Clarification on Mammals

I made a mistake in saying that shrews developed naturally on Australia as a placental mammal; it was actually rodents, bats, and pinnipeds (seals, etc). There are no non-human-introduced shrews in Australia. My mistake.

Also, I mentioned that it must have been a coup to wrest shrews away from rodents, but upon further research, shrews have been distinct from rodents since Linnaeus started to classify animals in the late 1770s.

Rodents have incisors that grow continuously for life, so they must gnaw on seeds or other hard things to wear them down, while shrews don't have this problem. They are similar in size, but apparently that's about all. Shrews have five-clawed toes, while rodents only four. The only terrestrial mammals that use echolocation are two species of shrew (bats fly, so I'm not calling them terrestrial). Also, besides the platypus, the only other venomous mammals are shrews.

Bet you know more about an animal that you could care less about, right?