Supersaurus, Ultrasaurus and Dystylosaurus in 2019, part 2: what we found in Utah

June 15, 2019

Last time, we reviewed what’s known about Jensen’s three giant sauropods based on published papers (and one abstract). This time, I want to talk a bit about what Matt and I have discovered, and intend to publish when we get around to it.

The Three Baro Jacket

It all followed on from our work on Barosaurus (which for now remains available only as a preprint, becalmed as it is in the peer-review doldrums — mostly my fault). Because of that, we were on the alert for Barosaurus material when we were travelling around Utah in Spring of 2016, and one of the first things we locked onto at the Brigham Young University’s Museum of Paleontology (BYU) was this:

We’ve been informally calling this “Three Baro Jacket”, or “3BJ” for short. But if we’re being formal, it’s specimen BYU 20815, being field jacket 3GR from BYU Locality 601 (The Jensen/Jensen quarry at Jensen, Utah), excavated in 1966. It also has an accession number, JJ/66 (which I didn’t realise was different from the specimen number).

Here it is being winched out of the ground at the Jensen/Jensen quarry, back in 1966 (photo courtesy of Brooks Britt):

This jacket contains — as our name for it suggests — three Barosaurus cervicals. The easiest way to see them is in 3D, using this red-cyan anaglyph, which shows the structure of the block much more informatively than the flat photo above:

(Do you have red-cyan anaglyph glasses? If not get some. They are dirt cheap, and will show you a whole world of morphology. For example, Amazon will send you ten pairs for $3.26, so you can keep two at home and two at work, and give half a dozen to your friends.)

For those stuck in the 2D world, these interpretive drawings should help to pick out the vertebrae from the matrix: they show individually the three vertebrae that we arbitrarily designated as A, B and C in that order.

Characters of Barosaurus cervicals

We spent some time looking pretty closely at these vertebra to figure out what they were — after all, the jacket wasn’t presented to us as “Here are some Barosaurus cervicals”. As we did so, we kept comparing the 3BJ vertebrae with photos we’d taken of the YPM and AMNH Barosaurus cervicals, and published illustrations. And as we did this, we discovered a whole set of distinctive characteristics of Barosaurus cervicals. We will properly describe and illustrate these characters another time, but to briefly summarise:

  • 1. Centra very long relative to vertebral height (measured at the posterior articular surface). This one will come as no surprise.
  • 2. Neural spine low and fairly smooth in profile.
  • 3. Postzygapophyses set forward slightly from posterior margin of centrum — as opposed to set well forward in brachiosaurs, or overhanging the posterior margin in apatosaurs.
  • 4. Parapophysis set much further forward than diapophysis, so that the cervical rib loop projects anteroventrally from the diapophysis.
  • 5. Cervical rib loop very thin anteroventrally (and lateromedially).
  • 6. Distinct hollow “thumb groove” between prezygapophyseal facet and pre-epipophysis.
  • 7. “U”-shaped notch in dorsal view where prezygapophyseal rami meet.
  • 8. Prezygapophyseal rami have two “faces” at right angles: one facing dorsomedially (bearing the prezgapophyseal facet), one facing dorsolaterally.
  • 9. Prezyagpophyseal rami very broad.
  • 10. Process projecting posteriorly from diapophysis.
  • 11. Prezyadiapophyseal lamina sweeps out smoothly to diaphophysis in dorsal view.

(These characters are all illustrated in our 2016 SVPCA talk: check the slides if you want to get a better handle on what we’re describing here. The reason I listed them in the slightly odd order above is so you can easily match them up with the slides.)

Now these vertebrae are well worthy of proper study and description in their own right, and we do plan to give them the attention they deserve. But for today’s story, they have done their part.

What is BYU 9024?

Now, here’s the thing. Literally a couple of yards away from the Three Baro Jacket in BYU collections sits the single longest vertebra of anything ever discovered: our old friend BYU 9024 (what Jensen called BYU 5003), which was originally assigned to Ultrasaurus (Jensen 1985), then reassigned to Supersaurus (Jensen 1987).

Mike compares Jensen’s sculpture of the big Supersaurus cervical BYU 9024 with the actual fossil.

And the more we looked at Barosaurus cervicals, then looked at BYU 9024, then looked back at Barosaurus, the more convinced we became that BYU 9024 is itself a Barosaurus cervical.

You would not immediately think this to look at the bone, as it’s pretty smashed up, and very difficult to interpret from photos, but this anaglyph will help:

As we discussed before, the posterior end looks much taller dorsoventrally than it should, because the postzygapophysis is folded upwards and the ventrolateral processes folded down.

