahoma apatosaurine (but not the largest individual).

My memories of those early days of my sauropod research are strongly shaped by the places and circumstances in which I was doing the work. Vicki and I had gotten married in the summer of 1996 and moved into a two-bedroom duplex apartment on the north side of Norman. The upstairs had a long, narrow bathroom with two sinks which opened at either end onto the two upstairs bedrooms, the one in which we slept and the one we used as a home office. In the mornings I could get showered and dressed in no time, and while Vicki was getting ready for work or school I’d go into the office to read sauropod papers and take notes. Vicki has always preferred to have music on while she completes her morning rituals, so I listened to a lot of Top 40 hits floating in from the other upstairs rooms while I puzzled out the fine details of sauropod vertebral anatomy.

Two songs in particular could always be counted on to play in any given hour of pop radio in the early spring of 1997: Wannabe by the Spice Girls, and Lovefool by the Cardigans. I am surely the only human in history to have this particular Pavlovian reaction, but to this day when I hear either song I am transported back to that little bedroom office where I spent many a morning poring over sauropod monographs, with my working space illuminated by the light of the morning sun pouring through the window, and my mind illuminated by Werner Janensch, who had the foresight and good grace to give his readers a map.

Figure 5 from my undergraduate thesis: OMNH 53062 in right lateral view.

If you want to know what I thought about OMNH 53062 back in 1997, you can read my undergraduate thesis—it’s a free download here. Looking back now, the most surprising thing to me about that thesis is how few mentions there are of pneumaticity. I met Brooks Britt in the summer of 1997 and had another epochal conversation, in which he suggested that I CT scan OMNH 53062 to look at the air spaces inside the vertebrae. I filed my undergrad thesis in December of 1997, and the first session CT scanning OMNH 53062 took place in January, 1998. So in late 1997 I was still a pneumaticity n00b, with no idea of the voyage I was about to embark upon.

In 2010, after I was settled in as an anatomist at Western University of Health Sciences, I wrote a long thank-you to Trish Schwagmeyer. It had been 14 years since that pivotal conversation, but when she wrote back to wish me well, she still remembered that I’d gotten a C in comparative anatomy. I’d have a chance to make amends for that glaringly anomalous grade later the same year. At ICVM in Punta del Este, Uruguay, I caught up with Edie Marsh-Matthews, who had taught my comparative anatomy course back when. I apologized for having squandered the opportunity to learn from her, and she graciously (and to my relief) shifted the conversation to actual comparative anatomy, the common thread that connected us in the past and the present.

If the story has a moral, it’s that I owe my career in large part to people who went out of their way to help me when I was floundering. And, perhaps, that the gentle approach is not always the best one. I needed to have my head thumped a few times, verbally, to get my ass in gear, when less confrontational tactics had failed. I slid easily through the classrooms of dozens of professors who watched me get subpar grades and didn’t try to stop me (counterpoint: professors are too overworked to invest in every academic disaster that comes through the door, just like paleontologists can’t study every garbage specimen). If Trish Schwagmeyer and Rich Cifelli had not decided that I was worth salvaging, and if they not had the grit to call me out on my BS, I wouldn’t be here. As an educator myself now, that thought haunts me. I hope that I will be perceptive enough to know when a student is struggling not because of a lack of ability but through a lack of application, wise enough to know when to deploy the “you’re blowing it” speech, and strong enough to follow through.


  • Gilmore Charles W. 1936. Osteology of Apatosaurus, with special reference to specimens in the Carnegie Museum. Memoirs of the Carnegie Museum 11:175–300 and plates XXI–XXXIV.
  • Janensch, Werner.  1950.  Die Wirbelsaule von Brachiosaurus brancai.  Palaeontographica (Suppl. 7) 3: 27-93.
  • Wedel, M.J. 1997. A new sauropod from the Early Cretaceous of Oklahoma. Undergraduate honor thesis, Department of Zoology, University of Oklahoma, Norman, OK. 43pp.
  • Wilson, J.A. 1999. A nomenclature for vertebral laminae in sauropods and other saurischian dinosaurs. Journal of Vertebrate Paleontology 19: 639-653.

