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When sensory nerves from the thigh end up in the feet

July 23, 2019

The image I put together explaining the new discovery. Modified from Staples et al. (2019: fig. 6).

Today sees the publication of a new paper, “Cutaneous branch of the obturator nerve extending to the medial ankle and foot: a report of two cadaveric cases,” by Brittany Staples, Edward Ennedy, Tae Kim, Steven Nguyen, Andrew Shore, Thomas Vu, Jonathan Labovitz, and yours truly. I’m excited for two reasons: first, the paper reports some genuinely new human gross anatomy, which happens surprisingly often but still isn’t an everyday occurrence, and second, the first six authors are my former students. This isn’t my discovery, it’s theirs. But I’m still going to yap about it.

When the obturator nerve won’t stay in its lane

Your skin is innervated by cutaneous nerves, which relay sensations of touch, pressure, vibration, temperature, and pain to your central nervous system, and carry autonomic (involuntary) fibers to your sweat and sebaceous glands and the arrector pili muscles that raise and lower your hairs (as when we get goosebumps). Every inch of your skin lies in the domain of one cutaneous nerve or another. Known boundaries between cutaneous branches of different nerves are approximate, both because they vary from person to person, and because the territories of the nerves themselves interdigitate and overlap at very fine scales. That said, aside from complex areas where the domains of multiple nerves intersect (like the groin), most body regions get their cutaneous innervation from just one nerve.

The obturator nerve arises from the spinal levels of the 2nd-4th lumbar vertebrae (L2-L4), exits the pelvis through the obturator canal behind the superior ramus of the pubis, and innervates the adductor muscles of the medial compartment of the thigh. The cutaneous branch of the obturator nerve typically innervates a variable but limited patch of skin on the inner thigh. Here’s a diagram from Gray’s Anatomy, 40th edition, showing the common cutaneous distribution of the obturator nerve (Standring et al. 2008 fig. 79.17, modified):

In rare cases, however, the obturator nerve doesn’t stay in the thigh. I was teaching in the gross anatomy lab in the fall of 2013 when one of our podiatry students, Brittany Staples, called me over to her table. We were skinning the thigh and leg that day, and in her assigned cadaver, Brittany had found a nerve from the medial thigh running all the way down to the inner side of the ankle and foot.

I didn’t immediately freak out, because everyone has a nerve from the thigh running down to the inner side of the ankle and foot: the saphenous branch of the femoral nerve, which comes out of the anterior thigh (also highlighted in the above image). But when we traced back Brittany’s nerve, it wasn’t coming from the femoral nerve. Instead, it was coming from the anterior division of the obturator nerve, right behind the adductor longus muscle (when people do the splits, this is the muscle that makes a visible ridge from the inner thigh to the groin). We carefully cleaned and photographed the nerve, and then we hit the books. Our first question: was this a known variation, or had Brittany discovered something new in the annals of human anatomy?

Standing on the shoulders of giants

Virtually all introductory anatomy textbooks show the obturator nerve only going to the thigh. But a little digging turned up Bouaziz et al. (2002), which in turn reproduced a figure from Rouvière and Delmas (1973), a French textbook, which showed the obturator nerve passing the knee and innervating part of the calf. That was at least an advance on what we knew starting out. We found a similar written description in Sunderland (1968).

Bouaziz et al. (2002: fig. 1)

Then we discovered Bardeen (1906), a magnificent and magisterial work 130 pages in length. Titled, “Development and variation of the nerves and the musculature of the inferior extremity and of the neighboring regions of the trunk in man”, the paper delivers on its impressive title. Bardeen (1906: 285 and 317) reported than in 22 out of 80 cadavers, the cutaneous branch of the obturator nerve (CBO) reached the knee; in 10 of those cases it could be traced at least to the middle third of the calf; and in one case it reached “nearly to ankle”. Bardeen also commented on the difficulty of tracing out the limits of this tiny nerve (p. 285):

“How constant the cutaneous branch of the obturator may be I have been unable satisfactorily to determine. Students dissecting frequently fail to find it. Owing to the fact that this may often be due to its small size the negative records cannot safely be used in making up statistics.”

