Sideshow Collectibles Apatosaurus Maquette, Part 3: the neck

November 18, 2011

This is the third in a series of posts on the Apatosaurus maquette produced by Sideshow Collectibles. The rest of the series:

It is probably no surprise, given my proclivities, that I have more to say about the neck than about anything else. So unless I develop an abnormal curiosity about and mastery of, say, sauropod foot anatomy in the next few days, this will be the longest post in the series.

As with the head, the neck of the Apatosaurus maquette illustrates a lot of interesting anatomy. Some of this is unique to Apatosaurus and some of it is characteristic of sauropods in general. I’ll start with the general and move toward the specific.

As we’ve discussed before, the necks of most sauropods were not round in cross section (see here and here). The cervical ribs stuck out far enough ventrolaterally that even with a lot of muscle, the neck would have been fairly flat across the ventral surface, and in many taxa it would have been wider ventrally than dorsally.

The non-circular cross section would have been exaggerated in Apatosaurus, which had simply ridiculous cervical ribs (photo above is from this post). The widely bifurcated neural spines would also have created a broad and probably flattish surface on the dorsal aspect of the neck. The extreme width of the vertebrae and the cervical ribs created a very broad neck base. As in Camarasaurus, the base of the neck was a substantial fraction of the width of the thorax (discussed here). Consequently, the cervico-thoracic junction probably appeared more abrupt in narrow-necked taxa like Diplodocus and Giraffatitan, and more smoothly blended in Apatosaurus and Camarasaurus.

All of these features–the non-circular cross-section, the flattish dorsal and ventral surfaces, the wide neck base blending smoothly into the thorax–are captured in the Apatosaurus maquette.

The ventrolateral ‘corners’ of the neck have a ribbed appearance created by, well, ribs. Cervical ribs, that is, and big ones. In contrast to most other sauropods, which had long, overlapping cervical ribs, diplodocoids had short cervical ribs that did not overlap. But in Apatosaurus they were immense, proportionally larger than in any other sauropod and probably larger than in any other tetrapod. What Apatosaurus was doing with those immense ribs is beyond me. Some people have suggested combat, akin to the necking behavior of giraffes, and although I haven’t seen any evidence to support that hypothesis over others, neither does it strike me as far-fetched (an important nuance: giraffes use their heads as clubs, clearly not an option for the small-headed and fragile-skulled sauropods). Whatever the reason, the cervical ribs of Apatosaurus were amazingly large, and may well have been visible from the outside.

Mounted skeleton of Apatosaurus louisae in the Carnegie Museum, from Wikipedia.

Now this brings me to a something that, although not universal, has at least become fairly common in paleoart. This is the tendency by some artists to render (in 2D, 3D, or virtually) sauropods with dished-in areas along the neck, between the bony loops where the cervical ribs fuse to the centra. I am going to be as diplomatic as I can, since some of the people who have used this style of restoration are good friends of mine. But it’s a fine example of shrink-wrapped dinosaur syndrome, and it simply cannot be correct.

Adjacent cervical ribs loops in sauropods would have been spanned by intertransversarii muscles, as they are in all extant tetrapods. And outside of those single-segment muscles were long belts of flexor colli lateralis and cervicalis ascendens, which are also anchored by the cervical rib loops. All of these muscles are present in birds, and only vary in their degree of development in different parts of the neck and in different taxa. The spaces between adjacent cervical rib loops are not only not dished-in, they actually bulge outward, as in the turkey neck above.

And we’re still not done; running up through the cervical rib loops, underneath all of those muscles, were pneumatic diverticula. Not just any diverticula, but the big lateral diverticula that carried the air up the neck from the cervical air sacs at the base of the neck to the vertebrae near the head end (diverticula are reconstructed here in a cervical vertebra of Brachiosaurus, from Wedel 2005: fig. 7.2). Now, it’s unlikely that the diverticula exerted any outward pressure on the lateral neck muscles, but they were still there, occupying space (except when the muscles bulged inward and impinged on them during contraction), and with the muscles they would have prevented the neck from having visible indentations between the cervical rib loops of adjacent vertebrae.