Matt with big Apato dorsal 2000

Final bonus image so when I post this to Facebook, it won’t grab the next image in line and crop it horribly to make a preview. This is me with OMNH 1670, in 2003 or 2004, photo by Andrew Lee.

Back in the spring of 1998, Kent Sanders and I started CT scanning sauropod vertebrae. We started just to get a baseline for the Sauroposeidon project, but in time the data we collected formed the basis for my MS thesis, and for a good chunk of my dissertation as well. Mostly what we had available to scan was Morrison material. Between imperfect preservation, inexpert prep (by WPA guys back in the ’30s), and several moves over the decades, most of the verts from the Oklahoma Morrison have their neural spines and cervical ribs broken off. One of the first things I had to figure out was how to tell broken vertebrae of Camarasaurus from those of Apatosaurus (at the time; Brontosaurus is back in contention now). Here’s a thing I made up to help me sort out cervical centra of Camarasaurus and whatever the Oklahoma apatosaurine turns out to be. It’s a recent production, but it embodies stuff from my notebooks from 20 years ago. Should be useful for other times and places in the Morrison as well, given the broad spatiotemporal overlap of Camarasaurus and the various apatosaurines.

For a related thing in the same vein, see Tutorial 30: how to identify Morrison sauropod cervicals.

More elephant seals soon, I promise.

UPDATE 20 Feb 2018

Ken Carpenter sent this by email, with a request that I post it as a comment. Since it includes an image, I’m appending to the post, because it makes an important point that I neglected to mention.

Camar post cerv

Ken: Sorry, Matt. Not so easy. The last cervical of Camarasaurus from the Cleveland Lloyd Quarry is more apatosaurine-like than Camarasaurus-like based on your posting. Note the position of both zygapohyses with both ends of the centrum.

My response: Yes, good catch. I meant to say in the post that my distinguishing characters break down at the cervico-dorsal transition. Even so, in this Cleveland Lloyd vert the postzyg is still forward of a line drawn directly up from the cotyle. I’ve never seen that in an apatosaurine–going into the dorsal series, the postzygs tend to be centered over a line projected up from the rim of the cotyle. (If anyone knows of counterexamples, speak up!)

For distinguishing cervico-dorsals, apatosaurines tend to have much taller neural spines than Camarasaurus, and this carries on through the rest of the dorsal series. In apatosaurine dorsals, the height of the spine above the transverse processes always equals or exceeds the height of the arch below the transverse processes. In Camarasaurus, the height of the dorsal neural spines is always less than or equal to the height of the arch. The shapes of the spines are fairly different, too. Maybe that will be the subject of a future post.

Here’s OMNH 1330, another vertebra from the big Oklahoma apatosaurine. Based on the size and shape of the transverse process, and the large pneumatic chambers on either side of the neural canal, I think this is probably a 4th caudal, but it could plausibly be a 3rd or a 5th. The centrum is 33 cm tall by 36 cm wide.

For other elements of the big Oklahoma apatosaurine, please see:

I have used this photo in loads of talks, but as far as I can tell, this is the first time I’ve put it up on SV-POW! (I am certain that, having said that, someone will find a previous instance – if so, consider this an extremely inefficient and lazy form of search.) The vert is OMNH 1670, the most complete and nicest dorsal of the giant Oklahoma apatosaurine, probably a D5 or D6. That’s me back in 2004. Photo by my then fellow grad student in the Padian lab, Andrew Lee. I’m 6’2″ and have normally-proportioned human arms, but if you’re trying to figure out the scale, that vert is 135cm tall, with an anterior centrum face 38cm tall by 46cm wide (partly reconstructed but probably accurate). See this post for more details and a fairly exhaustive list of measurements.

Here’s a stupid thing: roughly 2-3 times a year I go to the field or to a museum and get hundreds of SV-POW!-able photos. Then I get back to the world and catch up on all of the work that piled up while I was away. And by the time I’m done with that, whatever motivating spark I had – to get some of those photos posted and talk about the exciting things I figured out – has dissipated.

