In mammals — certainly the most-studied vertebrates — regional differentiation of the vertebral column is distinct and easy to spot. But things aren’t so simple with sauropods. We all know that the neck of any tetrapod is made up of cervical vertebrae, and that the trunk is made up of dorsal vertebrae (subdivided into thoracic and lumbar vertebrae in the case of mammals). But how do we tell whether a given verebra is a posterior cervical or an anterior dorsal?

Here two vertabrae: a dorsal vertebra (D3) and a cervical vertebra (C13) from CM 84, the holotype of Diplodocus carnegii, modified from Hatcher (1901: plates III and VII):

It’s easy to tell these apart, even when as here we have only lateral-view images: the dorsal vertebra is tall, its centrum is short, its neural spine is anteroposteriorly compressed and its parapophysis is up on the dorsal half of the centrum; but the cervical vertebra is relatively low, its centrum is elongated, its neural spine is roughly triangular and its parapophysis hangs down well below the centrum (and has a cervical rib fused to it and the diapophysis).

But things get trickier in the shoulder region because, in sauropods at least, the transition through the last few cervicals to the first few dorsals is gradual — the vertebrae become shorter, taller and broader — and tends to have no very obvious break point. In this respect, they differ from mammals, in which the regional differentiation of the spinal column is more abrupt. (Although even here, things may not be as simple as generally assumed: for example, Gunji and Endo (2016) argued that the 1st thoracic vertebra of the giraffe behaves functionally like an 8th cervical.)

So here are those two vertebrae in context: the sequence D3 D2 D1 C15 C14 C13 in CM 84, the holotype of Diplodocus carnegii, modified from Hatcher (1901: plates III and VII):

Given that the leftmost is obviously a dorsal and the rightmost obviously a cervical, where would you place the break-point?

The most usual definition seems to be that the first dorsal vertebra is the first one that has a free rib, i.e. one not fused to the vertebra: in the illustration above, you can see that the three cervicals on the right all have their cervical ribs fused to their diapophyses and parapophyses, and the three dorsals on the left do not. This definition of the cervical/dorsal distinction seems to be widely assumed, but it is rarely explicitly asserted. (Does anyone know of a paper that lays it out for sauropods, or for dinosaurs more generally?)

But wait!

Hatcher (1903:8) — the same dude — in his Haplocanthosaurus monograph, writes:

The First Dorsal (Plate I., Fig. 1). […] That the vertebra now under consideration was a dorsal is conclusively shown not by the presence of tubercular and capitular rib facets showing that it supported on either side a free rib, for there are in our collections of sauropods, skeletons of other dinosaurs fully adult but, with the posterior cervical, bearing free cervical ribs articulating by both tubercular and capitular facets as do the ribs of the dorsal region. The character in this vertebra distinguishing it as a dorsal is the broadly expanded external border of the anterior branch of the horizontal lamina [i.e. what we would now call the centroprezygapophyseal lamina]. This element has been this modified in this and the succeeding dorsal, no doubt, as is known to be the case in Diplodocus to give greater surface for the attachment of the powerful muscles necessary for the support of the scapula.

Hatcher’s illustrations show this feature, though they don’t make it particularly obvious: here are the last two cervicals and the first dorsal, modified from Hatcher (1903:plate I), with the facet in question highlighted in pink: right lateral view at the top, then anterior, and finally posterior view at the bottom. (The facet is only visible in lateral and anterior views):

Taken at face value, Hatcher’s words here seem to imply that he considers the torso to begin where the scapula first lies alongside the vertebral column. Yet if you go back to the Diplodocus transition earlier in this post, a similar scapular facet is not apparent in the vertebra that he designated D1, and seems to be present only in D2.

Is this scapular-orientation based definition a widespread usage? Can anyone point me to other papers that use it?

Wilson (2002:226) mentions a genetic definition of the cervical/dorsal distinction

Vertebral segment identity may be controlled by a single Hox gene. The cervicodorsal transition in many tetrapods, for instance, appears to be defined by the expression boundary of the Hoxc-6 gene.

But this of course is no use in the case of extinct animals such as sauropods.

