Here’s a bit of light relief, in the middle of all those looong posts about Supersaurus and its buddies. When Matt and I were at NAMAL on the last day of the 2016 Sauropocalypse, we took a bunch of tourist shots. Two of them were of a skull and first three cervical vertebrae from what I take to be Diplodocus or something close, and happened to be from sufficiently close angles that they make a pretty good anaglyph. Here it is!

(If you don’t have the 3D glasses that you need to see this, get some. Seriously, how many times do I have to tell you?)

If anyone out there is familiar with NAMAL (on indeed with diplodocid skulls) and can confirm or contradict my identification, I’d appreciate it. Best of all would be a photo of the signage associated with this specimen, such as I should have taken.

By the way, if you’re not used to the ways of sauropods, you might be thinking “Mike, you dummy, there are only two vertebrae there”. But in saropods, the atlas (1st cervical) is a tiny, inconsequential element that frequently fuses to the axis (2nd cervical). So what looks like the first cervical here is really 1+2. If you look closely, you can see the blades of the atlas projecting backwards and upwards, across the surface of the axis.


Having 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 having thought a bit more about the size of the BYU 9024 animal, we’re getting to the point where we can consider what all this means for Jensen’s taxa.

The Supersaurus pelvis BYU 13018 in right lateral view, at the North American Museum of Ancient Life (NAMAL). Signage reads: “Supersaurus pelvis. In 1988 the pelvis of Supersaurus was discovered at Dry Mesa Quarry. Brian Versey, Cliff Miles and Ken Stadtman of Brigham Young University’s Earth Science Museum found the pelvis while they were trying to close the quarry for the season. The discovery generated a huge media event, making headlines around the world. This pelvis is the largest dinosaur bone complex ever discovered. It is on display here for the very first time. Specimen on loan from Brigham Young University’s Earth Science Museum. Late Jurassic/Early Cretaceous (about 144 million years ago)

As Curtice and Stadtman (2002:36-39) pointed out, Supersaurus is actually known from quite a lot of material, all assigned to the holotype individual. I’ll quote them at length rather than paraphrasing, but if you want a tabular summary, you can skip the quote and pick up down below.

Supersaurus vivianae roll call

The name “Supersaurus” first appeared in a Reader’s Digest article (George, 1973) describing a pair of 8′ long scapulocoracoids uncovered from Dry Mesa Dinosaur Quarry near Delta, Colorado. When formally described (Jensen, 1985) a number of elements were referred to the holotype including the left scapulocoracoid discovered in 1972 (BYU 9025), a right scapulocoracoid (BYU 12962), a right ischium (BYU 12946), a distal proximal caudal vertebra (BYU 12843) and 12 articulated mid-caudal vertebrae (BYU 9084). An additional caudal vertebra (BYU 9077) is referred to (and figured as) Supersaurus in the text of Jensen (1985). The specimen numbers used in Jensen (1985), no longer valid, have created confusion in the literature (e.g., Paul, 1988) and thus current BYU specimen numbers are used here throughout.

Jensen (1987) later referred a mid-cervical vertebra (BYU 9024) and Curtice and Curtice (1996) a proximal caudal vertebra (BYU 9045), both originally assigned to Ultrasauros, to Supersaurus. Numerous additional elements belong to Supersaurus, including a left ischium (BYU 12555), which is clearly the mate to the referred right ischium (BYU 12946), a right pubis (BYU 12424), a carpal (BYU 12390), a phalanx (BYU 9000), a left ulna (BYU 13744), at least five caudal vertebrae (BYU 4839, 9045, 12639, 12819, 12843) and a pelvis (BYU 13018) consisting of a left ilium and four sacral vertebrae.

Jensen never referred the two Supersaurus scapulocoracoids to the same individual due to a 260 mm discrepancy in length. Stripping away the paint and resin on BYU 9025 revealed the proximal end had been inadvertently lengthened during preservation. Close examination of the actual bone surface nets a total scapulocoracoid length less than 50 mm longer than BYU 12962, an amount easily accounted for by scapular variation and thus here both are referred to the same individual. Concerning the large brachiosaur scapulocoracoid (BYU 9462) Jensen (1985) listed as part of the material belonging to Ultrasauros, it is demonstrably smaller than the largest Tendaguru scapula and has been referred to Brachiosaurus sp. (Curtice and Curtice, 1996; Curtice et al., 1996). As such all exceptionally large sauropod elements from Dry Mesa Dinosaur Quarry can be referred to one of two individuals, one a Supersaurus and one a Brachiosaurus.

