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 Rodentia 2.) Order Artiodactyla 3.) Order Carnivora 4.) Order Cetacea 5.) Order Primates 6.) Order Monotremata

Order Rodentia Rodents! Mice, squirrels, gophers, beavers, & guinea pigs Many have been pests Have continuously growing incisors Incisors = front teeth Must 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 Poison Barb Echindas