So what’s going on here? In 1964, United States Supreme Court Justice Potter Stewart, in describing his threshold test for obscenity, famously said “I shall not today attempt further to define the kinds of material I understand to be embraced within that shorthand description, and perhaps I could never succeed in intelligibly doing so. But I know it when I see it.” Is that all we have for the definition of what makes a vertebra cervicals as opposed to dorsal? We know it when we see it?

Help me out, folks! What should the test for cervical-vs-dorsal be?

References

  • Gunji, Mego, and Hideki Endo. 2016. Functional cervicothoracic boundary modified by anatomical shifts in the neck of giraffes. Royal Society Open Science 3:150604. doi:10.1098/rsos.150604
  • Hatcher, Jonathan B. 1901. Diplodocus (Marsh): its osteology, taxonomy and probable habits, with a restoration of the skeleton. Memoirs of the Carnegie Museum 1:1-63 and plates I-XIII.
  • Hatcher, J. B. 1903b. Osteology of Haplocanthosaurus with description of a new species, and remarks on the probable habits of the Sauropoda and the age and origin of the Atlantosaurus beds; additional remarks on Diplodocus. Memoirs of the Carnegie Museum 2:1-75 and plates I-VI.
  • Wilson, Jeffrey A. 2002. Sauropod dinosaur phylogeny: critique and cladistic analysis. Zoological Journal of the Linnean Society 136:217-276.

A. Recovered skeletal elements of Haplocanthosaurus specimen MWC 8028. B. Caudal vertebra 3 in right lateral view. C. The same vertebra in posterior view. Lines show the location of sections for D and E. D. Midsagittal CT slice. The arrow indicates the ventral expansion of the neural canal into the centrum. E. Horizontal CT slice at the level of the neural arch pedicles, with anterior toward the top. Arrows indicate the lateral expansions of the neural canal into the pedicles. B-E are shown at the same scale. Wedel et al. (2021: fig. 1).

New paper out today:

Wedel, Mathew; Atterholt, Jessie; Dooley, Jr., Alton C.; Farooq, Saad; Macalino, Jeff; Nalley, Thierra K.; Wisser, Gary; and Yasmer, John. 2021. Expanded neural canals in the caudal vertebrae of a specimen of Haplocanthosaurus. Academia Letters, Article 911, 10pp. DOI: 10.20935/AL911 (link)

The paper is new, but the findings aren’t, particularly. They’re essentially identical to what we reported in our 1st Paleo Virtual Conference slide deck and preprint, and in the “Tiny Titan” exhibit at the Western Science Center, just finally out in a peer-reviewed journal, with better figures. The paper is open access and free to the world, and it’s short, about 1600 words, so this recap will be short, too.

A. Photograph of a 3D-printed model of the first three caudal vertebrae of Haplocanthosaurus specimen MWC 8028, including endocasts of the neural canal (yellow) and intervertebral joints (blue), in right lateral view, and with the neural canal horizontal. B. Diagram of the same vertebrae in midsagittal section, emphasizing the volumes of the neural canal (yellow) and intervertebral joint spaces (blue). Anterior is to the right. Wedel et al. (2021: fig. 2).

John Foster and I described Museum of Western Colorado (MWC) specimen 8028, a partial skeleton of Haplocanthosaurus from Snowmass, Colorado, in late 2014. One weird thing about that specimen (although not the only weird thing) is that the neural canals of the tail vertebrae are bizarrely expanded. In most vertebrae of most critters, the neural canal is a cylindrical tunnel, but in these vertebrae the neural canals are more like spherical vacuities.

John and I didn’t know what to make of that back in 2014. But a few years later I started working with Jessie Atterholt on bird anatomy, which led me to do a little project on the whole freaking zoo of weird stuff that birds and other dinosaurs do with their neural canals, which led to the 1PVC presentation, which led to this. 

Caudal vertebra 3 of Haplocanthosaurus specimen MWC 8028 in left posterolateral (A), posterior (B), and right posterolateral (C) views, with close-ups (D and E). In A and B, a paintbrush is inserted into one of the lateral recesses, showing that the neural canal is wider internally than at either end. Wedel et al. (2021: fig. 3).

