Opabinia

[Ken Kinman]

Bill,
       Thanks for the feedback.   I doubt that Opabinia got more than a few
inches long, and if it is a larval form it probably underwent metamorphosis
at 3-4 inches in length, and some small Anomalocarids are about that size.
      And an Opabinia-like animal, _Myoscolex_, is found in the Lower
Cambrian Emu Bay Shale in Australia, along with at least two species of
Anomalocaris.  See Briggs and Nedin, 1997 (J. Paleont., 71:22-32).
Opabiniids are bound to turn up in China as well, if they haven't already.
      I do plan to elaborate on my ideas on my homepage.  I have been
putting if off thinking Collins would be describing his _Hurdia_
anomalocarid, but almost 9 years later we're still left waiting for that
(unless it has appeared recently).
      Anyway, without access to such material, it is very difficult to come
to any conclusions.  And yet it is also very frustrating waiting, and I have
no sign whatsoever that any of the anomalocarid "research teams" is
seriously considering these alternatives, so I figure it's about time that
they are discussed.
      Just trying to get the ball rolling on some internet discussion
groups, and see what happens.  If there is any evidence to falsify either
the larval form or dwarf male hypotheses, I would like to hear it, but I
have been unable to find any reason to doubt these alternatives.
      I do not know why others have not considered such alternatives (at
least in print, as far as I know), but I think it is a mistake not to try to
falsify them.  I always like Charles Darwin's comment that "without
speculation there is no good science" (or something to that effect).
Anyway, I think these ideas are worth considering, and am tired of waiting
for published papers that might not even discuss such possibilities.
                        Cheers, Ken
********************************************************
Bill Shear wrote:
>Ken, how about sharing some of the evidence for your various hypotheses?
>You invite criticism but that is hard to provide without knowing why you
>came to the conclusions you did.
>
>One thing to think about is this--if O. is a juvenile of A., there should
>be some intermediate growth stages around.  Both are fairly rare, so these
>could be hard to find, but given mortality through time, there should be a
>lot more Opabinia than Anomalocaris if the former is the young of the
>latter.  Assuming of course that the chances of preservation are roughly
>equal at all stages of the life cycle.  No such intermediate stages have
>ever been found.  I don't know if the Burgess Shale has yielded more of one
>or the other.
>
>If Opabinia is the dwarf male of Anomalocaris, then Opabinia should
>be found wherever Anomalocaris occurs.  I don't think Opabinia has
>been found anywhere else but the Burgess Shale (could be wrong),
>while Anomalocaris has turned up at numerous sites around the world,
>most notably and abundantly in China.
>--
>
>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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