Echidnas are not related to moles, but to platypuses. Hedgehogs are not related to rodents, but to moles.
Platypuses live in water, while echidnas live on land and have a large number of spines on their backs for protection.
Echidnas live on the grasslands of Australia, and their spines are modified hairs.
They are characterized by large claws on their forelegs that allow them to dig through soil, and sharp claws on their hind legs.
And, unusually for mammals, they lay eggs.