Of course there will be more posts and more yapping, as signaled by the ‘Part 1’ in the post title. Although I am extremely satisfied with the streamlined, 1600-word missile of information and reasoning that just dropped, there are parts that I want to unpack, that haven’t been unpacked before. But the paper launched at midnight-thirty, Pacific Daylight Time, I’m up way too late finishing this first post, and I reckon the rest will keep for a few hours at least.

Anatomical features of the neural canal in birds and other dinosaurs. A. MWC 9698, a mid caudal vertebra of Apatosaurus in posterodorsal view. Arrows highlight probable vascular foramina in the ventral floor of the neural canal. B. LACM 97479, a dorsal vertebra of Rhea americana in left anterolateral view. Arrows highlight pneumatic foramina inside the neural canal. C. A hemisected partial synsacrum of a chicken, Gallus domesticus, obtained from a grocery store. Anterior is to the right. The bracket shows the extent of the dorsal recess for the glycogen body, which only spans four vertebrae. Arrows highlight the transverse grooves in the roof of the neural canal for the lumbosacral organ. D. Sagittal (left) and transverse (right) CT slices through the sacrum of a juvenile ostrich, Struthio camelus. The bracket shows the extent of the lumbosacral expansion of the spinal cord. Indentations in the roof of the neural canal house the lumbosacral organ. In contrast to the chicken, the ostrich has a small glycogen body that does not leave a distinct osteological trace. Yellow arrows show the longitudinal troughs in the ventral floor of the neural canal that house the ventral eminences of the spinal cord. Wedel et al. (2021: fig. 4).

I have a ton of people to thank. John Foster, obviously, for initiating the line of research that led here. Julia McHugh for access to the MWC collections, and for being an excellent sounding board regarding the Morrison Formation, sauropod dinosaurs, and crafting ambitious but tractable research projects. Anne Weil for helping me be methodical in thinking through the logic of the paper, and Mike Taylor for helping me get it polished. Niels Bonde, Steven Jasinski, and David Martill for constructive reviews, which were published alongside the paper. We couldn’t take all of their suggestions because of space limitations, but figures 3 and 4 were born because they asked for them, and that’s not a small thing. Vicki and London Wedel for putting up with me at various points in this project, especially in the last few days as I’ve been going bonkers correcting page proofs. And finally, because I’m the one writing this blog post, my coauthors: Jessie Atterholt, Alton Dooley, Saad Farooq, Jeff Macalino, Thierra Nalley, Gary Wisser, and John Yasmer, for their contributions and for their patience during the unusually long gestation of this very short paper.

More to say about all that in the future. For now, yay, new paper. Have fun with it. Here’s the link again.

References

 

FIGURE 7.1. Pneumatic features in dorsal vertebrae of Barapasaurus (A–D), Camarasaurus (E–G), Diplodocus (H–J), and Saltasaurus (K–N). Anterior is to the left; different elements are not to scale. A, A posterior dorsal vertebra of Barapasaurus. The opening of the neural cavity is under the transverse process. B, A midsagittal section through a middorsal vertebra of Barapasaurus showing the neural cavity above the neural canal. C, A transverse section through the posterior dorsal shown in A (position 1). In this vertebra, the neural cavities on either side are separated by a narrow median septum and do not communicate with the neural canal. The centrum bears large, shallow fossae. D, A transverse section through the middorsal shown in B. The neural cavity opens to either side beneath the transverse processes. No bony structures separate the neural cavity from the neural canal. The fossae on the centrum are smaller and deeper than in the previous example. (A–D redrawn from Jain et al. 1979:pl. 101, 102.) E, An anterior dorsal vertebra of Camarasaurus. F, A transverse section through the centrum (E, position 1) showing the large camerae that occupy most of the volume of the centrum. G, a horizontal section (E, position 2). (E–G redrawn from Ostrom and McIntosh 1966:pl. 24.) H, A posterior dorsal vertebra of Diplodocus. (Modified from Gilmore 1932:fig. 2.) I, Transverse sections through the neural spines of other Diplodocus dorsals (similar to H, position 1). The neural spine has no body or central corpus of bone for most of its length. Instead it is composed of intersecting bony laminae. This form of construction is typical for the presacral neural spines of most sauropods outside the clade Somphospondyli. (Modified from Osborn 1899:fig. 4.) J, A horizontal section through a generalized Diplodocus dorsal (similar to H, position 2). This diagram is based on several broken elements and is not intended to represent a specific specimen. The large camerae in the midcentrum connect to several smaller chambers at either end. K, A transverse section through the top of the neural spine of an anterior dorsal vertebra of Saltasaurus (L, position 1). Compare the internal pneumatic chambers in the neural spine of Saltasaurus with the external fossae in the neural spine of Diplodocus shown in J. L, An anterior dorsal vertebra of Saltasaurus. M, A transverse section through the centrum (L, position 2). N, A horizontal section (L, position 3). In most members of the clade Somphospondyli the neural spines and centra are filled with small camellae. (K–N modified from Powell 1992:fig. 16.) [Figure from Wedel 2005.]

