From the collections of the American Museum of Natural History, I give you the sacrum and fused ilia of “Apatosaurusminimus AMNH 675, as correctly identified by Steve P in a comment to the previous post:

"Apatosaurus" minimus sacrum with fused ilium, right lateral view

As Steve P rightly pointed out, AMNH 675 was designated as Brontosaurus sp. by Osborn (1904), and made the type of Apatosaurus minimus by Mook (1917).

It’s been known for some time that whatever this is, it’s not Apatosaurus — see for example McIntosh (1990a:398), McIntosh (1990b:59) and Upchurch et al. (2004:298). But what actually is it? Well, at the moment, no-one knows. Matt and I now have a manuscript in prep that we hope will somewhat elucidate this question. More to come on this specimen, most likely.

References

McIntosh, John S. 1990a. Sauropoda. In The Dinosauria, pp. 345–401. Berkeley and Los Angeles: University of California Press.

McIntosh, John S. 1990b. Species Determination in Sauropod Dinosaurs with Tentative Suggestions for the Their Classification. In Dinosaur Systematics: Approaches and Perspectives, pp. 53–69. Cambridge: Cambridge University Press.

Mook, Charles C. 1917. Criteria for the determination of species in the Sauropoda, with description of a new species of Apatosaurus. Bulletin of the American Museum of Natural History 38:355-360.

Osborn, Henry F. 1904. Manus, sacrum, and caudals of Sauropoda. Bulletin of the American Museum of Natural History 20:181-190.

Upchurch, Paul, Paul M Barrett, and Peter Dodson. 2004. Sauropoda” In The Dinosauria, 2nd Edition, pp. 259–322. Berkeley and Los Angeles: University of California Press.

A couple of posts back, when Matt was talking about turtle laminae, he included a photo of me in front of the skeleton of the giant turtle Archelon. Also in that photo is the tripod I was using — if you want to call it that — a tripod of altogether startling inadequacy. Here it is again, this time in the collections of the AMNH:

(Bonus SV-POW! points for anyone who can tell me what taxon or specimen I am working on. Sorry, Heinrich, you’re disqualified, since you already know.)

Why did we use such a poor tripod? Matt was planning to bring a proper one, but at the last minute decided to downsize his luggage by taking one small enough to fit into a smaller bag — in fact, it’s the tripod that came free with a telescope he recently bought. Not a good move: it was too short for many of the shots we wanted to take, too flimsy to properly stabilise the camera in many situations, and didn’t have enough degrees of freedom to let us get every shot we wanted from the best position.

Still, it was better than nothing, and we did contrive to get all the specimen photos we needed.

At the end of the week, when we finished up in collections and went to catch our taxi to the airport, Matt left the tripod behind. I emailed our AMNH host Carl Mehling to explain:

Matt deliberately left behind his tripod — it’s on the desk where we had the pelvic elements. He has much better tripods at home, and regrets the false economy of bringing that lighter and less stable one. But we figured it would be better than nothing for the use of anyone who turns up in collections with no tripod at all, so please feel free to make it available to visitors. Matt asks only that it be known as “The Mathew J. Wedel Memorial Tripod”.

Carl replied:

Thanks so much for the tripod – I KNOW it will come in handy!

My response:

Ah, sorry about this but my client insists that it must be known by its full title The Mathew J. Wedel Memorial Tripod at all times. If necessary, you may abbreviate it to TMJWMT on second and subsequent mentions.

Carl’s reply:

I can engrave it in the Lab and apply a B72/India Ink/B72 sandwich acronym/monogram on it. I will also construct an archival museum mount for it and put a security chip in its brain.

That’s when Matt himself weighed in:

Oh, and be sure that when the tripod is not in use it is stored in an airtight positive pressure chamber full of an inert gas. It should also be polished twice daily with the down of a hatchling bald eagle (fresh down each time, naturally). Finally, the tripod itself should be listed as an author on any publications that include photos taken with it. Please send a runner to my office in California to confirm that these instructions will be carried out to the letter.

The runner hasn’t arrived yet (to my knowledge) but I think we can take it as read that Carl will comply with these very reasonable conditions.

