Unbelievably, despite the fact that it is one of my favorite places in the world, despite the fact that it is just 10 fast hours away by car, across some of the most desolate and beautiful country on the planet, I have not been to BYU since the fall of 2005.

The highlight of my last trip was spending a little quality time with the Dry Mesa Supersaurus cervical. You’ve seen it here before so you know it’s dimensions…sorta. As I am always saying, there is a big difference between knowing something in your head and knowing it in your gut. So here are a couple of gut-level facts about this vert.

First, it’s so darn big that once the forklift has it down from it’s shelf, it can’t turn or maneuver, and the driver has to crawl out through the window (true; I watched him do it). I have no idea how they got this thing up there in the first place. It’s not there anymore, it’s been moved to the gigantic shiny white new big bone storage room (a.k.a. the Vault of Awesome) that was just about completed when I was there last. How they moved it is another mystery, since the forklift can’t turn.

Second, if you want to get it all in one frame with minimal distortion, you have to get up on a very tall ladder and shoot straight down. Which I did. The scale bar is in cm (top) and inches (bottom).

This is one of my hand-full of favorite fossils in the world, and I’m looking forward to seeing it again in its new home. The barn it was in before was not air-conditioned, and the two hours I spent in there on a hot August afternoon had me sweating like a fat kid in a garbage sack. But it was more than worth it. Dirty is temporary. Science last forever (or close enough for me).

STOP THE PRESSES!! (May 7)

The paper describing the new Supersaurus specimen from Wyoming has finally been made public. It’s Lovelace et al., with a claimed date of 2007, which for all I know is when the thing actually came out. I’d appreciate details on that from those in the know. In any case, the paper is freely available by emailing co-author Scott Hartman on dinoboygraphics@aol.com - I haven’t even had a chance to read it yet, but I salute the authors for getting it out, and salute them for offering it to interested parties. Everyone should be so kind.

So, you’ll all recall the previous post where we looked at the absurdly broad neck base of the Upper Jurassic macronarian Camarasaurus. This time round we’re playing the same game, but looking up at the neck base of the diplodocoid Diplodocus, and again it is of course the Natural History Museum’s (London) mount of the Carnegie cast of D. carnegii (image © NHM). Note how elongate and narrow the centra are: the length-to-width ratio of sauropod cervical vertebrae has proved to be a useful character, and was formalised as the ‘EI’, or elongation index, by Paul Upchurch (1998). However, EI has also been used as centrum length-to-height by other sauropod workers (Wilson & Sereno 1998, Wedel et al. 2000), and this is the version we’re using here. The EI of Diplodocus is reasonable, ranging from 3.1 to 4.7 between C2 and C6, and with a maximum of 4.9 in C7, but it is exceeded by that of brachiosaurs (where it can be over 5.0 and even over 6.0), and - among diplodocoids - by those of Barosaurus, Australodocus and Supersaurus (where the EI ranges to an incredible 7.5). Erketu and a few other particularly long-necked taxa also have particularly high EIs. Note that the ventral surfaces of the centra are shallowly concave and lack any sort of midline ridge - these details are variable among sauropods, with some having flattened bases and some having low midline keels.

Finally for now, note also that the cervical ribs are not making contact with one another: a very basic observation which makes a mockery of the idea that the ribs somehow propped up the neck from underneath. Some sauropod workers have actually proposed this (Martin et al. 1998), in part because (I think) there seems to be an assumption among some scientists that bizarre products of evolution - like the incredible necks of sauropods - must have operated in bizarre and novel ways. That might sound like a reasonable position, but it is in fact countered by the evidence: so far as we can tell, sauropod necks worked much like those of other saurischian dinosaurs, and they were not off-the-scale whacky bizarre in terms of morphological innovation. More on this topic in the future, oh yes.

References

• Martin, J., Martin-Rolland, V. & Frey, E. 1998. Not cranes or masts, but beams: the biomechanics of sauropod necks. Oryctos 1, 113-120.
• Upchurch, P. 1998. The phylogenetic relationships of sauropod dinosaurs. Zoological Journal of the Linnean Society 124, 43-103.
• Wedel, M. J., Cifelli, R. L. & Sanders, R. K. 2000. Osteology, paleobiology, and relationships of the sauropod dinosaur Sauroposeidon. Acta Palaeontologica Polonica 45, 343-388.
• Wilson, J. A. & Sereno, P. C. 1998. Early evolution and higher-level phylogeny of sauropod dinosaurs. Society of Vertebrate Paleontology Memoir 5, 68 pp.

