tallweird was Sauroposeidon?
August 7, 2009
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:
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:
(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!
- Holtz, Thomas R., Jr., and Luis Rey. 2007. Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages. Random House, New York. 428 pages.
- Janensch, Werenr. 1950. Die Wirbelsaule von Brachiosaurus brancai. Palaeontographica (Suppl. 7) 3: 27-93.
- McIntosh, John S. 2005. The Genus Barosaurus Marsh (Sauropoda, Diplodocidae). pp. 38-77 in Virginia Tidwell and Ken Carpenter (eds.), Thunder Lizards: the Sauropodomorph Dinosaurs. Indiana University Press, Bloomington, Indiana. 495 pages.
- Paul, Gregory 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.
- Wedel, Mathew J., and Richard L. Cifelli. 2005. Sauroposeidon: Oklahoma’s Native Giant. Oklahoma Geology Notes 65 (2): 40-57.
- Wedel, Mathew J., Richard L. Cifelli and R. Kent Sanders. 2000a. Sauroposeidon proteles, a new sauropod from the Early Cretaceous of Oklahoma. Journal of Vertebrate Paleontology 20(1): 109-114.
- Wedel, Mathew J., Richard L. Cifelli and R. Kent Sanders. 2000b. Osteology, paleobiology, and relationships of the sauropod dinosaur Sauroposeidon. Acta Palaeontologica Polonica 45(4): 343-388.