Here’s what we see in BYU 9024 in terms of the characters we picked out from the 3BJ vertebrae. First, in left lateral view, with the characters highlighted in green:

  • 1. Centra very long relative to vertebral height (measured at the posterior articular surface).
  • 2. Neural spine low and fairly smooth in profile.
  • 3. Postzygapophyses set forward slightly from posterior margin of centrum.
  • 4. Parapophysis set much further forward than diapophysis, so that the cervical rib loop projects anteroventrally from the diapophysis.
  • 10. Process projecting posteriorly from diapophysis.

Now in anterodorsal view, with dorsal to the left:

  • 7. “U”-shaped notch in dorsal view where prezygapophyseal rami meet.
  • 8. Prezygapophyseal rami have two “faces” at right angles: one facing dorsomedially (bearing the prezgapophyseal facet), one facing dorsolaterally.
  • 9. Prezyagpophyseal rami very broad.

(It’s not easy to tell from this photo, but the broken-off area of flattish bone highlighted in the circle is part of the dorsolaterally-facing aspect of the prezygapophyseal ramus, where is it merging into the prezygadiapophyseal lamina.)

Three of the characters we saw in 3BJ we couldn’t determine in BYU 9024, due to breakage:

  • 5. Cervical rib loop very thin anteroventrally (and lateromedially).
  • 6. Distinct hollow “thumb groove” between prezygapophyseal facet and pre-epipophysis.
  • 11. Prezyadiapophyseal lamina sweeps out smoothly to diaphophysis in dorsal view.

But the morphology that’s preserved is certainly compatible with all of these. There are also a couple more characters in this vertebra that indicate that it’s Barosaurus, which we were not able to isolate in any of the 3BJ vertebrae:

  • A pair of posteroventrally directed accessory laminae radiating from the part of the centrum surface medial to the diapophysis. (These may be homologous with PCDLs but they seem to come out from under the PODL.)
  • It lacks paired foramina on the ventral surface separated by a midline ridge, as seen in Apatosaurus and WDC Supersaurus. (Thanks to David Lovelace from drawing our attention to that one in a comment on the last post!)

No one or two of these characters is a slam-dunk in isolation. But when you put them all together, they leave us pretty much 100% satisfied that BYU 9024 is a Barosaurus cervical.

How big was the BYU 9024 animal?

Before we say anything at all about this, please first hear our standard disclaimer: any size estimate based on a single bone is necessarily going to be wildly speculative, and could easily be a long way out in either direction.

That said, here’s the thinking behind our best guess.

First, what is the serial position of BYU 9024? We’d like to determine this by comparing with the cervical series of AMNH 6341, which is pretty well preserved — but unfortunately it has never been adequately illustrated and is now impossible to photograph as it is entombed below a walkway in the AMNH public gallery. Here’s the best published illustration, from McIntosh (2005:figure 2.1):

We judge it most similar to C9 or maybe C10, based largely on neural spine bifurcation and general proportions when corrected for distortion.

In AMNH, C9 is 685 mm long and C10 is 737 mm long (McIntosh 2005:table 2.1). Since BYU 9024 is 1370 mm in length, it is exactly twice as long as the C9 and 1.86 times as long as the C10.

I think I speak for all right-thinking people when I say holy crap.

If our identification of BYU 9024 as a C9 of Barosaurus is correct, then we are talking about an animal twice as large in linear dimension as the AMNH specimen whose cast looms over the rotunda (and the one at the Natural History Museum of Utah, which by eye is about the same size). Since the neck of the AMNH specimen is 8.5 m long (Wedel 2007:206–207), that would mean that the neck alone of BYU 9024 would have been 17 m long: longer than most complete sauropods and substantially taller than the mounted Giraffatitan skeleton in Berlin. The length of the whole animal is harder to predict, even if we assume isometry, but if Paul’s (2010:189) length estimate of 27 m for regular Barosaurus is correct, we’re probably looking at a total length exceeding 50 m.

This animal would, other things being equal, be eight times as massive (2 × 2 × 2) as the AMNH Barosaurus. There aren’t a lot of Barosaurus mass estimates out there, but Wedel (2005:217–221) did a lot of careful work to arrive at about 12 tonnes for the Diplodocus carnegii holotype CM 84, which is about the same size as the AMNH Barosaurus. If that’s right, then the BYU 9024 animal might have massed about 8 × 12 = 96 tonnes, which puts it right up there among the heaviest known sauropods: probably the heaviest represented by extant fossils, as the other strong contenders for that title are Maraapunisaurus and Bruhathkayosaurus, both known only from illustrations of now-destroyed specimens.

[UPDATE, the next day: see the next post for more on the serial position of the vertebra and the size of the animal.]

