And so the series continues: part 9, part 10 and part 11 were not numbered as such, but that’s what they were, so I am picking up the numbering here with #12.

If you’ve been following along, you’ll remember that Matt and I are convinced that BYU 9024, the big cervical vertebra that has been referred to Supersaurus, actually belongs to a giant Barosaurus. If we’re right about, then it means one of two things: either Supersaurus synonymous with Barosaurus, or there are two diplodocids mixed up together.

Jensen (1987:figure 8c). A rare — maybe unique? — photograph of the right side of the big “Supersaurus” cervical vertebra BYU 9024. We assume this was taken before the jacket was flipped and the presently visible side prepped out. We’d love to find a better reproduction of this image.

Which is it? Well, seventeen years ago Curtice and Stadtman (2002:39) concluded that “all exceptionally large sauropod elements from the Dry Mesa Quarry can be referred to one of two individuals, one a Supersaurus and one a Brachiosaurus […] further strengthening the suggestion that all of the large diplodocid elements belong to a single individual.” It is certainly suggestive that, of all the material that has been referred to Supersaurus, there are no duplicate elements, but there are nice left-right pairs of scapulocoracoids and ischia.

But do all those elements actually belong to the same animal? One way to address that question is to look at their relative sizes and ask whether they fit together.

Sadly, when Matt and I were at BYU we didn’t get to spend time with most of these bones, but there are published and other measurements for a few of them. Jensen (1985:701) gives the total lengths of the two scapulocoracoids BYU 9025 and BYU 12962 as 2440 and 2700 mm respectively. Curtice et al. (1996:94) give the total height of the last dorsal BYU 9044 as 1330 mm. We have measured the big cervical BYU 9024 (probably C9) ourselves and found it to measure 1370 mm in total length. Finally, while there is no published measurement for the right ischium BYU 12949 (BYU 5503 of Jensen’s usage), we can calculate it from the scalebar accompanying Jensen’s illustration (with all the usual caveats) as being 1235 mm long.

Jensen (1985:figure 7a). BYU 12946 (BYU 5503 of his usage), the right ischium assigned to Supersaurus. By measuring the bone and the scalebar, we can calculate the length as 1235 mm.

Do these measurements go together? Since we’re considering the possibility of Supersaurus being a big Barosaurus, the best way to test this is to compare the sizes of the elements with the corresponding measurements for AMNH 6341, the best known Barosaurus specimen.

For this specimen, McIntosh (2005) gives 685 mm total length for C9, 901 mm total height for D9 (the last dorsal) and 873 mm for the ischia (he only provides one measurement which I assume covers both left and right elements). The scapulocoracoids are more complex: McIntosh gives 1300 mm along the curve for the scapulae, and 297 mm for the length of the coracoids. Assuming we can add them in a straight line, that gives 1597 mm for the full scapulocoracoid.

I’ve given separate measurements, and calculated separate ratios, for the left and right Supersaurus scapulocoracoids. So here’s how it all works out:

Specimen Element Size (mm) Baro (mm) Ratio Relative
9024 Mid-cervical vertebra 1370 685 2.00 124%
9044 Last dorsal vertebra 1330 901 1.48 92%
9025 Left scapulocoracoid 2440 1597 1.53 95%
12962 Right scapulocoracoid 2700 1597 1.69 105%
12946 Right ischium 1235 873 1.41 88%

The first five columns should be self-explanatory. The sixth, “proportion”, is a little subtler. The geometric mean of the size ratios (i.e. the fifth root of their product) is 1.6091, so in some sense the Dry Mesa diplodocid — if it’s a single animal — is 1.6 times as big in linear dimension as the AMNH 6341 Barosaurus. The last column shows each element’s size ratio divided by that average ratio, expressed as a percentage: so it shows how big each element is relative to a hypothetical isometrically upsized AMNH Barosaurus.

As you can see, the cervical is big: nearly a quarter bigger than it should be in an upscaled Barosaurus. The two scaps straddle the expected size, one 5% bigger and the other 5% smaller. And the dorsal and ischium are both about 10% smaller than we’d expect.

Can these elements belong to the same animal? Maaaybe. We would expect the neck to grow with positive allometry (Parrish 2006), so it would be proportionally longer in a large individual — but 25% is a stretch (literally!). And it also seems as though the back end of the animal (as represented by the last dorsal and ischium) is growing with negative allometry.

A nice simple explanation would be that that all the elements are Supersaurus and that’s just what Supersaurus is like: super-long neck, forequarters proportionally larger than hindquarters, perhaps in a slightly more convergent-on-brachiosaurs way. That would work just fine were it were not that we’re convinced that big cervical is Barosaurus.

