It’s time to revisit everyone’s favourite trio of apocryphal super-sized sauropods! (Yes, we’ve talked about this before, but only very briefly, and that was nearly eleven years ago. Things have moved on since then.)

John Sibbick’s classic artwork showing three giant sauropods, including two of Jensen’s three. On the left is Seismosaurus Gillette 1991, which is not directly relevant to today’s post. In the middle is the brachiosaur Ultrasaurus, and on the right the diplodocid Supersaurus. Poor, unloved Dystylosaurus doesn’t get a look-in — perhaps because this was drawn before that name had been announced?

Here’s the story so far …

1. Jensen’s discoveries

In a series of expeditions beginning in April 1972, following a tip from uranium prospectors Eddie and Vivian Jones, Jim Jensen found numerous massive sauropod fossils in the Dry Mesa quarry, southwest Colorado. The Supersaurus pelvis at least was still in the ground as late as August 1972 (George 1973b:51–52) and the excavations continued into 1982 (Jensen 1985:697).

Eschewing such pedestrian venues as Science, Nature or indeed the Journal of Vertebrate Paleontology, Jensen first told the world about these finds in the popular press. The oldest published work I have that mentions them is Jean George’s (1973b) piece in Reader’s Digest, condensed from the same author’s piece in the Denver Post’s Empire Magazine earlier that year (George 1973a), which I have not been able to obtain.

“‘Supersaurus,’ as we shall call him, now awaits an official name and taxonomic classification”, wrote George (1973b:53) — but the piece does not mention the names “Ultrasaurus” or “Dystylosaurus” and I’ve not been able to determine when those informal names became known to the world. (Can anyone help?) We do know that Jensen was informally using the name “Ultrasaurus” as early as 1979 (Curtice et al. 1996:87).

Anyway, for reasons that have never been very clear, Jensen concluded that the remains represented not one, not two, but three gigantic new genera: a diplodocid, which he named “Supersaurus”; a brachiosaurid, which he named “Ultrasaurus”; and an unidentifiable which he named “Dystylosaurus”. All these names were informal at this point, like “Angloposeidon” and “The Archbishop”.

2. Kim’s accidental Ultrasaurus

After Jensen had been using these names informally for some years, Kim (1983) named an indeterminate Korean sauropod as Ultrasaurus tabriensis. Based on the abstract (the only part of the paper in English, apart from the figure captions), Kim was aware of Jensen’s dinosaurs: “Judging by the large size of the ulna the animal may belong to the sauropod dinosaur, which is much bigger than Supersaurus. A new name Ultrasaurus tabriensis is proposed for the convenience of the further study.” While this does not quite go so far as to say that Kim considered the ulna to belong to the same genus as Jensen’s brachiosaur, it seems unlikely that he was aware of Supersaurus but not of Ultrasaurus, and landed independently on the latter name by coincidence.

Either way, in naming his species, Kim inadvertently preoccupied Jensen’s chosen genus name, with conseqences that we shall see below. By all accounts, the material the Kim described is in any case indeterminate, and the genus is generally considered a nomen nudum (e.g. Olshevsky 1991:139, Glut 1997:1001).

Kim 1983, plate 1, parts 1-3, illustrating the proximal portion of the huge “ulna” that the name Ultrasaurus tabriensis was founded on. As is apparent, this is actually the proximal end of a humerus, meaning that the animal is rather less large than Kim supposed — although the 42 cm width across the proximal end is still nothing to be sniffed at. It is about 71% the width of the 59 cm-wide humerus of the Giraffatitan brancai paralectotype MB.R.2181 (previously HMN SII).

Two years after this, and presumably unaware of Kim’s paper or incorrectly assuming his informal use of the name “Ultrasaurus” gave him priority, Jensen published a formal account of his finds, naming them (Jensen 1985). Unfortunately, while the paper does contain formal nomenclatural acts that are valid according to the rules of the ICZN, Jensen did not explain his reasoning for the creation of the new genera, and his selection of type material was problematic, as we shall see below. Also, the specimen numbers that he used have been superseded — I do not know why, but my guess would be that he re-used numbers that were already in use for other specimens, so his own material had to be given new numbers.

3. Jensen’s three sauropods

The following three genera (with their type species) were named, in this order:

1. Supersaurus vivianae, based on the holotype BYU 9025 (BYU 5500 of his usage), a scapulocoracoid measuring 2.44 m in length. To this, he referred an even larger scapulocoracoid whose length he gives as 2.70 m (though Curtice and Stadtman 2002:39 found that this length to be due to optimistic reconstruction); an ischium; either one or two mid-caudal vertebrae (his paper contradicts itself on this); and a sequence of 12 articulated caudal vertebrae. Unfortunately, Jensen’s use of specimen numbers for most of these referred elements is inconsistent, but he is at least consistent in referring to the second scapulocoracoid as BYU 5501.

