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Re: a lot of fog (halkieriids)
> Sorry for not getting to this sooner.
Might be considered off-topic anyway :-)
> One of the reasons I disagree with Simon Conway Morris on his
> of "halkieriids--->brachiopods" is that he too easily dismisses
> and lophophore-like structures as being very homoplastic.
You don't argue for Archicoelomata and for a clade Entoprocta/Kamptozoa +
Ectoprocta/Bryozoa s. str., do you? A filter feeder without the gill
apparatus of a derived deuterostome is supposed to need tentacles. Many
morphologists have questioned the monophyly of Lophophorata/Tentaculata,
though without getting a good idea where to put Bryozoa. On the other hand,
there are pretty good morphological arguments for linking Kamptozoa and
Mollusca (Ax, ?1996, calls them Lacunifera and puts them next to Pulvinifera
= Sipunculida + "Articulata".)
> And the molecular
> evidence is not nearly as definitive as it is being made out to be.
Well, Lophotrochozoa is usually a horrible polytomy, but its contents are
> this "setae" thing is getting as complicated as protofeathers are. No
> simple answers.
Why do you think protofeathers are complicated?
> Another very long-standing problem in zoology is the assumption that
> primitive bilaterians were some kind of motile worms (like flatworms).
As Acoela is the sister group of all others and motile...
> sessile filter-feeders may well be more primitive, and worms like
> may actually be relatively derived
Flatworms are indeed pretty derived = have heaps of apomorphies. But it
really doesn't look like they ever had a coelom, for example.
Some say there was much less plankton way up into the Cambrian than
today. Would be bad for filter-feeders.
> but I
> particularly remember one article on bilaterian evolution by a Dr. Rieger
> the 1991 book by Simonetta and Conway Morris (The early evolution of
> Metazoa). You might want to take a look at Rieger's ideas sometime.
Certainly, the biology library here may well have it, but it's older than
the discoveries of Lophotrochozoa (1995) and Ecdysozoa (1997).