Mammals

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MammaliaMammalia

Mammal EvolutionMammal Evolution• Mammals are believed to have

evolved from Reptiles during the late Jurassic period

Mammal EvolutionMammal 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 EvolutionMammal 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 3 Major Reproductive CategoriesCategories

• Placentals– Embryos develop inside the womb,

receiving nutrients and O2 from the mother via the Placenta

– Newborns fed milk from mammary glands.

Mammal Mammal CharacteristicsCharacteristics

• Characterized by hair and mammary glands

• Whales have very little hair


• Mammalian brains are more developed and specialized (cephalized) than any other class of animals


• All mammals have special sweat glands that are modified for producing milk, called Mammary glands


• 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: PrimataOrder: 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

Education

Mammals