Here’s figure 1 from my 2005 book chapter. I tried to cram as much pneumatic sauropod vertebra morphology into one figure as I could. All of the diagrams are traced from pre-existing published images except the horizontal section of the Diplodocus dorsal in J, which is a sort of generalized cross-section that I based on broken centra of camerate vertebrae from several taxa (like the ones shown in this post). One thing that strikes me about this figure, and about most of the CT and other cross-sections that I’ve published or used over the years (example), is that they’re more or less bilaterally symmetrical. 

We’ve talked about asymmetrical vertebrae before, actually going back to the very first post in Xenoposeidon week, when this blog was only a month and a half old. But not as much as I thought. Given how much space asymmetry takes up in my brain, it’s actually weird how little we’ve discussed it.

The fourth sacral centrum of Haplocanthosaurus CM 879, in left and right lateral view (on the left and right, respectively). Note the distinct fossa under the sacral rib attachment on the right, which is absent on the left.

Also, virtually all of our previous coverage of asymmetry has focused on external pneumatic features, like the asymmetric fossae in this sacral of Haplocanthosaurus (featured here), in the tails of Giraffatitan and Apatosaurus (from Wedel and Taylor 2013b), and in the ever-popular holotype of Xenoposeidon. This is true not just on the blog but also in our most recent paper (Taylor and Wedel 2021), which grew out of this post.

Given that cross-sectional asymmetry has barely gotten a look in before now, here are three specimens that show it, presented in ascending levels of weirdness.

First up, a dorsal centrum of Haplocanthosaurus, CM 572. This tracing appeared in Text-fig 8 in my solo prosauropod paper (Wedel 2007), and the CT scout it was traced from is in Fig 6 in my saurischian air-sac paper (Wedel 2009). The section shown here is about 13cm tall dorsoventrally. The pneumatic fossa on the left is comparatively small, shallow, and lacks very distinct overhanging lips of bone. The fossa on the right is about twice as big, it has a more distinct bar of bone forming a ventral lip, and it is separated from the neural canal by a much thinner plate of bone. The fossa on the left is more similar to the condition in dorsal vertebrae of Barapasaurus or juvenile Apatosaurus, where as the one on the right shows a somewhat more extensive and derived degree of pneumatization. The median septum isn’t quite on the midline of the centrum, but it’s pretty stout, which seems to be a consistent feature in presacral vertebrae of Haplocanthosaurus.

 

Getting weirder. Here’s a section through the mid-centrum of C6 of CM 555, which is probably Brontosaurus parvus. That specific vert has gotten a lot of SV-POW! love over the years: it appears in several posts (like this one, this one, and this one), and in Fig 19 in our neural spine bifurcation paper (Wedel and Taylor 2013a). The section shown here is about 10cm tall, dorsoventrally. In cross-section, it has the classic I-beam configuration for camerate sauropod vertebrae, only the median septum is doing something odd — rather than attaching the midline of the bony floor of the centrum, it’s angled over to the side, to attach to what would normally be the ventral lip of the camera. I suspect that it got this way because the diverticulum on the right either got to the vertebra a little ahead of the one on the left, or just pneumatized the bone faster, because the median septum isn’t just bent, even the vertical bit is displaced to the left of the midline. I also suspect that this condition was able to be maintained because the median septa weren’t that mechanically important in a lot of these vertebrae. We use “I-beam” as a convenient shorthand to describe the shape, but in a metal I-beam the upright is as thick or thicker than the cross bits. In contrast, camerate centra of sauropod vertebrae could be more accurately described as a cylinders or boxes of bone with some holes in the sides. I think the extremely thin median septum is just a sort of developmental leftover from the process of pneumatization.

