platypus
Technical point #1: Since only the male platypus has the venomous spurs, and only the female platypus lays eggs, there would actually not be any venomous egg-laying mammals.
Technical point #2: There are no egg-laying marsupials. The platypus belongs to the monotremes.
You're thinking of the platypus, which lays eggs and can eject venom. But the platypus isn't a marsupial. No marsupial lays eggs or is venomous. The platypus is part of a small group called the Monotremes.
Duck-billed platypus
A marsupial is a mammal.A deer is not a marsupial, which is a sub-group of the mammal classification. A deer is known as a placental mammal, or Eutherian.
There are two misconceptions in this question. First, there are no egg-laying marsupials. All marsupials give live birth. Second, there are numerous venomous mammals. Many species of shrew, as well as the Cuban Solenodon, are venomous mammals. The only egg-laying mammal that is venomous is the platypus, which ejects venom through a hollow spur on each ankle. Only maturemales have spurs and can eject venom. The platypus is a monotreme, not a marsupial. Monotremes are egg-laying mammals.
An elephant is a mammal, not a marsupial.
An ibex is not a marsupial. It is a placental mammal.
A wallaroo is a marsupial.
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).
Neither. Possums, or at least true possums, which are found in Australia, are marsupials.
A kangaroo is a marsupial mammal.
Yes, a wombat is a mammal and a marsupial.
A "Marsupial".