Well, not really really.

charlie-appendicular-480px

Appendicular skeleton of savannah monitor lizard Varanus exanthematicus, "Charlie", in dorsal view.

What we have here is of course the bones of all four feet of a lizard (plus the limb bones): “sauropod” means “lizard foot”, so lizard-foot skeletons are sauropod skeletons — right?

(Note that the hind limbs are arranged in a weird posture here, with the knees bent forward.  Also that the left pes is missing one digit — possibly IV — which was presumably lost some time ago and healed.)

These are the bones of “Charlie”, a mature savannah monitor lizard Varanus exanthematicus, estimated as fourteen or fifteen years old at the time of death.  I have his whole skeleton — cranial, axial and limb-girdles — in various states of preparation, and no doubt they will all appear here sooner or later.  I was fortunate enough to encounter Charlie in the reptile house of a local kids’ activity centre with the boys, and he was not in a good way.  Luckily, his keepers happened to come in as I was looking at him, we got talking, and I popped the question as tactfully as I could — would it be OK to take his body away when the sad day comes?

The sad day came, and I found a message on my answering machine.  For one reason and another, it was a couple of days before I was able to drive out and pick up his mortal remains, but it was a proud day when I brought him home:

Charlie in his glory

Savannah monitor lizard Varanus exanthematicus, "Charlie", recently expired, in left dorsolateral view. Scale bar for, uh, scale.

Charlie was a good-sized beast: 111 cm in length from snout to tail, and massing 3.4 kg.  I tell you, it was quite a challenge getting him into that pot that you see top right.

Charlie with Jonno

Savannah monitor lizard Varanus exanthematicus, "Charlie", recently expired, in right anterodorsolateral view. Juvenile Homo sapiens "Jonno Taylor" for scale.

To prepare Charlie for the pan, I had to remove his tail — much, much harder than I’d been prepared for, as it was so difficult to locate the sacrocaudal intervertebral joint — and gut him.  Unfortunately, by the time I opened him up, internal decomposition had set in, and he was not in a pleasant state:

charlie-opened-up-480px

Savannah monitor lizard Varanus exanthematicus, "Charlie", recently expired, in the unpopular right posteroventrolateral view.

(I have much more disgusting photos than this one, but it wouldn’t be tasteful to show them.)  Anyway, I abandoned my initial plan of dissecting the organs out, and basically just removed and discarded them.  I’ve actually had shamefully little experience with dead animals, so I don’t know how much the horrible state of Charlie’s guts is due to his final illness and how much to post-mortem decomposition.

Once I’d managed — just — to get him into the pot, Charlie was lightly simmered for a couple of hours (to Fiona’s delight), then dismembered, and the individual parts reboiled before I started picking the bones out of the various parts.  There’s more to say, but that will have to wait for another time.

Was this just a half-lame attempt to fulfill our titular mandate whilst plugging my new astronomy blog? Of course it was (and I just did it again!). Doesn’t mean you lot are off the hook for figuring out what it is. So here’s another image with more views. You have a week. Don’t let me down.

Oh, and to sweeten the pot, 351 SV-POW!bucks to the person who first figures it out.

UPDATE: Too late, suckers! In a stunning move, Phil Mannion won the contest basically right out of the gate. The vertebra is indeed a cervical of Paluxysaurus (image below from Rose, 2007). Good job, Phil!

Well, now you’re hosed–the contest is over and you’re not due for another post for nearly a week. What to do, what to do? Assuming that you’re all caught up on your Tet Zoo reading, you might want to check out Save Your Breath For Running Ponies. It’s not just a paleo blog, but it has a lot of paleo in it, including lots of smack talk to whatever critter has been in the news lately. For example, see the recent post, “It’s not all mindless sex with beautiful women, placoderm”. This makes SYBFRP sort of the FU, Penguin of paleo.

OR you could discuss the question I posed in the comments: why does “this anterior cervical of Paluxysaurus look so much like Euhelopus, DGM Serie B, etc. The posterior cervicals look like Sauroposeidon, not exactly the same, but lots of similarities. The juxtaposition blew my mind ten years ago, and it still does. Your thoughts are welcome.” They still are.

Still not telling you

We really should have covered this ages ago …  Here we are, blithering on about brachiosaurids and diplodocoids and all, and we’ve never really spelled out what these terms mean.  Sorry!

