CLASSIFICATION OF MAMMALS
Mammary glands: hair: diaphragm: three middle-car ossicles; heterodont dentition;sweat, sebaceous and scent glands: four- chambered heart; large cerebral cortex.
(a) Subclass Prototheria
This subclass formerly contained the monotremes. Monotremes have recently been reclassified, and this subclass now contains only extinct species.
(b) Subclass Theria
Technical characteristics of the skull distinguish members of this subclass Infraclass:
Infra class Ornithodelphia
Technical characteristics oldie skull distinguish members of this infraclass, Monotremes.
Viviparous; primitive placenta ; young are born early and often are carried in a marsupial pouch on the female’s belly Marsupials.
Complex placenta; young develop to advanced stage prior to birth. Placental. This infra class has following orders:
1.Order lnsectivora: Diverse group of small, primitive mammals ; third largest mammalian-order. Examples: hedgehogs, tenrecs, moles, shrews.
2. Order Chiroptera: Cosmopolitan, but especially abundant in the tropics; bones of the arm, and hand are elongate and slender; flight membranes extend from the body, between the digits of forelimb, to the hind limbs; most are insectivorous, but some are fruit eaters. fish eaters, and blood feeders: second largest mammalian order. Examples: Bats
3. Order Primates: Adaptations of primates reflect adaptations for increased agility in arboreal (tree-dwelling) habitats; omnivorous diet; unspecialized teeth; grasping digits; freely movable limbs; nails on digits; reduced nasal cavity; enlarged eyes and cerebral hemispheres. Examples: Lemurs (Madagascar and the Comoro Islands), tasters (Jungles of Sumatra and E Indies), monkeys, gibbons, great apes (apes and humans).
4. Order Edentata or Xenarthra: Incisors and canines absent; cheek teeth, when present, lack enamel; braincase is long and cylindrical; hind foot is four toed; forefoot has two or three prominent toes with large claws; limbs are specialized for climbing or digging; xenarthrous lumbar vertebrae. Examples: Anteaters, tree sloths. armadillos.
5. Order Lagomorpha: Two pairs of upper incisors; one pair of lower incisors: incisors are ever-growing and slowly worn down by feeding on vegetation. Rabbits. pikas.
6. Order Rodentia: Largest mammalian order: upper and lower jaws bear single pair of er-growing incisors. Examples: Squirrels, chipmunks, rats, mice, heavers, porcupines, woodchucks, lemmings.
7.Order Cetacea: Streamlined, nearly hairless, and insulated by thick layers of fat (blubber); no sebaceous glands; forelimbs modified into paddle like flippers for swimming;hind limb are reduced and not visible externally; tail fins (flukes) flattened horizon tally; external nares (blowhole) on top of skull. Examples: Toothed whales (beaked whales, narwhals, sperm whales, dolphins, porpoises, killer whales); toothless, filter-feeding whales (right whale gray whales, blue whales, and humpback whales).
8. Order Carnivora: Predatory mammals; usually have a highly developed sense of smell and a lame braincase: premolars and molars modified into camassial apparatus; three pairs of upper and inner incisors usually present and canines are well developed. Examples: Dogs, cats, bears, raccoons, minks, sea urns, seals. walruses. otters.
9. Order Prohoscidea: Long, muscular proboscis (trunk) with one or two ringer- like processes at the tip; short skull with the second mc sot on each side of the upper jaw modified into tusks; six cheek teeth are present in each half of each jaw; teeth erupt (grow into place) in sequence from Front to rear, so that one tooth in each jaw is functional. Examples: African and Indian elephants.
10. Order Sirenia: Large, aquatic herbivores that weigh in excess of 600 kg; nearly hairless, with thick,-wrinkled skin; heavy skeleton: forelimb slipper like, and hind limb is vestigial; horizontal tail fluke is present; horizontally oriented diaphragm, teeth lack enamel. Examples: Manatees (coastal rivers of the Americas and Africa). dugongs (western Pacific and Indian Oceans).
11. Order Perissodactyla: Skull usually elongate, large molars and premolars; primarily grazer; The Artiodactyla also have hoofs. Artiodactyls and perissodactyls are. therefore, called ungulates. Examples: Horses, rhinoceroses, zebras, tapirs.
12. Order Artiodactyla: Hoofed; axis of support passes between third and fourth digits; digits one, two, and five reduced or lost; primarily grazing and browsing animals (pigs are an obvious exception). Examples: Pigs. hippopotamuses. camels, antelope, deer, sheep, giraffes, cattle.