Did apatosaurs have unusually large neural spines, too?
June 22, 2018
We all know that apatosaurines have big honkin’ cervical ribs (well, most of us know that). But did they also have unusually large neural spines?
The question occurred to me the other day when I was driving home from work. I was thinking about C10 of CM 3018, the holotype of Apatosaurus louisae, and I thought, “Man, that is a lot of neural spine right there.”
Why was I thinking about C10, particularly? I traced and also stacked Gilmore’s (1936) drawing for my 2002 paper with Kent Sanders, and recycled the trace for my 2007 prosauropod paper, and recycled the stack-o-C10s for my 2013 PeerJ paper with Mike. So for better or worse C10 is my mental shorthand for A. louisae, the same way that their respective C8s seem to capture the essence of Giraffatitan and Sauroposeidon.
I decided that the quick-and-dirty solution was to compare the vertebrae of A. louisae with those of Diplodocus carnegii, the default reference diplodocid, and see how they stacked up. With the cotyles scaled to the same vertical diameters, this is what we get for C9 and C10 of CM 3018 (lighter gray, background, traced from Gilmore 1936) vs CM 84/94 (darker gray, foreground, traced from Hatcher 1901):
The A. louisae verts are a hair taller, proportionally, than those of D. carnegii, but not by much. The difference is trivial compared to the differences in centrum length and cervical rib size.
So where did I get this apparently erroneous impression that Apatosaurus had giant neural spines? Maybe it’s not that the neural spines of apatosaurines in particular are so large, but rather than diplodocids of all types have large neural spines compared to non-diplodocids. Here are the same vertebrae compared for D. carnegii (dark gray, background) and Camarasaurus supremus (black, foreground, traced from Osborn and Mook 1921):
I deliberately picked the longest C9 in the AMNH collection, and the least-distorted C10. The first surprise for me was how well this C. supremus C9 hangs with D. carnegii in terms of proportions. That is one looooong Cam vert. In any other sauropod, it would probably be beautiful. But because it’s Camarasaurus it attained its length in the most lumpen possible way, with the diapophysis way up front, the neural spine apex way at the back, and in the middle just…more vertebra. Like a stretch limo made from a Ford Pinto, or Mike’s horrifying BOBA-horse.
Inevitable and entirely justified Cam-bashing aside, it’s striking how much smaller the whole neural arch-and-spine complex is in C. supremus than in D. carnegii. And remember that D. carnegii is itself a bit smaller than Apatosaurus, spine-wise. Is this maybe a diplodocoid-vs-macronarian thing, at least in the Morrison? Here’s the C10 stack with Brachiosaurus included, represented by BYU 12867 (which I think is probably a C10 based on both centrum proportions and neural spine shape – see Wedel et al. 2000b for details), and with labels added because it’s getting a little nuts:
I like this; it shows a lot. Here are some things to note:
- The diplodocids don’t just have taller neural spines, their pre- and postzygapophyses are also higher than in the macronarians. That’s gotta mean something, right? All else being equal, putting the zygs farther from the intervertebral joints would reduce the flexibility of the neck. Maybe diplodocoids could get away with it because they had more cervicals, or maybe their necks were stiffened for some reason.
- The zygs being set forward of their respective centrum ends in the macronarians really comes through here.
- The Brachiosaurus vert isn’t that different from a stretched (and de-uglified) Cam vert, with a slightly higher neural spine to help support the longer neck. (Maybe this is why Cam inspires such visceral revulsion: it reads as a failed brachiosaur.)
- This emphasizes the outlier status of Apatosaurus in the cervical rib department. It bears repeating: the cervical ribs of Camarasaurus are certainly wide, but they’re not nearly as massive or ventrally expanded as in apatosaurines.
So far, pretty interesting. I’d like to add Barosaurus and Haplocanthosaurus to round out the “big six” Morrison sauropods. I known Haplo has big, tall, almost apatosaurine neural spines (as shown above, with arrows highlighting the epipophyses), but for Baro I’d have to actually do the comparison to see where it falls out.
The idea of bringing in Barosaurus also forces the question, previously glossed over, of how legit it is to compare C10s of all these animals when their cervical counts differed. C. supremus is thought to have had 12 vertebrae in its neck, Brachiosaurus 13 (based on Giraffatitan), A. louisae and D. carnegii 15, and Barosaurus probably 16. It would be more informative to graph neural spine height divided by cotyle diameter along the column for all of these critters, plus Kaatedocus and Galeamopus. But that’s a lot of actual work, and as much fun as it sounds (really, I’d rather be doing that), I have summer teaching to prep for and field gear to wrangle. So I’ll have to revisit this stuff another time.
