Mammalia Mammal Evolution Mammals are believed to have
Mammalia
Mammal Evolution • Mammals are believed to have evolved from Reptiles during the late Jurassic period
Mammal Evolution • The first true mammal was a small, shrew-like organism that coexisted with Dinosaurs – Ex. Hadrocodium fossil found in Northern China in 2002
Mammal Evolution • Mammal’s inner-ear bones probably evolved from modified ancestral reptile jaw bones
3 Major Reproductive Categories • Monotremes – Egg-laying mammals (Ex. Echidna + Platypus)
3 Major Reproductive Categories • Marsupials – Embryos born very early and nurse from inside mother’s pouch (Ex. Kangaroo, Koala)
3 Major Reproductive Categories • Placentals – Embryos develop inside the womb, receiving nutrients and O 2 from the mother via the Placenta – Newborns fed milk from mammary glands.
Mammal Characteristics • Characterized by hair and mammary glands • Whales have very little hair
Mammal Characteristics • Mammalian brains are more developed and specialized (cephalized) than any other class of animals
Mammal Characteristics • All mammals have special glands that are modified for producing milk, called Mammary glands
Mammal Characteristics • Mammals are Heterodontic – Teeth are differentiated – Used for biting, grinding, tearing and crushing – Ex. Incisors, molars, canines, etc.
Mammal Orders • There are 19 orders of mammals • We will look at the characteristics of 14 of them • Order: Monotremata – Lay Eggs (Ex. Echidna, Platypus) • Order: Marsupiala – Young grow in pouch (Ex. Koala)
Order: Insectivora • Small pointed teeth, adapted mainly for eating insects – Ex. Moles, Shrews, Hedgehogs
Order: Rodentia • Nearly 50% of mammals are rodents • Have no canine teeth, but two very larger incisors • Almost all are herbivores – Ex. Mice, Squirrels, Beavers
Order: Edentata • Have no teeth – Ex. Armadillos, Sloths, Anteaters
Order: Carnivora • Very diverse group, • Meat eaters • Canine teeth highly developed – Ex. Wolves, Bears, Raccoons, Otters, Skunks, Mongoose, Cats
Order: Serenia • Aquatic mammals that breathe through their mouth and nose • Herbivores – Ex. Manatees and Dugongs
Order: Chiroptera • Forelimbs adapted for flight • May find prey by echolocation – Ex. Insectivorous Bats, Old World Fruit Bats
Order: Lagomorpha • Large incisor teeth • Hindlimbs larger than forelimbs – Ex. Rabbits and Pikas
Order: Cetacea • Fully aquatic mammals • Vestigial pelvic bones • Evolved from a wolf/bear-like land mammal
Order: Cetacea • Highly developed brain • Have a dorsal blow-hole – Ex. Toothed Whales, Baleen Whales
Order: Proboscidea • Nose and top lip are highly enlarged into a muscular trunk for grasping items – Ex. Elephants
Order: Primata • Highly developed brains • Often bipedal – Ex. Lemurs, Monkeys, Apes, Humans
Order: Primata • Humans are relatively new primates • We appear to share a recent common ancestor with chimpanzees
Order: Artiodactyla • Hooves with even-numbered toes • Many of them are ruminants with a 4 chambered stomach – Ex. Deer, Giraffe, Cattle, Pig, Camel, Hippo
Order: Perissodactyla • Have odd-numbered toes – Ex. Horses, Tapirs, Rhinoceroses
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