Grilling your Thanksgiving dinosaur: live-blogging the bird

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

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

Enough of that. Let’s rock!

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

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

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

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

Into the fridge for a day.

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

The bird awaits.

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

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

A chimney is helpful to get the coals going.

To eat is human; to grill is divine.

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

Fruit and spices into the body cavity.

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

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

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

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

UPDATE

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

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

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

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

And hello-o science!

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

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

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

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

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

More out than in

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

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

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

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

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

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

References

• Gilmore, C.W.  1936.  Osteology of Apatosaurus with special reference to specimens in the Carnegie Museum. Memoirs of the Carnegie Museum 11: 175-300.
• Lovelace, D.M., Hartman, S.A., and Wahl, W.R. 2007. Morphology of a specimen of Supersaurus (Dinosauria, Sauropoda) from the Morrison Formation of Wyoming, and a re-evaluation of diplodocid phylogeny. Arquivos do Museu Nacional, Rio de Janeiro 65(4):527-544.
• Schwarz, D., Frey, E., and Meyer, C.A. 2007. Pneumaticity and soft−tissue reconstructions in the neck of diplodocid and dicraeosaurid sauropods. Acta Palaeontologica Polonica 52 (1): 167–188.
• Wedel, M.J., and Sanders, R.K. 2002. Osteological correlates of cervical musculature in Aves and Sauropoda (Dinosauria: Saurischia), with comments on the cervical ribs of Apatosaurus. PaleoBios 22(3):1-6.

Postscript

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

Small African primate possibly sheds light on soft-tissue morphology of Cretaceous diplodocoid

One of the most bizarre of sauropods – and arguably one of the most bizarre of dinosaurs – is the Patagonian dicraeosaurid diplodocoid Amargasaurus cazaui Salgado & Bonaparte, 1991. Here’s a picture of a replica specimen, provided by Nizar Ibrahim. You’ll note that this skeleton has been posed with an extended cranio-cervical junction, and a slightly extended cervico-dorsal junction: virtually the opposite of what you’d expect in ‘normal’ posture (Taylor et al. 2009).

Thanks to its appearance in virtually every post-1991 book on dinosaurs, Amargasaurus is a relatively familiar animal these days, which is sort of a shame: we’ve somehow forgotten how frikkin’ weird it is. We’ve looked at Amargasaurus on SV-POW! before: in this article we drew attention to the fact that its dorsals are pretty interesting too, and as usual with sauropods we could write whole essays on all manner of its vertebral osteology. Perhaps, in time, we will.

However, let’s be honest and note that it’s those ridiculous cervical spines that keep us awake at night. What the hell did the animal do with these structures, and exactly what did it look like when alive? Early reconstructions (most notably Brian Franczak’s drawing from 1992 (see Hecht 1992)) all went with the idea of two paired sails, running in parallel along the length of the neck. All artists thereafter followed suit. Until 1994, when Greg Paul noted that the circular cross-sections of the spines and tapering tips might suggest that the paired neural spines instead protruded from the neck as horn-covered spikes (Paul 1994). Greg also suggested that having paired sails along the neck might be a really bad idea as it could restrict neck mobility, but this idea never made much sense as the tissue between the spines would presumably be flexible and hence not such a problem (the circular cross-section is not really a problem either, since other animals that are thought to have had skin sails, like Dimetrodon, also have rounded neural spines). Since 1994 few opinions have been expressed on this subject, but those that have have sided with Greg in noting that spines are more likely than sails (Salgado 1999).

At SVP Bristol last month, your favourite blog authors spent many happy hours discussing sauropods and their vertebrae. And, inevitably, the subject of Amargasaurus and its weird cervical spines came up. Fact is, sails AND spines are both equally stupid, and the idea of independent neck spines is particularly stupid because animals just don’t ever have their neural spines poking out beyond the musculature and skin of the neck. Right?

Wrong. Hardly known and rarely mentioned is that the last four (or so) cervical neural spines and first three thoracic spines of the Potto Perodicticus potto (a peculiar African strepsirrhine primate, closely related to the Asian lorises) protrude from the skin of the neck and shoulders, have sharply pointed tips, and are usually stated to serve a defensive function [potto skeleton above provided by Mo Hassan]. The spines don’t protrude as naked bone (though this was claimed by Ivan Sanderson), but are covered with skin and some hair, and form a series of tubercles in the live animal. When threatened, a potto is supposed to hide its head and point those protruding neck spines towards the danger, sometimes even butting the predator or aggressor with the spines. Other functions have been suggested for the spines, but a defensive function remains most popular and in the absence of any special knowledge I’ll go with the majority.

At left, Potto with flexed neck, showing its cervical and thoracic spines. From Walker (1970). At right, Amargasaurus as reconstructed by Salgado (1999). Salgado imagined this to be the animal's normal posture: an idea that we find somewhat unlikely (see Taylor et al. 2009).

You might wonder, quite reasonably, whether the anatomy of a small arboreal modern primate has any bearing whatsoever on the soft-tissue morphology of a Cretaceous sauropod (even a ‘small’ one). The point is, however, that neural spines can protrude from the neck after all (albeit sheathed in skin and other tissue), and hence there is at least some precedent for this sort of thing. All that’s needed now is for someone to study the histology and microscopic surface texture of those protruding potto spines and see if there are any correlates for their protruding nature (so far as I can tell this hasn’t been done). Then go look at Amargasaurus. There’s clearly a paper in this, please report back and include me on the authorship, thanks.

References

• Hecht, J. 1992. Dollars for dinosaurs. New Scientist 136 (1845), 50.
• Paul, G. S. 1994. Dinosaur art & restoration notes: dicraeosaurs. The Dinosaur Report Summer 1994, 8.
• Salgado, L. 1999. The macroevolution of the Diplodocimorpha (Dinosauria; Sauropoda): a developmental model. Ameghiniana 36, 203-216.
• Taylor, M. P., Wedel, M. J. & Naish, D. 2009. Head and neck posture in sauropod dinosaurs inferred from extant animals. Acta Palaeontologica Polonica 54, 213-220.
• Walker, A. 1970. Nuchal adaptations in Perodicticus potto. Primates 11, 135-144.

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.

