Weren’t we just discussing the problem of keeping up with all the good stuff on da intert00bz? The other day Rebecca Hunt-Foster, a.k.a. Dinochick, posted a “mystery photo” that is right up our alley here at SV-POW!, but, lazy sods that we are, we missed it until just now. Here’s the pic:


I flipped it 90 degrees so that you can see more clearly what is going on. This is a cut and polished section of a pneumatic sauropod vertebra–the bottom half of the mid-centrum of a dorsal vertebra, to be precise. Cervicals usually have concave ventral surfaces, and sacrals are usually either wider and flatter or narrower and V-shaped in cross sections, so I am pretty confident that this slice is from a dorsal. Compare to the classic anchor cross-section in this Camarasaurus dorsal:

camarasaurus-internal-structure(You may remember this image from Xenoposeidon week–almost two years ago now!)

Naturally as soon as I saw ReBecca’s shard of excellence, I wondered about its ASP, so after a bit of GIMPing, voila:

IMG_7857 ASP

As usual, bone is black, air is white, and everything else is gray. And the ASP is:

461080 white pixels/(461080 white + 133049 black pixels) = 0.78

So, we know what this is, and we know the ASP of this bit of it, and we can even figure out the in vivo density of this bit. The density of cortical bone ranges from about 1.8  g/cm^3 for some birds to about 2.0 for most mammals. For the sake of this example–and so I can hurry back to writing my lecture about the arse–let’s call it 1.9. The density is then the fraction of bone multiplied by the density of bone, full stop. If it was an apneumatic bone, we’d have to add the fraction of marrow multiplied by the density of marrow, but the density of air is negligible so we can skip that step here. The answer is 0.22 x 1.9 = 0.42 g/cm^3, which is pretty darned light. Keep in mind, though, that some slices of Sauroposeidon (and ‘Angloposeidon’, as it turns out) have ASPs of 0.89, and thus had an in vivo density half that of the above slice (0.11 x 1.9 = 0.21 g/cm^3).

What’s that in real money? Well, your femora are roughly 60% bone and 40% marrow, with a density of ((0.6 x 2.0)+(0.4 x 0.93)) = 1.6 g/cm^3, four times as dense as the bit of vertebra shown above, and eight times as dense as some slices of Sauroposeidon and ‘Angloposeidon’. If that doesn’t make you self-conscious about your heavy thighs, I don’t know what will.

Yes, that was a lame joke, and yes, I’m going out on it.

Hat tip to Dinochick.

P.S. It’s the 40th anniversary of the first moon landing today. Hoist a brew for Neil and Buzz, wouldja?


By now you’ll recognize this as NHM 46870, a minor celebrity in the world of pneumatic sauropod vertebrae. Darren has covered the history of the specimen before, and in the last post he showed photographs of both this chunk and its other half. He also briefly discussed the Air Space Proportion (ASP) of the specimen, and I’ll expand on that now.

People have mentioned the weight-saving properties of sauropod vertebrae from the very earliest discoveries of sauropods. But as far as I know, no one tried to quantify just how light they might have been until 2003.

That fall I was starting my third year of PhD work at Berkeley, and I was trying to think of everything that could possibly be investigated about pneumaticity in sauropod vertebrae. I came up with a list of four things:

  • external traces of pneumaticity (foramina, fossae, tracks, laminae)
  • form and complexity of internal spaces (camerae, camellae, branching patterns)
  • ratio of bone to air space within a pneumatic element
  • distribution of postcranial skeletal pneumaticity (PSP) in the body

That list of four things formed the outline for my first dissertation chapter (Wedel 2005), and for my dissertation itself. In fact, all of my papers that have anything to do with pneumaticity can be classified into one or more of those four bins:

That list is not exhaustive. It’s every aspect of PSP that I was able to think of back in 2003, but there are lots more. For example, I’ve only ever dealt with the internal complexity of sauropod vertebrae in a qualitative fashion, but the interconnections among either chambers or bony septa could be quantified, as Andy Farke has done for the frontal sinuses of hartebeests (Farke 2007). External traces on vertebrae and the distribution of PSP in the body can also be quantified, and were shortly after I drew up the list–see Naish et al. (2004) for a simple, straightforward approach to quantifying the extent of external pneumatic fossae, and O’Connor (2004, 2009) for a quantitative approach to the extent of pneumaticity in the postcranial skeletons of birds. There are undoubtedly still more parameters waiting to be thought of and measured. All of these papers are first steps, at least as applied to pneumaticity, and our work here is really just beginning.

