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Re: Theropod traps



>A herd to herbivores I can accept, but such large aggrigations of
>carnivores? That is what seems to be unusual to me. I understand that
>around 60 individual allosaurs are represented at CL Quarry almost to the
>exclusion of other taxa and a similar situation exists as Ghost Ranch for
>Ceolophysis (correct me if I am wrong here, thou I know I don't need to
>ask!). My point is that I do not know of mammalian carnivores or any other
>extant large carnivores that get around in groups of this size. If this is
>the case, doesn't such unusually large aggrigations of dinosaurian
>carnivores, occuring twice, possibly indicate that there is some
>fundemental difference between them and our understandings of modern
>carnivores? How do you feed a herd of 60 Allosauruses?

        I've personally never liked the "herding" theropod theory, although
I admit it _is_ a possibility (just because modern mammals don't do it
doesn't mean dinosaurs didn't!  Birds do, after all...).  For the
Cleveland-Lloyd Quarry, at any rate, the general explanation is that is was
some kind of predator trap, a la the La Brea tar pits.  That is:
herbivores became trapped in a sticky clay (an explanation that has been
offered for the sedimentology of the quarry), which attracted carnivores.
There are other dinosaurs in the CLQ other than _Allosaurus_:
_Camarasaurus_ and _Stegosaurus_, for example...they're just not as common
as the theropods (which also include _Marshosaurus_ and _Stokesosaurus_,
neither of which is currently recognized from anywhere else).

        I'm curious:  today there are tar pits, both the smaller ones in
California and the pitch lakes near Trinidad, in South America...but I've
never heard of a fossilized tar pit!  Does anyone know of any?  Or, for
that matter, a fossil quicksand?  Would that even be recognizeable?



Jerry D. Harris
Denver Museum of Natural History
2001 Colorado Blvd.
Denver, CO  80205
(303) 370-6403
Internet:  jdharris@teal.csn.net
CompuServe:  73132,3372

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