This is a Galeamopus, roughly two feet long, sculpted by James Herrmann (who also made the life-size Aquilops sculpture and bust) for the Cincinnati Museum Center.

Here’s what it looks like on the other side.

From behind.

And from the front.

I dig this. I’m sure someone else must have done this half-skeletal reconstruction, half-fleshed life restoration style of sculpture before, but I can’t think of any museum-quality examples. The bronze is a nice touch.

Here’s a convincingly chunky Allosaurus.

About the sculpting process, James wrote (in an email with permission to cite):

I worked on all of the museum pieces with Glenn Storrs, Ph.D., vertebrate paleontologist with the Cincinnati Museum Center. He would tell me what he envisioned and provide me with reference material, I would sculpt it, take the clay to Glenn for his critique, take it back and make revisions. We went through several cycles of this for each piece and when I received the final approval I took each piece to the foundry.

Tyrannosaurs are to museums what roller-coasters are to amusement parks. Here’s Daspletosaurus.

My favorite thing about these sculptures is why they’re done in bronze. It’s not just for posterity. James again:

The idea was to provide a small sculpture of each skeletal reconstruction on display for people to touch and feel. It was felt that this element of touch would be particularly important to accommodate the needs of the visually impaired museum visitor. I will feel like I have achieved success when the patina is rubbed off parts of the bronze.

One more, a life-size bust of Galeamopus.

In addition to having these on display at the Cincinnati Museum Center, James will be producing these sculptures as limited editions. If you’re interested, please visit http://www.herrmannstudio.com/.

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Since the previous installment of this epic, we’ve taken two brief digressions on how little importance we should attach the colours of bones in our photographs when trying to determine whether they’re from the same individual: cameras do lie, and in any case different bones of the same individual can age differently. Since then — newsflash! — a third reason has become apparent in the case of the two Supersaurus scaps: the object we discussed as Scap A turns out to be a cast. A really good one, sure, but still: its colour tells us little about the colour of the actual bone.

If you doubt that, consider the scapulocoracoid referred to Ultrasauros (which we’ll be meeting again in the next post). Here is the real bone, at the North American Museum of Ancient Life (NAMAL), with me for scale:

BYU 9462, the scapulocoracoid referred by Jensen to Ultrasauros. Mike Taylor for scale, doing a Jensen. The signage reads: Brachiosaurus scapula and coracoid. Originally believed to belong to the genus Ultrasaurus (now invalid), this shoulder blade is from the giant herbivorous dinosaur Brachiosaurus, a replica of which is mounted in this room. The dinosaur that owned this scapula was over 65 feet long and could tower 45 feet above the ground. When collected by Jim Jensen at Dry Mesa Quarry (Colorado) in 1989, the scapula was believed to represent the largest dinosaur ever found. Note how many separate pieces are within the specimen. A tremendous amount of work is required to complete a fossil of this size. Specimen on loan from Brigham Young University’s Earth Science Museum. Late Jurassic/Early Cretaceous (about 144 million years ago)

And here’s Matt with the cast of the same bone that resides in the BYU collections:

As you can see, the cast has been prepared in a darker and browner colour than the pale greenish grey of the real bone (though don’t forget that cameras lie about colours, so we shouldn’t over-interpret this difference).

Aaanyway …

We finished up last time with the observation that the holotype scapulocoracoid of Supersaurus, BYU 9025, is not obviously diagnostic; and that since the cervical BYU 9024 that has been referred to it actually belongs to Barosaurus, we can’t trust any of the other referrals of big Dry Mesa diplodocid bones to Supersaurus; and that the name must therefore be considered a nomen dubium, resting as it does on non-diagnostic material.

Can the name Supersaurus survive? I think it can, and I see four possible routes to that happening.

Method 0: Everyone ignores these blog posts

This is only a blog, after all. No-one is obliged to pay any attention to anything we say here.

That said, Matt and I do have previous in transforming series of blog posts in to actual papers. Having invested so much effort into writing these posts, I do hope that I’ll be able to do the same thing in this case, so at some stage the ideas from this series should become part of the formal scientific record. (I make no promises about how long that will take.)

So assuming that we can’t all just walk away and pretend that none of this ever happened, are there better ways to save the name Supersaurus?

Method 1. Someone finds autapomophies

Matt and I are of course primarily vertebra jockies. We are not above studying the occasional taxon based on appendicular material, but our expertise lies in the domain of the axial. It’s perfectly possible that someone who understands sauropod appendicular anatomy better than we do could isolate some autapomorphies in the holotype scap BYU 9025, and Supersaurus would then be firmly founded on a diagnostic type specimen.

Can we find hope for this outcome in the results of phylogenetic analyses?

In Whitlock’s (2011) diplodocoid analysis, Supersaurus emerges with but a single autapomophy: “Anterior caudal neural spine height less than 150% centrum height” (page 44). Based, as it is, on a referred element, that doesn’t help us much here. (Although it’s worth noting that Whitlock scored this character as 0 for Supersaurus and 1 for Barosaurus, which does very slightly suggest that the referred caudal is not Barosaurus and therefore might belong to the same individual as the Supersaurus holotype. Yes, this is weak sauce.)

