Teeth High energetic costs associated with higher body T; increased selective pressure for efficient food processing Mammal teeth---modified & specialized to far greater extent than in any other group of vertebrates Slice, dice, puncture, stab, grind, defend, display,.... Teeth alone often indicative of diet Variable BETWEEN major lineages, relatively constant WITHIN species FOSSILIZE; may fossil species described from teeth alone, often a SINGLE TOOTH! Traditionally given heavy emphasis in inferring relationships, BUT often misleading due to convergence, etc.

gumline Crown Root Alveolus (pl. “alveoli”) Enamel: hardest tissue in mammals. 3% organic... “pre-fossilized” Pulp cavity: nerves & vessels. Remains open in rootless, ever- growing teeth (rodent incisors, some cheekteeth) Dentine: same mineral composition, but 30% organic; softer. Cementum: bony material surrounding root

Teeth grow from one of 3 bones

Tooth replacement Living mammals DIPHYODONT (EXCEPT molars!). Ancestral condition for mammals. Most other vertebrates have POLYPHYODONT dentition. “Deciduous” teeth replaced by “permanent” teeth. Replacement timing varies (e.g., shrews) Morphology often different in deciduous teeth vs. permanent teeth Sequence of replacement constant w/in species: useful for AGING

dC1

Canine canine First tooth in maxilla or at maxillary/premaxillary suture. All mammals have AT MOST one canine per quadrant Usually single-cusped (unicuspid), single-rooted (but exceptions) Generally used for stabbing, holding prey in carnivores (but exceptions) Often absent (rodents, some artiodactyls) or heavily modified (elephants) Can be problematic to identify if absent and next tooth is caniniform

Premolars premolars Posterior to canines, rooted entirely in maxilla Variable: tiny, peglike in some, massive crushing tool in others Often “molariform,” but generally smaller, less developed than molars Premolars are replaced, molars aren’t

Premolars premolars Dog carnassial pair

Molars molars Posteriormost teeth in toothrow Variable, but late to erupt Erupt anterior-to-posterior NOT REPLACED!

Cheekteeth molars premolars “cheekteeth” Despite variation in I, C, much of the important functional variation is found in CHEEKTEETH, particularly MOLARS.

“Assembly line” for food processing capture, pick up puncture puncture, shear grind gulp!

“Convergence” within dental arcade: Elk Sea otter Philippine treeshrew “caniniform” incisor “incisiform” canine “molariform” premolar

Primitive dental formula Marsupial: IC P M= IC P M= Placental: BUT 1st premolar (P1/p1) lost in many living placentals, so maximum often 3 premolars!!!!!!!

Primitive dental formula IC P M == Placental: 11 P1 absent in MOST, but not ALL, living placental mammal

Evolution of molars Mammals of Triassic (early) mammals “shearing” action. 3 prominent cusps. cingulum

Upper: Lower: (compare with early mammal) stylar shelf (expanded cingulum) “Tribosphenic” molar pattern

Modifications of the tribosphenic molar Quadritubercular or Quadrate or Euthemorphic tribosphenic quadritubercular

Modifications of the tribosphenic molar Quadritubercular or Quadrate or Euthemorphic stylar shelf (addition of 4th major cusp)

Dilambdodont Crests connecting two prominent outer cones with smaller cones (“-styles”) of stylar shelf form double-V or W-shape. (addition of 4th major cusp)

Zalambdodont = cusps form single V. (Stylar shelf is incorrectly labeled on this figure!) Zalambdodont parastyle mesostyle LOSS of metacone, metastyle.

Omnivores Quadritubercular Bunodont (ROUNDED) Brachydont (LOW-CROWNED)

Herbivores

Brachydont vs. hypsidont

Lophodont (herbivores) hypocone protocone paracone metacone anterior labial

Carnassial pair (carnivores) P4P4 M1M1

protocone paracone metacone anterior labial Carnassial pair

“Assembly line” for food processing capture, pick up puncture puncture, shear grind gulp!