The monophyletic origin of the Brachiopoda

Abstract

Although it is commonly accepted that the brachiopods descended from phoronid-like ancestors there is dispute over their origin. Traditionally they have been regarded as a monophyletic group, a clade. More recently it has been claimed that brachiopods are polyphyletic and that several of the orders arose independently from separate phoronid-like stocks. The latter point of view implies that brachiopods are not a taxon but merely a grade of organization. Traditional stratophenetic approaches do little to resolve this problem, which may be outside their domain. It is possible, even probable, that the initial radiation involved organisms that lacked mineralized shells. Cladistic analysis of both living forms and Lower Paleozoic taxa strongly supports the contention that brachiopods are monophyletic and closely related to the phoronids. The inarticulate Paterinida and Kutorginida are genealogically more closely related to the Articulata than they are to the remaining Inarticulata.