这个词是什么意思？
An order of wholly aquatic MAMMALS occurring in all the OCEANS and adjoining seas of the world, as well as in certain river systems. They feed generally on FISHES, cephalopods, and crustaceans. Most are gregarious and most have a relatively long period of parental care and maturation. Included are DOLPHINS; PORPOISES; and WHALES. (From Walker's Mammals of the World, 5th ed, pp969-70)
中文名称索引；定义为 MeSH 英文原文，尚未逐条译审。MESH:D002591 · MeSH 2026。
Courtesy of the U.S. National Library of Medicine. Annual snapshot; later updates may not be reflected. NLM does not endorse this service.