The Past, Present and Future of Jensen’s “Big Three” sauropods

September 17, 2019

My talk (Taylor and Wedel 2019) from this year’s SVPCA is up!

The talks were not recorded live (at least, if they were, it’s a closely guarded secret). But while it was fresh in my mind, I did a screencast of my own, and posted it on YouTube (CC By). I had to learn how to do this for my 1PVC presentation on vertebral orientation, and it’s surprisingly straightforward on a Mac, so I’ve struck while the iron is hot.

For the conference, I spoke very quickly and omitted some details to squeeze the talk into a 20-minute slot. In this version, I go a bit slower and make some effort to ensure it’s intelligible to an intelligent layman. That’s why it runs closer to half an hour. I hope you’ll find it worth your time.

References

Posted by Mike Taylor
Filed in "Ultrasauros", Barosaurus, brachiosaurids, CC BY, cervical, conferences, diplodocids, dorsal, Dystylosaurus, mystery vertebra, neural spine, Nomenclature, papers by SV-POW!sketeers, Science communication, Supersaurus, SVPCA, timely, video
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Supersaurus, Ultrasaurus and Dystylosaurus in 2019, part 12: how big are the giant diplodocid bones in the Dry Mesa Quarry?

August 19, 2019

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

Posted by Mike Taylor
Filed in Barosaurus, cervical, coracoid, diplodocids, dorsal, Dystylosaurus, ischium, math, scapula, Supersaurus
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Supersaurus timeline

July 17, 2019

The history of Supersaurus — and its buddies Ultrasauros and Dystylosaurus — is pretty complicated, and there seems to be no one source for it. But having read a lot about these animals in the process of writing eleven mostly pretty substantial posts about them, I feel like I’m starting to put it all together. This post is an attempt at recognising the landmarks in this history, in chronological order. Please leave a comment if you find a mistake or if I missed anything.

1943 — Sawmill operator Eddie Jones and his wife Vivian are prospecting for uranium during WWII. They find a brachiosaur skeleton in an advanced state of erosion at Potter Creek in the Uncompahgre Upwarp (Jensen 1987:592). (Jensen 1985a:697 says the humerus was also collected in this year, but that is contradicted by other accounts.)

1955 — Eddie and Vivian Jones collect the brachiosaur humerus and donate it to the Smithsonian Institition (George 1873b:53), where it is accessioned as USNM 21903 and put on display some time before March 1959 (Anonymous 1959).

USNM 21903, a left humerus of ?Brachiosaurus altithorax, discovered by Eddie and Vivian Jones. From the NMNH’s specimen gallery page, which gives the collection date as 1955. When I first saw this specimen, my gut reaction was that it was not slender enough to be Brachiosaurus, but note that the midshaft is very extensively restored. It may be that the intact bone was longer than the version we now see.

1958 — Jensen sees the Smithsonian humerus and finds the Jones family, who take him to the humerus location in Potter Creek and to three other Uncompahgre fossil localities (Jensen 1985a:697).

1964 — Jensen makes his first collection from the Uncompahgre Upwarp (Jensen 1985b:710).

1971 — Jensen sees a theropod toe bone at the Joneses’ home and asks where they found it. They tell him “On the Uncompahgre” (George 1973b:53), i.e. probably specifically from Dry Mesa, awakening his interest in that quarry.

1972 — In April (George 1973b:53), Jensen makes his first collection of material from Dry Mesa, one of the Uncompahgre localities found by the Joneses (Jensen 1985a:697).

In August (George 1973b:51-52) a large sauropod pelvis is found. This seems to have been the first element found that hinted at a very large sauropod at Dry Mesa (George 1973b:52-53).

Jensen displays the first Dry Mesa pelvis, still in the ground, in a frame from the 1976 version of The Great Dinosaur Discovery [13m53s].

Later this year, the first large Dry Mesa scapulocoracoid is found (Jensen 1985b:717). This would later be referred to as the “first specimen” of Supersaurus (e.g. Jensen 1985a:figure 8), but it was the subsequently discovered “second specimen” that would become the holotype when the genus was formally named (Jensen 1985a:701).

[NOTE. I am increasingly concerned that this might be wrong, and that the first scapulocoracoid found might after all have become the holotype. How to establish this? I sense yet another blog-post incoming.]