So, folks! If ever you’re working in the AMNH big-bone room, and you find you’ve forgotten your tripod … you might just be lucky enough to be allowed use of the Mathew J. Wedel Memorial Tripod!

Sometimes you just can’t make this stuff up.

You may recall a story from the Onion Our Dumb Century book, allegedly from 1904, about the skeleton of Satan being discovered in Wyoming. Mike used his occult powers to put together this scan from freely available online sources:

If you scrutinize the above image carefully, you’ll see that ‘Satan’ is an Allosaurus (I’m no theropod booster, but I always thought that was a little harsh on T. rex).

Why am I telling you this? Because last week Mike and I were toiling in the big bone room in the basement of the AMNH when we came across AMNH 666.

It’s an ilium. (Of course it would have to be an appendicular element. Vertebrae are from on high [or dorsal, if you prefer].)

Of Allosaurus!

The stomach-churning color here could be a manifestation of diabolical power, or just what happens when you try to photograph a pink specimen label on a yellow-orange forklift.

After this harrowing encounter, we cleansed our bodies, minds, and souls with street-vendor hot dogs and The Avengers.* That particular mode of exorcism may not be the most effective–I felt distinctly dodgy that evening. But the next day we received illumination at the Altar of Sauropod Awesomeness and were soon back to what we jokingly refer to as normal.

* The best way to see The Avengers is by going up to the observation deck of the Empire State Building shortly beforehand, so big swathes of the Manhattan skyline will still be in your mental RAM during the big final battle. I understand it’s not an option for everyone.

Mike gets a shot of a sauropod sacrum in the AMNH basement.

…with sauropod bones!

Lots of basements have them. Some basements have had them for decades, and other basements have been newly constructed to house them. So you can take advantage of that retro chic while taking your basement into the 21st century!

What the heck am I talking about?

Matt ponders the mysteries of evolution in the AMNH basement.

One of the nifty features of WordPress is that you can track the search terms that people are using to find your blog. After Mike put up his “Suboptimal location of Mamenchisaurus” post, we noticed that one of the top search terms bringing people to SV-POW! was ‘basement’. Yeah, that’s right, ‘basement’. In fact, ‘basement’ is the 5th highest search term of all time that has brought people to SV-POW! And that’s not unusual–in fact, of the top 5 search terms bringing people here, only one is sauropod-related (Brachiosaurus, at number 2).

As of this posting, here are the Top 10 non-sauropod search terms of all time that have led people to SV-POW!, listed by rank, and including the number of hits in parentheses:

1. rabbit (18,235)

3. leopard seal (12,797) — this explains why “Sorting out Cetiosaurus nomenclature”, which even Mike admits is the most boring topic we’ve ever covered here, is the 11th most popular post of all time on this blog!

4. flamingo (10,974)

5. basement (9743)

12. twinkie (3434)

14. flamingos (3102) — double dipping for the “Necks lie” post!

20. pig skull (2099)

21. savannah monitor (2078)

22. varanus exanthematicus (1936) — double dipping for “Four complete, articulated, extant sauropod skeletons–yes, really!”

24. shish kebab (1660) — double dipping for “Sauropods were corn-on-the-cob, not shish kebabs”.

Mike and Darren discover a new dwarf sauropod in the basement at Oxford.

We’re apparently getting a lot of hits from people who want to remodel their basements. I’m all for that (the remodeling, and the extra hits), so I’m embracing it. You want basements, we got ‘em. We’ll drown you in pictures of sauropod vertebrae in basements. Did I say basement? Basement, basement, basement!

(Why am I pushing basement and not rabbit, flamingo, or leopard seal? Partly because basement used to be our number 1 search term and I want to see its fortunes rise again. Partly because those other things are at least biological, and it cracks me up to have a common architectural term bringing people to the blog. And partly because I want to upstage John and his freezers.)

Basement Renovation Instructions

This short guide will help you with your project.

Is your basement in a museum?

If YES, then:

1. Fill it with sauropod vertebrae.

2. Call us.

If NO, then:

1. Fill it with anything you like except sauropod vertebrae.

2. Support your local museum.

Don’t forget: basement!

