Xenocarida
Xenocarida is a proposed clade inside the subphylum Crustacea that comprises two classes that were discovered in the 20th century: Remipedia and Cephalocarida. Both groups are marine hermaphrodites. The clade was recovered as the sister groups to Hexapoda.
However, other studies do not recover Xenocarida as a monophyletic group and variously find Branchiopoda or Remipedia as the hexapod sister group