We presented most of this reasoning in our 2016 SVPCA talk, whose abstract and slides are online. (Sadly, there is no recording of the actual talk.)

Tune in for the post after that as we (finally!) reach the part promised by the title of this series, and consider where Jensen’s Big Three genera stand today.



  • Jensen, James A. 1985. Three new sauropod dinosaurs from the Upper Jurassic of Colorado. Great Basin Naturalist 45(4):697–709.
  • Jensen, James A. 1987. New brachiosaur material from the Late Jurassic of Utah and Colorado. Great Basin Naturalist 47(4):592–608.
  • McIntosh, John S. 2005. The genus Barosaurus Marsh (Sauropoda, Diplodocidae). pp. 38-77 in: Virginia Tidwell and Ken Carpenter (eds.), Thunder Lizards: the Sauropodomorph Dinosaurs. Indiana University Press, Bloomington, Indiana. 495 pp.
  • Paul, Gregory S. 2010. Dinosaurs: a Field Guide. A. & C. Black Publishers ltd. London, UK. 320 pp.
  • Wedel, Mathew J. 2005. Postcranial skeletal pneumaticity in sauropods and its implications for mass estimates. pp. 201-228 in Wilson, J. A., and Curry-Rogers, K. (eds.), The Sauropods: Evolution and Paleobiology. University of California Press, Berkeley
  • Wedel, Mathew J. 2007. Postcranial pneumaticity in dinosaurs and the origin of the avian lung. Ph.D dissertation, Integrative Biology, University of California, Berkeley, CA. Advisors: Kevin Padian and Bill Clemens. 290 pages.

23 Responses to “Supersaurus, Ultrasaurus and Dystylosaurus in 2019, part 2: what we found in Utah”

  1. Dan Chure Says:

    The Jensen/Jensen Quarry is in Kensen, IT.

  2. Dan Chure Says:

    Well autocorrect intrudes again. It is in Jensen UT!

  3. Illiterate Scholar Says:

    Oh, so those bones in the glass case next to the Apatosaurus are the real Barosaurus bones? I was there for the T.rex exhibit last month and that glass walk way is in very bad shape. The glass is so fogged up that you can barely see anything. That’s such a waste of a good specimen to be displayed like that. I hope they renovate the glass case.

    Also, the Diplodocus vertebra was removed for studying in the AMNH. I wonder who took it out for studies?

  4. Zachary Miller Says:

    Holy crap.

  5. Andrea Cau Says:

    Thanks for the disclaimer: unfortunately, it is going to be ignored by the Internet.

    I am too old for being impressed by super-sized estimations based on just a single bone.
    [My cynical conclusion reading this post was: oh, look, ANOTHER paleontologist claiming that his super crappy fossil is the biggest dinosaur ever]
    So, my boring-conservative mind asks: what is the smallest size that is a valid alternative explanation? I mean, if we combine all possible factors (position misinterpretation, deformation effects, allometry and so on) what could be the smallest plausible size? Only the latter should be taken as “the size” of this animal, pending more material.

    Sorry for playing the boring guy role, but I am quite annoyed by the number of super-giant dinosaurs created from just one misinterpreted poorly preserved specimen that turned out to be much smaller once revised with a less hyperbolic and more rational approach.
    Dinosaur science does not need another episode in the too long list of “my [censored] is bigger than yours” claims.

    That said, it’s a really interesting specimen, regardless of the claimed size.

  6. Mike Taylor Says:

    Dan, thanks for the geography check. The stupid thing is that I knew Jensen was close to the Utah/Colorado border and looked it up, only to then type the wrong answer into the post! You had me going there with Kensen, IT!

  7. Mike Taylor Says:

    Illiterate Scholar, yes, that right there is by far the most complete and best preserved and prepared Barosaurus neck in the whole world — and for all the scientific value it has down there under the Walkway Of Opaque Glass, they might just as well have buried it back in the Morrison. It really is the most horrible and avoidable tragedy. Your hope that they renovate the glass case seems to me like the wrong solution: the thing to do is get those specimens out of there completely!

    What Diplodocus vertebra are you referring to here?

  8. Mike Taylor Says:

    Andrea, you make an excellent point on size estimates. I think it’s worth doing another (much shorter) post on that, so I won’t respond in detail to this comment. Thanks for the prod.

  9. […] part 2, we concluded that BYU 9024, the large cervical vertebra assigned by Jensen to the Supersaurus […]

  10. […] Next time, we’ll look what Matt and I found in Utah, and what we think it means for Supersaurus and its friends. […]

  11. Mike Taylor Says:

    Andrea, I wrote the promised followup dealing in more detail with the likely size of the BYU 9024 animal. Spoiler: the very shortest the next could be is 13.5 m, but 15 m is very much more likely. These neck lengths may correspond with total body lengths of 43 and 48 m, though those are of course much more succeptible to being wrong due to neck allometry.