Tschopp et al.’s (2015) unnumbered supplementary file Apomorphies recovered by TNT under implied weighting is difficult to interpret: for example, a heading on the first page says simply “R_iw” and its counterpart on page 8 is simply “P_iw“. But the Supersaurus-relevant entries are the same under both headings. In both cases, they read:

Supersaurus vivianae BYU
Char. 258: 1 –> 0
Char. 274: 1 –> 0
WDC DMJ-021
Char. 165: 1 –> 2
Char. 172: 0 –> 1
Char. 174: 0 –> 1
Char. 257: 1 –> 2

Node 137 (Supersaurus vivianae)
Char. 183: 1 –> 2

I read this as meaning that the two OTUs have autapomorphies as listed, and the node uniting them has a single synapomorphy. But all of these characters related to the presacral vertebrae (C165-C183 in the cervicals, C257-C274 in the dorsals). So again, there is nothing here to help us diagnose Supersaurus on the basis of the holotype scapulocoracoid.

Of course, that doesn’t prove that there there aren’t any diagnostic characters. Someone with a good eye for sauropod scapulocoracoids might find details missed by these phylogenetic analyses, whose remits were much broader. But the news so far is not good.

Method 2. Nominate a neotype from the BYU material

If we accept that there are probably no more than two big diplodocoids in the Dry Mesa quarry, and that one of them is Barosaurus (based in the big cervical BYU 9024), and that the “Dystylosaurus” vertebra BYU 4503 is not Barosaurus, then it must follow that it belongs to Supersaurus. Unlike the type scapulocoracoid BYU 9025, that vertebra probably is diagnostic (it’s an anterior diplodocid dorsal, yet its spine is unsplit) so perhaps Supersaurus could survive by being diagnosed on that basis.

How would this work nomenclaturally? I think it would be difficult. If I have properly understood Article 75 of the ICZN, you can only go ahead and designate a neotype “when no name-bearing type specimen (i.e. holotype, lectotype, syntype or prior neotype) is believed to be extant”. But the holotype scapulocoracoid exists (so far as we know, though we’re not sure where it is).

All is not necessarily lost, though. Paragraph 75.5 (Replacement of unidentifiable name-bearing type by a neotype) says “When an author considers that the taxonomic identity of a nominal species-group taxon cannot be determined from its existing name-bearing type (i.e. its name is a nomen dubium), and stability or universality are threatened thereby, the author may request the Commission to set aside under its plenary power [Art. 81] the existing name-bearing type and designate a neotype.” But that means writing an ICZN petition, and I’m not sure anyone wants to do that. The process is technical, picky and prolonged, and its outcome is subject to the whim of the committee. It’s quite possible someone might go to all the trouble of writing a petition, then wait five years, only to have it rejected.

The irony here is that when Curtice and Stadtman (2001) referred the “Dystylosaurus” dorsal BYU 4503 to Supersaurus, they were at liberty to sink Supersaurus into Dystylosaurus rather than vice versa. Then the unique dorsal vertebra would have become the holotype, and the surviving genus would have been nicely diagnosable. Curtice and Stadtman (2001) did not discuss this possibility; nor did Curtice et al. (1996) discuss the possibility of folding Supersaurus into Ultrasauros when determining that the holotype vertebra of the latter belongs to the same taxon as the former.

Curtice and his collaborators were likely following the principle of “page priority”: preferring Supersaurus over the other two genera as it was the first one named in Jensen’s (1985) article that named all three. However, page priority does not exist at all in the present version of the Code (see Article 24, Precedence between simultaneously published names, spellings or acts), and even in earlier versions was only a non-binding recommendation. So it was really Curtice’s and his friends’ choice which genus to retain.

But that ship has now sailed. According to the principle of first reviser (Section 24.2.1), the pubished actions of Curtice and colleagues established a new status quo, and their choice of genus stands.

Method 3. Nominate Jimbo as a neotype

We might conceivably give up on the mixed-up Dry Mesa material as too uncertain to base anything on, and nominate WDC DM-021 (“Jimbo”) as the neotype specimen instead. It may have less material in total than has been referred to Supersaurus from the Dry Mesa quarry, but the association is somewhat more solid (Lovelace et al. 2008:528).

In some ways this might be the most satisfactory conclusion: it would give us a more solid basis on which to judge whether or not subsequent specimens can be said to belong to Supersaurus. But as with method 2, it could only be done via a petition to the ICZN, and I suspect the chances of such a petition succeeding would be low because clause 75.3.6 of the Code says that neotype designation should include “evidence that the neotype came as nearly as practicable from the original type locality [of] the original name-bearing type”.

So I don’t think this is likely to work, but I mention it for completeness. (Also, I am not 100% sure how solid the association of the Jimbo elements is, as the wording in Lovelace et al. (2008:528) does hedge a little.)

In conclusion …

I think the best hope for the survival of the name Supersaurus would be the recognition of unambiguously diagnostic characters in the holotype scapulocoracoid BYU 9025. In comments on the last post, John D’Angelo has started to think about what characters might work here. We’ll see how that thread pans out.

On the other hand, do we even particularly want the name Supersaurus to survive? It’s a pretty dumb name. Maybe we should just let it die peacefully.

Next time — in what really, really, really will be the last post in this series — we’ll consider what all this means for the other two names in Jensen’s trio, Dystylosaurus and Ultrasauros.

