What IS Ainiktozoon?

[Ken Kinman]

Dear All,
     First off, Alex Ritchie assures me that the "weird fossil" is indeed
just an inorganic concretion---either a septarian nodule or a "thunder egg".
  Darn it, how disappointing reality can be, but I guess it's time to move
on to "real" fossils.
     I was surprised to learn that Ritchie does NOT accept the recent
re-interpretation of Ainiktozoon as a thylacocephalan crustacean, if it is
an arthropod at all.  In his 1985 paper on Ainiktozoon (Alcheringa,
9:117-142), he argues that it could very well be a highly specialized
protochordate related to urochordates (tunicates).  I preliminarily
classified it as such in my 1994 classification, but also noted that it
could be a hemichordate or an even more primitive deuterostome.
     I would be interested to hear if others have any opinions on the
affinities of Ainiktozoon, as an arthropod, a deuterostome, or something
else.  Quite frankly, it would not surprise me if it turned out to be
related to molluscs.  Afterall, arthropods aren't the only animals which
have evolved compound eyes (they also occur in some bivalves and sabellid
tubeworms).
     So I guess the classification of Ainiktozoon remains an open question.
Trouble is that very few people pay much attention to it, even those who are
fascinated by problematica.
         --- Cheers, Ken Kinman


_________________________________________________________________
Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp.