What unique mammalian order do echidnas belong to, shared only with the platypus?

Answer

Monotremata

Echidnas belong to the order Monotremata, which is an ancient and unique branch of the mammalian family tree, shared only with the platypus.

What unique mammalian order do echidnas belong to, shared only with the platypus?
GeographyfaunamammalAustraliaechidna