Facetotecta is a poorly known subclass of thecostracan crustaceans. The adult forms have never been recognized, and the group is known only from its larvae, the "y-nauplius" and "y-cyprid" larvae. The only known genus is Hansenocaris in the family Hansenocarididae. They are mostly found in the north Atlantic Ocean, neritic waters around Japan, and the Mediterranean Basin, where they also survive in brackish water.

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