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

This is corn on the cob:

Corn on the cob, in cross section. Stolen from http://www.istockphoto.com/file_thumbview_approve/214165/2/istockphoto_214165-co rn-cob-cross-section.jpg

This is a shish kebab:

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

Most tetrapods are like shish kebabs: a whole lot of meat stuck on a proportionally tiny skeleton.  If you don’t believe me, you can look at the human and cow neck torso cross-sections in Matt’s last post, or check out this ostrich-neck cross-section from his 2003 Paleobiology paper:

Ostrich neck in cross section, CT scan. From Wedel (2003a: fig. 2)

Remember that this is a freakin’ ostrich — of all extant animals, one of the ones with a most extreme long, skinny neck.  And yet, if sauropods were muscled like ostriches, then their necks would have looked like this in cross section:

Putative shish kebab-style sauropod neck in cross section. Ostrich soft-tissue from Wedel (2003a: fig. 2), Diplodocus vertebra cross-section from Paul (1997: fig. 4) scaled to match size of ostrich vertebra

And soft-tissue reconstructions would have to look like this:

Diplodocus with its neck as fat as an ostrich's. Modified from Paul (1998: fig. 1F)

Which, happily, no-one is suggesting.  Instead, published reconstructions of sauropod neck soft-tissue are startlingly emaciated.  As exhibit A, I call this pair of Greg Paul cross-sections:

Diplodocus and Brachiosaurus neck cross-sections, showing very light musculature. From Paul (1997: fig. 4)

(Yes, the Diplodocus on the left is the one I used in the photoshopped ostrich cross-section above.  It’s instructive to compare Paul’s original with the What If It Was Like A Big Ostrich version.)

Paul’s reconstructions seem to be widely considered too lightly muscled.  But even the very careful and rigorous more recent reconstructions of Daniela Schwarz and her colleague show a neck much, much thinner than that of the ostrich:

Diplodocus neck cross-sections. From Schwarz et al. (2007: fig. 7a)

Although Schwarz has put a lot more soft tissue onto the neck vertebrae than Paul did, it is still a tiny proportion of what we see in extant animals — even the ostrich, remember, which has a super-thin neck compared with pretty much anything else alive today.  If sauropod necks were muscled as heavily as those of, say, cows, then the soft tissue would pretty much reach down to the ground.  But they weren’t: they were more like corn on the cob, with a broad core of skeleton and relatively little in the way of delicious edibles festooned about it.

So why is this?  Why does everyone agree that sauropod necks were much less heavily muscled than those of any extant animal?

It’s a simple matter of scaling.  A really big ostrich might have a neck 1 m long.  (Actually, ostriches don’t get that big, but let’s pretend they do because it makes the maths easier).  If the x meter-long neck of a sauropod was just a scaled-up ostrich neck, then it would be x times longer, x times taller and x times wider, for a total of x^3 times as voluminous and therefore x^3 times as heavy.  But the cross-sectional area of the tension members that support it is only x times taller and x times wider, for a total of x^2 times the strength.  In total, then, the neck’s mass/strength is x^3/x^2 = x times as great as in the ostrich.  (The sauropod neck’s mass also acts further out from the fulcrum by an additional factor of x, but that is cancelled by the fact that the tension in the neck also acts x times higher above the fulcrum.)

It seems intuitively obvious (which is is code for “I have no way to prove”) that you can’t reasonably expect the neck muscles of a giant ostrich to work ten times as hard as they do in their lesser cousins, which is what you’d need to do for the 10 m neck of, say, Sauroposeidon.  So simple isometric scaling won’t get the job done, and you need to restructure the neck.

But how?  Surely just reducing all the muscle around the vertebrae can’t help?  No indeed — but that is not really what sauropods were doing.  If you look at the typical sauropod-neck life restoration, you’ll see that the proportional thickness of the neck is actually not too dissimilar to that of an ostrich — rather thicker, in fact.  If you scaled an ostrich neck up to sauropod size and compared it with a real sauropod neck, you would find not that the soft tissue was too fat, but that the vertebrae were too thin.

And so we come to it at last: rather than thinking of sauropods as having reduced the amount of soft-tissue hanging on the cervical vertebrae, we do better to think of them as having kept a roughly similar soft-tissue profile to that of an an ostrich, but enlarging the vertebrae within the soft-tissue envelope.  Of course if you just blindly made the vertebrae taller and wider, they would become heavier in proportion, which would defeat the whole purpose of the exercise — but as everyone who reads this blog surely knows by now, sauropod cervicals were extensively lightened by pneumaticity.  By bringing air into the center of the neck, they were effectively able to displace bone, muscle and ligament away from the centre, so that they acted with greater mechanical advantage: higher epaxial tension members, lower hypaxial compression members, and more laterally positioned paraxials.

It’s a rather brilliant system — using the same volume of bone to achieve greater strength by displacing it outwards and filling the center with air (and, in doing so, also displacing soft tissue outwards).  And it will be hauntingly familiar to anyone who loves birds, because it is of course exactly what birds (and pterosaurus) have done in their long bones: the hollow humeri of flying vertebrates famously allow them to attain greater strength — specifically, resistance to bending — for the same volume and mass of bone.  It’s a neat trick when done with long bones, but it takes a truly awesome taxon to do it with the neck.

So maybe sauropods were not corn on the cob after all.  Maybe they were Hostess Twinkies.

Hostess Twinkie. Not truly pneumatic, as the internal cavity is filled with adipose tissue rather than air, but do you have any idea how difficult it is to find good images of hollow junk food? Stolen from http://dixiedining.files.wordpress.com/2008/07/twinkie_070918_ms1.jpg

And now for something completely different

Now that I’ve finished my Ph.D at the University of Portsmouth, what am I going to do with the rest of my scientific life?  I’ve always said that I have no intention of going into palaeo full time: my knowledge is far too narrow for that, so that even if paid jobs were not in insanely short supply, I wouldn’t stand much chance of getting one.  And in any case, I’d hate to get into the all-too-common situation of being up against a friend for a position we both wanted. Throw in the fact that I really enjoy my computer-programming day-job and it seems pretty clear that what I need is an unpaid affiliation that lets me get on with lovely research.

Well: I am absolutely delighted to announce that, as of last month, I am an Honorary Research Associate in the Department of Earth Sciences at UCL.  It’s not just that UCL is such a well-respected institution — see that Wikipedia article for some details — more importantly, it’s where Paul Upchurch hangs out, as Senior Lecturer in Palaeobiology.  Sauropod fans will be familiar with Paul’s characteristically detailed and careful work, from his pioneering work on sauropod phylogeny (Upchurch 1995, 1998), through his and John Martin’s indispensible Cetiosaurus makeovers (Upchurch and Martin 2002, 2003) to the state-of-the art review that he lead-authored for Dinosauria II (Upchurch et al. 2004) and the Tokyo Apatosaurus monograph (Upchurch et al. 2005).  What many of you won’t know is what an excellent collaborator he is — quick, conscientious, insightful and diplomatic.  We’ve already collaborated on a few short papers (Upchurch et al. 2009 and a couple of Phylocode companion-volume chapters that are in press), and I hope there will be more in the future.