Othniel Charles Marsh, who was always careful to base all of his hundreds of new taxa on the best, most diagnostic material available (Alert: Sarcasm detected!), named Pleurocoelus nanus based on a handful of junenile sauropod vertebrae centra from the Arundel clays of Maryland (Marsh 1888). Here’s the dorsal. As you can see, it is loaded with unique features like big pneumatic fossae, which at the time were only known in all other sauropods (we have since found some with less pneumaticity in the dorsals, or none at all), and the absence of a neural arch, which is shared with any sufficiently immature vertebrate.

Here’s a cervical, which was not figured by Marsh (1888). These views are after Lull (1911:pl. 15), as modified by Wedel (2003:fig. 10); pfs stands for pneumatic fossa.

And a sacral, again from Marsh (1888).

To be fair, the criteria for “diagnosably distinct” in the 1880s were different than they are now. Wilson and Upchurch (2003) addressed this in their revision of Titanosaurus: as we find and describe more fossil taxa, characters that originally diagnosed small taxonomic groups (like species and genera) are often found to be more broadly distributed. For example, the original diagnosis of Titanosaurus ended up applying to almost everybody in the clade Titanosauria. It is conceivable that in the future we will discover an entire clade of xenoposeidonids with identical weird dorsals and all of their diagnostic characters elsewhere in the skeleton, and the longish list of weird characters that diagnose Xenoposeidon will turn out to be present in all xenoposeidonids. There’s not much we can do about this, other than to keep working, revisit old diagnoses from time to time and see if they need updating, and generally be nice about it.

I am cool with not being nice about Pleurocoelus, though, because of what happened later. But that’s a story for another post.

Note: In 2005 Carpenter and Tidwell sunk Pleurocoelus into Astrodon, which is totally cool by me, and which makes Astrodon the correct name for the poorly-known Arundel titanosauriform, just like Apatosaurus is the correct name for the Morrison diplodocine that is built like a brick outhouse. But in this series I am Telling a Tale about the Days of Yore, past tense, pre-2005, so I’m using Pleurocoelus.

References

• Carpenter, K., and Tidwell, V. 2005. Reassessment of the Early Cretaceous sauropod Astrodon johnsoni Leidy 1865 (Titanosauriformes). Pp. 78-114 in. Tidwell, V., and Carpenter, K. (ed.) Thunder-lizards: The Sauropodomorph Dinosaurs. Indiana University Press, Bloomington.
• Lull, R.S. 1911. Systematic paleontology of the Lower Cretaceous deposits of Maryland: Vertebrata. Lower Cretaceous Volume, Maryland Geological Survey, 183–211.
• Marsh, O.C. 1888. Notice of a new genus of Sauropoda and other new dinosaurs from the Potomac Formation. American Journal of Science, 3rd Series 35:89-94.
• Wedel, M.J. 2003. The evolution of vertebral pneumaticity in sauropod dinosaurs. Journal of Vertebrate Paleontology 23(2):344-357.
• Wilson, J.A., and Upchurch, P. 2003. A revision of Titanosaurus (Dinosauria – Sauropoda), the first ‘Gondwanan’ dinosaur genus. Journal of Systematic Palaeontology 1:125–160.

It is a strange fate that we should suffer so much fear and doubt over so small a thing.

Such a little thing….

–

Prepare yourselves, true believers. Pleurocoelus is coming!

I’m going to exploit this site to post a (very rare) off-topic book recommendation. So here it is: The Variety of Life — a survey and a celebration of all the creatures that have ever lived, by Colin Tudge.

I’ve just finished reading this hefty book — 684 pages in the paperback edition — and I’ve found it fantastically invigorating. I’ve often bemoaned how stupidly over-specialised my zoological knowledge is: really, outside the realm of mid-to-posterior neosauropod dorsals, I am pretty darned hopeless, and Darren’s effortless mastery of pretty much every tetrapod group leaves me awestruck. Having come to the end of this whistle-stop tour of the whole of Biota — three domains, more kingdoms than you can shake a stick at, and hundreds of freakier lifestyles than I’d ever imagined — I’ve come to realise what a tiny and parochial corner of biology we inhabit here at SV-POW! towers.

