Prosauropod pneumaticity strikes back
March 12, 2011
UPDATE April 16, 2012: The paper is officially published now. I’ve updated the citation and link below accordingly.
More new goodies:
This is only kinda sorta published. The accepted manuscript is now posted on the APP website, and it has a DOI, but it’s not formatted or available in print yet. But after discussing it amongst ourselves, we authors agreed that (1) the paper is globally available and it’s silly to pretend otherwise, (2) there are no nomenclatural ramifications of that fact, and (3) we’re tired of not being able to talk about this stuff. So we’re gonna, starting…now.
A brief tale of Serendipity in Science (TM):
Back in 2004 I was in my third year of grad school at Berkeley. My fellow grad student, Brian Kraatz, gave me a heads up about the 19th International Congress of Zoology coming up in Beijing. Attendees could submit 500-word abstracts or 2000-word short papers. I didn’t plan on doing either one, until the night before they were due, when I changed my mind and wrote almost all of what would become this paper in a single six-hour session (don’t be too impressed; I’ve been trying to replicate that feat for seven years with no success).
That summer, I met up with Brian in Beijing a week before the congress, and we spent the extra time working in the collections of the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP). Paul Barrett was there, working on prosauropods, and he and I had some long and fascinating conversations. We also gave our talks in the same session at the congress. Paul must have decided I was not a complete moron because he invited me to give a talk in the basal sauropodomorph symposium at SVP in 2005.
A brief aside: many of the animals I grew up calling prosauropods ended up outside of the monophyletic Prosauropoda that is anchored on Plateosaurus. Some are now basal sauropods, some are closer to sauropods than to Plateosaurus but outside of Sauropoda, and some are outside of Prosauropoda + Sauropoda. The phylogenetically correct term encompassing all of the nonsauropods is ‘basal sauropodomorphs’, and it means roughly what ‘prosauropods’ did until a decade or so ago. I often slip into informally using ‘prosauropods’, but I try to remember to put the term in quotes so as not to mislead anyone.
I had been to England in 2004 and 2005 and seen the putatively pneumatic vertebrae of Erythrosuchus and what was then known as Thecodontosaurus caducus (and is currently trading under the name Pantydraco caducus for reasons that it would be otiose, for the moment, to rehearse)–and, not incidentally, had finally met Mike in person, although we’d been corresponding since 2000. I’d also been to Stuttgart primarily to see the appendicular material of Janenschia and ended up spending some quality time with Plateosaurus. (Since the theme here is serendipity, note that the Janenschia work–my raison d’etre for going to Germany–died on the table, whereas I’ve now been an author on three ‘prosauropod’ papers and have more in the works. Weird!)
Anyway, with all of that accidental experience with ‘prosauropods’ and other interesting critters like Erythrosuchus, I found that I actually had something to say in 2005 SVP symposium. I titled my talk, ‘What pneumaticity tells us about “prosauropods”, and vice versa’, and it turned into the 2007 paper of the same title.
None of this would have happened if Brian hadn’t hounded me about going to Beijing, and if I hadn’t ended up talking so much with Paul on that trip, and if I hadn’t finished up with Janenschia on my first day in Stuttgart and spent the rest of the week playing with Plateosaurus. And so on. Science is unpredictable, especially for scientists.
When I sent around the PDF of the paper to friends and colleagues, I included this quip: “Were prosauropods pneumatic? The fossils don’t say. Somehow I stretched that out to 16 pages.” Mike claims that because of this quip he’s never been able to take that paper seriously. But it is my favorite among my solo efforts. It includes loads of stuff on the origins of air sacs and pneumaticity that I wasn’t able to get into my earlier papers, either because it wasn’t directly relevant or because some reviewer forced me to excise it.
BUT.
Almost immediately after the paper came out, Adam Yates and Matt Bonnan went and found roughly a zillion pneumatic ‘prosauropods’, which was a bit embarrassing since I’d just concluded that the evidence for ‘prosauropod’ pneumaticity was thin to nonexistent. So it is a damn good thing for me that I was already on friendly terms with both of them, because instead of taking the opportunity to smack me down, they invited me on board. Which led to Adam’s talk at SVP in Bristol in 2009, and to the new paper.
