I floated this idea on Fist Full of Podcasts, and Andrew Stuck gave it a shout-out in the comments, so I’m promoting it to a post.
The idea, briefly, is that sauropods grew fast and had enormous energy demands and even though horsetails and pine needles are surprisingly nutritious (Hummel et al. 2008), they probably suck to eat all the time. Extant herbivores are notoriously carnivorous when no-one is looking, and it’s silly to assume that extinct ones were any different. It seems likely that a big, hungry sauropod, gifted by natural selection with more selfish opportunism than compassion, would probably have viewed a turtle as a quick shot of protein and calcium, and a welcome hors d’oeuvre before stripping yet another conifer or tree fern. Furthermore, said sauropod would have been well-equipped to render the unfortunate chelonian into bite-size chunks, as shown above. The first time might even have been accidental. (Yeah, sure, Shunosaurus, I believe you. [rolls eyes])
Given that sauropods and turtles coexisted over most of the globe for most of the Mesozoic, I’ll bet this happened all the time. I don’t know how to falsify that,* but how could it not have? You’d have to assume that sauropods didn’t run into turtles, or that their mercy outweighed their curiosity and hunger. That’s even more bonkers than turtle nachos.** As Sherlock Holmes almost said, “When you have eliminated the impossible, whatever remains – no matter how stupid/awesome – was probably done by sauropods.”
* “Oh, you found a boatload of turtle shell pieces at your fossil site? How tantalizingly unprecedented – please tell me more!” said no-one ever. Seriously, everyone who works on stuff younger than the Early Jurassic seems to bitch about all of the turtle frags they find, whether they’re looking for Apatosaurus or Australopithecus.
** Not to be all navel-gazey, but that is conservatively the greatest sentence I have ever written.
In conclusion, sauropods stomped on turtles and ate them, because duh. Fight me.
Further Reading
For more sauropods stomping, see:
- Genesis of an instant palaeo-art classic
- Sauropods stomping theropods: a much neglected theme in palaeo-art
- Sauropods stomping theropods, redux
- Greatest. Palaeoart. Ever.
- Brian Engh: Stomp time!
- Sauropods stomping theropods: Bryan Riolo’s Chaos Gigantes
- Greatest. Video. Ever. Starring sauropod-on-theropod violence!
And for sauropods not eating, but gettin’ et:
- Oblivious sauropods being eaten
- Oblivious sauropods being eaten, part 2: Bakker’s snoozing brontosaur
Reference
What I did on my holidays
September 25, 2009
I made brachiosaur sand-sculptures.

Brachiosaurid in hypothetical sleep posture, left anteroventrolateral view. Juvenile Homo sapiens (Daniel Taylor) for scale.
(And yes, it’s that Daniel Taylor, the author of Taylor 2005 — a copy of which apparently hangs on the wall of the Padian Lab.)
But wait! Is the brachiosaur truly asleep, as it seems, or is it actually the victim of a mighty hunter?

Brachiosaurid in hypothetical death pose, left posteroventrolateral view. Mighty hunter (Michael P. Taylor) for scale. Note bemused bystander in middle distance.
No, it turns out it was just asleep after all; and I joined it.

Brachiosaurid in hypothetical sleep pose after all, left posteroventrolateral view. Brachiosaur's new best friend for scale.
… and finally: your obligatory sauropod-vertebra shot:

Cast of Mamenchisaurus hochuanensis holotype CCG V 20401, in right lateral view. Need I draw your attention to the truly absurd neck? This cast is owned by the Homogea Museum in Trzic, Slovenia, and was on loan in the car-park of the Geological Museum in Copenhagen.
References
Jurassic roadkill: OMNH 4167
November 12, 2008
I’m worried that you might be getting spoiled, only getting to see perfect beautiful vertebrae, so I’m gonna show you some uglies now and then just to keep the universe in balance.
As uglies go, this one ain’t bad. It’s clearly a cervical, probably from Camarasaurus, given how far the prezyg overhangs the front of the centrum. As I recall, the internal structure on this one is pretty gorgeous, which illustrates a paradox that Kent Sanders and I discovered: many times the verts that are ugliest on the outside have the most beautiful internal structures, whereas verts that look nice on the outside are sometimes unreadable mush within.
Or rather, the internal structure of this vert would illustrate that paradox, if I could show it to you. But nice as it was, this was never one of my worth-publishing-on specimens, and although I know the CTs are around here somewhere, I can’t pinpoint their location right now. It’s a Heisenberg thing.
Until next time…