Grilling your Thanksgiving dinosaur: live-blogging the bird

Trying two new things this morning: grilling a turkey, and live-blogging on SV-POW!

I like to grill. Steak, chicken, kebabs, yams, pineapple, bananas–as long as it’s an edible solid, I’m up for it. But I’ve never grilled a turkey before. Neighbor, colleague, fellow paleontologist and grillmeister Brian Kraatz sent me his recipe, which is also posted on Facebook for the edification of the masses. See Brian’s excellent writeup for the whole process, I’m just going to hit the photogenic parts here. Oh, and usually I tweak any photos I post within an inch of their lives, but I don’t have time for that this morning, so you’re getting as close to a live, unedited feed as I can manage. Stay tuned for updates.

Enough of that. Let’s rock!

The process starts  more than a day in advance, with the brine. Salt water, fruit, onions, garlic, spices, and some apple juice.

The turkey needs to be entirely immersed in the brine for at least 24 hours. Doing this in a solid container would require an extra big container and too much  liquid to cover the bird. I follow Brian’s method of brining in a triple-layer of trash bags. You can see a turkey roaster peeking out underneath the trash bags. Helps with the carrying.

Put the turkey in the trash bags first, then pour in the brine. Unless you like huge messes.

The genius of the trash bag method on display. You can squeeze out all the air so that the volume of the bag is equal to just the turkey and the brine.

Into the fridge for a day.

First thing this morning: out come the giblets, and save the goodies from the brine. We’ll get back to the neck later.

The bird awaits.

Crucial step: putting in a drip pan. Keeps the coals off to the side for indirect heat, and catches the grease so you don’t burn down the neighborhood.

Putting in the herb butter. I used three short sticks of butter mixed with sage, lemon pepper, and Mrs. Dash. Working the skin away from the meat and then filling the space with butter was extremely nasty. This must be what diverticula feel like.

A chimney is helpful to get the coals going.

To eat is human; to grill is divine.

Smoke bombs: mesquite chips soaked in water, wrapped up in balls of tinfoil, with holes poked on top to let the smoke out.

Fruit and spices into the body cavity.

At this point, I was fairly certain that today would be the greatest day of my life. The turkey is centered over the drip pan, stuffed with goodness, subcutaneously loaded with herb butter, draped with bacon. You can see one of the smoke bombs sitting right on top of the coals.

Know what you’re getting into. This 15 lb bird just barely cleared the lid of my grill.

A little over an hour in. I installed foil heat shields to keep the wings and thighs from cooking too fast. It’s all about the indirect heat. Some of the bacon comes off now, as a mid-morning treat.

Okay, the bird is about halfway done, and I have to whip up some sustainer coals and another batch of smoke bombs. Further updates as and when. Happy Thanksgiving!

UPDATE

I was hoping to get some more pictures posted before we ate, but you know how it is in the kitchen on Thanksgiving Day (or, if you’re not an American, maybe you don’t know, so I’ll tell you: dogs and cats living together, we’re talking total chaos).

The turkey just before I pulled it off the grill. The heat shields turned out to be clutch, I would have completely destroyed the limbs without them. That’s going to be SOP from now on.

Ah yes, the bird, she turned out even more succulent than I hadda expected. Check out the pink shade of the meat just below the skin. I recognize that, from good barbeque, but I’ve never produced it before.

That’s it for the cooking part of today’s program. As for the ultimate fate of the bird…we ate a stupifying amount of it. I sent even more home with our guests. And the other half–yes, half–of this thunder beast is sitting in the fridge. Hello-o leftovers!

And hello-o science!

I was going to post some more pictures of the neck, but I didn’t get around to eating it, so…another time, perhaps. In lieu, here’s Mike’s turkey vertebra in left lateral view (see the original in all its supersized glory here). Note the pneumatic foramen in the lateral wall of the centrum, just behind the cervical rib loop. This is actually kind of a lucky catch; a lot of times with chickens and turkeys, the pneumatic foramina are so far up in the cervical rib loop that they can’t be seen in lateral view.

It used to freak me out a little bit that birds often don’t have their pneumatic foramina in the middle of the lateral wall of the centrum, like sauropods. But a possible explanation occurred to me just this morning as I was planning this post. I think that birds have their pneumatic foramina right where you’d expect them, based on sauropods. I’ll explain why.

The first part of the explanation is that instead of wearing their pneumatic cavities on the outside, like this Giraffatitan cervical, bird vertebrae tend to be inflated from within, with just a few tiny foramina outside. The second part is that birds have HUGE cervical rib loops compared to sauropods. If the sauropod vert shown above had its rib on, the resulting loop would be fairly dainty, the osteological equivalent of a bracelet. The cervical rib loops of birds are more like tubes, they’re so antero-posteriorly elongated.

So take the brachiosaur cervical shown above and shrink all of the external pneumatic spaces by several inches. The cavities on the arch and spine would close up entirely, and the complex of fossae and foramina on the lateral side of the centrum would be reduced to a small hole right behind the cervical rib. Then stretch out the cervical rib loop in the fore-aft direction and voila, you’d have something like a turkey cervical, with a little tiny pneumatic foramen tucked up inside the cervical rib loop.

This doesn’t explain why bird verts are inflated from within instead of being eroded from without, or why sauropods had such dinky cervical rib loops (mechanical what, now?), or why pneumatic diverticula tend to make the biggest holes in the front half of the centrum, adjacent to the cervical ribs. I just think that maybe bird and sauropod pneumaticity are not as different as they  appear at first glance. Your thoughts are welcome.

More out than in

I drew a couple of these a while back, and I’m posting them now both to fire discussion and because I’m too lazy to write anything new.

Here’s the neck of Apatosaurus, my own reconstruction based on Gilmore (1936), showing the possible paths and dimensions of continuous airways (diverticula) outside the vertebrae.

Here’s figure 4 from Lovelace et al. (2007), which first got me thinking about pneumatic traces on the ventral surfaces of the centra and what they might imply. You can see pneumatic spaces between the parapophyses in Supersaurus (A) and Apatosaurus (C) but not in Barosaurus (B).

This is another of my moldy oldies, again based on one of Gilmore’s pretty pictures, showing how I think the soft tissues were probably arranged. The muscles are basically the technicolor version of Wedel and Sanders (2002). Two points:

1. How bulky you make the neck depends mainly on how much muscle you think was present (which of course depends on how heavy you think the neck was…). Here I was just trying to get the relationships right without worrying about bulk, but it’s worth considering.
2. The volume of air inside the vertebra was dinky compared to the probable volume of air outside. In Apatosaurus, either of the canals formed by the transverse foramina has almost twice the cross-sectional area of the centrum.

A fair amount of this has been superseded with better data and prettier pictures by Schwarz et al. (2007), so don’t neglect that work in any ensuing discussion (it’s free, fer cryin’ out loud). And have a happy Thanksgiving!