Also, it took me an embarrassingly long time to “discover” ASPs.  I’d had CT slices of sauropod vertebrae since January, 1998, and it took me almost six years to realize that I could use them to quantify the amount of air inside the bones. I later discovered that Currey and Alexander (1985) and Casinos and Cubo (2000) had done related but not identical work on quantifying the wall thickness of tubular bones, and I was able to translate their results into ASPs (and MSPs for marrow-filled bones).


The procedure is pretty simple, as Mike has shown here before. Open up the image of interest in Photoshop (or GIMP if you’re all open-sourcey, like we are), make the bone one color, the air space a second color, and the background a third color. Count pixels, plug ’em into a simple formula, and you’ve got the ASP. I always colored the bone black, the air space white, and the background gray, so

ASP = (white pixels)/(black + white pixels)

For the image above, that’s 460442/657417 = 0.70.

Two quick technical points. First, most images are not just black, white, and one value of gray. Because of anti-aliasing, each black/white boundary is microscopically blurred by a fuzz of pixels of intermediate value. I could have used some kind of leveling threshold thing to bin those intermediate pixels into the bone/air/background columns, but I wanted to keep the process as fast and non-subjective as possible, so I didn’t. My spreadsheet has columns for black, white, gray, and everything else. The everything else typically runs 1-3%, which is not enough to make a difference at the coarse level of analysis I’m currently stuck with.

Second, I prefer transverse sections to longitudinal, because most of the internal chambers are longitudinally oriented. That means that longitudinal sections, whether sagittal or horizontal, are likely to cut through a chamber wall on its long axis, which makes the walls look unnaturally thick. For example, in the image above the median septum looks 5-10 times thicker than the outer walls of the bone, which would be a first–usually the outer walls are thicker than the internal septa, as you can see here. I don’t think the median septum really is that thick; I strongly suspect that a very thin plate of bone just happened to lie in the plane of the cut. It takes some work to get used to thinking about how a 2D slice can misrepresent 3D reality. When I first started CT scanning I was blown away by how thick the bone is below the pre- and postzygapophyses. I was thinking, “Wow, those centrozygapophyseal laminae must have been way more mechanically important than anyone thinks!” It took me a LONG time to figure out that if you take a transverse slice through a vertical plate of bone, it is going to look solid all the way up, even if that plate of bone is very thin.

Even apart from those considerations, there is still a list of caveats here as long as your arm. You may not get to choose your slice. That’s almost always true of broken or historically sectioned material, like NHM 46870. It’s even true in some cases for CT scans, because some areas don’t turn out very clearly, because of mineral inclusions, beam-hardening artifacts, or just poor preservation.

The slice you get, chosen or not, may not be representative of the ASP of the vertebra it’s from. Even if it is, other elements in the same animal may have different ASPs. Then there’s variation: intraspecific, ontogenetic, etc. So you have to treat the results with caution.

Still, there are some regularities in the data. From my own work, the mean of all ASP measurements for all sauropods is about 0.60. That was true when I had only crunched my first six images, late on the evening of October 9, 2003. It was true of the 22 measurements I had for Wedel (2005), and now that I have over a hundred measurements, it’s still true. More data is not shifting that number at all. And Woodward (2005) and Schwartz and Fritsch (2006) got very similar numbers, using different specimens.

This is cool for several reasons. It’s always nice when results are replicated–it decreases the likelihood that they’re a fluke, and in this case it suggests that although the limitations listed above are certainly real, they are not deal-killers for answering broad questions (we are at this point seeing the forest more clearly than the trees, though).

More importantly, the mean 0.60 ASP for all sauropod vertebrae is very similar to the numbers that you get from the data of Currey and Alexander (1985) and Cubo and Casinos (2000): 0.64 and 0.59, respectively. So sauropod vertebrae were about as lightly built as the pneumatic long bones of birds, on average.

Naturally, there are some deviations from average. Although I didn’t have enough data to show it in 2005, brachiosaurids tend to have higher ASPs than non-brachiosaurids. And Early Cretaceous brachiosaurids from the US and England are especially pneumatic–the mean for all of them, including Sauroposeidon, ‘Angloposeidon’, some shards of excellence from the Isle of Wight, and assorted odds and ends, is something like 0.75-0.80, higher even than Brachiosaurus. So there’s probably a combined phylogenetic/functional story in there about the highly pneumatic, hyper-long-necked brachiosaurids of the Early Cretaceous of Laurasia. Another paper waiting to be written.

Chondrosteosaurus broken face

Here’s another shard of excellence, referred to Chondrosteosaurus, NHM R96. As Mike had discussed here before, there’s no good reason to believe that it actually is Chondrosteosaurus, and the internal structure looks considerably more subdivided than in NHM 46870. This is an anterior view, and normally you’d be seeing a nice hemispherical condyle, but all of the cortical bone is gone and the internal structure is revealed. The little black traces are bone and the brownish stuff is rock matrix filling the pneumatic cavities.