Here’s how that would look, if the BYU Supersaurus is a large Barosaurus with different proportions due to allometry. First, Scott Hartman’s Barosaurus reconstruction as he created it:

And here’s my crudely tweaked version with the neck enlarged 24% and the hindquarters (from mid-torso back) reduced 10%:

Does this look credible? Hmm. I’m not sure. Probably not.

So: what if we’re wrong?

We have to consider the possibility that Matt and I misinterpreted the serial position of BYU 9024. If instead of being C9 it were C14 (the longest cervical in Barosaurus) then the AMNH analogue would be 865 mm rather than 685 mm. That would make it “only” 1.58 times as long as the corresponding AMNH vertebra, which is only 3% longer than we’d expect based on a recalculated geometric mean scale of 1.5358 — easily within the bounds of allometry. We really really really don’t think BYU 9024 is a C14 — but it’s not impossible that its true position lies somewhere posterior of C9, which would mean that the allometric interpretation would become more tenable, and we could conclude that all these bones do belong to a single animal after all.

Of course, that would still leave the question of why the Supersaurus scapulocoracoids are 10% bigger than we’d expect relative to the last dorsal vertebra and the ischium. One possible explanation would be to do with preparation. As Dale McInnes explained, there’s some interpretation involved in preparing scaps: the thin, fragile distal ends shade into the cartilaginous suprascapula, and it’s at least possible that whoever prepped the AMNH 6341 scaps drew the line in a different place from Dale and his colleagues, so that the Barosaurus scaps as prepared are artificially short.

Putting it all together: it might easily be the case that all the elements really do belong to a single big diplodocid individual, provided that the big cervicals is more posterior than we thought and the AMNH scaps were over-enthusiastically prepped.

References

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I got a wonderful surprise a couple of nights ago!

Supersaurus referred scapulocoracoid BYU 12962 back when it was still in the ground. Rough composite assembled from screenshots of the video below, from about 23m17s.

I found myself wondering where the widely quoted (and ludicrous) mass estimate of 180 tons for Ultrasauros came from, and went googling for it. That took me to a blog-post by Brian Switek, which linked to a Google Books scan of what turned out to be my own chapter on the history of sauropod research (Taylor 2010) in the Geological Society’s volume Dinosaurs and Other Extinct Saurians: a Historical Perspective. So it turns out that I once knew the answer to that question. My chapter references McGowan (1991:118), which says:

Jim Jensen’s (1985) Ultrasaurus (“beyond lizard”), found in Colorado in 1979, had an estimated length of more than ninety-eight feet (30 m), compared with seventy-four feet (22.5 m) for the Berlin specimen of Brachiosaurus. This is a length increase of 1.32, so the weight increase would be (1.32)^3 = 2.3, giving an estimated weight of almost 180 tons.

[As I noted in my 2010 chapter, that’s based on Colbert’s (1962) equally silly estimate of 78 tonnes for MB.R.2181 (formerly HMN S II), the Girafatitan brancai paralectotype.]

So that’s a funny story and a mystery solved, but where it gets really good is that as I was grubbing around in the search results that led me to that conclusion, I stumbled on Episode 21 of the I Know Dino podcast, which contains a glorious embedded video: The Great Dinosaur Discovery, a 1976 film by BYU about Jensen’s work at quarries including Dry Mesa, and heavily featuring bones of what would become Supersaurus!

It’s very well worth 25 minutes of your time, despite the horrible 1970s documentary music, and brings actual new information to the table.

Some of the highlights include:

— Right from the start, seeing Jensen himself: someone I’ve been sort of familiar with from the literature, but never really imagined as being an actual human being.

— From about two minutes in, Jensen seems be uncovering bones in dry sand, rather like kids in a palaeo pits at some museums. It takes about one minute to uncover a nice tibia. Is it ever really that easy? Is the Dry Mesa quarry that easy to work?

— Putting faces to the important names of Vivian and Eddie Jones, the uranium prospectors who first led Jensen to several of his important sites, and after whom the species Supersaurus vivianae and Dystylosaurus edwini were named.

Vivian “Supersaurus” Jones and Eddie “Dystylosaurus” Jones in the field [from about 4m41s in the video]

— From about 13m30s onwards, we see what I think must be the Supersaurus pelvis that’s now on display at the North American Museum of Ancient Life. (It doesn’t actually look all that big, in the scheme of things.)

