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In a message dated 95-12-06 21:24:01 EST, email@example.com
(Chip Pretzman) writes:
>So the characteristics
>separating major groups of tetrapods could have occured over a very short
>period of time, right? Like synapsids and diapsids? Dinosaurs and birds?
>Birds and mammals? The accumulation of pattern differences could actually
>lead one to believe that birds and mammals, for instance, are farther apart
>than they truly are.
Indeed they could have accumulated over a short period of time. Except that
with _Archaeopteryx_ it seems to have taken most of the Jurassic Period.
However, we can never exclude the possibility that the lineage the led to
_Archaeopteryx_ appeared in the Early Jurassic but left no birdlike
descendants (or, for that matter, large cursorial descendants) in the fossil
record until the Late Jurassic.