Chondrosteosaurus broken face ASP

A few years ago, Mike asked me to look at that photo and guess the ASP, and then run the numbers and see how close I got. I guessed about 78%, then did the calculation, and lo and behold, the answer was 78%. So I’m pretty good at guessing ASPs.

Except I’m not, because as any of you armed with photo software can tell, that picture has 24520 black pixels and 128152 white ones, so the ASP is actually 128152/(128152+24520) = 0.84. The moral of the story is check your homework, kids! Especially if you seem to be an unnaturally good estimator.

ASP-ESP aside, I think ASP is cool and has some interesting potential at the intersection of phylogeny and biomechanics. But the method is severely limited by sample size, which is severely limited by how much of a pain in the butt preparing the images is. In most cases you can’t just play with levels or curves to get a black and white image that faithfully represents the morphology, or use the magic wand, or any of the other myriad shortcuts that modern imaging programs offer. Believe me, I’ve tried. Hard. But inevitably you get some matrix with the bone, or some bone with the matrix, and you end up spending an impossible amount of time fixing those problems (note that this is not a problem if you use perfect bones from extant animals, which is sadly not an option for sauropod workers). So almost all of my ASP images were traced by hand, which is really time-consuming. I could pile up a lot more data if I just sat around for a few weeks processing images, but every time I’ve gotten a few free weeks there has been something more important demanding my attention, and that may always be the case. Fortunately I’m not the only one doing this stuff now, and hopefully in the next few years we’ll get beyond these first few tottering steps.

Side Note: Does NHM 46870 represent a juvenile, or a dwarf?

This came up amongst the SV-POW!sketeers and we decided it should be addressed here. Darren noted that the vert at top is pretty darned small, ~23 cm for the preserved part and probably only a foot and a half long when it was complete, which is big for an animal but small for a sauropod and dinky for a brachiosaurid (if that’s what it is). Mike made the counter-observation that the internal structure is pretty complex, citing Wedel (2003b:fig. 12) and surrounding text, and suggested that it might be an adult of a small or even dwarfed taxon. And I responded:

I’m not at all certain that it is dwarfed. It matters a lot whether the complex internal structure is polycamerate or camellate. I was agnostic for a long time about how different those two conditions are, but there is an important difference that is relevant in this case: the two internal structures develop differently. Polycamerate verts really do get progressively more complex through development, as illustrated–there are at least two great series that show this, that I need to publish one of these days. But I think camellate vertebrae may be natively complex right from the get-go; i.e., instead of a big simple diverticulum pushing in from the side and making a big camera first, a bunch of smaller diverticula may remodel the small marrow spaces into small air spaces with no prior big cavities. At least, that’s how birds seem to do it. This needs more testing from sauropods–a good ontogenetic sequence from Brachiosaurus would be clutch here–but it’s my working hypothesis. In which case NHM 46870 may be a juvenile of a camellate taxon, rather than an adult of a polycamerate taxon.

The whole camerate-vs-camellate problem deserves a post of its own, and this post is already too long, so we’ll save that for another day.


It’s no secret – at least, not if you’re a regular SV-POW! reader – that the Lower Cretaceous Wealden Supergroup of southern England includes more than its fair share of enigmatic sauropod remains (see Mystery sauropod dorsals of the Wealden part 1, part 2, part 3). Poor taxonomic decisions, a dearth of adequate descriptive literature, and (perhaps) the vague concept that sauropod diversity in the Lower Cretaceous of Europe must be low have combined to prevent adequate appraisal. Recent comments on Wealden sauropods have been provided by Naish et al. (2004), Naish & Martill (2007), Taylor & Naish (2007) and Mannion (2008).


One of the most interesting Wealden sauropods – and I mean ‘interesting’ in an entirely subjective, historiographical sense – is Chondrosteosaurus gigas. This taxon has a rather confusing history that I don’t want to repeat here. The type series consists of two cervical vertebrae: BMNH R46869 and BMNH R46870 (and it is BMNH R46870, despite the occasional use in the literature of ‘46780’). We’ve looked at BMNH R46869 before. This time round I want to briefly talk about BMNH R46870. Anyone familiar with the literature on Wealden sauropods will know that this specimen was sectioned and polished. However, to date, only half of BMNH R46870 has been published (Owen 1876, plate V; Naish & Martill 2001, text-fig. 8.4), on both occasions as a mirror-image of the actual specimen. Previously unreported is that both halves of the specimen were polished, and both are in the Natural History Museum’s collection today. And here they are, shown together for the first time ever. I screwed up on the lighting, so sorry for the poor image quality [images © Natural History Museum, London].

