Sauropod Vertebra Picture of the Week

What if I told you that when Matt was in BYU collections a while ago, he stumbled across a cervical vertebra — one labelled DM/90 CVR 3+4, say — that looked like this in anterior view?

I think you would say something like “That looks like a Camarasaurus cervical, resembling as it does those illustrated in the beautiful plates of Osborn and Mook (1921)”. And then you might show me, for example, the left half of Plate LXII:

And then you might think to yourself that, within its fleshy envelope, this vertebra might have looked a bit like this, in a roughly circular neck:

Reasonable enough, right?

But when what if I then told you that in fact the vertebra was twice this wide relative to its height, and looked like this?

I’m guessing you might say “I don’t believe this is real. You must have produced it by stretching the real photo”. To which I would reply “No no, hypothetical interlocutor, the opposite is the case! I squashed the real photo — this one — to produce the more credible-seeming one at the top of the post”.

You would then demand to see proper photographic evidence, and I would respond by posting these three images (which Matt supplied from his 2019 BYU visit):

BYU specimen DM/90 CVR 3+4, cervical vertebra of ?Camarasaurus in anterior view. This is the photo from which the illustration above was extracted.

The same specimen in anteroventral view.

The same specimen in something approaching ventral view.

So what’s going on here? My first thought was that this speicmen has to have been dorsoventrally crushed — that this can’t be the true shape.

And yet … counterpoint: the processes don’t look crushed: check out the really nice 3d preservation of the neural spine metapophyses, the prezygs, the transverse processes, the nice, rounded parapophyseal rami, and even the ventral aspect of the centrum. This vertebra is actually in pretty good condition.

So is this real? Is this the vertebra more or less as it was in life? And if so, does that mean that the flesh envelope looked like this?

Look, I’m not saying it isn’t ridiculous; I’m just saying this seems to be more or less where the evidence is pointing. We’ve made a big deal about how the necks of apatosaurines were more or less triangular in cross-section, rather than round as has often been assumed; perhaps we need to start thinking about whether some camarasaur necks were squashed ovals in cross section?

Part of what’s crazy here is that this makes no mechanical sense. A cantilevered structure, such as a sauropod neck, needs to be tall rather than wide in order to attain good mechanical advantage that can take the stress imposed by the neck’s weight. A broad neck is silly: it adds mass that needs to be carried without providing high anchors for the tension members. Yet this is what we see. Evolution doesn’t always do what we would expect it to do — and it goes off the rails when sexual selection comes into play. Maybe female camarasaurus were just really into wide-necked males?

Final note: I have been playing fast and loose with the genus name Camarasaurus and the broader, vaguer term camarasaur. Matt and I have long felt (without having made any real attempt to justify this feeling) that Camarasaurus is way over-lumped, and probably contains multiple rather different animals. Maybe there is a flat-necked species in among them?

(Or maybe it’s just crushing.)