— From 16m50s onwards, things start to get real, with the uncovering (real or re-enacted) of the first Supersaurus scapulocoracoid: that is, the one that Jensen referred to in his 1985 paper as “first specimen”, but which in the end he did not designate as the holtotype. This bone, once accessioned, became BYU 12962 (but Jensen refers to it in his papers as BYU 5501).

The first appearance in the film of the Supersaurus scap BYU 12962 fully unconvered [18m11s]. You can easily recognise it as the bone that Jensen posed with from the lobe-shaped acromion process.

— Within seconds of our seeing the scap, Jensen decides the best thing to do is illustrate how it’s “like a sidewalk” by walking up and down on it. Seriously.

Oh, Jim.

— At about 19m30s, we see what is probably the big Barosaurus vertebra BYU 9024 whose identity Jensen changed his mind about a couple of times. Unfortunately, the film quality is very poor here, and you can’t make much out.

— From 20 minutes in, the video shows comparative skeletal reconstructions of Brontosaurus (clearly from Marsh 1891), “Brachiosaurus” [i.e. Giraffatitan] (clearly from Janensch 1950) and Supersaurus. The fascinating thing is that the latter is restored as a brachiosaurid — in fact, as a scaled-up Janensch-1950 Giraffatitan with some tweaks only to the head and anterior neck. So it seems Jensen thought at this time that he’d found a giant brachiosaur, not a diplodocid. (Note that this film was made three years before the Ultrasaurus scapulocoracoid was discovered in 1979, so the presumed brachiosaurid identity cannot have rested in that.)

Brontosaurus (yellow), Brachiosaurus (blue), and Supersaurus (white) — which is restored as a brachiosaurid.

— During this section, a fascinating section of narration says “The animal found here is so much larger than anything ever dreamed of, the press, for lack of scientific name, called it a Supersaurus.” If this is legit, then it seems Jensen is not guilty of coining this dumb name. It’s the first I’ve heard of it: I wonder if anyone can corroborate?

— As 22m06s we are told: “It was an AP newsman who broke the story to the world. Time and Life followed. Reader’s Digest ran the story. And National Geographic, one of the quarry sponsors, began an article.” I would love to get hold of the AP, Time, Life and National Geographic articles. Can anyone help? It seems that all these organisations have archives online, but they all suffer from problems:

Here’s that scap again, in the process of being excavated. [22:05]

— As 22m40s, Jack McIntosh turns up to give an expert opinion. I don’t know how much film of him there is out there, but it’s nice that we have something here.

Everyone’s favourite avocational sauropod specialist, Jack McIntosh.

— At 23:17, we get our best look at the scap, with a long, slow pan that shows the whole thing. (That’s the sequence that I made the composite from, that we started this whole post with.)

All in all, it’s a facinating insight into a time when the Dry Mesa quarry was new and exciting, when it was thought to contain only a single giant sauropod, when that animal was known only informally as “Supersaurus” having been so nicknamed by the media, and when it was (it seems) thought to be brachiosaurid. Take 25 minutes, treat yourself, and watch it.

Update (the next day)

The Wikipedia entry on Jim Jensen says that “In 1973, Brigham Young University cooperated with producer Steve Linton and director John Linton in order to produce The Great Dinosaur Discovery, a 1-hour-long color documentary showing Jensen’s on-site finds in Dry Mesa. […] the full-length documentary was reduced to a 24-minute-long mini-film which started airing on American television channels throughout the USA as of 1976.”

Can anyone confirm that the original date was 1973, and not 1976 as given on the short version that’s linked above?

And, more important, does anyone have access to the full-hour version?

 

References

 

One of the strange things about Jensen’s 1985 paper is that the abstract implies that he informally considered the Ultrasauros scapulocoracoid to be the type specimen.

Cast of BYU 9462, scapulocoracoid referred to Ultrasaurus macintoshi (possibly intended to the be the holotype), at Brigham Young Museum. This photo is one of a series in which I turned the cast in place to obtain photos for a photogrammetric model.

Here’s what Jensen (1985:697) says:

From 1972 to 1982 three exceptionally large sauropod scapulocoracoids […] were collected from the base of the Brushy Basin Member of the Upper Jurassic, Morrison Formation, in western Colorado. Two of the scapulae are conspecific, but the third represents a second genus and possibly a new family. The two conspecific specimens are described here as Supersaurus vivianae; the second genus is described as Ultrasaurus mcintoshi.

But on page 704, he formally and unambiguously nominated the dorsal vertebra as the holotype:

Family Brachiosauridae
Ultrasaurus macintoshi, n. gen., n. sp.
[…]
Holotype.—BYU 5000, posterior dorsal vertebra.
Referred material.—BYU 5001, scapulocoracoid.

