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

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

III. Horns and Antlers

   A. Antlers (only in males except caribou)

• shed annually
• tusks that got out of control (of dentary developmental origin)
• velvet nourishes antlers
• adaptive advantage of shedding is a mystery

• may be epidermal in origin (Rhino)
• skin and bone (giraffes)
• not shed
• pronghorn - sheds epidermal sheaths
• true horns are non shedding / nonrenewable

IV. Mammalian Teeth

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

    B. Types (per half of upper or lower jaw)
        1. incisors (2 to 5)
        2. canines (never more than 1): Hold and cut food
        3. premolars (2 to 4)
        4. molars (usually 3): grind up food (new to mammals)

    C. Tooth Formulas (per 1/2 of jaw)
        1. upper/lower

V. Modifications of Tooth Structure

    brachydont = short tooth (herbivores)
    bunodont = rounded cusp
    diastema - separation between incisors and molars (exaggerated in many grazers to keep eyes above grasses)
    cheeks - skin stretched between upper and lower jaws
    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 (persoiodactyl = horses)
    selenodont (cresent shaped) longitudinal cusps (artiodactyl = deer)
    sectorial cutting
    Carnassial Apparatus 1st upper and 4th lower premolar

VI. Nontrophic Functions of Teeth

    A. Tusks
        1. males in some
        2. both sexes in elephant
        3. recurved lower canines in pigs
        4. upper incisors = pure dentine

    B. Display Canines
        1. Walrus Tusks

VII. Skull Design, Muscles and Feeding Ecology

    A. Inovative Features
        1.  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
        1. tight jaw articulation
        2. well developed temporalis
        3. condylar process is near occlusal plane (teeth close like scissors)
        4. molars and premolaras are sectorial
        5. Carnassial Apparatus

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