The book is in two and a half sections. Part 1 consists of five chapters (90 pages or so) on the history and philosophy of biological classification, an outline of cladistic methodology and molecular biology techniques and a plea for a rather odd taxonomic approach that he terms “Neolinnaean Impressionism”, and which amounts to a PN-like naming of the nodes but with Linnean ranks arbitrarily imposed on some though not all of the nodes. While Tudge is not strongly attached to the idea that sister groups must have equal rank, he clearly has inclinations in that direction, resulting in several monogeneric “kingdoms” and some odd maneouvering towards the end of the book where he seems to consider Proboscidea and Coleoptera of equal importance for conservation purposes because they are both of rank “order”. *cough*. Well, let’s pass swiftly on.

Part 2 of the book, and by far its bulk, is the survey of all living creatures — 25 chapters covering Biota in 500-odd pages, broken down as follows: one chapter on how the old “two kingdoms” became “three domains”, one chapter briefly covering both Bacteria and Archaea, one on basal eukaryotes, one on fungi, a whopping eighteen on animals, and three on plants. Finally, part 3 is an “epilogue” concerning the need for conservation, the efficacy of various strategies and finally the reasons we should care.

Parts 1 and 3 have some interesting material, to be sure, but the survey is the heart of the book in every way. You can get some sense of how much ground it covers by reading the following paragraph from p. 430:

The Sauropodomorpha includes the Prosauropoda and the Sauropoda — the most famous examples of the latter being the huge herbivorous brachiosaurs of the Brachiosauridae, and Diplodocus of the Diplodocidae.

That’s it folks — that’s the entire coverage of sauropods. And it’s not that they get particularly short shrift, either: that’s how most groups are covered. Super-quick, very direct, bam, onto the next one. Because there is so much ground to cover.

So having read this, it’s not as though I particularly feel I have any real understanding of, say, cnidarians, “brown seaweeds” or sea-spiders. But at least I know they’re out there, and I know what it is that I don’t know. I feel richer and wiser (though also more aware of how stupendously ignorant I am) for having read it.

Obligatory Amazon links: UK and USA.

And finally, to keep of the SV-POW! promise, here is a sauropod vertebra picture: but what is it? I’m not giving too much away if I say that it’s an NHM specimen (and therefore their copyright) — but who (apart from Matt and Darren) can tell me what it is?

The answer will follow in a week or two.

Those of you who have been paying attention to my recent posts will have pretty much known this was coming. I’d hate to disappoint you, so here it is:

What you’re looking at here is the first caudal vertebra (i.e. the first tail bone) of Apatosaurus ajax, the newish specimen NSMT-PV 20375 described by Upchurch et al. (2005). The drawings are all from the plates at the end of that lavishly illustrated paper: all I’ve done is composite them. The top row, from left to right, shows the vertebra in anterior, left lateral, posterior and right lateral views. Below the left lateral view is a dorsal view, with the front pointing to the left (as in the left lateral view).

Oddly, the size of this vertebra doesn’t seem to be stated in the paper, but two lines of evidence suggest that it’s about 65 cm in total height. First, measuring the caudal on the skeletal reconstruction that is the frontispiece, and comparing with that figure’s 1m scale-bar, yields a height of 64 cm; second, the neural spine’s height (measured from the ventral margin of the poztzygapophyses) is given in Table 9 as 392 mm, and that extrapolates, using the posterior view figure, to a total height of 665 mm. So about 65 cm, then.

The caudal vertebrae of diplodocids such as Apatosaurus, Diplodocus and Barosaurus are unusually complex for sauropods, having been somewhat “dorsalised”, i.e. taking on some of the complex morphology of posterior dorsals rather than being the rather dull round-centrum-with-a-flat-spine-on-top affairs you get hanging off the rear end of brachiosauruids. You’ll notice that the lateral processes, or “caudal ribs”, take the form of tall, broad plates, so that the middle part of the vertebra is trapezoidal in anterior view. This is as different as can be from the boring, stick-like caudal ribs of Brachiosaurus. (What actually are caudal ribs? So far as I can tell, amazingly, no-one really knows. They might be homologous with the diapophysis of dorsal vertebrae, or with the parapophysis, or perhaps both of them fused, or one or both fused with an actual rib.)