  12. illiterate scholar Says:

    Mike Taylor, there’s a Diplodocus vertebra in the AMNH. It’s sort of displayed by itself. You know the hall way that connects the Hall of Saurchia to the other halls? There’s a random Diplodocus vert on display and it that was taken out with a sign that says it was taken away for study. I wonder if you can do the same thing for the Barosaurus neck?

    I think I might still have a picture of that Diplodocus vert somewhere in my PC.

  13. Mike Taylor Says:

    Interesting, illiterate scholar. But I think the chances of having the Barosaurus presacral column removed for study are pretty poor. Apart from anything else, there’s nowhere to put them all. And it would be a major operation to take up that walkway floor and get them out of there. Maybe they’d do it for one of their own researchers who could spend a month on them, but not for a visitor who’d be in and out in a couple of days.

  14. Illiterate Scholar Says:

    Would they at least take it out for you to get some good high quality photos? It is quite ridiculous that a world famous institution like the AMNH would make it hard for people to study their specimen.

  15. Mike Taylor Says:

    No, I don’t think the AMNH are in a position to “at least” take their Barosaurus presacrals out for photography. It’s not as simple as you make it sound here, unfortunately. They are so positioned that they’d need to shut down the most popular gallery in the whole museum for multiple days and perform a lot of physically demanding work that would require specialists to handle extremely heavy and fragile panes of glass, and even more fragile vertebrae. I’m not saying it could never be done, but it would be a very significant undertaking.

  16. […] surveyed what we know from the published literature about Jensen’s Big Three sauropods, and what Matt and I concluded about its big cervical BYU 9024, and though a bit more about the size of the BYU 9024 animal, it’s finally time to consider […]

  17. […] you don’t have the 3D glass that you need to see this, get some. Seriously, how many times do I have to tell […]

  18. […] a problem arises: Matt and I are about as certain as we can be that the big cervical verebra BYU 9024 is Barosaurus. That means there are two possibilities: either the cervical been wrongly referred to the […]

  19. […] wait, wait. We’ve shown that there are probably two big diplodocids in the Dry Mesa quarry: Barosaurus (represented by the […]

  20. […] you’ve been following along, you’ll remember that Matt and I are convinced that BYU 9024, the big cervical vertebra that has been referred to Supersaurus, actually belongs to a gia…. If we’re right about, then it means one of two things: either Supersaurus synonymous with […]

  21. Maciej Z. Says:

    There is another possibility: BYU 9024 (and maybe other specimens) is similar to Barosaurus, but it is not Barosaurus. I test this possibility by modifying OTU “Supersaurus_vivianae_BYU+” in Tschopp et al. (2015) matrix. I deleted all non-cervical codings in “Supersaurus_vivianae_BYU+”, so they are: ?????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????1?11?011001?0???0???????????????????1011101002100011?11?112?000?10?????????????????????0????1???????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????
    If BYU 9024 is Barosaurus, it should group with Barosaurus. Instead, “Supersaurus_vivianae_BYU+” is sister taxon to Jimbo, as in original analysis, far away from Barosaurus, with basic tree topology as in Tschopp et al. I don’t know why this is so. Maybe Tschopp et al. don’t include some of Barosaurus characters? (at least first of Your characters is included as ch. 192).
    Tschopp, E., Mateus, O. & Benson, R.B.J. (2015) “A specimen-level phylogenetic analysis and taxonomic revision of Diplodocidae (Dinosauria, Sauropoda)” PeerJ, 3, e857. doi:10.7717/peerj.857

  22. Mike Taylor Says:

    Really interesting, Maciej, thanks for running that.

    I think what’s going on is that the Tschopp et al. matrix lacks a lot of the Barosaurus cervical characters that we’ve only recently identified, and that when those are added, we’ll see BYU 9024 grouping accordingly. But this is a valuable warning to run that analysis and see.

  23. hopdobby Says:

    Brian Curtice will give a talk at the SVP 2021 conference regarding new sauropod material from the Dry Mesa Quarry that he refers to Supersaurus vivianae based on comparisons with the caudals of WDC DMJ-021. The caudal vertebrae from the Supersaurus type locality are almost certainly those in the BYU collections that Lovelace et al. (2008) refer to Supersaurus vivianae but which are not described, and because Curtice will note in his abstract that the BYU caudals are similar to those of Barosaurus, it’d be interesting to see what bearing this material has on any possible affinity of Supersaurus with Barosaurus.

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