Terrifying hypothetical cervical vertebrae of the Morrison Formation
February 13, 2013
In our PeerJ neck-anatomy paper, we speculated on how long individual cervical vertebrae might have grown. Here is the relevant section:
Mere isometric scaling would of course suffice for larger animals to have longer necks, but Parrish (2006, p. 213) found a stronger result: that neck length is positively allometric with respect to body size in sauropods, varying with torso length to the power 1.35. This suggests that the necks of super-giant sauropods may have been even longer than imagined: Carpenter (2006, p. 133) estimated the neck length of the apocryphal giant Amphicoelias fragillimus Cope, 1878 as 16.75 m, 2.21 times the length of 7.5 m used for Diplodocus, but if Parrish’s allometric curve pertained then the true value would have been 2.21^1.35 = 2.92 times as long as the neck of Diplodocus, or 21.9 m; and the longest single vertebra would have been 187 cm long.
Now this speculation is shot through with uncertainty. As we’ve discussed before, at length, all estimates of Amphicoelias fragillimus length and mass are wildly speculative; and Parrish’s allometry result was extrapolated from an unconvincingly small data set. But still, these numbers are probably the best we can do with what we have.
In Diplodocus carnegii, C14 is the longest individual vertebra at 642 mm long (Hatcher 1901, p. 38). The Amphicoelias:Diplodocus size ratio of 2.21 from Carpenter and the neck allometry constant of 1.35 from Parrish suggest that the corresponding vertebra in the big boy would have been 2.92 times as long as that 642 mm, hence the 187 cm that we reported.
So what does a 187-cm long cervical vertebra look like? Scaling up from the Diplodocus carnegii C14 in Hatcher (1901: plate III) and using my good self as a scalebar, here it is:
I find that just a little bit frightening. In more ways than one.
References
- Carpenter, Kenneth. 2006 Biggest of the big: a critical re-evaluation of the mega-sauropod Amphicoelias fragillimus (Cope, 1878). New Mexico Museum of Natural History and Science Bulletin 36:131.
- Cope, Edward D. 1878. Geology and paleontology: a new species of Amphicoelias. The American Naturalist 12:563.
- Hatcher, Jonathan B. 1901. Diplodocus (Marsh): its osteology, taxonomy and probable habits, with a restoration of the skeleton. Memoirs of the Carnegie Museum 1:1-63 and plates I-XIII.
- Parrish, J. Michael. 2006. The origins of high browsing and the effects of phylogeny and scaling on neck length in sauropodomorphs. pp 201-224 in: Amniote paleobiology, University of Chicago Press, Chicago.
Sauropod Vertebra Picture of the Week 
February 13, 2013 at 1:05 pm
Watch out! That vertebra is about to eat you!
February 13, 2013 at 2:31 pm
Nice pose!
February 13, 2013 at 4:24 pm
One of course wonders if the height and other proportions are as constrained. Must read Parrish on this, but off hand can you say if they only constrain length between neck and dorsal vertebrae, or do they perhaps provide variables for other proportions.
February 13, 2013 at 4:27 pm
Yes, I wondered about this too. I don’t know of any data looking into this — it would be interesting to see. But in purely mechanical terms what one might expect is for longer vertebrae to also be taller and broader, and more pneumatic, as the bone is pushed outwards more from the center of the neck. In light of that, and having no other data, I elected to keep the Diplodocus vertebra’s proportions the same rather than plucking an aspect-ratio fudge factor out of thin air.
February 13, 2013 at 5:56 pm
Personally, I expect the trend we see in titanosauriforms to be true in diplodocoids: That the vertebra becomes longer, but not necessarily taller. It would be nice to compare, say, “short-necked” “brachiosaurs” with the longer-necked taxa, correcting for vertebral counts. Comparing cervical elongation to increased numbers, under the premise that shorter counts in long necks result in long vertebrae, while greater counters result in shorter vertebrae. This might have been done for birds: compare parrot necks, various anseriforms, etc.
February 13, 2013 at 8:13 pm
“The trend we see in titanosauriforms … That the vertebra becomes longer, but not necessarily taller.”
Can you substantiate that? Offhand, I can’t think what specimens you’d be using.
February 13, 2013 at 8:51 pm
Camarasaurus spp. -> Brachiosaurus/Giraffatitan -> Erketu ellisoni. Apatosaurus spp. -> Diplodocus spp. might represent another similar trend, as with Rapetosaurus -> Isisaurus, only in reverse.
February 13, 2013 at 8:54 pm
But Erketu is much smaller than Giraffatitan, and Diplodocus is no bigger than Apatosaurus. They don’t corroborate your hypothesis at all. The reverse, if anything, in the first case.
