• I. Skeletal features
• II. Teeth
• III. Hair*
• IV. Glands
• V. Pinnae*
• VI. Internal soft structures

I. Skeletal features

1. Dentary bones*
2. Dentary-squamosal joint*
3. Ossicles*
   1. Articular --> malleus
   2. Quadrate --> incus
   3. Columella --> stapes

4. Auditory bulla*
5. Other important skull features
   1. Cranium
   2. Mandible
   3. Zygomatic arch

6. Other common skeletal characteristics
   1. More complete ossification
   2. Fusion of small bones into larger, single bones
   3. Dorso-ventral flexion
   4. Five well-differentiated types of vertebrae
      1. Cervical (including atlas=1, axis=2)
      2. Thoracic
      3. Lumbar
      4. Sacral
      5. Caudal
   5. Limbs and girdles
      1. Manus
      2. Pes
      3. Pollex
      4. Hallux

II. Teeth

1. Homodont dentition
2. Heterodont dentition
   1. Incisors: cutting, gathering food
   2. Canines: capturing food, communication displays
   3. Premolars: grinding or slicing
   4. Molars: grinding or slicing

3. Deciduous* or milk teeth

III. Hair*

1. Function
   1. Insulation
   2. Filter out harmful UV radiation
   3. Communication

2. Anatomy
   1. Keratinized epidermal cells
   2. Living root
   3. Follicle
   4. Sebaceous glands (secretes oil)
   5. Arrector pili muscle (causes piloerection)

3. Types (based on function and how they grow: definitive vs. angora)
   1. Vibrissae (whiskers)
   2. Guard hairs
      1. Spines
      2. Bristles
      3. Awns
   3. Under hairs
      1. Wool
      2. Fur
      3. Velli

4. Hair color
   1. Coloration patterns
   2. Pigments
      1. Eumelanin (blacks to browns)
      2. Pheomelanin (reds to yellows)
      3. Combinations (agouti)
   3. Moulting and hair replacement

IV. Glands

1. . Mammary glands*
   1. Anatomy
      1. Mammary tissue
      2. Milk ducts or cistern
      3. Nipple or teat
   2. Milk production

2. Sebaceous glands*
3. Sweat glands*

4. Scent glands

V. Pinnae*

VI. Internal soft structures (Often related to homeothermy)

1. Respiratory system
   1. Muscular diaphragm*:
   2. Secondary palate (bone) and soft palate*

2. Circulatory system
   1. Four chambered heart
   2. Enucleate erythrocytes*

3. Brain
   1. Neopallium.
   2. Corpus callosum

4. Reproduction (related to vivparity)
   1. Placenta