References

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

What heads tell us about necks, redux

I Cannot Brain Today, I Have the Dumb

Man, I hate making mistakes. The only thing worse than making mistakes is making them in public, and the only thing worse than that is finding them in published papers when it’s too late to do anything about them. About the only consolation left–if you’re lucky–is getting to be the one to rat yourself out (we have to do this a lot). So here goes.

Neck angle FAIL

In our figure 4 (from Taylor et al. 2009) we showed the skulls of three sauropodomorphs, Massospondylus, Camarasaurus, and Diplodocus, posed with horizontal semicircular canals (HSCCs) level, angled 30 degrees above horizontal, and angled 20 degrees below horizontal, as it is written (by Duijm 1951). We also showed the angle of the occipital condyle when the HSCCs are level; if the craniocervical joint was in osteologically neutral pose (ONP), that line would indicate the angle of the anterior cervicals.

Trouble is, we put the neck lines for Diplodocus and Camarasaurus in the wrong places.

As any idiot can see from Sereno et al. (2008: fig 1), the brain, brainstem, and occipital condyle form a line that runs from roughly the upper part of the orbit (in lateral see-through view) out the back of the head. Now if you look at our fig. 4 you’ll see that the ONP lines for Camarasaurus and Diplodocus are much too inclined, so that if the brain was in line with the anterior neck–which it should be, in ONP–it would be sticking out the back of the head.

If that doesn’t make sense, just look at the above illustration, imagine the brain and spinal cord in a straight line parallel to the black neck line but also dorsal to it, and you’ll see that the brain would be outside the skull. Those incorrect neck lines don’t represent impossible postures, but they don’t represent ONP, either.

Taxonomic variation WIN!

Here’s a corrected up version of the figure to show what I mean. The black lines are still the ONP neck lines, and now I’ve put in shadowy necks at +30 and -20 to go with the shadowy heads. The 50 degree spans marked out by the shadowy necks are the ranges within which the neck could articulate in ONP with skulls stuck in the 50-degree “Duijm window”.

Caution: it is very easy to misread the shadowy necks as showing a range of movement within an individual; in fact, the neck lines are ‘anchored’ to the skulls in ONP as the skulls rotate through the 50 degrees allowed by the HSCCs. They are not individual movement but the possible range of taxonomic variation in HSCC orientation according to Duijm (1951).

Worth noting here is the likelihood that Massospondylus had a more elevated neck than any of the neosauropods studied so far–certainly a finding at odds with the traditional depictions of basal sauropodomorphs. (It is just a likelihood, though, since the top, neck-wise, of Massospondylus’s Duijm window overlaps with the windows of the other taxa a bit.)

Nigersaurus, buddy, why so down?

In this version I’ve gone one step farther and included Nigersaurus (modified from Sereno et al. (2008: fig 1). Nigersaurus differs from Diplodocus in the angle of the face from the HSCCs and occipital condyle, not in the angle between the HSCCs and the occipital condyle, which is remarkably similar in Camarasaurus, Diplodocus, and Nigersaurus. This suggests that Nigersaurus held its head differently than other sauropods, but not necessarily its neck.

Keep in mind, though, that the difference in facial angle between Diplodocus and Nigersaurus is less than 50 degrees, and that some of the head postures in the respective Duijm windows of the two taxa are identical. So we can’t say for certain that Nigersaurus held its head differently than Diplodocus; it is possible that they held their heads at the same angle and that Nigersaurus just carried its HSCCs at a different angle. If that were the case, the neck of Nigersaurus would have been more inclined than that of Diplodocus. I’m not arguing that that’s likely–it seems perfectly plausible that the two taxa might have held their necks similarly and their heads differently, as suggested above–I’m just pointing out the very wide range of possibilities allowed by the data. To reiterate one of the points of the paper, HSCCs aren’t useless for determining habitual head posture, they just can’t narrow things down very far on their own.

Also note that some of the neck postures allowed by the Duijm window have the anterior cervicals running down, below horizontal, not up. And many of the allowed neck postures for the neosauropods are close to horizontal. So, we were wrong and HSCCs + occipital condyles show that most sauropods held their necks close to level and not strongly elevated after all, right?

Onward and Upward, or Down in Flames?

Not so fast. Remember that all of the neck lines in the above figures show the angle of the anterior neck if the neck was in ONP with the skull. But Vidal et al. (1986) found that the skull is habitually flexed on the neck, even in lizards, and we have since verified this for salamanders, turtles, and more. And sometimes the flexion is dramatic.

Our figure 1 (from Taylor et al. 2009) shows the cranium, cervicals, and first few dorsals from a hare in ONP and in the posture shown by Vidal et al. (1986: fig. 4b). The difference between the anteriorly-directed ONP pose and the backward-leaning Vidal-compliant pose is striking. I measured the angle between the cervical column and the maxillary toothrow to be ~110 degrees in the ONP pose and ~70 degrees in the Vidal-compliant pose (try it yourself with Paint or Photoshop, or download some free image manipulation software). That means the head is flexed on the neck by 40 degrees! That is a big angle. If sauropods did the same, you could take the neck lines shown above and crank them down by 40 degrees (remember that the heads are “fixed” into the 50-degree Duijm windows allowed by the HSCCs), which would make Mike’s elevated Diplodocus look not just achievable, but perhaps even conservative.

Where does all that leave us? In sauropods for which HSCC orientation is known, putting the HSCCs level the anterior neck is still inclined, and even with the HSCCs angled 20 degrees down the ONP neck would only be slightly below horizontal, and if the head was Vidal-compliant (strongly flexed on the neck), the neck would have to be above horizontal. So heads still tell us about necks, and in particular they tell us that the necks angled up. Our neck lines for Camarasaurus and Diplodocus are not correct for ONP, but probably represent attainable postures. My first head ‘n necks post has the angles too exaggeraged for ONP, too, but again all of those poses are not just possible but likely if the head was flexed on the neck.

Miscellanea

We owe mad props to Brian Engh, a.k.a. The Historian, who burst on the paleo-rap scene with a rap video about crocodilian predation and almost certainly the first ever kung-fu rap video to name-check titanosaurs. Brian stumbled across Mike’s extra goodies page for the new paper about week before the paper was due out, and kindly suppressed the information until after D-Day. You can and should download his entire album, Earth Beasts Awaken (open access, yo), and kick it old school.

