Class Mammalia

General Characteristics• Bilaterally symmetrical• Hair• Mammary glands (produces milk)–Nurse young

• Endothermic (warm blooded)• Unique inner ear – Incus, Malleus, Stapes• Dioecious - Internal fertilization• Diphyodonty – Two teeth (replace teeth once)• Lower Jaw – Made of one bone attached directly

to head (improved power)

• Heterodont dentition– Specialized teeth with different function

• Birth to live young• Produce a placenta (usually) – nourishing fetus

(similar to yolk sac in reptiles/birds)

Mammalian Orders 6 Major Orders:

1.) Order Rodentia2.) Order Artiodactyla3.) Order Carnivora4.) Order Cetacea5.) Order Primates6.) Order Monotremata

Order Rodentia Rodents!

Mice, squirrels, gophers, beavers, & guinea pigs

Many have been pests Have continuously growing incisors

Incisors = front teethMust gnaw to keep short

• Have a short breeding cycle• Largest group of mammals

Order Artiodactyla• Pigs, hippos, camels, deer, sheep, etc.• 220 species• Means “even-toed” – they lost the first (many

have shortened the 2nd and 5th

• Mostly obligate herbivorous/grazing animals–Suinae (hogs/pigs)•Are omnivorous – eat both

Order Carnivora

• Meat eaters!• Canines, cats, bears, raccoons,

seals, otters, walruses, etc.• 260 species• Are predatory

• Enhanced vision and hearing• Have special teeth and/or claws

to take down prey

Order Cetacea

• Whales and dolphins• Have blubber for insulation• Up and down movement of tail

(unlike side to side by fish)• All aquatic• Highly intelligent

• Use sonar to locate food

Order Primates• Gorillas, chimps, orangutans,

humans, monkeys, lemurs• Bipedal – stand on two feet• Adaptations for tree-living–Strong limbs with opposable

digits

• Generally largest brain:body ratio–Small ants & small birds

• Extensive parental care

Order Monotremata

• Duck Billed Platypus and Echidnas (spiny anteater)• Only mammals to lay eggs• Have a single opening called a cloaca for

urination, defecation, and reproductive• Platypus has a poisonous barb on the

back foot

Order Monotremata

Echindas

Poison Barb