A dorsal vertebra (BYU 9044) referred to Supersaurus (Curtice and Curtice, 1996; Curtice et al., 1996) results in Ultrasaurus macintoshi becoming a junior synonym of Supersaurus vivianae, as BYU 9044 was the type specimen of Ultrasauros. A second dorsal vertebra, BYU 12814, is also here referred to Supersaurus based on its similarities to BYU 9044. All of the three large dorsal vertebrae mentioned herein were found within the confines of the paired Supersaurus scapulae further strengthening the suggestion all of the large diplodocid elements belong to a single individual.

(Yes, it really does say “a distal proximal caudal vertebra”.)

Curtice and Stadtman say that the pelvis consists of left ilium plus four sacral vertebrae; but as the photo above clearly shows, it is the right ilium that is preserved.

Here is a summary table, in standard anatomical order:

Specimen Element Referred by
9024 Mid-cervical vertebra Jensen 1987
12814 Anterior dorsal vertebra Curtice & Stadtman 2002
9044 Posterior dorsal vertebra Curtice et al. 1996
13018 Pelvis (right ilium, four sacral vertebrae) Curtice & Stadtman 2002
9045 Proximal caudal vertebra Curtice & Curtice 1996
12843 “Distal proximal” caudal vertebra Jensen 1985
9084 Twelve articulated mid-caudal vertebrae Jensen 1985
9077 Caudal vertebra Jensen 1985
4839 Caudal vertebra Curtice & Stadtman 2002
9045 Caudal vertebra Curtice & Stadtman 2002
12639 Caudal vertebra Curtice & Stadtman 2002
12819 Caudal vertebra Curtice & Stadtman 2002
12843 Caudal vertebra Curtice & Stadtman 2002
9025 Left scapulocoracoid Holotype
12962 Right scapulocoracoid Jensen 1985
13744 Left ulna Curtice & Stadtman 2002
12390 Carpal Curtice & Stadtman 2002
12424 Right pubis Curtice & Stadtman 2002
12946 Right ischium Jensen 1985
12555 Left ischium Curtice & Stadtman 2002
9000 Phalanx Curtice & Stadtman 2002

This is an impressively complete specimen — especially for a giant sauropod, as these tend only to survive in the form of isolated elements.

But is it really one specimen? That’s the subject of the next post.

(This post is rather slender by recent standards. That’s because I accidentally hit Publish when it was only half written. Rather than leave it to slowly change as I write more, I think it’s better to let this first half stand as its own post, and write the rest as its own post next time.)



  • Curtice, Brian D. and Linda J. Curtice. 1996. Death of a dinosaur: a reevaluation of Ultrasauros macintoshi (Jensen 1985). Journal of Vertebrae Paleontology 16(3):26A.
  • Curtice, Brian D. and Kenneth L. Stadtman. 2001. The demise of Dystylosaurus edwini and a revision of Supersaurus vivianae. Western Association of Vertebrate Paleontologists and Mesa Southwest Museum and Southwest Paleontologists Symposium, Bulletin 8:33-40.
  • Curtice, Brian D., Kenneth L. Stadtman and Linda J. Curtice. 1996. A reassessment of Ultrasauros macintoshi (Jensen, 1985). M. Morales (ed.), “The continental Jurassic”. Museum of Northern Arizona Bulletin 60:87–95.
  • 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.


In part 2, we concluded that BYU 9024, the large cervical vertebra assigned by Jensen to the Supersaurus holotype individual, is in fact a perfectly well-behaved Barosaurus cervical — just a much, much bigger one than we’ve been used to seeing. Although we heavily disclaimered our size estimates, Andrea Cau quite rightly commented:

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

Andrea is right that we should take a moment to think a bit more about the possible size implications of BYU 9024.

BYU 9024, the huge cervical vertebra assigned to Supersaurus but which is actually Barosaurus, in left dorsolateral view, lying on its right side with anterior to the right. In front of it, for scale, a Diplodocus cervical from about the same serial position. (Note that the Diplodocus vertebra here appears proportionally bigger than it really is, due to being much closer to the camera.)

What we know for sure is that the vertebra is 1380 mm long (give or take a centimeter or two due to the difficulties of measuring big complex bones in an objective way, something we should write about separately some time.)

We are 99% certain that the bone is a Barosaurus cervical.

We are much less certain about the serial position of that bone. When we were at BYU, we concluded that it most resembled C9 of the AMNH specimen, but I honestly can’t remember the detail of our reasoning (can you, Matt?) and our scanned notebooks don’t offer much in the way of help. We know from McIntosh (2005) that the neural spine of C8 is unsplit and that C9 has the first hint of a cleft.  How does that compare with BYU 9024? Here’s a photo to help you decide:

BYU 9024, large cervical vertebra in left dorsolateral view, inverted (i.e. with dorsal towards us and anterior to the right). Note the shallow cleft between metapophyses at bottom left.