Okay, so sauropod necks shouldn’t be dished in. But might the cervical ribs have stuck out? It might seem like the same question, only seen from the other side, but it’s not. We’ve established that adjacent cervical rib loops supported bands of single-segment muscles that spanned from one vertebra to the next, and longer, multi-segment muscles that crossed many vertebrae. But could the bony eminences of the cervical ribs have projected outward, through the muscle, and made bumps visible through the skin? The idea has some precedent in the literature; in his 1988 paper on Giraffatitan, Greg Paul (p. 9) argued that,

The intensely pneumatic and very bird-like neck vertebrae of sauropods were much lighter in life than they look as mineralized fossils, and the skulls they supported were small. This suggests that the cervical musculature was also light and rather bird-like, just sufficient to properly operate the head-neck system. The bulge of each neck vertebra was probably visible in life, as is the case in large ground birds, camels, and giraffes.

Paul has illustrated this in various iterations of his Tendaguru Giraffatitan scene; the one below is from The Princeton Field Guide to Dinosaurs (Paul 2010) and is borrowed from the Princeton University Press blog.

There is much to discuss here. First, I have no qualms about being able to see individual vertebrae in the necks of camels and giraffes, and it’s not hard to find photos that show these. It makes sense: these are stinkin’ mammals with the usual seven cervical vertebrae, so the verts have to be longer, proportionally, and bend farther at each joint than in other long-necked animals. I’m more skeptical about the claim that individual vertebrae can be seen in the necks of large ground birds. I’ve dissected the necks of an ostrich, an emu, and a rhea, and it seems to me that the neck muscles are just too thick to allow the individual vertebrae to be picked out. In a flamingo, certainly–see the sharp bends in the cranial half of the neck in the photo below–but flamingos have freakishly skinny necks even for birds, and their cervicals are proportionally much longer, relative to their width, than those of even ostriches.

What about sauropods? As discussed in this post, sauropod cervicals were almost certainly proportionally closer to the surface of the neck than in birds, which would tend to make them more likely to be visible as bulges. However, the long bony rods of the cervical ribs in most sauropods would have kept the ventral profile of the neck fairly smooth. The ossified cervical ribs of sauropods ran in bundles, just like the unossified hypaxial tendons in birds (that’s Vanessa Graff dissecting the neck of Rhea americana below), and whereas the latter are free to bend sharply around the ventral prominences of each vertebra, the former were probably not.

All of which applies to sauropods with long, overlapping cervical ribs, which is most of them. But as mentioned above, diplodocoids had short cervical ribs. Presumably they had long hypaxial tendons that looked very much like the cervical ribs of sauropods but just weren’t ossified. Whether the vertebrae could have bent enough at each segment to create bulges, and whether the overlying muscles were thin enough to allow those bends to be seen, are difficult questions. No-one actually knows how much muscle there was on sauropod necks, not even within a factor of two.  There has been no realistic attempt, even, to publish on this. Published works on sauropod neck muscles (Wedel and Sanders 2002, Schwarz et al. 2007) have focused on their topology, not their cross-sectional area or bulk.

But then there’s Apatosaurus (AMNH mount shown here). If any sauropod had a chance of having its cervical vertebrae visible from the outside, surely it was Apatosaurus. And in fact I am not opposed to the idea. The cervical ribs of Apatosaurus are unusual not only in being large and robust, but also in curving dorsally toward their tips. If one accepts that the cervical ribs of sauropods are ossified hypaxial tendons–which seems almost unarguable, given that the cervical ribs in both crocs and birds anchor converging V-shaped wedges of muscle–then the ossified portion of each cervical rib must point back along the direction taken by the unossified portion of the tendon. In which case, the upwardly-curving cervical ribs in Apatosaurus suggest that the muscles inserting on them were doing so at least partially from above. So maybe the most ventrolateral portion of each rib did stick out enough to make an externally visible bulge.

Maybe. Many Apatosaurus cervical ribs also have bony bumps at their ventrolateral margins–the ‘ventrolateral processes’ or VLPs illustrated by Wedel and Sander (2002: fig. 3). If these processes anchored neck muscles, as seems likely, then even the immense cervical ribs of Apatosaurus might have been jacketed in enough muscle to prevent them from showing through on the outside.

