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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)
Ronald I. Orenstein Phone: (905) 820-7886
International Wildlife Coalition Fax/Modem: (905) 569-0116
1825 Shady Creek Court
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