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Re: Platypus niche (was Re: The birds vs. the pterosaurs)



> As one
> listmember put it, niches are the way by which organisms divide up the
> available resources in a given habitat.  A niche is not so much a "socket"
> waiting to be filled by a "peg" in the form of a species.  It is more like
a
> piece of a jigsaw puzzle, in which the size and shape and location of each
> piece is determined by the size and shape and location of each neighboring
> piece in the puzzle.  Together, the puzzle pieces combine to "fill out" a
> complete picture.  Individually, each piece is almost meaningless.

Erm... true.

> As for the "platypus niche" existing since the Early Cretaceous...  This
is
> based on the identification of the Australian monotreme _Steropodon_ as an
> ornithorhynchid (the platypus family).  I don't think this is still
regarded
> as correct; _Steropodon_ is a monotreme, but not an ornithorhynchid.

AFAIK it is even regarded as an ornithorhynchid (Rich & Vickers-Rich:
Wildlife of Gondwana, 1999 [partly updated from the 1993 version], but with
that piece of jaw known...

> A second Early Cretaceous monotreme from Australia, _Kollikodon_, is
> certainly not an ornithorhynchid.  Interestingly, based on _Kollikodon_'s
> dentition, this mammal may have been a shellfish-eater and hence aquatic.

Just read it probably had a beak... I don't know how they found that out on
that piece of lower jaw.

> But since _Steropodon_ and _Kollikodon_ are both known only from jaw
> material, I think it's fair to say we have very little idea how similar
the
> ecologies of these Early Cretaceous monotremes were to that of the modern
> platypus (_Ornithorhynchus_).  (This is even more true of a possible
> ornithorhynchid from the Paleocene, named _Monotrematum_, which is known
> only from a tooth.)  The earliest monotreme which is known to have at
least
> looked like the modern platypus is the Miocene genus _Obdurodon_, known
from
> a beautiful skull (among other material)found in the Rivesleigh site in
> Queensland, northern Australia.

Well, I'd say it is still a good idea to say that _Steropodon_ and
_Kollikodon_ behaved like _Ornithorhynchus_, if only because their teeth
seem to look similar enough to those of _Obdurodon_ and a recent young
platypus...