Case in point – this bitchin’ shark, prepped in ventral view, which I saw last month in the natural history museum in Vienna. Look at that fat, muscular tail – this shark is swole.

That’s dumb. And this blog is in danger of slipping into senescence, and irrelevance.

So here’s my New Year blog resolution for 2018: I’m getting us back to our roots. I, or we – I am taking this plunge without consulting with Mike (surprise, buddy!) – will post a new, never-posted-before photo, at least once a week, for the whole year. It may not always be a sauropod vertebra, but if often will be, because that’s what I have the most of, and the most to yap about. And I will try to write something interesting about each photo, without lapsing into the logorrhea that has too often made this blog too exhausting to contemplate (at least from this side of the keyboard).

Wish me luck!

Anterior view. Dorsal is to the upper right. The neural spine and left transverse process are missing.

Here’s a closeup of the condyle. The outer layer of cortical bone is gone, allowing a glimpse of the pneumatic chambers inside the vert. The erosion of the condyle was probably inflicted post-excavation by relatively unskilled WPA workers, whose prep tools were limited to chisels, penknives, and sandpaper. Because the bones from the Kenton localities are roughly the same color as the matrix, the preparators sometimes did not realize that they were sanding into the bones until the internal structure was revealed. Bad for the completeness of this specimen, but good for pneumaticity junkies like me, because this baby is too big to be scanned by any but the largest industrial CT machines.

For other posts on the giant Oklahoma apatosaur, see:

Clash of the Titans from above

Here’s the “Clash of the Titans” exhibit at the Sam Noble Oklahoma Museum of Natural History, featuring the reconstructed skeletons of the giant Oklahoma Apatosaurus – which I guess should now be called the giant Oklahoma apatosaurine until someone sorts out its phylogenetic position – and the darn-near-T. rex-sized Saurophaganax maximus, which may be Allosaurus maximus depending on who you’re reading.

Now, I love this exhibit in both concept and execution. But one thing that is more obvious in this view from the upper level balcony is that despite its impressive weaponry, a lone 3-to-5 ton Saurophaganax had an Arctic ice cap’s chance in the Anthropocene of taking down a healthy 30-meter, 40-50 ton apatosaur (which is to say, none). I like to imagine that in the photo above, the apatosaur is laughing at the pathetically tiny theropod and its delusions of grandeur.

Clash of the Titans from behind

In this shot from behind, you get a better look at the baby apatosaur standing under the big one, and it hints at a far more likely target for Saurophaganax and other large Morrison theropods: sauropods that were not fully-grown, which was almost all of them. I am hip to the fact that golden eagles kill deer, and some lions will attack elephants – as Cookie Monster says, “Sometime food, not anytime food” – but not only were smaller sauropods easier prey, they were far more numerous given the inevitable population structure of animals that started reproducing at a young age and made more eggs the bigger they got (as essentially all egg-laying animals do).

In fact, as discussed in our recent paper on dinosaur ontogeny (Hone et al. 2016), there may have been times when the number of fully-grown sauropods in a given population was zero, and the species was maintained by reproducing juveniles. The giant Oklahoma apatosaurine is a unique specimen today – by far the largest apatosaurine we have fossils of – but it may also have been an anomaly in its own time, the rare individual that made it through the survivorship gauntlet to something approaching full size.

Amazingly enough, there is evidence that even it was not fully mature, but that’s a discussion for another day. Parting shot:

Oklahoma Apatosaurus neck and head


OMNH 1331 is my new hero

March 24, 2013

Here’s an update from the road–get ready for some crappy raw images, because that’s all I have the time or energy to post (with one exception).

