Re: Waders and fishers

["Tim Williams" <twilliams_alpha@hotmail.com>]

Martin Baeker <martin@turtle.ifw.ing.tu-bs.de> wrote:

> My question now is: Where are all the dinosaurian waders and fishers?

At the risk of sounding like a broken record, if you consider birds
as a subset of dinosaurs (and in a phylogenetic context, you must)
then the question answers itself.

However, if your question is amended to "Did any animals wade or
catch fish in Mesozoic environments before the emergence of
birds?" then you have an excellent point.

Pterosaurs were flying long before birds, and many almost certainly fed on 
fish.  An array of archosauromorphs and lepidosauromorphs no doubt prowled 
rivers and lakes and coastlines in the Triassic.  (I also have a picture I 
my head of _Tanystropheus_ using its long neck as a fishing line.)  Then 
there's the sea reptiles that no doubt haunted the seaside during the 
Mesozoic.

> They were not there because there were less fishes around in the mesozoic. 
> (I have next to no clue on fish evolution.)

It's not my strong point either.  However, there is a view that the rise of 
teleost fishes was due to the rise of birds:  Unlike other fishes, teleosts 
didn't need to pop their heads up above the water to aerial breathe, and 
were therefore less exposed to sharp-eyed birds.  I'm not sure I agree with 
the theory, but there you have it.

BTW, I believe the Cretaceous hesperornithids are the stratigraphically 
earliest example of dinosaurs that were habitually subaquatic.  AFAIK, 
that's around the time that the first putative aquatic mammals appear 
(_Kollikodon_, _Steropodon_).  Are there any examples of pre-mid-Cretaceous 
aquatic mammals? - I could be wrong on this point.



Tim

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