A little bit of science has been done on this specimen. Chondrosteosaurus has had a mildly controversial history: it’s been suggested at times to be a camarasaur, but its camellate interior show that it’s a titanosauriform. Because the exact ratio of bone to air can be measured, the specimen lends itself particularly well to an Air Space Proportion analysis of the sort invented by Matt. Indeed, Matt did some ASP work on the figured half of BMNH R46870 in his thesis, finding an ASP of 0.70 (Wedel, Phd thesis, 2007). The average ASP of sampled neosauropod vertebrae is 0.61, and an ASP of 0.70 for the mid-centrum (as opposed to the condyle or cotyle) is most similar to the values present in camarasaurs and brachiosaurs. Mid-centrum ASP values of titanosaurs seem to be lower (Wedel, Phd thesis, 2007).


Anyway, more on Wealden sauropods – hopefully, a lot more – in the future.


  • Mannion, P. 2008. A rebbachisaurid sauropod from the Lower Cretaceous of the Isle of Wight, England. Cretaceous Research 30, 521-526.
  • Naish, D. & Martill, D. M. 2001. Saurischian dinosaurs 1: Sauropods. In Martill, D. M. & Naish, D. (eds) Dinosaurs of the Isle of Wight. The Palaeontological Association (London), pp. 185-241.
  • Naish, D. & Martill, D. M. 2007. Dinosaurs of Great Britain and the role of the Geological Society of London in their discovery: basal Dinosauria and Saurischia. Journal of the Geological Society, London, 164, 493-510.
  • Naish, D., Martill, D. M., Cooper, D. & Stevens, K. A. 2004. Europe’s largest dinosaur? A giant brachiosaurid cervical vertebra from the Wessex Formation (Early Cretaceous) of southern England. Cretaceous Research 25, 787-795.
  • Owen, R. 1876. Monograph on the fossil Reptilia of the Wealden and Purbeck Formations. Supplement 7. Crocodilia (Poikilopleuron). Dinosauria (Chondrosteosaurus). Palaeontographical Society Monographs, 30, 1-7.
  • Taylor, M. P. & Naish, D. 2007. An unusual new neosauropod dinosaur from the Lower Cretaceous Hastings Beds Group of East Sussex, England. Palaeontology 50, 1547-1564.

This is corn on the cob:

Corn on the cob, in cross section, stolen from http://www.istockphoto.com/file_thumbview_approve/214165/2/istockphoto_214165-co rn-cob-cross-section.jpg

Corn on the cob, in cross section. Stolen from http://www.istockphoto.com/file_thumbview_approve/214165/2/istockphoto_214165-co rn-cob-cross-section.jpg

This is a shish kebab:

Most tetrapods are like shish kebabs: a whole lot of meat stuck on a proportionally tiny skeleton.  If you don’t believe me, you can look at the human and cow neck torso cross-sections in Matt’s last post, or check out this ostrich-neck cross-section from his 2003 Paleobiology paper:

Ostrich neck in cross section, CT scan.  From Wedel (2003a: fig. 2)

Ostrich neck in cross section, CT scan. From Wedel (2003a: fig. 2)

Remember that this is a freakin’ ostrich — of all extant animals, one of the ones with a most extreme long, skinny neck.  And yet, if sauropods were muscled like ostriches, then their necks would have looked like this in cross section:

Putative shish kebab-style sauropod neck in cross section.  Ostrich soft-tissue from Wedel (2003a: fig. 2), Diplodocus vertebra cross-section from Paul (1997: fig. 4) scaled to match size of ostrich vertebra

Putative shish kebab-style sauropod neck in cross section. Ostrich soft-tissue from Wedel (2003a: fig. 2), Diplodocus vertebra cross-section from Paul (1997: fig. 4) scaled to match size of ostrich vertebra

And soft-tissue reconstructions would have to look like this:

Diplodocus with its neck as fat as an ostrich's.  Modified from Paul (1998: fig. 1F)

Diplodocus with its neck as fat as an ostrich's. Modified from Paul (1998: fig. 1F)

Which, happily, no-one is suggesting.  Instead, published reconstructions of sauropod neck soft-tissue are startlingly emaciated.  As exhibit A, I call this pair of Greg Paul cross-sections:

Diplodocus and Brachiosaurus neck cross-sections, showing very light musculature.  From Paul (1997: fig. 4)

Diplodocus and Brachiosaurus neck cross-sections, showing very light musculature. From Paul (1997: fig. 4)

(Yes, the Diplodocus on the left is the one I used in the photoshopped ostrich cross-section above.  It’s instructive to compare Paul’s original with the What If It Was Like A Big Ostrich version.)