OMNH 1331

Here’s OMNH 1331. It’s just the slightly convex articular end off a big vertebra, collected near Kenton, Oklahoma, in 1930s by one of J. Willis Stovall’s field crews. I measured the preserved width at 45 cm using a tape measure, and at 44.5 in GIMP using the scale bar in the photo, which is up on a piece of styrofoam so it’s about the same distance from the camera as the rim of the vertebra (i.e, about 8 feet–as high as I could get and still shoot straight down). So whether your distrust runs to tape measures or scale bars in photos, I am prepared to argue that this sucker is roughly 45 cm wide.

OMNH 1331 internal structure

There’s admittedly not a ton of morphology here, but the size and the fact that the other side is hollow and has a midline bony septum show that it is a pneumatic vertebra from a sauropod, and given that the quarry it’s from was chock-full of Apatosaurus, and liberally salted with gigantic Apatosaurus, I feel pretty good about calling it Apatosaurus.

OMNH 1331 cloned and flipped

To figure out how wide the articular face was when it was intact, I duplicated the image and reversed it left-to-right in GIMP, which yields an intact max width of about 49 cm. That is friggin’ immense.

If we make the maximally conservative assumption that this is the largest centrum in the whole skeleton of a big Apatosaurus, then it has to be part of a dorsal vertebra. Here are the max diameters of the largest dorsal centra in some big mounted apatosaurs, taken from Gilmore (1936). The number in parentheses is how many percent bigger OMNH 1331 is.

  • A. louisae CM 3018 – 36.5 cm (34%)
  • A. parvus UWGM 15556 – 36.5 cm (34%)
  • A. sp. FMNH P25112 – 41 cm (20%)

OMNH 1331 lateral view

However, this might not be part of a dorsal vertebra. For one thing, it’s pretty convex, and Apatosaurus dorsals sometimes have a little bump but they’re pretty close to amphiplatyan, at least in the posterior half of the series. For another, I think that smooth lower margin on the right in the photo above is part of the rim of a big pneumatic foramen, but it’s waaay up high and pretty medial on the centrum, opening more dorsally than laterally, which I have seen a lot in anterior caudal vertebrae. Finally, Jack McIntosh went through the OMNH collections years ago and his identifications formed the basis for a lot of the catalogue IDs, and this thing is catalogued as the condyle off the back end of a proximal caudal.

Here are the max diameters of the largest caudal centra in those same mounted apatosaurs, again taken from Gilmore (1936). Once again, the number in parentheses is how many percent bigger OMNH 1331 is.

  • A. louisae CM 3018 – 30 cm (63%)
  • A. parvus UWGM 15556 – 32.5 cm (51%)
  • A. sp. FMNH P25112 – 39 cm (26%)

(Aside: check out the skinny rear end on A. louisae. ‘Sup with that?)

So whatever vert it’s part of, OMNH 1331 is damn big bone from a damn big Apatosaurus. There are lots of other big Apatosaurus vertebrae in the OMNH collections, like OMNH 1670, but OMNH 1331 is the largest centrum that I know of in this museum. Which is why you’re getting a post about most of one end of a centrum in the wee hours of the morning–it’s most of one end of an awesome centrum. And it pains me when people do comparison figures of big sauropod vertebrae, or lists of the “Top 10 Largest Sauropods”, and put in stuff like Argentinosaurus and Puertasaurus and Supersaurus, but leave out Apatosaurus. It was legitimately huge, and it’s time the world realized that.

For more on the giant Oklahoma Apatosaurus, see:


Gilmore, C.W. 1936. Osteology of Apatosaurus with special reference to specimens in the Carnegie Museum. Memoirs of the Carnegie Museum 11:175-300.

In the recent post on OMNH 1670, a dorsal vertebra of a giant Apatosaurus from the Oklahoma panhandle, I half-promised to post the only published figure of this vertebra, from Stovall (1938: fig. 3.3). So here it is:

And in the second comment on that post, I promised a sketch from one of my notebooks, showing how much of the vertebra is reconstructed. Here’s a scan of the relevant page from my notebook. Reconstructed areas of the vert are shaded (confusingly, using strokes going in opposite directions on the spine and centrum, and the dark shaded areas on the front of the transverse processes are pneumatic cavities), and measurements are given in mm.

Next item: is this really a fifth dorsal vertebra?