EDIT 3 days later: John Whitlock reminded me in the comments of Zurriaguz and Alvarez (2014), who looked at asymmetry in the lateral pneumatic foramina in cervical and dorsal vertebrae of titanosaurs, and found that consistent asymmetry along the cervical column was not unusual. They also explicitly hypothesized that the asymmetry was caused by diverticula on one side reaching the vertebrae earlier than diverticula on other other side. I believe they were the first to advance that idea in print (although I should probably take my own advice and scour the historical literature for any earlier instances), and needless to say, I think they’re absolutely correct.

Both of the previous images were traced from CTs, but the next one is traced from a photo of a specimen, OMNH 1882, that was broken transversely through the posterior centrum. To be honest, I’m not entirely certain what critter this vertebra is from. It is too long and the internal structure is too complex for it to be Camarasaurus. I think an apatosaurine identity is unlikely, too, given the proportional length of the surviving chunk of centrum, and the internal structure, which looks very different from CM 555 or any other apatosaur I’ve peered inside. Diplodocus and Brachiosaurus are also known from the Morrison quarries at Black Mesa, in the Oklahoma panhandle, which is where this specimen is from. Of those two, the swoopy ventral margin of the posterior centrum looks more Diplodocus-y than Brachiosaurus-y to me, and the specimen lacks the thick slab of bone that forms the ventral centrum in presacrals of Brachiosaurus and Giraffatitan (see Schwarz and Fritsch 2006: fig. 4, and this post). So on balance I think probably Diplodocus, but I could easily be wrong.

Incidentally, the photo is from 2003, before I knew much about how to properly photograph specimens. I really need to have another look at this specimen, for a lot of reasons.

Whatever taxon the vertebra is from, the internal structure is a wild scene. The median septum is off midline and bent, this time at the top rather than the bottom, the thick ventral rim of the lateral pneumatic foramen is hollow on the right but not on the left, and there are wacky chambers around the neural canal and one in the ventral floor of the centrum. 

I should point out that no-one has ever CT-scanned this specimen, and single slices can be misleading. Maybe the ventral rim of the lateral foramen is hollow just a little anterior or posterior to this slice. Possibly the median septum is more normally configured elsewhere in the centrum. But at least at the break point, this thing is crazy. 

What’s it all mean? Maybe the asymmetry isn’t noise, maybe it’s signal. We know that when bone and pneumatic epithelium get to play together, they tend to make weird stuff. Sometimes that weirdness gets constrained by functional demands, other times not so much. I think it’s very seductive to imagine sauropod vertebrae as these mechanically-optimized, perfect structures, but we have other evidence that that’s not always true (for example). Maybe as long as the articular surfaces, zygapophyses, epipophyses, neural spine tips, and cervical ribs — the mechanically-important bits — ended up in the right places, and the major laminae did a ‘good enough’ job of transmitting forces, the rest of each vertebra could just sorta do whatever. Maybe most of them end up looking more or less the same because of shared development, not because it was so very important that all the holes and flanges were in precisely the same places. That might explain why we occasionally get some really odd verts, like C11 of the Diplodocus carnegii holotype.

That’s all pretty hand-wavy and I haven’t yet thought of a way to test it, but someone probably will sooner or later. In the meantime, I think it’s valuable to just keep documenting the weirdness as we find it.

References

Can I really be the first one to have done this? Seems unlikely. Sing out in the comments if you’ve seen others.

Anyway, folks, here’s your new all-purpose scale silhouette. Useful fact: the standard metal folding chairs found from sea to shining sea are 29.25 inches tall, or 0.75 meters. Bernie might be in a plastic folding chair here, I dunno, I’m no expert. But folding chair seats are typically 16-17 inches off the ground, so it can’t be that far out.

Who will get Bernie into print first?

If you’re thinking that it’s about time to look at some sauropod vertebrae from the Salt Wash member of the Morrison Formation, well, you’re gol-durned right, pardner. Let’s ride.