Supersaurus vivianae holotype scapulocoracoid BYU 9025, photographed at the North American Museum of Natural Life. The exhibit text reads: “Supersaurus scapula and coracoid. This is the actual Supersaurus bone that the world saw when the announcement was made of the new animal’s discovery in 1972. The scapula lay in the ground for five more years, waiting for the collection of other fossils that lay in the path of excavation. The flatness of the bone presented a challenge to “Dinosaur Jim” Jensen, who had to figure out a way to get the bone safely out of the ground. He finally accomplished this by cutting the scapula into three pieces. In 1988, Cliff Miles, Brian Versey and Clark Miles prepared the bone for study. It is still one of the largest dinosaur bones known in the world. Specimen on load from Brigham Young University’s Earth Science Museum. Late Jurassic/Early Cretaceous (about 144 million years ago)

2. Ultrasaurus macintoshi, based on the holotype BYU 9044 (BYU 5000 of his usage), a dorsal vertebra measuring 1.33 m in height. To this, he referred BYU 9462 (BYU 5001 of his usage), a scapulocoracoid measuring 2.7 m in length; BYU 9024 (BYU 5003 of his usage), a huge cervical vertebra; and an anterior caudal vertebra.

Ultrasaurus macintoshi holotype dorsal vertebra BYU 9044, photographed at the North American Museum of Natural Life. (It’s incredibly hard to photograph well because it’s behind reflective glass.)

3. Dystylosaurus edwini, based on the holotype BYU 4503 (BYU 5750 of his usage), a dorsal vertebra. He did not refer any other material to this taxon, and considered it “Family indeterminate” commenting that it “no doubt represents a new sauropod family”. Poor Dystylosaurus has always been the unloved member of this group, and pretty much ignored in the literature aside from the Curtice & Stadtman (2002) synonymisation paper discussed below.

Dystylosaurus edwini holotype BYU 4503, a diplodocoid anterior dorsal vertebra.

In a subsequent paper, Jensen (1987:600–602) removed the big cervical BYU 9024 (BYU 5003 of his usage) from Ultrasauros and reassigned it to Diplodocidae. The text of this paper never refers it to Supersaurus vivianae in particular, but it is illustrated and captioned as belonging to that taxon (Jensen 1987:figures 7A-B, 8C), and this assignment is generally assumed to have been meant.

When Jensen became aware of Kim’s (1983) preoccupation of the name Ultrasaurus, he recognised that his own genus needed a new name. At his suggestion, Olshevsky (1991) erected the replacement name Ultrasauros (with a single-letter spelling difference) for Jensen’s taxon based on the dorsal vertebra BYU 9044. We will use this revised spelling hereon, and the taxon Ultrasaurus Kim 1983 is of no further interest to this story.

The relevant extract from Olshevsky (1991:139).

4. Curtice’s synonymies

This was how things stood, with Jensen’s assignment of the material to his three new genera standing unchallenged, until Brian Curtice came on the scene in the mid 1990s. In a series of three publications (two papers, one abstract), he first synonymised Ultrasauros with Supersaurus, then Dystylosaurus also with Supersaurus, and finally (tentatively) Supersaurus itself with Barosarus. If Curtice’s suggestions were all correct, then there were no new sauropods from Jensen’s work in the the Dry Mesa quarry, just a lot of Barosaurus material.

Was he right? We’ll now consider each of the three publications in turn.

First, Ultrasauros. Jensen had always considered this genus to be a brachiosaurid due to the morphology of the scapulocoracoid BYU 9462 — and indeed this element does seem to be brachiosaurid. Unfortunately, he did not found the taxon on this element, but on the dorsal vertebra BYU 9044. Curtice et al. (1996) re-examined this element, and argued convincingly that it was not an anterior dorsal from a brachiosaurid, as Jensen had thought, but a posterior dorsal from a diplodocid. Since its neural spine morphology matches that of the first preserved sacral spine (S2) of the Supersaurus sacrum, and since it was found between the two Supersaurus scapulocoracoids, Curtice et al. (1996:94) considered BYU 9044 to be a vertebra of Supersaurus (belonging to the holotype individual), and therefore concluded that Ultrasauros was a junior subjective synonym of Supersaurus. They inferred that the referred Ultrasauros scapulocoracoid BYU 9462 therefore did not belong to the same species as the type, since it was brachiosaurid, and referred it to Brachiosaurus sp.

