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Re: Diatryma and mammals!



>Andors in full (Andors, A.V. Reappraisal of the Eocene groundbird
>_Diatryma_ in Campbell, K.E. (ed.) Papers in Avian Paleontology
>-Honoring Pierce Brodkorb #36 Science series Nat. Hist. Mus. of LA County)
>says:
>" Depositional environments and associated floras and faunas indicate that
>the D. were inhabiatants of coastal lowlands and alluvial floodplains
> (Andors 1988) Although eurytropic, diatrymids may have been primarily
>paludal (I can't find that word in any dictionary I own), preffering
>humid, well-vegetated back-swamps that were doomed to contract once the
>period of relative tropicality that characterized the earlly Tertiary came
>to a close.  Their presumed closest relatives (Andors 1988) the
>Neotropical screamers, exhibit similar preferences for marshy habitats.
>the persistence of suitable habitats in northern S. America probably
>explains the survival of the screamers as marginal relicts."

It's hard to judge without seeing the full paper, but this sounds like
speculation to me.  Andors states that diatrymids are "eurytropic" (meaning
capable of tolerating a wide range of conditions, as opposed to
"stenotropic"),
then goes on to say that they MAY HAVE BEEN primarily paludal (which means, I
believe, associated with flooded areas).  Her only evidence cited here is the
current habitat of screamers, which may be related but are certainly very
different birds.  If this is the basis for her conclusion about marshes, I
would describe it as flimsy at best.  There are only three living
screamers, in
two closely-allied genera - certainly not enough to draw conclusions about the
habitat choices of an entire lineage, considering the range exhibited by the
much more specialized ducks and geese.  I can think of a number of bird
families that show a wide range of habitat choices among birds much more
closely similar to each other than are diatrymids and screamers - ibises, for
example.

I'm not saying diatrymids did not prefer swamp forests or swamps - only that I
haven't heard any DIRECT evidence yet that they did.

PS - if diatrymids were indeed eurytropic, that argues against their being
restricted by mammalian competition - eurytropy is hardly a symptom of
competitive restriction!
--
Ronald I. Orenstein                           Phone: (905) 820-7886
International Wildlife Coalition              Fax/Modem: (905) 569-0116
1825 Shady Creek Court                 
Mississauga, Ontario, Canada L5L 3W2          mailto:ornstn@inforamp.net