And actually, the depth of my incorrectness was even greater than I had thought. I reckon that literally millions of people have seen the mounted Plateosaurus skeleton in the AMNH, and any of them who have looked closely have seen this:
(Click for full size, unlabeled version.)
You see the problem here, I’m sure: the semi-big, semi-obvious fossa divided by an accessory lamina, not consistent with a muscle attachment point or fat pad or cartilage or infection, but very consistent in both form and location with the pneumatic fossae of other, more derived sauropodomorphs. On the lateral face of the vertebra, probably seen by millions, obvious to anyone who cares to look. A pneumatic prosauropod, in other words, right out in public for decades and decades (this time I don’t have to use the scare quotes because Plateosaurus actually IS a prosauropod sensu stricto). I didn’t even notice the first time I visited the AMNH back in 2006. I took the above photos, which are the basis for Figure 4 in the paper, in 2009.
So: ‘prosauropods’ were pneumatic. Some of them. A little bit. If you’d like to know more, please read the paper–it’s free.
Finally, a big thank-you to Adam and Matt for inviting me to be part of this. I think it’s pretty cool stuff, and I’m sure I’ll have more to say about it in the future. They might too–you should be reading their blogs, Dracovenator and Jurassic Journeys, anyway.
We’re still not done with Brontomerus, by the way. If nothing else, there’s the long-overdue post on how sauropod ilia change (or rather fail to change) through ontogeny. But that’s something we’ll have to get back to next week. Stay tuned.
Sauropod Vertebra Picture of the Week 
March 12, 2011 at 2:43 am
[…] all things pneumatic, would find this very interesting, as indeed he did. If you go to his blog (SVPoW) he shows a picture of the “prosauropod” Plateosaurus he took awhile back at the […]
March 12, 2011 at 5:13 am
I’ve long assumed that some of these buggers were pneumatic and assumed that someone would get around to showing it or a fossil would pop up with it. Obviously I wasn’t going to bury myself in non-sauropodan sauropodomorphs to see if I was right, so I’m really pleased you guys have done it. Col stuff!
March 12, 2011 at 6:06 am
Obviously I wasn’t going to bury myself in non-sauropodan sauropodomorphs to see if I was right, so I’m really pleased you guys have done it.
Thanks, but that almost made me snort my drink on the keyboard. :-) I have certainly seen papers that made me sigh with relief and think, “Whew, I’m glad those poor bastards took care of that, because it needed doing but I sure didn’t want to tackle it!”
March 12, 2011 at 7:47 am
Its too bad Dave – when you were in China you had a chance to look at all those obscure Chinese basal sauropodomorphs! I bet some of them definitely show PSP.
March 12, 2011 at 3:50 pm
The question at this point, though, is why did pneumaticity disappear in cetiosaur-grade sauropods only to reappear in neosauropods?
Or were Cetiosaurus and Company more pneumatic than I’m aware of?
March 12, 2011 at 6:44 pm
The question at this point, though, is why did pneumaticity disappear in cetiosaur-grade sauropods only to reappear in neosauropods?
Or were Cetiosaurus and Company more pneumatic than I’m aware of?
I think they were all pneumatic. In ‘prosauropods’, and then again in derived neosauropods, it’s easy to see the pneumatic fossae because the vertebra has a corpus of bone that they are impressed into. In between, in animals like Cetiosaurus and Haplocanthosaurus, there are no big blocks of bone in the neural arches and spines, just slabs of intersecting laminae (see the first image in this post). These laminae are homologous with those of other sauropods, which do bound irregular, subdivided, clearly pneumatic fossae. My hypothesis is that sauropod pneumaticity went through four broad evolutionary phases:
1. In ‘prosauropods’ and the most basal sauropods, the bulk of each vertebra was a block of apneumatic bone, and the relatively small pneumatic fossae impressed into those blocks of bone are easy to see and interpret.
2. In the ‘cetiosaur-grade’ animals you’re discussing, pneumatization of the neural arch and spine had gone far enough that everything above the centrum was reduced to thin plates of bone. Pneumaticity wasn’t absent–on the contrary, pneumatization had removed enough bone that there were no more blocks of bone against which the fossae would be obvious. I think that in these animals, that’s all you get: laminae, and vast, usually unornamented fossae in between them. Pneumatization of the centrum in these animals is variable, but usually manifests as very shallow fossae, as in Barapasaurus and Cetiosaurus.
