Supersaurus, Ultrasaurus and Dystylosaurus in 2019, part 1: what we know now

June 13, 2019

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



23 Responses to “Supersaurus, Ultrasaurus and Dystylosaurus in 2019, part 1: what we know now”

  1. David Lovelace Says:

    Hi Mike! I don’t really disagree with much you said – I look back at that paper and there are MANY things I wish I could do again to make it a little less ‘weak sauce’ – but alas, that was the result of undergraduate research with no real mentor. I was/am proud of what we did (with what we had/knew) – if nothing else it got some of the ‘Jimbo’ material out there – but it is nonetheless cringe-worthy looking back at it with a decade more experience ;) *but it still holds value* says my inner ego that can’t be silenced no matter how much I try.

    That being said, there were at least a few synapomorphies and an autapomorphic character that we stated (more/better would be… well… better). Plus there are a few other ‘apatosaurine-like’ characters that come from the Jimbo material, but alas those are appendicular.

    “Supersaurus dorsal vertebrae demonstrate several synapomorphic characters with Apatosaurus. The neural spines (measured from the junction between postzygapophyses to the top of the neural spine) of the posterior dorsal vertebrae make up more than half the height of the vertebra. This is similar to the condition seen in Apatosaurus. Both Diplodocus and Barosaurus exhibit posterior dorsal neural spine heights that contribute to less than half of the entire vertebrae (Fig.5). The bifed neural spines are lost prior to dorsal seven, and possibly as early as dorsal four or five (inferred from the merging of the spinoprezygapophyseal laminae with the prespinal lamina), unlike in Diplodocus. The cleft in the posterior dorsal neural spines of Diplodocusis absent in Supersaurus. Preserved dorsal centra of Supersaurus exhibit a ventral keel on the centra, as observed in Apatosaurus (UWGM 15556). While the posteriordorsal vertebrae of all other diplodocids are amphiplatean (GILMORE, 1936; HATCHER, 1901; LULL,1919), the posterior dorsals of both Supersaurus specimens are opisthocoelous, a probable autapomorphy of Supersaurus.”

    We also discuss the weird little paired pneumatocoels –

    “On the ventral surface just posterior of the centroparapophyseal lamina there are two pneumatopores separated by a medial septum. This feature appears in all cervicals where this area is preserved (both anterior and posterior cervical vertebrae demonstrate this condition). Figure 4 shows this condition in cervical vertebrae (Cv.) 14 of Apatosaurus ajax as well as in Cv.13 of Supersaurus; however this feature is absent in Barosaurus (LULL, 1919) and Diplodocus. More work is needed to determine the distribution of this character in diplodocids.”

    I would love to get your take on the above feature (it is an accurate observation, whether or not it has any utility has yet to be determined).

    I look forward to hearing your findings and hopefully a better resolution to the problem!
    All the best,

  2. william dale McInnes Says:

    WHAAAATTT ??? Give me a break! Curtice and Stadtman measured the BYU 5500 scapulocoracoid @ 2.44 m. (approx. 8′). This sounds about right. J. McIntosh himself measured this specimen. He was also very well aware of the 2nd specimen (unmeasured) and Jensen sent it to us at the PMRI (now RAM) in Alberta. P.J.Currie in the late 70s handed the specimen over to me for preparation. We were curious about why Jensen would create an 11′ field jacket for an 8′ = 2.44 m specimen. When G. Danis and I opened it up, we discovered a scapulocoracoid (BYU 5501) measuring 2.8 m = 9′ 2″. It gets complicated. When we prepared this giant bone from the matrix, we were able to close about 4″ of cracks. This brought it down to 2.7 m = 8′ 10″. The distal end of the bone was so thin, we could practically see through it. What was interesting was that we used mostly resin to cover an area we couldn’t cast. It was an area that had an ultra thin section that at best could only be described as a sharply defined delineation of the distal termination (literally powdered bone). We believed that this represented, possibly, an imprint of the cartilage. You should be able to see some of the powder we picked up in the original specimen. Mostly, the resined distal end is colorless and clear which could have been mistaken for “optimistic reconstruction”. We wondered about the 10″ that should but didn’t appear on the 2.44 m specimen (BYU 5500). We did take detailed photographs which never appeared in any publication that I am aware of. It was a transition time from Edmonton to Drumheller. Everything was in chaos at that time.

  3. Mike Taylor Says:

    Really interesting to hear from Dave and Dale! Thanks to you both.

    Dave, I hope I wasn’t overly harsh on your Supersaurus paper. Whatever criticisms I might have, it’s waaay better than my Archbishop paper! In other words, you got it done. Sure, there’s room for improvement: explaining the referral of the new specimen to Supersaurus would have been top of my list, and I suspect that you had figured this out and just didn’t get it down on paper. But the bottom line is that the specimen is described and out there to be shot at. That’s commendable. It cetainly does hold value!