References

  • 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.
  • 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.
  • 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
  • Whitlock, John A. 2011. A phylogenetic analysis of Diplodocoidea (Saurischia: Sauropoda). Zoological Journal of the Linnean Society 161(4):872-915. doi:10.1111/j.1096-3642.2010.00665.x

 

When I started this series, it wasn’t going to be a series at all. I thought it was going to be a single post, hence the title that refers to all three of Jensen’s 1985 sauropods even though most of the posts so far have been only about Supersaurus. The tale seems to have grown in the telling. But we really are getting towards the end now. This should be the last post that is only about Supersaurus, and then we should be able to finish with one more that covers all three animals.

Supersaurus skeletal reconstruction at NAMAL, based in part on preserved fossil material. Mike Taylor for scale, lying in front of the referred scapulocoracoid BYU 12962.

So: what actually is Supersaurus?

Is Supersaurus the same thing as Barosaurus?

As we established previously, a lot of material has been referred not only to Supersaurus in general, but to the type individual in particular: a cervical, two dorsals, four sacrals, 20 caudals, two scapulocoracoids, an ulna, a carpal, right ilium and pubis, both ischia, and a phalanx. (After Jensen’s original papers, Curtice and his collaborators did much of the work to assemble this list.) And remember, too, that Lovelace et al. (2008) described a completely separate Supersaurus specimen from Wyoming.

So: 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 Supersaurus type individual, and our conception of Supersaurus needs to change accordingly; or it was correctly referred, which means that Supersaurus is merely a very big Barosaurus, and the name should be sunk.

I would be a lot more confident about which of these is the right thing to do if Matt and I had had time to look at all the sacral, caudal and appendicular material of Supersaurus during the Sauropocalypse. But our time was very limited (seven museums in nine days) and we had to focus on the presacrals.

What we really want is a solid assessment of all the putative Supersaurus material and a judgement of whether the differences between it and regular Barosaurus might be size- or age-related. We can’t have that (at least, not unless someone with more time on their hands than Matt or me takes it on).

But we are not left without hope. We have the published literature.

Pylogenetic analyses

Lovelace et al. (2008:figure 14). Strict consensus tree resulting from the addition of Supersaurus and “Seismosaurus” into a modified matrix from Harris & Dodson (2004).

First, Lovelace et. al’s (2008) description of Jimbo, the WDC’s referred Supersaurus specimen, included a phylogenetic analysis. This recovered Supersaurus as the sister taxon to Apatosaurus, with Suuwassea as its outgroup, and the BarosaurusDiplodocus clade sister to that broader grouping. That finding would argue against Supersaurus being Barosaurus. (They commented that “It is possible that some similarities between Supersaurus and other apatosaurines result from a size-coupled increase in robustness, but it is worth noting that apatosaurine robustness does not correlate with size, and large diplodocines like Seismosaurus do not exhibit markedly more robust pelvic or costal elements.)

Whitlock (2011:figure 7). Phylogenetic hypothesis presented in this analysis. Cladogram represents a strict consensus of three equally parsimonious trees (273 steps), labelled with relevant clade names. Decay indices reported below each node.

Whitlock’s (2011) more detailed phylogenetic analysis recovered Supersaurus is a somewhat more traditional position, closer to Barosaurus than to Apatosaurus. But still not very close. Supersaurus is here the most basal diplodocine, the outgroup to Dinheirosaurus, Torneria and the Barosaurus+Diplodocus pair. It’s not a result that would immediately make you want to synonymise Supersaurus with Barosaurus.

One problem with both Lovelace et al.’s and Whitlock’s analyses is that they took as read that the WDC specimen really is Supersaurus — the same thing as the BYU specimen. What if it isn’t? Maybe the WDC animal is something different that’s more closely related to Apatosaurus, while the BYU specimen is a big Barosaurus? Is that possible?

Enter Tschopp et al. (2015), whose monumental specimen-level analysis separated Jimbo out from BYU Supersaurus — and so they tested the hypothesis that these two specimens are the same thing, instead of assuming it. Here’s what they found:

Tschopp et al. (2015:figure 118). Reduced consensus tree obtained by implied weighting. Eight OTUs were deleted a posteriori. Numbers at the nodes indicate the number of changes between the two branches departing from the node (for the apomorphy count), where they differ from the trees under equal weights.

As you can see, BYU Supersaurus and the WDC specimen came out as sister taxa in every most parsimonious tree. And Tschopp et al.’s (2015) figure 115 shows that this is true under equal-weights parsimony as well as under implied weighting. So this gives us confidence that the WDC team’s referral of Jimbo to Supersaurus probably is correct after all.

But that Supersaurus duo comes out some way away from Barosaurus, being well outside the DiplodocusBarosaurus node.

These are the only three phylogenetic analyses I am aware of to have included Supersaurus — though if there are others, please shout in the comments. In none of them do Supersaurus and Barosaurus come out as sister taxa, and in fact they are separated by multiple nodes in all three analyses.

More compellingly, Andrea Cau re-ran Tschopp et al.’s (2015) analysis with Supersaurus and Barosaurus constrained to be sister groups (thanks, Andrea!) and found that the best resulting trees were 18 steps longer than the unenforced trees (1994 steps vs 1976). This is convincing evidence that the totality of the Supersaurus material is not Barosaurus.

