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

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



In a message dated 97-01-24 04:19:55 EST, ornstn@inforamp.net (Ronald
Orenstein) writes:

<< Again I dispute this.  As Jonathan Wagner has pointed out, it won't fit
 hummingbirds - in fact the majority of perching birds (Passeriformes),
 generally accepted to be the most recently evolved (and certainly the most
 diverse) bird lineage, are on the small side - certainly smaller than
 Archaeopteryx and I suspect smaller than their ancestors somewhere down the
 line. >>

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)?

Basically, the fossil record of birds is too poor to use as either an example
of or a counterexample to Cope's Rule.