The family tree of a group of animals (or plants, or fungi, or what have you) is called its phylogeny.  The science of figuring out a phylogeny is called systematics.  And once you’ve got a phylogeny, the business of naming the parts of it (and of course choosing which parts to name) is taxonomy.

For a long time, sauropod systematics was completely up in the air, so that McIntosh’s (1990) review article on sauropods in The Dinosauria (first edition) said, rather despairingly, that “although recent discoveries are beginning to clarify the problems of sauropod phylogeny, were are still very far from being able to construct a cladogram” (p. 399).  Happily, this changed rapidly thereafter, with the first published numerical phylogenetic analysis appearing in Russell and Zheng’s (1993) description of the new Mamenchisaurus species M. sinocanadorum.  More importantly, in the same year Paul Upchurch submitted his (1993, duh) dissertation on sauropods, and this contained a much larger analysis which was subsequently published as Upchurch (1995).  This paper raised the bar significantly, with an analysis of 27 taxa using 174 characters.  Three years later, Upchurch (1998) published a major revision of his own work; in the same year, the other major school of sauropod phylogeny launched with a JVP memoir (Wilson and Sereno 1998), which featured only 10 taxa and 109 characters, but discussed and illustrated them in more detail.  Wilson (2002) followed this up with a much larger analysis of 27 taxa and 234 characters, and Upchurch et al. (2004), in the second editi0n of The Dinosauria, saw his 27×234 and raised him to 41×309.  The good news is that, by this time, the two schools’ phylogenies, having started out rather different, were converging on a consensus topology with only two significant disagreements, which we’ll come to in a minute.

Since then, Jerry Harris (2006) created a union matrix from the character scores in the Wilson (2002) and Upchurch et al. (2004) matrices, and also threw in a few additional characters from other less ambitious phylogenetic analyses.  This analysis came up with a tree that was very similar to Wilson’s, and subsequent work by Wilson and Upchurch (2009) indicates that Upchurch is now also substantially in agreement with this arrangement.

So here it is!

Consensus phylogeny of sauropod, from Harris (2006)

Consensus phylogeny of sauropod, from Harris (2006)

I plucked this from Jerry’s paper, and coloured it in to show two of the more important groups.  Evolution begins at bottom left, so let’s quickly tour the group.

  • First of all, note the outgroups. Sauropods’ nearest relatives are the other saurischian dinosaurs, theropods and prosauropods.  (They’re shown the wrong way round here, because in an unrooted tree it makes no difference.  Ignore that.)
  • The most basal sauropods include things like Vulcanodon and, it turns out mostly from the work of Adam Yates (e.g. Yates 2007), a whole bunch of things that, if you looked at them you’d probably guess were prosauropods.
  • Sauropods as we know them really begin at the boundary of the group Eusauropoda (“true sauropods”), which is roughly speaking everything more derived than Vulcanodon.  (I won’t discuss the naming of nodes and branches in detail in this post, as it would quickly get too long.  Maybe in a later tutorial.)  This group I have coloured pink in the diagram above.
  • Basal eusauropods include quite a few genera, and the order in which they branched off the “main line” leading to the neosauropods is not clear — as the unresolved polytomy above shows.  Cetiosaurus (which for some reason is not shown in this figure) is generally considered quite derived; some of the Chinese sauropods (Mamenchisaurus, Omeisaurus, etc.) may form a group of their own, but that’s not clear.
  • Most of the best-known sauropods fall within the great group Neosauropoda (“new sauropods”), which is coloured purple above.  A few genera float around the root of this group, including Haplocanthosaurus and Jobaria, both of which are sometimes considered neosauropods, and sometimes non-neosauropod sauropods (or what I informally call “eosauropods”, or “dawn sauropods”).
  • Otherwise the great split within Neosauropoda is between the diplodocoids (on the left) and the macronarians (on the right) — the groups including Diplodocus on one hand, and Saltasaurus on the other.
  • The most basal diplodocoids are the rebbachisaurids over on the left.
  • Most other diplodocoids fall into the group Flagellicaudata (“whip-tails”), which is itself composed of dicraeosaurids and diplocodids.  (It’s not clear where in that dichotomy, or maybe just outside it, Suuwassea falls.)
  • Over in the other half of the Neosauropods, the first macronarians to diverge are the camarasaurids (which currently means, uh, Camarasaurus).
  • Most of the other macronarians fall into Titanosauriformes, the group uniting brachiosaurids (yay!) with titanosaurs and their buddies.  Everything closer to titanosaurs falls within Somphospondyli, and that includes Euhelopus — as it turns out.  (Upchurch had found Euhelopus to fall outside Neosauropoda).
  • Once you get past Euhelopus, you’re into Titanosauria (though there are various definitions which place the entry point differently).
  • And once inside Titanosauria … well, all bets are off at this stage.  There is a rough consensus that things like Malawisaurus and Andesaurus are pretty basal and Saltasaurus is, sort of by definition, derived.  But apart from that, different studies have come up with wildly different phylogenies, with that of Curry Rogers (2005) being particularly left-field.

