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Let's be logical, guys. Amongst birds only the passerines, or
song-birds, hop. Granted the passerines form the l argest number
of species, but they are only one small groups among many others
of equal rank. They are a late evolutionary group among the birds.
The common ancestors of Saurischia (including Aves, if you prefer,
though my own preference is to regard Aves as a separate class)
and the Ornithischia walked on all fours. Bipedalism evolved
at least three times in these groups, at least once is Ornith-
ischia, once in Saurisschia proper, and once, separately, in
Aves. Bipedalism also evolved more than once in mammals.
Now even if bipedalsim is necessary for hopping, not all bipedal
animals hop. Kangaroos and thrushes may hop, but crows walk,
and so does Homo sapiens.
Bipedalism is a pre-requisite for hopping, but the fact that two
species are b ipedal does not point to common ancestry and can
tell us nothing about whether they both hop or do not.
For all I know some dinosaurs MAY have hopped, but birds'
hopping can tell us nothing about dinosaurs. I know of no
good evidence that dinosaurs hopped. Does anyone else?
A new reference for your book-shelves, on the extinction of
dinosaurs: Carlisle (1995) "Dinosaurs, diamonds and things from
outer space: the great extinction." Stanford University Press
(paperback). Just out this week.
>From: David Brez Carlisle