The molar design that is considered one of the most important characteristics of mammals is a three-cusped shape called a tribosphenic molar. This design of molar has two important features: the trigonoid , or shearing end, and the talinoid , or crushing heel. With the exception of Jurassic mammal Shuotherium , the talinoid is posterior the triginoid.
The tribosphenic design appears in all species of mammals. In monotremes, it seems to have developed independently, rather than from common ancestry with marsupials and placentals.
