Were the biggest sauropods the most pneumatic?

March 19, 2008

giant-cervicals-compared-500.jpg

In a comment on the previous post, Amanda wrote:

This might be a stupid question (I don’t really believe that there are no such things as stupid quetions) but do you find that sauropod vertebrae are more highly pneumatic in larger sauropods?

This is not only not a dumb question, it is one of most important questions about pneumaticity in sauropods. The answer is complex, but here at SV-POW! we embrace the complexity. So here’s the dope: brachiosaurids had the most highly pneumatic vertebrae of anything that we’ve measured. Nobody’s gotten a mamenchisaur vert into a CT scanner, nor one from Supersaurus. I had a plan all worked out to do the latter, but at the last minute we realized that the darn thing wouldn’t fit through the scanner. Occupational hazard. And not much scanning has been done on titanosaurs, and none at all on the very big ones. So out of the four clades that produced real monsters–mamenchisaurs, diplodocids, brachiosaurs, and titanosaurs–we have hard data on the monsters themselves from only one. Diplodocids and the more derived titanosaurs did have pretty highly pneumatic vertebrae, but not all of them were big. Some were downright dinky. And there were some pretty big sauropods with only moderate pneumaticity, like Jobaria and Camarasaurus. But they weren’t the real monsters; neither of those critters probably topped 1/3 of the mass of the biggest sauropods we have fair remains for, let alone semi-apocryphal gigapods like Amphicoelias and Bruhathkayosaurus. In short, the picture ain’t clean.

Draw a square and divide it into four smaller squares. Label one axis with “Huge: Yes or No” and the other axis with “Highly pneumatic: Yes or No”, where “huge” means something in the 50+ ton range and highly pneumatic means something with more than 60% air in its verts. All of the boxes will be filled but one, which is the “Huge” and “Not highly pneumatic” one. There are small sauropods that were highly pneumatic, but so far no huge sauropods that weren’t, at least based on the evidence in hand.

It doesn’t work out so well statistically, despite what I said in my 2006 SVP abstract. The problem is that the statistical significance comes and goes depending on which taxa are included. That’s a big problem, because there aren’t very many taxa for which we have enough data to make doing the statistics worthwhile. And we have no crunchable numbers on most of the biggest sauropods, including Supersaurus and the biggest mamenchisaurs and titanosaurs, so even the lack of statistical significance in some of the tests might be just an artifact of undersampling the biggest and possibly most pneumatic taxa.

And there is a final caveat, which is that supposedly there is a 2.3 meter femur from the Early Jurassic of Morocco. Not much is known about this. It was mentioned but apparently not figured in one short paper published a while ago in French in a Moroccan journal that is exceedingly hard to get a hold of. If it is really from the Early Jurassic and it really is that big, that’s pretty amazing. A 2.3 meter femur is as big as that of the largest known brachiosaurids. It’s up there in Argentinosaurus country. But in the Early Jurassic it presumably represents something pretty basal, which presumably means something that is not highly pneumatic. You’ll notice that there are a lot of presumablys in there, but if that femur does represent a huge basal sauropod, then we would have to go back to our boxes and put an X in the last one, the “huge” and “not highly pneumatic” box. In which case, forget about any statistical correlation between size and pneumaticity. That giant eopod would be enough to wreck the correlation all by itself.

And I just remembered Turiasaurus, which I should have thought of sooner since I’ve seen the material (nyah nyah). The verts are a little mooshed but not bad. I’ve scanned worse. And the folks in Spain would like to scan it. My guess is that it will come about about like Camarasaurus, in the ~60% zone. It is probably the biggest sauropod with so little pneumaticity, except only the Moroccan monster, assuming my guess is correct (FWIW, when Mike’s tested me in the past my guesses about air space proportion have been pretty darn close).

So what’s the take home message? At least a few sauropods got rilly rilly big without being rilly rilly pneumatic. And at least some rilly rilly pneumatic sauropods were not particularly big. But the biggest sauropods that we know of also seem to be the most pneumatic.

There is another interesting pattern, having to do with neck length and internal complexity of the vertebrae, but I’m going to save that one for another post.

