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A fair amount of this has been superseded with better data and prettier pictures by Schwarz et al.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.

Bifid Brachiosaurs, Batman!

These are the days of miracle and wonder, especially for all you right-minded people out there who are lovers of fine brachiosaurs.  I heard yesterday evening about a new paper in Proceedings of the Royal Society B: You and Li’s (2009, duh) description of a new brachiosaur, the first one known from the Cretaceous of Asia: Qiaowanlong kangxii. Best of all, it’s based primarily on vertebral material:

You and Li (2009:fig. 2) Cervical vertebrae of Qiaowanlong kangxii holotype FRDC GJ 07-14. (a) Photograph and (b) interpretative line drawing of C4-C7 in left lateral view; (c) a distal portion of a cervical rib; C9 in (d) cranial, (e) left lateral, (f) caudal, (g) right lateral, (h) dorsal and (i) ventral views. di, diapophysis; f1-f5, fossa 1-fossa 5; pa, parapophysis; poz, postzygapophysis; prz, prezygapophysis; sp, neural spine. Scale bars, 10 cm.

Brachiosaur aficionados will be gazing slack-jawed at parts d, f and h of this figure (the anterior, posterior and dorsal views of C9), which clearly show that the neural spines of the new taxon are bifid (i.e. have two peaks side by side and a trough between them) — just like the cervical neural spines of flagellicaudatans (diplodocids and dicraeosaurs) and camarasaurs.  And mamenchisaurs.  And some titanosaurs.  And Erketu.  Finding this feature yet again — apparently independently evolved in brachiosaurs — makes it about the most plastic character in the matrix.  Very exciting.

That is, it’s exciting if this really is a brachiosaurid.  Now as it happens, Matt was one of the reviewers for this paper (and by the way did an amazingly professional job of not telling me about it until it came out, the git).  He’s told me in email that he’s satisfied that Qiaowanlong really is a brachiosaur, and I hesitate to question that identification given that (A) unlike the authors I’ve never seen the material, and (B) unlike Matt, I’ve spent most of my brachiosaur-presacral quality time with dorsals rather than cervicals.  But, with that caveat, I’m not sure that a compelling case has yet been made for a brachiosaurian identity.

The authors cite three characters in support of a brachiosaurid identity:

• The most persuasive is the deeply excavated cervical neural spines.
• Next is a transition in neural spine height: this is quite abrupt in “Brachiosaurus” brancai between cervicals 6 and 7, and also in Sauroposeidon — presumably also between C6 and C7, but that can’t be known for sure, since it’s only the assumption that this is the case that led to the identification of the four preserved Sauroposeidon cervicals as C5-C8 in the first place.  In Qiaowanlong, this transition is “much less pronounced”, with spines increasing in height by only 25% rather then 100% in the other taxa — and occurs between C8 and C9.  All in all, not really very similar to the condition in “B.” brancai.
• The final character supporting the brachiosaurid identity of Qiaowanlong is the absence of an anterior centrodiapophyseal lamina.  As the authors point out, though, this lamina does exist in “B.” brancai and is absent only in Sauroposeidon; so if this is evidence of anything, it’s a synapomorphy of a clade uniting Qiaowanlong and Sauroposeidon to the absence of other brachiosaurs — something that seems very unlikely given the proportions of the vertebrae.

Putting it all together, there seems to be only one convincing brachiosaur character cited; and that stands against several non-brachiosaur characters, most obviously the bifurcation of the neural spine and the low Elongation Index (centrum length divided by cotyle height) but also by a few other characters that are not discussed in the paper.  For example, Matt has previously noted that in brachiosaur cervicals, the diapophyses are more anteriorly positioned than the parapophyses whereas in diplodocids the opposite is the case: as shown in fig 2(b) above, C6 at least of Qiaowanlong resembles diplodocids in this respect.

To try to get more of a handle on this, I put together a comparative figure of the 8th and 9th cervicals of various sauropods:

8th/9th cervicals vertebrae of various sauropods, scaled to the same centrum length. From top to bottom and left to right: "Brachiosaurus" brancai, Sauroposeidon; Qiaowanlong, Diplodocus; Haplocanthosaurus, Camarasaurus. Six sauropod vertebrae for the price of one!

Based on overall proportions, I don’t find it intuitively obvious that the Qiaowanlong (middle row, left) more closely resembles the brachiosaurs (top row) than it does the other three.

What does all this mean?  Probably nothing: most likely there are further reasons for the brachiosaurid identification of the new taxon, and lack of space prevented their explanation and illustration.  We can hope that the authors, having placed an initial brief description in Proc. B, will follow it up with a more comprehensive description and analysis in a journal that does not impose such tight length restrictions.  But for now at least, my feeling is that the case for a bifid brachiosaur has yet to be made.

