Key to Megacalanus, females and males

1 Head with crest in females and males.................................................. Megacalanus frosti n. sp.

- Head without crest in females and males...................................................................2

2 Posterolateral lappets of Pd5 rounded in females and males.............................. Megacalanus ohmani n. sp.

- Posterolateral lappets of Pd5 triangular in females and males................................................... 3

3 Female A1 ancestral segments XV and XVI posterior border smooth; male right A1 segment XIX with 1 distal fused gripping element........................................................................ Megacalanus ericae n. sp.

- Female A1 ancestral segments XV and XVI with posterior border blunt teeth; male right A1 segment XIX without distal fused gripping element.................................................................... Megacalanus princeps