From: adpeters@sunflower.bio.indiana.edu (Andy Peters)
Subject: Re: lophophore relationships
Organization: Program in Evolution, Ecology, and Behavior, Indiana University
Date: Wed, 7 Oct 1992 02:51:13 GMT

In article <97817@bu.edu> colby@bu-bio.bu.edu (Chris Colby) writes:
>In article <91820@netnews.upenn.edu> weemba@sagi.wistar.upenn.edu (Matthew P Wiener) writes:
>>In article <1193@tdat.teradata.COM>, swf@teradata (Stanley Friesen)
>writes:
>
>>>the lophophorate phyla (brachiopods, bryozoans, and an obscure group
>>>called the phoronids) are generally considered to be more or less
>>>intermediate between the protostomes and the deuterostomes.
>
>>I've usually seen them presented as deuterostomes.
>
>I just got a invertebrate biology book recently and they give the
>relationship as:
>
>echinoderms	lophophorates hemichordates	chordates
>   *                 *              *               *
>      *                 *              *         *
>           *               *               *
>                *                *      *
>                    *                *
>                         *        *
>                             *  *
>                               *
>                         deuterostomes
>
>This is a cladistic analysis based on morphological data. They give
>"Ciliated feeding tentacles derived from mesosome and containing
>extensions of the mesocoel" and "Circulatory system derived, at least
>in part, from archenteric mesoderm" as two synapomorphies for
>lophophores and chordates. (They list loss of tentacles as a character
>leading to chordates, so I may have misused the term synapomorphy
>because the resulting distribution of that character is paraphyletic
>(not shared by all descendents)).(Gee, now I may have used paraphyletic
>wrong as I'm not sure characters can be referred to as paraphyletic.) 

Chris - keep on reading.  If I recall correctly, B & B report at least
2-3 other possible cladograms, all placing the loph split before
echinoderms.

However, it is true that lophs are definitely considered as deuterostomes
by most (my current #1 prospect for a study organism is a freshwater
bryozoan, tho' my knowledge of their phylogeny is less than perfect).
Though I object to the use of ther term "intermediate" by Stan, it's
generally accepted that the lophs are an early branch off the deutero
lineage, and therefore (assuming deuteros and protos are monophyletic,
which was not certain a long time ago when I was learning this stuff)
are probably the deutero group most closely related to the protostomes.

>REFERENCE:
>Brusca and Brusca, 1990, Invertebrates, Sinaeur, Sunderland, Mass
>
>This is (IMHO) a cool book. The stuff about torted and untorted
>gastropods just screams to be included in any list great examples
>of "jury-rigged" design. 

Yes, it's a great book.  Apparently a little dense for an undergrad
inverts course, but I love it.

>>-Matthew P Wiener (weemba@sagi.wistar.upenn.edu)
>
>Chris Colby 	---	 email: colby@bu-bio.bu.edu	---

-- 
* Andy Peters                     * "Slugs are small and portable    *From
* Program in Evolution,           * Just stuff 'em up your nose      *"Slugs,"
*      Ecology, and Behavior      * They'll fit beneath your armpits *by David
* Indiana University, Bloomington * Or right between your toes"      *Greenberg
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