Things are pretty quiet at SV-POW! Towers: Matt’s on the road and can’t post, I’ve been working way too hard on day-job work and haven’t had much time for anything else, and Darren seems to have gone to ground (probably holed up somewhere with a stack of lissamphibian cladograms). Until the new year, then we give you the following lame picture:

Ornithopsis lectotype BMNH R28632

What we have here is one of the lamer sauropod type specimens: it’s BMNH R28632, the lectotype of the venerable Wealden “brachiosaurid” Ornithopsis hulkei Seeley 1870. I won’t blame anyone who can’t immediately see what it is: it’s a badly eroded dorsal centrum in left lateral view. Perhaps surprisingly, this genus was judged valid in Upchurch et al.’s (2004) survey of sauropods.
There’s a lot that could be said about this specimen, and maybe we’ll revisit it in the New Year, but right now I need to go and watch Sonic Underground Volume 2 with my boys, so for now you’ll have to content yourselves with the picture.

Happy new year!

Merry Christmas from SV-POW!

December 24, 2007

soaring-sauropod-500.jpg

The famous (infamous?) AMNH Barosaurus, from an angle you may not have seen before. There’s a very subtle problem here–both this skeleton (the “mommy”) and the juvenile hiding behind it (the “baby”) are reconstructed with 17 cervicals, although to the best of anyone’s knowledge, Barosaurus only had 16. Nitpicky? Sure. But to me, making an already ridiculously long-necked dinosaur even more outrageous by sneaking in an extra vertebra is–at the risk of offending the British 2/3 of the SV-POW! creative team–just not cricket.

Stay tuned during 2008–we’ll see if the three of us can keep this up for an entire calendar year.

Cheers,

Matt (and Mike and Darren)

Now that the Xenoposeidon frenzy is over, we seem to be settling down to about one SV-POW! post per week … which on the face of it is not too unreasonable for a blog with “of the week” in its title.

Continuing with our drive not to show you presacrals all the time, but completely failing in our drive not to show you Brachiosaurus all the time, I present this photo of a nearly complete tail of B. brancai that I took in the basement of the Humboldt Museum, Berlin, in March 2005:

Nearly complete tail of Brachiosaurus brancai

To my shame, I have to admit that I paid almost exactly no attention to the tail while I was there, for what seemed like a perfectly sensible reason: I was (and still am) working on another Tendaguru brachiosaur, and my specimen has no caudal vertebrae, so this tail was no use to me for comparative purposes. I know, I know, how dreadfully utilitarian. I don’t believe I’d make that mistake today.

Janensch (1950a) figured two nearly-complete caudal sequences of B. brancai, in plates II (specimen Fund Aa) and III (Fund D), and described these two plus a third, Fund no, in his description (p. 60). In a separate paper, Janensch (1950b:98) explains that the third tail skeleton, Fund no, was used for the skeletal mount in the public gallery, so the tail skeleton in the collections must be either Aa or D. Judging by eye it more closely resembles the elements in Plate III, so I guess it is Fund D. Don’t quote me on that, though. I must get back over there some day and check.

Actually there are lots of good reasons to return to Berlin now. The remount of the big brachiosaur skeleton is done, and it looks absolutely spectacular. (My thanks go to Gerhard Maier, who sent me a CD full of photos that he took of the new mount.) Also the collections are open again for the first time in a couple of years. Also, I am nowhere near as ignorant now as I was when I made my earlier visit. And, finally, there is a sushi restaurant just around the corner from the museum (why not?) which, foolishly, does an all-you-can-eat fixed-price deal. I don’t think I actually drove them out of business when I was there before. but it must have been a close-run thing.

7306 anterior half in section

Inspired by Mike’s recent post on the interior of Chondrosteosaurus from the Isle of Wight’s Wessex Formation, what could I do but weigh in yet again with one of my most-loved specimens: the beauty that is MIWG.7306 (aka ‘Angloposeidon’), a big brachiosaurid also from the Wessex Formation (Naish et al. 2004). As mentioned previously, it’s perhaps intuitively surprising that one of the most useful things about MIWG.7306 is that it’s broken in two, allowing us to see the broken faces of both halves of the vertebra. This allows us to see the internal structure of the specimen and, potentially, to work out, not just what the internal architecture was like, but also how pneumatic this beast was. To date Matt and I have done some preliminary work on this, but we have yet to publish anything, so what you’re getting here is a world first, never-before-seen by anyone outside.. well, me and Matt. In fact I can’t recall whether even Mike has seen this stuff: IT’S THAT SECRET.

