PHYLOGENY, ONTOGENY AND SYSTEMATICS OF RECENT SORITACEA EHRENBERG 1839 (FORAMINIFERIDA)

The phylogenetic relationships of 18 species of the Soritacea can be inferred from cladistic methodology. From 28 homologies, based on test morphology, the most likely (i.e., most parsimonious) cladogram contains 15 monophyletic groups. This cladogram, in which the ontogeny of homologues is documented for each species, appears to be satisfactorily robust in a variety of contexts. For instance congruent sequences of character development among all species is consistent with the postulate that ontogeny has remained stable during the evolution of this group. The cladogram is used to predict which biostratigraphic ranges are consistent with character ontogeny and distribution of homologies. Finally, the distribution of the symbiont flora among the examined soritid species is consistent with the branching pattern of the cladogram, as well as with the ''symbiosis hypothesis'' for soritid evolution. During this study, fine structural analysis of embryonic soritids revealed the presence of a double-layered porcellaneous wall, in which the outer layer is pitted and tubulated, rather than porous, and the inner layer is solid. A new species from the Pacific, Marginopora kudakajimaensis, is described.