Uneven Rostrum, Narrow Angle & Small Size Group
GONATUS / GONATOPSIS / EOGONATUS

　CL < Base length of lateral wall. Insertion of cutting teeth is short. Wing teeth locates at 3/4 beak height.
---Gonatus pyros

　(LRL=3.5mm)

　　　CL = Base length of lateral wall. Insertion of cutting teeth is long. Wing teeth locates at 1/2 beak height.
---Gonatopsis octopedatus / Eogonatus tinro　)

　G. octopedatus (LRL=3.1mm)
　E. tinro (LRL=2.5mm)

Beaks of G. octopedatus and E. tinro closely resemble each other. Although beak of E. tinro has not yet pigmented completely, it has narrow angle of lateral walls and a broad pigmented cutting teeth. On the other hand, beak of G. octopedatus has wide angle of lateral walls, a narrow pigmented cutting teeth and a shallow groove between wing teeth and wing hold. When distinguishing beaks of this two species, it is better to compare them with reference beaks of nearly the same size.