This is also the date given in the Dystylosaurus systematic palaeontology of Jensen (1985a:707). This may be an error as it is seven years before the date given for Supersaurus and Ultrasaurus, both of which names were known long before that of Dystylosaurus. but Curtice and Stadtman (2001:33) corroborate this early date for the discovery of the Dystylosaurus vertebra, and the relatively low specimen number BYU 4503 perhaps also suggests early collection and accessioning.

1973 — First published accounts of the giant sauropod material from Dry Mesa. The earliest may be that of Jean George (1973a) in the Denver Post’s Empire Magazine, on May 13. This is subsequently condensed into an account (George 1973b) in Reader’s Digest for June (not August as stated by Jensen 1985b:717, who also mis-cites the title). This latter account may be responsible for coining the informal name “Supersaurus” (Jensen 1985b:717), which would later be confirmed as the scientific name. (“There ‘Supersaurus,’ as we will call him, now awaits an official name and taxonomic classification.” — George 1973b:53.)

On Tuesday 13 November, a one-hour film about the dinosaurs of Dry Mesa, The Great Dinosaur Discovery, premieres in Delta, Colorado (Herald 1973). It is to be aired on 225 public TV stations across the USA.

Brigham Young University publishes an eight-page pamphlet, also titled The Great Dinosaur Discovery (House et al. 1973) to introduce the documentary. In it, Jensen is said to refer to the giant sauropod as “Big George”, but this nickname never caught on. “Both of Big George’s eight-foot-long shoulder blades were uncovered at the quarry” by this stage. The large pelvis is now considered probably not to belong to Big George. Jensen thinks the new specimen “will not only require a new genus and species, but also a new family and perhaps even a new infra-order”.

1974 — Jensen hopes that the Dry Mesa Quarry will be developed as a tourist destination along the lines of Dinosaur National Monument, “with provisions for public access and viewing while the scientific work continues” (Barnes 1974:40) — a dream that would never come to pass.

1976 — A shortened version of The Great Dinosaur Discovery is made available for schools. (At present, this is the only version we have access to.) In this version of the film (and presumably in the 1973 original, if the 1976 version was made only by cutting), the name “Supersaurus” is used informally, and a reconstruction of the animal [20 minutes in] shows it modelled after Brachiosaurus rather than a diplodocid.

A newspaper report about a large sauropod humerus (Anonymous 1976:1) suggests that Jensen believes belongs to “Supersaurus”. But no Supersaurus humerus is subsequently mentioned, and the bone probably belongs to another taxon. Its slenderness suggests it may belong to a brachiosaur: it is probably the Potter Creek humerus or more likely a cast of it, misreported.

1977 — Jensen is informally referring to the giant sauropod as “Supersaurus jenseni” (Look 1977:37). It is still felt that “it is a good guess that the big animal looked something like a cousin to the Brachiosaurus“.

“Late 1970s” — Dale McInnes prepares the “2nd specimen” Supersaurus scapulocoracoid, probably referring to the second to be discovered, which we believe is BYU 9025, eventually to become the holotype. (The “1st specimen” has already been prepared by this point.) In the 11-foot-long jacket, they find 9’2″ of bone, which they reduce to an 8’10” scapulocoracoid by closing cracks.

1978 — John Ostrom’s (1978) popular account of new ideas about dinosaurs in National Geographic mentions Supersaurus, and still considers it probably “built along the lines of Brachiosaurus“. He says that “a pair of shoulder blades eight feet long” have been dug up, so both of the elements that might be the holotype were known by this point.

1978 — Olshevsky (1991:139) gives this as the date of Jensen’s first informal use of the name “Ultrasaurus”, but this must be considered suspect as other sources say the key specimen of this genus was not discovered until 1979.

1979 — The brachiosaurid scapulocoracoid BYU 9462 (BYU 5001 of Jensen’s usage) is discovered and collected from the Dry Mesa Quarry (Jensen 1987:603 — although in this passage he incorrectly says the specimen number is BYU 5000). The discovery is witnessed by a Japanese film crew that is making a documentary about the Dry Mesa dinosaurs (Jensen 1985b:717). Jensen begins to refer to the specimen informally as “Ultrasaurus”.

