Emeus crassus mount

In a back room at the Field Museum, from my visit in 2012.

I took a lot of photos of the neck, which nicely records the transition in neural spine shape from simple to bifurcated–a topic of interest to sauropodophiles.

Emeus crassus neural spines

Are you a lover of sauropod necks?

Do you long to demonstrate to your friends and family how much better[1] they are than the necks of other long-necked critters?

Are you crazy for the Taylor and Wedel (2013a) paper on why sauropods had long necks; and why giraffes have short necks, but disappointed that it’s not, until now, been obtainable in T-shirt form?

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If so, it’s your lucky day! You can now buy a T-shirt featuring Figure 1 on the front (necks of a human, giraffe, ostrich, Paraceratherium[2], Therizinosaurus, Gigantoraptor, Arambourgiania and Tanystropheus) and Figure 3 on the back (necks of Diplodocus, Puertasaurus, Sauroposeidon, Mamenchisaurus and Supersaurus).

And here it is in real life — sorry I couldn’t get a more photogenic model at short notice.

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And here are the original figures as they appeared in the paper. The full captions, as reproduced here, are also on the shirts — just in case you need to check details while you’re out and about.

Figure 1. Necks of long-necked non-sauropods, to scale. The giraffe and Paraceratherium are the longest necked mammals; the ostrich is the longest necked extant bird; Therizinosaurus and Gigantoraptor are the largest representatives of two long-necked theropod clades; Arambourgiania is the longest necked pterosaur; and Tanystropheus has a uniquely long neck relative to torso length. Human head modified from Gray’s Anatomy (1918 edition, fig. 602). Giraffe modified from photograph by Kevin Ryder (CC BY, http://flic.kr/p/cRvCcQ). Ostrich modified from photograph by “kei51” (CC BY, http://flic.kr/p/cowoYW). Paraceratherium modified from Osborn (1923, figure 1). Therizinosaurus modified from Nothronychus reconstruction by Scott Hartman. Gigantoraptor modified from Heyuannia reconstruction by Scott Hartman. Arambourgiania modified from Zhejiangopterus reconstruction by Witton & Naish (2008, figure 1). Tanystropheus modified from reconstruction by David Peters. Alternating blue and pink bars are 1 m tall.

Figure 1. Necks of long-necked non-sauropods, to scale. The giraffe and Paraceratherium are the longest necked mammals; the ostrich is the longest necked extant bird; Therizinosaurus and Gigantoraptor are the largest representatives of two long-necked theropod clades; Arambourgiania is the longest necked pterosaur; and Tanystropheus has a uniquely long neck relative to torso length. Human head modified from Gray’s Anatomy (1918 edition, fig. 602). Giraffe modified from photograph by Kevin Ryder (CC BY, http://flic.kr/p/cRvCcQ). Ostrich modified from photograph by “kei51” (CC BY, http://flic.kr/p/cowoYW). Paraceratherium modified from Osborn (1923, figure 1). Therizinosaurus modified from Nothronychus reconstruction by Scott Hartman. Gigantoraptor modified from Heyuannia reconstruction by Scott Hartman. Arambourgiania modified from Zhejiangopterus reconstruction by Witton & Naish (2008, figure 1). Tanystropheus modified from reconstruction by David Peters. Alternating blue and pink bars are 1 m tall.

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Figure 3. Necks of long-necked sauropods, to scale. Diplodocus, modified from elements in Hatcher (1901, plate 3), represents a “typical” long-necked sauropod, familiar from many mounted skeletons in museums. Puertasaurus, Sauroposeidon, Mamenchisaurus and Supersaurus modified from Scott Hartman’s reconstructions of Futalognkosaurus, Cedarosaurus, Mamenchisaurus and Supersaurus respectively. Alternating pink and blue bars are one meter in width. Inset shows Fig. 1 to the same scale.

No doubt these will be all the rage at SVPCA this year!

So get your T-shirts!

Update (the same evening)

As suggested by Kevin, I’ve now made the shirt available in a selection of eight versions: four men’s shirt, two women’s, and two kids. I don’t really understand what the differences are between them all, but they seemed to be the saner choices among those offered by Cafe Press. You can get any or all of them here. The shirt modelled above is the one called simple “White T-Shirt”. Please be aware that unlike all the others, the “Value T-Shirt” has no printing on the back — only Figure 1 on the front.

Notes

[1] i.e. bigger.

[2] Not to be confused with Paramecium.

