The heart of the matter

March 12, 2008

It’s a lonely night here at the Fortress of Sauropoditude. Darren is off at one of his numerous conferences, and Mike is in hiding, trying to avoid the reality that 4% of a millennium has passed since he was loosed upon the world. I gave the serfs the night off, which means it’s just me here in this lonely tower, surrounded by arcane devices, mouldering tomes and piles of ancient bones. The candles are lit, the wine is open on the sideboard, and I am in quest of something appropriately baroque for our evening’s contemplation. How about…a vertebra with no outsides?

iow-cut-section-500.jpg

Here is a sauropod specimen with no external morphology whatsoever. This is a cut and polished section of a fragmentary vertebra from the Isle of Wight. The black lines are bony septa that make up the internal structure of the vertebra. The brownish gray stuff between the septa is matrix (rock) filling the air spaces.

How much can we infer about the animal whose mortal remains these are, in the utter absence of soft tissue or external form?

The first thing that we note is that the vertebra has a complex internal structure, one that is highly subdivided into lots of irregular cavities. Complex internal structures are present in the vertebrae of mamenchisaurs, diplodocids, and most titanosauriforms, so we know that this chunk is not from a cetiosaur or dicraeosaur or camarasaur. It is from Early Cretaceous rocks from England, so we can provisionally rule out mamenchisaurs as possible donors. Diplodocids are represented in the Early Cretaceous of England by perhaps one bone or perhaps none at all. However, titanosauriforms were all over the place in the Early Cretaceous in the Northern Hemisphere generally, and in England particularly, and on the Isle of Wight especially. So we might guess that this is a chunk of a titanosauriform.

We should also pay attention to the size of the specimen: the vertebra of which it was a part was somewhat more than 15 cm in diameter, and may have been much larger. Now, 15 cm is not huge, but it means that is not from a very small sauropod like Europasaurus. And it is another line of evidence against a dicraeosaurid or rebbachisaurid identification.

Finally, we might be curious about the ratio of bone to air space. As frequent commenter Mike From Ottawa noted of another pneumatic vertebra, “There’s almost nothing but nothing there.” In fact, the plane exposed here is about 85% space and only 15% bone, which puts it up into “Angloposeidon”-Sauroposeidon territory. Most pneumatic sauropod vertebrae were about 60% air by volume, which is remarkable enough when you stop and think about it.

So based on qualitative (complex) and quantitative (85% air) assessments of its form, and given its size and stratigraphic and geographic context, my best guess is that this is a chunk of “Angloposeidon” or a closely related brachiosaurid. I can’t rule out the possibility that it belongs to a titanosaur or a weird giant rebbachisaurid or something even more unlikely, but that’s not where the balance of the evidence points.

Which, I think, is not too bad for a skinless piece of crap shard of excellence* that most people wouldn’t look at twice.

Well, thanks for your company. Mind the stairs on your way down, and if the side door in the hall is open, walk by quickly and don’t look inside. With any luck, one of my compatriots will be back here to greet you next week.

*That’s what small chunks of sauropods are called. Honest!

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12 Responses to “The heart of the matter”

  1. Dave Hone Says:

    “Mike is in hiding, trying to avoid the reality that 4% of a millennium has passed since he was loosed upon the world”.

    Mike is 250! Man, I knew his hair was greying, but he’s doing well.

  2. Matt Wedel Says:

    Um, 4% = 0.04, and 0.04 x 1000 = 40, which is how old Mike is now. Although I agree that he looks like he might be 250. On a good day.

    Anyway, you’d better let someone else found “Ask a Mathematician”. :-)

  3. Nathan Myers Says:

    If zoologists could count, snakes wouldn’t be tetrapods.

  4. Dave Hone Says:

    Oooooooops. For soem reason I thought Mike was much younger and managed to do soem bizarre mental gymnastics of ‘%’, ‘100’ ’25’ and ‘4’. You can guess where this went….

  5. Mike from Ottawa Says:

    My first thought on seeing the pic was that you guys had run out of sauropod vertebrae and had branched out into ankylosaur tail clubs. Would it be rude here at SVPOW! to ask if the ankylosaur tail clubs were dermal bone or an outgrowth of the tail vertebrae?

    It would be really cool to see one of these pneumatic vertebrae reproduced in a translucent plastic. Rapid prototyping from a CT scan could do that. Has anyone done it?

    “If zoologists could count, snakes wouldn’t be tetrapods.”

    I like that. Is it attributed to someone, floating in about generally or your own invention, Nathan?

  6. Graham Peter King Says:

    Nice one, Matt!

    (see I thought I’d post a short comment for once. just to show I can ;-) )

    graham

  7. Nathan Myers Says:

    Mike: It kind of evolved over on TetZoo. The longer expressions involved birds (2 is almost 4) leading to snakes (0 is approximately 4).

  8. Nathan Myers Says:

    … and when people make fun of snakes as tetrapods, the expression is, “If zoologists could count, they would do something else that pays better.”

  9. Amanda Says:

    This might be a stupid question (I don’t really believe that there are no such things as stupid quetions) but do you find that sauropod vertebrae are more highly pneumatic in larger sauropods?

  10. Matt Wedel Says:

    Would it be rude here at SVPOW! to ask if the ankylosaur tail clubs were dermal bone or an outgrowth of the tail vertebrae?

    As far as I know they were a bit of both, but the scales definitely tipped in the direction of dermal bone. IIRC, the tail club of Shunosaurus is composed of swollen vertebrae. But then the club of Shunosaurus is not a club the way the club of Euoplocephalus was a club. If the latter were a sledgehammer, the former would be one of those little four-inch novelty hammers you find here and there.

    On the other hand, that little hammer was being swung by a longer arm. I wouldn’t want any of that, not even if I was Gasosaurus

    It would be really cool to see one of these pneumatic vertebrae reproduced in a translucent plastic. Rapid prototyping from a CT scan could do that. Has anyone done it?

    Not to my knowledge. I wish, though. DROOL.

    This might be a stupid question (I don’t really believe that there are no such things as stupid quetions) but do you find that sauropod vertebrae are more highly pneumatic in larger sauropods?

    I also am a firm believer in the reality of stupid questions, but this ain’t one of them. It’s one I’ve been wrestling with for a while. And originally I wrote a multi-page comment about it, and then I realized that I was just stealing post material from myself, so I’m going to answer it in an upcoming post. Promise. Stay tuned.

  11. Amanda Says:

    Cool! Thanks!


  12. […] mean for all of them, including Sauroposeidon, ‘Angloposeidon’, some shards of excellence from the Isle of Wight, and assorted odds and ends, is something like 0.75-0.80, higher even than […]


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