Congratulations to Francisco “Paco” Gasco, who just got funding for a PhD to do a complete morphological and paleobiological workup on the giant Spanish sauropod Turiasaurus. You’ll be hearing more about Paco in the not-too-distant future, we promise.

Finally, here’s that video of an elephant grabbing an ostrich by the neck that you ordered.

The End of the Beginning?

This brings us to the end of ten solid days of new posts, which is a new record for us and one not likely to be broken for a long time, if ever. We never planned to do all this; in the beginning we each were going to contribute one post and that would have been that. But we kept finding things that we felt needed to be discussed.

As all of us have been saying in every available medium, this is not the end of anything. The sauropod neck posture debate is not over; in a few years we may look back and see that in 2009 we were still stumbling to the real starting line. We don’t think this stuff is unimportant or unknowable, and we’re going to keep working on it, and we hope lots of others do as well.

We’ll see you out there.

Up, boy, up! Heyaaah!!

References

• Duijm, M. 1951. On the head posture in birds and its relation to some anatomical features. II. Proceedings of the Koninklijke Nederlandse Akademie van Wetenschappen, Series C 54: 260–271.
• Sereno, Paul C., Jeffrey A. Wilson, Lawrence M. Witmer, John A. Whitlock, Abdoulaye Maga, Oumarou Ide and Timothy A. Rowe.  2007. Structural Extremes in a Cretaceous Dinosaur. PLoS ONE 2 (11): e1230 (9 pages).  doi:10.1371/journal.pone.0001230
• Taylor, M.P., Wedel, M.J., and Naish, D. 2009. Head and neck posture in sauropod dinosaurs inferred from extant animals. Acta Palaeontologica Polonica 54 (2): 213–220.

Necks, the big picture: because there are other animals besides sauropods

In case you haven’t heard, Taylor et al. (2009) recently argued that sauropods naturally held their cervico-dorsal junctions in extension, and their cranio-cervical joints in flexion… at least, when they weren’t foraging, feeding or engaged in other such activities [if you need help with those terms please see the Tet Zoo article here].

Given that we here at SV-POW! are predominantly interested in sauropods, and given that the amazing necks of these animals have long been such a source of debate, it stands to reason that sauropods might get used as the ‘poster children’ or exemplars for any particular argument about neck pose in fossil tetrapods. However, as we’ve said here and there – I certainly mentioned it in my Tet Zoo article on the subject – the contention (that cervico-dorsal junctions are maintained in extension, and that cranio-cervical joints are maintained in flexion) holds true for all terrestrial amniotes and, to a degree, all crown-group tetrapods. In this article we’re going to do something a little odd for SV-POW! – we’re going to look at other fossil amniotes to see if and how this affects them. Have any of them also been reconstructed in poses that are not compliant with the data from living animals?

The short answer is yes, yes they have.

First off, fossil mammals mostly get by ok, which is what you’d expect given that they are generally very similar to their extant relatives. Likewise, there aren’t any fossil birds that have been reconstructed incorrectly, and again you’d hope not given that they’re generally highly similar to extant forms. The extinct moa from New Zealand (that’s moa in the plural sense) are sometimes shown standing at rest with non-extended cervico-dorsal junctions, but with extremely strong extension in the anterior part of the neck that makes up for this (Worthy & Holdaway 2002). While extension at the cervico-dorsal junction may be subtle or absent in living ratites when they are feeding or foraging, in relaxed individuals extension at the neck base is indeed present.

Stegosaurs really need a makeover

What about other dinosaurs? Here’s where we do find quite a few reconstructions that contradict our contention. For a start, basal sauropodomorphs – the animals conventionally lumped together as prosauropods – have often been shown with non-extended cervico-dorsal junctions and fully extended cranio-cervical junctions: that is, with necks that emerge in a straight line from the body, and heads that have their long axis parallel to that of the neck. Classic examples include Kermack’s reconstruction of the animal formerly known as Thecodontosaurus and Weishampel & Westphal’s Plateosaurus. There are many others.

Historically, non-avian theropods have been depicted with elevated necks, flexed cranio-cervical junctions and all that. So far so good. One specific exception does come to mind however: Tarsitano (1983) produced a truly awful theropod reconstruction in which the neck was shown as straight and with a non-extended cervico-dorsal junction. The latter is a no-no, and so is straightening the neck this much, as the shapes of the centra and neural arches show that the cervical vertebrae of theropods were held elevated and in a gentle S-curve (see Molnar & Farlow 1990). A few artistic reconstructions of non-avian theropods have given them non-elevated necks (Neave Parker’s megalosaur picture from the 1970s comes to mind), and if you look at the allosaurs that featured in Walking With Dinosaurs you’ll note that their cranio-cervical junctions are extended, not flexed as they should be.

Theropod posture as reconstructed by Tarsitano (1983). Tarsitano mostly argued that non-avian theropods were more like crocodilians than birds in musculature and some aspects of posture.

On to ornithischians. It was difficult to keep a tight lip back in February 2009 when the long-necked stegosaur Miragaia longicollum was published. Like the WWD diplodocoids, Miragaia was given a non-extended cervico-dorsal junction and extended cranio-cervical junction: in other words, its neck and head were illustrated projecting forwards in a straight line, as a continuation of the animal’s dorsal column (Mateus et al. 2009). Based on what we know about living animals, it’s more likely that the cervico-dorsal junction was extended, and that the cranio-cervical junction was flexed: in other words, that the neck was strongly elevated relative to the dorsal vertebrae, and that the head was held at an angle to the neck. Given the remarkable length of its neck, this at least makes it possible that Miragaia was a high-browser. I look forward to seeing artistic reconstructions that show this animal with its head held up above its back, rather than extending forwards and parallel to it (actually, I’ve already seen two, but you know what I mean).

