Key to families of Odontoceti in Korea

1 Nares of similar size................................................................................... 2

- Skull extremely asymmetrical; left nare much larger than right......................................... Physeteridae

2 Heterodont teeth; large teeth restricted lower jaw; no teeth on upper jar.................................... Ziphiidae

- Homodont teeth; mandibular symphysis short: <1/3 of mandible length........................................... 3

3 Teeth <12, concentrated from frontal tip to 2/3 of jaw and absent on 2/3 to rear end of both upper and lower jaws................................................................................................... Monodontidae

- Teeth>12, evenly distributed on both jaws (except Grampus: only lower teeth)..................................... 4

4 Teeth pointed; no bony boss on nares............................................................. Delphinidae

- Teeth blunt; bony boss on nares................................................................. Phocoenidae