Spider-mouse

Not "spider" as in "spins webs", but rather as in "the males die after mating". Also they're marsupials, not placental mammals, but that's still pretty novel. And kind of heart-wrenching TBH.
https://theconversation.com/doing-it-to ... mice-18884
https://theconversation.com/doing-it-to ... mice-18884