Stranger still, two years after this, Jensen (1987:603) straight up claimed – quite incorectly — that the scap was the Ultrasaurus holotype:

In 1979 a scapulocoracoid, 2.70 m (8’10”) long (Figs. 6A-B, 9I) was collected in the Dry Mesa Quarry. This scapula, BYU 5000 [sic; he meant BYU 5001], is readily referrable to the Brachiosauridae (Fig. 9H) and is the holotype of Ultrasaurus macintoshi Jensen, 1985.

But it sayin’ it’s so don’t make it so. The joint evidence of the 1985 abstract and the 1987 extract suggest that Jensen probably intended the scap to be the holotype and somehow accidentally designated the wrong element — or was persuaded to do so against his own judgement. But however it came about, the scap is not the holotype.

BYU 9462, the scapulocoracoid referred by Jensen to Ultrasauros. Mike Taylor for scale, doing a Jensen. Note that the actual specimen is very much a mosaic of bone fragments, rather than the solid, complete bone that the cast might suggest.

Instead, the holotype remains the large posterior dorsal vertebra BYU 9044 (BYU 5000 of Jensen’s usage) which Curtice et al. (1996) convincingly showed to be diplodocid, and referred to Supersaurus, making Ultrasaurus (and its subsequent replacement Ultrasauros) a junior synonym of that name.

Ultrasauros macintoshi holotype dorsal vertebra BYU 9044, in left lateral view, photographed at the North American Museum of Natural Life. Sorry about all the reflections off the glass case.

But wait, wait. We’ve shown that there are probably two big diplodocids in the Dry Mesa quarry: Barosaurus (represented by the big cervical BYU 9024) and something different (represented by the “Dystylosaurus” dorsal, BYU 4503). The Ultrasauros holotype vertebra probably belongs to one of these (unless there are three big diplodocids in there but we’ll ignore that possibility). But we can’t tell whether the Ultrasauros dorsal belongs with the Barosaurus cervical or the Dystylosaurus dorsal.

All of this means that Ultrasauros is a synonym, but we don’t know of what. It might be Barosaurus; it might be Supersaurus, whatever that is, if it’s not a nomen dubium; and it might be Dystylosaurus, if Supersaurus is a nomen dubium. Yikes.

Well, then. Is it Barosaurus? Here are the dorsal vertebrae of the fairly complete AMNH specimen, in a composite that I put together a few years ago from McIntosh’s (2005) illustrations:

Barosaurus lentus AMNH 6341 dorsal vertebrae 1 to 9 in anterior, left lateral and posterior views. Modified from McIntosh (2005:figure 2.5)

We can compare these with the photo above of the Ultrasauros dorsal in left lateral view, and with this one in posterior view:

Ultrasauros macintoshi holotype dorsal vertebra BYU 9044, in posterior view, photographed at the North American Museum of Natural Life. Sorry about all the reflections off the glass case.

I wouldn’t want to hang too much on those poor quality, postage-stamp-sized monochrome photos of the Barosaurus dorsals. And I’m also more than aware of the imperfections in my photos of the “Ultrasauros” dorsal. But to the naked eye, there’s nothing here that immediately screams they couldn’t be the same thing.

Lull’s (1919) monograph on the original Barosaurus specimen YPM 429 also illustrated a posterior dorsal, which he designated D9. Lull helpfully provided both drawings and photographs:

Lull (1919: plate IV: parts 4-6). Barosaurus lentus holoype YPM 429, 9th dorsal vertebra in anterior, right lateral and posterior views (line drawing).

Lull (1919: plate IV: parts 4-6). Barosaurus lentus holoype YPM 429, 9th dorsal vertebra in anterior, right lateral and posterior views (photographs).

With something a bit more substantial to go on, the case for the Ultrasaurus vertebra being Barosarus doesn’t look so good.

Most obviously, its centrum is much longer than that of the Barosaurus dorsal — and indeed, than any posterior dorsal vertebra of any diplodocid. This character is the reason — the only reason — that Jensen (1985:704) initially thought it was brachiosaurid: “Ultrasaurus shares the family characteristic of a long dorsal centrum with Brachiosaurus, but in other features it has no parallel with that genus”. Curtice et al. (1996:90) argued that “extensive transverse and oblique crushing artificially elongate the centrum […]. Without the crushing […] the centrum shrinks considerably in length”. Based on my photos, I can’t really see any justification for this claim, but Curtice spent waaay more time with this specimen than I have done, so I’m going to hold that observation lightly.