All of us on the paper can back up Bardeen’s comments here: by the time they reach the skin, cutaneous nerves might be as big around as a pencil lead, or a strand of dental floss, or a human hair, but they won’t be much bigger. Sometimes they run just under the skin, sometimes down in the subcutaneous fat and fascia (with vanishingly small extensions spidering out to the underside of the skin), always variable in their courses and often devilishly hard to find, preserve, and trace.

If there is a prior report in the literature of a CBO passing the ankle, we haven’t found it, and neither have the numerous podiatric physicians who commented on the manuscript before we submitted, nor the reviewers and editors of the Journal of Foot & Ankle Surgery. I feel pretty safe saying that this is truly new (and if you know otherwise, please let me know in the comments!).

The second case, and the long silence

Every year since 2013, I’ve warned our medical and podiatric students to be on the lookout for anomalously long branches of the obturator nerve. The very next year, a group of summer anatomy students found a second example (they’re authors 2-6 on the paper). Since then, nada, in over 200 more bodies as of this summer. Either we got crazy lucky to find two examples in back to back years, or long CBOs are more common than we think, just really hard to find and identify. More on that in a minute.

A quick aside: we didn’t deliberately hold up the paper while we were looking for more examples, we’ve all just been busy. Brittany and the other student authors were occupied with passing med school and their board exams, surviving clinical rotations, and applying to residency programs. I’m happy to say “were occupied” with all those things because they’re all graduated now, and in residency training. Anyway, that’s why the paper had a 5-year gestation: med school doesn’t leave a lot of time for research and writing. Kudos to Brittany for giving all of us regular kicks to keep things moving along. In every sense, the paper would not exist without her skill and dedication.

So what’s going on here?

There are two sides to this: what happened to produce the variants we found in 2013 and 2014, and why variants like that escaped detection for so long, and I’ll tackle them in that order.

We found both of the long CBOs in the territory normally occupied by the saphenous branch of the femoral nerve. The saphenous nerve is so named because it runs along the great saphenous vein, the major superficial vein of the medial leg and thigh. Sometimes the saphenous nerve has only a single main trunk, but more commonly it splits into two parallel branches, one on either side of the saphenous vein, as illustrated here by Wilmot and Evans (2013: fig. 3):

In both of our cases, the saphenous branch of the femoral nerve was present, but it only had one branch, in front of the big vein, and the long CBO ran behind the vein, in the place usually occupied by the posterior branch of the saphenous nerve. In effect, the posterior part of the saphenous branch of the femoral nerve had been replaced by a sort of saphenous branch of the obturator nerve. This has interesting implications.

Suppose you were a surgeon, harvesting the distal portion of the saphenous vein for a coronary artery bypass graft, and you saw two nerves accompanying the vein, one in front and one behind. You would probably assume that both branches arose from the femoral nerve, because that is what happens most commonly. But if the posterior branch actually came from the obturator nerve, you’d have no way of knowing that, without tracing the nerve back to its origin in the inner thigh. The watchwords in surgery these days are “minimally invasive” and “patient outcomes” — smaller openings in the body mean less pain, fewer complications, faster recoveries, and happier patients. So surgeons aren’t going to flay patients open from ankle to groin just to chase down a nerve that might be coming from the normal place after all.

If you only get to look inside the box, these two things look the same.

We suspect that long CBOs may be fairly common, just hard to recognize, because who is going to find them? Medical students dissecting human cadavers have the opportunity to trace long cutaneous nerves back to their origins, but since it’s the students’ first time cutting, they usually haven’t yet developed the experience to recognize weird versions of tiny nerves, nor the skill to preserve them. Surgeons have the experience and the skill, but not the opportunity, because they can’t go around filleting their patients to see where all the nerves come from. So long CBOs probably fall into a perceptual blind spot, in which almost no-one who cuts on human bodies has both the opportunity to find them, and the skill to preserve them — my former students excepted (he said with no small helping of pride).