The picture shows the three largest cervical vertebrae of anything, ever, that anyone has found. Until somebody finds some more Amphicoelias fragillimus or Bruhathkayosaurus, this is as long as vertebrae are known to get. Sauroposeidon and Supersaurus are my own photos; Puertasaurus is after Novas et al. (2005:fig. 1). Each of those taxa–heck, each of those vertebrae–is due its own post one of these days, but for now just grok the immensity.

Reference

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29 Responses to “Were the biggest sauropods the most pneumatic?”

  1. Zach Miller Says:

    Very interesting. That Early Jurassic monster is titilating! Has it been named, or is it just based on a single bone?

  2. Matt Wedel Says:

    Titilating? It’s titanilating! No name, just the one bone, so far as I have been able to determine is it just the one mention with no photo, and nobody outside of Morocco knows where it is or even whether it was collected. It could have been eroding out of a hillside, and by now it could be part of a Saharan dune. I hope not. I brake for 2.3 meter femora.

  3. Nathan Myers Says:

    What is, er, was it about sauropod vertebrae that led them to be preserved while the ribs and tarsals evaporated? (I already understand that the skulls exploded on death, as a defensive measure. Apologies if this has been addressed already; my own skull may not survive either.)

  4. Matt Wedel Says:

    Dude, I wish like hell I knew. Take Sauroposeidon. Probably a 40 or 50 ton critter, with femora like seven-foot bars of fairly solid bone, and we have 3.5 very fragile vertebrae in perfect articulation. If the vertebrae got moved from the carcass, why are they in such good shape? They don’t have any bite marks or anything, no evidence on the bone of fluid transport. And I can’t really see dozens of tons of carcass getting dragged away from the neck. So it’s a mystery.

    Puertasaurus is equally weird but for a slightly different reason. There are two vertebrae from different parts of the animal. Okay, why vertebrae? Why not a humerus and a femur? If you’re rolling the dice on sauropod bits, big fragile vertebrae seem a lot less likely than big solid limb bones.

    Then there’s the Dry Mesa Supersaurus material, which includes loads of verts and not much else. I know, there are a few appendicular bits, but except for a handful of potentially pneumatic ilia, sauropod appendicular bits are apneumatic and verts are almost always pneumatic. So why do we get the fragile stuff so often with the big critters? Even Amphicoelias fragillimus. Where’s the four-meter femur? It’s a conspiracy, I tells ya.

    Seriously, I’m not holding out. I’m legitimately mystified. In the second Sauroposeidon paper we brought this up, pointed how damn weird it is, and then basically threw up our hands and went on to the next part of the manuscript. Not very satisfying, as an author or a researcher.

    You get any brainstorms, let us know. Seriously.

  5. Vertebrat Says:

    Thanks to the SV-POW tutorials, I think I can identify all of the sticky-out bits on these three vertebrae, except, uh… what’s going on at the back end of the Supersaurus vert? It looks like one huge lamina, with no cotyle or postzygapophyses in sight. Is the left postzygapophysis missing, so we’re looking at the right SPOL and CPOL? But then what happened to the cotyle? Or are those solid-looking things at the bottom the centrum? (But then why is there a huge hole in the bottom?)

    Or is this vertebra tilted, so the big lamina is the SPOL, and the things at the bottom are the postzygapophyses, and most of the centrum is just missing?

    Or maybe the neural spine is missing and the piece at the top is a postzygapophysis?

    What features should I be looking at to know which part is which?

  6. Vertebrat Says:

    Some of the shortage of big bones could be explained by the difficulty of transporting them after death. If big sauropods were tree-browsers, they’d tend to live and die in terrestrial forests and savannahs, which are not environments conducive to fossilization. Only the bits that got washed down a river would end up in sediment. But most of a sauropod is too big and heavy for that to happen much. “Seven-foot bars of fairly solid bone” aren’t going anywhere. Only the light parts are likely to be carried to the fossil beds.

    And what’s the lightest part of a sauropod? The hollow vertebrae.

    This would also explain why there’s so much sauropod material from swamps, like Paralititan, even though that doesn’t seem like a great environment for a big animal with small feet. A swamp is one of the few places a sauropod might plausibly die and be fossilized without being transported first.

    I wouldn’t think the good condition of vertebrae like Sauroposeidon‘s is much evidence against water transport. The kind of water transport that leaves scars is when an object is rolled along the bottom, but intact sauropod neck sections probably float, and rivers can be quite gentle to a floating object.

