Mammals of Australia introductions of placental mammals into Australian fauna were about (rats), several thousand years ago (dingo), and 200 years ago (many species); the last two were made by humans. Some claims were made about placental mammal fossils from the Eocene of Australia, called "Tingamarra". These claims are based on only one found tooth having some characteristic features of condylarth, and were discussed widely. But both the age and placental nature of these fossils were challenged by other researchers. Monotremes are mammals with a unique method of reproduction: they lay eggs instead of giving birth to live young. Two of the five
Marine Mammal Protection Act Indian manatee, sea otter, polar bear, and Pacific walrus. Species not present in U.S. waters include the West African and Amazonian manatee, dugong, Atlantic walrus, and marine otter. In efforts to conserve and manage marine mammal species, the Service has appointed field staff dedicated to working with partners to conduct population censuses, assess population health, develop and implement conservation plans, promulgate regulations, and create cooperative relationships internationally. Various Marine Mammal Management offices are located on either coast. The Service's Marine Mammal Management office in Anchorage, Alaska is responsible for the management and conservation of polar bears, Pacific walruses, and northern