Many different terms have been proposed for features of the tooth crown in mammals. The structures within the molars receive different names according to their position and morphology. This nomenclature was developed by Henry Fairfield Osborn in 1907 and is, although with many variations, the one that continues today.

Suffixes

Tooth structures bear suffixes in order to note the type of structure they are and whether they are present in the upper or lower molars.

Major features

The positions of tooth features are described along four directions: mesial (forwards, towards the chin), distal (backwards, towards the jaw joint), lingual (inwards, towards the tongue), and buccal or labial (outwards, towards the cheek).

Upper teeth

Therians (marsupials and placentals) ancestrally have roughly triangular upper molars, with the apex pointing lingually (inwards) and the flat edge positioned labially (outwards). This fundamental three-pointed structure is sometimes called the trigon. Three major cusps are almost always present: Other common features include:

Lower teeth

Therians ancestrally have lower molars which are longer from front-to-back than from side-to-side. Five to six cusps are most common. The trigonid region at the front part of the molar is triangular, with three large cusps: The talonid region at the rear part of the molar has two to three relatively small cusps which define the rear rim of a low basin: Other common features include:

Image gallery

Cricetidae molar teeth nomenclature after Reig (1977)

These are a list of tooth features identified in the rodent family Cricetidae (hamsters, voles, New World mice and rats, etc.). Source:

Upper teeth

Lower teeth