But there are other features of BYU 9044 that are not a good match for Lull’s illustrations. These include a less robust looking and more prominently laminated subzygapophyseal neural arch, and a neural spine that is anteroposteriorly broader but transversely narrower than in Lull’s specimen. Also, the apex of the neural spine in anterior or posterior view is convex in BYU 9044 but concave in YPM 429.

None of these characters can be considered to definitely separate BYU 9044 from Barosaurus, especially in light of that element’s crushing, the imperfect preservation of Lull’s specimen, the possibility of serial variation, and the fact that I am working only from photographs and drawings of both. But when you put all the differences together, they combine to at least suggest that Ultrasaurus is not Barosaurus — and that it is therefore most likely Supersaurus/Dystylosaurus.

So what about the scapulocoracoid?

It looks brachiosaurid, as Jensen observed. Curtice et al. (1996) concurred, and referred it to Brachiosaurus sp. In fact, when compared with the best-preserved scapula of a known brachiosaurid Giraffatitan HMN Sa 9), it’s not all that similar:

Brachiosaurid scapulocoracoids. Left: cast of BYU 9462, right scapulocoracoid referred to Ultrasauros macintoshi, at Brigham Young Museum, with Mike Taylor for scale. Right: HMN Sa 9, left scapula only (coracoid is not co-ossified) of Giraffatitan brancai, scaled to same blade length as BYU 9462, photo by FunkMonk (Michael B. H.), CC By-SA.

It’s apparent, when looking at the two scaps together, that there are significant differences: BYU 9462 is in every respect less robust, having a less expanded distal blade, a more constricted midshaft, a less promiment and narrower acromial ridge and a much less robust ventral ridge. In addition, the acromion process is hooked in Sa 9, so that its tip projects laterally, whereas it is rounded in BYU 9462. Finally, the shapes of the distal blades differ, having a gently rounded profile in BYU 9462 but a distinct kink in Sa 9 where the dorsal part of the margin inclines anterodorsally.

What does all this mean? We don’t know. I’m certainly not arguing that BYU 9462 is not brachiosaurid, as it does seem to differ less from Giraffatitan scapulae than from those of other sauropods. All I’m saying is that it’s not all that Giraffatitan-like. But then every bone that we know from both Giraffatitan and Brachiosaurus is significantly different between them (Taylor 2009:798), so if a subsequently discovered associated skeleton one day shows us that this is just what the scapulocoracoid of Brachiosaurus altithorax looks like, it would not be a huge shock.

Still, as things stand, I’m not really convinced that the referral to Brachiosaurus sp. — based on a not-particularly-close resemblance to a completely different brachiosaurid — is rock solid. Had the scap been the type specimen, as Jensen probably intended, I would consider that the sound move would be to continue to consider Ultrasauros as a distinct taxon from Brachiosaurus, unless and until an associated specimen demonstrates that synonymy is warranted.

But that’s all in Shoulda-Coulda-Woulda territory. In fact the scapulocoracoid is not the type specimen, and so the name Ultrasauros remains sunk, even though we can’t tell whether it’s a synonym of Barosaurus, Supersaurus or Dystylosaurus. That will remain the case unless someone takes the initiative to raise a new name for the scapulocoracoid — which we can, at least, be confident does not belong the diplodocid Ultrasauros. I think that would be a reasonable move for someone to make, but it’s not one that I feel moved to make myself.

… and with that, I think we have finally reached the end of this series. We may revisit it in the future to say more about Jimbo, or maybe Dinheirosaurus, but this series has been the substance of what we have to say. Hope you’ve enjoyed it!

References

 

 

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

 

Last time, I noted that photographs of the exact same object, even under the same lighting conditions, can come out different colours. That is one of the two reasons why I am not persuaded that the very different colours of my photos of the two Supersaurus scapulae is strong evidence that they are from different individuals.

The other reason is that, as BJ Nicholls pointed out in a comment on that post, “Color in fossils can be misleading even in real life. As bones erode out, surface float pieces can be bleached on exposed surfaces. Bones within a bed can vary a lot in color too.”

Here’s an example:

What we have here are some of bones from the skeleton of Charlie the monitor lizard. After I extracted these bones from Charlie’s decomposing carcass ten years ago (can it really have been that long?!) I have left them sitting on a tray, awaiting articulation.

At the top of this photo is a scapulocoracoid; at the bottom, some dorsal vertebrae. As you can see, the former has bleached white, while the latter have remained ivory coloured. Remember, these are bones from the same individual that were extracted at the same time (give or take maybe a day or two), and that have been in exactly the same situation (on a tray, on a window sill, in my office) ever since.

The moral: bone colour doesn’t really tell you much at all.

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.