Viviparous,(^) −
both extinct and living.
Their young develops in the uterus, testes extra abdominal,
(^) −
cloaca is usually absent.
Primitive mammals which
(^) −
lay eggs.
Newly hatched animals are nourished on mother’s milk.
(^) −
Cloacal opening present.
(^) −
Confined to Australia and its neighbouring islands.
(^) −
Subclasses
Prototheria (Egg-laying mammals)
Class Mammalia
Theria (Viviparous)
Order
Cloacal opening present.
(^) −
Connecting link between reptiles
(^) −
and mammals.
(^) −
E.g.,
(^) −
Platypus (
Ornithorhynchus
),
Spiny ant eater (
Echidna
)
Monotremata
Metatheria
(Pouched mammals
or marsupials)
Eutheria
Placenta is simple and small.
(^) −
Young ones are born prematurely.
(^) −
The females have a pouch or marsupium for
(^) −
keeping and nourishing the young ones.
Placental mammals with well developed
(^) −
placenta.Young born in a relatively advanced stage.
(^) −
Marsupium absent.
(^) −
Cloaca absent but anus is present.
(^) −
Order
Vagina and uterus are double.
(^) −
E.g.,
(^) −
Kangaroo, (
Macropus
), Koala,
Opossum (
Didelphis
)
Marsupialia
infraclasses
Orders (16)
Ornithodelphia
Allotheria
Extinct
EotheriaExtinct
Pontootheria
Extinct
infraclasses