Mammals Key Features Hair keratin Mammary glands Parental care of young Mammalian Taxonomy Monotremes Egg laying mammals Leathery outer covering Found in Australia and New Zealand Produce milk Duck-billed Platypus Egg laying Feed young milk Platypus With Young Echidna - Monotreme Marsupial Live born young Very immature Develop in pouch Cretaceous Today Continental Drift Koala Marsupial Marsupial Young Short gestation Long lactation Placental Mammals Eutherians Diverged from Marsupials ~90 mya Placental Mammals 10 major orders Artiodactyla even toed hoofs, deer, cows Carnivora carnivores, cats, dogs Cetacea whales and dolphins Chiroptera bats Insectivora - shrews Lagomorpha rabbits Perissodactyla odd toed hoofs, horses Primates humans, monkeys, apes Rodentia rats, squirrels Pinnipedia seals and sea lions Fetus is nourished through placenta Long gestation period Gestation vs. Lactation Placenta formation inner cell mass (embryo) trophoblast (embryonic portion of placenta) Placental Mammals Tooth Structure Side to side movement of jaw Grinding of plant material Up and down movement of jaw Scissor-like cutting of flesh Tooth Function Jaw Structure Deer Coyote Jaw Structure Herbivore Lack canines Selenodont teeth Side to side movement Diastema Carnivore Large canines Secodont teeth Wide gape Teeth interlock Carnasial teeth to cut flesh Gastrointestinal Tracts Stomach Comparison Ruminant Stomach Rumination Rumen Microorganisms digest cellulose Some nutrients absorbed through wall of rumen Rumination (chewing cud) Reticulum and Omasum Absorb water Slowly pass material from rumen to abomasum Abomasum True stomach Digestion of microorganisms Digestion of proteins Hoofed Carnivores Pakicetus Whales With Legs Modern Whales Hoofed Herbivore Modern Hoofed Herbivore Gingerichs 1984 Theory of Whale Evolution Pakicetus Is Pakicetus an ancestor of the Whale? Genetic Evidence Decode the DNA DNA sequencing Compare with DNA code of other organisms Determine which organism have the best fit Artiodactyls Gingerichs 2001 Discovery Whales with Artiodactyl-like ankle bones Hoofed Mammals Single Pulley Hoofed Carnivores Pakicetus Single Pulley Deer, Antelope, Hippos etc. Double Pulley Whales With Legs Double Pulley Modern Whales No Legs 65 my 55 my 5 my Hoofed Mammal Double Pulley Vertebrate Swimming Fish Tail vertically compressed Movement side-to-side Whale Tail horizontally compressed Movement up-and-down Whale Spine Movement Movement of whale spine swimming similar to movement of land mammal running