That’s pretty darned interesting, and it makes me wonder what other perceptual blind spots are out there, in both anatomy and paleontology. I know of at least one: the true nature and extent of the fluid-filled interstitial tissues that pervade our bodies (and those of all other vertebrates at least) were not fully appreciated until just last year, because the first step in the production of most histological slides is to dehydrate the tissues, which collapses the fluid-filled spaces and makes the interstitium look like regular connective tissue (Benias et al. 2018). That is a spooky kind of observer effect, and it makes me wonder what else we’re missing because of the ways we choose — or are constrained — to look.

What next?

What’s the fallout from this study? For me, two things. First — obviously — we’re going to keep looking for more examples of long CBOs, and for other similar cases in which one nerve may have been replaced by its neighbor. This is more than trivia. Knowing which nerves to expect and where to find them is important, not only for surgeons but also for anaesthetists and pain management physicians doing nerve blocks. The decks may be stacked against med students for some of these discoveries, but clearly “difficult” does not mean “impossible” or I’d have nothing to write about. Lightning has already struck twice, so I’ll keep flying this particular kite.

Second, this case, a few other odd things we’ve found in the lab over the years, and other recently-reported discoveries in human anatomy have caused me to wonder: could we formulate predictive maxims to help guide future discoveries in human anatomy, or in anatomy full stop? I think so, and provided my abstract is accepted, I’ll be presenting on that topic at SVPCA in a couple of months. More on that in due time.

Finally — and this cannot be overstated — without the keen eyes, skilled hands, sharp minds, and hard work of the student authors, there would be no discovery and no paper. So congratulations to Brittany, Edward, Tae, Steven, Andrew, and Thomas. Or as I’m happy to address them now, Drs. Staples, Ennedy, Kim, Nguyen, Shore, and Vu. Y’all done good. Keep it up.

References

  • Bardeen, C.R. 1906. Development and variation of the nerves and the musculature of the inferior extremity and of the neighboring regions of the trunk in man. Developmental Dynamics 6(1):259-390.
  • Benias, P.C., Wells, R.G., Sackey-Aboagye, B., Klavan, H., Reidy, J., Buonocore, D., Miranda, M., Kornacki, S., Wayne, M., Carr-Locke, D.L. and Theise, N.D. 2018. Structure and distribution of an unrecognized interstitium in human tissues. Scientific Reports, 8:4947.
  • Bouaziz, H., Vial, F., Jochum, D., Macalou, D., Heck, M., Meuret, P., Braun, M., and Laxenaire, M.C. 2002. An evaluation of the cutaneous distribution after obturator nerve block. Anesthesia & Analgesia 94(2):445-449.
  • Rouvière, H., and Delmas, A. 1973. Anatomie humaine, descriptive, topographique et fonctionnelle: tome 3—membres-système nerveux central, ed 11, Masson, Paris.
  • Standring, S. (ed.) 2008. Gray’s Anatomy: The Anatomical Basis of Clinical Practice, 41st ed, Elsevier Health Sciences, London.
  • Staples, B., Ennedy, E., Kim, T., Nguyen, S., Shore, A., Vu, T., Labovitz, J., and Wedel, M. 2019. Cutaneous branch of the obturator nerve extending to the medial ankle and foot: a report of two cadaveric cases. Journal of Foot & Ankle Surgery, advance online publication.
  • Sunderland, S. 1968. Nerves and Nerve Injuries. Churchill Livingstone, Edinburgh.
  • Wilmot, V.V., and Evans, D.J.R. 2013. Categorizing the distribution of the saphenous nerve in relation to the great saphenous vein. Clinical Anatomy 26(4):531-536.
Posted by Matt Wedel
Filed in human anatomy, nervous system
16 Comments »

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
22 Comments »

Don’t touch the casts! Touch the bones!

