» Not to be confused with order Sirenidae (aquatic salamanders) For the Gothic metal band, see Sirenia (band) Sirenia is an order of fully aquatic, herbivorous mammals that inhabit rivers, estuaries, coastal marine waters, swamps, and marine wetlands. The order evolved during the Eocene epoch, more than 50 million years ago. Sirenians, including manatees and the Dugong, have major aquatic adaptations: forelimbs have modified into arms used for steering, the tail has modified into a paddle used… (More on Sirenia)