Definition of Sipunculoidea
1 : a group of marine worms of obscure systematic position that are commonly classed as a division of Gephyrea and that lack setae and have the mouth at the end of a retractile introvert similar to a proboscis and usually provided with tentacles and the anus anterior and dorsal
2 in some classifications a : a group coextensive with Gephyrea b : a class or other group comprising Sipunculoidea (see sense 1 above) and Priapuloidea
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Origin and Etymology of sipunculoidea
New Latin, from Sipunculus, genus of marine worms (from Latin sipunculus, siphunculus little pipe) + -oidea — more at siphuncle
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