References

• Gilmore, C.W.  1936.  Osteology of Apatosaurus with special reference to specimens in the Carnegie Museum. Memoirs of the Carnegie Museum 11: 175-300.
• Lovelace, D.M., Hartman, S.A., and Wahl, W.R. 2007. Morphology of a specimen of Supersaurus (Dinosauria, Sauropoda) from the Morrison Formation of Wyoming, and a re-evaluation of diplodocid phylogeny. Arquivos do Museu Nacional, Rio de Janeiro 65(4):527-544.
• Schwarz, D., Frey, E., and Meyer, C.A. 2007. Pneumaticity and soft−tissue reconstructions in the neck of diplodocid and dicraeosaurid sauropods. Acta Palaeontologica Polonica 52 (1): 167–188.
• 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.

Postscript

Mike asked me to add the labeled version of Nima’s brachiosaur parade, so here you go. Click to embiggen.

CT-Scanning the Archbishop

Last week, for the first time ever, I spent the entire working week on palaeo.  I took a week away from my job, and spent it staying in London, working on the Archbishop at the Natural History Museum.  (For those of you who have not been paying attention, the Archbishop is the informal name of the specimen NHM R5937, a brachiosaurid sauropod from the same Tendaguru area that produced Giraffatitan brancai, and which has been generally assumed to represent that species.)

Brachiosauridae incertae sedis NHM R5937, "The Archbishop", Cervical U in right lateral view. Photo copyright the NHM since it's their specimen.

My main goal was to take final publication-quality photographs that I can use in the description (which I have committed to try really, really hard to get submitted by the end of 2009).  There’s quite a bit of material (more than for Xenoposeidon, anyway!) — six cervicals in various states of preservation/preparation, cervical ribs, two complete dorsals, two more dorsal centra and a dorsal spine, some scap scraps, a partial ?pubis, a long-bone fragment and “Lump Z“, whatever that is.  What you see above is my best lateral-view photograph of what I’ve designated “Cervical U”.  One of these days, I’m going to do a post on how to photograph large fossils — something it’s taken me five years to get the hang of — but for today, I want to tell you about an exciting adventure with Cervical U.

Because my other big goal on this trip was to get it CT-scanned.  Thanks to the generosity of John Hutchinson of the Royal Veterinary College, and to the help of the NHM people in arranging a loan, everything was set up for my host Vince Bickers and me to ferry the specimen up to the RVC, scan it and return it.

But first it had to be packed:

The Archbishop, Cervical U, packed and ready for transportation. Behind, Lorna Steel and Sandra Chapman of the NHM, who did the work.

Lorna and Sandra spent a long time looking for a crate big enough to pack the bone in, but came up empty — there was one that was long enough but not wide enough, one that was tall enough but not long enough, and so on.  In the end we sat the bone, on its very solid plaster base, on a plastic pallet, and wrapped it in pillows, bubble-wrap and that blue stuff whose name I don’t know.

As it happened, the scan had to be delayed for a day due to lack of personnel at RVC, but Vince and I took the vertebra up on the Thursday anyway; he had to return to work on the Friday, but I took public transport to RVC for the big day.  Before we went into the scanning room, John showed me his freezer room:

Just a couple of the freezers at RVC

I found it amusing that they have enough Segments Of Awesome that they have to label the various elephant-part freezers differently.  And further down the aisle:

John Hutchinson proudly shows off his dead baby rhino.

Then it was off to the scanning facility, where we found that we had to unpack the vertebra: it was small enough to go through the machine, but there was no way the pallet was going through.  Once we’d unpacked it and removed it, it fit pretty nicely:

The Archbishop's Cervical U all lined up and ready to go through the scanner, courtesy of John and radiographer Victoria Watts.

Because the scanner spits out X-rays in all directions, it’s controlled from a separate room, behind lead-impregnated glass:

Inside the control room

We ran three scans before we got the settings right — we needed more voltage to get through the bone and matrix than we’d first realised, and a filter was causing unhelpful moire patterns.  The third scan was definitely the best, and the one I expect to be working with.

[Boring technical side-note: I plan to use 3D Slicer for visualisation thanks to Andy Farke's series of tutorials. But, frustratingly, I wasn't able to load the DICOM files from the scan into that program: it crashes when trying to load them (segmentation fault) even though it works fine on the ankylosaur skull that Andy walked us through in the tutorials.  I fixed this by gluing the 300-odd files together into a single stack file that 3D Slicer was able to read.  For the benefit of anyone else who needs to do this, the command (on a Ubuntu Linux box) was: medcon  -f  *.dcm  -c  dicom  -stack3d  -n  -qc]

Here is an example slice, showing part of the condyle in posterior view:

CT slice through the condyle of The Archbishop's Cervical U, in posterior view. Dorsal is to the left.

The grey blobs at the bottom of the image are the plaster jacket that supports the vertebra; the white is bone, and the light grey inside it is matrix that fills the pneumatic spaces.  I’m showing the condyle here because its cavities are clearly visible: further back in the vertebra, they are harder to pick out, perhaps in part because of the iron bars scattering the X-rays.  It’s notable that this vertebra is less pneumatic than would be expected for a brachiosaurid — by eye, it looks like like the condyle is only 20-30% air, and this slice is not unrepresentative.  Most neosauropods would be at least twice this pneumatic, so we may have an Archbishop autapomorphy here.

I’ve not yet persuaded 3D Slicer to build a 3D model for me, but I’m pleased to say that before I left RVC, John mocked up a quick-and-dirty render of the bone using only density threshholding, and I can at least show you that.

The Archbishop, Cervical U, CT scan 3d model in left ventrolateral view

Here we see the bone from the left side, previously obscured by solid plaster.  From a single static image, it’s not easy to make out details, but we can at least see that there is a solid ventral floor to the centrum … and that those two crossed iron bars obscure much that we would like to see.  You will get more of an idea from the rotating video that this is screencapped from.

Looking at this and comparing it with the right-lateral photo at the top of the post, it’s apparent that the density threshhold was set too high when making this model: all the bone along the lower right margin of the middle part of the centrum is good, but it’s been omitted from the model.  In other words, the vertebra is more complete than this proof-of-concept model suggests.  Hopefully I will shortly be able to show you a better model.

ASP target of opportunity

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:

(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:

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?

NHM 46870 Strikes Back: ASP

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:

• external traces: Wedel (2005, 2007)
• internal complexity: Wedel et al. (2000a, 2000b), Wedel (2003b)
• bone/air ratio: Wedel (2005)
• distribution in the body: Wedel (2003a, 2006, 2009)

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.

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.

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.

