Class Mammalia
Sub Class Prototheria
Order Monotremata
Platypus, Echidna
Sub Class Theria
Order Metatheria
Marsupials
Order Eutheria
Placental mammals
Characteristics
Originated from therapsids: Mammal like reptiles
Fossil mammals from the Triassic (190 million yrs)
Co-existed with dinosaurs
Large radiation in mammals at extinction of dinosaurs
Amniotes
Epidermal hair
Mammary glands for milk secretion
Homoeothermic and endothermic
High internal body temp
4 chambered heart
Reproductive cycles
Metanephros kidney (Conserves water, nitrogenous
waste removal, maintains ion and acid-base variation)
Sweat glands
Monoecious
Internal fertilisation
Placental attachment of embryo (except monotremes)
Hair
Made of keratin
Two kinds
Underhair
Dense and soft
Provides insulation
Guard hair
Coarse and long
Protection against wear and tear
Coloration
Also Vibrissae (whiskers)
Reproductive cycles
Definite mating cycles
Males capable of fertile copulation at any time
Female restricted to an oestrus cycle
3 patterns of reproduction
i) Monotremes
One breeding season per year
One, (echidna), or two eggs, (platypus)
Leathery shell on each egg
Incubation for 2 weeks
Feeding via nipple
NO GESTATION
Primitive yolk sac placenta
Embryo does not implant in the uterus
Erodes depression in uterine wall
Absorbs nutrients via yolk sac
Gestation is short
Young tiny at birth
Prolonged lactation interval
Viviparous placental mammals
Investment in gestation
Long Gestation period
Embryo remains in uterus
Nourishment via placenta
Small mammals, short gestation
Large mammals, long gestation (cf whales)
Condition at birth varies
Monotremata (one opening)
Rectum and urinogenital system open to common cloaca
Includes Platypus, 3 species of echidna
Split off from ancestral mammal in Mesozoic
No true teeth in adults
Skull retains reptilian like features
Vertebrae are reptilian like (cervical ribs)
Pectoral and pelvic girdles reptilian like
Milk produced from modified sweat glands (no nipples)
Hair and/or spines
Body temperature 29-32oC
Echidnas hibernate (body temps ambient)
Echidnas have no sweat glands; Lethal temp 38oC
Grooved poison spine on male tarsus
Used for territorial battles and mate immobilisation?
Marsupials
Similar to placental mammals except in reproduction
Pouch for holding developing young
Skull contains teeth
No cervical ribs
Epipubic bones to support pouch
Small gestation period more freedom for adult
Rectum and urinogenital system open into a common
sinus
Young make own way to pouch specialisations
Nervous system fully functional at birth
Fore limbs functional at birth
Mouth and olfactory system well developed at birth
Milk injected into young via a teat
Embryonic diapause
Usually multiple reproduction cf male Antechinus
Herbivores, insectivores and carnivores
Australian and South American in distribution
124 species of marsupials in Australia
108 species of Placental mammals
50 bats
48 murid rodents
Placental Mammals
Arose from stock in Cretaceous
Probably insectivorous (teeth)
Placental nourishment of embryo
Chorionic villi spread into uterine wall
Respiratory gases, and food supplied via placenta
No pouch or epipubic bones
Teeth ( dentition shows feeding types)
Most successful of the mammals
Large radiation
Insectivores
All small
Retain many primitive mammalian features eg teeth
type
Plantigrade foot
Flying mammals
Pectoral appendages transformed into wings
"Flying insectivores"
Wings structurally closer to pterosaurs
Wing membrane supported by digits
Feed on insects, fruit, pollen, blood, fish, birds,
small mammals
Echo location
Toothless mammals
eg Ant eaters, Aardvarks, Armadillo
Food swallowed whole and ground up in pyloric stomach
Tongue modified for food capture
Carnivores
Weasels, dogs, raccoons, bears, cats, seals etc
Teeth specialised for killing, cutting
Limbs often modified for high speed
Digitigrade foot posture cf marine carnivores
Semi-arboreal or Terrestrial
Ungulates
Herbivores eg cows, antelope, horses etc
Teeth adapted for grinding
Modification of limbs for high speed (escape)
Unguligrade feet
Major food for carnivores
Terrestrial and aquatic
Rodents
Gnawing teeth
More species of rodents than all other mammals
Chisel like incisors; continually growing
Whales
Toothed and baleen
Hair present in foetus, often lost in adults
Suckle young
Insulation provided by fat, rather than hair