Without a doubt, Titanosauria is where the action is right now.  As alluded to in the comments of Matt’s Isisaurus post, it’s a big, big group, encompassing many genera and huge morphological range.  It’s also a long-lived group, spanning the whole of the Cretaceous; and it’s where most new genera are being named, as Argentina seems to be packed full of ‘em.

Well, that’s all for now.  Sorry it’s been wordier than usual — probably not much fun to read, but hopefully useful to refer back to in future.

Here’s the famous 8th cervical vertebra of the “Brachiosaurusbrancai lectotype HMN SII, this time in a left-lateral close-up of its left prezygpapophyseal ramus, showing the many pneumatic excavations.  Enjoy!

"Brachiosaurus" brancai lectotype HMN SII, 8th cervical vertebra, left prezygapophyseal ramus in left lateral view.

"Brachiosaurus" brancai lectotype HMN SII, 8th cervical vertebra, left prezygapophyseal ramus in left lateral view.

References

Curry Rogers (2005)
Harris (2006)
McIntosh (1990)
Russell and Zheng (1993)
Upchurch (1993)
Upchurch (1995)
Upchurch (1998)
Upchurch et al. (2004)
Wilson (2002)
Wilson and Sereno (1998)
Wilson and Upchurch (2009)
Yates (2007)
  • Curry Rogers, Kristina. 2005. The Evolutionary History of the Titanosauria. pp. 50-103 in: K. Curry Rogers and J. A. Wilson (eds.), The Sauropods: Evolution and Paleobiology. University of California Press, Berkeley.
  • Harris, Jerald D. 2006. The significance of Suuwassea emiliae (Dinosauria: Sauropoda) for flagellicaudatan intrarelationships and evolution. Journal of Systematic Palaeontology 4: 185-198.
  • McIntosh, John S. 1990. Sauropoda. pp. 345-401 in: D. B. Weishampel, P. Dodson and H. Osmólska (eds.), The Dinosauria, 1st edition. University of California Press, Berkeley and Los Angeles.
  • Russell, Dale A., and Zheng, Zhong. 1993. A large mamenchisaurid from the Junggar Basin, Xinjiang, China. Canadian Journal of Earth Science 30(10/11): 2082-2095.
  • Upchurch, Paul. 1993. The Anatomy, Phylogeny and Systematics of the Sauropod Dinosaurs. University of Cambridge, unpublished Ph.D. dissertation. 489 pp.
  • 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, 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.
  • Wilson, Jeffrey A. 2002. Sauropod dinosaur phylogeny: critique and cladistic analysis. Zoological Journal of the Linnean Society 136: 217-276.
  • Wilson, J. A. and Paul C. Sereno. 1998. Early evolution and Higher-level phylogeny of sauropod dinosaurs. Society of Vertebrate Paleontology, Memoir 5: 1-68.
  • Wilson, Jeffrey A. and Paul Upchurch. 2009. Redescription and reassessment of the phylogenetic affinities of Euhelopus zdanskyi (Dinosauria – Sauropoda) from the Early Cretaceous of China. Journal of Systematic Palaeontology 7: 199-239. doi:10.1017/S1477201908002691
  • Yates, Adam M. 2007. The first complete skull of the Triassic dinosaur Melanorosaurus Haughton (Sauropodomorpha: Anchisauria). pp. 9-55 in: Paul M. Barrett and David J. Batten (eds.), Special Papers in Palaeontology 77: Evolution and Palaeobiology of Early Sauropodomorph Dinosaurs. The Palaeontological Association, U.K.
Mare Imbrium from my driveway, Feb. 3, 2009

Mare Imbrium from my driveway, Feb. 3, 2009

I’ve been interested in astronomy my whole life, but I only got serious about it in the past two years. In the internet age, “getting serious” about something usually means “starting a blog”, so I did. My aim is to show people that enjoying the night sky doesn’t have to be time-consuming or expensive. Stop by if you’re interested.