References
- Gilmore Charles W. 1936. Osteology of Apatosaurus, with special reference to specimens in the Carnegie Museum. Memoirs of the Carnegie Museum 11:175–300 and plates XXI–XXXIV.
- Hatcher, John Bell. 1901. Diplodocus (Marsh): its osteology, taxonomy, and probable habits, with a restoration of the skeleton. Memoirs of the Carnegie Museum 1:1-63.
- Osborn, Henry Fairfield, and Charles C. Mook. 1921. Camarasaurus, Amphicoelias and other sauropods of Cope. Memoirs of the American Museum of Natural History, n.s. 3:247-387, and plates LX-LXXXV.
- Taylor, Michael P., and Mathew J. Wedel. 2013. Why sauropods had long necks; and why giraffes have short necks. PeerJ 1:e36. 41 pages, 11 figures, 3 tables. doi:10.7717/peerj.36
- Wedel, M.J., and Sanders, R.K. 2002. Osteological correlates of cervical musculature in Aves and Sauropoda (Dinosauria: Saurischia), with comments on the cervical ribs of Apatosaurus. PaleoBios 22(3):1-6.
- Wedel, M.J., Cifelli, R.L., and Sanders, R.K. 2000b. Osteology, paleobiology, and relationships of the sauropod dinosaurSauroposeidon. Acta Palaeontologica Polonica 45(4): 343-388.
Work on the Archbishop begins!
May 28, 2018
I know, I know — you never believed this day would come. And who could blame you? Nearly thirteen years after my 2005 SVPCA talkSweet Seventy-Five and Never Been Kissed, I am finally kicking the Archbishop descriptive work into gear. And I’m doing it in the open!
In the past, I’ve written my academic works in LibreOffice, submitted them for peer-review, and only allowed the world to see them after they’ve been revised, accepted and published. More recently, I’ve been using preprints to make my submitted drafts public before peer review. But there’s no compelling reason not to go more open than that, so I’ll be writing this paper out in the open, in a public GitHub repository than anyone can access. That also means anyone can file issues if they thing there’s something wrong or missing, and anyone can submit pull-requests if they have a correction to contribute.
I’ll be writing this paper in GitHub Flavoured Markdown so that it displays correctly right in the browser, and so that patches can be supported. That will make tables a bit more cumbersome, but it should be manageable.
Anyway, feel free to follow progress at https://github.com/MikeTaylor/palaeo-archbishop
The very very skeletal manuscript is at https://github.com/MikeTaylor/palaeo-archbishop/blob/master/archbishop-manuscript.md
Remember this broken Giraffatitan dorsal vertebra, which Janensch figured in 1950?
It is not only cracked in half, anteroposteriorly, it’s also unfused.
Here’s a better view of the broken face, more clearly showing that the neural canal is (a) much taller than wide – unlike all vertebrate spinal cords – and (b) almost entirely situated ventral to the neurocentral joint, getting close to the condition in the perverted Camarasaurus figured by Marsh.
Here’s a dorsal view, anterior to the top, with Mike’s distal forelimbs for scale.
Left lateral view.
Right lateral view – note the subtle asymmetries in the pneumatic foramen/camera. A little of that might be taphonomic distortion but I think much of it is real (and expected, most pneumatic systems produce asymmetries).
And postero-dorsal view, really showing the weird neural canal to good advantage. In this photo and in the pure dorsal view, you can see that the two platforms for the “neural arch” – which, as in the aforementioned Camarasaurus, is neither neural nor an arch – converge so closely as to leave only a paper-thin gap.
A few points arise. As explained in this post, it makes more sense to talk about the neurocentral joint migrating up or down relative to the neural canal, which is right where it always is, just dorsal to the articular faces of the centrum.
So far, in verts I’ve seen with “offset” neurocentral joints, the joint tends to migrate dorsally in dorsal vertebrae, putting the canal inside the developmental domain of the centrum (which now includes a partial or total arch in an architectural sense, even though the chunk of bone we normally call the neural arch develops as a separate bit) – as shown in the first post in this series. In sacral and caudal vertebrae, the situation is usually reversed, with the joint shifted down into what would normally be the centrum, and the canal then mostly or completely surrounded by the arch – as shown in the second post in the series. This post then doesn’t really add any new concepts, just a new example.
Crucially, we can only study this in the vertebrae of juveniles and subadults, because once the neurocentral joints are fused and remodeled, we usually can’t tell where the old joint surface was. So it’s like cervicodorsal and caudal dorsal pneumatic hiatuses, in that the feature of interest only exists for part of the ontogeny of the animal, and our sample size is therefore inherently limited. Not necessarily limited by material – most museums I’ve visited have a fair amount of juvenile and subadult material in the collections – but limited in published visibility, in that for many sauropods only the largest and most complete specimens have been monographically described.
