Although superficially they resemble whales, sirenians have evolved independently. They are descended from the group of ancient land mammals that also gave rise to the elephants. The living sirenians are classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Sirenia, families Trichechidae and Dugongidae.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.