Re: Ears

[Dann Pigdon <dannj@alphalink.com.au>]

David Marjanovic wrote:
> 
> Phylogenetic bracketing: Among living animals, only placentals and
> marsupials have them.

And monotremes don't. Although we don't have a much of a sample size
left (only two remaining body forms), and one is a swimmer, one a
burrower/digger, so loss of external ears may be secondary to both (see
below).

> So while it's ambiguous whether multituberculates and
> triconodonts had them, we can be pretty certain that no dinosaur ever did.

Can we be so sure? How many extant archosaurs are there? Aquatic
varieties (crocs) and aerial forms (birds) both of which have
aqua/aero-dynamic concerns. Any external ear flaps may have been lost by
both lineages, for the same reasons that whales or moles lost theirs
(okay, so bats throw a spanner in the works - but echolocation
requirements may be a factor there).

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