A living organism is called a living fossil if the characteristics of a fossil animal of the past match the characteristics of a living animal of the present. Fossil organisms survive on Earth in morphologically and physiologically unchanged forms.
Characteristics of Platypus
(i) Body of platypus is covered with hair.
(ii) They lay eggs containing yolk and the eggs hatch.
(iii) They have active mammary glands.
(iv) Their cubs drink mother’s milk.
(v) T-shaped thoracic skeleton of platypus.
The features of the platypus are very similar to those of past fossil animals. Hence the platypus is called a living fossil.