Hello again, old friend

December 5, 2011

This week the SV-POW!sketeers are off to Bonn, Germany, for the Second International Workshop on Sauropod Biology and Gigantism. All three of us will be there, plus SV-POW! guest blogger Heinrich Mallison, plus Wedel Lab grad student Vanessa Graff, plus about 50 other awesome scientists from around the world. So we’ll have a ton of fun, but we probably won’t get much posted.

In the meantime, enjoy this cool encounter from the bone cellar at the Humboldt Museum in Berlin, where Mike and I fetched up at the end of the last IWSBG back in 2008. It’s a transversely-sectioned dorsal centrum of Giraffatitan, one that Janensch illustrated in his 1950 monograph on the vertebrae of Giraffatitan. Mike and I were very familiar with the cross-section image from the paper, so it was cool and a bit unreal to find the actual item.

Reference

Janensch, Werner. 1950. Die Wirbelsaule von Brachiosaurus brancai. Palaeontographica (Suppl. 7) 3:27-93.

Back when Darren and I did the Xenoposeidon description, we were young and foolish, and only illustrated the holotype vertebra NHM R2095 in four aspects: left and right lateral, anterior and posterior.  No dorsal or ventral views.

Also, because the figure was intended for Palaeontology, which prints only in greyscale, I stupidly prepared the figure in greyscale, rather than preparing it in colour and then flattening it down at the last moment.  (Happily I’d learned that lesson by the time we did our neck-posture paper: although it was destined for Acta Palaeontologia Polonica, which also prints in greyscale, and though the PDF uses greyscale figures, the online full-resolution figures are in colour.)

As if that wasn’t dumb enough, I also composited the four featured views such that the two lateral views were adjacent, and above the anterior and posterior views — so it wasn’t easy to match up features on the sides and front/back between the views.  Since then, I have landed on a better way of presenting multi-view figures, as in my much-admire’d turkey cervical and pig skull images.

So, putting it all together, here is how we should have illustrated illustrated Xenoposeidon back in 2007 (click through for high resolution):

(Top row: dorsal view, with anterior facing left; middle row, from left to right: anterior, left lateral, posterior, right lateral; bottom row, ventral view, with anterior facing left.  As always with images of NHM-owned material, this is copyright the NHM.)

Of course, if we’d published in PLoS ONE, then this high-resolution (4775 x 4095), full colour image could have been the published one rather than an afterthought on a blog somewhere.  But we didn’t: back then, we weren’t so aware of the opportunities available to us now that we live in the Shiny Digital Future.

In other news, the boys and I all registered Xbox Live accounts a few days ago.  I chose the name “Xenoposeidon”, only to find to my amazement that someone else had already registered it.  But “Brontomerus” was free, so I used that instead.

Vanessa Graff and I spent yesterday working in the herpetology and ornithology collections at the Natural History Museum of Los Angeles County (LACM). The herpetology collections manager, Neftali Comacho, pointed us to this skull of Alligator mississippiensis. It’s not world’s biggest gator–about which more in a second–but it’s the biggest I’ve seen in person. Normally it lives in a big rubbermaid tub in the collections area, but this Sunday it will be out on display for Reptile and Amphibian Appreciation Day (RAAD) at the LACM. RAAD will include guest talks, tours of the collections, and live animal demonstrations. If you’re in SoCal and you’re into herps–or have kids, grandkids, nephews or nieces that are into herps–it will be well worth checking out. While you’re there, don’t neglect the newly renovated Age of Dinosaurs and Age of Mammals halls, which are frankly phenomenal: spacious, well-lit, loads of actual material on display, skeletons you can walk all the way around, informative but unobtrusive signage, tasteful integration with existing architecture…I could go on. Better if you just go and see for yourself.

About that gator. First the bad news.  It came to the LACM from another collection, and has no data–no locality, no date collected, nothing. The skull is also missing all of its teeth, the left retroarticular process, the back end of the braincase and the occipital condyle. I think the latter losses were probably caused by a foramen of Winchester.*

Now, the awesome news. The length from the snout tip to the end of the articulars was 680mm and from the snout to the end of the quadrates was 590mm. Irritatingly I did not get a dorsal head length, which is the gold standard for comparative croc skull measurements, because I only reread Darren’s giant croc skull post after I got home last night. Going from the photos, I think the dorsal head length was right around 50 cm (beware, the yardstick in the photos is marked off in inches).