Paul’s reconstructions seem to be widely considered too lightly muscled.  But even the very careful and rigorous more recent reconstructions of Daniela Schwarz and her colleague show a neck much, much thinner than that of the ostrich:

Diplodocus neck cross-sections.  From Schwarz et al. (2007: fig. 7a)

Diplodocus neck cross-sections. From Schwarz et al. (2007: fig. 7a)

Although Schwarz has put a lot more soft tissue onto the neck vertebrae than Paul did, it is still a tiny proportion of what we see in extant animals — even the ostrich, remember, which has a super-thin neck compared with pretty much anything else alive today.  If sauropod necks were muscled as heavily as those of, say, cows, then the soft tissue would pretty much reach down to the ground.  But they weren’t: they were more like corn on the cob, with a broad core of skeleton and relatively little in the way of delicious edibles festooned about it.

So why is this?  Why does everyone agree that sauropod necks were much less heavily muscled than those of any extant animal?

It’s a simple matter of scaling.  A really big ostrich might have a neck 1 m long.  (Actually, ostriches don’t get that big, but let’s pretend they do because it makes the maths easier).  If the x meter-long neck of a sauropod was just a scaled-up ostrich neck, then it would be x times longer, x times taller and x times wider, for a total of x^3 times as voluminous and therefore x^3 times as heavy.  But the cross-sectional area of the tension members that support it is only x times taller and x times wider, for a total of x^2 times the strength.  In total, then, the neck’s mass/strength is x^3/x^2 = x times as great as in the ostrich.  (The sauropod neck’s mass also acts further out from the fulcrum by an additional factor of x, but that is cancelled by the fact that the tension in the neck also acts x times higher above the fulcrum.)

It seems intuitively obvious (which is is code for “I have no way to prove”) that you can’t reasonably expect the neck muscles of a giant ostrich to work ten times as hard as they do in their lesser cousins, which is what you’d need to do for the 10 m neck of, say, Sauroposeidon.  So simple isometric scaling won’t get the job done, and you need to restructure the neck.

But how?  Surely just reducing all the muscle around the vertebrae can’t help?  No indeed — but that is not really what sauropods were doing.  If you look at the typical sauropod-neck life restoration, you’ll see that the proportional thickness of the neck is actually not too dissimilar to that of an ostrich — rather thicker, in fact.  If you scaled an ostrich neck up to sauropod size and compared it with a real sauropod neck, you would find not that the soft tissue was too fat, but that the vertebrae were too thin.

And so we come to it at last: rather than thinking of sauropods as having reduced the amount of soft-tissue hanging on the cervical vertebrae, we do better to think of them as having kept a roughly similar soft-tissue profile to that of an an ostrich, but enlarging the vertebrae within the soft-tissue envelope.  Of course if you just blindly made the vertebrae taller and wider, they would become heavier in proportion, which would defeat the whole purpose of the exercise — but as everyone who reads this blog surely knows by now, sauropod cervicals were extensively lightened by pneumaticity.  By bringing air into the center of the neck, they were effectively able to displace bone, muscle and ligament away from the centre, so that they acted with greater mechanical advantage: higher epaxial tension members, lower hypaxial compression members, and more laterally positioned paraxials.

It’s a rather brilliant system — using the same volume of bone to achieve greater strength by displacing it outwards and filling the center with air (and, in doing so, also displacing soft tissue outwards).  And it will be hauntingly familiar to anyone who loves birds, because it is of course exactly what birds (and pterosaurus) have done in their long bones: the hollow humeri of flying vertebrates famously allow them to attain greater strength — specifically, resistance to bending — for the same volume and mass of bone.  It’s a neat trick when done with long bones, but it takes a truly awesome taxon to do it with the neck.

So maybe sauropods were not corn on the cob after all.  Maybe they were Hostess Twinkies.

Hostess Twinkie.  Not truly pneumatic, as the internal cavity is filled with adipose tissue rather than air, but do you have any idea how difficult it is to find good images of hollow junk food?

Hostess Twinkie. Not truly pneumatic, as the internal cavity is filled with adipose tissue rather than air, but do you have any idea how difficult it is to find good images of hollow junk food? Stolen from http://dixiedining.files.wordpress.com/2008/07/twinkie_070918_ms1.jpg

And now for something completely different

Now that I’ve finished my Ph.D at the University of Portsmouth, what am I going to do with the rest of my scientific life?  I’ve always said that I have no intention of going into palaeo full time: my knowledge is far too narrow for that, so that even if paid jobs were not in insanely short supply, I wouldn’t stand much chance of getting one.  And in any case, I’d hate to get into the all-too-common situation of being up against a friend for a position we both wanted. Throw in the fact that I really enjoy my computer-programming day-job and it seems pretty clear that what I need is an unpaid affiliation that lets me get on with lovely research.