We consider all of Curtice et al.’s (1996) arguments well-founded and convincing, and agree with their conclusions. As a result, both spellings of Jensen’s brachiosaurid genus are now discarded: Ultrasaurus as a nomen dubium, and Ultrasauros as a junior synonym.

Curtice et al. (1996:figure 2). “Uncrushed” Supersaurus vivianae caudal dorsal, BYU 9044, right lateral view.

A few years later, Curtice and Stadtman (2002) took aim at Dystylosaurus. Jensen had argued that it was unique because of the paired centroprezygapophyseal laminae that supported each prezygapophysis from below — and it was from this feature than the genus took its name. But Curtice and Stadtman pointed out that this supposedly unique feature is in fact almost ubiquitous in diplodocids. Because it, too, was found between the two Supersaurus scapulae (close to the Ultrasaurus dorsal), Curtice and Stadtman referred it, too, to Supersaurus, thereby collapsing all three of Jensen’s taxa into one. This argument, too, is well supported and has been generally accepted.

Finally, in a sole-authored abstract, Curtice (2003) hedged about whether he considered Supersaurus to be Barosaurus. I will quote directly, as the line of reasoning is vague and difficult to summarise:

The question of is Supersaurus truly a distinct genus from Barosaurus is now testable. The former Dystylosaurus dorsal vertebra provides an autapomorphy for Supersaurus, that being a strongly reduced bifid neural spine on dorsal four. This loss of bifidity is important for in all other diplodocids the neural spine is still deeply bifurcated on dorsal four. Only Barosaurus has a reduction in cleft depth that far forward in the dorsal column. Supersaurus has all but lost the cleft, more closely resembling the sixth dorsal vertebra of Barosaurus than the fourth.

It is disappointing that this abstract never became a more rigorously argued paper, because the conclusion here is highly equivocal. Curtice appears to be saying that Supersaurus is distinct from Barosaurus — but only on the basis of bifidity reducing two vertebrae more anteriorly in Supersaurus. In other words, he seems to be suggesting that the two taxa are indisinguishable aside from this rather minor difference.

At any rate, this speculation in a conference abstract has generally been ignored, and Supersaurus considered a valid and distinct genus.

5. Jimbo the WDC Supersaurus

In 2008, Lovelace et al. (2008, duh) described WDC DMJ-021, a new specimen of Supersaurus vivianae at the Wyoming Dinosaur Center that is known informally as “Jimbo”. (Confusingly, they refer to the Supersaurus holotype scapulocoracoid by yet a third specimen number, BYU 12962; but we will continue to use BYU 9025 here. It is possible that BYU 12962 is the revised specimen number of the referred scapulocoracoid, not the holotype.)

Lovelace et al. (2008) did not justify in detail their referral of Jimbo to Supersaurus. The closest the come is this brief passage on page 529–530:

While a scapula is not known for WDC DMJ-021, other elements are identical to axial elements referred to the type individual of Supersaurus. Referral of all material is supported by relative position within their respective quarries (Curtice and Stadtman 2001; Lovelace 2006), size of the skeletal elements, and congruence of phylogenetically significant diplodocid characters between the scapula and referred material.

All of this is kind of weaselly. What it amounts to is this: vertebrae are “identical” to those referred to the BYU Supersaurus (but not really, as we’ll see), and the elements are really big, and the Supersaurus holoype scap comes out in about the same place as Jimbo in a phylogenetic analysis if you code them up separately. This is weak sauce, and I would really have liked to see a much more explicit “Jimbo shares synapomorphies X, Y and Z with BYU Supersaurus” section.

Among the ways in which the justification for this assignment disappoints is that the presacrals that are described as “identical” to the BYU elements are not at all well preserved (Lovelace et al. 2008:figures 3D–E, 4A, 5A): in particular C13, presumably the best preserved cervicals as it is the only one illustrated, is missing the condyle, prezygapophyses and neural spine. It’s not possible to be sure in light of the small monochrome illustrations in the paper, but it does not seem likely that these elements can be reliably assessed as identical to the BYU cervical.

Lovelace et al. (2008:figure 3). Lateral views of cervical vertebrae from A, Diplodocus carnegii (Hatcher 1901); B, Barosaurus lentus (Lull 1919); C, Apatosaurus louisae (Gilmore 1936); D and E, Supersaurus vivianae; demonstrating pneumatic modifications of centra. Supersaurus has the least amount of modification with minimal size for pneumatopores. Internal structure is similar to that seen in other diplodocids (Janensch, 1947). Left lateral view of Cv.13 (D, missing the condyle, prezygapophyses and neural spine; length of incomplete centra 94cm). E, cross section through Cv.11, 5cm posterior of the diapophysis.