Darren’s post led me to this one, which has some very useful measurements (yay!) of giant croc skulls. The table at the end of that post lists alligator skulls with dorsal head lengths of 58, 60, and 64 cm, so the big LACM gator is nowhere near being the world’s largest. In fact, the 64 cm skull would be a quarter again as large, which is a truly horrifying thought. Still, it’s a big damn skull from a big damn gator.

You might get the impression that here in the Wedel lab we are shamelessly obsessed with giant saurians. And that is in fact true. But we also look at tiny ones, too. Here I’m playing with the skull of a little Tomistoma, the false gharial. Tomistoma is notable because another individual of the genus produced the longest skull of any known extant crocodilian–a whopping 84 cm dorsal head length (photos of this monster are in both of the giant croc skull posts linked above).

The moral of the story? If the sign says don’t go swimming, don’t go swimming. Go to RAAD instead, and see the giant alligator skull, and a ton of other cool stuff besides. And if you’re into gator skulls or just like geeking out on awesome anatomy, check out the 3D Alligator Skull site, a joint project of the Holliday lab and Witmer lab. Have fun!

* bullet hole

It’s been a little quiet around here lately. Mike has been slammed with day-job work, Darren is terminally busy as always, and I’m in my fall teaching block so I’ve been too busy to think. But life rolls on and there are announcements that need making. To wit:

- My post on the long nerves of sauropods was chosen as one of ten blog posts for the Science Writer Tip Jar at Not Exactly Rocket Science, back in May. Ed Yong, the NERS mastermind, has this to say:

Throughout the blogosphere, people produce fantastic writing for free. That’s great, but I believe that good writers should get paid for good work. To set an example, I choose ten pieces every month that were written for free and I donate £3 to the author. There are no formal criteria other than I found them unusually interesting, enjoyable and/or important.

It was an honor to be chosen; Ed’s a damn fine writer and has a knack for finding good stuff and pointing people to it. So why am I just blogging about this now, in August? I didn’t cover it at the time because the Science Writer Tip Jar runs on reader donations and I thought it would be a little gross to solicit money for myself. And I didn’t cover it right after because Ed’s been busy, too, and it sorta slipped off the radar for both of us. But at the end of last month he sent me a nice donation by PayPal, and I’m finally making good with the blogging about it.

What will I do with the dough? Inevitably, it will be spent on an epic meal of sushi for Mike and I. We don’t get to see each other very often, so when we do we have a sushipocalypse, and it’s pretty common for us to have ideas worth pursuing and publishing at these events. So ultimately the money will be plowed back into science, albeit indirectly. Thanks, Ed, and keep up the stellar work at NERS.

- Speaking of money, if you’d like to win a pile of it–4500 Euros, in fact–for the paleo paper you published in 2010, and get a nice trip to Spain in the bargain, I suggest you submit to Paleonturology 11, sponsored by Fundacion Dinopolis in Teruel, Spain. I know about this awesomeness because one of my papers won back in 2006, and I got a free trip to Spain in December, 2007 (story here). Winners have included papers by grad students and emeritus professors, on everything from trilobite eyes and bivalve shells to Pliocene hominids and dinosaur gastralia. The entrance form is super-simple and the whole process takes about as much time as it does to read this post. So if you published a paleo paper in the calendar year 2010 and you don’t enter, you’re just being silly. The deadline isn’t until November 15, but there’s no reason not to just sit down and do it right now. The form is somewhere on the Dinopolis website, but if your Spanish is as nonexistent as mine, you may find this PDF handy:  Paleonturology 11 entrance form

- This Friday, August 19, I’ll be on Jurassic CSI, talking about big sauropods. Details, showtimes, and some photos are here. The photo up top, of me with an Apatosaurus pelvis at BYU, is borrowed from there.

That’s all for now; further bulletins as events warrant.

