Evaluating internal versus external characters: Phylogenetic analyses of the Echinoconchidae, Buxtoniinae, and Juresaniinae (phylum Brachiopoda)

Abstract

Evolutionary relationships between the Echinoconchidae, Productidae, Buxtoniinae, and Juresaniinae (Phylum Brachiopoda, Order Productida) have been the subject of debate for the better part of a century. The original (Muir-Wood and Williams, 1965) and revised (Brunton et al., 2000) Brachiopoda volumes of the Treatise on Invertebrate Paleontology use markedly different classifications and emphasize different characters. The 1965 Treatise classification for these taxa primarily was based on internal features, especially the cardinal process; the revised Treatise (2000) relied on external ornament and shell shape. Multiple phylogenetic analyses (global parsimony, stratocladistics, nearest-neighbor) of 14 genera, representing all of the relevant subfamilies and outgroups, are in strong agreement that 1) the subfamily Buxtoniinae belongs in the family Echinoconchidae, not to the Productidae; 2) the subfamily Juresaniinae is more closely related to the Echinoconchinae than to the Buxtoniinae; and 3) that internal characters, such as a shafted cardinal process and anterio-medial position of the brachial valve adductor field, provide the best phylogenetic signal, and are synapomorphic for the Echinoconchidae. Jackknifing and Bremer Support corroborate these results.