Apatosaurus louisae CM 3018 D4 and D5, in anterior (top), left lateral, and posterior views, from Gilmore (1936: plate 25).

Here are D4 and D5 of A. louisae CM 3018. They sort of bracket OMNH 1670 in terms of morphology. D4 has a broader spine, and D5 has a narrower one. The spine of D5 lacks the slight racquet-shaped expansion seen in OMNH 1670, but the overall proportions of the spine are more similar. On the other hand, the transverse processes of D4 taper a bit in anterior and posterior view, as in OMNH 1670, and unlike the transverse processes of D5 with their more parallel dorsal and ventral margins. But honestly, neither of these verts is a very good match (and the ones on either side, D3 and D6, are even worse).

Apatosaurus parvus UWGM 15556 (formerly A. excelsus CM 563) D4 (left) and D3 (right) in anterior (top), right lateral, and posterior views, from Gilmore (1936: plate 32).

Here are D3 and D4 of A. parvus UWGM 15556. D3 is clearly a poor match as well–it is really striking how much the vertebral morphology changes through the anterior dorsals in most sauropods, and Apatosaurus is no exception. D3 looks like a dorsal in lateral view, but in anterior or posterior view it could almost pass for a posterior cervical. If I was going to use the term “cervicodorsal”, indicating one of the vertebrae from the neck/trunk transition, I would apply it as far back as D3, but not to D4. That thing is all dorsal.

And it’s a very interesting dorsal from the perspective of identifying OMNH 1670. It has fairly short, tapering transverse processes. The neural spine is a bit shorter and broader, but it has a similar racquet-shaped distal expansion. I’m particularly intrigued by the pneumatic fossae inscribed into the anterior surface of the neural spine–in Gilmore’s plate they make a broken V shapen, like so \ / (or maybe devil eyes). Now, OMNH 1670 doesn’t have devil eyes on its spine, but it does have a couple of somewhat similar pneumatic fossae cut into the spine just below the distal racquet–perhaps a serially modified iteration of the same pair of fossae as in the A. parvus D4. It’s a right sod that D5 from this animal has its spine blown off–but it still has its transverse processes, and they are short and tapering as in OMNH 1670.

Apatosaurus sp. FMNH P25112, dorsal vertebrae 1-10 and sacrals 1 and 2, Riggs (1903: plate 46)

Here are all the dorsals and the first couple sacrals of FMNH P25112, which was originally described as A. excelsus but in the specimen-level analysis of Upchurch et al. 2005) comes out as the sister taxon to the A. ajax/A. parvus/A. excelsus clade. Note the striking similarity of the D5 here with D4 of the A. parvus specimen in Gilmore’s plate (until the careful phylogenetic work up Upchurch et al. 2005, that A. parvus specimen, once CM 563 and now UWGM 15556, was considered to represent A. excelsus as well). But  also notice the striking similarity of D6 to OMNH 1670. It’s not quite a dead ringer–the transverse processes are longer and have weird bent-down “wingtips” (XB-70 Valkyrie, anyone?)–but it’s pretty darned close, especially in the shape of the neural spine.

So what does this all mean? First, that trying to specify the exact serial position of an isolated vertebra is nigh on to impossible, unless it’s something that is one-of-a-kind like an axis. Second, after doing all these comparos I think it’s unlikely that OMNH 1670 is a D4–those are a bit too squat across the board–but it could plausibly be either a D5 or a D6. Third, I’m really happy that it doesn’t seem to match any particular specimen better than all the rest. What I don’t want to happen is for someone to see that this vertebra looks especially like specimen X and therefore decide that it must represent species Y. As I said in the comments of the previous post, what this Oklahoma Apatosaurus material needs is for someone to spend some quality time seeing, measuring, and photographing all of it and then doing a phylogenetic analysis. That sounds like an ambitious master’s thesis or the core of a dissertation, and I hope an OU grad student takes it on someday.