So once again, the answer is simply to visit collections, look at lots of fossils, and stay alert for weird stuff – happily, a route that is open to everyone with a legitimate research interest.
Reference
- Janensch, W. 1950. Die Wirbelsaule von Brachiosaurus brancai. Palaeontographica (Suppl. 7) 3:27-93.
Sauroposeidon, the early years: my first drawing
February 7, 2018
As part of a major spring cleaning operation that we started the first week of January, this week I opened the last two boxes left over from when we moved into our current house. One of them had a bundle of framed art. I knew most of what was in there before I opened the box, but I had somehow completely forgotten about this. I must have gotten it framed in late 90s, and it hung on the walls of our apartments in Norman and Santa Cruz. At some point it went into a box, and I forgot it even existed.
This is the first technical drawing I ever attempted of OMNH 53062, which would later become the holotype of Sauroposeidon. I drew it for my poster at the 1997 SVP meeting in Chicago, and it went on to become Figure 5 in my undergraduate thesis (which is preserved for posterity here). I’d do other, better drawings of the specimen in later years, but this one came first.
I know I’m biased, but that second vertebra in the preserved series, which I interpreted as C6 back when, will probably always be the most gorgeous natural object on the planet in my book. I don’t expect anyone else to feel the same. I worked on that specimen for three years – some of it seeped into my soul, and vice versa. Then again, I don’t care how jaded you are about long vertebrae, that one is still a pretty arresting sight.
For a much more recent take on the appearance of the Sauroposeidon vertebrae, see this post.
When I was nine, a copy of Don Glut’s The New Dinosaur Dictionary turned up in my local Waldenbooks. It wasn’t my first dinosaur book, by far – I’d been a dinosaurophile since the age of three. But The New Dinosaur Dictionary was different.
Up to that point, I had subsisted on a heavy diet of kids’ dino books and the occasional article in National Geographic and Ranger Rick. The kids’ books were aimed at kids and the magazine articles were pitched at an engagingly popular level. I didn’t understand every word, but they were clearly written for curious layfolk, not specialists.
A typical spread from The New Dinosaur Dictionary (Glut, 1982). The armored sauropod blew my young mind.
The New Dinosaur Dictionary was something else entirely. It had photos of actual dinosaur bones and illustrations of skeletons with cryptic captions like, “Skeleton of Daspletosaurus torosus. (After Russell)”. Okay, clearly this Russell cove was out there drawing dinosaur skeletons and this book had reproduced some of them. But nobody I knew talked like that, and the books I had access to up to that point held no comparable language.
The New Dinosaur Dictionary (Glut, 1982: p. 271)
Then there was stuff like this: “The so-called Von Hughenden sauropod restored as a brachiosaurid by Mark Hallett”. A chain of fascinating and pleasurable ideas detonated in my brain. “The so-called” – say what now? Nobody even knew what to call this thing? Somehow I had inadvertently sailed right to the edge of human knowledge of dinosaurs, and was peering out into taxa incognita. “Restored as a brachiosaurid” – so this was just one of several possible ways that the animal might have looked. Even the scientists weren’t sure. This was a far cry from the bland assurances and blithely patronizing tones of all my previous dinosaur books.
“By Mark Hallett.” I didn’t know who this Hallett guy was, but his art was all over the book, along with William Stout and some guy named Robert T. Bakker and a host of others who were exploding my conception of what paleo art could even be. Anyway, this Mark Hallett was someone to watch, not only because he got mentioned by name a lot, but because his art had a crisp quality that teetered on some hypercanny ridge between photorealism and scribbling. His sketches looked like they might just walk off the page.
In case that line about scribbling sounds dismissive: I have always preferred sketches by my favorite artists to their finished products. The polished works are frequently inhumanly good. They seem to have descended in a state of completed perfection from some divine realm, unattainable by mere mortals. Whereas sketches give us a look under the hood, and show how a good artist can conjure light, shadow, form, weight, and texture from a few pencil strokes. Put it this way: I am anatomist by temperament first, and by training and occupation second. Of course I want to see how things are put together.
The New Dinosaur Dictionary (Glut, 1982: p. 75)
Anyway, The New Dinosaur Dictionary was something completely new in my experience. It wasn’t aimed at kids and written as if by kids, like lots of kids’ books. It wasn’t even written by adults talking down (deliberately or inadvertently) to kids, or trying to reach a wide audience that might include kids. It was written by an adult, aiming at other adults. And it was admitting in plain language that we didn’t know everything yet, that there were lots of animals trembling on the outer threshold of scientific knowledge. I didn’t understand half of it – I was down in an ontogenetic trench, looking up as these packets of information exploded like fireworks over my head.