Oh, yes: also in the picture is your coccyx, that is, the four or five bones that make up your vestigial tail. It is, needless to say, contemptible. It’s surprisingly hard to find a reference for how big it should be, but by cross-scaling from illustrations of whole human skeleton and sacra, I’ve come up with a figure of about 2.5 cm, and that’s what I’ve used here. If you want to compare your tail with Apatosaurus’s, remember that Apato had about eighty caudals: they diminish in size posteriorly, of course, but they do stay about the same anteroposterior length for much of the tail. In fact, diplodocids have tremendous tails, something like half the entire length of the entire animal. One of my long-standing bugbears is that the biomechanics of sauropod tails gets almost no attention (except for speculations about whip-cracking) compared with the love and care lavished on their necks. One day, one of us might do something about that.

That concludes our short but humiliating series of abuse directed at your frail human body. I’ll have to come up with something else next time it’s my turn. Hope you’ve enjoyed the ride.

Finally, good news for everyone who was intererested in Matt’s Aegyptosaurus post: he’s made a PDF of Stromer 1932 so you can see that mystery vertebra for yourselves.

Bibliography

• 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.

There seems to be some kind of bell curve associated with sauropods. We get lots of medium-sized ones, but very few babies, mostly disarticulated bits, and very few super-immense ones, which are also mostly disarticulated bits. Puertasaurus is known from two vertebrae. Sauroposeidon is known from 3.5. The holotype of Hudiesaurus is a single vertebra; the referred forelimb is not from the same individual or the same quarry, and there’s no particularly good reason to think it’s from the same taxon. Argentinosaurus is known from a handful of vertebrae and a smaller handful of limb bones.

Bruhathkayosaurus was evidently pretty big, but there’s only one paper on it so far, illustrated with very, um, simple line drawings of some bones and blurry non-orthogonal photos of others. More on that one later, maybe, although none of the preserved elements appear to be verts so it is a little outside our bounds. In any case, Bruhathkayosaurus may be the biggest sauropod known from remains that still exist (may be; by now you should know how much uncertainty that covers).

Then there are the really frustrating ones: the gigapods for which we have no remains left at all. What’s really frustrating is that these might be the biggest of all! The best known of our absent friends is Amphicoelias fragillimus, which Darren has discussed before and which we ought to cover here in the future. The genotype of Amphicoelias is the Diplodocus-sized A. altus, and it’s still around, or at least it was as of October 2006 because that’s when I took the photo above. No one knows what happened to the A. fragillimus vert. It might have gotten lost, or simply crumbled to dust since it was very fragile and it was excavated before the use of consolidant glues became widespread in paleontology (Carpenter 2006).

In the case of Aegyptosaurus, we know exactly what happened to the type material: it was blown to hell and gone, along with the original material of Spinosaurus and Carcharodontosaurus, when Allied bombs hit the museum in Munich in 1944. The type material of Aegyptosaurus baharijensis consisted of some caudal vertebrae and limb and girdle bones from an animal of unspectacular size. But in a curious parallel with Amphicoelias, there is–or rather was–a larger specimen, possibly one that represented a distinct species.

Near the end of the paper in which he described and figured A. baharijensis, Stromer (1932a) mentioned “ein Wirbel eines anderen noch größeren sauropod”, which he said would be described later. I’ll end the suspense right now: it wasn’t. Later that year Stromer published a short paper (1932b) on the sauropod fauna of Africa. That paper also did not describe any giant vertebrae in any detail, but it did include this photo (below).

The original caption reads “Professor Ernst Stromer neben einem Wirbel einer neuen Art von Aegyptosaurus“–Professor Ernst Stromer next to a vertebra of a new species of Aegyptosaurus. Presumably Stromer intended to provide a full description soon after, but it was not to be. The next summer at Bahariya Oasis he was attacked by a crocodile and nearly lost his left leg. In the end Stromer recovered, but only after repeated surgeries and many painful months spent learning to walk again. The wound effectively killed his professional career. Although he lived until 1952, his 1934 paper on Bahariasaurus was his last paleontological contribution. Almost all of the Bahariya Oasis collection was lost to science in 1944, but science lost Stromer himself almost a decade earlier.

So what about that vert? It’s clearly a posterior cervical. Stromer’s left hand is resting on the rib, which is awfully short and awfully high up on the centrum, which indicates that the vertebra is from near the base of the neck. There are other interesting features as well–note the hint of a keel on the bottom of the centrum, which is usually only found in fairly basal sauropods, and the ridges above the postzygapophyses, which put me in mind of Mamenchisaurus.