In fact, like sauropods, stegosaurs have been flat out abused by palaeontologists, with non-extended cervico-dorsal junctions and fully extended cranio-cervical junctions being the norm across more than 100 years of description and reconstruction. And don’t use the excuse that these reconstructions are all meant to show the animals engaged in feeding or foraging: they’re not. Many of them clearly depict the animals standing, in relaxed poses, and doing nothing. Marsh started it in 1891: he showed the skull of Stegosaurus armatus (then S. stenops) fully extended, rather than flexed, on the neck, and showed the neck continuing in (approximately) a straight line from the dorsals. This reconstruction was hugely influential, of course, and even today the popular conception of the stegosaur – with its horrible over-arched back and down-sloping tail – is based on Marsh’s drawing. Later stegosaur reconstructions by Lull and Gilmore perpetuated the idea of non-extended cervico-dorsal junctions and fully extended cranio-cervical junctions in Stegosaurus (see Czerkas 1987 for a review of stegosaur life reconstructions), and the same posture was later reconstructed for Huayangosaurus, Kentrosaurus, Tuojiangosaurus and others (see Galton & Upchurch 2004).

Tuojiangosaurus, as displayed in the Natural History Museum, London. (c) NHM (image from wikipedia). Note the lack of extension at the cervico-dorsal junction and the slight hyper-extension at the cranio-cervical junction.

Those stegosaur reconstructions you can see in some museums – some of which show the cranio-cervical junction in slight hyper-extension (look at the Tuojiangosaurus shown here) – are flat-out horrible and totally contradict the data we have from neck and head posture in extant amniotes (Taylor et al. 2009). In recent decades, reconstructions by artists like Stephan Czerkas and Greg Paul have given stegosaurs raised necks where the cervico-dorsal junction is extended in proper fashion (as per the data from living amniotes). I get the impression, however, that such reconstructions have not been taken seriously by ‘mainstream’ palaeontologists, at least some of whom still seem to think that stegosaurs walked around with their heads two inches off the ground.

Similar mistakes have been made with ankylosaurs: most classic reconstructions show non-extended cervico-dorsal junctions where the neck emerges in a straight line or even slopes downwards, and cranio-cervical junctions that are in full extension. This goes for Ken Carpenter’s Euoplocephalus [shown in composite above] and Sauropelta, Richard Lull’s Nodosaurus, and others (Lull 1921, Carpenter 1982, 1984). Again, the reconstructions that show these neck and head postures do not definitely show the animals in feeding, foraging or searching postures: they are meant to depict the ‘normal’ (viz, relaxed) pose for the animal. A gently elevated neck with an extended cervico-dorsal junction and a flexed cranio-cervical junction is, again, what we should expect given what living animals do, and this has been correctly portrayed by some.

Other ornithischians have generally been reconstructed accurately (at least as goes neck and head posture), but there are, however, a few ceratopsian reconstructions showing non-extended cervico-dorsal junctions and fully extended cranio-cervical junctions. Granger & Gregory (1923) reconstructed Protoceratops in this manner, for example, and ceratopsids have sometimes been shown this way too (Lull 1933). Again, the reconstructions I’m referring to are meant to show normal, relaxed poses, rather than feeding or foraging poses, so criticism is justified. Putting extension into the ceratopsian cervico-dorsal junction raises the head somewhat, such that the top of the frill is now higher than the top of the back rather than lower than it. Notably, some articulated skeletons are displayed this way: the Centrosaurus panel-mount AMNH 5351, shown here, is one of the best examples. Lull thought that the neck had been elevated too much and that the neck posture ‘is that of death rather than that of life’! Peter Galton’s Hypsilophodon (which has mostly been superseded by Greg Paul’s reconstruction these days anyway) should also be considered suspect in view of the strongly extended cranio-cervical junction (Galton 1971, 1974), but the animal was clearly meant to be running at speed, so you could argue that it was shown holding its head and neck in a decidedly un-relaxed pose.

The excellent Centrosaurus specimen AMNH 5351. Photo borrowed from Traumador the Tyrannosaur. Thanks, Traumador :)

I should point out again at this point that our contention (that cervico-dorsal junctions should be shown in extension in a relaxed animal, and cranio-cervical junctions should be shown in flexion in a relaxed animal) is a hypothesis. It’s possible (unlikely perhaps, but possible) that some stegosaurs, or ankylosaurs, or therapsids, or whatever, did some funky stuff with their occipital condyles or vertebrae and evolved a relaxed head and neck posture different from that of living amniotes, and indeed (as we’ll see in a moment) there surely are at least some exceptions within Amniota. However, if you think a given animal represents a special case, you’re gonna have to demonstrate it.

Shock horror, marine reptiles on SV-POW!

Elsewhere among Reptilia, the data from living lizards and crocodilians indicates that, generally speaking, we should expect fossil forms to hold their necks elevated at moderate angles of between 20-40° relative to the dorsal column when in normal, relaxed pose. Many fossil, non-dinosaurian archosaurs (like rauisuchians and aetosaurs) have been reconstructed this way (mostly because people have looked at living crocodilians when reconstructing these animals), as have fossil squamates and many others.

A very old reconstruction of the Jurassic plesiosaur Plesiosaurus.

We do, however, have a contradiction of sorts when we come to sauropterygians (the plesiosaurs and their relatives). Reconstructions of plesiosaurs have evolved in similar fashion to those depicting sauropods: some old reconstructions (some, not all) depict them with extended cervico-dorsal junctions and flexed cranio-cervical junctions (such reconstructions typically show the animals sticking their necks well up out of the water and peering around) (e.g., Williston 1914), but many others show them with non-extended cervico-dorsal junctions and fully extended cranio-cervical junctions. In other words, with the neck and head continuing in a straight line from the dorsal column.

The elasmosaurid Thalassomedon haningtoni, as displayed at the Denver Museum of Nature and Science. Check out the big neural spines.

Contradicting the idea that plesiosaurs looked down on their prey from above is the fact that their orbits often face slightly or strongly upwards, and there are also indications from their narial and ear anatomy that they were specialised for detecting sensory cues in water, not in air (Cruickshank et al. 1991, Storrs & Taylor 1996). Furthermore, their high-density, often pachyostotic skeletons indicate that they were negatively buoyant animals that were trying their hardest to stay submerged and beneath the surface. All of this indicates that plesiosaurs were subaqueous predators that mostly kept their necks and heads beneath the surface of the water (except when breathing). This makes it very unlikely that their necks were elevated, and indeed – in strong contrast to sauropods and other dinosaurs – there are indications from their vertebral anatomy that neck elevation was not possible in the group (in elasmosaurs, for example, the neural spines on both the cervicals and dorsals are tall and sub-rectangular and it’s difficult to imagine how this would have allowed anything more than extremely subtle extension at the cervico-dorsal junction). So I am going to go out on a limb here (or, more accurately, I’m going to agree with everyone who works on plesiosaurs) and say that plesiosaurs did not hold their necks in the same manner as the extant amniotes that we looked at (Taylor et al. 2009). Is this because they were aquatic, and hence not under the same gravitational constraints as terrestrial amniotes? That looks likely, but we really need to thrash this out once and for all: further work on this is obviously needed, and perhaps it will appear soon. I know from many discussions that plesiosaur researchers talk as much about long necks as sauropod researchers do.