Well: I am absolutely delighted to announce that, as of last month, I am an Honorary Research Associate in the Department of Earth Sciences at UCL.  It’s not just that UCL is such a well-respected institution — see that Wikipedia article for some details — more importantly, it’s where Paul Upchurch hangs out, as Senior Lecturer in Palaeobiology.  Sauropod fans will be familiar with Paul’s characteristically detailed and careful work, from his pioneering work on sauropod phylogeny (Upchurch 1995, 1998), through his and John Martin’s indispensible Cetiosaurus makeovers (Upchurch and Martin 2002, 2003) to the state-of-the art review that he lead-authored for Dinosauria II (Upchurch et al. 2004) and the Tokyo Apatosaurus monograph (Upchurch et al. 2005).  What many of you won’t know is what an excellent collaborator he is — quick, conscientious, insightful and diplomatic.  We’ve already collaborated on a few short papers (Upchurch et al. 2009 and a couple of Phylocode companion-volume chapters that are in press), and I hope there will be more in the future.



This is a taco.


This is a corn dog.

Vertebra outlined in green. Click for unmarked original.

Vertebra outlined in green. Click for unmarked original.

Here’s a cross-section of a human. In the terms of fast food, people are corndogs. Most of us even have an outer ring of yellow adipose ‘breading’.

Vertebra oulined in red. Click for unmarked original.

Vertebra oulined in red. Click for unmarked original.

Here’s a cross-section of a cow. In an example of function following form, cows are, and often become, corndogs.

Note that in both the human and the cow the spaces between the neural spine and transverse processes are completely filled with back muscles, which in fact bulge out beyond the tips of the neural spine, as we also saw here. This despite the common paleoart convention of presenting dinosaurs as thin layers of skin conforming perfectly to the underlying skeleton. Just Say No to shrink-wrapped sauropods!

Diplodocus torso xs

Here is Figure 17 from Holland (1910), one of the most badass scientific smackdowns ever published, in which Holland wiped the floor with Hay, Tornier, and the idea of sprawling sauropods. On the left are torso skeletons of three lizards and a croc; on the right is an anterior dorsal with articulated ribs from Diplodocus. As you can see, it’s a taco, and its taconic form would be perfected if it could roll supine.

The point of the post is not that sauropods had deep, slab-sided bodies. We’ve covered that before. The point is that sauropod torsos are seriously weird. In mammals, the dorsal ribs arch up and out, away from the vertebra, before sweeping around to define the anterior body wall.  In lizards, the proximal part of each rib sticks out sideways. In sauropods, the ribs point down. This is mainly because the vertebrae are FREAKIN’ HUGE compared to the size of the body. Whereas in the mammals and lizards the dorsal vertebrae are titchy little things that span a small fraction of the width of the torso, in Diplodocus and other sauropods the dorsal vertebrae account for about half. (The cow cross-section missed the transverse processes, so that vert looks narrower than it actually is.)

This is relevant when we think about the function of pneumaticity. When I write that pneumaticity lightened vertebrae, I usually mean relative to that same vertebra if it wasn’t pneumatized. But we could also ask if the pneumatic vertebra is lighter than a vertebra from a similar-sized animal that lacks pneumaticity–except that, for big sauropods, there are no similar-sized terrestrial animals without pneumaticity to compare.

Imagine that in a big sauropod the dorsal vertebrae are three times as wide and three times as tall as they would be in a similar-sized mammal. They should weigh nine times more. But let’s also assume that the vertebrae of the sauropod are 85% air by volume, which is in fact pretty typical for Early Cretaceous brachiosaurids. The mass of the dorsal column relative to that of the mammal is then 9 x 0.15 = 1.35, a little heavier, but not much (I’m assuming the length of the torso is the same in the two animals). Bigger bones mean better lever arms for the muscles and lower bending stresses on the ribs, which can function more like curtains and less like cantilevered beams.

I can’t think of much published discussion of this stuff as it relates to sauropods, but it seems like it might be important.


Holland, W.J. 1910. A review of some recent criticisms of the restorations of sauropod dinosaurs existing in the museums of the United States, with special reference to that of Diplodocus carnegiei [sic] in the Carnegie Museum. American Naturalist 44:259-283.


December 8, 2008


A 3D reconstruction of the paranasal sinuses in a human (from Koppe et al. 1999). You also have paratympanic sinuses that pneumatize the mastoid process of the temporal bone (feel for an inferiorly-directed, thumb-size protuberance right behind each ear).