Here’s your token sauropod vert. What do you reckon it might be?

Not telling you

Back in 1999 or 2000 Jaime Headden sent me his skeletal reconstruction of what was then known as Titanosaurus colberti (Jain and Bandyopadhyay 1997), but which has recently been renamed Isisaurus colberti by Upchurch and Wilson (2004). Jaime’s skeletal reconstruction and life restoration are here. Somebody threw a skin over the recon to produce this life restoration.

As you can see, the sauropod as reconstructed by Jaime is weird as heck.

I tried my own, and it came out quite a bit differently, but also weird as heck. I have to give a lot of the credit to Jaime; my recon is basically his, traced, with some of the elements scaled differently.

isisaurus-colberti-circa-2000-480DO NOT assume that this is accurate. IIRC, Jaime scaled the elements in his recon using the scale bars in the figures from Jain and Bandyopadhyay (1997), and I scaled mine using the measurements given in the text. As you can see if you compare to the two recons, those sources of data do not agree (hmm…where have we seen this problem before?). Also, the whole skeleton of Isisaurus is not known so a lot of what you see here is guesswork. Finally, I drew this on a spare afternoon almost a decade ago, and I haven’t ever done a single thing with it that would give me any real-world feedback to tell me just how screwed up it is. Looking at it now, the limb bones look awfully long for those girdles, the anterior caudals don’t look very much like the anterior caudals of anything, and…yeah. I could barely muster the courage to post it. But I am posting it, partly because it is an artifact of my own intellectual ontogeny, partly to spark discussion, and partly to highlight the following problem:

We’ve got two weird and conflicting reconstructions, based on two conflicting sets of measurements from the same paper!

So what now? I’ve always intended to update this. I would make a start by scanning all of the elements from Jain and Bandyopadhyay (1997) and saving them as separate layers in Photoshop or GIMP. Then each element can be rescaled at will. And I’d build a background grid to hopefully help keep the scaling honest, like I did with my Brachiosaurus and Sauroposeidon skeletal recons. And I’d probably try plugging the Isisaurus elements into Mark Hallett’s Rapetosaurus skeletal reconstruction; back when Jaime and I were working on our drawings no one had ever found a reasonably complete titanosaur so we were both working a bit in the dark.

All that would possibly make for better versions of these drawings, but the fundamental difference is in the measurements, and those aren’t going to change until someone measures the skeleton again to check whether the scale bars or the published measurements are accurate. My guess is that the published measurements are accurate, or at least a lot more accurate than the scale bars. Scale bars are notoriously difficult to get right, but it is hard to creatively misuse a tape measure. Still, for now, we just don’t know.

We know that Isisaurus must have been pretty darn weird because its cervicals are so short. I tend to spend most of my time thinking about critters like Sauroposeidon and Erketu and Mamenchisaurus youngi, in which the cervical centra can be six times as long as tall or even longer. Isisaurus went the opposite direction–its cervical centra are only about twice as long as tall, right down the column. The only other sauropods with such short cervicals are dicraeosaurids such as Brachytrachelopan. Given the other examples of homoplasy between diplodocoids and titanosaurs, I wonder if Isisaurus and Brachytrachelopan were ecological analogues, and I wonder what they were up to.

References

In an email, Vladimir Socha drew my attention to the fact that Tom Holtz’s dinosaur encyclopaedia estimates the maximum height of Sauroposeidon as 20 meters plus, and asked whether that was really possible.  Here’s what Tom actually wrote: “Sauroposeidon was one of the largest of all dinosaurs.  At perhaps 98 to 107 feet (30 to 32.5 meters) long and weighing 70 to 80 tons [...] Sauroposeidon would have been the tallest of all dinosaurs. [...] If it could crane its neck up, it might have been able to hold its head 66 to 69 feet (20 to 21 meters) high or more” (Holtz and Rey 2007:207).  Vladimir was understandably skeptical.  But can it be true?