Finally – dicynodonts and other synapsids

Moving now well away from dinosaurs and archosaurs and even reptiles, I’ve had non-mammalian synapsids on my mind an awful lot during all of this. While many of them have relatively short necks, members of some groups have still been shown in downright unlikely postures. Dinocephalians have consistently been shown (correctly) with extended cervico-dorsal junctions and flexed cranio-cervical junctions, so those reconstructions of such things as Titanophoneus and Moschops with their necks held high and their heads at an angle are correct based on the data from living amniotes. However, some reconstructions of some caseids (Stovall’s Cotylorhynchus), dicynodonts (I’m looking at you, Watson’s rendition of Lystrosaurus [shown at top of composite image used above] and Cluver’s Cistecephalus) and gorgonopsids (Colbert’s Lycaenops, for example; shown below) have the cranio-cervical junction in extended or even hyper-extended pose, which again is a total no-no unless there is evidence to the contrary. While some of these animals have been reconstructed in walking or running poses (and hence might be holding their necks and heads in special searching or foraging poses), plenty of others are shown standing on all fours, in relaxed, ‘normal’ poses, so their unusual neck and head poses are, we can assume, meant to be the relaxed, ‘normal’ poses (further examples include King’s Dicynodon and Dinodontosaurus).

The relatively short necks of these animals mean that, even with the cervico-dorsal junction in full extension, the neck is only elevated by a slight and thoroughly believable 20-40° relative to the dorsal column. Similarly, showing the cranio-cervical junction in flexion is no big deal, as all it does is rotate the skull such that its long axis is at an angle to the neck, rather than acting as a straight-line continuation of it. It seems that more extreme cervico-dorsal extension and cranio-cervical flexion evolved within Mammalia, and hence that non-mammalian synapsids were more like other ‘average’ amniotes in head and neck posture. Nevertheless – again – reconstructions that show the neck and head as straight-line extensions of the back should be considered inconsistent with what we know of neck and neck posture in living amniotes.

Final thoughts

We really hope that our paper will inspire some much-needed debate, and instigate some new work. As you’ll know if you’ve been following the comments on blogs and such, and the media coverage we’ve been getting, there’s every indication that this is exactly what will happen. But what makes this work of particular interest to people in general – and not just to specialists who spend their time worrying about cervical rib morphology and its correlation with functional morphology, or whether the bifurcate neural spines of some sauropods are homologous with the single neural spines of others, and so on – is that it has a real and obvious effect on the life appearance of a fossil animal. And, as I’ve tried to show here, our hypothesis extends beyond the limits of Sauropoda. Stegosaurs and dicynodonts need never look the same way again.

References

• Carpenter, K. 1982. Skeletal and dermal armor reconstruction of Euoplocephalus tutus (Ornithischia: Ankylosauridae) from the Late Cretaceous Oldman Formation of Alberta. Canadian Journal of Earth Sciences 19, 689-697.
• Carpenter, K. 1984. Skeletal reconstruction and life restoration of Sauropelta (Ankylosauria: Nodosauridae) from the Cretaceous of North America. Canadian Journal of Earth Sciences 21, 1491-1498.
• Cruickshank, A. R. I., Small, P. G. & Taylor, M. A. 1991. Dorsal nostrils and hydrodynamically driven underwater olfaction in plesiosaurs. Nature 352, 62-64.
• Czerkas, S. A. 1987. A reevaluation of the plate arrangement on Stegosaurus stenops. In Czerkas, S. J. & Olson, E. C. (eds) Dinosaurs Past and Present, Volume II. Natural History Museum of Los Angeles County/University of Washington Press (Seattle and Washington), pp. 82-99.
• Galton, P. M. 1971. Hypsilophodon, the cursorial non-arboreal dinosaur. Nature 231, 159-161.
• Galton, P. M. 1974. The ornithischian dinosaur Hypsilophodon from the Wealden of the Isle of Wight. Bulletin of the British Museum (Natural History) 25, 1-152.
• Galton, P. M. & Upchurch, P. 2004. Stegosauria. In Weishampel, D. B., Dodson, P. & Osmólska, H. (eds) The Dinosauria, Second Edition. University of California Press (Berkeley), pp. 343-362.
• Granger, W. & Gregory, W. K. 1923. Protoceratops andrewsi, a pre-ceratopsian dinosaur from Mongolia. American Museum Novitates 72, 1-9.
• Lull, R. S. 1921. The Cretaceous armored dinosaur, Nodosaurus textilis Marsh. American Journal of Science 1, 97-126.
• Lull, R. S. 1933. A revision of the Ceratopsia or horned dinosaurs. Memoirs of the Peabody Museum of Natural History 3, 1-175.
• Mateus, O., Maidment, S. C. R. & 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)
• Molnar, R. E & Farlow, J. O. 1992. Carnosaur paleobiology. In Weishampel, D. B., Dodson, P. & Osmólska, H. (eds) The Dinosauria. University of California Press (Berkeley), pp. 210-224.
• Storrs, G. W. & Taylor, M. A. 1996. Cranial anatomy of a new plesiosaur genus from the lowermost Lias (Rhaetian/Hettangian) of Street, Somerset, England. Journal of Vertebrate Paleontology 16, 403-420.
• Tarsitano, S. F. 1983. Stance and gait in theropod dinosaurs. Acta Palaeontologica Polonica 28, 251-264.
• Taylor, M. P., Wedel, M. J. & Naish, D. 2009. Head and neck posture in sauropod dinosaurs inferred from extant animals. Acta Palaeontologica Polonica 54, 213-220.
• Williston, S. W. 1914. Water Reptiles of the Past and Present. University of Chicago Press, Chicago.
• Worthy, T. H., Holdaway, R. N. 2002. The Lost World of the Moa. Indiana University Press, Bloomington, Indiana.

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?]

Unstated precision and undemonstrated accuracy: two more reasons why we don’t trust DinoMorph

Because the appearance of accuracy has an irresistible allure, non-specialists frequently treat these estimates as factual.

–Graur and Martin (2004: p.80)

Prologue: Why We Hatin’?

