RE: Armadillos at the K/T?

[John Bois <jbois@umd5.umd.edu>]

Jamie Headen said:

>Egg-eating is not a tenable solution to the K/T. It is unviable
>ecologically, and untestable.
>Egg-eating must be a global event, and this has not been at all supported
>by the present data.

Allow me to suggest that "egg eating" is a poor description of what I'm
proposing.  "Predation on offspring" is better.  This may sound like spin
control.  It's not!  Predation on offspring as a persistent selective force
is a well accepted fact; "egg eating" (for some reason, perhaps because we
placentals are somewhat blind to its omnipresence as a selective force in
extant species) is perceived as a somewhat exotic practice, and, therefore,
unlikely to pose threats to any species, let alone many species.  Even after
extirpation of significant predators, rhea suffer a heavy, heavy predation
load.  Because they are easy to find (compared to small birds, at least, but
not compared to much larger non-avian dinosaurs), they are subject to
predation from several species on offspring at several stages, both in the
egg and whilst proceeding through growth to adulthood.  So, I'm not
proposing that a single predator evolved and suddenly wiped out   dinosaurs.
I am saying that there was an increase in potential predators on their
offspring.  I would include birds and other mammals.  And I would welcome
the addition of another player-armadillos-especially one which is so
devastating to extant large egg layers!  This hypothesis _is_ testable.
That they _did_ prey dinos to death may not be testable.  But so what?
There are some things we may never know.  This should not mean that we
accept one hypothesis over another unless there is a good reason to do so.
Many, if not most paleontologists find the bolide insufficient in explaining
the patterns of extinction.  It is an unsatisfactory hypothesis to them.  It
is to me as well.  But I'm not sure why anyone would find predation on
offspring "untenable" when it is such an obvious limitation on extant
species.  All we need to know to give the hypothesis some respect is whether
or not there was an evolutionary change w/in K/T creatures which brought
them into the size ranges and morphologies which today cause oviparous
species much trouble.  The finding of K/T armadillos--if true--adds value to
the hypothesis.