    And yes, the paper does do a better job of justifying the apatosaurine position. But the relatively early disappearance of the interspinal cleft by D5 or so is shared by both Apatosaurus and Barosaurus, so it doesn’t help much. (In this respect, Diplodocus seems to be an outlier.)

    I agree that your paired-ventral-foramina character uniting Supersaurus with apatosaurines looks good: I certainly can’t see anything similar in my photos of the YPM Barosaurus material.

    BTW., is there any prospect of a followup paper on Jimbo?

  4. Mike Taylor Says:

    Dale, thanks for chipping in with your detailed memories of preparing the scapula! The Curtice and Stadtman (2002:39) passage I was alluding to says this:

    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 [i.e. what was previously known as BYU 5500] 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.

    But actually Curtice and Stadtman’s observation doesn’t make sense now I think it through, because in Jensen’s (1985:701) original description, BYU 5500 (the holotype) is the shorter of the two scaps at 2.44 m, with the referred scap BYU 5501 being longer at 2.7 m. So why would the repreparation of 5500, making it shorter than before, leave it more similar in size to 5501?

    At any rate, the “optimistic reconstruction” that I alluded to, being a reference to Curtice and Stadtman’s remarks quoted above, pertains to BYU 5500, not to the one that you worked on.

  5. TimW Says:

    Great summary of a complicated issue. Re the Supersaurus/Barosaurus synonymy…. I was unaware of this. Was the intention to sink Supersaurus vivianae into Barosaurus lentus, or to have S. vivianae as a distinct species of Barosaurus (B. vivianae)?

  6. Mickey Mortimer Says:

    ““‘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?)”

    The very paper you show Ultrasauros’ entry from (Olshevsky, 1991) has “Ultrasaurus” going back to 1978, “Supersaurus” to 1972 and no leak of Dystylosaurus prior to its official publication. The “Ultrasaurus” publication is-

    Jensen, 1978. Ultrasaurus. Science News. 116, 84.

    Not sure what the original “Supersaurus” entry is though. Try emailing Olshevsky.

  7. Nick Pharris Says:


    Huh. I always thought one of the diplodocids (the less heavily marked one on the left, I think) was supposed to be Seismosaurus (=Diplodocus hallorum).

  8. Mike Taylor Says:

    Thanks, TimW! Rather than try to summarise Curtice’s slightly ambiguous abstract, I’ll just post it here. (I got his, in plain text, from Jerry Harris, who got it directly from Brian Curtice.)

    The Dry Mesa Dinosaur Quarry near Delta, Colorado has produced the most diverse group of dinosaur taxa ever found in one location. Four theropod genera, three ornithischian genera and at least seven sauropod genera are recognized from the quarry. The quarry is traditionally know[n] for two additional sauropods, Ultrasaurus and Dystylosaurus. Recent synonomy of Dystylosaurus and Ultrasauros with Supersaurus not only reduced the genera count but, by realizing the three taxa represent one individual diplodocid, provided a more accurate size profile and phylogenetic positioning of Supersaurus. 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.

    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.

  9. Mike Taylor Says:

    Mickey, it simply hadn’t occurred to me to use the Olshevsky revision as a source of taxonomic history, but of course that’s exactly what it’s for! Thanks for the hint. Also, good catch on Jensen’s 1985 paper being the first revelation of the name Dystylosaurus. That’s a real shock to me. I’d have sworn I was aware of the trio, as a trio, much earlier than that.

    I’d got as far as locating the Science News announcement of Ultrasaurus, but ran into a paywall that Sci-Hub could not defeat at (which is an oddly specific URL). BTW, this seems to be from 1979, not 1978.

  10. Mike Taylor Says:

    Nick, you may be right about the identities of the three sauropods in Sibbick’s piece: what is your source?

  11. Mike Taylor Says:

    Well, it turns out that Science News is a registration-impeded website, not a subscription journal. So I was able to make a free account and get the (very short) account of Ultrasaurus — which is indeed from 1979, not 1978. That leaves me worried that Olshevsky might have found an older mention that we’ve both missed … or of course he might just have mistyped the year.

    Regarding Dystylosaurus, this other Science News piece, from 1986, says “In recent years, scientists have unearthed the remains of Supersaurus and Ultrasaurus, animals weighing in at about 75 or 80 tons and measuring about 90 to 100 feet long.” But poor Dystylosaurus doesn’t get a mention. So even though it had been formally published by then (Jensen 1985), it doesn’t seem to have been something that journalists were aware of.