Is BYU Supersaurus a chimaera?

All of this strongly suggests — it comes close to conclusively proving — that Supersaurus (as defined by all the BYU and WDC material) is not Barosaurus. But if Matt and I are right that BYU 9024 is a vertebra of Barosaurus, then it follows that this cervical doesn’t belong to Supersaurus.

And that, I think, throws the whole material list of BYU Supersaurus into question. Because if the big cervical belongs to something different, then it follows that there are (at least) two big diplodocids mixed up in the Dry Mesa quarry, contra Curtice et al.’s (2001) assertion that all the big bones there can be referred to two individuals, one diplodocid and one brachiosaur.

In which case, how can we know which of the elements belongs to which of the animals?

Are the scapulocoracoids from the same individual?

Can we even trust the assumption that the two scapulocoracoids were from the same animal? Maybe not. In favour of that possibility, the two elements are similar sizes, and were found close together. But there are reasons to be sceptical.

Based on our photos in the earlier post, I was coming to the conclusion that Scap B is much less sculpted than Scap A. But I started to change my mind once I was able to make a weak anaglyph of Scap B. Now, thanks to Heinrich Mallison and the magic of photogrammetry, my set of bad photos have become a 3D model, which is far more informative again.

Here, then, is a comparative anaglyph of the two scapulocoracoids.

Red-cyan anaglyps of both scapulocoracoids of Supersaurus from BYU’s Dry Mesa Quarry, Utah. Top: the holotype BYU 9025, left scapulocoracoid (“Scap A”); Bottom: referred specimen BYU 12962, right scapulocoracoid (“Scap B”), reversed for easier comparison. Scap B rendered from a 3D model created by Heinrich Mallison. Scaled to the same length. (We could not scale them in correct proportion, since the true current lengths of both are unknown.)

These are not obviously from the same individual, or from the same species, or even necessarily the same “subfamily”. A few of the more obvious morphological differences:

  • In Scap A, the acromion process projects posterodorsosally, whereas in Scap B it projects dorsally (i.e. at right angles to the long axis of the scap.)
  • In Scap A, the acromion process is positioned close to mid-length of the whole element, whereas in Scap B it is closer to the proximal end.
  • In Scap A, the acromion process comes to a point, whereas in Scap B is it lobe-shaped.
  • In Scap A, the ridge running running up to the acromion process is broad and becomes rugose dorsally, whereas in Scap B it is narrow and remains smooth along its whole length.
  • Scap B has a distinct ventral bump around midlength, which Scap A lacks (or at most has in a much reduced form).
  • In Scap B, the ventral border below the acromion process distinctly curves down to the glenoid, but in Scap B this ventral margin is almost straight.
  • In Scap A, the glenoid margin is gently curved, nearly straight, whereas in Scap B it has a well defined “corner”, with distinct scapular and coracoid contributions that are at right angles to each other.
  • In Scap A, the dorsal margin of the coracoid is well defined and has a low laterally protruding ridge. This is absent in Scap B, where the coracoid’s dorsal margin is poorly defined.

Now, much of this is quite possibly due to damage — as (I assume) is the excavation in the dorsal margin of the distal part of the scapular blade in Scap A. But when you put it all together, I think they really are rather different, even allowing for variation in limb-girdle bones. Certainly if you found them both in different quarries, you would not leap to the conclusion that they belong to the same species. Jensen’s (1985:701) description of Scap B (BYU 5001 of his usage) as “same as Holotype, BYU 5500” is difficult to justify.

The possibility that the two scaps are from different individuals is also weakly supported by the fact that the preservation looks very different between the two elements — dark and rough for Scap A but light and smooth for Scap B. But I don’t trust that line of evidence as much as I might for two reasons. First, different photography conditions can give strikingly different coloured casts to photos, making similar bones appear different. And second, I know from experience that bones from a single specimen can vary in colour and preservation much more than you’d expect.

At any rate, I certainly don’t think it’s a given that the two scapulae belonged to to the same individual as Curtice and Stadtman (2001) stated. And of course if they do not, then the issue of which is the holotype takes on greater importance — which is why we spent so long on figuring that out.

So what are we left with?

We know — or at least we are confident — that one of the referred BYU Supersaurus elements is Barosaurus. We don’t think the whole animal is Barosaurus, due to the evidence of three phylogenetic analyses. So we think there are at least two big diplodocoids in the BYU quarry, and we can’t know which of the elements belongs to which animal. We can’t even be confident that the two scapulocoracoids belong to the same animal.

As a result, the only bone that we can confidently state belongs to Supersaurus is the holotype — BYU 9025, which we called “Scap A”. All bets are off regarding all the other Dry Mesa diplodocoid elements. They might belong the Scap A taxon, or to Barosaurus. (Or indeed to something else, but we’ll ignore that possibility as multiplying entities without necessity.)

So to the next question: is the holotype element even diagnostic, beyond the level of “big diplodocoid”? I’m not sure it is, but this is where I’d welcome input from people who are more familiar with sauropod appendicular material than I am. At any rate, Jensen’s (1985:701) original diagnosis based on the holotype scap is useless: “Scapula long but not robust; distal end expanding moderately; shaft not severely constricted in midsection”.