An x-ray of a pig skull, from here. Can you see the outline of the brain-shaped endocranial cavity?


How about in this x-ray of a rhino skull? Image courtesy of Kent Sanders.


A sectioned cow skull. The bottom half of the endocranial cavity is exposed in the horizontal cut. The vertical cut shows the tiers of sinuses that make up most of the volume of the skull. I think that the middle tier (the large, butterfly-shaped space) is the front part of the endocranial cavity and housed the most rostral bits of the brain; note that it is completely surrounded by sinuses.


Part of a bighorn sheep skull. The pneumatic horncores of bighorns are a useful antidote to the idea that pneumatic bones must be weak.


A cross-section of an elephant skull, courtesy of Project Gutenberg. The cavity at the back marked ‘b’ is the endocranial cavity that holds the brain. The big tube running through the middle is the nasal airway. Everything else is pneumatic. Note that the brain is entirely surrounded by sinuses.


A blown skull of a proboscidean from the bone cellar at the Humbolt Museum. I snapped this on the last day in collections,  on a mad scramble to get whatever non-sauropod pics (gasp!) I might want later. The bumps to the upper right are the occipital condyles; the skull is in left lateral view facing down and to the left.


Paratympanic sinuses (green) surrounding the brain (blue) of an alligator, from David Dufeau’s homepage. Go there for a lot more mind-blowing images of sinuses. The snout of this gator is filled with paranasal sinuses, they’re just not shaded in here.


Sectioned skull of a rhinoceros hornbill, which is pretty much completely filled with paranasal and paratympanic sinuses. Even the lower jaw is pneumatized.

Okay, so now you know that mammals, crocs, and birds are all air-heads. What does any of this have to do with sauropods? Well…

  • Archosaurs and mammals evolved cranial pneumaticity independently. Does that mean that cranial pneumaticity is easy to evolve (since it evolved more than once) or hard to evolve (since it only evolved twice)? This is relevant to the question of how many times postcranial pneumaticity evolved.
  • Archosaurs evolved cranial pneumaticity before they evolved postcranial pneumaticity. Does that mean that postcranial pneumaticity is the application of a pre-existing developmental program (bone pneumatization) to a new anatomical region (the postcranial skeleton)? Or did the developmental control of pneumatization have to evolve de novo in the postcranium?
  • The development of cranial pneumatization in mammals and postcranial pneumatization in birds seems to  follow similar rules. Does that mean that we can apply lessons learned from, say, the development of human sinuses to understand the development of sauropod vertebrae?
  • Sauropods and big-headed mammals like elephants have this in common: at the front end they’ve got a big chunk of pneumatic bone. In sauropods, it’s the neck; in elephants, it’s the head. In both cases the big pneumatic organ makes up close to a tenth of the animal’s volume. I don’t know what else to make of that, but maybe you can get mileage out of it at a cocktail party.

I posted these because I was inspired by Darren’s post on dome-headed elephants, because they’re cool, to maybe demystify sauropod pneumaticity a little, or perhaps to re-mystify skeletal pneumatization in general. You have a pneumatic cavity between your brain and your monitor right now. How much time have you spent thinking about that (when you didn’ t have a sinus headache)?

Next time: more Berlin goodness.


UPDATE: By utter coincidence, Ohio University put out a news story about Larry Witmer’s work on sinuses yesterday. Hat tips to Yasmani Ceballos Izquierdo, who posted the link on the DML, and to Mike for sending it on to me. As long as you’re going over there, remember that Larry is one of the Good Guys and puts his papers up for public consumption; the new dino sinus paper is here. It’s great, but it makes the pictures I used here look pretty pathetic. Go have fun!

Internal structure of a cervical vertebra of Sauroposeidon, OMNH 53062. A, parts of two vertebrae from the middle of the neck. The field crew that dug up the bones cut though one of them to divide the specimen into manageable pieces. B, cross section of C6 at the level of the break, traced from a CT image and photographs of the broken end. The left side of the specimen was facing up in the field and the bone on that side is badly weathered. Over most of the broken surface the internal structure is covered by plaster or too damaged to trace, but it is cleanly exposed on the upper right side (outlined). C, the internal structure of that part of the vertebra, traced from a photograph. The arrows indicate the thickness of the bone at several points, as measured with a pair of digital calipers. The camellae are filled with sandstone.

Image and caption recycled from fig. 14 here. Hat tip to Mike from Ottawa for the wonderful title.

Addendum (from Mike)

What Matt’s failed to mention is that this section of prezygapophyseal ramus is one of the elements for which he calculated the Air-Space Proportion (ASP) in his chapter in “The Sauropods”. As shown in his table 7.2, this calculation yielded 0.89.  Just think about that for a moment.  89% of the bone was air.  Yikes.

