I. Key Characteristics

    A. Hair
    B. Mammary Glands
    C. Dentary / Squamosal Articulation
    D. External Pinnae / 3 bones in ear
    E. Complex Dentition (Heterodont vs Homodont)

II. Evolution

    stem reptile led to synapsids led to therapsids led to mammals
    first real mammals in triassic
    cynodontia tree shrew like
    Jurassic - prototheria
    Cretaceous - metatherians and eutherians

III. Horns and Antlers

    Antlers (only in males except caribou)
    shed annually
    tusks that got out of control
    velvet nourishes antlers
    adaptive advantage of shedding is a mystery
    Horns may be epidermal (Rhino)
    skin and bone (gariffes)
    not shed
    pronghorn - sheds epidermal sheaths
    True horns are non shedding / nonrenewable

IV. Mammalian Teeth

    A. Structure
        dentine (inner layer) (harder than bone but softer than enamel)
        pulp
        enamel (exterior) (hardest, heavyest, most friction resistant tissue) (totally acellular)

    B. Types
        incisors (2 to 5)
        canines (never more than 1) Hold and cut food
        premolars (2 to 4)
        molars (usually 3) grind up food (new to mammals)

    C. Tooth Formulas (per 1/2 of jaw)
        upper/lower     2/2        1/1         2/2           3/2
                            incisors canines premolars molars
        most mammals are diphyodont (two sets)

V. Modifications of Tooth Structure

    brachydont = short tooth
                        = herbivores
    bunodont = rounded cusp
    diastema
    cheeks
    incisors- enamel wears more slowly than dentine (self sharpening chisel)
    tubercular - interlocking teeth to pierce as well as grind
    hypsodont (high tooth) enamel folded with dentine = differential wear persoio= horses
    selenodont (cresent shaped) longitudinal cusps (artiodactyla = deer
    sectorial cutting
    Carnassial Apparatus 1st upper and 4th lower premolar

VI. Nontrophic Functions of Teeth

    A. Tusks
        males n some
        both sexes in af elephant
        recurved lower canines in pigs
        upper incisors = pure dentine

    B. Display Canines
        Walrus Tusks

VII. Skull Design, Muscles and Feeding Ecology

    A. Inovative Features
        zygomatic arch

    B. Important Muscles
        1. masseter (zygomatic arch to posterior of mandible)
        2. temporalis (roof of skull to coronoid process of mandible)
        3. pterygoideus (base of skull to mandible)

    C. Adaptations for carnivores
        tight jaw articulation
        well developed temporalis
        condylar process is near occlusal plane (teeth close like scissors)
        molars and premolaras are sectorial
        Carnassial Apparatus

    D. Adaptations for herbivores
        loose jaw articulation
        well developed masseters and pterygoideus
        condylar process is above occlusal plane (teeth close all at once)
        diastema (put face away from food)
        molars and premolars are lophodont (high crowned)