The emended diagnosis of Lovelace et al. (2008:530) says of the scapulocoracoid only “scapular blade expanded dorsally; deltoid ridge perpendicular to the acromian[sic] ridge”. but they also include a more comprehensive assessment of the BYU scapulae (p. 534) as follows:

The only known pectoral elements for Supersaurus are the scapulocoracoids from Dry Mesa (Fig.10). Scapulocoracoid BYU 9025 demonstrates a deltoid ridge that is perpendicular to the acromian ridge and the scapular blade is one-half the entire length of the scapulocoracoid. Both of these features are seen in Apatosaurus but not in Diplodocus or Barosaurus, which have relatively short scapular blades, and an acute angle between the deltoid ridge and the acromian ridge. This angle is much stronger in Barosaurus than it is in Diplodocus. The apatosaurine nature of the scapulocoracoids further reinforces the referral of BYU elements to the type scapula, as well as our referral of WDC DMJ-021 to Supersaurus.

This is a helpful discussion (although note that Lovelace et al. are not consistent about which of the scaps they think is BYU 9025). But, notably, nothing here suggests any unique characters of the scapulocoracoid that could serve to diagnose Supersaurus by its holotype.

Putting it all together, it seems that BYU 9025 is the only bone in the world that unambiguously belongs to Supersaurus (because it is the the holotype, and all referrals are uncertain); and that bone is non-diagnostic. I think it must follow, then, that Supersaurus is currently a nomen dubium.

I say “currently”, because there are at least three possible ways for the name to survive. (Four, if you count everyone just ignoring this sequence of blog-posts.) Next time, we’ll talk about those options.

 

References

  • 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.
  • Harris, Jerald D., and Peter Dodson. 2004. A new diplodocoid sauropod dinosaur from the Upper Jurassic Morrison Formation of Montana, USA. Acta Palaeontologica Polonica 49:197–210.
  • Jensen, James A. 1985. Three new sauropod dinosaurs from the Upper Jurassic of Colorado. Great Basin Naturalist 45(4):697–709.
  • 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.
  • 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
  • Whitlock, John A. 2011. A phylogenetic analysis of Diplodocoidea (Saurischia: Sauropoda). Zoological Journal of the Linnean Society 161(4):872-915. doi:10.1111/j.1096-3642.2010.00665.x

 

Before we get on to the home stretch of this series — which is turning out waaay longer than I expected it to be, and which I guess should really have been a paper instead — we need to resolve an important detail. We all know there are two scapulocoracoids in the BYU Supersaurus material, and that one of them is the holotype: but which one?

The two elements

Since we don’t know the actual specimen numbers yet, we’ll refer to the two specimens as Scap A and Scap B for now.

Both specimens are on loan from BYU to other museums. We’re not sure where Scap A is, but there is a good cast at the Dinosaur Journey Paleontological Museum in Fruita, Colorado; and Scap B is at the North American Museum of Ancient Life (NAMAL) in Lehi, Utah. Happily, we saw both on the Sauropopcalypse. Unhappily, we were in a rush both times, and didn’t pay them anything like the attention they deserve.

Scap A

We don’t have many photos of this, because we only had a single day at Dinosaur Journey museum and we had a lot of specimens we wanted to hit in collections. But it’s still shameful that we have as little as we do. Here’s one from Matt’s earlier visit in 2014:

Cast of one of the scapulocoracoids of Supersaurus, which we here refer to as Scap A, at the Dinosaur Journey musuem in Fruita, Colorado. Matt Wedel for scale.

And here is an anaglyph made from the only two photos I took on our 2016 Sauropocalypse visit:

Sort-of-OK anaglyph of the cast of the Supersaurus scapulocoracoid A. It’s not great because we don’t have a good pair of source photos, but it’s still way more informative than a 2d photograph.

If you think our images are disappointing, check out Jensen’s own illustrations of this specimen. It crops up in line-drawing form as part B of figure 8 in his 1985 paper:

Jensen 1985:figure 8B and G. For comparison only, not to scale. Profiles of various sauropod scapulae and scapulocoracoidae. B, Supersaurus vivianae, first specimen. G, Supersaurus vivianae, second specimen. (Other, non-Supersaurus, parts removed.)

And that seems to be all we have of this specimen.

Well … almost all. There is just one other photo …

I really really wish I’d spent less time making out with this specimen and more time studying it. There’s a lesson there for all of us, kids!

This scap has really nice, clear ridges running along the ventral border of the proximal end, and up from there to the acromion process. That makes it very clear that we’re looking at the lateral side of the scap, which means it’s a left scapulocoracoid.

By the way, I am a little short of six feet tall. Using myself as a very crude scalebar, it looks like this scap is a hair over eight feet long. (Why am I using Imperial measurements? Because, as will become clear below, that’s what Jensen used, and so what we want to compare with.)

Scap B

This occurs in Jensen’s (1985:figure 8G) line drawing, as shown above. But there are a few more photos out there. For a start, this is the scap which Jensen is measuring and then lying next to in the photos in his descriptive paper:

Jensen 1985:figure 6. A, Measuring Supersaurus vivinae scapulocoracoid. D. E., Vivian Jones; J. A. Jensen. B, The author, 6’3″ tall beside Supersaurus vivianae scapulocoracoid.

