A minor phylum of mesozoan worms that are internal parasites of a range of marine invertebrates.
- They are now believed to be made up of two, possibly unrelated, groups: the Dicyemida and Orthonectida.
- As it turns out, the Orthonectida are almost certainly metazoans, particularly under our stem group definition; but it's anyone's guess whether they, or any other members of the mysterious Mesozoa, are also bilaterians.
orthonectid noun& adjective
- Example sentences
- In some orthonectids, circular and longitudinal muscles occur beneath the epidermis.
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