3. In most neosauropods, pneumatic structures are more complex. In diplodocids and brachiosaurs, for example, the vertebrae often have subfossae and embossed laminae (as discussed in the post linked above), and there are genuine internal chambers in both the centrum (commonly) and the neural arch and spine (occasionally). I don’t know why these changes happened, but I note that pneumaticity is pretty simple in dicraeosaurids and Europasaurus (pers. obs.), so maybe it’s mostly or entirely size-related.
4. Finally, in most titanosaurs the vertebrae are inflated from within with a honeycomb of internal cavities, and the external fossae are reduced in size. Since the neural arches and spines aren’t reduced to intersecting flat laminae anymore, it’s easier to see that the fossae are excavated out of (or impressed into) a block of bone. In some ways, the fossae of these very derived sauropods are similar to those of ‘prosauropods’ and basal sauropods, only instead of being impressed into a block of apneumatic bone, they’re impressed into a block of pneumatic bone.
Hmm. I should probably put this into a paper sometime.
Anyway, did that answer your question, or only stir the murk?
March 12, 2011 at 9:16 pm
I think that answered it. At that stage, the pneumaticity just didn’t leave obvious evidence, which explains why a lot of books erroneously say things like “Cetiosaurus had solid bones, unlike its later relatives”
March 13, 2011 at 1:32 am
“Its too bad Dave – when you were in China you had a chance to look at all those obscure Chinese basal sauropodomorphs! I bet some of them definitely show PSP.”
Well that rather assumes that a) I had the time (which I didn’t) and b) had the access to most of those more interesting specimens (which I didn’t) and c) had the motivation to really bury myself in basal sauropod PSP in order to find out (which I didn’t). ;-)
There’s a million and one things I wanted to do in China and didn’t / couldn’t and this as pretty low on the list to be honest. Plus I already knew Oli Rauhut and Paul Barrett were looking at these kinds of issues.
March 13, 2011 at 7:56 am
Interesting stuff. I have a hunch that Camelotia might also have some PSP, but the specimens need preparation to check this out. Neither Paul Upchurch nor I spotted any obvious PSP in either Lufengosaurus or Yunnanosaurus, but that observation is based only on the types, which are both missing at lot of the cervical arches. Will be checking out Lufengosaurus again in a couple of weeks…
March 14, 2011 at 12:49 pm
Oh bloody hell!! I have LECTURED more than once in front of that specimen and never noticed it!
“Derp” indeed!
March 14, 2011 at 2:51 pm
Tom, I promise, however great your chagrin, mine is unfathomably deeper. *cringe*
March 15, 2011 at 6:09 am
Matt, if we all remained cringed when we realised we had massively overlooked something it seems almost impossible to miss, none of us would leave the foetal position. You can at least be grateful that you guys spotted it. I’m sure there are other colleagues who can’t believe that they missed it either.
Dave
March 16, 2011 at 3:43 am
Double plus good!
March 16, 2011 at 5:05 am
[…] exchange of comments on this recent SV-POW! post was in good fun, but it masked an actual issue within research that’s worth making note of. […]
March 17, 2011 at 12:01 am
[…] weeks ago, Matt’s had the rather bad manners to post about another new paper of his — a review of prosauropod pneumaticity which might be uncharitably summarised as “Were prosauropods pneumatic? The fossils say […]
March 18, 2011 at 11:56 am
[…] heels came the long awaited basal sauropodomorph pneumaticity paper which has already showcased on SV-POW and Jurassic Journeys. Just this week has seen the electronic publication of a third paper of mine, […]
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[…] Yates et al. on prosauropod pneumaticity, it is “out” in the sense that the manuscript has been through peer review, has been […]
January 16, 2013 at 10:14 am
[…] you look very carefully, down at the bottom, you can see the same vertebra, C8, of the prosauropod Plateosaurus. […]
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[…] students), plus important singleton papers like Woodward and Lehman (2009), Cerda et al. (2012), Yates et al. (2012), and Fanti et al. (2013). Not to mention my own work, and some of Mike’s and […]
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