    The obvious test of this is whether the swamp sauropods really do preserve more heavy bones. Smaller sauropods also ought to be more easily transported, and thus be more complete. Are either of these actually observed?

    I also wonder if dorsal vertebrae would tend to remain attached to the carcass longer, and thus not be transported as readily as cervicals and caudals. Is the vertebra surplus just cervicals and caudals, or are there extra dorsals too?

  7. Mike Taylor Says:

    Hi, Vertebrat, thanks for your thoughts on differential preservation. What you suggest makes a certain amount of sense, but it won’t work for Sauroposeidon, whose three-and-a-half preserved vertebrae were perfectly articulated (not merely associated). Interesting stuff.

    Regarding your question about dorsals remaining attached longer than cervicals and caudals: empirically, it seems that isolated vertebrae (or pairs or short sequences) are about equally common from all three regions, so there doesn’t seem to be any differential preservation going on _along_ the axial column.

    What is really strange is there seems to be a taxonomic bias: Matt and I sometimes joke that if you find an isolated dorsal, it’s a brachiosaurid, but if you find an isolated caudal, it’s a titanosaur. And it really does seem to be that way — there are lots of crappy Wealden maybe-brachiosaurs named from dorsals, and lots of a titanosaurs from all over the world named from caudals.

    I think we might put this down to observer bias: an isolated brachiosaurid caudal is not a very striking object, whereas a titanosaur caudal is very characteristic — you really can’t mistake it for anything else. I am guessing plenty of collection have isolated brachiosaur caudals that no-one’s bothered to study.

  8. Darren Naish Says:

    Of possible relevance to the last point made by Mike there is that the rather nondescript caudal vertebrae of brachiosaur-type sauropods sometimes (perhaps regularly) get mistaken for those of other big Mesozoic reptiles. Exhibit A….

    Buffetaut, E., Colleté, C., Dubus, B. & Petit, J.-L. 2005. The “sauropod” from the Albian of Mesnil-Saint-Pere (Aube, France): a pliosaur, not a dinosaur. Carnets de Géologie / Notebooks on Geology – Letter 2005/01 (CG2005_L01).

  9. Amanda Says:

    Thanks Matt!

  10. Matt Wedel Says:

    I think I can identify all of the sticky-out bits on these three vertebrae, except, uh… what’s going on at the back end of the Supersaurus vert?

    It’s smashed. A bit. The cotyle is mashed down until it is about 5 times as tall as wide. And there are a couple of big posterior centroparapophyseal laminae hanging down off the centrum, which are themselves flat and blend into the bottom of the cotyle and exaggerate the apparent flatness. This vert by itself will get a post one of these days, and all will become clear.


  11. And there is a final caveat, which is that supposedly there is a 2.3 meter femur from the Early Jurassic of Morocco. Not much is known about this. It was mentioned but apparently not figured in one short paper published a while ago in French in a Moroccan journal that is exceedingly hard to get a hold of.

    In case anyone is interested, this reference is:

    Charroud, M., and Fedan, B. 1992. Données préliminaires sur la découverte du Gisement de Boulahfa a dinosauriens (SW de Boulemae, Moyen Atlas Cental). Notes et Mémoires du Service Géologique du Maroc 366:448-449.

    Actually, this specimen is Middle Jurassic (Bathonian), not Early Jurassic, per the paper. Anyway, apparently more than the femur was preserved — the paper refers continuously to “bones” (plural — e.g., “…[d]ans ce gisement, les ossements énormes sont très fréquents. Nous possédons déjà plus de 45 pièces dont; 2 os longs (fémurs) qui mesurent entre 230 et 240 cm, des têtes d’os longs en assez grand nombre, de grosses vertèbres dont le tour fait 60 à 80 cm. Ces ossements sont ceux du squelette d’un animal de très grandes dimensions: un femur mésure 236 cm.”

    Hmmmmm…I feel a grant proposal coming on — anyone wanna join me?


  12. Darn it…I forgot two things:

    (1) For anyone that can’t read French, that quote I provided says “…in this deposit, enormous bones are very common. We already have more than 45 bones including: 2 long bones (femora) that measure between 230-240 cm, a large number of heads of long bones, [and] large vertebrae with heights range from 60-80 cm. The bones are those of a very large animal: one femur measures 236 cm.”