The big surprise in the Jimbo paper is that in the phylogenetic analysis (Lovelace et al. 2008:figure 14), the compound BYU+WDC Supersaurus is recovered as an apatosaurine, the sister taxon to Apatosaurus, rather than as a diplodocine as had been assumed in previous studies due to its resemblance to the diplodocine Barosaurus.

The huge specimen-level phylogenetic analysis of diplodocoids by Tschopp et al. (2015) corroborated Lovelace et al’s (2008) referral of the WDC specimen to Supersaurus vivianae, as the two species were sister groups in all most parsimonious trees, with quite strong character support (Tschopp et al. 2015:187). But it placed the Supersaurus clade at the base of Diplodocinae, not within Apatosaurinae as Lovelace et al. (2008) had found.

This, then, was the state of play when Matt and I started to work on Supersaurus during the 2016 Sauropocalypse: Ultrasauros and Dystylosaurus had both been sunk into Supersaurus, and the WDC specimen had been referred to the same species.

Next time, we’ll look what Matt and I found in Utah, and what we think it means for Supersaurus and its friends.

 

References

  • Curtice, Brian D. 2003. Two genera down, one to go? The potential synonomy [sic] of Supersaurus with Barosaurus. Southwest Paleontological Symposium 2003, Guide to Presentations. Mesa Southwest Museum, January 25 2003. Unpaginated.
  • Curtice, Brian D. and Kenneth L. Stadtman. 2001. The demise of Dystylosaurus edwini and a revision of Supersaurus vivianae. Western Association of Vertebrate Paleontologists and Mesa Southwest Museum and Southwest Paleontologists Symposium, Bulletin 8:33-40.
  • Curtice, Brian D., Kenneth L. Stadtman and Linda J. Curtice. 1996. A reassessment of Ultrasauros macintoshi (Jensen, 1985). M. Morales (ed.), “The continental Jurassic”. Museum of Northern Arizona Bulletin 60:87–95.
  • George, Jean. 1973a. Supersaurus, the biggest brute ever. Denver Post, Empire Magazine. May 13, 1973.
  • George, Jean. 1973b. Supersaurus, the biggest brute ever. Reader’s Digest (June 1973):51–56.
  • Glut, Donald F. 1997. Dinosaurs: the Encyclopedia. McFarland & Company Inc., Jefferson. 1076 pp.
  • Jensen, James A. 1985. Three new sauropod dinosaurs from the Upper Jurassic of Colorado. Great Basin Naturalist 45(4):697–709.
  • Jensen, James A. 1987. New brachiosaur material from the Late Jurassic of Utah and Colorado. Great Basin Naturalist 47(4):592–608.
  • Kim, Hang-mook. 1983. Cretaceous dinosaurs from South Korea. Journal of the Geological Society of Korea 19(3):115–126.
  • Lovelace, David M., Scott A. Hartman and William R. Wahl. 2008. Morphology of a specimen of Supersaurus (Dinosauria, Sauropoda) from the Morrison Formation of Wyoming, and a re-evaluation of diplodocid phylogeny. Arquivos do Museu Nacional, Rio de Janeiro 65(4):527–544.
  • Olshevsky, George. A revision of the parainfraclass Archosauria Cope, 1869, excluding the advanced Crocodylia. Mesozoic Meanderings 2:1–196.
  • Tschopp, Emanuel, Octávio Mateus and Roger B. J. Benson. 2015. A specimen-level phylogenetic analysis and taxonomic revision of Diplodocidae (Dinosauria, Sauropoda). PeerJ 2:e857. doi:10.7717/peerj.857

 

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In a word, amazingly. After 6 days (counting public galleries last Sunday), 4300 photos, 55 videos, dozens of pages of notes, and hundreds of measurements, we’re tired, happy, and buzzing with new observations and ideas.

We caught up with some old friends. Here Mike is showing an entirely normal and healthy level of excitement about meeting CM 584, a specimen of Camarasaurus from Sheep Creek, Wyoming. You may recognize this view of these dorsals from Figure 9 in our 2013 PeerJ paper.

We spent an inordinate amount of time in the public galleries, checking out the mounted skeletons of Apatosaurus and Diplodocus (and Gilmore’s baby Cam, and the two tyrannosaurs, and, and…).

I had planned a trip to the Carnegie primarily to have another look at the Haplocanthosaurus holotypes, CM 572 and CM 879. I was also happy for the chance to photograph and measure these vertebrae, CM 36034, which I think have never been formally described or referred to Haplocanthosaurus. As far as I know, other than a brief mention in McIntosh (1981) they have not been published on at all. I’m planning on changing that in the near future, as part of the larger Haplocanthosaurus project that now bestrides my career like a colossus.

The real colossus of the trip was CM 555, which we’ve already blogged about a couple of times. Just laying out all of the vertebrae and logging serial changes was hugely useful.