Miller et al. (1991: figure 4b). “Loading plaster-jacketed bones at the Dry Mesa quarry, 1979. Left to right, Richard Jensen, Jim Jensen, Japanese TV crew.” It’s obvious from the shape of the plaster jacket that this is the “Ultrasaurus” scapulocoracoid BYU 9462.

The earliest reports of “Ultrasaurus” appear in the media (Webster 1979, Whitney 1979, Martin 1979).

At the climax of an eleven-day lecture tour in Japan, Jensen presents casts of three bones to the the people of Japan (Anonymous 1979): the “Ultrasaurus” scapulocoracoid BYU 9462, the Potter Creek humerus USNM 21903 and a large rib referred to Brachiosaurus sp.

This is the date given in the Ultrasaurus systematic palaeontology of Jensen (1985a:704).

This is also the date given in the Supersaurus systematic palaeontology of Jensen (1985a:701): “COLLECTOR.—James A. Jensen 1979”. This late date is surprising, as Supersaurus material was known as early as 1972 and both scapulocoracoids had been excavated by the time of Ostrom’s (1978) account.

1982 — Last collection of material considered for 1985 descriptive paper (Jensen 1985a:697).

Wilford (1982), in a popular article in the New York Times apparently written with Jensen’s collaboration, says that Supersaurus “may be an enlarged variation of brachiosaurus” and that Ultrasaurus “must have been even larger”, indicating that Supersaurus may still have been thought of as brachiosaurid well after the discovery of Ultrasaurus.

1983 — As of this date, approximately 100 tons of material collected by Jensen for BYU remains unprepared (Jensen 1985a:709).

Kim (1983) names a Korean sauropod Ultrasaurus tabriensis, intending it to be a new species of Jensen’s genus. However, since the name Ultrasaurus has not previously been formally published, Kim inadvertently preoccupies the name. (The Korean sauropod was thought enormous because of the size of its “ulna”; however, this bone is clearly a humerus, and of only moderate size for a sauropod. The taxon is generally considered undiagnosable, and the name therefore a nomen dubium.)

1985 — Jensen’s main descriptive paper (Jensen 1985a) is published, formally naming three new sauropod genera. Supersaurus (now considered to be of indeterminate family) is based on the scapulocoracoid BYU 9025 (BYU 5500 of his usage); Ultrasaurus (considered to be a brachiosaurid) is based on the posterior dorsal vertebra BYU 9044 (BYU 5000 of his usage) rather than the scapulocoracoid; and Dystylosaurus (which “no doubt represents a new sauropod family”) is based on the anterior dorsal vertebra BYU 4503 (BYU 5750 of his usage). This paper is accompanied by a broader overview of the Uncompahgre dinosaur fauna (Jensen 1985b) in which he says of the second Supersaurus scapulocoracoid that “it displays diplodocid affinities” (p717).

1987 — Jensen’s second descriptive paper removes the large Dry Mesa cervical vertebra BYU 9024 (BYU 5003 of his usage) from Ultrasaurus and refers it to Supersaurus (Jensen 1987:600-602). It seems from this paper that he may have intended the Ultrasaurus scapulocoracoid BYU 9462 (BYU 5001) to be the holotype of that genus (Jensen 1987:603). By this point, Supersaurus seems to have been recognised as diplodocid: “two unusually large scapulocoracoids … were referrable to the Diplodocidae. One of these (BYU 5500, Fig. 9B) is the holotype of Supersaurus vivianae” (p602).

1988 — A second large pelvis, BYU 13018, is found in Dry Mesa quarry (Wakley 1988, Wilford 1988, Miller et al. 1991:40). This is quickly recognised as belonging to Supersaurus, and will later be formally referred to that genus (Curtice and Stadtman 2001:38-39). It is now on display at the North American Museum of Ancient Life.

1990 — In the landmark encyclopaedia The Dinosauria, McIntosh (1990) describes Supersaurus as a diplodocid (p391), Ultrasaurus (Jensen) as “a very large brachiosaurid” based on the type vertebra and referred scapulocoracoid (p384), and the Dystylosaurus vertebra as “clearly brachiosaurid” (p384).

