-since birds exist, dinos are not truly extinct
Mammals • Origin: Triassic. • Diversified after K/T boundary (last 65 my).– Today ~ 4,500 species.
• Key features: Upright gait—(like dinos), High metabolic rates and constant body temperature, Mammary Glands
for which the class is named. This is a unique feature of the class of course the function of the class, mammary
glands is lactation - that is to provide milk to the developing young, particularly important during the early phases of
their development when they don't have any teeth.
Other Glands: sweat, pheromone (scent) production, etc
Hair or Fur a form of insulation. Part of adaptation for warm bloodedness
Large brains: learning, parental care.
Chewing (several things necessary)
1. Modification of jaw articulation and palate.
2. Cheeks to hold food.
3. Tongue to position food.
4. Several kinds of teeth.
Mammal vs reptile teeth:
Mammals- 1 jaw bone, cuspate and occlusal (top and bottom fit together), heterodont (teeth vary is size, shape,
function), 2 roots and replaced once
Reptiles- several jaw bones, simple cones and non-occlusal, homodont, 0 or 1 root and replaced throughout life
Mammals have a secondary palate below the primary palate of skull that separates breathing and chewing areas
Longer lever arm from applied force to pivot (joint) = bigger mechanical advantage
Mammals need less effort to chew because of the muscle and the jaw bone is closer and it acts as a lever (tweezers
Reptile—temporalis muscle only! (single jaw bone makes jaw stiffer and force goes to what is being bitten than the
flexing where bones join)
Mammal – temporalis + masseter (muscles:
more and bigger
more strength to bite and more control of jaw
movement in different directions)
Mammals are great chewers!
--complex chewing motion (rotary), not just up and down (also forward and back and sideways)
--precise occlusion of teeth for improved food processing
--heterodonty: ability to process (slice, pierce, crush) food in their mouth (masticate) that
other groups lack—break it down, increase surface area:volume;
--improved mechanical efficiency of lower jaw and jaw joint-hard, fast biting
Faster, more efficient digestion in gut
Greater use of available resources
First mammal teeth:
Triassic; first mammal skeleton:
Morganucodon: small shrew-like, insect-eater
smallest living mammal = pygmy shrew
monkeys and apes
FOUR groups of Primates 1. Prosimians 2. New world monkeys 3. Old world monkeys 4. Hominoids (apes +
1. opposable thumb- grasping and manipulation behaviors
2. flat nails instead of claws, (with fingerprints) on fingers and toes: function:
grooming, grasping—try to do that
3. eyes: large, toward front of face: (depth perception; stereoscopic vision)
5. reproduction: smaller litter size, longer gestation (in womb) times, extended period juvenile growth = increased
6. relatively large brains: high learning capacity
7. Shorter snout, smaller number of teeth