Let’s look a bit more closely at the holotype element of Brontomerus mcintoshi, which as we all remember is the juvenile left ilium OMNH 66430.  Much of what we’ve said about Brontomerus is based on the shape of that ilium, so it’s important to get right.  Several commentators have expressed skepticism about how we reconstructed, so I thought it would be worth taking the time to explain why we put it together we way we did.

First, let’s orient ourselves.  Here is the torso from the skeletal inventory that was Figure 1 of the paper (Taylor et al. 2011, natch).  In this version, I’ve highlighted the ilium in red.  We’re looking at the left side of the animal, so the main part of the bone is further forward than the hip socket, towards the animal’s head.

As you’ll see from the area that we left shaded grey, a chunk is missing from the middle of the ilium, where it was damaged in the field.  As the figure of the ilium in the paper shows clearly, what we actually saw in the OMNH collection was three chunks of bone: a big one consisting of the acetacular margin, pubic and ischiadic peduncles and most of the preacetabular blade; and two smaller fragments, each contributing part of the dorsal or posterior margin.

We spent a while in the OMNH collection playing with the three chunks to see how they best fit together.  In doing this with the actual bones, we were able to take account of their curvature in the third dimension, which our figure don’t show — although a dorsal-view photo gives some idea.

Anyway, we this is what we came up with:

(Sorry if that image is getting a bit overfamiliar, but it’s worth seeing again in the context of this post.)

You’ll remember from the Clearing the Air post that Jim Kirkland, who excavated the ilium, felt that we’d got the two smaller fragments in the wrong places relative to the main chunk, and also that a fourth fragment which we’d missed also belongs to the ilium.  He kindly sent a photo of how he’d reconstructed the ilium, and I used the arrangement of pieces in the photo as the basis for a “what if” alternative reconstruction.

So far, this is old news.  But what was maybe not quite clear in the post is how very similar the two reconstructions really are.  Let’s fix that: here they are side by side, with ours on the left and Jim’s on the right:

It seems pretty clear that even if Jim’s arrangement is correct (which Rich Cifelli  disputes), that doesn’t affect the reconstruction in any significant way.

But the real question is why we put in that dotted line — and why we put it where we did.  How do we know there wasn’t a normal-sized postacetabular lobe sticking out behind?  This is what Jamie Headden wanted to know in an email to me shortly after the paper come out.  With his kind permission, I reproduce the illustration that he prepared, showing (A) the reconstruction from the paper, and (B) how it might have been different:

The reason we rejected a reconstruction like the one in Jaime’s part B is explained (too) briefly in the paper (pp. 80-81):

The postacetabular lobe is reduced almost to the point of absence [...]  The ischiadic peduncle is reduced to a very low ventral projection from almost the most posterior point of the ilium. The near absence of the ischiadic peduncle cannot be attributed to damage as the iliac articular surface is preserved. Immediately posterodorsal to this surface is a subtle notch between the peduncle and the very reduced postacetabular lobe. This notch and the areas either side of it are composed of finished bone, demonstrating that the great reduction of the postacetabular lobe, too, is a genuine osteological feature and not due to damage.

To my lasting annoyance, I didn’t take any posterior-view photos of the ilium back in 2007, so I can’t show you this finished bone as well as I’d like — this was back before I’d learned all my lessons on how to photograph bones.  But here is a close-up of the posterovental extremity of the ilium, again from Fig. 2, showing the notch: I have left the postacetacular lobe in colour, and desaturated the ischiadic peduncle — the notch is between them.

This next photograph of the ilium, again in lateral view, is lit rather differently from the one we used in the figure, so that you can see a distinct shadow lying along the valley between the ischiadic peduncle and what there is of the postacetabular blade.

Here’s one that shows the main chunk of the ilium in anteromedial view: from here, you can more easily see the the distinction between the ischial peduncle (which projects towards the camera) and the preserved, ventralmost, part of postacetacular blade, which is further back.

And one in posteroventral view: this is similar to our Fig. 2b, but from a slightly more posterior (and medial) perspective, so that you can more easily see the mediolaterally compressed posterior lobe sticking out behind the broader ischial peduncle at top right:

What all these photos unfortunately do not show is the finished nature of the bone on the posterior margin of the postacetacular blade — on that, you just have to take our word.