Here’s a vertebra sticking out of the rock. For once it’s not in cross-section. We’re simply looking at the posterior surface of a dorsal vertebra and bits of its associated ribs. Let’s stand it up correctly:

And, well, heck, Alex, I’d like to go ahead and solve the puzzle:

Figure on the right from Wedel and Taylor (2013a), and composed in turn from plates in Hatcher (1901, Diplodocus), Hatcher (1903, Haplocanthosaurus), and Gilmore (1936, Apatosaurus).

UPDATE: I had the discovery sequence wrong–this is one of the bones that was first found by photographer Guy Tal, who then put ReBecca Hunt-Foster onto the area. ReBecca has since gone on to become Monument Paleontologist at Dinosaur National Monument, but at the time she was working as a BLM paleontologist out of the Moab office. ReBecca then brought out some more of us out to take a look, and that was the genesis of my work with her and John in the Salt Wash.

John Foster and Cary Woodruff were both there when I saw this vertebra for the first time. I think we set a new record for a consensus among paleontologists in concluding that this vertebra belongs to Haplocanthosaurus. The super-tall, cathedral-esque laminae arching over the neural canal and the up-tilted transverse processes are absolutely diagnostic, and not present in any other Morrison sauropods. Haplocanthosaurus is one of the rarer sauropods in the Morrison, so it’s nice to have one in our Salt Wash fauna. Not least because of all the other awesome sauropods out there, it’s this weird little duck that my destiny seems to have become intertwingled with (exhibits A, B, C, D, E, and counting).

Speaking of: did you remember that the Western Science Center exhibit on the Snowmass Haplocanthosaurus is still up for a couple more months? Have you seen it? Go see it!

Life restoration of Haplocanthosaurus by Brian Engh, for the Western Science Center exhibit.

So, hey, rock and roll, we have Haplocanthosaurus, and that is legitimately exciting. Between that and Camarasaurus (covered here) we have the primitive-and-unspecialized end of the Morrison sauropods sewn up. Anything bigger or more exotic? Why, yes, in fact. Stay tuned.

This is another “Road to Jurassic Reimagined, Part 2″ post. You know the drill: Part 1 is here, Part 2 will be going up here in the near future, Part 3 will be along sometime after that.

References

A life-size silhouette of the Snowmass Haplocanthosaurus, with Thierra Nalley, me, and Jessie Atterholt for scale. Photo by Jeremiah Scott.

Tiny Titan, a temporary exhibit about the Snowmass Haplocanthosaurus project, opened at the Western Science Center in Hemet, California, last night. How? Why? Read on.

Things have been quieter this year on the Haplo front than they were in 2018, for many reasons. My attention was pulled away by a lot of teaching and other day-job work–we’re launching a new curriculum at the med school, and that’s eaten an immense amount of time–and by some very exciting news from the field that I can’t tell you about quite yet (but watch this space). Things are still moving, and there will be a paper redescribing MWC 8028 and all the weird and cool things we’ve learned about it, but there are a few more timely things ahead of it in the queue.

One of the things going on behind the scenes this year is that Jessie Atterholt, Thierra Nalley, and I have been working with Alton Dooley, the director of the Western Science Center, on this exhibit. Alton has had a gleam in his eye for a long time of using the WSC’s temporary exhibit space to promote the work of local scientists, and we had the honor of being his first example. He also was not fazed by the fact that the project isn’t done–he wants to show the public the process of science in all of its serendipitous and non-linear glory, and not just the polished results that get communicated at the end.

Everything’s better cut in half. Photo by Jessie Atterholt.

Which is not to say that the exhibit isn’t polished. On the contrary, it looks phenomenal. Thanks to a loan from Julia McHugh at Dinosaur Journey in Colorado, most of the real fossils are on display. We’re only missing the ribs and most of the sacrum, which is too fragmentary and fragile to come out of its jacket. As you can see from the photo up top, there is a life-size vinyl silhouette of the Snowmass Haplo, with 3D prints of the vertebrae in approximate life position. Other 3D prints show the vertebrae before and after the process of sculpting, rescanning, and retrodeformation, as described in our presentation for the 1st Palaeontological Virtual Congress last year (that slideshow is a PeerJ Preprint, here). The exhibit also includes panels on “What is Haplocanthosaurus” and its relationships, on pneumaticity in sauropods, on the process of CT scanning and 3D modeling, and on the unusual anatomical features of the Snowmass specimen. The awesome display shown above, with the possibly-bumpy spinal cord and giant intervertebral discs reconstructed, was all Alton–he did the modeling, printing, and assembly himself.

