A crocodile is a reptile, not a mammal.
They mean the same thing it is just that mammals is the plural form of mammal.
Marine mammals are divided between the orders Cetacea, Sirenia, and Carnivora. Whales, dolphins, and porpoises are in the order Cetacea. Manatees and dugongs are in the order Sirenia. Seals, sea...
mammals can give birth to live young they have hair on their bodies and they can produce milk.
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