The investigators, headed by Professor Christine Janis, used fossil bones of marsupials and placental mammals excavated in Western North America, the only place with a good representation of ...

Kangaroos are pretty peculiar on the outside: They're the world's largest marsupials, they hop to get around, and they use their tails as a fifth limb. But they're also pretty unusual on the ...

Marsupials differ from placental mammals ... of both birds and mammals. Whereas reptiles only have three-chambered hearts and other vertebrates only have two, mammals have developed a more complicated ...