Wedel and Cifelli (2005: fig. 15) shows Matt’s best skeletal reconstruction of Sauroposeidon, with Boring Old Brachiosaurus and a human for scale:

Sauroposeidon with Boring Old Brachiosaurus and human for scale and 20 m height indicated. Lightly modified from Wedel and Cifelli (2005: fig. 15)

Sauroposeidon with Boring Old Brachiosaurus and human for scale and 20 m height indicated. Lightly modified from Wedel and Cifelli (2005: fig. 15)

Amazingly, those dummies didn’t include an actual scalebar; but apparently the human figure is 1.8 m tall, so by measuring pixels and cross-scaling, I determined that in this image, Sauroposeidon is a mere 13.43 m tall.  I took the liberty of adding in a marker for the 20 m height proposed by Holtz, and as things stand you’d have to say that it doesn’t look probable.

But let’s see what we can do.  We’ll begin with the classic brachiosaur skeleton of Paul (1988), which shows the well represented species Brachioaurus brancai:

Brachiosaurus brancai skeletal reconstruction in left lateral view. From Paul (1988:fig. 1)

Brachiosaurus brancai skeletal reconstruction in left lateral view. From Paul (1988:fig. 1)

(Some other time, we should take a moment to discuss the differences between this and the Wedel brachiosaur reconstruction; but it will not be this day.)

This reconstruction is in a nice erect-necked posture which, in light of our own recent paper, is probably not too extreme.  Since all the neural arches and processes are missing from the only known posterior cervicals of this species, we don’t know how much flexibility they allowed, and so in light of how the rest of the animal is built (high shoulders and all) it seems reasonable to allow a lot of extension at the base of the neck.  So let’s assume that the pose offered by Paul is correct.  By measuring my scan of that figure, and I see that the 2.13 m humerus is 306 pixels long.  The entire reconstruction, from tip of cranial crest down to forefoot, is 1999 pixels tall, which is 1999/306 = 6.53 times as long as the humerus, which scales to 6.53*2.13 = 13.91 m — a little taller than Sauroposeidon (not Brachiosaurus) in Matt’s reconstruction, which seems about right if we imgine Matt’s Brachiosaurus raising its neck into a Paul-compliant posture.

Now Paul’s reconstruction is based on the Berlin mounted skeleton HMN S II.  Cervical 8 is very well preserved in that animal, and has a centrum length of 98 cm (Janensch 1950a:44).  By contrast, the centrum of C8 of Sauroposeidon OMNH 53062 (the only known specimen) is 125 cm long (Wedel et al. 2000a: 110). So if Sauroposeidon is merely an elongated Brachiosaurus brancai, then it’s 125/98 = 1.28 times as long and tall, which would be 17.74 m.

But wait: it seems that Sauroposeidon is to Brachiosaurus brancai as Barosaurus is to Diplodocus — similar overall but more elongate.  And it turns out that Barosaurus has at least 16, maybe 17 cervicals (McIntosh 2005:45) compared with Diplodocus‘s 15.  So maybe Sauroposeidon also added cervicals from the brachiosaur base-state — in fact, that would hardly be surprising given that Brachiosaurus brancai has so few cervicals for a long-neck: 13, compared with 15 in most diplodocids, 16 or 17 in Barosaurus, and 19 in Mamenchisaurus.  If you reconstruct Sauroposeidon with two more C8-like cervicals in the middle of the neck, that adds 2*125 = 250 cm, which would give us a total height of 17.74+2.5 = 20.24 m.

So I don’t think Tom Holtz’s estimate is completely unrealistic, even for the one Sauroposeidon specimen we have now — and remember that the chances of that individual being the biggest that species got are vanishingly small.

On the other hand, maybe Sauropodseidon‘s neck was the only part of it that was elongated in comparison to Brachiosaurus brancai — maybe its forelimbs were no longer than those of its cousin, so that only the neck elongation contributed to greater height.  And maybe it had no additional cervicals, so its neck was “only” 1.28 times as long as that of Brachiosaurus brancai — 1.28*8.5 = 10.88 m, which is 2.38 m longer; so the total height would be 13.91+2.38 = 16.29 m (assuming the additional neck length was vertical).  And maybe the neck couldn’t get very close to vertical, so that the true height was lower still.