In Seeing In the Dark, the best book about why you should go out stargazing for yourself, Timothy Ferris writes about growing up on Florida’s Space Coast in the early 1960s, and watching the first generation of artificial satellites pass overhead:
I felt like an ancient lungfish contemplating the land from the sea. We could get up there.
That’s precisely the effect that The New Dinosaur Dictionary had on me: I could get up there. Maybe not immediately. But there were steps, bodies of knowledge that could be mastered piecemeal, and most of all, mysteries to be resolved. The book itself was like a sketch, showing how from isolated and broken bones and incomplete skeletons, scientists and artists reconstructed the world of the past, one hypothesis at a time. Now I take it for granted, because I’ve been behind the curtain for a couple of decades. But to my 9-year-old self, it was revolutionary.
This has all come roaring back because of something that came in the mail this week. Or rather, something that had been waiting in the mailroom for a while, that I finally picked up this week: a package from Mark Hallett, enclosing a copy of his 2018 dinosaur calendar. And also this:
An original sketch, which he gave to me as a Christmas present. The published version appears on one of the final pages of our book, where we discuss the boundaries between the known – the emerging synthesis of sauropod biology that we hoped to bring to a broader audience by writing the book in the first place – and the unknown – the enduring mysteries that Mark and I think will drive research in sauropod paleobiology for the next few decades. Presented without a caption or commentary, the sketch embodies sauropods as we see them: emerging from uncertainty and ignorance one hard-won line at a time, with ever-increasing solidity.
Thank you, Mark, sincerely. That sketch, what it evokes, both for me now and for my inner 9-year-old – you couldn’t have chosen a better gift. And I couldn’t be happier. Except perhaps to someday learn that our book exploded in the mind of a curious kid the way that The New Dinosaur Dictionary did for me 34 years ago, a time that now seems as distant and romantic as the primeval forests of the Mesozoic.
Paul Graham on blogging as a way to generate papers
January 16, 2018
Computer programmer, essayist and venture capitalist Paul Graham writes:
In most fields, prototypes have traditionally been made out of different materials. Typefaces to be cut in metal were initially designed with a brush on paper. Statues to be cast in bronze were modelled in wax. Patterns to be embroidered on tapestries were drawn on paper with ink wash. Buildings to be constructed from stone were tested on a smaller scale in wood.
What made oil paint so exciting, when it first became popular in the fifteenth century, was that you could actually make the finished work from the prototype. You could make a preliminary drawing if you wanted to, but you weren’t held to it; you could work out all the details, and even make major changes, as you finished the painting.
You can do this in software too. A prototype doesn’t have to be just a model; you can refine it into the finished product. I think you should always do this when you can. It lets you take advantage of new insights you have along the way. But perhaps even more important, it’s good for morale.
– Paul Graham, “Design and Research”
Mike and I have long been drawn by the idea that blog posts, like conference talks and posters, could be first drafts of research papers. In practice, we haven’t generated many successful examples. We basically wrote our 2013 neural spine bifurcation paper as a series of blog posts in 2012. And Mike’s 2014 neck cartilage paper grew out of this 2013 blog post, although since he accidentally ended up writing 11 pages I suppose the blog post was more of a seed than a draft.
I should also note that we are far from the first people to do the blog-posts-into-papers routine. The first example I know of in paleo was Darren’s Tet Zoo v1 post on azhdarchid paleobiology, which formed part of the skeleton of Witton and Naish (2008).
Nevertheless, the prospect of blogging as a way to generate research papers remains compelling.
And as long as I’m on about blogging and papers: sometimes people ask if blogging doesn’t get in the way of writing papers. I can’t speak for anyone else, but for me it goes in the opposite direction: I blog most when I am most engaged and most productive, and drops in blogging generally coincide with drops in research productivity. I think that’s because when I’m rolling on a research project, I am constantly finding or noticing little bits that are cool and new, but which aren’t germane to what I’m working on at the moment. I can’t let those findings interfere with my momentum, but I don’t want to throw them away, either. So I blog them. Also the blog gives me a place to burn off energy at the end of the day, when I can still produce words but don’t have the discipline to write technical prose.
