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
Mammal work on the systematics, relationships and occurrences of all mammal taxa, living and extinct, down through the rank of genus, though molecular genetic data challenge several of the higher level groupings. The authors worked together as [[paleontologist]]s at the [[American Museum of Natural History]], [[New York City|New York]]. McKenna inherited the project from Simpson and, with Bell, constructed a completely updated hierarchical system, covering living and extinct taxa that reflects the historical genealogy of Mammalia. [[Extinct]] groups are represented by a [[Dagger (typography)|dagger]] (†). Class Mammalia Molecular studies based on [[DNA]] analysis have suggested new relationships among mammal families over