Between the first DinoMorph post and this one, it may seem like we have it in for DinoMorph, like we’re trying to discredit the method or bury it. We’re not anti-DinoMorph at all. We really want it to work, because 3D modeling is probably going to be the only way to explore some problems we care about  (like the breathing mechanics of an articulated sauropod torso), and so far DinoMorph seems to be farther along than any of the alternatives. It is also worth remembering that building 3D digital dinos for scientific purposes is still in its infancy, and that the VP community has barely gotten started exploring the possibilities. The field has great promise. But we also have to be realistic about limitations in the source data (see Mike’s post) and about the accuracy and precision of the results (this post). We hope that these posts will start constructive conversations and inspire more work to improve the science.

Intro: Accuracy and Precision

Accuracy is how close to the real value a measurement is, and precision is how close repeated measurements are to each other. Say it’s 100 degrees F outside, which it may be for some of you. If you have four thermometers and they read 90, 95, 105, and 110, then the mean is 100. The accuracy of the aggregate setup is high, but the precision is low (big error bars). If, on the other hand, your thermometers read 94.2, 93.8, 94.6, and 93.4, then they are precise (tight grouping) but inaccurate (not centered on the real value)

Oh Error Bars, Where Art Thou?

Here’s what 2 degrees (angular, not temperature) looks like:

It’s not a big measurement. If I was measuring the range of movement (ROM) of a single joint in one individual, like an elbow or shoulder, and I got a precision of plus or minus 2 degrees over repeated movements, I’d be pretty happy. If I got that level of precision on, say, the left knee, in ten different people, I’d start worrying that I was in the Matrix.

All eusauropods have at least 12 cervical vertebrae, and diplodocids have at least 15 (Barosaurus probably has 16, but there are no complete necks so it’s hard to be sure). What happens if we propagate an error of plus or minus 2 degrees down the neck of Diplodocus?

None of these are supposed to correspond to any particular pose in life. I just lined up all the cervicals as straight as I could get them, and then rotated each joint between C3 and C15 by 2 degrees. I left the occipital condyle and C1-C3 in a straight line because I felt the point was made, but the head could be rotated up or down by another 6 degrees if one so chose. Again, this is not an ROM, this is just an error of plus or minus 2 degrees across each of 12 intervertebral joints.

Now let’s look back at the neutral pose and estimated ROM of the neck in the CM 84/94 composite skeleton of Diplodocus (Stevens 2002: fig. 6a):

Notice that the model poses are shown with perfect precision, and no allowance for error. Now, look back up at the first picture to get an idea of what 2 degrees of error looks like, and then try to mentally apply it to each of those three poses. It’s not easy to picture, but in my mind’s eye the three neck poses dissolve into a fuzz of probabilities, like the electron cloud around the nucleus of an atom.

How precise is DinoMorph? Or rather, given that the guts of the program probably allow for Jupiter flyby levels of precision, how precise is any given result, based on the interaction of raw data, necessary but unverified controlling assumptions (see below), and the algorithm itself? Can we really rule out an error of plus or minus 2 degrees per joint? What about 1 degree per joint? What about 5? This is a problem of precision, and it would still exist even with an absolutely perfect neck that was 100% complete and entirely undistorted (which we ain’t got).

It’s possible that the current version of the program doesn’t allow these kinds of error calculations. That’s fine–I realize that DinoMorph, like all of science, is a work in progress. But I’d like to know up front that there is no provision for determining the precision, so I could delay asking the question. And at some point, it will have to be answered.

Maybe it would be better to shift gears and ask: when DinoMorph is applied to extant animals, does it accurately predict the neutral pose and ROM?

Ground Truthiness

It might be better to ask that question, but there are no published answers. From the first DinoMorph paper, where the method is justified (Stevens and Parrish 1999: p. 798):

Our manipulation of muscle and ligament preparations of extant bird necks indicated that synovial capsules constrain movement such that paired pre- and postzygapophyses could only be displaced to the point where the margin of one facet reaches roughly the midpoint of the other facet, at which point the capsule is stretched taut (20). In other words, one facet could slip upon the other until their overlap was reduced to about 50%. In vivo, muscles, ligaments, and fascia may have further limited movement (20); thus, the digital manipulations reported here represent a “best case” scenario for neck mobility.

The reference supporting all this is number 20 (remember how much I like numbered references?), and here’s the full text (Stevens and Parrish 1999: p. 800):

20. J. M. Parrish and K. Stevens, unpublished data.

Those data are still unpublished. But at least one of the basic assumptions–the 50% zyg overlap bit–is contradicted by Stevens and Parrish (2005b: p. 191 [not to mention by Taylor et al. 2009]).

It’s been a decade. There have been three subsequent papers on this stuff (Stevens 2002, Stevens and Parrish 2005a, b). The DinoMorph results have been the foundation for sauropod depictions in the biggest dinosaur documentary ever made and for an exhibit at the biggest natural history museum in the world. And we have no idea if the method is accurate, because the supporting data have never been published.

Sadly, this is not that uncommon in paleontology, particularly when it comes to sauropods, and especially when it comes to necks. Someone comes up with a totally new method, and right out of the gate it gets applied to a thorny paleontological problem, before it’s been demonstrated to work on extant animals. It’s exciting, it’s seductive, and it’s hard to screw up, because when you apply an unproven method to an unsolved problem, it’s impossible to get the wrong answer. In fact, the results are “not even wrong“; it’s impossible to get an answer of any value whatsoever, because there is no way of judging its correctness.

In contrast, the work of Christian and Dzemski (2007) on neck posture in Brachiosaurus warrants serious consideration, not because of the particular answer they got for Brachiosaurus, but because they got the right answers when they applied their method to extant long-necked animals (ostriches and camels; Dzemski and Christian 2007). Don Henderson and Ryosuke Motani, among others, have also been religious about ground-truthing their methods on extant animals before applying them to fossil taxa. That shouldn’t be  exceptional. It should be expected. It should be the minimum requirement for being included in the discussion.

Conclusion: Let’s move forward

I can’t accuse the makers of Walking With Dinosaurs or the designers of Dinosaurs: Ancient Fossils, New Discoveries of drinking the DinoMorph Kool-Aid. I don’t know that it is Kool-Aid. It might be fine wine. There’s red stuff in the cup, but no one has tasted it.

If you get nothing else from this post, please understand that I’m not saying the results of DinoMorph are either good or bad. I’m saying that there is currently no objective way of knowing. I want DinoMorph to work, but I want a DinoMorph made rigorous by the publication of supporting data from extant animals demonstrating its accuracy, and ranges of error demonstrating its precision.

