Re: feather tracts

["ptnorton" <ptnorton@msn.com>]

It is not at all clear that the feather tracts seen in some birds today is
necessarily reflective of any basal arrangement of dermal elements.  For one
thing, not all birds have feathers arranged in pterylae (aka "feather
tracts")--many taxa have feathers evenly distributed over the body-- so
who's to say which is the more derived condition? Even birds that have
pterylae often have down feathers growing in the apterial spaces, so it
seems to me that one could reasonably suggest that the basal condition
involved an even distribution of proto-feathers. And since most (all?) of
the taxa with even feather distributions are either flightless of primarily
aquatic, it seems that lifestyle exerts some selective pressure on feather
arrangement.

PTN