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Re: Waders and fishers




Tim Williams wrote:
> 
>
> I was not claiming that all extinct monotremes were aquatic simply because
> one modern representative (the platypus) is aquatic.  Nor were _Steropodon_
> and _Kollikodon_ platypus "clones".  Nevertheless, the original descriptions
> provide evidence favoring aquatic feeding for both these monotremes.  From
> the Australian Museum website:
> 
> "The Cretaceous monotremes were probably similar in size and shape to the
> modern platypus

Size, maybe. Steropodon was about the size of a domestic cat, so perhaps
in the size range of the largest of male platypus. Kollokodon was a bit
larger. But shape? How did they determine the overall shape of the
animal from jaw fragments?

> although in modern monotremes the well-developed teeth of
> the fossil forms are absent.  _Steropodon galmani_ may have used
> electroreceptors in its snout to hunt crustaceans in a similar manner to the
> modern platypus.

A big use of the word "may" there. Again, how they inferred
electroreceptors (on the tip of the snout) from a lower jaw fragment is
beyond me.

>  The recently discovered _Kollikodon ritchiei_ has unusual
> dome-like teeth, which earned it the nickname 'hotcrossbunodon'.  These
> blunt, rounded molars may have been used to crush the hard shells of mussels
> and other shellfish."

or land-based animals like snails, large beetles, etc. The evidence for
aquatic behaviour is scant and ambiguous, and largely based on analogy
with the modern platypus. When it comes of monotremes, we have to think
outside of the extant square (if indeed a square can have only two
sides).

If only for some articulated post-crania...

-- 
________________________________________________________________

Dann Pigdon                   Australian Dinosaurs:
GIS / Archaeologist         http://www.geocities.com/dannsdinosaurs
Melbourne, Australia        http://www.alphalink.com.au/~dannj/
________________________________________________________________