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Re: Fossil Discovery Threatens Theory of Birds' Evolution




First of all, spirula, ain't a squid, it's a cuttlefish of sorts, and it's
internal shell looks exactly like an ammonite. quite simply a perfect example
of convergance giving the appearence of a nearly exact copy.

Cuttlefish are a sort of squid, or at least a member of the Decapoda. The shell of Spirula bears some resemblance to that of an ammonite but is hardly "exactly" like one (for example, it does not have the extremely complex folding of the septa that is very much a distinguishing feature of ammonites). Anyway its spiral shape is a pretty basic one in nature, and ammonites and spirula belong in the same class anyway, so the convergence involved seems to me interesting but not all that remarkable. Anyway, I still do not see the relevance of your point in bringing it up.



The graphotite-like colonies we've both mentioned is another example of such
convergance. I've never said that these look anything like theropods as you
seem to be saying. Can nearly exact duplicates evolve completely seperately?

Um... I didn't say that either, and the term is "graptolite". And what are graptolites supposed to be convergent to?


I think the answer to your question depends, though, on what you mean by a "nearly exact duplicate" and on how complicated the structure is you are talling about. Bumblebee hairs, for example, look very much like mammalian hairs, but the resemblance is actually quite superficial and does not extend to details of structure or composition. Is it a "nearly exact duplicate" or just a superficially similar (and basically pretty simple) structure?

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Ronald I. Orenstein Phone: (905) 820-7886
International Wildlife Coalition Fax/Modem: (905) 569-0116
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