Are Piranhas considered mammals?

Piranhas are not mammals because they are not warmblooded and they do not have limbs, fingers, toes, fur, or hair. Mammals are a group of vertebrate animals. Rats, cats, dogs, deer, monkeys, apes, bats, whales, dolphins, and people are all mammals.

Why Are Piranha Fish Not Mammals?

Most fish are not mammals because they don't have warm blood. However, some sharks and tuna species do have warm blood. They don't have arms, legs, fingers, toes, fur, or hair, and most of them can't breathe air, but the lungfish, bichir and the snakehead are the exceptions. Most have gills that allow them to get oxygen from the water.

Mammals are the only animals that feed their young with milk. All other animals lay eggs or give birth to their young alive. Even pigeons and tsetse flies that feed their young something like milk while they are still in the womb are not mammals.

Fish are not mammals, but there are so many different kinds of fish that putting them all in one class, like they used to be in Pisces, is not helpful. Instead, they are put into three classes and an uncountable number of subclasses, clades, orders, suborders, tribes, superfamilies, families, genera, and species. This is because they are the most diverse vertebrates (animals with backbones) on Earth, even though one of them, the ghastly hagfish, doesn't really have a backbone.