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Re: sauropod killers



> > Correct me if I'm wrong, but hasn't there been some
> > YPM _Deinonychus_ quarry
> > fossil matrial associated with _Tenontosaurus_?

Yup. That association is discussed by Maxwell and Ostrom (1995). 
Associated remains of Deinonychus and Tenontosaurus have also been found
at OMNH locality V706 in the Antlers Fm., as discussed by Brinkman et
al. (1998) [refs at end of post].  OMNH crews have recovered several
individuals of Tenontosaurus from that locality, and the majority of
tenontosaurs have isolated Deinonychus teeth associated with them. We
have found Deinonychus teeth with the Tenontosaurus material in the
field, and also in the Tenontosaurus jackets while preparing them back
at the lab. Natural History recently had a cover article on Deinonychus,
written by Des Maxwell, discussing all of this and more.

> As an aside, I'm intrigued by the notion that some
> theropods may have eaten by stealing bites out of live
> sauropods rather than killing, then eating them, a
> daunting proposition to be sure when your prey laughs
> at an elephant's small size.  Has anyone proposed
> this?

Paul (1998) proposed this after seeing a documentary in which false
orcas nipped bites out of sperm whales. The sperm whales did not die
during the course of documentary, although their long-term survival was
not reported. Given that a lot of whales evidently have healed scars on
their fins and flanks, they certainly might have survived. However, I
have some problems with attributing this behavior to theropods, at least
as a significant component of their caloric intake.
1) I imagine that sepsis and infection would probably be worse for a
terrestrial animal wounded in this fashion (just an assumption, please
correct me if I err).  While this might lead to the sauropod's death,
thus providing the theropod with a meal, that strategy is not the same
as the "meals on feet" idea as proposed by Paul (1998). I have a hard
time believing that sauropods were losing enough flesh to support the
local theropod populations without either succumbing entirely, on an
individual basis, or evolving some kind of counter behavior in which
they actually notice that the theropod is about to take a bite of them
and proceed to do something about it.
2) Although encounters such as the one in the documentary do happen, I
would be surprised if they happened often enough for live sperm whale
chunks to provide a false orca pod with its primary source of food.
Again, this is merely the argument from personal incredulity. Perhaps
someone out there has data on this?
3) I don't know of any large terrestrial animal that prefers to take
single bites out of a living prey animal that is then allowed to escape,
rather than finding a young, old, sick, or weak individual and whacking
it.
4) I haven't been able to get my hands on Chiappe et al. (1999), on
sauropod nest sites in Patagonia. However, in his talk at SVP last year,
Chiappe suggested that survivorship for sauropods was low, maybe 1 in
500 if I remember correctly. That would give sauropods a very
juvenile-heavy population structure, which is not too surprising. Given
that there were probably tons of tiny sauropods running (or at least
ambling) around, and that the adult sauropods outweighed their largest
predators by a factor of 10 (roughly), going after the juveniles would
be the safer bet. And if a theropod was driven to go after an adult, an
option that probably put the theropod in mortal danger, why not go for
the gold and try to kill the thing? IMHO, dashing in to nip off a single
bite seems like a heck of big risk for a tiny payoff.

So, there's my two cents. Unfortunately, in the absence of data this is
all sheerest sophistry, or as the men on the lower decks say, pure B.S.
Let me know whach'all think.

Matt Wedel
Oklahoma Museum of Natural History
2401 Chautauqua Ave.
Norman, OK 73072
sauropod@ou.edu

Brinkman, D.L., Cifelli, R.L, and Czaplewski, N.J. 1998. First
occurrence of Deinonychus antirrhopus (Dinosauria: Theropoda) from the
Antlers Formation (Lower Cretaceous: Aptian-Albian) of Oklahoma.
Oklahoma Geological Survey, Bulletin 146, 27 pp.

Chiappe, L.M., et al. 1999. Sauropod dinosaur embryos from the Late
Cretaceous of Patagonia. Nature 396 [sorry, lost the page numbers]

Maxwell, W.D., and Ostrom, J.H. 1995. Taphonomy and paleobiological
implications of Tenontosaurus-Deinonychus associations. Journal of
Vertebrate Paleontology 15(4):707-712.

Paul, G.S. 1998. Terramegathermy and Cope's Rule in the land of titans.
Modern Geology 23:179-217.