Incidentally, in previous posts and some upcoming videos, we’ve referred to this specimen as Brontosaurus excelsus, because McIntosh (1981) said that it might belong to Apatosaurus excelsus. I was so busy measuring and photographing stuff that it wasn’t until Friday that I realized that McIntosh made that call because CM 555 is from the same locality as CM 563, now UWGM 15556, which was long thought to be Apatosaurus excelsus but which is now (i.e., Tschopp et al. 2015) referred to Brontosaurus parvus. So CM 555 is almost certainly B. parvus, not B. excelsus, and in comparing the specimen to Gilmore’s (1936) plates of CM 563, Mike and I thought they were a very good match.

Finding the tray of CM 555 cervical ribs was a huge moment. It added a ton of work to our to-do lists. First we had to match the ribs to their vertebrae. Most of them had field numbers, but some didn’t. Quite a few were broken and needed to be repaired – that’s what I’m doing in the above photo. Then they all had to be measured and photographed.

It’s amazing how useful it was to be able to reassociate the vertebrae with their ribs. We only did the full reassembly for c6, in part because it was the most complete and perfect of all of the vertebrae, and in part because we simply ran out of time. As Mike observed in his recent post, it was stunning how the apatosaurine identity of the specimen snapped into focus as soon as we could see a whole cervical vertebra put back together with all of its bits.

We also measured and photographed the limb bones, including the bite marks on the radius (above, in two pieces) and ulna (below, one piece). Those will of course go into the description.

And there WILL BE a description. We measured and photographed every element, shot video of many of them, and took pages and pages of notes. Describing even an incomplete sauropod skeleton is a big job, so don’t expect that paper this year, but it will be along in due course. CM 555 may not be the most complete Brontosaurus skeleton in the world, but our ambition is to make it the best-documented.

In the meantime, we hopefully left things better documented than they had been. All of the separate bits of the CM 555 vertebrae – the centra, arches, and cervicals ribs – now have the cervical numbers written on in archival ink (with permission from collections manager Amy Henrici, of course), so the next person to look at them can match them up with less faffing about.

We have people to thank. We had lunch almost every day at Sushi Fuku at 120 Oakland Avenue, just a couple of blocks down Forbes Avenue from the museum. We got to know the manager, Jeremy Gest, and his staff, who were unfailingly friendly and helpful, and who kept us running on top-notch food. So we kept going back. If you find yourself in Pittsburgh, check ’em out. Make time for a sandwich at Primanti Bros., too.

We owe a huge thanks to Calder Dudgeon, who took us up to the skylight catwalk to get the dorsal-view photos of the mounted skeletons (see this post), and especially to Dan Pickering, who moved pallets in collections using the forklift, and moved the lift around the mounted skeletons on Tuesday. Despite about a million ad hoc requests, he never lost patience with us, and in fact he found lots of little ways to help us get our observations and data faster and with less hassle.

Our biggest thanks go to collections manager Amy Henrici, who made the whole week just run smoothly for us. Whatever we needed, she’d find. If we needed something moved, or if we needed to get someplace, she’d figure out how to do it. She was always interested, always cheerful, always helpful. I usually can’t sustain that level of positivity for a whole day, much less a week. So thank you, Amy, sincerely. You have a world-class collection. We’re glad it’s in such good hands.

What’s next? We’ll be posting about stuff we saw and learned in the Carnegie Museum for a long time, probably. And we have manuscripts to get cranking on, some of which were already gestating and just needed the Carnegie visit to push to completion. As always, watch this space.

References

Mike’s and Matt’s excellent adventure in Pittsburgh continues! Today was Day 4, and just as yesterday offered us a unique opportunity to see the mounted Dipodocus and Apatosaurus skeletons up close on a lift, so today we got to look the two mounts from directly above!

Thanks to our host Amy Henrici and to Calder Dudgeon, we were able to go up to the maintenance balconies above the dinosaur hall, and from there we were able to see this:

It was a little bit scary up there: here’s Matt’s vertical panorama photo of me. Just below the balcony I’m standing on you can see another, which is actually far below up but further back. Below that is the main balcony that overlooks the hall. And below that, the hall itself, showing Diplodocus from above:

We think this is a first: we don’t know of any published photos of mounted sauropods from above — but now, there are some. Let’s take a closer look at the torsos:

Diplodocus carnegii holotype CM 84, torso, in dorsal view, anterior to right.

Apatosaurus louisae holotype CM 3018, torso, in dorsal view, anterior to left.

You can immediately see from here that Apatosaurus is a much broader animal than Diplodocus. That much, we could have guessed. What’s more interesting is that Apatosaurus seems to be slightly broader at the shoulders than at the hips, whereas the opposite is the case in Diplodocus.