1991 — McGowan (1991:118) originates the idea that Ultrasaurus massed 180 tonnes, based on its restoration as a brachiosaurid 1.32 times as large in linear dimension as the Berlin Giraffatitan brancai paralectotype MB.R.2181 (formerly HMN SII) whose mass Colbert (1962) had grossly overestimated at 78 tons.

Olshevsky (1991:139), recognising the preoccupation of the name Ultrasaurus by Kim’s (1983) genus, raises the replacement name Ultrasauros for Jensen’s genus, with Jensen’s blessing. He had originally suggested the replacement name Jensenosaurus, but Jensen disliked this and suggested the variant spelling that was used instead (Curtice et al. 1996:87-88).

Miller et al. (1991:40) suggest that the holotype dorsal vertebra of Ultrasaurus (i.e. Ultrasauros) might by diplodocid, due to its similarity to the sacral vertebrae of the 1988 pelvis whose tall neural spines “most closely resemble the diplodocids”.

1994 — John Sibbick’s classic artwork of Supersaurus and Ultrasaurus, with Seismosaurus, is published in David Norman’s Prehistoric Life: The Rise of the Vertebrates.

1995 — Curtice (1995), in an SVP abstract, reassigns to Supersaurus the clearly diplodocid caudal vertebra BYU 9045 (BYU 5002 of Jensen’s usage), which Jensen had assigned to Ultrasaurus.

The caudal vertebra BYU 9045 (BYU 5002 of Jensen’s usage), in (from left to right) posterior, right lateral, and anterior views. Modified from Jensen (1985a:figures 2E, 3E and 2D respectively), an including his original scalebars. These are consistent between the photos in posterior and lateral views, and if accurate indicate that the vertebra is 1.18 m in total height.

1996 — Curtice et al. (1996) persuasively show that the holotype of Ultrasauros, BYU 9044 (BYU 5000 of Jensen’s usage) is diplodocid, and conclude that it belongs to Supersaurus, making Ultrasauros a junior synonym.

2001 — Curtice and Kenneth (2001) show that the holotype of Dystylosaurus, BYU 4503 (BYU 5750 of Jensen’s usage) is diplodocid, and conclude that it, too, belongs to Supersaurus, making Dystylosaurus another junior synonym.

2003 — Curtice (2003), in a conference abstract, suggests tentatively that Supersaurus (into which he has already sunk Ultrasauros and Dystylosaurus) may itself be synonymous with Barosaurus.

2005 — A team from a the Wyoming Dinosaur Center announce in an SVP abstract and poster (Lovelace et al. 2005) a new specimen WDC DMJ-021 (“Jimbo”), which they refer to Supersaurus vivianae.

McIntosh (2005:73), in revising Barosaurus, is persuaded that Supersaurus is indeed a valid genus rather than merely a large species of Barosaurus. (He mentions “the type specimen, the right scapulocoracoid” — another puzzle piece to help determine which element is the type.)

2008 — The WDC team formally describe their referred Supersaurus specimen WDC DMJ-201 (“Jimbo”), providing a phylogenetic analysis that recovers Supersaurus (based on a compound BYU+WDC taxon) as more closely related to Apatosaurus than to Barosaurus.

2011 — Whitlock’s phylogenetic analysis of diplodocoids recovers Supersaurus as the most basal diplodocine (Whitlock 2011:figure 7), i.e. closer to Barosaurus than to Apatosaurus, but not very close to either.

2015 — Tschopp et al.’s phylogenetic analysis of diplodocoids codes the BYU and WDC Supersaurus individuals as separate OTUs and finds that they emerge as sister taxa (Tschopp et al. 2015:figure 118), corroborating Lovelace et al.’s referral of the WDC specimen to Supersaurus. They recover Supersaurus in a small clade with Australodocus and Dinheirosaurus near the base of diplodocinae: again, closer to Barosaurus than to Apatosaurus, but not very close to either.

2016 — In an SVPCA talk and abstract, Taylor and Wedel (2016) argue that BYU 9024, the large cervical vertebra usually considered to be part of the Dry Mesa Supersaurus, actually belongs to a large Barosaurus. If this is correct, then the concept of Supersaurus requires further revision.

2019 — In a seemingly endless series of blog-posts, Taylor and Wedel consider the history of Supersaurus and co., and the taxonomic implications of the BYU cervical belonging to Barosaurus.