And here’s an anaglyph, to help you appreciate the 3D structure. (Don’t have any red-cyan glasses? GET SOME!)

BYU 9024, oriented similarly to the previous photograph.

The morphology around the crown of the neural spine is difficult to interpret, partly just because the fossil itself is a bit smashed up and partly because the bone, the (minimal) restoration and the matrix are such similar colours. But here’s my best attempt to draw out what’s happening, zoomed in from last non-anaglyph photo:

As you start at the prezygapophyses and work backwards, the SPRLs fade out some way before you reach the crown, and disappear at or before what appears to be an ossified midline ligament scar projecting anteriorly from very near the top of the vertebra. Posterior to that are two small, tab-like metapophyses that appear almost like separate osteological features.

Now this is a very strange arrangement. Nothing like it occurs in any of the cervicals of Diplodocus, where all the way from C3 back to the last cervical, the SPRLs run continuously all the way up from the prezygs to the metapophyses:

Hatcher (1901:plate V). Diplodocus carnegii holotype CM 84, cervical vertebra 2-15 in anterior view.

What we’d love to do of course is compare this morphology with a similar plate of the AMNH Barosaurus cervicals in anterior view, but no such plate exists and no such photos can be taken due to the ongoing entombment of the vertebrae. So we’re reduced to feeding on scraps. McIntosh (2005:47) says:

The neural spine of cervical 8 is flat across the top, and that of cervical 9 shows the first trace of a divided spine (Fig. 2.2A). This division increases gradually in sequential vertebrae, being moderately developed in cervicals 12 and 13, and as a deep V-shape in cervicals 15 and 16.

Sadly, McIntosh illustrates only cervicals 8 and 13 in anterior view: Fig 2.2A does not illustrate C9, as the text implies. And neither of the illustrated vertebrae much resembles what we see in BYU 9024.

So while in 2016 we interpreted BYU 9024 is having “the first trace of a divided spine”, we do hold open the possibility that what we’re seeing is a vertebra in which the spine bifurcation is a little more developed than we’d realised, but with strange morphology that does not correspond closely to any well-preserved vertebra we’ve seen of any sauropod. (Most Barosaurus cervicals are either crushed and damaged; the well preserved ones outside of the AMNH walkway tomb are from a more anterior part of the neck where there is no bifurcation of the spine.)

There is one more possibility. Here is a truly lovely (privately owned) Barosaurus cervical in the prep lab at the North American Museum of Ancient Life (NAMAL):

Uncrushed Barosaurus cervical vertebra, serial position uncertain, in the NAMAL prep lab.

In this blessedly undistorted vertebra, we can see that the summit of the neural spine is flared, with laterally projecting laminae that are likely homologous with metapophyses. (The vertebra is symmetrical in this respect.) Might it be possible that the tab-like metapophyses of BYU 9024 were like this in life, but have been folded upwards post-mortem?

All of this leaves the serial position of the vertebra far from certain. But what we can do is compare it with the lengths of all the known AMNH Barosaurus vertebrae. Columns 1 and 2 in the table below show the serial position and total length of the AMNH cervicals. Column 3 shows the factor by which the 1370 mm length of BYU 9024 exceeds the relevant cervical, and column 4 shows the corresponding estimate for total neck length, based on 8.5 m (Wedel 2007:206–207) for AMNH Barosaurus.

Cv# Length (mm) BYU 9224 ratio BYU 9024 neck length
8 618 2.217 18.84
9 685 2.000 17.00
10 737 1.859 15.80
11 775 1.768 15.03
12 813 1.685 14.32
13 850 1.612 13.70
14 865 1.584 13.46
15 840 1.631 13.86
16 750 1.827 15.53

So to finally answer Andrea’s question from waaay back at the start of this post, the smallest possible interpretation of the BYU 9024 animal gives it a neck 1.584 times as long as that of the AMNH individual, which comes out around 13.5 m (and implies a total length of maybe 43 m).

But I don’t at all think that’s right: I am confident that the serial position of BYU 9024 is some way anterior to C14, likely no further back than C11 — which gives us a neck at least 15 m long (and a total length of maybe 48 m and a mass of maybe 12 × 1.768^3 = 66 tonnes).



  • Hatcher, Jonathan B. 1901. Diplodocus (Marsh): its osteology, taxonomy and probable habits, with a restoration of the skeleton. Memoirs of the Carnegie Museum 1:1-63 and plates I-XIII.
  • 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.
  • 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.

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.

It’s time to revisit everyone’s favourite trio of apocryphal super-sized sauropods! (Yes, we’ve talked about this before, but only very briefly, and that was nearly eleven years ago. Things have moved on since then.)

