Group includes dugongs and manatees.
Wikipedia: Evolution of Sirenians
Sirenians from Sirenian International
Origin of Sirenians from Edward T Babinski (site is CPU drain)
Dawkins "Greatest Show on Earth" page 172.
As whale is related to hippo, so sirenians to elephant.
Fossil Pezosiren from Eocene. Puijila darwini from Miocene.