If you were intrigued by my suggestion that the big Oklahoma Apatosaurus rivalled Supersaurus in size, and wanted to see a technical comparison of the two, I am happy to report that Scott Hartman has done the work for you. Here’s one of his beautiful Apatosaurus skeletal reconstructions, scaled to the size of OMNH 1670, next to his Supersaurus silhouette. This is just a small teaser–go check out his post on the subject for a larger version and some interesting (and funny) thoughts on how the two animals compare.


  • Gilmore, C.W. 1936. Osteology of Apatosaurus with special reference to specimens in the Carnegie Museum. Memoirs of the Carnegie Museum 11:175-300.
  • Riggs, E.S. 1903. Structure and relationships of opisthocoelian dinosaurs, part I: Apatosaurus Marsh. Field Columbian Museum Publications, Geological Series 2(4): 165–196.
  • Stovall, J.W. 1938. The Morrison of Oklahoma and its dinosaurs. Journal of Geology 46:583-600.

Left: the Queen of England, 163 cm.  Middle, the Oklahoma apatosaur dorsal, 135 cm.  Right, classic “big Apatosaurus” dorsal, 106 cm.  To scale.

Something I’ve always intended to do but never gotten around to is posting on some of the immense Apatosaurus elements from the Oklahoma panhandle. Here’s one of the most impressive, OMNH 1670, an isolated dorsal. Notice that the tip of the neural spine is ever-so-shallowly bifurcated, which in Apatosaurus indicates a D4, D5, or D6. The low parapophyses and fat transverse processes are similar to D4, but Apatosaurus D4s usually have somewhat broader spines, so I’m guessing this thing is a D5. These things vary and I could easily be off by a position in either direction.

Next to it is D5 of CM 3018, the holotype specimen of Apatosaurus louisae (from Gilmore 1936: plate 25), which has served as the basis for many of the published mass estimates of the genus Apatosaurus. OMNH 1670 is 135 cm tall, compared to 106 cm for D5 of CM 3018. If the rest of the animal scaled the same way, it would have been 1.27^3 = 2 times as massive. Mass estimates for CM 3018 are all over the map, from about 18 tons up to roughly twice that, so the big Oklahoma Apatosaurus was probably in Supersaurus territory, mass-wise, and may have rivaled some of the big titanosaurs (Update: see the two giant diplodocids square off in a cool follow-up post by Supersaurus wrangler Scott Hartman). Here’s a fun rainy-day activity: take any skeletal reconstruction of Apatosaurus, clone it in Photoshop or GIMP, scale it up by 27%, and park it next to the original. It looks a lot bigger. So I’m continually surprised that Apatosaurus is so rarely mentioned in the various roundups of giant sauropods, both in the technical literature and in popular articles online. This vertebra was figured by Stovall (1938)–if I get inspired, I’ll dig up that figure and post it another day (hey, look, I did!).

Fun fact: in Apatosaurus the tallest (most posterior) dorsals are 1.3-1.5 times as tall as D5 (Gilmore 1936: 201). So D10 from this individual was probably between 1.7 and 2 meters tall–not quite in Amphicoelias fragillimus territory but getting closer than I’ll bet most people suspected.

NB: if you try to use the scale bar lying on the centrum of OMNH 1670 to check my numbers, you will get a wonky answer. The problem is that the vertebra is so large that it is almost impossible to get far enough back from it (above it, in this case, since it is lying on a padded pallet) to get a shot free from distortion due to parallax. For this shot, the pallet with the vert was on the floor, and I was standing on top of the tallest ladder in the OMNH collections, leaning out over the vert to get centered over the prezygapophyses, and shooting straight down–in other words, I had done everything possible to minimize the visual distortion. But it still crept in. Anyway, trust the measurements, which I–and presumably Gilmore–made with a good old reliable tape measure.


  • Gilmore, C.W. 1936. Osteology of Apatosaurus with special reference to specimens in the Carnegie Museum. Memoirs of the Carnegie Museum 11:175-300.
  • Stovall, J.W. 1938. The Morrison of Oklahoma and its dinosaurs. Journal of Geology 46:583-600.