Also, I suppose you’ll have noticed that the vertebra is freakin’ immense. Frustratingly, neither Stromer nor the vert appear in their entirety, and neither are shown from an orthogonal angle (perils of using a portrait to try to do science, I know). Still, we know that Stromer was a tall man. Werner Janensch once playfully described him as “die bärtige Bohnenranke”–the bearded beanstalk. No one seems to have written down his exact height, and we’re missing his feet in this photo anyway, but from contemporary descriptions he seems to have been several inches over 6 feet. The diameter of the cotyle seems to be about the same as the distance between his shoulder and wrist, which is a good 2 feet in me and I’m only 6′2″. Assuming–well, you know–that would give a cotyle diameter of about 60 cm, which is just appallingly large. The cervico-dorsal vertebrae of the HM SII specimen of Brachiosaurus brancai are about 3/4 that big. Imagine B. brancai scaled up by a third.

It’s a cool thought, but that’s all it is. We don’t know exactly how tall Stromer was. We don’t know how much the vertebra might be foreshortened in this photo. It wouldn’t take much to get our imaginary monster sauropod downsized into being merely interesting instead of completely flabbergasting. And the specimen itself is literally history.

Farewell, Aegyptosaurus sp. We hardly knew you.

References

• Carpenter, K. 2006. Biggest of the big: a critical re-evaluation of the mega-sauropod Amphicoelias fragillimus Cope, 1878. New Mexico Museum of Natural History and Science Bulletin 36, 131-137.
• Stromer, E. 1932a. Ergebnisse der Forschungsreisen Prof. E. Stromers in den Wüsten Ägyptens. II. Wirbeltierreste der Baharîje-Stufe (unterstes Cenoman). 11. Sauropoda. Abhandlungen der Bayerischen Akademie der Wissenschaften Mathematisch-naturwissenschaftliche Abteilung, Neue Folge 10:1-21.
• Stromer, E. 1932b. Die sauropod Fauna Afrikas und seine biogeographical Bedeutung. Monatsberichten der Deutschen Geologischen Gesellschaft 1932:85-91.

Again, another exclusive peek at an interesting specimen: the MIWG.7306 vertebra, aka ‘Angloposeidon’ (Naish et al. 2004). Apologies if, by now, you’re bored of my show-casing of this specimen, but – not only is it the only sauropod vertebra of which I personally have multiple unpublished images – it is also a really nice demonstration of the fact that, even in just a single vertebra, there are multiple interesting, bizarre, and sometimes under-studied or even un-studied details.

What we’re looking at here is the medial (‘inside’) surface of the left postzygapophysis, with the centrum down below the bottom of the image, and the cotyle off to the left (the opposite side of what’s shown here). The image below should help with orientation. The focus of interest is the unusual matrix-filled space in the middle of the image: just what is it? Because it has sharp, clean edges, I am pretty convinced that it’s natural, and I assume it’s a pneumatic foramen. Similar structures are present on the medial side of the right postzygapophysis, and are different in position and shape (Naish et al. 2003, p. 790). We think, based on several lines of evidence, that the space between the postzygapophyses (limited anteriorly by the neural spine) was occupied by an air-sac (Schwarz & Fritsch (2006) called this the interspinal diverticulum), so is this evidence that diverticula from the interspinal air-sac invaded the bodies of the postzygapophyses on their medial sides? If so, was this just a one-off in MIWG.7306, or was it widespread in brachiosaurs, in macronarians, in neosauropods, or even in sauropods as a whole? I admit that I haven’t yet taken the time to check properly, but the big problem is that this part of the vertebra – the medial surface of the postzygapophysis - is rarely figured. Based on what has been published, I have yet to see a similar structure, even in Brachiosaurus (which is very well figured, as sauropods go).

I’m sure that someone is now going to make me look very, very silly. But, whatever. I can’t pretend to know everything. Note that, again, this is a world first. Yes, all of this stuff should be published… and in time in will, in time.

References

• 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.
• Schwarz, D. & Fritsch, G. 2006. Pneumatic structures in the cervical vertebrae of the Late Jurassic Tendaguru sauropods Brachiosaurus brancai and Dicraeosaurus. Eclogae geol. Helv. 99, 65-78.