John Sibbick’s classic artwork showing three giant sauropods, including two of Jensen’s three. On the left is Seismosaurus Gillette 1991, which is not directly relevant to today’s post. In the middle is the brachiosaur Ultrasaurus, and on the right the diplodocid Supersaurus. Poor, unloved Dystylosaurus doesn’t get a look-in — perhaps because this was drawn before that name had been announced?

Here’s the story so far …

1. Jensen’s discoveries

In a series of expeditions beginning in April 1972, following a tip from uranium prospectors Eddie and Vivian Jones, Jim Jensen found numerous massive sauropod fossils in the Dry Mesa quarry, southwest Colorado. The Supersaurus pelvis at least was still in the ground as late as August 1972 (George 1973b:51–52) and the excavations continued into 1982 (Jensen 1985:697).

Eschewing such pedestrian venues as Science, Nature or indeed the Journal of Vertebrate Paleontology, Jensen first told the world about these finds in the popular press. The oldest published work I have that mentions them is Jean George’s (1973b) piece in Reader’s Digest, condensed from the same author’s piece in the Denver Post’s Empire Magazine earlier that year (George 1973a), which I have not been able to obtain.

“‘Supersaurus,’ as we shall call him, now awaits an official name and taxonomic classification”, wrote George (1973b:53) — but the piece does not mention the names “Ultrasaurus” or “Dystylosaurus” and I’ve not been able to determine when those informal names became known to the world. (Can anyone help?) We do know that Jensen was informally using the name “Ultrasaurus” as early as 1979 (Curtice et al. 1996:87).

Anyway, for reasons that have never been very clear, Jensen concluded that the remains represented not one, not two, but three gigantic new genera: a diplodocid, which he named “Supersaurus”; a brachiosaurid, which he named “Ultrasaurus”; and an unidentifiable which he named “Dystylosaurus”. All these names were informal at this point, like “Angloposeidon” and “The Archbishop”.

2. Kim’s accidental Ultrasaurus

After Jensen had been using these names informally for some years, Kim (1983) named an indeterminate Korean sauropod as Ultrasaurus tabriensis. Based on the abstract (the only part of the paper in English, apart from the figure captions), Kim was aware of Jensen’s dinosaurs: “Judging by the large size of the ulna the animal may belong to the sauropod dinosaur, which is much bigger than Supersaurus. A new name Ultrasaurus tabriensis is proposed for the convenience of the further study.” While this does not quite go so far as to say that Kim considered the ulna to belong to the same genus as Jensen’s brachiosaur, it seems unlikely that he was aware of Supersaurus but not of Ultrasaurus, and landed independently on the latter name by coincidence.

Either way, in naming his species, Kim inadvertently preoccupied Jensen’s chosen genus name, with conseqences that we shall see below. By all accounts, the material the Kim described is in any case indeterminate, and the genus is generally considered a nomen nudum (e.g. Olshevsky 1991:139, Glut 1997:1001).

Kim 1983, plate 1, parts 1-3, illustrating the proximal portion of the huge “ulna” that the name Ultrasaurus tabriensis was founded on. As is apparent, this is actually the proximal end of a humerus, meaning that the animal is rather less large than Kim supposed — although the 42 cm width across the proximal end is still nothing to be sniffed at. It is about 71% the width of the 59 cm-wide humerus of the Giraffatitan brancai paralectotype MB.R.2181 (previously HMN SII).

Two years after this, and presumably unaware of Kim’s paper or incorrectly assuming his informal use of the name “Ultrasaurus” gave him priority, Jensen published a formal account of his finds, naming them (Jensen 1985). Unfortunately, while the paper does contain formal nomenclatural acts that are valid according to the rules of the ICZN, Jensen did not explain his reasoning for the creation of the new genera, and his selection of type material was problematic, as we shall see below. Also, the specimen numbers that he used have been superseded — I do not know why, but my guess would be that he re-used numbers that were already in use for other specimens, so his own material had to be given new numbers.

3. Jensen’s three sauropods

The following three genera (with their type species) were named, in this order:

1. Supersaurus vivianae, based on the holotype BYU 9025 (BYU 5500 of his usage), a scapulocoracoid measuring 2.44 m in length. To this, he referred an even larger scapulocoracoid whose length he gives as 2.70 m (though Curtice and Stadtman 2002:39 found that this length to be due to optimistic reconstruction); an ischium; either one or two mid-caudal vertebrae (his paper contradicts itself on this); and a sequence of 12 articulated caudal vertebrae. Unfortunately, Jensen’s use of specimen numbers for most of these referred elements is inconsistent, but he is at least consistent in referring to the second scapulocoracoid as BYU 5501.

