Ondatra (muskrat)

1. cheek teeth with crowns bearing prismatic patterns of dentine
2. M¹ and M² with middle portion divided into a number of sharp-angled triangles
    Click here to see an example of a tooth with the middle loop undivided (Neotoma)
3. dorsal border of infraorbital foramen virtually straight
4. cranium abruptly constricted in interorbital region
5. basal length (front of incisive foramen to middle of foramen magnum) > 50 mm
6. postorbital processes nearly right-angled in shape and projecting into orbit as thin-edged shelves