It’s interesting that this was the only prezygpapophyseal ramus in the survey, and that it had a way higher value that any of the other elements considered, which topped out at 0.77, i.e., more than twice as much bone as this specimen.  So maybe all prezyg rami are ridiculously pneumatic? So far (as far as I know) no-one’s measured the ASP of another ramus, so the answer remains, for now, ridiculously unknown to our planet.

Special bonus weirdness

Basal sauropodomorph wizard Adam Yates has posted an entry on his blog showing more sauropod vertebrae/ceratopsian frill convergence, as follow-up to our own recent post. Too weird.

You know, we have not done what we intended with this blog. We intended to post pretty pictures of sauropod vertebrae, sketch a few lines of text a la our inspiration, and call it good. But not one of us is capable of shutting up–me least of all–so we sit down to write 6 lines and end up writing 60 or 600.

Well, not this time. Here’s BYU 12866, probably a fifth cervical, almost certainly from Brachiosaurus, plus some CT cross-sections (the cross-sections have been straightened up a little to correct distortion in the specimen; see figure 12 here for the unexpurgated version). If they haven’t been defined before, camerae are big chambers and camellae are small chambers.

Hat tip to Mike from Ottawa for the title.


Matt is staying here at Taylor Towers for a couple of weeks while his wife spends some quality time with some leprous human remains in Bradford (yes, really). Since both Matt and I are big fans of sushi, I took a stab at making some at home on Sunday night:

Fig. 1. Sushi plate, poorly preserved due to predation

Fig. 1. Sushi plate, poorly preserved due to predation

We noticed that the spring onion in one of the rolls had held its shape sufficiently well to preserve an air-space running along the length of the roll:

av, avocado; cs, crab-stick; pf, pneumatic foramen; pr, prawn.

Fig. 2. Spring-onion california roll, cross-section in anterior view. A, photograph; B, interpretive drawing. Anatomical abbreviations: av, avocado; cs, crab-stick; pf, pneumatic foramen; pr, prawn.

Using the technique of Wedel (2005:212-213), we can calculate the air-space proportion of this roll (ASP) by dividing the area of the enclosed pneumatic space by total cross-section.

fig. 7.5)

The simplest way to do this is to reduce the image to simple black-and-white with a grey background and count the pixels:

Fig. 4. Spring-onion California roll depicted in figure 2, with solid material drawn in black and pneumatic space in white.

Fig. 4. Sushi roll depicted in figure 2, with solid material drawn in black and pneumatic space in white.

According to image-processing program, the full-sized version of this images has 21961 white pixels and 302993 black pixels, yielding an ASP of W/(W+B) = 21961/(21961+302993) = 0.067, or 6.7%. This is a very low value compared to most sauropod vertebrae: according to Wedel (2005:table 7.2), values are mostly in the range 50-70% — nearly ten times as pneumatic as this sushi roll — with Sauroposeidon reaching 89% in a cervical prezygapophyseal ramus.


Hottt news

May 15, 2008

Mike Taylor has a loooong interview up at Laelaps. It’s sauropawesome.

The picture above has nothing to do with that, we just like to put sauropod vertebrae in every post. Here are some CT sections of a Haplocanthosaurus cervical (abbreviations: fos – fossa, lam laminae, nc neural canal, ncs neurocentral suture). I like them because they look nothing like what I expected. Not that the internal structure or laminae are unusual for sauropods, just that sauropod vertebrae themselves are unusual and sometimes the best way to be confronted with that is to see them from new vantages. I recycled this from Wedel (2007:fig. 13), and it basically just a rearrangement of Wedel (2005:fig. 7.3). The nice drawing of the Haplo cervical is from Hatcher (1903:pl. 2).

Well, now I’ve blabbed on for a paragraph and managed to cite myself twice in a post that is ostensibly about Mike. Seriously, go read the interview, it’s great.


Hatcher, J.B. 1903. Osteology of Haplocanthosaurus, with a description of a new species, and remarks on the probable habits of the Sauropoda, and the age and origin of Atlantosaurus beds. Mem Carn Mus 2:1-72.

Wedel, M.J. 2005. Postcranial skeletal pneumaticity in sauropods and its implications for mass estimates; pp. 201-228 in Wilson, J.A., and Curry-Rogers, K. (eds.), The Sauropods: Evolution and Paleobiology. University of California Press, Berkeley.

Wedel, M.J. 2007. Aligerando a los gigantes (Lightening the giants). ¡Fundamental! 12:1-84. [in Spanish, with English translation]