References

• Cubo, J., and Casinos, A. 2000. Incidence and mechanical significance of pneumatization in the long bones of birds. Zoological Journal of the Linnean Society 130: 499–510.
• Currey, J. D., and Alexander, R. McN. 1985. The thickness of the walls of tubular bones. Journal of Zoology 206:453–468.
• Farke, A. A. 2007. Morphology, constraints, and scaling of frontal sinuses in the hartebeest, Alcelaphus buselaphus (Mammalia: Artiodactlya, Bovidae). Journal of Morphology 268:243-253.
• 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.
• O’Connor, P.M. 2004. Pulmonary pneumaticity in the postcranial skeleton of extant Aves: a case study examining Anseriformes. Journal of Morphology 261:141-161.
• O’Connor, P. M. 2009. Evolution of archosaurian body plans: Skeletal adaptations of an air-sac-based breathing apparatus in birds and other archosaurs. Journal of Experimental Zoology DOI: 10.1002/jez.548
• Schwarz D, Fritsch G. 2006. Pneumatic structures in the cervical vertebrae of the Late Jurassic Tendaguru sauropods Brachiosaurus brancai and Dicraeosaurus. Eclogae Geologicae Helvetiae 99:65–78.
• Woodward, H. 2005. Bone histology of the titanosaurid sauropod Alamosaurus sanjuanensis from the Javelina Formation, Texas. Journal of Vertebrate Paleontology 25 (Supplement to No. 3):132A.

The hitherto hidden half of BMNH R46870

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.

References

• 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.

Sauropods were corn-on-the-cob, not shish kebabs

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

This is a shish kebab:

Shish kebab. Stolen from http://www.mediterraneancafe-flatiron.com/images/shish.jpg

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)

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

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)

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)

(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)

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? 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.

References

• Paul, Gregory S.  1997.  Dinosaur models: the good, the bad, and using them to estimate the mass of dinosaurs.  pp. 129-154 in: D. L. Wolberg, E. Stump, and G. D. Rosenberg (eds.), DinoFest International: Proceedings of a Symposium Sponsored by Arizona State University.  Academy of Natural Sciences, Philadelphia.
• Paul, Gregory S.  1998.  Terramegathermy and Cope’s Rule in the land of titans.  Modern Geology 23: 179-217.
• Schwarz, Daniela, Eberhard Frey and Christian A. Meyer.  2007. Pneumaticity and soft-tissue reconstructions in the neck of diplodocid and dicraeosaurid sauropods.  Acta Palaeontologica Polonica 52(1): 167-188.
• Upchurch, Paul.  1995.  The evolutionary history of sauropod dinosaurs.  Philosophical Transactions of the Royal Society of London Series B, 349: 365-390.
• Upchurch, Paul.  1998.  The phylogenetic relationships of sauropod dinosaurs.  Zoological Journal of the Linnean Society, 124: 43-103.
• Upchurch, Paul and John Martin.  2002.  The Rutland Cetiosaurus: the anatomy and relationships of a Middle Jurassic British sauropod dinosaur.  Palaeontology, 45(6): 1049-1074.
• Upchurch, Paul and John Martin.  2003.  The anatomy and taxonomy of Cetiosaurus (Saurischia, Suaropoda) from the Middle Jurassic of England.  Journal of Vertebrate Paleontology 23(1): 208-231.
• Upchurch, Paul, Paul M. Barrett and Peter Dodson.  2004.  Sauropoda. pp. 259-322 in D. B. Weishampel, P. Dodson and H. Osmólska (eds.), The Dinosauria, 2nd edition.  University of California Press, Berkeley and Los Angeles.  861 pp.
• Upchurch, Paul, Yukimitsu Tomida, and Paul M. Barrett.  2005.  A new specimen of Apatosaurus ajax (Sauropoda: Diplodocidae) from the Morrison Formation (Upper Jurassic) of Wyoming, USA.  National Science Museum Monographs No. 26.  Tokyo.  ISSN 1342-9574.
• Upchurch, Paul, John Martin, and Michael P. Taylor.  2009.  Case 3472: Cetiosaurus Owen, 1841 (Dinosauria, Sauropoda): proposed conservation of usage by designation of Cetiosaurus oxoniensis Phillips, 1871 as the type species.  Bulletin of Zoological Nomenclature 66(1): 51-55.
• Wedel, Mathew J.  2003.  Vertebral pneumaticity, air sacs, and the physiology of sauropod dinosaurs.  Paleobiology 29(2): 243-255.

Choosing a journal for the neck-posture paper: why open access is important

[Disclaimer: in this post, I am unavoidably critical of certain aspects of particular journals.  Please take this in the spirit it's intended: I'm not out to get anyone, but I need to illustrate my points with real examples.]

When we started blogging our recent neck-posture paper (Taylor et al. 2009, for those of you who’ve been chatting in the back row and not paying attention), we expected to make two posts, maybe three.  Yet here we are in post six, and I know Matt has another up the barrel for tomorrow, so it looks like we’re going to end up having written a whole week’s worth of daily posts, just as we did for Xenoposeidon.

One of the questions a lot of people have asked me is why we published in a Polish journal (Acta Palaeontologica Polonica).  Although APP is published in Poland and edited by a primarily Polish board, it’s more accurate to characterise it as an international journal — the papers in the issue where our work appeared had lead authors based in Poland (4 papers), USA (3), Italy (2), and England, France, Japan, Spain and Sweden (1 each).  Still, that question is a nice jumping-off point to discuss something of relevance to all academics that doesn’t get a lot of coverage: how to choose a journal.

From another sauropod paper in Acta Palaeontologica Polonica: Schwarz et al. (2007: fig. 1), showing CT scans of a Diplodocus cervical

Criteria for choosing a journal

There are plenty of criteria that come in to play in picking a journal, and people will vary in how much weight their place on each.  We’ll take a look at some of them (in no very convincing order), and then I’ll explain what I think is the unifying principle.

Impact factor. I’ll deal with this first, because it’s easiest to dismiss.  The impact factor is a stupid, irrelevant number attached to journals by a private corporation with its own agenda and with no responsibility to actual scientists.  Its use is particularly dumb in palaeo, a field in which it’s near impossible to get a paper written, submitted, reviewed and published in time to hit the two-year window during which citations are counted for impact-factor purposes — which is why even the best palaeo journals (JVP, Palaeontology, APP) have impact factors close to 1.0.  All scientists should ignore impact factor whenever possible.

