[Taxacom] Animalia or Metazoa?
kennethkinman at webtv.net
Fri Jul 24 00:25:18 CDT 2009
Kingdom Metazoa = Phylum Porifera (sponges) + Eumetazoa (all the
other phyla). The only question these days is whether the sister group
of Eumetazoa is all of crown group Porifera or some subclade thereof.
Many researchers believe the latter, and that Eumetazoa evolved
specifically from the calcareous sponges, which would make the crown
group Porifera definitely paraphyletic (and even the crown group
calcareous sponges could easily be paraphyletic as well).
The sponges themselves almost certainly evolved from
choanoflagellates, making the latter paraphyletic (as well as the
Protozoa as a whole). The names are thus perfect reflections of what
they are evolutionarily. Protozoa means "first animals", and their
descendants Metazoa ("higher animals"). Makes perfect sense to me.
Animalia (in the sense of Protozoa + Metazoa; first animals +
higher animals) is also paraphyletic with respect to the photosynthetic
protists when they acquired plastids. Metazoa on the other hand is a
clade, unless you believe those old theories that Porifera evolved from
choanoflagellates, and Eumetazoa evolved from some other group of
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