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The photo at the top of the post is of Giraffatitan dorsal vertebrae in a case at the MfN Berlin, from Mike’s and my visit with the DfG 533 group back in late 2008. I picked that photo so I could make the following dumb off-topic observation: with its upturned transverse processes, the dorsal on the right looks like it’s being all faux melodramatic, a la:
This post started out as a comment on this thread, kicked off by Dale McInnes, in which Mike Habib got into a discussion with Mike Taylor about the max size of sauropods. Stand by for some arm-waving. All the photos of outdoor models were taken at Dino-Park Münchehagen back in late 2008.
I think it’s all too easy to confuse how big things do get from how big they could get, assuming different selection pressures and ecological opportunities. I’m sure someone could write a very compelling paper about how elephants are as big as they could possibly be, or Komodo dragons, if we didn’t have indricotheres and Megalania to show that the upper limit is elsewhere. This is basically what Economos (1981) did for indricotheres, either forgetting about sauropods or assuming they were all aquatic.
Truly, a mammal of excellence and distinction. With Mike and some dumb rhino for scale.
In fact, I’ll go further: a lot of pop discussions of sauropod size assume that sauropods got big because of external factors (oxygen levels, etc.) but were ultimately limited by internal factors, like bone and cartilage strength or cardiovascular issues. I think the opposite is more likely: sauropods got big because of a happy, never-repeated confluence of internal factors (the Sander/et al. [2008, 2011, 2013] hypothesis, which I think is extremely robust), and their size was limited by external, ecological factors.
Take a full-size Argentinosaurus or Bruhathkayosaurus – even modest estimates put them at around 10x the mass of the largest contemporary predators. Full-grown adults were probably truly predator-immune, barring disease or senescence. So any resources devoted to pushing the size disparity higher, instead of invested in making more eggs, would basically be wasted.
If there was reproductive competition among the super-giants, could the 100-tonners have been out-reproduced by the 70-tonners, which put those extra 30 tonnes into making babies? Or would the 100-tonners make so many more eggs than the 70-tonners (over some span of years) that they’d still come out on top? I admit, I don’t know enough reproductive biology to answer that. (If you do, speak up in the comments!) But if – if – 70-tonners could out-reproduce 100-tonners, that by itself might have been enough to put a cap on the size of the largest sauropods.
Another possibility is that max-size adult sauropods were neither common nor the target of selection. In most populations most of the time, the largest individuals might have been reproductively active but skeletally-immature and still-growing subadults (keep in mind that category would encompass most mounted sauropod skeletons, including the mounted brachiosaurs in Chicago and Berlin). If such individuals were the primary targets of selection, and they were selected for a balance of reproductive output and growth, then the few max-size adults might represent the relatively rare instances in which the developmental program “overshot” the selection target.
Dave Hone and Andy Farke and I mentioned this briefly in our 2016 paper, and it’s come up here on the blog several times before, but I still have a hard time wrapping my head around what that would mean. Maybe the max-size adults don’t represent the selective optimum, but rather beneficial traits carried to extreme ends by runaway development. It seems at least conceivable that the bodies of such animals might have been heavily loaded with morphological excrescences – like 15- to 17-meter necks – that were well past the selective optimum. As long as those features weren’t inherently fatal, they could possibly have been pretty darned inefficient, riding around on big predator-immune platforms that could walk for hundreds of kilometers and survive on garbage.
What does that swerve into weird-but-by-now-well-trod ground have to do with the limits on sauropod size? This: if max-size adults were not heavy selection targets, either because the focus of selection was on younger, reproductively-active subadults, or because they’d gotten so big that the only selection pressure that could really affect them was a continent-wide famine – or both – then they might not have gotten as big as they could have (i.e., never hit any internally-imposed, anatomical or biomechanical limits) because nothing external was pushing them to get any bigger than they already were.
Or maybe that’s just a big pile of arm-wavy BS. Let’s try tearing it down, and find out. The comment thread is open.
References
- Economos, A.C. 1981. The largest land mammal. Journal of Theoretical Biology 89(2):211-214.
- Hone, D.W.E., Farke, A.A., and Wedel, M.J. 2016. Ontogeny and the fossil record: what, if anything, is an adult dinosaur? Biology Letters 2016 12 20150947; DOI: 10.1098/rsbl.2015.0947.
- Sander, P.M. and Clauss, M. 2008. Sauropod gigantism. Science 322(5899):200-201.
- Sander, P.M., Christian, A., Clauss, M., Fechner, R., Gee, C.T., Griebeler, E.M., Gunga, H.C., Hummel, J., Mallison, H., Perry, S.F. and Preuschoft, H. 2011. Biology of the sauropod dinosaurs: the evolution of gigantism. Biological Reviews 86(1):117-155.
- Sander, P.M. 2013. An evolutionary cascade model for sauropod dinosaur gigantism-overview, update and tests. PLoS One, 8(10) p.e78573.
