TY - JOUR AB - The Annelida, which includes the polychaetes and the clitellates, has long held the taxonomic rank of phylum. The unsegmented, mud-dwelling echiuran spoon worms and the gutless, deep-sea pogonophoran tube worms (including vestimentiferans) share several embryological and morphological features with annelids, but each group also has been considered as a separate metazoan phylum based on the unique characters each group displays. Phylogenetic analyses of DNA sequences from the nuclear gene elongation factor-1α place echiurans and pogonophorans within the Annelida. This result, indicating the derived loss of segmentation in echiurans, has profound implications for our understanding of the evolution of metazoan body plans and challenges the traditional view of the phylum-level diversity and evolutionary relationships of protostome worms. A1 - McHugh, Damhnait JO - Proceedings of the National Academy of Sciences of the United States of America N1 - Kristian Fauchald's Polychaeta DB SP - 8006 EP - 8009 C1 - 94: 8006–8009 TI - Molecular evidence that echiurans and pogonophorans are derived annelids. UR - http://www.pnas.org/content/94/15/8006.short VL - 94 PY - 1997 Y2 - 2024-03-29 ER -