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RE: Sheesh



At 21:55 2006-10-24, evelyn sobielski wrote:

> Honestly, to do so is to just be wrong.

At least until the full fallout of Mayr et al's study
of the Thermopolis Archie has settled in. I'd rather
like to see Confuciusornis removed from Aves sensu
stricto than Deinonychus included in it...

> Why did no dinosaurs become marine until the
> advanced ornithurines? (E.g., hesperornithiforms and
> various neornithines)

Hesperornithids, penguins, plotopterids, and
mancalline auks, Pinguinus and Chendytes as borderline
cases. Did I forget any?

Apparently by "marine" you mean "flightless" (in which case the flightless cormorant and steamer ducks might classify as borderline cases). However I don't see in what way a volant bird that never comes ashore except for breeding is less marine than a flightless bird that never comes ashore except for breeding. In this case albatrosses, shearwaters, storm petrels, diving petrels and auks also qualify with frigatebirds, tropicbirds and gannets as borderline cases.



I can see no clear pattern here. Not even competition
by marine mammals spelling doom - this seems to hold
true for flying seabirds (whether the "Late
Pleistocene supernova" theory is correct doesn't
matter - seabirds simply couldn't get a hold on their
habitat as they did before marine mammal
diversification). Competition by marine mammals does
prevent truly marine birds which are also carnivores
from evolving, but that's no reason for why the
Hesperornithes disappeared (which was some time before
the C/T, IIRC).

So what one can say with certainty is that there were
no truly carnivorous lineages of truly marine birds
(as opposed to flying seabirds) around when and where
there was a large diversity of marine mammals.

Do you consider penguins not truly marine or herbivorous?

Tommy Tyrberg