This observation left us wondering what’s known about the relative widths of the forelimb and hindlimb articulations in extant animals. What, from the modern bestiary, has hips broader than its shoulders, and what has shoulders wider than its hips? We have no idea. Does anyone know if this has been studied, or better yet summarised?

If you followed along with the last post in this series, you now have some bird vertebrae to play with. Here are some things to do with them.

1. Learn the parts of the vertebrae, and compare them with those of other animals

Why are we so excited about bird vertebrae around here? Mostly because birds are reasonably long-necked living dinosaurs, and although their vertebrae differ from those of sauropods in relative proportions, all of the same bits are present in roughly the same places. If you know the parts of a bird vertebra and what each one does, you have a solid foundation for inferring the functions of sauropod vertebrae. Here’s a diagram I made for my SVP poster with Kent Sanders way back in 1999. I used an ostrich vertebra here but you should be able to find the same features in a cervical vertebra of just about any bird.

These are both middle cervical vertebrae in right lateral view. A middle cervical vertebra of a big ostrich will be between 3 and 4 inches long (7.5-10 cm), and one from a big brachiosaur like Giraffatitan will be about ten times longer.

I should do a whole post on neck muscles, but for now see this post and this paper.

2. Put the vertebrae in order, and rearticulate them

It is often useful to know where you are in the neck, and the only way to figure that out is to determine the serial position of the vertebrae. Here’s an articulated cervical series of a turkey in left lateral view, from Harvey et al. (1968: pl. 65):

Harvey’s “dorsal spine” is the neural spine or spinous process, and his “ventral spine” is the carotid process. The “alar process” is a sort of bridge of bone connecting the pre- and postzygapophyses; you can see a complete version in C3 in the photo below, and a partial version in C4.

Speaking of that photo, here’s my best attempt at rearticulating the vertebrae from the smoked turkey neck I showed in the previous post, with all of the vertebrae in left dorsolateral view.

These things don’t come with labels and it can take a bit of trial and error to get them all correctly in line. C2 is easy, with its odd articular surface for the atlas and narrow centrum with a ventral keel. Past that, C3 and C4 are usually pretty blocky, the mid-cervicals are long and lean, and then the posterior cervicals really bulk out. Because this neck section had been cut before I got it, some of the vertebrae look a little weird. Somehow I’m missing the front half of C6. The back half of C14 is also gone, presumably still stuck to the bird it went with, and C7 and C12 are both sectioned (this will come in handy later). I’m not 100% certain that I have C9 and C10 in the right order. One handy rule: although the length and neural spine height change in different ways along the column, the vertebrae almost always get wider monotonically from front to back.

And here’s the duck cervical series, in right lateral view. You can see that although the specific form of each vertebra is different from the equivalent vert in a turkey, the same general rules apply regarding change along the column.

Pro tip: I said above that these things don’t come with labels, but you can fix that. Once you have the vertebrae in a satisfactory order, paint a little dot of white-out or gesso on each one, and use a fine-point Sharpie or art pen to write the serial position (bone is porous and the white foundation will keep the ink from possibly making a mess). You may also want to put the vertebrae on a string or a wire to keep them in the correct order, but even so, it’s useful to have the serial position written on each vertebra in case you need to unstring them later.

3. Look at the air spaces

One nice thing about birds is that all of the species that are readily commercially available have pneumatic traces on and in their vertebrae, which are broadly comparable to the pneumatic vertebrae of sauropods.

The dorsal vertebrae of birds are even more obviously similar to those of sauropods than are the cervicals. These dorsal vertebrae of a duck (in left lateral view) show a nice variety of pneumatic features: lateral fossae on the centrum (what in sauropods used to be called “pleurocoels”), both with and without foramina, and complexes of fossae and foramina on the neural arches. Several of the vertebrae have small foramina on the centra that I assume are neurovascular. One of the challenges in working with the skeletal material of small birds is that it becomes very difficult to distinguish small pneumatic foramina and spaces from vascular traces. Although these duck vertebrae have small foramina inside some of the lateral fossae, the centra are mostly filled with trabecular, marrow-filled bone. In this, they are pretty similar to the dorsal vertebrae of Haplocanthosaurus, which have fossae on the neural arches and the upper parts of the centra, but for which the ventral half of each centrum is a brick of non-pneumatic bone. For more on distinguishing pneumatic and vascular traces in vertebrae, see O’Connor (2006) and Wedel (2007).