But the point is this: we have the whole of the ischiadic peduncle and the ventralmost part of the postacetacular blade — we know that the posteriormost preserved part of the main chunk of ilium is not part of the peduncle (so that the postacetabular blade is missing), but that this really is the blade itself.  And because the bone is not broken, we know that the trajectory of the posterior margin of the postacetabular blade was directed dorsally from the posterior point of the peduncle.

I hope that’s clear.  What I really should have done, of course, was take my own good advice and get photos from every angle — and, ideally, pairs that would have allowed me to show the relevant features as anaglyphs.

Anyway, all this shows that the shape of the ilium really was pretty much as we reconstructed it — and, most, importantly, that the bizarre proportions we reported in Table 4 are correct: preacetabular blade, measured parallel to the longest axis of the ilium equal to 55% of total length; postacetabular blade equal to 0%.

Exactly how strange is this almost non-existent postacetabular blade?  In the paper we described it as “remarkable”, but it’s not completely unprecedented.  Lehman and Coulson (2002:fig. 8) showed the left ilia of six somphospondylians:

As you can see, the Euhelopus zdanskyi and Saltasaurus loricatus ilia both lack postacetabular blades (although Powell 1992:fig. 18 suggests that the posterior portion of the Saltasaurus ilium may be broken).  Where Brontomerus is unique is in the combination of this postacetabular reduction with the enormous preacetabular blade.

All clear?  Good.

“But wait!”, I hear you cry.  “That ilium is juvenile!  How do you know that its strange shape is not a juvenile feature?”

Stay tuned!  All will be revealed.

References

When you last saw this rhea neck, I was squeezing a thin, unpleasant fluid out of its esophagus. Previous rhea dissection posts are here and here; you may also be interested in my ratite clearing house post.

We did that dissection back in 2006. Since then I finished my dissertation, got a tenure-track job, and moved twice. The rhea neck followed me, living in a succession of freezers until last spring.

Last spring I thawed it out, straightened it (it had been coiled up in a gallon ziploc), refroze it, and had it cut in half sagittally with a bandsaw. I did all of this for a project that is not yet ready to see the light of day, but there’s a ton of cool morphology here that I am at liberty to discuss, so let’s get on with it.

Throughout the post, click on the images for full resolution, unlabeled versions.

In the image above, you’ll notice that the saw cut was just slightly to the left of the midline, so that almost the entire spinal cord was left in the right half of the neck (the one toward the top of the image; the left half, below, is upside down, i.e. ventral is towards the top of the picture). The spinal cord is the prominent yell0w-white stripe running down the middle of the hemisectioned neck. It’s a useful landmark because it stands out so well. Dorsal to it are the neural arches, spines*, and zygapophyses of the vertebrae, and epaxial muscles; ventral to it are the vertebral centra and the hypaxial muscles.

* If you want to call them that–some of them are barely there!

Here’s the large supraspinous ligament (lig. elasticum interspinale), which is similar to the nuchal ligament of mammals but independently derived. Compare to the nuchal ligament of a horse (image borrowed from here):

Note how the actual profile of the neck is vastly different from what you’d suspect based on the skeleton alone. This is one of the reasons that necks lie. For more on the supraspinous ligament in rheas and its implications for sauropods, see Tsuihiji (2004) and Schwarz et al. (2007).

Birds also have very large interspinous ligaments (lig. elasticum interlaminare), each of which connects the neural spines of two adjacent vertebrae. In the above photo, the blunt probe is passing under (= lateral to) the unpaired, midline interspinous ligament. Rheas are unusual among birds in having such a large supraspinous ligament, and you can see that this interspinous ligament is almost as big. If you tear down the neck of a chicken or turkey, you will find huge interspinous ligaments, and the supraspinous ligament will be tiny if you can identify it at all.

