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[doo-ter-uh-stohm, dyoo-] /ˈdu tər əˌstoʊm, ˈdyu-/
Embryology. a mouth that develops separately from the blastopore.
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.
Compare protostome.
1945-50; deutero- + -stome Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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deuterostome in Science
Any of a major group of animals defined by its embryonic development, in which the first opening in the embryo becomes the anus. At this stage in their development, the later specialized function of any given embryonic cell has not yet been determined. Deuterostomes are one of the two groups of animals that have true body cavities (coeloms), and are believed to share a common ancestor. They include the echinoderms, chaetognaths, hemichordates, and chordates. Compare protostome.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Article for deuterostome

(Greek: "second mouth"), group of animals-including those of the phyla Echinodermata (e.g., starfish, sea urchins), Chordata (e.g., vertebrates), Chaetognatha (e.g., arrowworms), and Brachiopoda (e.g., lamp shells)-classified together on the basis of embryological development. During that process the mouth of the Deuterostomia develops from an opening into the embryonic gut other than the blastopore, which develops into the anus. The coelom (body cavity) develops from buds off the embryonic gut. A number of Deuterostomia have larval forms. The Deuterostomia constitute one of two divisions of the coelomates (animals having a coelom). Compare Protostomia.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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