Haplo vs Bronto. Thierra usually works on the evolution and development of the vertebral column in primates, so I had to show her how awesome vertebrae can be when they’re done right. Photo by Brittney Stoneburg.

My favorite thing in the exhibit is this striking comparison of one the Snowmass Haplo caudals with a proximal caudal from the big Oklahoma apatosaurine. This was Alton’s idea. He asked me if I had any photos of caudal vertebrae from really big sauropods that we could print at life size to compare to MWC 8028, and my mind went immediately to OMNH 1331, which is probably the second-largest-diameter vertebra of anything from all of North America (see the list here). It was also Alton’s idea to fill in the missing bits using one of Marsh’s plates of Brontosaurus excelsus from Como Bluff in Wyoming. It’s a pretty amazing display, and it turns out to have been a vehicle for discovery, too–I didn’t realize until I saw the verts side-by-side that the neural canal of the Snowmass Haplo caudal is almost as big as the neural canal from the giant apatosaurine caudal. It’s not a perfect comparison, because the OMNH fossil doesn’t preserve the neural canal, and the Como specimen isn’t that big, but proportionally, the Snowmass Haplo seems to have big honkin’ neural canals, not just at the midpoint (which we already knew), but all the way through. Looks like I have some measuring and comparing to do.

(Oh, about the title: we don’t know if the Snowmass Haplo was fully grown or not, but not all haplocanthosaurs were small. The mounted H. delfsi in Cleveland is huge, getting into Apatosaurus and Diplodocus territory. Everything we can assess in the Snowmass Haplo is fused, for what that’s worth. We have some rib chunks and Jessie will be doing histo on them to see if we can get ontogenetic information. I’ll keep you posted.)

Brian’s new Haplocanthosaurus restoration, along with some stinkin’ mammals. Photo by Jessie Atterholt.

Brian Engh contributed a fantastic life restoration of Haplocanthosaurus pro bono, thanks to this conversation, which took place in John Foster’s and ReBecca Hunt-Foster’s dining room about a month ago:

Brian: What are you drawing?

Me: Haplocanthosaurus.

Brian: Is that for the exhibit?

Me: Yup.

Brian (intense): Dude, I will draw you a Haplocanthosaurus.

Me: I know, but you’re a pro, and pros get paid, and we didn’t include a budget for paleoart.

Brian (fired up): I’m offended that you didn’t just ask me to draw you a Haplocanthosaurus.

Then he went to the Fosters’ couch, sat down with his sketchbook, and drew a Haplocanthosaurus. Not only is it a stunning piece on display in the exhibit, there are black-and-white printouts for kids to take and color (or for adults to take to their favorite tattoo artists, just sayin’). [Obligatory: this is not how things are supposed to work. We should all support original paleoart by supporting the artists who create it. But Brian just makes so damn many monsters that occasionally he has to kick one out for the heck of it. Also, I support him on Patreon, and you can, too, so at a stretch you could consider this the mother of all backer rewards.]

One special perk from the opening last night: Jessica Bramson was able to attend. Who’s that, you ask? Jessica’s son, Mike Gordon, found the first piece of bone from the Snowmass Haplo on their property in Colorado over a decade ago. Jessica and her family spent two years uncovering the fossils and trying to get paleontologists interested. In time she got in touch with John Foster, and the rest is history. Jessica lives in California now, and thanks to John’s efforts we were able to invite her to the exhibit opening to see her dinosaur meet the world. Stupidly, I did not get any photos with her, but I did thank her profusely.

A restored, retrodeformed caudal of the Snowmass Haplocanthosaurus, 3D-printed at life size for the exhibit. Photo swiped from the WSC Facebook page.

I owe a huge thanks to Alton Dooley for taking an interest in our work, and to the whole WSC crew for their hard work creating and promoting the exhibit. You all rock.