Moving on … Qiaowanlong is also represented by some nice appendicular material: the entire right side of the pelvis (ilium, ischium and pubis).  The ilium certainly looks brachiosaury, so that is another bit of support for the systematic hypothesis, but the proportions of the pelvic bones are very odd:

Right pelvis of "Brachiosaurus" brancai (left), based on composite of Janensch's (1961) figures, and Qiaowanlong (from You and Li 2009: fig. 3a). Scaled to same ilium length.

You and Li (2009) describe their pelvis as having a “much reduced ischium”, but as is apparent by comparison with the pelvis of “Brachiosaurus” brancai, the ischium is in reasonable proportion to the ilium, and the oddity is more that the pubis is enormous.  So much so that it makes me feel a little ill looking at it, and it makes me wonder how certain it is that all three of these bones are from the same individual — sadly, the paper doesn’t discuss the association of the material.

[Not to flog a dead horse, but this kind of omission shows once more the perils of publishing new taxa in general-interest journals such as Proc. B that impose draconian length limits.  This paper just creeps onto page 7, and I simply don't believe that it's possible to do anything like justice to the description of a new taxon in that little space, especially when there is also geography, geology, phylogeny and discussion to be got through.  I don't want to go all This Is How To Do It, but I can't help remembering that Darren and I took 18 pages, nearly three times as long, to describe the single partial vertebra that is Xenoposeidon (Taylor and Naish 2007), and it's not as though that paper wastes a lot of words.  To give You and Li credit, they did squeeze in photos of a representative vertebra from all six cardinal directions, which is great; but only at the cost of the photos being too tiny to be much use.  Please, folks: send your new taxon descriptions to a proper descriptive journal, not to a tabloid!  </hobbyhorse>]

Back on the Dinosaur Mailing List, B tH asked how big Qiaowanlong was.  According to the BBC, the authors say that “the dinosaur would have been a relatively small sauropod about 12m long, 3m high, and weighing perhaps 10 tonnes”.  Can we confirm that?  Well, the excellently comprehensive table of measurements in the paper gives centrum lengths, not counting the condyle, totalling 267 cm for the seven vertebrae C5-C11.  Janensch (1950a:44) gave measurements for the corresponding vertebrae of “Brachiosaurus” brancai HMN SII totalling 577 cm, which is more than twice as long.  If Qiaowanlong was 267/577 = 0.46 times as long as HMN SII, which Janensch (1950b:102) gave as 22.46 m, then it would have been 10.4 m long; it’s not obvious how the authors got the larger figure of 12 m unless they had reason to think the neck was proportionally shorter than in HMN SII.  If Qiaowanlong was isometrically similar to HMN SII, then it was 0.46^3 = 0.99 0.099 times as heavy.  Using my own in-press mass of 23337 kg for HMN SII, this would make Qiaowanlong only 2312 kg in mass — pretty pathetic for a sauropod.

That’s it for now.  I’d be the first to admit that there’s an awful lot of speculation in this post based on relatively little published information.  Hopefully You Hai-Lu will drop by and comment — I’ll be letting him know that I’ve posted this.

References

• Janensch, Werner.  1950.  Die Wirbelsaule von Brachiosaurus brancai. Palaeontographica (Suppl. 7) 3: 27-93.
  Janensch, Werner.  1950.  Die Skelettrekonstruktion von Brachiosaurus brancai.  Palaeontographica (Suppl. 7) 3: 97-103.
  Janensch, Werner.  1961.  Die Gliedmaszen und Gliedmaszengurtel der Sauropoden der Tendaguru-Schichten.  Palaeontographica, suppl. 7 (1), teil 3, lief. 4: 177-235.
  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
  You, Hai-Lu, and Li, Da-Qing.  2009.  The first well-preserved Early Cretaceous brachiosaurid dinosaur in Asia.  Proceedings of the Royal Society B: Biological Sciences.  doi: 10.1098/rspb.2009.1278.
• Janensch, Werner.  1950.  Die Wirbelsaule von Brachiosaurus brancai. Palaeontographica (Suppl. 7) 3: 27-93.
• Janensch, Werner.  1950.  Die Skelettrekonstruktion von Brachiosaurus brancai.  Palaeontographica (Suppl. 7) 3: 97-103.
• Janensch, Werner.  1961.  Die Gliedmaszen und Gliedmaszengurtel der Sauropoden der Tendaguru-Schichten.  Palaeontographica, suppl. 7 (1), teil 3, lief. 4: 177-235.
• 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
• You, Hai-Lu, and Li, Da-Qing.  2009.  The first well-preserved Early Cretaceous brachiosaurid dinosaur in Asia.  Proceedings of the Royal Society B: Biological Sciences.  doi: 10.1098/rspb.2009.1278.