This turkey cervical, in left posterolateral view, shows some pneumatic features to nice advantage. The lateral pneumatic foramina in bird cervicals are often tucked up inside the cervical rib loops where they can be hard to see and even harder to photograph, but this one is out in the open. Also, the cervicals of this particular turkey have a lot of foramina inside the neural canal. In life these foramina are associated with the supramedullary diverticula, a set of air-filled tubes that occupy part of the neural canal in many birds — see Atterholt and Wedel (2018) for more on this unusual anatomical system. The development of foramina inside the neural canal seems to be pretty variable among individuals. In ostriches I’ve seen individuals in which almost every cervical has foramina inside the canal, and many others with no foramina. For turkeys it’s even more lopsided in my experience; this is the first turkey in which I’ve found really clear pneumatic foramina inside the neural canals. This illustrates one of the most important aspects of pneumaticity: pneumatic foramina and cavities in bones show that air-filled diverticula were present, but the absence of those holes and spaces does not mean that diverticula were absent. Mike and I coined the term “cryptic diverticula” for those that leave no diagnostic traces on the skeleton — for more on that, see the discussion section in Wedel and Taylor (2013b).

Finally, it’s worth taking a look at the air spaces inside the vertebrae. Here’s a view into C12 of the turkey cervical series shown above. The saw cut that sectioned this neck happened to go through the front end of this vertebra, and with a little clean-up the honeycomb of internal spaces is beautifully displayed. If you are working with an intact vertebra, the easiest way to see this for yourself is to get some sandpaper and sand off the front end of the vertebra. It only takes a few minutes and you’ll be less likely to damage the vertebrae or your fingers than if you cut the vertebra with a saw. Similar complexes of small pneumatic cavities are present in the vertebrae of some derived diplodocoids, like Barosaurus (see the lateral view in the middle of this figure), and in most titanosauriforms (for example).

I have one more thing for you to look for in your bird vertebrae, and that will be the subject of the next installment in this series. Stay tuned!

References

What it says on the tin. This is a specimen from the UCMP comparative collection.

I was just going to post this photo with zero commentary, but I can’t help myself. Note that on the two vertebrae in the middle, the crista transverso-obliqua (what in non-avian dinos would be the spinopostzygapophyseal lamina or SPOL) rises higher than either the neural spine apex or the epipophyses. That’s crazy. And it demonstrates something we also see in sauropods, which is that laminae are not merely the plates of bone left behind after pneumatization has scooped all of the unnecessary material out of a normal vertebra–sometimes they are additive structures, too.

If all of that sounded like gibberish, I can sympathize. I spent my first few months as a sauropodologist just learning the lingo (another thing I should blog about sometimes). Here’s a labeled version:

As long as I’m yapping, note the light shining through the honeycombed internal structure of these highly pneumatic vertebrae. For more on the ridiculous pneumaticity of pelican bones, see this post and this one. For more on the homology of bird and sauropod vertebrae, see Wedel and Sanders (2002), and for more on laminae as additive versus reductive structures, see the discussion on pages 210-212 of Wedel (2007).

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Matt’s drawn my attention to a bizarre fact: despite 17 separate posts about Xenoposeidon on this blog (linked from here and here), we’ve never shown a decent scan of Lydekker’s (1893) original illustration of NHMUK PV R2095, the partial mid-to-posterior dorsal vertebra that since Taylor and Naish (2007) has been the holotype specimen of Xenoposeidon proneneukos — and since Taylor (2018) has been known to represent a rebbachisaurid.

Well, here it is at last!

That’s Xeno on the left, of course. On the right, we have one of the various Wealden titanosauriform dorsal vertebrae that were constantly getting referred back and forth between taxa in the late 1800s. I think it might be one of the NPMUK PR R90 vertebrae, perhaps the one that, for disambiguation purposes, I’ve informally named R90a.

Lydekker — or, more likely, an uncredited illustrator — did rather a good job on this, as we can see by juxtaposing the illustration with the now well-known left-lateral photo that’s launched a thousand blog-posts:

The main differences here seem to pertain to how Lydekker and I perceived “lateral”. I think he has the vertebra rotated slightly away from us, so that it’s leaning into the page, and that’s why the centrum appears slightly taller and the arch slightly less tall than in my photo. He seems to have a bit more matrix stuck on the front of the centrum — perhaps because slightly more prep has been done since 1893 — but, worryingly, slightly less bone around the cotyle. I think that can only be illustration error, since that bone is definitely there.

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An important paper is out today: Carpenter (2018) names Maraapunisaurus, a new genus to contain the species “Amphicoelias fragillimus, on the basis that it’s actually a rebbachisaurid rather than being closely related to the type species Amphicoelias altus.

Carpenter 2018: Figure 5. Comparison of the neural spine of Maraapunisaurus fragillimus restored as a rebbachisaurid (A), and the dorsal vertebrae of Rebbachisaurus garasbae (B), and Histriasaurus boscarollii (C). Increments on scale bars = 10 cm.