Here’s something I don’t think we’ve ever shown before here on SV-POW!: a photograph of an actual pneumatic diverticulum. That’s the dark hole in the middle of the photo. You can see that we’re in the left half of the neck, lateral to the spinal cord, almost to the postzygapophysis, the articular surface of which is more lateral still (“below” or “deep to” the surface you see exposed in this cut). Usually at each intervertebral joint there is a connection between the lateral pneumatic diverticula that run up the side of the cervical column and pass through the cervical rib loops and the supramedullary diverticula that lie dorsal to the spinal cord inside the neural canal. That connecting diverticulum is the one exposed here.

NB: diverticulum is singular, diverticula is plural. There are no diverticulae or, heaven forbid, diverticuli, although these terms sometimes crop up in the technical literature, erroneously. (I hesitate to point this out, not because it’s not important, but because I’ll be lucky if I didn’t screw up a Latin term elsewhere in the post!)

Here are pneumatic diverticula in a transverse CT section of an ostrich neck (Wedel 2007b: fig. 6; compare to Wedel 2003: fig. 2, another slice from the same neck). In this view, bone is white, muscles and other soft tissues are gray, and air spaces are black. A, lateral diverticula running alongside the vertebral centra. B, air spaces inside the bone. C, supramedullary airways above the spinal cord. This section is close to the posterior end of a vertebra; the flat-bottomed wing-like processes sticking out to either side are the anterior portions of the postzygapophyses. If the slice was a few mm more posterior, we would see the prezygapophyses of the preceding vertebra in contact with them. Also, the vertical bars of bone connecting the centrum to the postzygs would pinch out, and we’d see the diverticula connecting the lateral (A) and supramedullary (C) airways–that’s the diverticulum revealed in the photo two images up.

Here’s another cool section showing a diverticulum and some muscles. Note the short interspinous muscles, which connect the neural spines of adjacent vertebrae. The probe indicates another open diverticulum, and the very tip of the probe is under one of the very thin layers of epithelium that line the diverticula. You can see that this diverticulum lies on the dorsal surface of the vertebra, posterior to the prezygapophysis and anterior to the neural spine. This supravertebral diverticulum is near and dear to my heart, because I have published an image of its traces before.

Lots going on in this photo (remember that you can click for an unlabeled version). This is a middle cervical vertebra of an emu, in anterodorsal view, with anterior towards the bottom of the picture. Bonus geek points if you recognized it as the basis for Text-fig. 9 in Wedel (2007a). I published this photo in that paper because it so nicely illustrates how variable the skeletal traces of pneumaticity can be, even from left to right in a single bone. On the right side of the photo (left side of the vertebra), the bone resorption adjacent to the supravertebral diverticulum produced a pneuamtic fossa, but one without distinct bony margins or a pneumatic foramen. On the other side, the fossa contains a pneumatic foramen which communicates with the internal air spaces, but the fossa is otherwise identical. Fossae like the one on the right are a real pain in the fossil record, because they might be pneumatic, but then again they might not be; such shallow, indistinct fossae can house other soft tissues, including cartilage and fat. This is what I was talking about when I wrote (Wedel 2009: p. 624):

If progressively more basal taxa are examined in the quest to find the origin of PSP [postcranial skeletal pneumaticity], the problem is not that evidence of PSP disappears entirely. It is that the shallow, unbounded fossae of basal dinosaurs are no longer diagnostic for pneumaticity.

For more on that problem, see Wedel (2007a) and the post, “X-Men Origins: Pneumaticity”.

The other labelled bits in the above photo are all muscle attachment points, and you may find Wedel and Sanders (2002), especially Fig. 2, a useful reference for the rest of the post. The dorsal tubercles, or epipophyses, are rugosities dorsal to the postzygapophyses that anchor most of the long, multi-segment epaxial muscles, which in birds are the M. longus colli dorsalis, which originates on the anterior faces of the neural spines, and M. ascendens cervicalis, which originates on the cervical rib loops. The crista transvers0-obliqua is a low, bony crest connecting each dorsal tubercle to the neural spine; it corresponds to the spino-postzygapophyseal lamina (SPOL) of sauropods (see Tutorial 4: Laminae!), and anchors the Mm. intercristales, a group of short muscles that span the cristae of adjacent vertebrae, like the Mm. interspinales only more lateral.

