Topic summary
Molars
Extracted from the Wikipedia article Molar (tooth).
Quadrate
From the primitive tribosphenic tooth, molars have diversified into several unique morphologies. In many groups, a fourth cusp evolved in the upper molars. Quadrate (also called quadritubercular or euthemorphic) molars have a hypocone, an additional fourth cusp on the lingual (tongue) side of the upper molar, located posterior to the protocone. Quadrate molars appeared early in mammal evolution and are present in many species, including hedgehogs, raccoons, and many primates, including humans. There may be a fifth cusp.