Recent molecular data such as 18SrRNA and mitochondrial DNA gene sequences of lophophorate phyla indicate that they (e.g., Phoronids, Brachiopods and Ectoprocts) place in the protostomes.īarnes (1987) has suggested that chordates evolved from non-chordata group and hypothetical echinoderm larva (dipleurula) and other echinoderm larvae hold the key position. The echinoderms, hemichordates and chordates share some common features such as gill slits (absent in living echinoderms but are found in fossil carpoids), protocoelic nephridium (present in echinoderms and hemichordates but in chordates it has secondarily lost).Īll the five mentioned groups are included under deuterostomes on the basis of embryonic development features. With these groups, the other few minor groups such as lophophorates and chaetognaths are included under deuterostomes but in considerable controversy. The deuterostomes include Echinodermata, Hemichordata and Chordata. Lophotrochozoa, e.g., Molluscs and Annelids. Ecdysozoa, e.g., Arthropods and Nematodes (pseudocoelomates)Ģ. The absence of segmentation in echiurans, sipunculans and molluscs is a secondary loss (Ruppert and Barnes, 1994).īased on current molecular data, it has been suggested that the coelomate protostome animals can be divided into 2 groups:ġ.
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