A wallaroo is a marsupial.
The platypus is a monotreme mammal.
An echidna IS a mammal. It is an egg-laying mammal, known as a monotreme,
The aardvark is a placental mammal.
A mammal which is not a marsupial or a monotreme is called a placental mammal. There is no opposite to a marsupial. An animal is either a marsupial or it is not. Marsupial is the term given to any mammal of the order Marsupialia whose young are born in an immature state and continue development in the "marsupium" (or pouch).
A mammal that is not a monotreme nor marsupial. It could be a monkey, a dog or cat, any mammal really.
A cow is a placental mammal.
The platypus is not a marsupial: it is a monotreme, which is an egg-laying mammal. Marsupials give birth to live young, and do not lay eggs. The other monotreme, or egg-laying mammal, is the echidna.
Neither. A scallop isn't a mammal or even a vertebrate. It is a bivalve mollusc.
I the mammal is a monotreme, it developes in an egg. If the mammal is in the marsupial group, it develops in a pouch on its mother. If it is a placental mammal, it develops in the placenta.
No. The numbat is not a monotreme, or egg-laying mammal. The numbat is a marsupial, which gives live birth.
No. The platypus is an Australian monotreme. The platypus is found nowhere else in the world apart from Australia. However, it is not a marsupial, as marsupials give both to live young. The platypus is classified as a monotreme because it is a mammal that lays eggs.
The Iberian lynx is a placental mammal. All members of the feline family are placental.