This is evidently the scap that we photographed at NAMAL, although it’s been flipped since the photos were taken of it in the ground:

Supersaurus vivianae scapulocoracoid, 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)

A similar photo turns up in Lovelace et al.’s (2008) description of the WDC Supersarus specimen, where a specimen number is given. This is welcome, as neither museum display includes a specimen number, and none of the Jensen’s illustrations do, either. It’s the first specimen number we’ve seen in this post.

Lovelace et al. 2008:figure 10. Lateral view of Supersaurus right scapulacoracoid (BYU 9025).

Also, Lovelace et al. (2008) provided a scalebar. If it’s reliable — which is always open to question with scalebars — the scapulocoracoid is 2.34 m long (based on 687 pixels for the scap, 147 for the scalebar), which is about 7’8″.

I don’t know where Lovelace et al. got the specimen number for this element: it’s certainly not on display in the NAMAL public gallery. Elsewhere, Lovelace et al. (2008:527) say that “The name Supersaurus was erected for a single scapulocoracoid, BYU 12962″, contradicting Jensen’s designation of BYU 5500 (i.e. BYU 9025) as the holotype.

Is this in fact a right scapulocoracoid, as claimed? I did wonder, because based on my own photos and the Lovelace et al. illustration the surface we’re looking at is pretty flat and featureless, which would suggest it’s the medial side of the bone. If that were so, it would be a left scap viewed from inside, not a right scap viewed from outside. But I was able to recover a very rough-and-ready anagylph from my NAMAL photos, and that was enough to persuade me that there is some surface structure on this bone, and that we are indeed therefore looking at the lateral face of a right scap.

(If you can’t make out the 3d structure here, it’s because you don’t have any red-cyan anaglyph glasses. Get some red-cyan anaglyph glasses. You’ll thank me.)

Anyway: I am satisfied that Scap A is a left scapulocoracoid and Scap B is right scapulocoracoid. So that’s something.

Which is the holotype?

This should be a simple question to resolve. But it’s not, for several reasons. First, although the earliest literature on Supersaurus refers to the scapulocoracoids, it doesn’t give specimen numbers. Second, Jensen’s (1985) description is vague about specimen numbers, sometimes using them and sometimes just referring to “first specimen” and “second specimen”. Third, the specimen numbers that Jensen used have since been changed. Fourth, the subsequent literature contains contradictions and perhaps straight-up mistakes. And finally, as though all that were not enough — and as we’ve already noted — the two museums that have the actual bones on display have omitted specimen numbers from their signage.

Yeah. It’s pretty crazy stuff. Let’s see if we can sort it out.

That Reader’s Digest article

The earliest reference to the name “Supersaurus” we’ve been able to find in the literature is George 1973a, which was subsequently condensed into George 1973b in Reader’s Digest. (These both predate George 1973c, cited by Curtice and Stadtman 2001, which I have been unable to obtain a copy of, if indeed it is actually a real article, as it does not seem to be.)

Aaanyway, here’s what George (1973b) says about “Supersaurus” scapulae. It doesn’t amount to much.

A shoulder blade, still partially encased in clay, spanned eight feet. Breaks and cracks were sealed with a mixture of sand and plaster, the bones were wrapped in burlap soaked with plaster of paris, braced, then swung aboard a special trailer for the journey to B.Y.U. in Provo, Utah. There, “Supersaurus,” as we shall call him, awaits an official name and taxonomic classification.

This certainly sounds like the eight-foot-long scap was destined to be the type specmen, but it doesn’t come out and say it.

Jensen 1985

As far as I know, the next published reference to this material is eight full years later, in Jensen’s (1985) formal description. It needs careful reading. But what seems clear (from page 701) is:

HOLOTYPE.—BYU 5500, scapulocoracoid 2.44m (8′) long.

REFERRED MATERIAL.—BYU 5501, scapulocoracoid 2.70 m (8′ 10″) long. [And other material not of interest for our purposes.]

[… and a little later …]

DESCRIPTION.—(Holotype BYU 5500; right scapulocoracoid) Scapula long but not robust; distal end expanding moderately; shaft not severely constricted in midsection. [There is more, but it’s not relevant here]

REFERRED MATERIAL.—BYU 5501, scapulocoracoid 2.70 m (8′ 10″) long. Description same as Holotype, BYU 5500.

So based on this, the “description” of the two scaps is the same, and the only recognised difference is in length: the holotype, at eight feet in length, is ten inches shorter than the referred element.

On that basis, Scap B might seem the more likely contender to be the holotype, as the scalebar in Lovelace et al. 2008:figure 10 suggests a length of 2.33 m which is closer to the 2.44 m given for the type than to the 2.7 m given for the referred specimen.

(On the other hand, the photo of me in love with Scap A at Dinosaur Journal suggests it’s about eight feet long, which would mean that it might be the type. *sigh*)

As we have seen, the captions in Jensen 1985 do not give specimen numbers, so we can’t tell whether the scap in his figure 6 is the holotype. And in the comparative figure 8 which shows both scaps, he maddeningly calls them “first specimen” and “second specimen” instead of giving numbers. We might guess that “first specimen” is the type; but it might instead refer to the order in which they were found or excavated. And we might guess that the specimen appearing in Jensen’s photos is the type, but it really would only be a guess — and one contradicted by the guess based on “first specimen”, since the photographed bone is the “second specimen”.

