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Pterobranchs are colonial hemichordates
living in secreded tubular coenecia. They reproduce by short-lived
planulashaped larvae or asexual budding. Pterobranchs were originally
classified similarly to bryozoans and phoronids based on lophophore
feeding structures. Morphological analysis of the feeding structures
along with molecular data suggest that the similarities are due
to convergence. Study of 18S rDNA sequences indicate that pterobranchs
are monophyletic within the clade. This would indicate that pterobranchs
evolved from a enteropneust-like ancestor.
Cameron, C.B., Garey, J.R.
and Swalla, B. J. (2000) "Evolution of the chordate body
plan: New insights from phylogenetic analyses of deuterostome
phyla." Proc. Natl. Acad. Sci. 97: 4469-4474. (Online) |