Prestige. Now we’re getting somewhere.  Prestige is what impact factor is a (wholly inadequate) proxy for.  Of course, it’s impossible to define or quantify satisfactorily, but we all know what we mean by it.  Sadly, top of the tree for prestige — by a long way — are the “tabloids”, Science and Nature.  It’s considered a huge deal to publish in these, very good for your career — which is a shame, as the super-short format makes it nearly impossible to do decent science in these venues.  As Exhibit A, I give you Sereno et al. (1999).  In five pages, Sereno and his ten co-authors presented descriptions of not one but two new sauropod genera, plus a time-calibrated phylogeny and an analysis of rates of morphological change through time.  It is not intended as a criticism of Sereno and his colleagues when I say that for scientific purposes, the descriptions in this paper are essentially worthless — it’s simply not possible to do anything like justice to two genera, both represented by nearly complete remains, in that amount of space.  Lest I seem to be picking on this particular team, which I honestly assure you is not my purpose here, I could equally point to Curry Rogers and Forster’s (2001) description of Rapetosaurus, Rauhut et al. (2005) on Brachytrachelopan or indeed the original DinoMorph paper (Stevens and Parrish 1999).  The publication of important work in the tabloids is not such a disaster when conscientious authors such as John Hutchinson follow up a high-prestige extended abstract such as Hutchinson and Garcia (2002) with a full-length study elsewhere (Hutchinson et al. 2005), but sadly this seems to be more the exception than the rule — after all, if you’ve already got all that credit for a short paper, why bother doing all the extra work involved in getting the full-length paper done?  That said, I am assured that Curry Rogers’s long-awaited Rapetosaurus osteology is on the way RSN.  At the risk of sounding sour-grapesy (I’ve never been published in either tabloid myself), I do think that the existence of these journals is a net negative for actual science.  I won’t go so far as to say that I’ll never publish in S‘n’N if I get the chance, but I do right here and now undertake that if ever that chance should come my way, I will do my level best to get the full-length study out as soon as possible thereafter.

Hmm, that seems to have turned into a tangential rant about the tabloids, which really wasn’t my intention, but so it goes.  More generally, there is a sense that general-science journals are more prestigious than specialist palaeo journals: notable ones include PNAS and the various Royal Society journals.  An exception to this rule is the PLoS journals: because it’s more selective PLoS Biology is considered more prestigious than the general-science PLoS ONE.  Among palaeo journals, there’s a feeling that Paleobiology is particularly well regarded, with Palaeontology, the Journal of Paleontology, JVP and Acta Pal. Pol. up on its shoulders.  Other journals are a little further down the great chain of being.

How much does prestige matter?  Quite a lot (especially if you need your CV to look good) but rather less than a few years ago, I think — for reasons that will become apparent later on.

Turnaround speed. The importance of this will vary at different times.  I’ve had a couple of my papers published in PaleoBios, the journal of the University of California Museum of Paleontology — which is not particularly high-profile — for one main reason: they turn papers round really quickly.  That was particularly important to me when I was starting out, and really needed to get something on my CV quickly.  Now that my publication list is a little less feeble, I can afford to let my manuscripts marinate for longer in order to get them into more recognised journals.  But sometimes that goes to ridiculous extremes: a while back, Matt and I sent a paper to Paleobiology.  The editors sat on the manuscript for more than a month before even sending it out to reviewers.  When I asked two months later, then again a month after than, then again a month after that, reviews were still not in.  In the end, we didn’t hear back until more than six months after submission — and when we finally saw the reviews, one of them consisted only of filling in a one-page form.  We weren’t impressed, and won’t be submitting there again, despite the journal’s high prestige.  (We know others who have had even longer waits.  Sadly, we didn’t know this at the time we submitted; if we did, we’d have made other plans).

At the other end of the scale, Acta Pal. Pol. did a very fast job: just under one month elapsed after our initial submission of the neck-posture paper before we got back two detailed and helpful reviews accompanying a provisional acceptance.  It took us a fortnight to make the revisions, and only one further week for the revised manuscript to be accepted and in press — seven weeks from start to end, and then a wait of only two and a half months before publication.

Figure reproduction. This varies in importance depending on what kind of paper you’re submitting: for a description, I think it’s really important (which is why Darren and I argued, successfully, with the Palaeontology editor to get full-page reproduction for the Xenoposeidon photographs and interpretive drawings); for a biomechanics paper or similar, it’s maybe not so important, provided the figures are legible.  In terms of electronic figure reproduction, the hands-down winner is the PLoS series of journals: for example, the individual elements surrounding the skeletal reconstruction in the full-sized figure 3 of Sereno et al.’s (2007) description of the skull of Nigersaurus are exquisite.  At the other end of the scale, one of the big disappointments with Palaeontologia Electronica is the figure quality: for example, Rose’s (2007) description of Paluxysaurus has really tiny online images of the figures — something there’s no real excuse for in an online-only journal.

Length restrictions/page charges. Some journals charge the author per printed page; some charge per page after a certain number of free pages.  The charges, and the number of free pages, vary wildly between journals.  Some, maybe most, journals will waive these fees for authors with no institutional support.  Need I say that you want to find a journal that won’t charge, or will charge only a little?

(For journals that take away your copyright and restrict your use of your own work, I think that charging as well adds insult to injury.)

Reprint costs. Before the advent of ubiquitous PDFs, the main way to disseminate your work apart the journal issue itself was by buying reprints from the journal and handing them out to colleagues at conferences.  Reprint costs also very wildly between journals.  This used to be more important than it is now, as we have other ways of letting people see our work.

Wide distribution of physical issues. If your article is in Science or Nature, then a zillion copies will be printed and sent all over the world.  If you publish in The Biennial Newsletter of the South Yorkshire Lepidopterists’ Society, eight copies will be photostatted and sent as far afield as North Yorkshire.  So you might think that wide distribution correlates strongly with prestige, but that’s not always true.  A nice outlier here is PaleoBios: copies are sent to libraries all over the world, in exchange for copies of other institutional journals, which means that anything published in PaleoBios can be found in hardcopy in a surprising number of places.  This is nice; but as with reprints, less important than it was even a few years ago.  And the reason is …

Existence of PDFs. Finally we get to the bit that we’ve all known was coming.  In this enlightened day and age, most of us have several metric shedloads of papers in PDF form on our hard drives, meaning that whenever we go to a musuem with our laptops and want to compare an alleged basal titanosauriform median caudal with those of Brachiosaurus brancai, we have only to pull up the PDF of Janensch (1950) and we’re done.  Lugging around great stacks of actual paper seems not merely unnecessary but passé, like wearing flared trousers or listening to the Spice Girls.  Everyone needs PDFs, and everyone knows that this is the case.  So every publication venue provides authors with them … right?

Amazingly, no.  Things may have changed since 2007, but back then authors had to PAY $100 to the Journal of Paleontology to get a PDF of THEIR OWN PAPER.  Oh, and money orders were only accepted from the USA and Canada, so good luck if you’re a European author.  These facts hurt so much I am going to have to go and lie down before continuing.

… later … Here’s one that hurts even more: Brusatte et al.’s (2008) osteology of the stinkin’ theropod Neovenator DOES NOT EXIST as a PDF, except for a crappy scan.  Apparently the Palaeontographical Society doesn’t give the authors PDFs at all, at any price.  For me, that is a simple, non-negotiable Submission Killer: I will never, ever send my stuff to a venue that doesn’t give me a PDF.  In 2009, the idea is untenable.