Supersaurus vivianae holotype scapulocoracoid BYU 9025, photographed at the North American Museum of Natural Life. The exhibit text reads: “Supersaurus scapula and coracoid. This is the actual Supersaurus bone that the world saw when the announcement was made of the new animal’s discovery in 1972. The scapula lay in the ground for five more years, waiting for the collection of other fossils that lay in the path of excavation. The flatness of the bone presented a challenge to “Dinosaur Jim” Jensen, who had to figure out a way to get the bone safely out of the ground. He finally accomplished this by cutting the scapula into three pieces. In 1988, Cliff Miles, Brian Versey and Clark Miles prepared the bone for study. It is still one of the largest dinosaur bones known in the world. Specimen on load from Brigham Young University’s Earth Science Museum. Late Jurassic/Early Cretaceous (about 144 million years ago)

2. Ultrasaurus macintoshi, based on the holotype BYU 9044 (BYU 5000 of his usage), a dorsal vertebra measuring 1.33 m in height. To this, he referred BYU 9462 (BYU 5001 of his usage), a scapulocoracoid measuring 2.7 m in length; BYU 9024 (BYU 5003 of his usage), a huge cervical vertebra; and an anterior caudal vertebra.

Ultrasaurus macintoshi holotype dorsal vertebra BYU 9044, photographed at the North American Museum of Natural Life. (It’s incredibly hard to photograph well because it’s behind reflective glass.)

3. Dystylosaurus edwini, based on the holotype BYU 4503 (BYU 5750 of his usage), a dorsal vertebra. He did not refer any other material to this taxon, and considered it “Family indeterminate” commenting that it “no doubt represents a new sauropod family”. Poor Dystylosaurus has always been the unloved member of this group, and pretty much ignored in the literature aside from the Curtice & Stadtman (2002) synonymisation paper discussed below.

Dystylosaurus edwini holotype BYU 4503, a diplodocoid anterior dorsal vertebra.

In a subsequent paper, Jensen (1987:600–602) removed the big cervical BYU 9024 (BYU 5003 of his usage) from Ultrasauros and reassigned it to Diplodocidae. The text of this paper never refers it to Supersaurus vivianae in particular, but it is illustrated and captioned as belonging to that taxon (Jensen 1987:figures 7A-B, 8C), and this assignment is generally assumed to have been meant.

When Jensen became aware of Kim’s (1983) preoccupation of the name Ultrasaurus, he recognised that his own genus needed a new name. At his suggestion, Olshevsky (1991) erected the replacement name Ultrasauros (with a single-letter spelling difference) for Jensen’s taxon based on the dorsal vertebra BYU 9044. We will use this revised spelling hereon, and the taxon Ultrasaurus Kim 1983 is of no further interest to this story.

The relevant extract from Olshevsky (1991:139).

4. Curtice’s synonymies

This was how things stood, with Jensen’s assignment of the material to his three new genera standing unchallenged, until Brian Curtice came on the scene in the mid 1990s. In a series of three publications (two papers, one abstract), he first synonymised Ultrasauros with Supersaurus, then Dystylosaurus also with Supersaurus, and finally (tentatively) Supersaurus itself with Barosarus. If Curtice’s suggestions were all correct, then there were no new sauropods from Jensen’s work in the the Dry Mesa quarry, just a lot of Barosaurus material.

Was he right? We’ll now consider each of the three publications in turn.

First, Ultrasauros. Jensen had always considered this genus to be a brachiosaurid due to the morphology of the scapulocoracoid BYU 9462 — and indeed this element does seem to be brachiosaurid. Unfortunately, he did not found the taxon on this element, but on the dorsal vertebra BYU 9044. Curtice et al. (1996) re-examined this element, and argued convincingly that it was not an anterior dorsal from a brachiosaurid, as Jensen had thought, but a posterior dorsal from a diplodocid. Since its neural spine morphology matches that of the first preserved sacral spine (S2) of the Supersaurus sacrum, and since it was found between the two Supersaurus scapulocoracoids, Curtice et al. (1996:94) considered BYU 9044 to be a vertebra of Supersaurus (belonging to the holotype individual), and therefore concluded that Ultrasauros was a junior subjective synonym of Supersaurus. They inferred that the referred Ultrasauros scapulocoracoid BYU 9462 therefore did not belong to the same species as the type, since it was brachiosaurid, and referred it to Brachiosaurus sp.

We consider all of Curtice et al.’s (1996) arguments well-founded and convincing, and agree with their conclusions. As a result, both spellings of Jensen’s brachiosaurid genus are now discarded: Ultrasaurus as a nomen dubium, and Ultrasauros as a junior synonym.

Curtice et al. (1996:figure 2). “Uncrushed” Supersaurus vivianae caudal dorsal, BYU 9044, right lateral view.