Still. It’s Apatosaurus. It’s simply a ridiculous animal–a sauropod among sauropods. If this were a model of Mamenchisaurus and it had visible bulges for the cervical rib loops, I’d be deeply skeptical. For Apatosaurus, it’s at least plausible.

Because the cervical ribs are visible in the maquette as distinct bulges, it’s possible to count the cervical vertebrae. Apatosaurus has 15 cervicals, and that seems about right for the maquette. The neck bumps reveal 11 cervicals, but they don’t run up all the way to the head. This is realistic: the most anterior cervicals anchored muscles that supported and moved the head, and these overlie the segmental muscles and cervical ribs in extant tetrapods. The most anterior part of the neck in the maquette, with no cervical rib bumps, looks about the right length to contain C1-C3. Plus the 11 vertebrae visible from their bumps, that makes 14 cervicals, and the 15th was probably buried in the anterior body wall.

One last thing: because the cervical ribs are huge, the neck of Apatosaurus was fat. To the point that the head looks almost comically tiny, even though it’s about the right size for a sauropod head. I first got a visceral appreciation for this when I was making my own skeletal reconstruction of Apatosaurus, for a project that eventually evaporated into limbo. Once you draw an outline of flesh around the vertebrae, the weirdness of the massive neck of Apatosaurus is thrown into stark relief. Apatosaurus is robust all over, but even on such a massive animal the neck seems anomalous. I don’t know what Apatosaurus was doing with its neck, but it’s hard not to think that it must have been doing something. Anyway, I bring this up because the maquette captures the neck-fatness very well. So much so that when I sit back from the computer and my eyes roam around the office and fall on the maquette, I can’t help thinking, for the thousandth time, “Damn, that’s weird.”

In sum, the neck of the Sideshow Apatosaurus maquette gets the non-circular cross-section right, appears to have the correct number of cervical vertebrae, and looks weirdly fat, which turns out to be just right for Apatosaurus. The bumps for the individual vertebrae are plausible, and the maquette correctly avoids the dished-in, emaciated appearance–cocaine chic for sauropods–that has become popular in recent years. It manages to be eye-catching and even mildly disturbing, even for a jaded sauropodologist like yours truly, in that it confronts me with the essential weirdness of sauropods in general, and of Apatosaurus in particular. These are all very good things.

Next time: as much of the rest of the body as I can fit into one post (all of it, it turned out).

References

25 Responses to “Sideshow Collectibles Apatosaurus Maquette, Part 3: the neck”

  1. kattato Garu Says:

    Great post! and I am very envious of the maquette which would look great with my lovely but weirdly large-footed and bunny-handed Papo Allosaurus. if you ever want to get other palaeontology chaps to join the ethical drawing of sauropods club, you’ll have to find another acronym than PaEDOS!!!

  2. Filipe Says:

    I suppose there is no consensus relating to sauropod fermentation (hindgut?, foregut? endogenous cellulases?). Is there enough volume along the neck for the esophagus to be more than a simple tube and to more like a chain of hoazin like crops for prefermentation/breaking of food matter?

  3. Matt Wedel Says:

    I suppose there is no consensus relating to sauropod fermentation (hindgut?, foregut? endogenous cellulases?).

    Almost certainly hindgut fermentation. This is discussed quite a bit in the big Sander et al. 2010 paper in Biological Reviews, with citations of many recent papers on gut scaling and fermentation in extant animals.

    Is there enough volume along the neck for the esophagus to be more than a simple tube and to more like a chain of hoazin like crops for prefermentation/breaking of food matter?

    Three things. First, the esophagus is not bound by bone so the fossils don’t actually constrain its volume. Second, the torsos of sauropods were large enough to comfortably contain the estimated volume of the digestive tract. Third, since the esophagus doesn’t leave any traces on the skeleton and is unlikely to be preserved in a sauropod, there’s no way to test the hypothesis of neck stomachs. And given what we know about sauropod torsos, there is also no need.

    Don’t take my word for it:

    Sander, P. M., A. Christian, M. Clauss, R. Fechner, C. T. Gee, E.-M. Griebeler, H.-C. Gunga, J. Hummel, H. Mallison, S. F. Perry, H. Preuschoft, O. W. M. Rauhut, K. Remes, T. Tütken, O. Wings, and U. Witzel. 2010. Biology of the sauropod dinosaurs: the evolution of gigantism. Biological Reviews. doi: 10.1111/j.1469-185X.2010.00137.x.


  4. […] over on SV-POW, Matt Wedel has gone and beaten me to the punch on this exact subject. Inevitably he does it in more detail and […]

  5. mattvr Says:

    Thanks for this really informative post Matt.
    Information like this is a great reference for those of us with a more generalized knowledge of anatomy who are attempting to bring accuracy into our depictions of animals.

  6. Matt Wedel Says:

    Thank you for the kind words. Comments like these keep us going. Glad it was useful!

  7. mattvr Says:

    It all goes into the knowledge bank for future reference. Part of the ‘paleoart’ gig is respecting the scientist and their detailed knowledge.

  8. Mark Witton Says:

    Great post, Matt, as was the last. These are almost turning into a ‘how to’ guide for reconstructing sauropod anatomy, albeit one where the answers to important questions – lips, vertebral bulges and so fourth – are explained in appreciated detail.

    It would be cool to see other bloggers with heavy science credentials doing similar things for other clades: it may help iron out some of the more common mistakes in palaeoart as well as enlighten us to the specific anatomy of different groups. I have considered writing something along this line for pterosaurs, but finding the time to do it has been tricky.


  9. […] was the raison d’etre for this post, and turned up again with different muscles labeled in one of the recent Apatosaurus maquette review posts. Mike and I ate those muscles, by the […]

  10. Warren B. Says:

    “Do your part this holiday season. Draw, paint, sculpt or render a healthy sauropod.”

    Yessir!

    I have to agree with other comments: these four posts, and their links to various papers and other blog posts, look like a very useful resource for restoration. I think they’ll be my go-to bookmark on ‘how to draw sauropods’.

  11. dmaas Says:

    What Mark says… this is a fantastic resource.
    I particularly appreciate the way you acknowledge things that can’t be known as well – clearly declaring what can be known, yet letting your personal views shine through.

  12. Filipe Says:

    Thanks, I had read that review but found the arguments for an hindgut system rather weak. Didn’t think it was the sort of a consensus.

  13. Matt Wedel Says:

    Well, it’s not airtight, and probably never will be, barring really spectacular preservation of the kind that would make the stuff from Liaoning look pathetic. But hindgut fermentation seems more likely than foregut, and insofar as there is a consensus right now, it’s for hindgut fermentation.


  14. […] a little irksome – depending on your opinion, of course. I’ll admit to having been convinced by Matt Wedel that brachiosaur necks probably shouldn’t be ‘caved in’ like this (especially as […]


  15. […] of every post-axial Apatosaurus cervical (see these posts [#1, #2, #3] for some crazy examples, and this post for more pictures and discussion). The giant cervical ribs are present even in very juvenile […]


  16. […] the internet. For example, Matt Wedel used an image of the neck of AMNH’s Apatosaurus mount in an SV-POW! post. It makes me wonder, if Brett were a paleontologist instead “merely” a community college […]

  17. Quora Says:

    How did Apatosaurus avoid getting neck pain? And what counterforce on the base of its neck was necessary in order to support its super-long neck?…

    The science behind Apatosaurus’ neck is actually pretty interesting – at least if you’re a dinosaur geek like me! To begin with, the long neck of Apatosaurus which measured in at around 40 feet long was counter weighted by a long tapered tail that me…


  18. […] the first to restore Sauroposeidon as a somphospondyl. Mike and I also voiced our opposition to the starvation-thinned neck, and Mike suggested that the forelimb was too lightly muscled and that the ‘fingers’ […]


  19. […] Neck wrinkles possibly corresponding to vertebrae: okay, just this once. […]


  20. […] This seems especially likely in Apatosaurus, where the neck length is unremarkable** but the neck fatness is frankly bizarre (and even inspired a Star Wars […]


  21. […] this imbalance, if it came to a fight, my money would be on the Brontosaurus: it’s just insanely robust compared with pretty much all other sauropods. If they got into a neck-bashing contest (as giraffes […]


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