- Merga violacea
- Mesaiokeras mikhailini
- Mesaiokeras semiplenus
- Mesaiokeras tantillus
- Mesocalanus tenuicornis
- Mesocomantenna spinosa
- Mesodinium acarus
- Mesodinium pulex
- Mesonychoteuthis hamiltoni
- Mesopodopsis wooldridgei
- Mesorhabdus angustus
- Mesorhoea sexspinosa
- Metacylis jorgenseni
- Metacylis sp.
- Metacyphocaris helgae
- Metamysidopsis elongata atlantica
- Metamysidopsis macaensis
- Metamysidopsis munda
- Metamysidopsis swifti
- Metasesarma rubripes
- Meterythrops picta
- Metoporhaphis calcarata
- Metridia brevicauda
- Metridia calypsoi
- Metridia curticauda
- Metridia discreta
- Metridia gerlachei
- Metridia longa
- Metridia lucens
- Metridia princeps
- Metridia venusta
- Microlissa brasiliensis
- Micropanope nuttingi
- Micropanope pusilla
- Micropanope sculptipes
- Micropanope urinator
- Microphrys antillensis
- Microphrys bicornutus
- Microphrys garthi
- Microphrys interruptus
- Microsetella norvegica
- Microsetella rosea
- Mimocalanus cultrifer
- Mimonectes gaussi
- Mimonectes loveni
- Mimonectes sphaericus
- Miracia efferata
- Miracia minor
- Mithraculus coryphe
- Mithraculus forceps