If someone has a novel method they want to apply to dinosaurs or any other extinct animal, the burden of proof is on them to show that the method works. And if that evidence is not forthcoming, you–reviewers, editors, readers, science journalists, museum exhibit designers, documentary producers, netizens, laypeople–have the right to ask for it. And until you get that supporting evidence, you don’t have to take the results of the method seriously. Asking “how do you know that?” is the basis of science; it ought to be reflexive.

In the immortal words of Tom Holtz, “Sorry if that makes some people feel bad, but I’m not in the ‘make people feel good business’; I’m a scientist.”

References

• Christian, A. and Dzemski, G. 2007. Reconstruction of the cervical skeleton posture of Brachiosaurus brancai Janensch, 1914 by an analysis of the intervertebral stress along the neck and a comparison with the results of different approaches. Fossil Record 10: 38–49. (subscription required)
• Dzemski, G., and Christian, A. (2007) Flexibility along the neck of the ostrich (Struthio camelus) and consequences for the reconstruction of dinosaurs with extreme neck length. Journal of Morphology 268(8):701-714. (subscription required)
• Graur, D., and Martin, W. 2004. Reading the entrails of chickens: molecular timescales of evolution and the illusion of precision. Trends in Genetics 20:80-86.
• Stevens, K.A. 2002. DinoMorph: Parametric modeling of skeletal structures.  Senckenbergiana Lethaea 82(1): 23-34.
• Stevens, K.A. and Parrish, J.M. 1999. Neck posture and feeding habits of two Jurassic sauropod dinosaurs. Science 284: 798–800. (subscription required)
• Stevens, K.A. and Parrish, J.M. 2005a. Neck posture, dentition, and feeding strategies in Jurassic sauropod dinosaurs. In: V. Tidwell and K. Carpenter (eds.), Thunder−Lizards: The Sauropodomorph Dinosaurs, 212–232. Indiana University Press, Bloomington, Indiana.
• Stevens, K.A. and Parrish, J.M. 2005b. Digital reconstructions of sauropod dinosaurs and implications for feeding. In: K.A. Curry Rogers and J.A. Wilson (eds.), The Sauropods: Evolution and Paleobiology, 178–200. University of California Press, Berkeley, California.
• Taylor, M.P., Wedel, M.J. and Naish, D. 2009. Head and neck posture in sauropod dinosaurs inferred from extant animals. Acta Palaeontologica Polonica 54(2): 213-220.

Necks lie

Since we’re spending a few days on neck posture, I thought I’d expand on what Mike said about bunnies in the first post: in most cases, it is awfully hard to tell the angle of the cervical column when looking at a live animal. Because necks lie.

Take this horse (borrowed from here). You can see that the external outline of the neck, which is what you would see in the living animal, is pointed in a different direction than the cervical column.

And here’s why. Many mammals carry their heads and necks so that the cranio-cervical joint is up high and the head is angled down from it. At the base of the neck, tall neural spines on the anterior thoracic vertebrae support the nuchal ligament, which lifts the body profile far above the cervical vertebrae. Basically, the cervicals run from the lower or middle part of the neck at its base to near the top of the neck at the head end.

This mismatch holds no matter how the neck and head are oriented. When the animal lowers its head to graze, the cervical column is still angled up relative to the apparent angle of the neck defined by its dorsal and ventral margins.

But if you think that’s bad, you ain’t seen nothin’ yet.

In most of the smaller birds, like this budgie (from Evans 1969:fig. 5-6) the neck is much longer and more flexible than you would think based on the external profile. And check out the mismatch between the cervical column (in front) and the trachea (behind). That’s not drawn incorrectly; the trachea is outside the bundle of neck muscles that encloses the vertebrae, and it is free to slide around all over the place, and does so in many birds.

Also note that while the neck is extended past vertical, the extension occurs in the middle of the neck, not at the shoulder. The neck actually goes down from the craniocervical joint, not up. My guess is that there is a lot of this in climbing taxa that hold their torsos elevated. Vultures come to mind here, too. A useful reminder that in natural history we are usually dealing with norms, not laws.

In the pigeon, note again the fact that the mid-cervicals are angled up much more sharply than is the external profile of the neck. In fact, the external profile of the neck is angled forward while the mid-cervicals are angled backward. This excellent reconstruction is from this page, which has several others which also show that necks lie.

Lest anyone think that the pigeon was either an outlier or a case of artistic embellishment, here’s yet another rabbit, this time from Vidal et al. (1986: fig. 5a). Again, the mid-cervicals–actually, almost all of the cervicals–are angled backward, but the neck as a whole is pointing slightly forward.

As an aside, I think possibly it has blown some people’s minds that we have used so many rabbits as examples, both in the paper and in our blog coverage. What can we say? Rabbits are awesome.

Of course not all necks lie. With flamingos, what you see is what you get.

Giraffes: 20 feet of reticulated irony

Let’s see here: necks not vertical.

Necks not vertical.

Trying . . . very . . . hard . . . and . . . just . . . getting . . . to . . . vertical!

(I know it looks like the neck is just slightly less than vertical, but remember that necks lie, and the cervical column is steeper. In this animal, you could drop a plumb bob from the ear and it would track the course of the cervical vertebrae just about perfectly.)

Cat, not trying at all: cervical column past vertical (Vidal et al. 1986: fig. 2).

Rat, taking its ease (top): cervical column vertical. Guinea pig, straight chillin’ (bottom): cervical column past vertical (Vidal et al. 1986: fig. 5 b and c).

Here’s the irony: for  practically as long as sauropod neck posture has been contentious, giraffes have been held up as THE example of the most extreme (dude!) elevated neck postures out there. But in fact giraffes have to really reach to achieve vertical cervical postures that “ordinary” animals like cats, rats, guinea pigs, chickens, and, yes, rabbits, reach or exceed all the time.

Good paleobiology has to start with good biology. It’s high time that the sauropod neck posture debate got a reality infusion. Giraffe necks are extreme in terms of length, but not in terms of posture.

Speaking of sauropods…

All right, you’ve suffered long enough. Here’s your sauropod vert. Care to guess what it is?

References

• Evans, H.E. 1969. Anatomy of the budgerigar; pp. 45-112 in Petrak, M.L. (ed.), Diseases of Cage and Aviary Birds. Lea and Febiger, Philadelphia.
• Vidal, P.P., Graf, W., and Berthoz, A. 1986. The orientation of the cervical vertebral column in unrestrained awake animals. Experimental Brain Research 61: 549­-559.