Invading the postzyg

March 30, 2008

7306-fossa-medial-side-postzyg-resized.jpg

Again, another exclusive peek at an interesting specimen: the MIWG.7306 vertebra, aka ‘Angloposeidon’ (Naish et al. 2004). Apologies if, by now, you’re bored of my show-casing of this specimen, but – not only is it the only sauropod vertebra of which I personally have multiple unpublished images – it is also a really nice demonstration of the fact that, even in just a single vertebra, there are multiple interesting, bizarre, and sometimes under-studied or even un-studied details.

What we’re looking at here is the medial (‘inside’) surface of the left postzygapophysis, with the centrum down below the bottom of the image, and the cotyle off to the left (the opposite side of what’s shown here). The image below should help with orientation. The focus of interest is the unusual matrix-filled space in the middle of the image: just what is it? Because it has sharp, clean edges, I am pretty convinced that it’s natural, and I assume it’s a pneumatic foramen. Similar structures are present on the medial side of the right postzygapophysis, and are different in position and shape (Naish et al. 2003, p. 790). We think, based on several lines of evidence, that the space between the postzygapophyses (limited anteriorly by the neural spine) was occupied by an air-sac (Schwarz & Fritsch (2006) called this the interspinal diverticulum), so is this evidence that diverticula from the interspinal air-sac invaded the bodies of the postzygapophyses on their medial sides? If so, was this just a one-off in MIWG.7306, or was it widespread in brachiosaurs, in macronarians, in neosauropods, or even in sauropods as a whole? I admit that I haven’t yet taken the time to check properly, but the big problem is that this part of the vertebra – the medial surface of the postzygapophysis – is rarely figured. Based on what has been published, I have yet to see a similar structure, even in Brachiosaurus (which is very well figured, as sauropods go).

miwg7306-prezyg-fossa-composite-resized.jpg

I’m sure that someone is now going to make me look very, very silly. But, whatever. I can’t pretend to know everything. Note that, again, this is a world first. Yes, all of this stuff should be published… and in time in will, in time.

References

  • Naish, D., Martill, D. M., Cooper, D. & Stevens, K. A. 2004. Europe’s largest dinosaur? A giant brachiosaurid cervical vertebra from the Wessex Formation (Early Cretaceous) of southern England. Cretaceous Research 25, 787-795.
  • Schwarz, D. & Fritsch, G. 2006. Pneumatic structures in the cervical vertebrae of the Late Jurassic Tendaguru sauropods Brachiosaurus brancai and Dicraeosaurus. Eclogae geol. Helv. 99, 65-78.
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4 Responses to “Invading the postzyg”

  1. Graham King Says:

    Wow. (Thanks for these exclusive pics on SVPOW.)

    “Air sacs, air sacs, everywhere/And scarce a drop of bone [left uninvaded]“…

    …Can I suggest colloquially dubbing the oh-so-pneumatic sauropods ‘the balloon animals’?

    Science and art may be converging on this… I have recently been thinking how to parade a scaled sauropod around town, and reckon a lightweight articulated plastic tube skeleton fleshed out with inflatables (using helium maybe in neck and tail?) would be a viable design and a manageable way to go.


  2. Can I suggest colloquially dubbing the oh-so-pneumatic sauropods ‘the balloon animals’?

    Well, they’d have to be the holey balloon animals…


  3. [...] flagrant playing-to-the-gallery “showdown” and Darren’s observation of a newly recognised site of pneumaticity (which I want to cite in a paper but won’t be allowed [...]


  4. [...] we should have cited that post as a source. Oh well. We do cite one SV-POW! post: Darren’s Invading the postzyg, which at the time of writing is the only published-in-any-sense source for pneumaticity invading [...]


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