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

Re: Fossil Discovery Threatens Theory of Birds' Evolution



In a message dated 6/25/00 10:26:27 AM, ornstn@home.com writes:

<< > >> Look at spirula and
>graphitites, I know that neither is a vertebrate, but both evolved to look
>exactly like another group.<<

I am not sure what this means.  Spirula is a cephalopod that looks like a 
squid because it is one, or a close relative of one; coiled shells are 
cetrainly not unknown in cephalopods either, though Spirula is the only one 
with an internal coiled shell of which I am aware.  I am not sure what 
"graphiphites" are but if you mean graptolites, they are apparently close 
relatives of the living acorn worms, which are somewhat distant relatives 
of chordates; a living acorn worm group, the pseudobranchs, has one species 
which produces quite graptolite-like colonies and was even considered to be 
a living graptolite by its discoverer.    I am not sure what else you think 
these animals resemble.  Certainly neither Spirula nor graptolites look 
like any vertebrate. >>

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.

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? 
Sure thing!

eric l.