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Re: silly question



Gary Vatnsdal <rrlgary@CC.UManitoba.CA> writes:

>I can understand how, for instance, there may have been a reptile
>pressure to be egg retentive and mammals may have developed (although
>how they managed to develop breasts at the same time - maybe internal
>feeding like a kangaroo for awhile) is a bit of a mystery.

Viviparity and lactation did *not* develop at the same time.  We know
this because the platypus has a "primitive" milk let down system and
yet it is oviparous (i.e. it lays eggs).

>But feathers are another thing. There are some coasting mammals like
>flying squarrels, and some flying mammals like the bat and some flying
>dinosaurs like archaeopteryx. But what strange force of nature started
>the development of these feathers?

Feathers are basically modified scales (as are hair and whiskers for
that matter).  The most likely explanation at the moment seems to be
that feathers developed first as insulating devices and only later as
generators of lift.  Unfortunately data which could support or falsify
such a scenario is hard to come by.

>Were Dino birds well developed when the K-T event took place?

Being relatively fragile, birds tend not to fossilize well.  However,
there are a few birds and bird-like dinosaurs known from before the
K-T event.  I'll leave that as an opening for Anusuya to elaborate if
she has time.

-- 
Mickey Rowe     (rowe@lepomis.psych.upenn.edu)