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Re: Bird Question



In a message dated 96-02-02 06:58:41 EST, CALPIN.SHARON@a1.pader.gov (Sharon
A. Calpin (717) 621-3118) writes:

>Post Jurassic question. I'm curious-  When did the large diversification of 
>birds occur? Or was it too gradual to specify?

There were at least two major bird radiations that we know of. The best-known
is the one that is still ongoing--or _was_ ongoing until humanity arrived on
this planet. It started shortly after the Cretaceous extinction event.

The second is the Cretaceous bird radiation, which witnessed the spread of
enantiornithine birds around the world. These seem to have gone extinct in
the Cretaceous extinction along with the dinosaurs. Inasmuch as
enantiornithines were essentially unknown until 1981, we still have a lot to
learn about this radiation. It is very telling that nearly all the known
Cretaceous bird skeletons are of enantiornithine birds.

Naturally, there must also have been a Jurassic bird radiation, of which
_Archaeopteryx_ was a part. There is an undescribed skeleton with feather
impressions of an _Archaeopteryx_-like Jurassic bird from Korea, so
confidence in the existence of this radiation is slowly increasing, but it
will be many years, I think, before we have as good physical evidence of this
radiation as we do of the Cretaceous enantiornithine radiation.