  12. Mike Taylor Says:

    … and this piece from 1987 surprisingly says “Although they have created the genus name Ultrasaurus, scientists are still unsure whether the animal they are studying belongs in a genus of its own or was just a large Brachiosaurus.” Would the BYU people really have been asking this two years after the genus was created?

    This makes me wonder whether Science News might be mis-dating articles in its own archive. (Or just very behind the times!)

    Corroborating that hypothesis: the same piece goes on to say: “This month, though, Brigham Young scientists unearthed a 4-foot-long neck vertebra that they think might finally settle the genus question”. This must surely be a reference to BYU 9024 — but that vertebra was found, excavated, photographed, modelled in plaster and published by 1985. Something is weird here.

  13. David Marjanović Says:

    I, too, was sure one of Sibbick’s trio was supposed to be Seismosaurus. I’ll have to find the book again…

    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 specimen

    To the holotype individual. Having a separate specimen number, it remains a separate specimen. Most of the Code fails to distinguish specimens from individuals, but Art. 72.5.5 and 73.1.5, as well as the slip-up in the wording of Rec. 72C, reveal the secret.

  14. David Marjanović Says:

    Uh, Article 72 of the International Code of Zoological Nomenclature. Art. 73 can be accessed in the sidebar.

  15. Mike Taylor Says:

    Thanks, David, for the precision on the distinction between the type specimen and the type individual. I will revise the text of this post accordingly.

    Does anyone have a way of getting in touch with Sibbick, to get the definitive take on what the three big sauropods in his artwork are?

  16. Matt Wedel Says:

    Regarding ventral pneumatic foramina in sauropod cervicals…

    In general pneumatic traces on the ventral surfaces of sauropod cervicals are woefully underdescribed, and I don’t know of any comprehensive review. I wasn’t thinking about them when I wrote Wedel (2003), and I haven’t been back to that sort of alpha-level descriptive work for cervicals in a while. I’ve seen pneumatic foramina on the ventral centrum firsthand in apatosaurines and brachiosaurids, but lots of other sauropods have fossae in the same position. Interestingly, sometimes there is a single midline fossa, and sometimes paired fossae split by a midline ridge or keel — the latter morphology is present in Barosaurus (see this post) and Haplocanthosaurus (visible in a CT slice in this post) and probably lots of other sauropods.

    I know that Tschopp et al. (2015) coded ventral pneumatic features for the taxa in their big diplodocoid analysis, but I haven’t dipped into that lately to see what they found. I strongly suspect that the pneumatic foramina are both highly variable serially and among individuals, and subject to a lot of homoplasy, simply by virtue of being pneumatic. Anyway, that paper would be the place to start.

  17. Mike Taylor Says:

    Matt, the Barosaurus cervical in the post you link has the ventral midline ridge, but I’m not seeing foramina either side of it.

  18. Matt Wedel Says:

    Oh, and regarding Sibbick’s trio of giant sauropods, the earliest appearance I know of is on pages 164-165 of David Norman’s 1994 book Prehistoric Life: The Rise of the Vertebrates. The caption reads:

    In recent years there has been a spate of reports from North America of “the biggest ever dinosaur”. On the left is Seismosaurus, up to 120ft (36m) long and weighing some 50 US tons (tonnes). Ultrasaurus (center) was a Brachiosaurus-like creature, and Supersaurus (right) resembled Diplodocus.

    Are there any earlier versions, possibly with different IDs for the critters?

  19. Mike Taylor Says:

    Thanks, Matt, that’s a really useful ID for the Sibbick artwork. I will tweak the caption accordingly.

  20. Matt Wedel Says:

    Matt, the Barosaurus cervical in the post you link has the ventral midline ridge, but I’m not seeing foramina either side of it.

    Right, I didn’t claim that there were. All I was saying is that there are fossae split by a midline ridge. There might be a figure/ground problem here in that the fossae aren’t usually distinct or sharp-edged, and one could argue whether there are fossae at all if the midline ridge is an additive structure. Or, alternatively, the ridge only appears because the bone on either side has been resorbed. (And incidentally, the same linked post shows a midline ridge in Diplodocus, which I forgot to mention in my previous comment.)

    The larger point, which I didn’t explain well (or at all) in the previous comment, is that fossae and foramina are on the same spectrum. If ventral centrum pneumaticity follows the same rules as pneumaticity in the rest of the vertebra, fossae are evolutionarily and developmentally antecedent to foramina. To me, presence or absence of a pneumatic space at all is a more important distinction than whether that space is a fossa or a foramen; the former indicates whether pneumaticity was present or not, whereas the latter just tells us how much.

  21. […] 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. […]

  22. […] 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 […]

  23. […] a comment on the first post in this series, Dale McInnes took issue with aspects of Curtice and Stadtman’s account of the repreparation […]

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