    (2) Although it’s not nearly as surprising in the Cretaceous, we’ve got one that is barely shorter than this (222 cm) from the Maastrichtian of Patagonia:

    Lacovara, K., Harris, J., Lamanna, M., Novas, F., Martínez, R., and Ambrosio, A. 2004. An enormous sauropod from the Maastrichtian Pari Aike Formation of southernmost Patagonia. Journal of Vertebrate Paleontology 24(suppl. 3):81A.

    Might be the same as Puertasaurus, or might not… Anyway, also don’t forget that the femur of “Antarctosaurusgigantaeus was reported at 231 cm.

    And now, back to the vertebrae…

  13. Mike Taylor Says:

    Hey, Jerry — that does sound promising. Please go ahead and get a grant to excavate and describe this beast :-) When they are this big, we don’t mind discussing appendicular elements!

    Darren, I know there is some history of confusing sauropod and pliosaur vertebrae, but … isn’t that only when dealing with isolated centra? (It certainly is the Buffetaut et al. paper.) I know that brachiosaur proximal caudals are less pretty than those of titanosaurs, but there’re still somewhat characteristic.

  14. Vertebrat Says:

    It’s smashed.

    Oh, so that’s what that looks like. Thanks.

    Is Sauroposeidon‘s articulation really surprising, if it was transported gently and buried right away, before it had a chance to rot or get eaten? (Gently, apart from the neck presumably getting torn in half by some huge scavenger who then conveniently dropped it in a river without eating any?)

  15. Matt Wedel Says:

    Is Sauroposeidon’s articulation really surprising, if it was transported gently and buried right away, before it had a chance to rot or get eaten? (Gently, apart from the neck presumably getting torn in half by some huge scavenger who then conveniently dropped it in a river without eating any?)

    The short answer is simply “yes”. The long answer would require a post of its own, so that’s how I’m going to play it. And because this post started out as a promised answer to a question that came up in a comment, you know I’m good for it.

  16. Nathan Myers Says:

    I suppose vertebrae were quickly discovered by any predator or scavenger to have a very unpleasant mouth-feel — all splintery, with no meat to speak of. We have (or once had?) a modern analog: “Only Grandma will eat the turkey neck.”

  17. Matt Wedel Says:

    I suppose vertebrae were quickly discovered by any predator or scavenger to have a very unpleasant mouth-feel — all splintery, with no meat to speak of.

    It’s an interesting question. Extant birds are mostly so small that carnivores can just plow right through them, although eating the bones may not be wonderful for their digestive systems. But a big sauropod vertebra wouldn’t be a very appealing prospect. No marrow inside, just air, so you’re crunching up thin, splintery bone for nothing. They’d probably eat all the neck muscles off the outside, though, and the taphonomy of Sauroposeidon strongly suggests that it was buried with the muscles on. But now I’m getting ahead of myself again. W4TP (wait for the post, in this case).

    We have (or once had?) a modern analog: “Only Grandma will eat the turkey neck.”

    Around my family, it’s “Save the turkey neck for Matt”, because I always want more pneumatic vertebrae to play with.

  18. Asier Says:

    Anyway there are femurs larger than 2.3 metros, like the 2.55 m. predicted for the Argentinosaurus holotype and probably 2.7 m. for the other Argentinosaurus fossils. Sauroposeidon would have been more than 2.4 femur. The supersaurus holotype suggets a femur between 2.4 and 2.6 m.

    How long is Seismosaurus hallorum femur?

    Thanks

  19. Matt Wedel Says:

    Anyway there are femurs larger than 2.3 metros, like the 2.55 m. predicted for the Argentinosaurus holotype and probably 2.7 m. for the other Argentinosaurus fossils. Sauroposeidon would have been more than 2.4 femur. The supersaurus holotype suggets a femur between 2.4 and 2.6 m.

    …all of which are from the Late Jurassic or Cretaceous. What is exciting about the 2.3-meter femur from Morocco is that is the biggest sauropod anyone has found so far from the Middle Jurassic or earlier. I agree, if someone found a 2.3-meter femur from the Late Cretaceous of Patagonia it would not be nearly as exciting. But considering where and when this one is from, it’s pretty darn important. Which is why I wish we knew more about it.