A few years later, Curtice and Stadtman (2002) took aim at Dystylosaurus. Jensen had argued that it was unique because of the paired centroprezygapophyseal laminae that supported each prezygapophysis from below — and it was from this feature than the genus took its name. But Curtice and Stadtman pointed out that this supposedly unique feature is in fact almost ubiquitous in diplodocids. Because it, too, was found between the two Supersaurus scapulae (close to the Ultrasaurus dorsal), Curtice and Stadtman referred it, too, to Supersaurus, thereby collapsing all three of Jensen’s taxa into one. This argument, too, is well supported and has been generally accepted.

Finally, in a sole-authored abstract, Curtice (2003) hedged about whether he considered Supersaurus to be Barosaurus. I will quote directly, as the line of reasoning is vague and difficult to summarise:

The question of is Supersaurus truly a distinct genus from Barosaurus is now testable. The former Dystylosaurus dorsal vertebra provides an autapomorphy for Supersaurus, that being a strongly reduced bifid neural spine on dorsal four. This loss of bifidity is important for in all other diplodocids the neural spine is still deeply bifurcated on dorsal four. Only Barosaurus has a reduction in cleft depth that far forward in the dorsal column. Supersaurus has all but lost the cleft, more closely resembling the sixth dorsal vertebra of Barosaurus than the fourth.

It is disappointing that this abstract never became a more rigorously argued paper, because the conclusion here is highly equivocal. Curtice appears to be saying that Supersaurus is distinct from Barosaurus — but only on the basis of bifidity reducing two vertebrae more anteriorly in Supersaurus. In other words, he seems to be suggesting that the two taxa are indisinguishable aside from this rather minor difference.

At any rate, this speculation in a conference abstract has generally been ignored, and Supersaurus considered a valid and distinct genus.

5. Jimbo the WDC Supersaurus

In 2008, Lovelace et al. (2008, duh) described WDC DMJ-021, a new specimen of Supersaurus vivianae at the Wyoming Dinosaur Center that is known informally as “Jimbo”. (Confusingly, they refer to the Supersaurus holotype scapulocoracoid by yet a third specimen number, BYU 12962; but we will continue to use BYU 9025 here. It is possible that BYU 12962 is the revised specimen number of the referred scapulocoracoid, not the holotype.)

Lovelace et al. (2008) did not justify in detail their referral of Jimbo to Supersaurus. The closest the come is this brief passage on page 529–530:

While a scapula is not known for WDC DMJ-021, other elements are identical to axial elements referred to the type individual of Supersaurus. Referral of all material is supported by relative position within their respective quarries (Curtice and Stadtman 2001; Lovelace 2006), size of the skeletal elements, and congruence of phylogenetically significant diplodocid characters between the scapula and referred material.

All of this is kind of weaselly. What it amounts to is this: vertebrae are “identical” to those referred to the BYU Supersaurus (but not really, as we’ll see), and the elements are really big, and the Supersaurus holoype scap comes out in about the same place as Jimbo in a phylogenetic analysis if you code them up separately. This is weak sauce, and I would really have liked to see a much more explicit “Jimbo shares synapomorphies X, Y and Z with BYU Supersaurus” section.

Among the ways in which the justification for this assignment disappoints is that the presacrals that are described as “identical” to the BYU elements are not at all well preserved (Lovelace et al. 2008:figures 3D–E, 4A, 5A): in particular C13, presumably the best preserved cervicals as it is the only one illustrated, is missing the condyle, prezygapophyses and neural spine. It’s not possible to be sure in light of the small monochrome illustrations in the paper, but it does not seem likely that these elements can be reliably assessed as identical to the BYU cervical.

Lovelace et al. (2008:figure 3). Lateral views of cervical vertebrae from A, Diplodocus carnegii (Hatcher 1901); B, Barosaurus lentus (Lull 1919); C, Apatosaurus louisae (Gilmore 1936); D and E, Supersaurus vivianae; demonstrating pneumatic modifications of centra. Supersaurus has the least amount of modification with minimal size for pneumatopores. Internal structure is similar to that seen in other diplodocids (Janensch, 1947). Left lateral view of Cv.13 (D, missing the condyle, prezygapophyses and neural spine; length of incomplete centra 94cm). E, cross section through Cv.11, 5cm posterior of the diapophysis.

The big surprise in the Jimbo paper is that in the phylogenetic analysis (Lovelace et al. 2008:figure 14), the compound BYU+WDC Supersaurus is recovered as an apatosaurine, the sister taxon to Apatosaurus, rather than as a diplodocine as had been assumed in previous studies due to its resemblance to the diplodocine Barosaurus.

