Pronunciation: (dOO'tur-u-stōm", dyOO'-), [key]
1. Embryol.a mouth that develops separately from the blastopore.
2. Taxonomy.any member of the phyla (Chordata, Hemichordata, Echinodermata, Chaetognatha) in which the anus appears first, developing at or near the blastopore, cleavage is radial and indeterminate, and the mesoderm and coelom form from outgrowths of the primitive gut. Cf. protostome.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.