Molar Teeth in Humans - Molar teeth in humans have either four or five cusps. - Adult humans have 12 molars, arranged in four groups of three at the back of the mouth. - The third molar in each group is called a wisdom tooth. - Wisdom teeth typically appear around the age of 20, but this can vary. - Some individuals may have missing wisdom teeth.

Molar Evolution in Mammals - In mammals, the crown of molars and premolars has complex shapes with cusps and valleys. - Cusps contain dentine and enamel, while crenulations result from different enamel thickness. - Mammalian cheek teeth likely evolved from single-cusped teeth in synapsids. - Additional cusps may have arisen through budding or outgrowth from the crown. - Therian mammals evolved from an ancestor with tribosphenic cheek teeth.

Morphology of Molars - Upper molars have major cusps called cones, identified by prefixes like proto-, para-, meta-, hypo-, and ento-. - Lower molars have cusps with the suffix -id, while minor cusps have the suffix -ule. - A shelf-like ridge on the lower part of an upper molar is called a cingulum. - A similar feature on a lower molar is called a cingulid. - Minor cusps on the cingulid are referred to as cingular cuspules or conulids.

Tribosphenic Molars - The tribosphenic molar is a key characteristic of therian mammals. - The lower molar is divided into the trigonid (shearing end) and talonid (crushing heel). - The trigonid has three large cusps: protoconid, anterior paraconid, and posterior metaconid. - Upper molars have a mirrored structure with the protocone, anterior paracone, and posterior metacone. - Tribosphenic molars likely developed independently in monotremes.

Different Types of Molar Morphologies - Quadrate molars have a hypocone, an additional fourth cusp on the lingual side of the upper molar. - Many mammals have additional smaller cusps called conules located between the larger cusps. - Bunodont molars have low and rounded cusps, common among omnivores. - Hypsodont dentition is characterised by high-crowned teeth with extended enamel. - Brachydont dentition is characterised by low-crowned teeth, like human teeth. - Zalambdodont molars have three cusps, one larger on the lingual side and two smaller on the labial side. - Dilambdodont molars have a distinct ectoloph and are shaped like two lambdas or a W. - Lophodont molars have enamel ridges called lophs that interconnect the cusps on the crowns. - Selenodont molars have a major cusp elongated into a crescent-shaped ridge. - Secodont teeth are adapted for slicing and chopping, commonly found in carnivorous mammals.