References

Note: this is a unified bibliography for all the posts in the present series. It therefore includes references not cited in this post.

 

Posted by Mike Taylor
Filed in "Ultrasauros", Barosaurus, Dystylosaurus, Supersaurus
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Lovelace et al.’s 2005 poster about the WDC Supersaurus

July 15, 2019

Back in 2005, three years before their paper on the WDC Supersaurus known as Jimbo was published, Lovelace at al. presented their work as a poster at the annual SVP meeting. The abstract for that poster appeared, as usual, in the abstracts book that came as a supplement to JVP 25 issue 3. But the poster itself was never published — which is a shame, as it contains some useful images that didn’t make it into the descriptive paper (Lovelace et al. 2008).

With Dave and Scott’s blessing, here it is! Click through for full resolution, of course.

And here’s the abstract as it appeared in print (Lovelace et al. 2005):

REVISED OSTEOLOGY OF SUPERSAURUS VIVIANAE

LOVELACE, David, HARTMAN, Scott, WAHL, William, Wyoming Dinosaur Center, Thermopolis, WY

A second, and more complete, associated specimen of Supersaurus vivianae (WDC-DMJ021) was discovered in the Morrison Formation of east-central Wyoming in a single sauropod locality. The skeleton provides a more complete picture of the osteology of S. vivianae, including a surprising number of apatosaurine characteristics. The caudals have heart shaped centra that lack a ventral longitudinal hollow, and the rectangular distal neural spines of the anterior caudals are mediolaterally expanded similar to Apatosaurus excelsus. The centra of the anterior caudals are procoelous as in other diplodocids, but the posterior ball is very weakly pronounced. The robusticity of the tibiae and fibulae are intermediate between Apatosaurus and diplodocines. The cervical vertebrae demonstrate classic diplodocine elongation with an elongation index ranging from 4 to 7.5. All 7 of the new cervicals have a centrum length that exceeds 1 meter. Mid-posterior cervicals are semicamellate at mid-centra near the pneumatic foramina. The dorsal vertebrae exhibit a high degree of elaboration on laminae, and extremely rugose pre and postspinal laminae. Costal elements are robust, with complex pneumatic innervations in the rib head. Although unknown in other diplodocids, early reports described pneumatic ribs in an A. excelsus; unfortunately the described specimen is unavailable.

Inclusion of lesser-known North American diplodocids such as Supersaurus, Seismosaurus and Suuwassea in phyolgenetic studies, may provide a framework for better understanding North American diplodocid evolution.

Many thanks to Dave and Scott for permission to share this important poster more widely. (Publish your posters, people! That option didn’t exist in 2005, but it does now!)

References

  • Lovelace, David M., Scott A. Hartman and William R. Wahl. 2005. Revised Osteology of Supersaurus vivanae (SVP poster). Journal of Vertebrate Paleontology 25(3):84A–85A.
  • 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.
Posted by Mike Taylor
Filed in Shiny digital future, Supersaurus, What counts?
8 Comments »

Table of old and new BYU specimen numbers

July 13, 2019

I keep wishing there was a single place out there where I could look up Jensen’s old BYU specimen numbers for Supersaurus, Ultrasaurus and Dystylosaurus elements, and find the modern equivalents, or vice versa. Then I realised there’s no reason not to just make one. So here goes! The first column shows the specimen numbers as used in Jensen (1985), and last column contains Jensen’s own assignments except where noted.

Jensen Element New Notes
5000 posterior dorsal vertebra 9044 holotype of Ultrasauros
5001 scapulocoracoid 9462 referred to Ultrasauros
5002 anterior caudal vertebra 9045 referred initially to Ultrasauros, then Supersaurus [1]
5003 mid-cervical vertebra 9024 referred initially to Ultrasauros, then Supersaurus [2]
5500 left scapulocoracoid [3] 9025 holotype of Supersaurus
5501 right scapulocoracoid [3] 12962 referred to Supersaurus, although found first
5502 sequence of 12 caudals [4] 9084 referred to Supersaurus
5503 right ischium [4] 12946 referred to Supersaurus
5504 two mid-caudal vertebrae [4] ?9077[5] referred to Supersaurus
5750 anterior dorsal vertebra 4503 holotype of Dystylosaurus

By the way, does anyone know why the numbers were changed?