Anyway, what we’re looking at here is the posterior broken face of the anterior half of MIWG.7306. The specimen was photographed lying on its side but I’ve reoriented the photo such that the dorsal surface is at the top, of course. The broken surface looks at first sight like a big mess, mostly obscured by sediment which has gotten preserved within the pneumatic spaces. However, it you look carefully you’ll see very dark (blackish) spars of bone scattered about the interior. These are the thin bony walls that surround the internal cavities, called camellae, that made up the vertebra’s interior. Much of the ventral part of the cross-section is taken up by the vertical median septum: much of the space lateral to the septum (on both its left and right sides) would have been occupied by large air sacs. I was hoping to use a fully labelled version of this photo but cleverly seem to have lost it (and don’t have time to knock up a new version). For the full details you’ll have to wait for the paper!

7306 section, ventral part

Ventral to the median septum, the vertebra is again wide when seen in cross-section, and in the photo here we’re looking at that ventral part, though this time we’re looking at the anterior face of the posterior half of the vertebra. What’s nice is that there are clearly at least four distinct camellae aligned along the centrum’s ventral edge, and they don’t appear to be equal in size (nor arranged symmetrically around the midline). The actual ventral floor of the centrum can also be clearly seen in cross-section, and it’s pretty thin. All of this is particularly interesting because we have comparative data from North American brachiosaurids (in particular from a specimen that Matt has scanned, BYU 12866) and from Sauroposeidon (Wedel et al. 2000a, b). ‘Angloposeidon’ is similar enough to both of these in its details to convince us that the same sort of thing is going on, but it’s also different in various subtle ways: the ventral floor of the centrum is not the same thickness in all of these animals for example.

In the article on Chondrosteosaurus, Mike noted that we can work out how much of a vertebra’s interior was occupied by air if we can calculate the bone : air space ratio. We did just this with MIWG.7306, using the photos shown here and several others. The result: MIWG.7306 approached Sauroposeidon in terms of its pneumaticity, being 80-90% air. This gives us some remarkable and significant data on the palaeobiology of this animal, as pneumaticity has all sorts of implications for the animal’s respiration, physiology and mass (Wedel 2003, 2005). And on that note, I shall say goodbye.

References

apato-growth-series-500.jpg

My favorite room in the world is the big bone room at BYU’s Earth Science Museum. It is the only place on the planet that has good material of all six of the best-known Morrison sauropods: Apatosaurus, Barosaurus, Brachiosaurus, Camarasaurus, Diplodocus, and Haplocanthosaurus. So if you are looking at, say, a middle cervical of Apatosaurus and you think, “Hmm, I wonder how this looks in X,” where X is one of the other five genera listed above, you can just go look. It’s phenomenal.

The big vert here is a posterior cervical of Apatosaurus. Those big loops on the side are formed by the diapophyses and parapophyses (sticking out from the vertebra) and the capitula and tubercula of the cervical ribs. Capitula are rib heads, and they articulate with the parapophyses, which are the lower of the two sets of rib articulations on the vertebral centrum. Tubercula are rib tubercles, and they articulate with the diapophyses, which are at the ends of the massive transverse processes sticking out sideways from the neural arch. Here’s a labeled version, just in case the verbal description made no sense. I know Mike covered this stuff back in Tutorial 2, but Apatosaurus is frankly pretty freaky in the cervical rib department.

apato-growth-labeled-500.png

You’ll notice that the neural spine is split down the middle, which is the case in many diplodocoids but not all of them. Bifurcated neural spines are also found in Camarasaurus, some titanosaurs, and to a lesser extent in some mamenchisaurs, so the character definitely evolved more than once. More about bifid neural spines another day…

At last, to the point. In front of the big vert you can see a smaller one, about the size of a fist. That’s a vertebral centrum from the same part of the neck from a much smaller individual of Apatosaurus, probably somewhere between horse- and elephant-size. And that’s not all–in front of the scale bar, wrapped up in plastic, is a centrum from a wee little baby Apatosaurus about the size of poodle. Why is the vert in plastic? Because it was going off to the micro-CT scanner at the University of Utah, which is in a cleanroom, so all specimens have to be hermetically sealed. I didn’t think to shoot this little growth series lineup until the vert was already bagged, and I haven’t been back since to set it up again.

Alas, the baby Apatosaurus vert and the CTs of its internal structure will also have to wait for another day. We’re such teases…

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