And it’s a compelling idea, as the illustration above shows. The specimen (AMNH FR 5777) has the distinctive dorsolaterally inclined lateral processes of a rebbachisaur, as implied by the inclined laminae meeting at the base of the SPOLs, and famously has the very excavated and highly laminar structure found in rebbachisaurs — hence the species name fragillimus.

Ken’s paper gives us more historical detail than we’ve ever had before on this enigmatic and controversial specimen, including extensive background to the excavations. The basics of that history will be familiar to long-time readers, but in a nutshell, E. D. Cope excavated the partial neural arch of single stupendous dorsal vertebra, very briefly described it and illustrated it (Cope 1878), and then … somehow lost it. No-one knows how or where it went missing, though Carpenter offers some informed speculation. Most likely, given the primitive stabilisation methods of the day, it simply crumbled to dust on the journey east.

Carpenter 2018: Frontispiece. E. D. Cope, the discoverer of AMNH FR 5777, drawn to scale with the specimen itself.

Cope himself referred the vertebra to his own existing sauropod genus Amphicoelias — basically because that was the only diplodocoid he’d named — and there it has stayed, more or less unchallenged ever since. Because everyone knows Amphicoelias (based on the type species A. altus) is sort of like Diplodocus(*), everyone who’s tried to reconstruct the size of the AMNH FR 5777 animal has done so by analogy with Diplodocus — including Carpenter himself in 2006, Woodruff and Foster (2014) and of course my own blog-post (Taylor 2010).

(*) Actually, it’s not; but that’s been conventional wisdom.

Ken argues, convincingly to my mind, that Woodruff and Foster (2014) were mistaken in attributing the great size of the specimen to a typo in Cope’s description, and that it really was as big as described. And he argues for a rebbachisaurid identity based on the fragility of the construction, the lamination of the neural spine, the extensive pneumaticity, the sheetlike SDL, the height of the postzygapophyses above the centrum, the dorsolateral orientation of the transverse processes, and other features of the laminae. Again, I find this persuasive (and said so in my peer-review of the manuscript).

Carpenter 2018: Figure 3. Drawing made by E.D. Cope of the holotype of Maraapunisaurus fragillimus (Cope, 1878f) with parts labeled. “Pneumatic chambers*” indicate the pneumatic cavities dorsolateral of the neural canal, a feature also seen in several rebbachisaurids. Terminology from Wilson (1999, 2011) and Wilson and others (2011).

If AMNH FR 5777 is indeed a rebbachisaur, then it can’t be a species of Amphicoelias, whose type species is not part of that clade. Accordingly, Ken gives it a new generic name in this paper, Maraapunisaurus, meaning “huge reptile” based on Maraapuni, the Southern Ute for “huge” — a name arrived at in consultation with the Southern Ute Cultural Department, Ignacio, Colorado.

How surprising is this?

On one level, not very: Amphicoelias is generally thought to be a basal diplodocoid, and Rebbachisauridae was the first major clade to diverge within Diplodocoidae. In fact, if Maraapunisaurus is basal within Rebbachisauridae, it may be only a few nodes away from where everyone previously assumed it sat.

On the other hand, a Morrison Formation rebbachisaurid would be a big deal for two reasons. First, because it would be the only known North American rebbachisaur — all the others we know are from South America, Africa and Europe. And second, because it would be, by some ten million years, the oldest known rebbachisaur — irritatingly, knocking out my own baby Xenoposeidon (Taylor 2018), but that can’t be helped.

Finally, what would this new identity mean for AMNH FR 5777’s size?

Carpenter 2018: Figure 7. Body comparisons of Maraapunisaurus as a 30.3-m-long rebbachisaurid (green) compared with previous version as a 58-m-long diplodocid (black). Lines within the silhouettes approximate the distal end of the diapophyses (i.e., top of the ribcage). Rebbachisaurid version based on Limaysaurus by Paul (2016), with outline of dorsal based on Rebbachisaurus; diplodocid version modified from Carpenter (2006).

Because dorsal vertebrae in rebbachisaurids are proportionally taller than in diplodocids, the length reconstructed from a given dorsal height is much less for rebbachisaurs: so much so that Ken brings in the new version, based on the well-represented rebbachisaur Limaysaurus tessonei, at a mere 30.3 m, only a little over half of the 58 m he previously calculated for a diplodocine version. That’s disappointing for those of us who like our sauropods stupidly huge. But the good news is, it makes virtually no difference to the height of the animal, which remains prodigious — 8 m at the hips, twice the height of a giraffe’s raised head. So not wholly contemptible.

Exciting times!

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