Opabinia

[Bill Shear]

Ken,

You also need some reasons to set up hypotheses as well as to
disprove them.  "Why not?" doesn't constitute a very good reason for
thinking something is so.  What are the reasons for thinking that
Opabinia and Anomalocaris are different stages/sexes of the same
animal?  As you state, a striking metamorphosis would be required to
go from one to the other--the change in eye number, acquisition of
frontal appendage, new jaw structures and loss of the "hose nose."
Also as you state, Opabinia were very small and nearly all the
Anomalacaris are from 0.5 to 1.0 meters long.  Where are the
intermediate life history stages?

Both Graham Budd and Simon Conway Morris think the two are closely
related, but distinct, animals.  Both these guys as well as
Whittington and Derek Briggs have studied the actual fossils and have
a lot of experience in a wide range of arthropods.  What they have to
say about the two animals is detailed and quite believable.

So, since you are the odd man out, you have to prove your case.  Mere
plausibility doesn't work...
--

Bill Shear
Department of Biology
Hampden-Sydney College
Hampden-Sydney VA 23943
(804)223-6172
FAX (804)223-6374
email<wshear at email.hsc.edu>
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