All of this just goes to show the perils of reconstructing an animal based only on a sequence of four cervicals.  (Reconstructing on the basis of a single partial mid-to-posterior dorsal, on the other hand, is a much more exact science.)

Finally: Matt’s reconstruction of Sauroposeidon is really rather conservative, and looks very much like a scaled-up vanilla brachiosaur.  Just to see how it looks, I’ve made a reconstruction of the putative (and very possible) elongated, attenuated version of Sauroposeidon, showing the legs and cervicals 28% longer than in B. brancai, and with two additional cervicals.  I made this by subjecting Greg Paul’s 1988 brachiosaur to all sorts of horrible and half-arsed distortions, so apologies to Greg.  But remember, folks: this is just as likely correct as Matt’s version!

A different view of Sauroposeidon, based on elongation of the cervicals and legs of Brachiosaurus brancai and the insertion of two additional cervicals. Heavily and carelessly modified from Paul (1988: fig. 1)

A different view of Sauroposeidon, based on elongation of the cervicals and legs of Brachiosaurus brancai and the insertion of two additional cervicals. Heavily and carelessly modified from Paul (1988: fig. 1)

References

.

Little, big: the reveal

August 2, 2009

WNV-1

Here’s the answer to last week’s riddle. The big vertebra was obviously cervical 8 of Sauroposeidon, which you’ve seen here more than once. The small vertebra is also a mid-cervical, also from the Early Cretaceous, but from Croatia rather than Oklahoma. The very long centrum, unbifurcated neural spine, and extensive pneumatic sculpturing mark it as a brachiosaurid. It was first described by Dalla Vecchia (1998), and lavishly illustrated with numerous photos by Dalla Vecchia (1999). It was also included by Dalla Vecchia (2005:figs. 18.5 and 18.6) in the Thunder-Lizards volume from Indiana University Press, which is where I figured someone might recognize it from.

WNV-1 in hand 480

Here are two of those figures from Dalla Vecchia (1999)–note the thumb and fingers in the left-hand photo. The vertebra is about a foot long (~30 cm), which means it is TINY for a brachiosaurid mid-cervical. Note also that there is no sign of a neurocentral suture, so the critter was probably at least half grown and might have been full grown.

It is worth bearing mind that this super-tiny, pathetically titchy, adorable widdle bwachiosauw ve’tebwa is only a bit smaller than your average giraffe cervical.

Sauroposeidon vs WNV-1 480Speaking of giraffes, from left to right we have:

  • Sauroposeidon, scaled like HM SII x 1.15;
  • a 20-foot-tall world record giraffe;
  • WNV-1, scaled like 0.22 x Sauroposeidon;
  • a 6’2″ human, such as yours truly.

Note that I  could look over the shoulder of WNV-1, but it could not look over the giraffe’s shoulder, nor could the giraffe look over Sauroposeidon‘s shoulder. The giraffe could not walk under Sauroposeidon‘s stomach, but WNV-1 could walk under the giraffe’s.  If the mass of Sauroposeidon was 40 tons, that of WNV-1 may have been around 450 kg, or a little under half a ton.

I wonder which evolved first in brachiosaurids, stupendous size or stupendous necks?

References

  • Dalla Vecchia, F.M. 1998. Remains of Sauropoda (Reptilia, Saurischia) in the Lower Cretaceous (Upper Hauterivian/Lower Barremian) limestones of SW Istria (Croatia). Geologia Croatica 51(2):105-134.
  • Dalla Vecchia, F.M. 1999. Atlas of the sauropod bones from the Upper Hauterivian – Lower Barremian of Bale/Valle (SW Istria, Croatia). Natura Nacosta 18:6-41.
  • Dalla Vecchia, F.M. 2005. Between Gondwana and Laurasia: Cretaceous sauropods in an intraoceanic carbonate platform; pp. 395-429 in Tidwell, V., and Carpenter, K. (eds.), Thunder-Lizards: The Sauropodomorph Dinosaurs. Indiana University Press, Bloomington.
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