Open access. Assuming that a PDF exists, who can get it and under what terms?  Under the classical model, publishers own your work, and can — and do — restrict access to it.  To see what you wrote, other scientists, and interested amateurs, have to either have an institutional subscription or pay some ludicrously inflated fee like $30.  (I wonder whether anyone in world history has ever done this?)  See Scott Aaronson’s rather brilliant article for more on this extraordinary state of affairs.

In contrast, an increasing number of journals are now open access, which means that anyone, anywhere can download the PDF with minimum fuss and at no cost.  Acta Palaeontologia Polonica is one of these, and was among the first in palaeo.  Other notable journals in this category include PLoS Biology and PLoS ONE, and Zootaxa.  If you’re prepared to wait a year before your paper becomes open access (i.e. wait until everyone who’s interested has long had a copy and all the buzz has died down so that no-one cares any more), then the list of open access journals grows to include venues like Science and Proc. B, but personally I am inclined to feel that this is stretching the definition well past breaking point.  There are good and valid reasons for wanting to publish in these venues, but their open-access-but-not-in-any-way-that-matters policy is not one of them.

There are (at least) two reasons to favour open-access journals: the pragmatic one is that it’s the best way to make sure that anyone, anywhere in the world who’s interested in your work can get it — whether professor, curator, student, interested amateur or vaguely interested high-school kid.  The other reason is that it’s just right.  We’re talking here about the world’s accumulated knowledge, in many cases acquired by publicly funded research programs.  It is simply and plainly wrong that this work should be shut up behind paywalls where the people who paid for it can’t see it.

Copyright retention. Most publishers, including some open access publishers, require the author to sign over copyright as a condition of publication.  Even if it doesn’t make much difference in practice, I have to say it rankles that, for example, that the Palaeontological Society has ended up owning my and Darren’s work on Xenoposeidon (Taylor and Naish 2007).  This is particularly iniquitous in unashamedly commercial publishers such as Elsevier — guess who owns Darren’s paper on “Angloposeidon” (Naish et al. 2004)?  And it’s even more baffling in open-access journals since they let anyone have the work anyway.  I assume the real reason for this is that publishers want to be able to exploit any spin-offs such as popular books, but copyright transfer forms usually contain a lot of blurfl about it being for the author’s benefit, as it allows the publisher to pursue infringement claims on the author’s behalf.  To which I offer the following rebuttal: “yeah, right”.

Not all publishers do this.  Notably, we retain the copyright on our recent paper in Acta Pal. Pol., Zoologica Scripta leaves copyright with the authors, and there are others.  Good for them.

… and finally, you do need to be realistic. Despite my whining about Science and Nature above, I don’t deny that we’d have loved to place the neck-posture paper at one of those journals: apart from anything else, it would be useful for Matt as he works towards tenure, and helpful for Darren who — astoundingly — is still without a job in academia.  S‘n’N papers help with that stuff.  But we know (these journals make no secret of it) that they reject 90% of submissions without even reviewing them, and it would likely just have been a waste of our time and effort to lobotomise our eight-pager down to three and reformat with the ultra-dumb numbered-references format in exchange for a tiny, tiny chance of hitting that jackpot.  So we didn’t bother.  (Also, while scientists strive to evaluate work on its merits, I can’t help suspecting that a submission to the tabloids with University of Portsmouth and Western University of Health Sciences in the byline would have started with something of a handicap in the selection process.)

What it all means

So apart from having suggested you ignore Impact Factor, I’ve said to consider prestige, reprint costs, distribution of physical issues, existence of PDFs, open access, copyright retention, turnaround speed, figure reproduction and length restrictions/page charges.  And the interesting thing is that the first half dozen of these are all about the same thing, which I’d argue is the underlying issue:

Getting the paper read by as many people as possible.

That’s what it’s really about, isn’t it?  The reason you want cheap reprints is so you can give them to people who’ll read them; the reason you want wide distribution of physical issues is so they’ll get into libraries where people will read them; and so on.

But both reprints and physical issues are much less important than they used to be, because now we can email our stuff to anyone in the world.  So let’s ignore them for now.  Prestige is less important than it used to be, because one of its big wins was that it got your article into the hands of potential readers; but it’s still important in other ways. And let’s ignore journals that don’t give you PDFs because they are off the Submission Radar.

Now here’s another thing:

Everything is open.

It just is, and there’s nothing that anyone can do about it.  Everything that becomes available as a PDF is quickly passed around the community, and in most cases posted on the author’s web-site (whatever the journal’s Arbitrary And Exploitative Copyright Transfer Form said).  So from a purely pragmatic perspective, you could say that in choosing a journal we can also ignore the criterion of whether or not the journal considers itself open access (because it really is anyway) and also copyright retention (since it doesn’t really matter if everyone can read it anyway).

So what criteria are we left with?  Of the ten we started with, those left standing in the era of ubiquitous PDFs number just four: prestige, turnaround speed, figure reproduction quality and length restrictions/page charges.  And this is excellent, because these are the actual services that journals provide to authors.  A journal best serves authors by handling their manuscripts quickly and without charge, by imparting prestige due to the reputation of the editorial board and quality of previous issues, and by reproducing the figures well.  I think it’s great that we’re moving inexorably towards an economy where the journals that get the best submissions will be the ones that provide the best services.

And among journals that do these things well, it’s fairer to reward the good buys by bestowing our submissions on those that are deliberately publishing open access rather than those that try to stop people reading what they “publish” (which, of course, is ironically the very opposite of what the word is supposed to mean, i.e. making something available).  There are some non-open journals that you sort of have to publish in — I don’t feel my CV would be complete without papers at JVP and Palaeontology — but aside from those society-owned journals (and, OK, museum journals), I am planning to pretty much stick to open access venues from here on.

In Praise of Acta Pal. Pol.

I’ll finish by mentioning that Acta Palaeontologia Polonica does offer a very good blend of the qualities we’re looking for in a publication venue: it’s open access by design (and has been for years), turnaround is very fast, the figure reproduction is good (though perhaps not stellar), and the page charges of 27 Euros per page over the first eight are not unreasonable.  (It also has cheap reprints and is widely distributed, but we’re ignoring those factors, remember?)  Finally, the journal has a well-earned reputation for publishing good papers and for reviewing them well.  So all in all, we’re really pleased with APP and would definitely use it again.

