Article: Phylogenetic analysis and ordinal classification of the Brachiopoda

The long-standing division of the lophophorate Phylum Brachiopoda into two units of Class rank, the Articulata and Inarticulata, is not supported by phylogenetic (cladistic) analysis. Using the PAUP program, two separate analyses, for seven extant brachiopod orders/suborders and for the combined extant and extinct groups, respectively, are consistent in identifying all chitinophosphatic-shelled stocks as a sister group to the carbonatic-shelled brachiopods, which include both 'inarticulates' and 'articulates' of previous schemes. The chitinophosphatic-shelled stocks are united in the Class Lingulata, but within the Brachiopoda, contrary to the proposals of Gorjansky and Popov (1985). The carbonatic-shelled brachiopods form the Class Calciata, embracing the Subclass Craniformea (including Craniida, Craniopsida, and Trimerellida), and a yet un-named Subclass that includes the Obolellida, Kutorginida, and the 'articulates'. The precise affinities of the kutorginides remain enigmatic, although they are clearly calciate. The proposed relationships suggest that brachiopods are monophyletic and had consistently separate shell chemistries from early in their phylogeny, removing the need for the repeated transformations in biomineralization inherent in previous evolutionary models.