The carotid tubercles serve as points of origin for the M. longus colli ventralis, one of the largest and longest of the multi-segment hypaxial muscles; they have no obvious homolog or analog in sauropods. The lack of this feature might indicate that the hypaxial muscles were less of a big deal in sauropods, for whom lifting the neck was presumably a bigger problem than lowering it. Alternatively, the M. longus colli ventralis of sauropods might have attached to the medial sides of the parapophyses and the capitula of the cervical ribs, which tended to be larger and more ventrally-directed than in basal sauropodomorphs and theropods.

The unlabeled red arrows mark the lateral tubercles and crests of the cervical rib loop, to which we will return momentarily.

Here you can see a big bundle of long epaxial muscles, including both the M. longus colli dorsalis and M. ascendens cervicalis, inserting on the left dorsal tubercle of the vertebra on the right.  Note that the cut here is quite a bit lateral of the midline, and actually goes through the lateral wall of the neural canal in the vertebra on the right (that vert is the fifth back from the front of the section of neck featured in this post, which is incomplete). That is why you see the big, multi-segment muscles here, and not the shorter, single-segment muscles, which lie closer to the midline.

Here are some more muscle attachment points in a bird vertebra (a turkey this time, courtesy of Mike). The lateral crests and tubercles (tubecula ansae and cristae laterales, if you’re keeping track of the Latin) are the same bony features indicated by the red arrows in the photo of the emu vertebra up above. They anchor both the long M. ascendens cervicalis, which inserts on the dorsal tubercles of more anterior vertebrae, and the short Mm. intertransversarii, which span the cervical rib loops of adjacent vertebrae. Sauropods usually have at least small rugosities on their diapophyses and the tubercula of their cervical ribs (which articulate with the diapophyses) that probably anchored homologous muscles.

Here’s a dorsal tubercle above the postzyg on the neural arch of a juvenile Apatosaurus (cervical 6 of CM 555, shown in right lateral view). Notice that the spinopostzygapophyseal lamina (SPOL) and postzygodiapophyseal lamina (PODL) actually converge on the dorsal tubercle rather than on the postzyg. This is pretty common, and makes good mechanical sense.

Dorsal tubercles again, this time on the world’s most wonderful fossil, cervical 8 of the HM SII specimen of Giraffatitan brancai, in the collections of the Humbolt museum in Berlin. While you’re here, check out the pneumato-riffic sculpting on the lateral faces of the neural arch and spine, and the very rugose texture on the tip of the neural spine, SPOLs, and dorsal tubercles. In fact, compare the numerous pocket-like external fossae on this vertebra with the internal air cells exposed in the cross-sectioned rhea neck. I have argued here before that sauropod cervical vertebrae are pretty similar to those of birds; the main differences are that the cervical rib loops are proportionally much smaller in sauropods, and sauropod vertebrae mostly wore their pneumaticity on the outside.

Farther anteriorly in the neck–the three vertebrae pictured here are the third, fourth, and fifth (from right to left) in this partial neck–and somewhat closer to the midline. Now you can see some short epaxial muscles, probably Mm. intercristales and Mm. interspinales (the two groups grade into each other and are often not distinct), spanning adjacent vertebrae. As in several previous photos, the supravertebral diverticulum is visible, as well as the communicating diverticulum that connects the lateral diverticula to the supramedullary airways. I forgot to label them, but ventral to the centra you can see long, light-colored streaks running through the hypaxial muscles. These are the tendons of the M. longus colli ventralis, and in some of the previous photos you can see them running all the way to their origination points on the carotid tubercles. These extend posteriorly from the short cervical ribs of birds, and are homologous with the long cervical ribs of sauropods.

That’s all I have for this time. If you’d like to see all of this stuff for yourself, turkey necks are cheap and big enough to be easy to work with. Geese are good, too. You can see all the same bits in a chicken or a duck, it’s just harder because everything is smaller (if you’re a real glutton for punishment, try a Cornish game hen).

When I first started working on sauropods, their cervical vertebrae made no sense to me. They were just piles of seemingly random osteology. The first time I dissected a bird neck was an epiphany; ever since then, it is hard for me to look at sauropod vertebrae and not see them clad in the diverticula and muscles that shaped their morphology. Go have fun.

References

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