References

• Brusatte, Stephen L., Roger B. J. Benson, and Stephen Hutt.  2008. The osteology of Neovenator salerii (Dinosauria: Theropoda) from the Wealden Group (Barremian) of the Isle of Wight.  Monograph of the Palaeontographical Society 162 (631): 1-166.
• Curry Rogers, Kristina and Catherine A. Forster.  2001.  The last of the dinosaur titans: a new sauropod from Madagascar. Nature 412: 30-534.
• Hutchinson, John R. and Garcia, Mariano.  2002. Tyrannosaurus was not a fast runner.  Nature 415: 1018-1021
• Hutchinson, John R., Frank C. Anderson, Silvia S. Blemker, and Scott L. Delp.  2005.  Analysis of hindlimb muscle moment arms in Tyrannosaurus rex using a three-dimensional musculoskeletal computer model: implications for stance, gait, and speed. Paleobiology, 31(4): 676-701.
• Janensch, W. (1950). Die Wirbelsaule von Brachiosaurus brancai. Palaeontographica (Suppl. 7) 3: 27-93.
• Naish, Darren, David M. Martill, David Cooper and Kent A. Stevens.  2004.  Europe’s largest dinosaur?  A giant brachiosaurid cervical vertebra from the Wessex Formation (Early Cretaceous) of southern England.  Cretaceous Research 25: 787-795.
• Rauhut, O. W. M., K. Remes, R. Fechner, G. Cladera, and P. Puerta. 2005.  Discovery of a short-necked sauropod dinosaur from the Late Jurassic period of Patagonia. Nature 435:670-672.
• Rose, Peter J.  2007.  A new titanosauriform sauropod (Dinosauria: Saurischia) from the Early Cretaceous of central Texas and its phylogenetic relationships.  Palaeontologia Electronica 10 (2): 8A.
• Schwarz, Daniela, Eberhard Frey and Christian A. Meyer.  2007. Pneumaticity and soft-tissue reconstructions in the neck of diplodocid and dicraeosaurid sauropods.  Acta Palaeontologica Polonica 52 (1): 167-188.
• Sereno, Paul C., Allison L. Beck, Didier. B. Dutheil, Hans C. E. Larsson, Gabrielle. H. Lyon, Bourahima Moussa, Rudyard W. Sadleir, Christian A. Sidor, David J. Varricchio, Gregory P. Wilson and Jeffrey A. Wilson.  1999.  Cretaceous Sauropods from the Sahara and the Uneven Rate of Skeletal Evolution Among Dinosaurs.  Science, vol. 282, pp. 1342-1347;
• Sereno, Paul C., Jeffrey A. Wilson, Lawrence M. Witmer, John A. Whitlock, Abdoulaye Maga, Oumarou Ide and Timothy A. Rowe.  2007. Structural Extremes in a Cretaceous Dinosaur. PLoS ONE 2 (11): e1230 (9 pages).  doi:10.1371/journal.pone.0001230
• Stevens, K. A., and Parrish J. M., 1999, Neck Posture and Feeding Habits of Two Jurassic Sauropod Dinosaurs: Science, 284: 798-800.
• Taylor, Michael P. and Darren Naish.  2007.  An unusual new neosauropod dinosaur from the Lower Cretaceous Hastings Beds Group of East Sussex, England.  Palaeontology 50 (6): 1547-1564.  doi: 10.1111/j.1475-4983.2007.00728.x
• Taylor, Michael P., Mathew J. Wedel and Darren Naish.  2009.  Head and neck posture in sauropod dinosaurs inferred from extant animals. Acta Palaeontologica Polonica 54(2): 213-220.

X-Men Origins: Pneumaticity

The respiratory system of a pigeon injected with pink latex. Click for the unlabeled gory version.

In case you’ve missed it, William Miller has been asking some great questions over in the comment thread for “Brachiosaurus: both bigger and smaller than you think“. Here’s his most recent, which is so good that the answer required a post of its own:

…in birds, the air sacs are obviously useful for flight, and they might have been useful for weight lightening in sauropods: but the common ancestor would have been flightless and too small to need the lightening. So what drove their evolution in the first place, I wonder?

To which I say: oh, Alice, the rabbit hole is a lot deeper than that.

Introduction to the Three Mysteries

First, in birds the diverticula that enter the bones are a comparatively small subset of all diverticula. Visceral, intermuscular, and subcutaneous diverticula run between the guts, between muscles, and under the skin, respectively. These are usually more numerous and more extensive than the diverticula that enter the bones, and with rare exceptions, like the subcutaneous “bubble wrap” in pelicans, we have no idea what they do. If, indeed, they do anything. All a character needs to do to be hereditarily propagated is not compromise the survival and reproduction of its bearer. Diverticula could be mostly functionless products of developmental processes that are usually invisible to selection but sometimes produce useful exaptations, like lightening the skeleton, insulating the body, etc. Sort of the evolutionary equivalent of the fire extinguisher in your kitchen: most of the time it does absolutely nothing, but once in a while it is really, really useful.

Second, postcranial skeletal pneumaticity (PSP) starts in the cervical vertebrae in basal theropods and sauropodomorphs, and possibly also in pterosaurs (Butler et al. 2009). The vertebrae adjacent to the lungs and air sacs are not the first to be pneumatized. Rather, the pneumatic diverticula must have gotten out of body cavity and traveled a ways before they started impacting the skeleton. Assuming that one thing had to come before another and it didn’t happen in one saltatory leap, diverticula must have evolved before they started pneumatizing the skeleton.

Third, in the earliest evolutionary stages of pneumatization in saurischians, the amount of bone removed is completely negligible. In Wedel (2007) I calculated that in Pantydraco (Thecodontosaurus caducus at the time) and Coelophysis the pneumatic spaces in the bones accounted for 0.0017% and 0.17%, respectively, of the body volumes. The fossae in the Pantydraco vertebrae are not absolutely diagnostic for PSP, but they’re in the right place and hard to explain otherwise. The holotype individual is a juvenile, and it is possible that PSP might have been more extensive in an adult, but it could increase one hundred-fold and still only be 1/500 of the animal’s volume, as in Coelophysis. Although I haven’t run the numbers, a similar result probably hold for the basalmost sauropods with definitive PSP.

Pneumatic fossae in the cervical vertebrae of Coelophysis

To sum up:

1. Most diverticula in birds are not involved with pneumatizing the skeleton, so PSP can’t be the reason for their existence.
2. In basal saurischians, the diverticula that pneumatized the skeleton must have evolved before they could start pneumatizing the skeleton, so PSP can’t be the reason for their existence, either.
3. In the early stages of the evolution of PSP in saurischians, the amount of mass saved was negligible and could not plausibly have influenced natural selection, so PSP didn’t initially evolve to lighten the skeleton.

Lighten Up, Fatso

There is a complication on that last point, which requires a little digression on fat.

In birds, pneumatic diverticula don’t just replace bone tissue, they also take up space that would be occupied by fat in mammals, for example in the spaces between muscles and around plexuses of nerve and blood vessels. Any of you who have had the misfortune to dissect the brachial plexus of a mammal know whereof I speak–you spend most of your time carefully picking fat out from around the nerves and blood vessels. This isn’t gross subcutaneous fat that means an animal or person is obese, this is adipose tissue doing its other job of being a lightweight packing material. Mammal bodies put fat in those spaces because they need to occupied by something light and squishy and fat is the cheapest thing your body can build.

