Re: Bird Brains

[dbensen <dbensen@gotnet.net>]

>>
In my unofficial position as a subscriber to this list let me address
this statement as a matter of fact.  "Mammal" and "bird" are
vernacular terms; "mammal" is generally understood to refer to the
class "Mammalia", but what "bird" refers to is frequently a subject of
debate right here on this list.  Stepping back further, though,
whatever animals the categories "bird" and "mammal" encompass, the
categorization can either help or hinder your thinking about
particular questions.<<

My point still stands, however.  I was replying to the statement that,
because birds (classifiable aves)  are an older clade than mammals
(mammalia, having mammary glands as well as ear bones) birds might be more
efficient than mammals.  In any way you think about it, birds cannot be
older than mammals.  Even though the definition of "bird" is extremely
fuzzy at the moment, the classification of mammals is not.  There is no
record of true mammals before the late Triassic (mammals may have existed
before then in, say, alpine environments, but not much longer.)  If you
enlarge the classification of "birds" to its maximum and also take
Chatterjee's find, _Avimimus_ as completely true, then birds may also have
evolved during the late Triassic.  If one is being generous, one can say
that birds and mammals (or if you prefer, Aves and Mammalia) both came
into their own at about the same time.  However, by no stretch can birds
be considered to be much older than mammals.

I could have said all this yesterday, but I assumed that most people
allready knew all of that.  I personaly think that birds didn't evolve
untill the Jurassic and that _Avimimus_ was a precosious archosaur, but I
am willing to change my mind if some new evidence makes itself known.

Dan