Inheritance hierarchy of various mammals, including some Australian ones

Mammal inheritance hierarchy

# http://ja.wikipedia.org/wiki/%E5%93%BA%E4%B9%B3%E9%A1%9E
class Mammal
end

# http://ja.wikipedia.org/wiki/%E6%9C%89%E8%A2%8B%E9%A1%9E
class Marsupial < Mammal
end

# http://ja.wikipedia.org/wiki/%E7%9C%9F%E7%8D%A3%E4%B8%8B%E7%B6%B1
class Placental < Mammal
end

# http://ja.wikipedia.org/wiki/%E3%82%AB%E3%83%A2%E3%83%8E%E3%83%8F%E3%82%B7%E7%9B%AE
class Monotreme < Mammal
end

# http://ja.wikipedia.org/wiki/%E3%83%95%E3%82%AF%E3%83%AD%E3%82%AA%E3%82%AA%E3%82%AB%E3%83%9F
class TasmanianTiger < Marsupial
end

# http://ja.wikipedia.org/wiki/%E3%82%AB%E3%83%B3%E3%82%AC%E3%83%AB%E3%83%BC
class Kangaroo < Marsupial
end

# http://ja.wikipedia.org/wiki/%E3%83%92%E3%83%88
class Human < Placental
end

# http://ja.wikipedia.org/wiki/%E3%82%A4%E3%83%8C
class Dog < Placental
end

# http://ja.wikipedia.org/wiki/%E3%82%AF%E3%82%B8%E3%83%A9
class Whale < Placental
end

# http://ja.wikipedia.org/wiki/%E3%83%8D%E3%82%B3
class Cat < Placental
end

# http://ja.wikipedia.org/wiki/%E3%82%AB%E3%83%A2%E3%83%8E%E3%83%8F%E3%82%B7
class Platypus < Monotreme
end

# http://ja.wikipedia.org/wiki/%E3%83%8F%E3%83%AA%E3%83%A2%E3%82%B0%E3%83%A9%E7%A7%91
class Echidna < Monotreme
end