July 16, 2019

Here’s a piece of signage from the wonderful Dinosaur National Monument, which we visited on the 2016 Sauropocalypse.

And in close-up:

This is the first and only time I’ve been encouraged to touch real dinosaur bones on the basis that a cast of them was too fragile.

Happily, we did have some great experiences with the actual fossils. Here is Matt, inspecting part of the wall, while our host Dan Chure documents the moment and the cotyle of a convenient ?Camarasaurus cervical acts as a receptacle for the cameras not in use at that point.

Above us, on the balcony, tourists wonder at such astonishingly massive creatures, and their ability to navigate a wall of fossils.

Posted by Mike Taylor
Filed in Dinosaur National Monument, goofy
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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?
2 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 »

Cabinet of curiosities: Jessie Atterholt’s office

July 10, 2019

My friend and frequent collaborator Jessie Atterholt has her office in the next building over from mine. When you walk in, you see something that looks approximately like this. Not exactly like this, because I took these photos in February and she’s changed a few things (and I’m rubbish about getting stuff posted in a timely fashion).

The last time I showed an office full of amazing stuff like this, it was Peter Dodson’s. It will come as no surprise that Jessie was Peter’s student at UPenn before she went to Berkeley for her PhD.

The far case holds mostly books and skulls. Dr. A has her own plastination setup for making preserved organs and organisms, and the snake on the second shelf here is one that she prepped herself. One side of the snake still has the skin on, the other half has been skinned to show the muscles. This is crunch week for me so I don’t have time to ID all of the stuff, but alert readers should have no problem spotting some digitally-resurrected Haplocanthosaurus bits.

Mostly skulls on the middle rack. The sirenian skull on the second shelf and the cave bear on the fourth are both casts, but almost everything else is real bone. The bighorn sheep on the middle shelf is a natural mummy.

Here’s a close-up of the top shelf. Other than some 3D-printed human skull bones sitting in front of the brain slice on the left, everything here is real bone, including the lion, baboon, and human skulls, and the giraffe cervicals winding across the top. Jessie’s been collecting since she was a kid and the African megafauna are gifts from a globe-trotting family friend.

The upper shelves here have quite a few of Jessie’s plastinated specimens, both whole organisms and things like hearts and kidneys from various critters.

A close-up of some of Jessie’s coolest anatomical preparations. In back is an internal cast of the lungs and bronchial tree of a cat. The baby rattlesnake died after eating a proportionally gigantic lizard — I was dumb and forgot to flip the snake over to show the lizard inside, plastinated along with its predator. The ground squirrel on the right is another half-fleshed, half-skinned plastinate, and the mouse up front is a classic dissection presentation, preserved forever through plastination.

I’ve heard it said that the difference between a collector and a hoarder is curation. As someone who definitely lurks more on the hoarder end of that spectrum (to paraphrase Dave Barry, if you could see my office you’d be blinded or driven insane), I’m pretty darned jealous of both the breadth of Jessie’s collection, and the skill and taste with which it is displayed. She’s featured some of these specimens on her Instagram, which I strongly recommend.

Posted by Matt Wedel
Filed in anatomical preparations, cabinet of curiosities, caudal, Haplocanthosaurus, stinkin' appendicular elements, stinkin' every thing that's not a sauropod, stinkin' snakes, stinkin' heads, stinkin' mammals
4 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
13 Comments »

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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James Herrmann’s dinosaur sculptures for the Cincinnati Museum Center

July 7, 2019

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

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

From behind.

And from the front.

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

Here’s a convincingly chunky Allosaurus.

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

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

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

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

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

One more, a life-size bust of Galeamopus.

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

Posted by Matt Wedel
Filed in Art, diplodocids, Galeamopus, James Herrmann, life restorations, stinkin' heads, stinkin' theropods
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