The huge specimen-level phylogenetic analysis of diplodocoids by Tschopp et al. (2015) corroborated Lovelace et al’s (2008) referral of the WDC specimen to Supersaurus vivianae, as the two species were sister groups in all most parsimonious trees, with quite strong character support (Tschopp et al. 2015:187). But it placed the Supersaurus clade at the base of Diplodocinae, not within Apatosaurinae as Lovelace et al. (2008) had found.

This, then, was the state of play when Matt and I started to work on Supersaurus during the 2016 Sauropocalypse: Ultrasauros and Dystylosaurus had both been sunk into Supersaurus, and the WDC specimen had been referred to the same species.

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



  • Curtice, Brian D. 2003. Two genera down, one to go? The potential synonomy [sic] of Supersaurus with Barosaurus. Southwest Paleontological Symposium 2003, Guide to Presentations. Mesa Southwest Museum, January 25 2003. Unpaginated.
  • Curtice, Brian D. and Kenneth L. Stadtman. 2001. The demise of Dystylosaurus edwini and a revision of Supersaurus vivianae. Western Association of Vertebrate Paleontologists and Mesa Southwest Museum and Southwest Paleontologists Symposium, Bulletin 8:33-40.
  • Curtice, Brian D., Kenneth L. Stadtman and Linda J. Curtice. 1996. A reassessment of Ultrasauros macintoshi (Jensen, 1985). M. Morales (ed.), “The continental Jurassic”. Museum of Northern Arizona Bulletin 60:87–95.
  • George, Jean. 1973a. Supersaurus, the biggest brute ever. Denver Post, Empire Magazine. May 13, 1973.
  • George, Jean. 1973b. Supersaurus, the biggest brute ever. Reader’s Digest (June 1973):51–56.
  • Glut, Donald F. 1997. Dinosaurs: the Encyclopedia. McFarland & Company Inc., Jefferson. 1076 pp.
  • 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.
  • Kim, Hang-mook. 1983. Cretaceous dinosaurs from South Korea. Journal of the Geological Society of Korea 19(3):115–126.
  • Lovelace, David M., Scott A. Hartman and William R. Wahl. 2008. Morphology of a specimen of Supersaurus (Dinosauria, Sauropoda) from the Morrison Formation of Wyoming, and a re-evaluation of diplodocid phylogeny. Arquivos do Museu Nacional, Rio de Janeiro 65(4):527–544.
  • Olshevsky, George. A revision of the parainfraclass Archosauria Cope, 1869, excluding the advanced Crocodylia. Mesozoic Meanderings 2:1–196.
  • Tschopp, Emanuel, Octávio Mateus and Roger B. J. Benson. 2015. A specimen-level phylogenetic analysis and taxonomic revision of Diplodocidae (Dinosauria, Sauropoda). PeerJ 2:e857. doi:10.7717/peerj.857


In a word, amazingly. After 6 days (counting public galleries last Sunday), 4300 photos, 55 videos, dozens of pages of notes, and hundreds of measurements, we’re tired, happy, and buzzing with new observations and ideas.

We caught up with some old friends. Here Mike is showing an entirely normal and healthy level of excitement about meeting CM 584, a specimen of Camarasaurus from Sheep Creek, Wyoming. You may recognize this view of these dorsals from Figure 9 in our 2013 PeerJ paper.

We spent an inordinate amount of time in the public galleries, checking out the mounted skeletons of Apatosaurus and Diplodocus (and Gilmore’s baby Cam, and the two tyrannosaurs, and, and…).

I had planned a trip to the Carnegie primarily to have another look at the Haplocanthosaurus holotypes, CM 572 and CM 879. I was also happy for the chance to photograph and measure these vertebrae, CM 36034, which I think have never been formally described or referred to Haplocanthosaurus. As far as I know, other than a brief mention in McIntosh (1981) they have not been published on at all. I’m planning on changing that in the near future, as part of the larger Haplocanthosaurus project that now bestrides my career like a colossus.

The real colossus of the trip was CM 555, which we’ve already blogged about a couple of times. Just laying out all of the vertebrae and logging serial changes was hugely useful.

Incidentally, in previous posts and some upcoming videos, we’ve referred to this specimen as Brontosaurus excelsus, because McIntosh (1981) said that it might belong to Apatosaurus excelsus. I was so busy measuring and photographing stuff that it wasn’t until Friday that I realized that McIntosh made that call because CM 555 is from the same locality as CM 563, now UWGM 15556, which was long thought to be Apatosaurus excelsus but which is now (i.e., Tschopp et al. 2015) referred to Brontosaurus parvus. So CM 555 is almost certainly B. parvus, not B. excelsus, and in comparing the specimen to Gilmore’s (1936) plates of CM 563, Mike and I thought they were a very good match.