References

Taylor, Michael P., and Mathew J. Wedel. 2013. Why sauropods had long necks; and why giraffes have short necks. PeerJ 1:e36. doi:10.7717/peerj.36

Back in 2010, SVPCA was held in Cambridge. (It was the year that I gave the “why giraffes have short necks” talk [abstract, slides].)

While we were there, I took a lot of photos in the excellent Cambridge University Museum of Zoology, which was just across the courtyard from the lecture theatre where the scientific sessions were held.

In light of the recent discussion here on how many cervical vertebrae giraffes have (spoiler: seven), I thought it would be good to air the sloth photos, since the two genera of sloths constitute 66% of all the mammals have that a cervical count other than seven. (The third is the manatee Trichechus, with six cervicals.)

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Three-toed sloth, Bradypus tridactylus. This specimen has nine cervicals vertabrae, but apparently the count can vary between eight and ten in different individuals.

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Three-toed sloth, Bradypus tridactylus, full skeleton.

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Two-toed sloth, Choloepus didactylus. Six cervical vertebrae.

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Two-toed sloth, Choloepus didactylus, full skeleton.

 

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

Okay, special dissection post, coming to you live from the Symposium  of Vertebrate Palaeontology and Comparative Anatomy in Lyme Regis, on the Jurassic coast of England, well past my bedtime. First, check out this comment from Neil and see the linked image of some neck muscles in the anhinga. Here’s a small version I’m swiping. There are a couple of short, single-segment muscles shown, but the big long ones in this image are longus colli ventralis (on the ‘front’ or ‘bottom’ of the neck) and longus colli dorsalis (on the ‘back’ or ‘top’).

Now, grok these photos of the same dorsal muscle. Or muscle group, if you prefer. Note that in all cases shown here and in the link–anhinga, rhea, and turkey–the muscle inserts on the anterior cervical vertebrae, and not on the skull.

In Rhea:

In Meleagris (turkey):

The rhea was dissected by Vanessa back at Western a couple of weeks ago, the turkey by me on Mike’s dining room table on Monday. Full story to follow…at some point.

In the meantime, go buy your own turkey and cut up its neck. It’s cheap and you’ll learn a ton.

Necks lie, redux

September 1, 2011

In a recent post I showed photos of the trachea in a rhea, running not along the ventral surface of the neck but along the right side. I promised to show that this is not uncommon, that the trachea and esophagus of birds are usually free to slide around under the skin and are not constrained to like along the ventral midline of the neck, as they usually are in mammals. Here goes.

Here’s figure 5 from van der Leeuw et al. (2001): a lateral x-ray of a duck, reaching up just a bit with its head and neck, possibly to get a bite or just look around. Click through for the unlabeled version.

There’s a LOT of stuff going on in this image:

  • As promised, the trachea (blue lines) is taking a very different path to the head than the vertebrae and skeletal muscles.
  • As usual for tetrapods, the neck is extended at the base in the caudal half and flexed at the head in the cranial half.
  • The epaxial (dorsal) muscles at the base of the neck are not tied down to the vertebral column so they are free to bowstring across the U-bend at the base of the neck (black arrow)–this was the point of the figure in the original paper. Although the gross outline of the neck also deviates from the vertebral column on the ventral side near the head, this is caused by the trachea and gullet approaching the pharynx, not because the hypaxial muscles are bowstringed across the curve.
  • As the post title intimates, this neck lies: the cervical vertebrae are significantly more extended than one would expect based on the external appearance of the neck alone. The red line shows the angle of the most strongly retroverted vertebra, which I measure at 48.5 degrees from vertical (41.5 degrees above horizontal)–slightly closer to horizontal than to vertical! We have seen this before, in most mammals and in a couple of small birds (see this post); here we see it even in a reasonably large, long-necked bird.
  • Worse, the gross outline of the neck–what one can see from the outside–lines up with nothing on the inside: the trachea is less curved and the vertebral column is more curved.

Same points again, this time in a chicken in an alert posture (Vidal et al. 1986: fig. 7). Here the most strongly retroverted cervical is 36 degrees from vertical (54 degrees above horizontal).

What’s all this got to do with sauropods?

First, it shows that even in animals with long, slender necks, it’s not enough to show a photo or painting of an extant animal and make assertions about what the cervicals are doing (necks lie, again). It’s even less defensible to make the dual assertions that (a) the gross outline of the neck shows the path of the cervicals and (b) the cervicals are in ONP, all based on a photo or painting of a living animal. The first point can only be established by radiography, and the second by manipulation of the skeleton, either physically or digitally. It may seem like I’m tilting at windmills here, but we’ve seen these very assertions made in conference talks. As always, we’ll follow where the evidence leads, but not until we see some actual evidence.