  20. Nathan Myers Says:

    I’m sure I’m not alone in preferring “Upper Jurassic” and “Lower Cretaceous” to “Late Jurassic” and “Early Cretaceous”. Is there a story there?

  21. Graham King Says:

    It’s always good to hear of large new finds! (Or any).

    Do you palaeo types have private wish-lists… ideal discoveries you dream of? (A complete, articulated skeleton of [i]Deinocheirus mirificus[i] would be near top of my list… though it’s fun to be left to imagine, too).

    Re the neck-bitey stuff… my theory (which is mine) of the sauropod is that, to catch one, to eat, which as a predator one might wish to do… to do that, by FAR (sic) the best approach would be to quickly bite its head off, surprising it, because that is the thin weak bit, removal of which will most rapidly subdue it… avoiding risk of it rearing, clawing, trampling, tail-whipping, bellowing for reinforcements, etc. So I reckon an ‘ambush ‘n’ lunge’ approach would have characterised predators which preyed singly on sauropods.
    Maybe T-rex habitually hid among stands of sauropods’ known favourite trees? Was camouflaged accordingly? Had a knack for standing stock-still for long periods?

    Tests: check sauropod skulls and neck vertebrae for carnosaur-sized bite marks and embedded teeth…
    (shake them; if the pneumatic cavities rattle, a tooth may be within).

    This would explain why sauropod finds often lack one end.

    I suspect the meatier parts (limbs and body) would be most eagerly attended to by megacarnivores, possibly dismembered and carried off; whereas the axial skeleton would remain to be picked over later by lesser feeders once the carcass was opened up, and so might remain substantially intact.

    IMHO, FWIW!


  22. I’m sure I’m not alone in preferring “Upper Jurassic” and “Lower Cretaceous” to “Late Jurassic” and “Early Cretaceous”. Is there a story there?

    The terms “Upper” and “Lower” are used exclusively when referring directly to strata (rocks), as in “the Upper Jurassic Morrison Formation” — they are chronostratigraphic terms. “Early” and “Late” are used for time periods and entities that dwelled within them, regardless of what rocks were around (or being formed) at the time, as in “Apatosaurus lived during the Late Jurassic” or “the Lower Cretaceous Sauroposeidon.” (“Middle” applies equally in both cases.) Though it has been argued that there is no reason to retain this set of discreet terminologies (e.g., Zalasiewicz J, Smith A, Brenchly P, Evans J, Knox R, Riley N, Gale A, Gregory FJ, Rushton A, Gibbard P, Hesselbo S, Marshall J, Oates M, Rawson P & Trewin N 2004. Simplifying the stratigraphy of time. Geology 32:1-4), these arguments don’t consider why the dichotomy exists in the first place (e.g., this, this, this, and this. On a simpler note than these links, though, it’s pretty easy to remember: if you’re talking directly about rocks, use “Upper” and “Lower”; if you’re talking about anything else (organisms, time periods in general, etc.), use “Early” and “Late.”

  23. Nathan Myers Says:

    Thanks, Jerry, that was full of crunchy detail. Not just a story, but a controversy.

    Me, I’m always talking about the rocks.


  24. [...] was spending a little quality time with the Dry Mesa Supersaurus cervical. You’ve seen it here before so you know it’s dimensions…sorta. As I am always saying, there is a big [...]


  25. [...] just to keep things in perspective. The entire neck of Miragaia might have been about as long as one of the middle cervicals of Sauroposeidon or [...]


  26. [...] The big vertebra was obviously cervical 8 of Sauroposeidon, which you’ve seen here more than once. The small vertebra is also a mid-cervical, also from the Early Cretaceous, but from Croatia [...]


  27. [...] for the record: C8 of the Sauroposeidon holotype OMNH 53062 is slightly longer overall, at 140 cm. But that includes overhanging prezygapophyses. Its centrum is “only” 125 cm [...]


  28. […] shown to scale, in right lateral view. These are not the biggest sauropod cervical vertebrae–Supersaurus beats them all, and there are vertebrae of Puertasaurus, Alamosaurus, and Futalognkosaurus that rival the big […]


  29. […] 4-3). At 1400 mm, the longest vertebra of Sauroposeidon is marginally longer in total length [see this post for a visual comparison]. However, that length includes the prezygapophyses, which overhang the […]


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