Mammals

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Mammals
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Characteristics of Mammals

• 3 Middle Ear Bones malleus, incus, and stapes
  (hammer, anvil, and stirrup) the first two
  derived from the ancestral jaw.
• Hair composed of keratin for insulation,
  sensation, appearance, and protection. (other
  keratinized structures horns, antlers,
• Mammary Glands modified sweat glands that, in
  females, produce milk to nourish their offspring.

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• Other important characteristics include highly
  differentiated teeth, 2 sets of teeth, single
  lower jaw bone, 4 chambered heart, secondary
  palate, muscular diaphragm, highly developed
  brain, endothermy and homeothermy, separate sexes
  (XX or XY), and internal fertilization.

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Mammalian Teeth

• Heterodont teeth different types of teeth
• 2 Sets of teeth - Diphyodont
• Dental Formula
• Diastema
• Carnassial apparatus
• Incisors chisel shaped for gnawing and nipping (1
  root)
• Canines long conical for catching, killing, and
  tearing (1 root)
• Premolars and Molars broad for chewing (1-2 or
  2-3 roots)

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Mammalian Glands

• Glands are an epidermal tissue that secrete
  substances.
• Sebaceous secrete oil for waterproofing.
• Sudoriferous sweat for evaporative cooling and
  elimination of waste.
• Scent secrete pheromones for defense, sex
  recognition, and territorial behavior.

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Mammalian Classification

1. Prototheria (Monotremes) - are oviparous
   (Egg-laying).
2. Metatheria (Marsupials) are viviporous with a
   short gestation, further development occurring in
   a pouch. Doubled reproductive features in females
   males.
3. Eutheria (Placentals) are viviparous with a
   long gestation.

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Terrestrial Placental Orders

• Order Artiodactyla
• Order Carnivora
• Order Insectivora
• Order Lagomorpha
• Order Perissodactyla

1. Order Rodentia
2. Order Chiroptera
3. Order Primates
4. Order Edentata (Xenartha)
5. Order Proboscidea

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Order Artiodactyla(Even Toed Ungulates)
st

• Ungulates walk on their toes.
• Most are specialized for cursorial locomotion
  with long hoofed legs, and have diversified as
  the Perssodactyls have declined.
• Number of teeth is variable but they have a
  diastema.
• Males often sport antlers or horns.
• Deer, Sheep, Javelina, Antelope, Cows,
  Hippopotamuses, Camels, Giraffes

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Order Carnivora st

• Although not all current carnivora are
  carnivorous, the ancestors were meat eaters.
• Recognizable carnassial apparatus for shearing
  meat and tendons (between the 4th upper premolar
  and 1st lower molar), keen senses, and large
  brain.
• 3 upper and 3 lower incisors.
• Dogs, Cats, Bears, Raccoons,

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Order Insectivora

• Third largest order of mammals and possibly the
  most primitive group (mesozoic mammals are rather
  shrew-like).
• Moles and Shrews

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Order Lagomorpha st

• Resemble large rodents with short tails.
• Flaps of skin can close behind the incisors and
  close the nostrils.
• 2 upper incisors, one behind the other.
• (2/1, 0/0, 4/4)
• Fenestrated skull
• Rabbits

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Order Perissodactyla(Odd Toed Ungulates)

• Horses, Rhinoceroses, Zebras

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Feeding Adaptations

• Herbivorous mammals have special adaptations for
  digesting cellulose.
• Perissodactyls, lagomorphs, and rodents have a
  cecum or fermentation pouch between the small and
  large intestine. In lagomorphs droppings are
  re-eaten.
• Artiodactyla are ruminants with the first three
  chambers of their stomach are storage and
  fermentation chambers. Food is regurgitated and
  chewed.

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Order Rodentia st

• Largest order of mammals (40 of mammal species).
• Individual upper and lower incisors that are
  rootless and grow throughout life for a gnawing
  life style.
• (2/1, 0/0, 3/2, 2-3/3)
• Squirrels, Chipmunks, Rats, Mice, Beavers, and
  Porcupines

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Being Warmblooded

• Endothermy the generation of internal heat
• Homeothermy the maintenance of constant
  temperature

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Cold Weather Adaptations

• Winter Sleep the organism is less active,
  alert, and easily aroused (Bears and raccoons).
• Hibernation the organism slows metabolism, and
  heart and respiratory rates (monotremes, and some
  insectivora, rodentia, and chiroptera).

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Order Chiroptera

• Second largest order of mammals.
• Bats

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Order Primates

• Lemurs, Tarsiers, Monkeys, Gibbons, and Apes

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Order Edentata

• Incisors and canines absent.
• Armadillos

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Didelphimorpha

• American marsupials

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Order Proboscidea

• Elephants

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Aquatic Placental Orders

1. Order Carnivora Otters, Weasels, Seals,
   Walruses, Sea Lions
2. Order Cetacea Whales, Dolphins, Porpoises
3. Order Sirenia - Manatees