And finally … two announcements!

Traumador the Tyrannosaur has asked us to point out that over on ART Evolved (the palaeo-art blog), the next big art gallery is to be sauropod themed.  Details are on the site, so get over there and submit your sauropod art!

And Matt and I will shortly be teaming up with Andy Farke, the open-source paleontologist, on a new project where we plan to actually do some of this Shiny Digital Future that we keep on talking about.  Andy will be announcing the details on Tuesday 8th September.  Mark the date well!  For now, I shall say no more …

How tallweird was Sauroposeidon?

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)

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)

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

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)

References

• 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.

.

Little, big: the reveal

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.

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.

Speaking 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.

Neck posture, yet again: T. rex’s neck is pathetic

Here at SV-POW! Towers, we often like to play Spot The T. rex — a simple drinking game that can be played whenever you have supply of palaeontology-related news reports.  Each player in turn takes a report off the stack, and if T. rex is mentioned anywhere in the report, the player drinks.  We lay in a lot of beer when we play this game, because as it turns out, T. rex is nearly always mentioned (and nearly always spelled “T-Rex”, no italics, no full stop, gratuitous hyphen, capitalised trivial name).  For example, suppose someone publishes an innocent paper arguing that a particular Eocene clam was an obligate scavenger: then the story in the press will be “… just as has been argued for the terrifying T-Rex, which had teeth like steak knives”.  Or if someone names a new Miocene rodent, it will be introduced as “… which lived 50 million years after the terrifying T-Rex, which had teeth like steak knives”.   (Drink twice if the steak knives are mentioned.  Three times if they are described as “banana-sized”.)

So we didn’t feel our neck-posture paper was real until it had somehow been tied in with T-Rex.  Happily, the Great North Museum came to the rescue: by coincidence, they unveiled their T. rex cast the weekend before the paper came out, and the Sunday Sun wanted our opinion on the way the neck had been mounted.  Here’s their mount (not quite ready to exhibit):

Tyrannosaurus rex mounted skeleton at the Great North Museum. From journallive.co.uk

Of course, everything we said about the necks of sauropods in the paper also applies to every other extinct land vertebrate — we only concentrated on sauropods because (A) they are the group whose neck posture has been claimed to depart from the tetrapod norm, and (B) they are cool.  In particular, non-avian theropods such as T. rex are in the same extant phylogenetic bracket as sauropods are (i.e. birds plus crocs), so we’d expect strong extension at the base of the neck and strong flexion at the head joint in habitual pose.

So I replied that “the Newcastle mount has the neck and torso in more of a straight line [than a Vidal-compliant posture], which would probably not have been the habitual pose.  It looks to me as though this animal is crouching down to take a drink”, and I’m pleased that the resulting news story included a rather gracious response from the GNM curator.

I don’t know whether the notoriously litigious Disney corporation would be so mellow, though, regarding their truly horrible mount of a cast of “Sue”:

Tyrannosaurus rex "Sue" cast, at Animal Kingdom, Walt Disney World, Florida. From wwarby's Flickr photostream.

I’m really not sure what the people who mounted this were getting at: unlike the Great North Museum mount, the legs are erect, so it’s not going into or coming out of a crouch; and it’s not going into a drinking posture, because the head is pointing straight forward.  But for some reason, it’s below shoulder height.

Here’s how it should be done:

Tyrannosaurus rex at the American Museum of Natural History. Photo by Mike Taylor

It’s good to see that the biggest natural history musuem in the world is ahead of the curve, and has its T. rex mount in a pose consistent with how other land vertebrates habitually hold their necks.

I leave you with the news the T. rex’s neck is pathetic.  Here is the skull and neck of that same AMNH mount, composited with a single cervical vertebra (C8) of Sauroposeidon.  Please note that the Sauroposeidon cervical is way longer than the whole T. rex neck.

T. rex's neck is pathetic

No references today!

[You don't need to be told the reference for Taylor et al. (2009) again, do you?]

OMG: MPT, PHD!

If you woke up this morning and thought, “Global warming is on the rise, amphibians are in a race to see who can go extinct first, the economy is in the toilet, any day now my boss will discover that I don’t actually do anything at work,  and my blog will never have the eclectic cachet of SV-POW!, but at least Mike Taylor doesn’t have a Ph.D.,” then it is my happy duty to ruin your day. Mike defended today, successfully.

