In addition, most marsupial species have 40 to 50 teeth, more than most placental mammals. Marsupials possess a pair of small bones in the pelvic region, called epipubic bones, that may have served to help support the reproductive pouch in ancestral marsupial forms. Also, in many marsupial species the hind limbs are larger and better developed than the forelimbs. Likewise, the tail is often well developed and may be used for support or grasping. The wide range of marsupial body shapes, sizes, and structures indicates that these animals have adapted to a variety of environments.
Marsupial mice live on the forest floor, and marsupial moles burrow beneath the ground.
Some marsupials have developed the ability to glide through the forest like flying squirrels. The water opossum is adapted for life in aquatic habitats, like many placental mammals. Kangaroos and wallabies live on grasslands. The present-day geographic distribution of marsupials is similar to what it was about 65 million years ago. Then competition with placental mammals for living space may have limited the marsupials' range.