What is the opposite of a mammal?

Answer 1

There is no "opposite" of mammals, only different life forms, such as reptiles (cold-blooded, egg-laying) or insects (very dissimilar) or bacteria (not multicellular).

Mammal is a classification, within a group of many other classifications, with their own distinct characteristics. Some major characteristics like being warmblooded or being a vertebrate could be the reverse, but the animals would still share many characteristics. Therefore there is no opposite to the term.
Egg laying animals are known as oviparous.

Answer 2

Well, considering a mammal is a vertebrate, than the opposite of any animal with a backbone would an invertebrate. This leaves us with protozoa, annelids, echinoderms, mollusks, and arthropods. Does this answer your question?

Answer 3

No animal is actually the opposite of a mammal. Although many animals may be considered, such as insects or mollusks, or even cephalopods.

Answer 4

no it is opposite to reptile