February 13, 2013 at 9:07 pm
Ah. I was confused on my trajectory there. I was reasoning that evolution toward longer necks doesn’t follow perfect trajectories: rather, vertebrae may trend to shorter vertebrae. It may actually be Europasaurus holgeri that suggests that size in basal titanosauriforms has a direct reation to vertebral length. Anterior vertebrae in the neck are relatively shorter than in comparable vertebrae in Giraffatitan brancai, which are in turn (?) shorter than in Sauroposeidon proteles. Then again, there may not be much of a pattern, though I think we’d all like to see if the biomechanical loading analyses of vertebrae and their relation to posture (or, at least I would).
February 14, 2013 at 2:41 am
Holy-moly that doesn’t seem physically possible. 0_0
Has anyone worked out a hypothetical upper limit to cervical vertebra?
I know we are always finding things that boggle the mind, but physics can only be taunted so much.
Still, it would be wicked sweet.
February 14, 2013 at 4:30 am
I was going to ask the same Q as Jaime. (No data, only
wildmoderate speculation), while the overall height of the vertebrae might scale to the same degree as length, I feel that perhaps the cross-sectional area of the centrum would not. I would also expect the degree of pneumatic “sculpting” to be greater.Still, that is certainly one sexy image to contemplate. That large vertebra in the background is not too bad either.
February 14, 2013 at 9:30 am
“Has anyone worked out a hypothetical upper limit to cervical vertebra?”
No, and I don’t think anyone ever will. Working out the mechanical properties of complex biological systems is incredibly complicated, and of course exacerbated by our knowing so very, very little about the non-bony components of the neck. It’s well worth skimming Jen Bright’s work on FEA-modelling the skull of a pig, especially figure 2 which shows that both FEA models were wildly wrong.
February 14, 2013 at 10:31 am
Mike, you need to make the Mike Taylor Smouldering Recline Scale Unit a standard of SV:POW and conference presentations. Your female readership will go through the roof.
Also, cool post. I feel an empathy for estimating long neck lengths with little data. On the aspect ratio issue, would it be possible to work a regressions of vertebral height and width along with length? My gut tells me that height and width will be relatively constant in each part of the vertebral column, mind, while length may be less constrained (at least in the neck). I’ve been pondering very similar issues with pterosaur cervicals recently, and may be trying to put some numbers to these thoughts very soon.
February 14, 2013 at 11:33 am
If I remember, I will use an MTSRSU silhouette as the scalebar in my next paper. It will follow in the honourable tradition of Bloke Walking Dog in the Brachiosaurus reconstruction, Bloke In Office Chair in the Brontomerus reconstruction and Bloke On Bike in the new paper’s animals-with-long-necks composite.
February 14, 2013 at 1:08 pm
[…] 13-2-2013: Terrifying hypothetical cervical vertebrae of the Morrison Formation […]
February 16, 2013 at 11:10 pm
Thanks!
I figured it was one of those things that would be nigh impossible.
I’m actually kind of surprised that no one has ever attempted to throw out a wild figure. Like the attempts to set a maximum size for animals in general.
Very cool paper and thanks again for the link!
February 16, 2013 at 11:38 pm
Hokkannen (1986) made what may well still be the most recent attempt to set absolute limits on land-animal body size. You can read it at http://www.miketaylor.org.uk/dino/hokkanen/Size-Hokkanen.pdf
February 17, 2013 at 6:30 am
The size of said vert becomes even more frightening when we consider than the 2.2 scaling factor is probably wrong. Last time I checked Diplodocus c.. did not have a D10 1.22 meters tall. If we instead go by femur length, Amphicoelias seems to be 4.6/~1.5=3 times larger. So vertebra lengths approaching 2.5 meters seem possible. Please correct me if anything seems grossly incorrect.
February 17, 2013 at 8:54 am
Well, we don’t know the femur length in Amphicoelias. We know almost nothing about its dimensions. Everything we “know” about it is extrapolated from a single partial neural arch, which was lost or destroyed. As we’ve noted elsewhere, everything we say about it has to be hedged about with multiple layers of uncertainty.
February 17, 2013 at 1:38 pm
[…] you found the hypothetical Amphicoelias fragillimus cervical in a recent post a bit too much to swallow, I won’t blame you. But how big do we know Morrison diplodocoid […]
April 11, 2013 at 4:56 pm
According to studies by John Whitlock, 2010, Amphicoelias should be more like Limaysaurus, which Diplodocus. It will be possible to estimate the true size of the animal, so we estimate it Allometric? I think so isometric scaling we are inflating too. Well, this is my opinion.