The exhibit will run through the end of March, 2020, at least. I deliberately did not show most of it, partly because I was too busy having fun last night to be diligent about taking photos, but mostly because I want you to go see it for yourself (I will do a retrospective post with more info after the exhibit comes down, for people who weren’t able to see it in person). If you make it out to Hemet, I hope you have half as much fun going through the exhibit as we did making it.

Regular readers will remember that we followed up our 1VPC talk about what it means for a vertebra to be horizontal by writing it up as a paper, and doing it in the open. That manuscripts is now complete, and published as a preprint (Taylor and Wedel 2019).

Taylor and Wedel (2018: Figure 5). Haplocanthosaurus sp. MWC 8028, caudal vertebra ?3, in cross section, showing medial aspect of left side, cranial to the right, in three orientations. A. In “articular surfaces vertical” orientation (method 2 of this paper). The green line joins the dorsal and ventral margins of the caudal articular surface, and is oriented vertically; the red line joins the dorsal and ventral margins of the cranial articular surface, and is nearly but not exactly vertical, instead inclining slightly forwards. B. In “neural canal horizontal” orientation (method 3 of this paper). The green line joins the cranial and caudal margins of the floor of the neural canal, and is oriented horizontally; the red line joins the cranial and caudal margins of the roof of the neural canal, and is close to horizontal but inclined upwards. C. In “similarity in articulation” orientation (method 4 of this paper). Two copies of the same vertebra, held in the same orientation, are articulated optimally, then the group is rotated until the two are level. The green line connects the uppermost point of the prezygapophyseal rami of the two copies, and is horizontal; but a horizontal line could join the two copies of any point. It happens that for this vertebra methods 3 and 4 (parts B and C of this illustration) give very similar results, but this is accidental.

The preprint has all the illustrations and their captions at the back of the PDF. If you prefer to have them inline in the text, where they’re referenced — and who wouldn’t? — you can download a better version of the manuscript from the GitHub archive.

By the way, you may have noticed that what started our written in Markdown has mutated into an MS-Word document. Why? Well, because journals won’t accept submissions in Markdown. It eas a tedious and error-prone job to convert the Markdown into MS-Word, and not one I am keen to repeat. For this reason, I think I am unlikely to use Markdown again for papers.

References

  • Taylor, Michael P., and Mathew J. Wedel. 2019. What do we mean by the directions “cranial” and “caudal” on a vertebra? PeerJ PrePrints 7:e27437v2. doi:10.7287/peerj.preprints.27437v2

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If you do, you might like to think about becoming a patron, making a small monthly donation to SV-POW!. We will use your money to fund research trips; if you donate $5 per month (or more), we will formally acknowledge you in papers that result from research trips that you helped to fund.

 

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.

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

If you were curious about the Wedel et al. presentation on the Snowmass Haplocanthosaurus at the 1st Palaeo Virtual Congress but didn’t attend the event, it is now preserved for posterity and freely available to the world as a PeerJ Preprint (as promised). Here’s the link.

I’ll have much more to say about this going forward, but for now here are slides 20 and 21 on the intervertebral joint spaces. This is obviously just the same vert cloned three times and articulated with itself. With the digital rearticulation of the reconstructed and retrodeformed caudal series still in progress, we cloned caudal 3, the only vertebra that preserves both sets of zygapophyses, to get a rough estimate of the sizes and shapes of the soft tissues that filled the intervertebral spaces and neural canal.

The reconstructed intervertebral discs (in blue) are very crude and diagrammatic. The reason I’m putting these particular slides up is to get the cited references out in the open on the blog, to start correcting the misapprehension that all non-mammalian amniotes have exclusively synovial intervertebral joints (see the discussion in the comments on this post). In the list below I’m including Banerji (1957), which is not cited in the presentation but which I did cite in that comment thread; it’s an important source and at least for now it is a free download. These refs are just the tip of a very big iceberg. One of my goals for 2019 is to do a series of posts reviewing the extensive literature on amphiarthrodial (fibrocartilaginous) intervertebral joints in living lepidosaurs and birds. Stay tuned!

And please go have a look at the presentation if you are at all interested or curious. As we said in the next to last slide, “this research is ongoing, and we welcome your input. If there are facts or hypotheses we haven’t considered but should, please let us know!”

References