In the spirit of Your neck is pathetic and Your torso is also pretty lame, I note that your sacrum is negligible:

We have here the sacrum of the Haplocanthosaurus priscus holotype CM 572, in ventral view with the ilia still in place (so that the slightly hourglass-shaped dark regions you see on either side are the acetabular regions of the ilia, facing downwards). To the right is the sacrum of a good-sized adult male human such as my good self, in dorsal view.

The total length of the five fused sacral vertebrae of Haplo is 79.5 cm (Hatcher 1903:18), compared with about 11.5 cm for the human. Actually, Haplo is not a particularly big sauropod: the sacrum of Brachiosaurus altithorax holotype FMNH P25107, for example, comes in at 95 cm (Riggs 1904:236). But it’s big enough to make your sacrum hang its zygapophyses in shame. I picked Haplo just because Hatcher’s 1903 monograph on it is so beautifully illustrated, and the world is not as plentifully supplied with complete, uncrushed, well-preserved sauropod sacra as we might wish.

This post marks Haplo’s SV-POW! debut, but what kind of sauropod is it? As pointed out by Taylor and Naish (2005:4), various studies have reached different conclusions about this: Riggs (1904:229) classified it as a brachiosaurid; McIntosh (1990:347) as a cetiosaurid; the phylogenetic analysis of Wilson and Sereno (1998:54) recovered it as a non-camarasauromorph macronarian; Upchurch (1998:74) found it to be an “eosauropod” (i.e. a non-neosauropod sauropod); Wilson (2002:240) recovered it as a basal diplodocoid (outside Diplodocimorpha, the clade uniting Diplodocus with Rebbachisaurus); and Upchurch et al. (2004:297) found it in a derived position, as a camarasauromorph closer to Titanosauriformes than to Camarasaurus.

All this disagreement is not as bad as it seems, though. We can discount Riggs’s assignment to Brachiosauridae as this was offered at a time when few sauropods were known. All the other assignments, as disparate as they appear, place Haplo very close to the root of Neosauropoda, that is the divergence between the two great Neosauropod clades Diplodocoidea and Macronaria. Some have it at the base of one branch, some at the base of the another, some just outside; with the exception of Upchurch et al.’s (2004) placement as a macronarian more derived than Camarasaurus, these positions are all only one or two nodes apart on a consensus cladogram.

In fact, the most recent common ancestor of all neosauropods might have been something rather similar to Haplocanthosaurus. It can’t have been Haplo itself, as it came along fifteen million years too late to be the ancestor of early neosauropods such as Atlasaurus, but it’s possible that it’s little changed from that ancestor.

Bibliography

• Hatcher, J.B. 1903. Osteology of Haplocanthosaurus with description of a new species, and remarks on the probable habits of the Sauropoda and the age and origin of the Atlantosaurus beds. Memoirs of the Carnegie Museum, 2, 1­-72, pls 1­4.
• McIntosh, J.S. 1990. Sauropoda. Pp. 345­-401 in D. B. Weishampel, P. Dodson and H. Osmólska (eds.). The Dinosauria. University of California Press, Berkeley.
• Riggs, E.S. 1904. Structure and relationships of opisthocoelian dinosaurs. Part II, the Brachiosauridae. Field Columbian Museum, Geological Series 2, 6, 229­-247.
• Taylor, M.P., and Darren Naish. 2005. The Phylogenetic Taxonomy of Diplodocoidea (Dinosauria: Sauropoda). PaleoBios 25 (2): 1­-7.
• Upchurch, P. 1998. The phylogenetic relationships of sauropod dinosaurs. Zoological Journal of the Linnean Society 124:43­-103.
• Upchurch, P., P.M. Barrett, and P. 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.
• Wilson, J.A. 2002. Sauropod dinosaur phylogeny: critique and cladistic analysis. Zoological Journal of the Linnean Society 136: 217-­276.
• Wilson, J.A., and P.C. Sereno. 1998. Early evolution and higher-level phylogeny of sauropod dinosaurs. Society of Vertebrate Paleontology Memoir 5:1­-68.

In a comment on the previous post, Amanda wrote:

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

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

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

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

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

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

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

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

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

Reference

• Novas, F.E., Salgado, L., Calvo, J., and Agnolin, F. 2005. Giant titanosaur (Dinosauria, Sauropoda) from the Late Cretaceous of Patagonia. Revisto del Museo Argentino de Ciencias Naturales, n.s. 7:37-41.