What IS Ainiktozoon?

Wed May 8 13:57:28 CDT 2002

Allow me to find the original articles and I'll get back to you...

Kind regards, 

Fedor

-----Original Message-----
From: Ken Kinman [mailto:kinman at hotmail.com]
Sent: 7. maj 2002 16:18
To: TAXACOM at USOBI.ORG
Cc: FSteeman at ZMUC.KU.DK
Subject: Re: What IS Ainiktozoon?

      I'm not advocating any particular assignment at this time, but I am no

longer convinced Ainiktozoon is either an arthropod or a primitive chordate.

  As Alex Ritchie pointed out to me, the two compound eyes (upon which the 
thylacocephalan assignment is based) are quite different from one another.  
One is what Ritchie proposed was a median compound eye, the other the 
"reticulate area".
       As Ritchie notes in his 1985 paper (Alcheringa, Vol. 9, page 137), 
compound eyes are also found in some annelids and molluscs.  More 
importantly he describes the similarities between the median "ocellus" (and 
its "pigmented cup") of ascidian larvae, and the "median eye" (and its 
"auriculate organ") of Ainiktozoon.
      He also notes (ibid., page 138) the "strongly developed fibrous nature

of the mineralized skeletal material in Ainiktozoon is quite different from 
that found in arthropods, but it is perhaps significant that the tunic of 
living ascidians, which may be very tough and similar to cartilage, contains

an extensive fibrous matrix consisting of a carbohydrate, tunicin, related 
to cellulose."
     I don't see how Occam's Razor supports the thylacocephalan assignment 
any more than it does the protochordate assignment.  Seems a very open 
question to me.                  ----- Cheers,  Ken
*****************************************
>From: "Steeman, Fedor" <FSteeman at ZMUC.KU.DK>
>Reply-To: "Steeman, Fedor" <FSteeman at ZMUC.KU.DK>
>To: TAXACOM at USOBI.ORG
>Subject: What IS Ainiktozoon?
>Date: Tue, 7 May 2002 13:03:10 +0200
>
>Hello all,
>
>Well, if you'd ask me: Ainiktozoon is definitely not a chordate of the kind

>that Ritchie proposed. More likely than anything else, it really is a 
>thylacocephalan. I have worked with Thylacocephalans during my Master's for

>Fred Schram. I have also studied some of the specimens of Ainiktozoon that 
>van der Brugghen showed Schram and helped make sense of these. Admittingly,

>Ainiktozoon is a very strange thylacocephalan, but it exhibits most of the 
>basic features of thylacocephalans, save the characteristic arched 3 pairs 
>of forelimbs.
>
>Basically, Ritchie has turned the creature the wrong side round. the 
>"ventral lobe" of Ritchies reconstruction appears to be a thin-shelled 
>dorsal carapace with thickened edges.  I have seen a specimen where this 
>so-called "lobe" was shifted more towards the tail and actually enclosing 
>it much like we see in a crustacean.  I recommend reading the article in 
>Nature by van der Brugghen et al. (1997).
>
>Before we start jumping to reconstructions of freak creatures we should 
>keep in mind Occam's Razor and first try to make sense of it on the basis 
>of known groups. Compound eyes like Ainiktozoon has them are known only in 
>arthropods as far as I know (but correct me if I am wrong).
>
>Yours sincerely,
>
>Fedor Steeman
>
>van der Brugghen, W, F.R. Schram, & D.M. Martill. 1997. The fossil 
>Ainiktozoon is an arthropod. Nature 385:589-590.
>
>-----Original Message-----
>From: Bjørn, Per de Place
>Sent: 7. maj 2002 08:57
>To: Steeman, Fedor
>Subject: RE: [TAXACOM] What IS Ainiktozoon?
>
>
>http://usobi.org/archives/cgi-bin/wa.exe?SUBED1=taxacom&A=1
>
>/per
>
>-----Original Message-----
>From: Steeman, Fedor
>Sent: 7. maj 2002 08:54
>To: Bjørn, Per de Place
>Subject: RE: [TAXACOM] What IS Ainiktozoon?
>
>Hej Per,
>
>Kan du fortælle mig om og hvordan jeg kan tilmelde mig denne mailingliste?
>Ken har ignoreret min henvendelse indtil nu. Ainiktozoon er helt bestemt
>ikke en chordat, medmindre man bruger meget fantasi. Tværtimod viser den de
>fleste karaktere typiske af Thylacocephala...
>
>Mvh,
>
>Fedor
>
>
>-----Original Message-----
>From: Bjørn, Per de Place
>Sent: 3. maj 2002 22:24
>To: Steeman, Fedor
>Subject: FW: [TAXACOM] What IS Ainiktozoon?
>
>-----Original Message-----
>From: Ken Kinman [mailto:kinman at HOTMAIL.COM]
>Sent: 3. maj 2002 17:23
>To: TAXACOM at USOBI.ORG
>Subject: [TAXACOM] What IS Ainiktozoon?
>
>
>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
>
>

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