Second,  I am increasingly haunted by the idea that we are all waaay too influenced, even (maybe especially) subconsciously, by big mammals when we think about sauropods and their necks. Big mammals–like, say, horses and giraffes–have:

  • only 7 cervical vertebrae;
  • lots of big muscles that attach to the thorax and the head and cross the cervical column without attaching to it much or at all;
  • presacral neural spines that max out, height-wise, over the shoulders, creating withers;
  • alert neck postures that are elevated (like all tetrapods) but often short of vertical, with the vertebrae often held more-or-less straight through the middle section of the neck (camels are an obvious exception here).

In contrast, birds have:

  • many cervical vertebrae, from a 12  or so up to 27 or 28;
  • almost no muscles that span from thorax to skull;
  • presacral neural spines that rise monotonically to the synsacrum (except–maybe–in Giraffatitan);
  • alert neck postures that are S-shaped, with the craniocervical joint over or just slightly in front of the cervicodorsal junction.

Which group sauropods had more in common with is left as an exercise for the reader.

References

  • van der Leeuw, A.H.J., Bout, R.G., and Zweers, G.A. 2001. Evolutionary morphology of the neck system in ratites, fowl, and waterfowl. Netherlands Journal of Zoology 51(2):243-262.
  • 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.

Wedel’s Theorem:

freezer full of interesting dead animals + great anatomy student who actually wants to get up on Saturday morning and dissect = happiness

The rhea has been the gift that keeps on giving. Saturday was my fourth session with some part of this bird, going back to 2006 (previous posts are here, here, and here). The first two sessions were just about reducing the bird to its component parts, and the last session was all about midline structures.

The goal for the neck is to dissect down to the vertebrae and document everything along the way–muscles, tendons, fascia, blood vessels, and especially diverticula. In the past I have been pessimistic about the chances of seeing diverticula without having them injected with latex or resin or something. But this bird is changing my mind, as we saw in a previous post and as you can see below.

The goal for Vanessa is to grok all of this anatomy, and hopefully make some publishable observations along the way. She has a chance to do something that I think is rather rare for a sauropod paleobiologist, which is to get a firm, dissection-based grounding in bird and croc anatomy before she first sets foot in a museum collection to play with sauropod bones.

That sounds awesome, and probably will be awesome, but before there can be any awesomeness, the fascia has to be picked off the neck. And by ‘picked’ I mean ‘actually cut away, millimeter by arduous millimeter’. It wasn’t that bad everywhere–the fascia over the long dorsal muscles came off very easily. But the lateral neck muscles were actually originating, in part, from the inner surface of the fascia. That’s not unheard of, it happens in the human forearm and leg all the time, but I’ve never seen it as consistently as in this rhea. So picking fascia took a loooong time–that’s what Vanessa is doing in the photo at top.

Once the fascia was off, Vanessa started parting out the long tendons of the hypaxial muscles in the left half of the neck. Meanwhile, I started stripping fascia from the right half. I had forgotten that the right half of the neck still had the trachea and esophagus adhered to the side. That probably sounds weird, given that our trachea and esophagus–and those of most mammals–run right down the middle of our necks and aren’t free to move around much. In birds, they’re more free-floating and can drift around between the skin and the vertebral muscles, sometimes even ending up dorsal to the  vertebral column–there’s a great x-ray of a duck in a  2001 paper that shows this, which I’ll have to blog sometime.

Anyway, when I cut the fascia to pull back the trachea and esophagus, I found that they were separated from the underlying tissues by a dense network of pneumatic diverticula winding through the fascia.

I had heard, anecdotally, of networks of diverticula described as looking like bubble wrap. I can now confirm that is true, for at least some networks. What was especially cool about these is that they were occupying space that would be filled with adipose or other loose connective tissue in a mammal, which illustrates the point that pneumatic epithelium seems to replace many kinds of connective tissue, not just bone–something Pat O’Connor has talked about, and which I also briefly discussed in this post.

I should mention that there was no connection between these diverticula and the trachea, as there is between the subcutaneous throat sac and the trachea in the emu (story and pictures here).

While I was geeking out on diverticula, Vanessa was methodically separating the long hypaxial muscles, which looked pretty cool all fanned out.

And that’s all we had time for on Saturday. But we’re cutting again soon, so more pictures should be along shortly.

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