ABSTRACT
Analysis by parsimony, maximum likelihood and distance methods of newly determined nuclear-encoded SSU rRNA gene sequences from 23 species of articulate brachiopods, six inarticulate brachiopods, two phoronids and an ectoproct, together with other sequences from published and unpublished sources show that lophophorates cluster with protostome, not deuterostome metazoa and that phoronids cluster with inarticulate brachiopods. Phoronids, inarticulate, and articulate brachiopods form a monophyletic assemblage. A chiton is the closest known outgroup of brachiopods plus phoronids. Within articulates, separate rhynchonellid and long- and short-looped terebratulid clades are identified and a thecideidine falls within the short-looped articulate clade. Forms with incomplete loops belong either to the short or long-looped clades, thus, a three-fold division of articulate brachiopods suffices to encompass the range of extant diversity so far examined. A perfect correlation was found between clade rank and lineage age rank for five well-dated brachiopod lineages. The important underpinning role of classical brachiopod taxonomy for molecular phylogeny is stressed.