Finding the tray of CM 555 cervical ribs was a huge moment. It added a ton of work to our to-do lists. First we had to match the ribs to their vertebrae. Most of them had field numbers, but some didn’t. Quite a few were broken and needed to be repaired – that’s what I’m doing in the above photo. Then they all had to be measured and photographed.

It’s amazing how useful it was to be able to reassociate the vertebrae with their ribs. We only did the full reassembly for c6, in part because it was the most complete and perfect of all of the vertebrae, and in part because we simply ran out of time. As Mike observed in his recent post, it was stunning how the apatosaurine identity of the specimen snapped into focus as soon as we could see a whole cervical vertebra put back together with all of its bits.

We also measured and photographed the limb bones, including the bite marks on the radius (above, in two pieces) and ulna (below, one piece). Those will of course go into the description.

And there WILL BE a description. We measured and photographed every element, shot video of many of them, and took pages and pages of notes. Describing even an incomplete sauropod skeleton is a big job, so don’t expect that paper this year, but it will be along in due course. CM 555 may not be the most complete Brontosaurus skeleton in the world, but our ambition is to make it the best-documented.

In the meantime, we hopefully left things better documented than they had been. All of the separate bits of the CM 555 vertebrae – the centra, arches, and cervicals ribs – now have the cervical numbers written on in archival ink (with permission from collections manager Amy Henrici, of course), so the next person to look at them can match them up with less faffing about.

We have people to thank. We had lunch almost every day at Sushi Fuku at 120 Oakland Avenue, just a couple of blocks down Forbes Avenue from the museum. We got to know the manager, Jeremy Gest, and his staff, who were unfailingly friendly and helpful, and who kept us running on top-notch food. So we kept going back. If you find yourself in Pittsburgh, check ’em out. Make time for a sandwich at Primanti Bros., too.

We owe a huge thanks to Calder Dudgeon, who took us up to the skylight catwalk to get the dorsal-view photos of the mounted skeletons (see this post), and especially to Dan Pickering, who moved pallets in collections using the forklift, and moved the lift around the mounted skeletons on Tuesday. Despite about a million ad hoc requests, he never lost patience with us, and in fact he found lots of little ways to help us get our observations and data faster and with less hassle.

Our biggest thanks go to collections manager Amy Henrici, who made the whole week just run smoothly for us. Whatever we needed, she’d find. If we needed something moved, or if we needed to get someplace, she’d figure out how to do it. She was always interested, always cheerful, always helpful. I usually can’t sustain that level of positivity for a whole day, much less a week. So thank you, Amy, sincerely. You have a world-class collection. We’re glad it’s in such good hands.

What’s next? We’ll be posting about stuff we saw and learned in the Carnegie Museum for a long time, probably. And we have manuscripts to get cranking on, some of which were already gestating and just needed the Carnegie visit to push to completion. As always, watch this space.


You’ll remember that we’ve been playing with CM 555, a subadult apatosaurine of indeterminate species, though John McIntosh assigned it to Brontosaurus (then Apatosaurus) excelsus. At the start of the week, we had the centra and neural arches of cervicals 1-14, plus there were some appendicular elements on a shelf that we’d not yet gone to. But then today, Matt found this drawer:

It contained a nice selection of cervical ribs that were part of the same specimen. Jackpot!

[You might notice that some of them have the specimen number 584 written on them. The history is that CM 555 and CM 584 came out of the same quarry, but most of the bones were initially thought to belong to a camarasaur which was designated CM 584. John McIntosh (1981:25) identified them as belonging to an apatosaurine, and they are now considered to be part of CM 555. The limb bones are catalogued separately as CM 556, but recognised as likely belonging to the same individual.]

Most of these ribs had field numbers written on them which were able to use to associate them with individual cervicals; and those that lacked these numbers, we could associate anyway, because the options were limited to a relatively small number of gaps. The upshot is that we know which vertebra each of these belongs to.

We have both ribs of C6, which is probably the best preserved single vertebra — centrum and arch — so I was able to rebuild the vertebra from its component parts. Matt was impressed:

And to be fair, I was pretty darned impressed myself:

Truly, this is a beautiful specimen. It was already pretty lovely, but putting the cervical ribs in place changed everything. It was totally transformed from a nice diplodocid cervical to an absolutely rock-solid slam-dunk apatosaurine — one to make grown men weep.

Here it is in right posterolateral view, just generally being awesome.


  • McIntosh, John S. 1981. Annotated catalogue of the dinosaurs (Reptilia, Archosauria) in the collections of Carnegie Museum of Natural History. Bulletin of the Carnegie Museum 18:1–67.