Predator traps (Re: Tyrannosaur numbers)

[Phil Bigelow <bigelowp@juno.com>]

> Michael Lovejoy (michael@palaeoproductions.fsnet.co.uk) wrote:
> 
> <I know it was just an example to illustrate the point, but it's 
> something I've
> wondered about. Are there any sites that suggest theropods stuck in 
> a predator
> trap? Any refs?>


So far, no predator traps have been found in the Hell Creek Fm.  Traps
require deep wet mud, or quicksand, or tar.  The Hell Creek landscape was
well drained and it contained no La Brea-style lakes of tar.

BTW: "fossilized quicksand" might be identifiable, in theory at least. 
In extant quicksand, the sand grains are uniformly elongated and
loose-packed, with a porosity of between 30% - 70% and no matrix.  In the
case of  "fossil" quicksand, the porosity and grain packing would have
changed during lithification, but the uniformly elongated grain shape of
the "clean" sand would be retained.  In sandstone quarries where large
numbers of theropods have been found, it may be worthwhile to look at the
sand grains microscopically.  Is the Cleveland-Loyd quarry composed of
sandstone?

Ancient mud traps are probably petrographically unrecognizable.   A mud
trap is just regular mud with an increased water content.

Multiple _T. rexes_ have been found together ("Sue" was found along with
elements from a smaller _T. rex_), but those aren't predator traps. 
Rather, they are cases where moving water concentrated the corpses.

<pb>
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