 

Notes

[1] This diplodocid caudal, which is obviously diplodocid based on Jensen’s own illustrations (Jensen 1985:figures 2D,E, 3E), was reassigned to Supersaurus by Curtice (1995).

[2] Jensen (1987:602-603) recognised his own error in referring this cervical to the brachiosaurid taxon Ultrasaurus, based on its bifurcated neural spine. He “provisionally refer[red] it to the Diplodocidae” in the text, but without specifying a genus or species. However in caption to illustrations in the same paper (Jensen 1987:figures 7A, B, 8C) he names the element as Supersaurus vivianae without comment.

[3] Jensen’s (1985) original description describes BYU 5500 (=BYU 9025) as a right scapulocoracoid, implying that BYU 5501 is the left; but this is incorrect.

[4] Jensen’s original Supersaurus/Ultrasaurus/Dystylosaurus description is confusing and contradictory in his assignment of specimen numbers. In his systematic palaeontology section, Jensen (1985:701) says that BYU 5502 is the ischium, BYU 5503 is the pair of mid-caudals and BYU 5504 is the sequence of 12 caudals. But the description on the same page contradicts this, giving the assignments shown here. The casting vote goes to the caption of Jensen (1985:figure 7), in which part A illustrates BYU 5503, the ischium; and parts C, D and D1 illustrate caudals that do not appear to be part of sequence of twelve.

[5] Curtice et al. (2001:36) say “An additional caudal vertebra (BYU 9077) is referred to (and figured as) Supersaurus in the text of Jensen (1985)”. This probably refers to Jensen 1985:figure 7:C, D, D1, which are captioned as follows: “C, BYU 5033, Supersaurus vivianae, referred specimen, ischium [sic]. D, D1, BYU 5504, Supersaurus vivianae, referred specimen, caudal vertebra.” Since part C of the figure is clearly a caudal vertebra, and since BYU 5503 is also illustrated as an ischium in part A of the same figure(!), it seems most likely that the caudals in part C and parts D and D1 of this figure are the pair described as BYU 5044 on pages 701-704.

 

Commentary (i.e. pointless whining)

For all his innovations in skeletal mounting and his amazing discoveries in the field, Jensen was evidently a markedly careless palaeontologist in many respects, and his contempt for specimen numbers in particular has created enormous problems. Even within a single page — even within a single figure caption — he was capable of contradicting himself on the numbers assigned to specimens. Most illustrations don’t give specimen numbers at all. And while in many respects the later work of Curtice et al. (1996) and Curtice and Stadtman (2001) is much better, they did the world no favours by simply switching to the new specimen numbers without providing a definitive key like the one I am trying to build here. It’s pretty silly that, 23 years on, we are reduced to guesswork like note 5.

 

References

  • Curtice, Brian D. 1995. A description of the anterior caudal vertebrae of Supersaurus vivianae. Journal of Vertebrate Paleontology 15(3):25A.
  • 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.
Posted by Mike Taylor
Filed in "Ultrasauros", BYU Museum of Paleontology, Dystylosaurus, Supersaurus
11 Comments »

Bonus post: Supersaurus before Ultrasaurus!

July 11, 2019

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

 

Posted by Mike Taylor
Filed in brachiosaurids, coracoid, field photos, math, paleontologists behaving badly, scapula, Shiny digital past, size, Supersaurus, timely
24 Comments »

Supersaurus, Ultrasaurus and Dystylosaurus in 2019, part 8: we finally get to Ultrasauros!

July 9, 2019

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

 

 

Posted by Mike Taylor
Filed in "Ultrasauros", BYU Museum of Paleontology, coracoid, diplodocids, dorsal, Dystylosaurus, museums, mystery vertebra, North American Museum of Ancient Life, scapula, Supersaurus
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Supersaurus, Ultrasaurus and Dystylosaurus in 2019, part 7: at last, Dystylosaurus has its day!

July 8, 2019

Poor Dystylosaurus. Always the bridesmaid. No-one seems to care much about it, yet the one and only vertebra that bears that name is the single most diagnostic elements out of all the individual bones that have been assigned to Supersaurus over the years.

