[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: "Cope's Rule" Put to the Test



>Sorry, but you just don't know this to be true ("generally accepted" doesn't
>count). Early Cretaceous birds are now being discovered in China that are
>sparrow-size, and it could well be true that the common ancestor of all
>ornithuran birds, and indeed of all modern birds, was likewise. And it might
>also well be true that the smaller size of passerine birds is the result of
>only one or two "dwarfing" events, after which the descendant lineages did
>not change body size very much. Do you know of any LARGE sparrows or other
>passerines in the fossil record? If you do, can you show they were ancestral
>to modern smaller sparrows or other passerines? Is the size change
>significant (that is, say, better than a species with a 10-inch-long body
>ancestral to one with a 9-inch-long body)?

I do not dispute any of these points, except to note that a great many
passerines are considerably less than "sparrow-sized".  The problem of
determining lineages I of course recognize - but I note that even if a
sparrow-sized bird gave rise to ornithurines the evidence we have suggests
that somewhere down the road its ancestors were bigger.  I certainly was
not implying that passerines evolved dwarfism over and over again (though I
suspect that they have done so more than once, species like the
sunbird-asities and the anianiau of Kauai being possible living examples of
independent size reductions).
--
Ronald I. Orenstein                           Phone: (905) 820-7886
International Wildlife Coalition              Fax/Modem: (905) 569-0116
1825 Shady Creek Court                 
Mississauga, Ontario, Canada L5L 3W2          Internet: ornstn@inforamp.net