That may seem backwards; we think of fat as an energy store and therefore energetically expensive. But it’s cheaper to build than muscule or cartilage or skin, and lighter than any other tissue or fluid in the body. It has been observed that even when mammals are starving, they do not use the fat in the yellow marrow that fills the marrow cavities of long bones. This is utterly unsurprising if you think about how bodies work. Nature really does abhor a vacuum, at least biologically (cosmically, it seems to be the biggest thing ever). If a starving body used the fat in the marrow cavity, it would have to replace it with something else, and all of the alternatives are heavier and more expensive to build. If the fat was not replaced, a partial vacuum would develop which would cause serous fluid to weep into the space, and that would also be heavier and more expensive, and a great site for infection to boot (ask someone who has an edema).

Birds cheat the system by replacing the lightest of tissues with something even lighter: air, held in diverticula that are basically super-thin layers of epithelium. Possibly diverticula had been running around replacing fat for a long time before they first entered the skeleton, in which case the earliest stages of pneumatization would have been a continuation of pre-existing function of replacing superfluous connective tissue (fat and bone are both forms of connective tissue, along with cartilage, ligaments, tendons, mesenteries, fascia, and blood; blood is connective tissue the way snakes are tetrapods).

Although that will be difficult or impossible to test, it actually makes quite a bit of sense. Getting fat out of the way ought to be easy; the lipids can be mobilized into the bloodstream and the flattened cells could either be pushed out of the way or resorbed. Getting bone out of the way requires increasing parathyroid hormone, mobilizing blood-born multinucleated osteoclasts, and convincing them to digest bone where it needs to be digested, which I assume is a more complicated process from a regulatory standpoint (physiologists or cell biologists, please correct me if I’m wrong!). So it seems plausible that diverticula might have acquired the ability to replace fat early on, and the ability to replace bone much later, and that by the time they got started on the skeleton diverticula could have been lightening the body for a long time by removing little bits of superfluous fat.

This does not contradict my statement above that by and large we don’t know what diverticula do. Some diverticula run where there is no fat to replace. And healthy birds do carry some fat, like any healthy tetrapod. One would think that this energy-reserve fat would need to be protected from diverticula that would otherwise resorb it, but I don’t know how or if that happens, and I don’t know if anyone else does either. The amount of research on diverticula is basically nil.

I also think that fat-resorbing diverticula don’t solve the third mystery, they just pushes it back a level. The amount of mass saved by replacing the “packing” fat with air is probably negligible in most animals, and it certainly would have been so in the earliest stages of replacement, so the third mystery still holds if it  is restated as:

3b. In the early stages of the evolution of diverticular replacement of connective tissue in saurischians, the amount of mass saved was negligible and could not plausibly have influenced natural selection, so PSP didn’t initially evolve to lighten the body.

A dorsal vertebra of Haplocanthosaurus in anterodorsal oblique view. It's pneumatic, sure, but not THAT pneumatic.

The Problem is the Solution

So, we seem to be stuck. We don’t know why diverticula evolved in the first place, and we don’t know what most diverticula do, and even the diverticula that lighten the body could not have initially evolved to do so.

One upshot of all this is that we need more research on possible  physiological functions of diverticula in birds. Oy! Ornithologists and avian physiologists! We’ve thrown you a bone, now throw us some data. Please?

Another upshot is that the erratic evolutionary pattern of PSP in Triassic and early Jurassic ornithodirans is maybe not entirely unexpected. Pterosaurs and theropods seem to have had PSP right out of the gate, but at least in theropods it was not enough to have done any good. Basal sauropodomorphs had little or no PSP, and not enough to have done any good below about the level of Eusauropoda. No non-dinosaurian dinosauromorphs have been found with PSP, but then we only have a handful of them and they’re all pretty dinky, so it’s possible it just hasn’t been recognized yet. Silesaurids, at least, had very pronounced, very thin laminae, which in derived saurischians are almost always associated with PSP. And ornithischians never had PSP at all, as far as we know.

My opinion is that an air sac system is probably primitive for Ornithodira, and that most of these lineages had pneumatic diverticula, but the speed with which they “discovered” extensive, skeleton-lightening PSP–ranging from “almost immediately” in pterosaurs to “after a while” in theropods to “after a long while” in sauropodomorphs to  “never” in ornithischians–varied because it was such an evolutionarily haphazard process. Basically, PSP had to evolve as a developmental accident, and in some lineages it got far enough to become visible to selection, and in others it did not, or took a long time to do so. That’s a pretty picture that makes a lot of sense to me. If I ever figure out a way to test it, I’ll let you know.

What's going on here? Why are ornithischians so lame?

The Solution is the Problem

The absence of PSP in Ornithischia is still a right sod. Pterosaurs, theropods, and sauropodomorphs all evolved some level of PSP in the Late Triassic, even if it wasn’t enough to significantly lighten their skeletons at first. Why not ornithischians? If air sacs are primitive for Ornithodira, then ornithischians had the gear for 160 million years and never exploited it, when the other three major lineages of ornithodirans discovered PSP pretty fast out of the gate. And if air sacs are not primitive for Ornithodira, three out of four ornithodiran lineages still discovered PSP on their own, so why not Ornithischia? It’s a big mystery, any way you slice it.

What do you think?

References

• Butler,  R.J., Barrett, P.M., and Gower, D.J. 2009. Postcranial skeletal pneumaticity and air sacs in the earliest pterosaurs. Biology Letters. doi:10.1098/rsbl.2009.0139
• Wedel, M.J. 2007.What pneumaticity tells us about ‘prosauropods’,
  and vice versa. Special Papers in Palaeontology 77:207–222.

Brachiosaurus: both bigger and smaller than you think

I made this, just for the heck of it.

The critters are, from left to right:

• OMNH 53062, the holotype of Sauroposeidon proteles, with a reconstructed skeleton grayed in;
• HM XV2, a fibula of Brachiosaurus brancai, which represents the largest known individual of Brachiosaurus;
• HM SII, the nearly complete mounted composite skeleton of Brachiosaurus brancai in Berlin;
• a 20-foot-tall, world record giraffe;
• a 6′2″ human being, such as myself.

The vertebrae of Sauroposeidon are about a third longer than their counterparts in HM SII, but only about 15% larger in diameter. I have therefore always scaled up the body of Sauroposeidon by only 15% relative to HM SII. It may have been bigger or smaller, I’m just trying to follow what few numbers I have to go on as slavishly, and conservatively, as possible. Sauroposeidon is shown here with a more vertical neck than Brachiosaurus because that’s how I had the necks posed in the  two separate skeleton reconstructions before I decided to combine them, and I’m lazy, and that’s not the point of the post anyway.