A nice drawing of the “Dystylosaurus” dorsal vertebra in anterior and right lateral views. It’s probably Tracey Ford’s work (awaiting confirmation), from the PaleoFile page on Supersaurus.

Unfortunately, we weren’t able to learn a whole ton about this vertebra on the Sauropocalypse visit. We did see it, but it was flat on its back on a shelf not much taller than the anteroposterior length of the bone itself, so we weren’t able to get a good look at it in anything but dorsal and ventral views. If we’d had more time to get things arranged, I’m sure the BYU people would have been happy to get it down from the shelf for us, but we simply had so much to do in their collections that time was never made for it.

BYU 4503, the holotype and only element of Dystylosaurus edwini, an anterior dorsal vertebra. here seen in approximately dorsal view with anterior to the top. Matt Wedel for scale.

Matt actually got some rather better photos a few years ago, though (based on his comment on that post), there are probably no more than the couple in that old blog-post. (By the way, notice how very different the colour of the bone appears in Matt’s old photos from how it appears in my more recent one above.)

Why do I say so confidently that the Dystylosaurus vertebra is diagnosable? Because it has a whole suite of characters that tell us it’s an anterior dorsal vertebra from a diplodocid (dual centroprezygapophyseal laminae, anteroposteriorly compressed spine composed primarily of spinozygapophyseal rather than spinodiapophyseal laminae, drooping transverse processes), yet two features of the spine are never seen in such vertebrae: the spine is wholly unsplit without even a hint of bifurcation, even featuring macronarian-like lateral apices; and it’s hollow inside rather than being constructed from intersecting plates of bone. (You can see the internal hollow in the photo above.)

So what happens to its genus name given the doubts about Supersaurus‘s diagnosability? The general trend of comments on these posts has been that Supersaurus should stand or fall on its holotype, and I am inclined to agree that parachuting in the Dystylosaurus vertebra or Jimbo as a neotype to save the name would be a mistake. For one thing, despite its numerous appearances in kids’ books, the name Supersaurus is not that important in the technical literature: for example, no-one has named a clade Supersaurinae or similar. For another, the holotypic scapulocoracoid BYU 9025 is only questionably undiagnosable. There would always be the possibility that if someone nominated a neotype and wrestled it through the ICZN petition process, someone else would find a good solid way to diagnose the original holotype. That would be embarrassing.

The rare ventral-ish view of the Dystylosaurus dorsal vertebra BYU 4503. Sorry it’s not better. I do have 93 photos of it in this shelf, all of them individually pretty terrible, which I took in the forlorn hope that one day we’ll get photogrammetry software simple enough and clever enough to make some kind of model out of them.

So I think we need to simply accept that the name Dystylosaurus, while perfectly diagnosable based on its holotype and only specimen, is destined to remain a junior synonym for as long as Supersaurus is considered taxonomically valid.

But it does leave Dystylosaurus in a bit of a quantum superposition. When Supersaurus is considered diagnosable, it ceases to exist, like a cat in a box. When Supersaurus is considered undiagnosable, it pops back into existence, like … well, a cat in a box. It’s an unsatisfactory kind of existence, but I think that’s the way it has to be.

So Dystylosaurus has its day — and it ends up being disappointing. Despite being perfectly diagnosable, it’s dependent for its validity on our assessment of other taxa. Some fossils just can’t catch a break.

Posted by Mike Taylor
Filed in BYU Museum of Paleontology, diplodocids, dorsal, Dystylosaurus, museums, mystery vertebra, Nomenclature, Supersaurus
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Supersaurus, Ultrasaurus and Dystylosaurus in 2019, part 6: what happens to Supersaurus now?

July 2, 2019

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

 

Posted by Mike Taylor
Filed in cervical, coracoid, diplodocids, dorsal, Dystylosaurus, mystery vertebra, Nomenclature, North American Museum of Ancient Life, Sauropocalypse 2016, scapula, Supersaurus
26 Comments »

Supersaurus, Ultrasaurus and Dystylosaurus in 2019, part 5: what actually is Supersaurus?

June 25, 2019

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 Barosaurus–Diplodocus 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 Diplodocus–Barosaurus 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

 

Posted by Mike Taylor
Filed in 3D models, coracoid, diplodocids, photogrammetry, scapula, Supersaurus, Thinking it through
20 Comments »
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