EVIDENCE FROM 18S RIBOSOMAL DNA THAT THE LOPHOPHORATES ARE PROTOSTOMEANIMALS INARTICULATE

The suspension-feeding metazoan subkingdom Lophophorata exhibits chara cteristics of both deuterostomes and protostomes. Because the morpholo gy and embryology of lophophorates are phylogenetically ambiguous, the ir origin is a major unsolved problem of metazoan phylogenetics. The c omplete 18S ribosomal DNA sequences of all three lophophorate phyla we re obtained and analyzed to clarify the phylogenetic relationships of this subkingdom. Sequence analyses show that lophophorates are protost omes closely related to mollusks and annelids, This conclusion deviate s from the commonly held view of deuterostome affinity.