The point of the post, or the first point anyway, is that almost everyone, everywhere, at all times underestimates the size of Brachiosaurus. This is because of the immense influence of the HM SII mounted skeleton. Practically every estimate of length or neck length or browsing height or mass or anything else for Brachiosaurus is based on that one skeleton. But we know that there were bigger individuals of Brachiosaurus roaming around, like HM XV2, which was 12-13% larger. Not only that, but we can be pretty certain that HM SII was not fully mature because the scapula and coracoid are unfused, and we know these elements are fused into a single scapulocoracoid in mature brachiosaurids. So between SII being not all grown up and XV2 being considerably bigger, we ought to think of XV2 and not SII when we think about big Brachiosaurus was.

Now, 12-13% might not seem like much, but it’s considerable. It’s the difference between me (6′2″) and someone seven feet tall. HM SII has a neck 8.5 meters long; that of XV2 would have been 9.5 meters long, which is longer than the neck of the holotype of Mamenchisaurus hochuanensis (9 m), but shorter than the estimated neck length of Mamenchisaurus sinocanadorum (~12m).

Crucially, XV2 would have massed 1.4 times as much as SII (1.125^3, because mass depends on volume, which scales with the cube of length). That holds true no matter how much you think SII weighed. If SII had a mass of 40 tons, then XV2 was 56 tons; if SII was 30 tons, XV2 was still 42 tons.

Maybe the most interesting thing about this is that, so far as we can tell, XV2 was almost exactly the same size as the holotype individual of Sauroposeidon. So anything I or anyone else has written about Sauroposeidon being bigger, absolutely, than Brachiosaurus, is bobbins. Sauroposeidon still had a considerably longer neck, 11.5 meters to XV2’s 9.5, but the cervical skeleton weighed about the same thanks to the higher air space proportion in Sauroposeidon. In fact, if the higher ASP of Sauroposeidon applied to the rest of the vertebral column, then the holotype individual of Sauroposeidon might have weighed less than XV2!

The evolutionary upshot is that, as far as we can tell, big brachiosaurids stayed about the same size from the Kimmeridgian-Tithonian (Late Jurassic) to the Aptian-Albian (Early Cretaceous). Maybe they hit some kind of limit, but I doubt it, because Argentinosaurus was probably a lot heavier and Bruhathkayosaurus and Amphicoelias would have knocked any known brachiosaurid right out of the park. I think it is more likely that the debits imposed by large body size finally caught up with the selective advantages of same, within that lineage (but not at the same point within other lineages). Whatever the reason, the biggest known brachiosaurid didn’t get any bigger than Brachiosaurus. Which puts the evolution of the longer, more pneumatic neck in Sauroposeidon into a new light. It might have been a cheat, an evolutionary hack to overcome a limit on whole-body growth, even if that limit was a ’soft’ one imposed by balanced selection pressures in both directions. That’s sort of assuming that Sauroposeidon was just Brachiosaurus with a redesigned front end, but the weirdness we see in the vertebrae might have extended to the rest of the animal. We won’t know until someone digs up some more specimens. Sigh.

The second point of the post is that, as indicated by the title, Brachiosaurus might have been smaller than we commonly think. Since the 1980s there have been a couple of ~30 ton estimates out there for HM SII, one by Anderson et al. (1985) based on limb bone allometry and one by Paul [1988] based on volumetrics (I have to put 1988 publication dates in brackets rather than parentheses or mrrfin’ frrfin’ WordPress automatically changes the 8 and the ) to a smiley, dammit). I think that by and large people have gotten pretty comfortable with the idea that SII was a 30 ton  critter.

But it might–might–have been quite a bit lighter. Paul (1997) assigned the neck a density of 0.6 g/cm^3 and the torso a density of 0.9 g/cm^3. Those are probably too dense. Some birds have necks as un-dense (sparse?) as 0.3 g/cm^3, and that does not strike me as unreasonable for sauropod necks given the amount of pneumaticity indicated by the skeleton. The lungs and air sacs of birds can account for up to 20% of the volume of the body. Not of the torso, of the whole body. And based on my calculations for derived theropods and sauropods, up to 10% of the whole-body volume was occupied by air in the pneumatic bones. That’s 10% in addition to the 20% for the lungs and air sacs, or 30% of the whole body  volume. That would give a whole-body density of about 0.7 g/cm^3, which is in fact what has been found for some birds.

I got 0.8 g/cm^3 for the whole-body density of Diplodocus in my 2005 paper, and other authors have since used that number for other sauropodomorphs. That’s gratifying, but it’s probably wrong. I erred conservatively at every possible point in that calculation and just flat left out some known air spaces whose volume I could not reliably estimate (e.g., vertebral diverticula outside the vertebrae). I also used 10% rather than 20% for the part of the whole-body volume occupied by the lungs and air sacs, because values as low as 10% have been reported for some birds and I was being conservative. But I don’t think that bird-like densities around 0.7 g/cm^3 are unrealistic for sauropods; in fact, I’d be surprised if the really pneumatic ones–like big brachiosaurids–weren’t about that sparse.

And speaking of big brachiosaurids, Henderson (2004) used computerized volumetrics and a density of 0.8 and got a mass of 25.8 tons for HM SII. If the density was really 0.7 that would shave off an additional 10% and bring the mass down to 22.7 tons. That’s getting crazy light; it’s about half of what Bakker and Alexander were proposing for Brachiosaurus in the mid-80s. And it’s still a quarter lighter than what Anderson (1985) and Paul [1988] got.

So, for the sake of argument, let’s say that HM SII did mass only 22.7 tons. That would give XV2 a mass of 32 tons, and Sauroposeidon a mass of only 34.5 tons without taking any additional pneumaticity into account.

That seems totally nuts. But every step is defensible*, and it might even be true.

* That means if you want to tear me a new one in the comments because teh Brachiosaurus wuz 50 tons!!!1!!111!, please be sure to specify which links in the chain of inference you disagree with, and why.

References

• Anderson, J. F., A. Hall-Martin, and D. A. Russell. 1985. Long-bone circumference and weight in mammals, birds and dinosaurs. Journal of Zoology 207:53-61.

• Henderson, D. M. 2004. Tipsy punters: sauropod dinosaur pneumaticity, buoyancy and aquatic habits. Proceedings: Biological Sciences 271 (Supplement):S180-S183.

• Paul, G. S. 1988. The brachiosaur giants of the Morrison and Tendaguru with a description of a new subgenus, Giraffatitan, and a comparison of the world’s largest dinosaurs. Hunteria 2(3):1-14.
• Paul, G. S. 1997. Dinosaur models: the good, the bad, and using them to estimate the mass of dinosaurs; pp. 129-154 in Wolberg, D. L., Stump, E., and Rosenberg, G. (eds.). Dinofest International: Proceedings of a Symposium Sponsored by Arizona State University. Academy of Natural Sciences, Philadelphia, 587 pp.