Jensen 1987

Jensen’s 1987 paper is primarily about brachiosaur material, but it does contain information relevant to to the present problem. Its figure 9 replicates Jensen 1985:figure 8 (the comparaive scapula line-drawings) but with an even less informative caption that doesn’t even say “first specimen” or “second specimen” for the two Supersaurus scaps. But then the text on page 602 may contain a key bit of information, given away in passing as though by accident:

I here remove the vertebra, BYU 5003, from Brachiosauridae and provisionally refer it to the Diplodocidae. This referral is based on two factors: principally, a bifurcate neural spine, and, secondly, the fact that two unusually large scapulocoracoids (Figs. 9B, 9G), found in the same (Dry Mesa) quarry, were referable to the Diplodocidae. One of these (BYU 5500, Fig. 9B) is the holotype of Supersaurus vivianae Jensen (1985).

Astonishingly, this is the first time in any of Jensen’s papers that he associates a specimen number with an illustration of either of the Supersaurus scaps. Jensen was notoriously careless with specimen numbers, but BYU 5500 does match his designation of the holotype in his 1985 paper, so we can perhaps be somewhat confident in this case.

The old specimen number BYU 5500 corresponds with the new number BYU 9025, which suggests that BYU 9025 is the the scap illustrated in Jensen 1987:figure 9B — which is scap A.

Curtice and Stadtman 2001

Curtice et al.’s (1996) paper referring the Ultrasauros holotype dorsal vertebra to Supersaurus does not say anything about the two Supersaurus scapulae. But the followup paper on Dystylosaurus (Curtice and Stadtman 2001) does. As noted in part 3 of this series, the “Supersaurus vivianae roll call” section remarks:

When [Supersaurus was] 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) …

This is not as helpful as it could be, as it lists both scapulae as “referred” without stating explicitly which was the holotype. But based on the evidence so far, we can be fairly confident that it it really was BYU 9025 (BYU 5500 of Jensen’s usage). The really useful information here is the designation that 9025 is a left scap and 12962 is the right. Since scap A is clearly left sided, this offers corroboration that is is the holotype, BYU 9025.

As we discussed before, Curtice and Stadtman (2001:39) went on to say:

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.

But this doesn’t make sense for two reasons. Most importantly, BYU 9025 is BYU 5500 of Jensen’s usage, and his 1985 paper makes it clear that this was the shorter of the two scaps at 8 feet, compared with 8 feet 10 inches for his BYU 5501 (i.e. BYU 12962). Shortening BYU 9025 would increase the discrepancy in length between the two scaps, not decrease it. Perhaps Curtice and Stadtman got the two scapulocoracoids’ specimen numbers reversed?

It’s also surprising because of the claim that the it was the proximal end that was inadvertently lengthened. The proximal end of a scapulocoracoid is the coracoid bone, which is thick and sturdy, and has a well defined proximal margin that would be difficult to inadvertently lengthen. Whereas the distal end — the farthest part of the scapula blade — is thinner and easily broken, and potentially shades into cartilage where the cartilaginous suprascapula attached. We could easily imagine the latter being subject to interpretation, but not really the proximal end. Perhaps Curtice and Stadtman (2001) were using the terms “proximal” and “distal” in the opposite sense to how they are generall applied to scapulae?

Dale McInnes’s involvement in preparation

In a comment on the first post in this series, Dale McInnes took issue with aspects of Curtice and Stadtman’s account of the repreparation of the scaps. According to McInnes, Jensen sent “the second specimen” (i.e. what we’re calling Scap B, if the caption to Jensen 1985:figure 9 is to be trusted) to RAM, and Phil Currie had McInnes prepare it in the late 1970s (i.e. after the initial popular publications on “Supersaurus” but well before Jensen’s formal publication in 1985). In an 11-foot-long field jacket, they found 9’2 of bone, which they reduced to 8’10 by closing four inches of open cracks.

So far, this account is consistent with that of Jensen (1985), who quotes only the final prepared length of 8’10”. But it doesn’t help us to make sense of Curtice and Stadtman’s account of re-preparing BYU 9025 to reduce its length, thereby creating a larger gap between its length and that of BYU 12962.

If Curtice and Stadtman were here reporting on the wrong scapula (i.e. they “stripped away the paint and resin” from BYU 12962) then it seems they may have undone some of the careful work done by McInnes and colleagues to preserve “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) [which might have been] an imprint of the cartilage”. If so, that is unfortunate indeed.

So which is which?

Jensen 1985 designated BYU 5500 (= BYU 9025) as the holotype and said it was 2.44 m (8′) long. He referred BYU 5501 (= BYU 12962) and said it was 8’10” long — but neither scap in its present form seems to be longer than 8′, so the differences in length reported by Jensen don’t help much.

Scap A (at the Dinosaur Journey Paleontological Museum in Fruita, Colorado) is a left scapulocoracoid. Curtice and Stadtman (2001) noted that BYU 9025 is a left scap (and BYU 12962 is a right scap), so that suggests that Scap A is BYU 9025.