Ladies and gentlemen, I proudly present Michael P. Taylor of Ruardean, Englishman, adventurer, raconteur, Doctor of Philosophy in the paleontological arts. Note that when recumbent he is approximately equal in length to 1.5 Sauroposeidon cervicals, and appears to be cradling an invisible wine glass. Don’t stare too long, or you might not be able to look away.

Congratulations, sir! Let the blogosphere ring with the happy news, and undescribed sauropods cry out for recognition.

Update (from Mike)

Thanks to Matt, and all commenters, for your kind words.  I wondered when the “Latin love god” photo was going to appear, and that day has finally come.  What Matt doesn’t know is that this photo was used for the cover of my forthcoming album:

Available wherever good music is sold

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.

SV-POW! showdown: stegosaurs vs sauropods

New hotness out today: Miragaia, a new long-necked stegosaur from the Late Jurassic of Portugal (Mateus et al. 2009). What is “long-necked” for a stegosaur? In this case, well over a meter! That may not sound too impressive for those of you who have gotten complacent about 10-meter-plus sauropod necks, but it’s a big deal. Miragaia is described as a sauropod mimic, and with good reason: its body proportions are not that different than those of a basal sauropod.

The number of ways to increase the proportional length of the neck are limited: you can add cervicals, or recruit dorsals into the neck, or make the individual vertebrae longer, or do some combination of  the above. In sauropods, different clades took different routes. Brachiosaurids kept a fairly primitive cervical count of  13 but made the individual vertebrae crazy long. Diplodocids recruited dorsals into the neck, and some (like Barosaurus and Supersaurus) also made the vertebrae crazy long. Mamenchisaurids and Euhelopus added cervicals (independently), up to a total of 17 or more, and some (like Omeisaurus)–are you ready for it?–also made the vertebrae crazy long.

In general, stegosaurs took an evolutionary walk through Door Number 2: turning dorsals into cervicals. Mateus et al. (2009) show this nicely in a table; the number of presacrals (cervicals plus dorsals) in stegosaurs stays about the same, between 25 and 27, but between the basal Huayangosaurus and the derived Stegosaurus 3 or 4 dorsals go forward to play for the other team. Is dorsal recruitment sufficient to explain the long neck of Miragaia? Hard to say, since the dorsal series has not been found. But Miragaia’s count of 17 cervicals is significantly more than Stegosaurus’s 13. If Miragaia didn’t add any cervicals but only recruited dorsals, it would have had only 9 of the latter. That’s not impossible–Barosaurus did that very thing–but it’s weird, and extreme. As Mateus et al. (2009:p. 4) state, “Miragaia possessed more cervical vertebrae than any other non-avian archosaur, except the Chinese sauropods Mamenchisaurus, Omeisaurus and Euhelopus, also with 17″. And yet the individual vertebrae are pretty short, no longer than in your not-exactly-average Stegosaurus.

I couldn’t resist pitting Miragaia, the longest-necked stegosaur (so far!) against Brachytrachelopan, the shortest-necked sauropod (so far!). Miragaia is stolen from Mateus et al. (2009:fig. 1a), and Brachytrachelopan from Rauhut et al. (2005:fig. 1a). Both critters come with the 1 meter scale bars from their respective figures. I’m in there for scale, too, at 6′2″ or 1.88 meters. Sauroposeidon looms in the background, just to keep things in perspective. The entire neck of Miragaia might have been about as long as one of the middle cervicals of Sauroposeidon or Supersaurus.

Still, you know.

Not bad.

(for a stinkin’ ornithischian)

A couple more pictures here.

References

• Mateus, O., Maidment, S.C.R., and Christiansen, N.A. 2009. A new long-necked ’sauropod mimic’ stegosaur and the evolution of the plated dinosaurs. Proceedings of the Royal Society of London, Series B. (doi:10.1098/rspb.2008.1909)
• Rauhut, O. W. M., Remes, K., Fechner, R., Cladera, G. & Puerta, P. 2005. Discovery of a short-necked sauropod dinosaur from the Late Jurassic period of Patagonia. Nature 435:670–672. (doi:10.1038/nature03623)

The ghost of Christmas past

But also of Christmas future.

Or, perhaps, the spirit (pneuma) of the season.

Merry Christmas to all! We’ll see you back here in 2009.

Cheers,

The SV-POW!sketeers

There’s almost nothing but nothing there, Sauroposeidon edition

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

Image and caption recycled from fig. 14 here.

Addendum (from Mike)

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

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

Special bonus weirdness

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