The Steller's sea cow (Hydrodamalis gigas) was hunted to extinction by 1768, while the genus Dusisiren is known from fossils dating from the middle Miocene to early Pliocene.
The Steller's sea cow (Hydrodamalis gigas) was hunted to extinction by 1768, whereas the genus Dusisiren has a longer history, with fossils dating from the middle Miocene to early Pliocene epochs.