Scap B (at the North American Museum of Ancient Life in Lehi, Utah) is a right scapulocoracoid, maybe 2.34 m long (7 feet 8 inches), based on the scale bar from Lovelace et al. (2008:figure 10). Their caption for that figure says it’s BYU 9025, but elsewhere they claim (incorrectly as far as I can tell) that BYU 12962 is the holotype, so something is wrong there.

The single most helpful thing in the literature is Jensen’s (1987:602) almost parenthetical comment that “(BYU 5500, Fig. 9B) is the holotype of Supersaurus vivianae“, as it’s the only published work that ties any specimen number to any illustration. Figure 9b shows Scap A — which indeed seems to be about eight feet long, according to the very fallible Mike-as-scalebar method.

But Curtice and Stadtman’s (2001:39) comments on re-prepping BYU 9025 suggest that it is the longer of the two elements, and  therefore (according to Jensen’s 1985 description) the referred element and not the holotype. We know that one of the scaps at least at one time measured 8’10, becausde of McInnes’s account of reducing the length of “the second specimen” to 8’10. But neither of them presently seems to be that long. (I hope Dale comments again, on this post, and is able to tell us whether the bone her worked on was Scap A or Scap B — and whether its present state is different from how he left it.)

Putting it all together, I think the weight of evidence says that Scap A is the holotype (BYU 9025, previously known as BYU 5500), with Jensen’s (1987:603) comment being our smoking gun. Other evidence includes Curtice and Stadtman’s (2001) observation that BYU 9025 is a left scap; its being about the right length (I trust my own scalebar, however informal, ahead of Lovelace et al.’s); and the fact that it is the better preserved of the two elements, making it a stronger candidate for having been selected as the holotype.

If that’s correct, then it is not without problems. It would follow that Lovelace et al. (2008:figure 10) is miscaptioned, being BYU 12962 and not 9025 as stated. It would also follow that Curtice and Stadtman were in error in describing the re-preparation of what was in fact the referred specimen BYU 12962 and not 9025 as stated.

Addendum: a cautionary tale

When I started this series of articles, I assumed that the NAMAL scap was the holotype (as you can see in the caption for the illustration of it in the first article). Why did I think that? Well, the Wikipedia article [archived link] says so: it has a photo of it captioned “The holotype of Supersaurus, scapulocoracoid BYU 9025″.

But as I got deeper into writing this series, I checked out the provenance of that photo on Wikipedia, only to find that it’s my own photo, as edited by Stephen O’Connor. Then I checked my emails to see whether I’d ever corresponded with Stephen, and I found that he’d emailed me three years ago including a link to this old SV-POW! photo of Scap A, and asking “I’m a little confused if the scapular in the image is a cast of holotype BYU 9025 or is it the opposing side, BYU 12962?” And I replied as follows:

Hi, Steve. I am attaching Jensen 1985, which is the canonical reference for this. Very poorly illustrated, though […]. Based on Figure 8 (page 708), the photo is a cast of “second specimen”. I’m attaching my photo of the holotype (“first specimen”) at NAMAL in Utah, in case it’s helpful.

So what happened here is that I over-interpreted a vague bit of hand-waving in Jensen 1985, fed it via Steve into Wikipedia, then trusted my own forgotten authority to reinforce the apparent legitimacy of my incorrect guess. I trusted Wikipedia on the identity of the NAMAL scap only to find it was my own assumption fed back to me.

A couple of days ago I read “Ninety percent of online journalism these days is nothing more than wannabe reporters summarizing other people’s assumptions from web sites that know how to game a search engine”.  I am pleased to find that I am efficient enough to cut out the wannae-reporter middle man from this process, and just summarise my own assumptions.

References

  • 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. giant of the giants. Denver Post, Empire Magazine. May 13, 1973, pp 14ff.
  • George, Jean. 1973b. Supersaurus, the biggest brute ever. Reader’s Digest (June 1973):51–56.
  • George, Jean. 1973c. Supersaurus, the greatest of them all. Readers Digest (August 1973), page-range unknown.
  • 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.
  • 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.

 

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 (2001:36-39) 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
4503 Anterior dorsal vertebra Curtice & Stadtman 2001
9044 Posterior dorsal vertebra Curtice et al. 1996
12814 Posterior dorsal vertebra Curtice & Stadtman 2001
13018 Pelvis (right ilium, four sacral vertebrae) Curtice & Stadtman 2001
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 2001
9045 Caudal vertebra Curtice & Stadtman 2001
12639 Caudal vertebra Curtice & Stadtman 2001
12819 Caudal vertebra Curtice & Stadtman 2001
12843 Caudal vertebra Curtice & Stadtman 2001
9025 Left scapulocoracoid Holotype
12962 Right scapulocoracoid Jensen 1985
13744 Left ulna Curtice & Stadtman 2001
12390 Carpal Curtice & Stadtman 2001
12424 Right pubis Curtice & Stadtman 2001
12946 Right ischium Jensen 1985
12555 Left ischium Curtice & Stadtman 2001
9000 Phalanx Curtice & Stadtman 2001

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.)

References

  • 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).

 

References

  • 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.