From the excellent Museum of Natural History in Helsinki. The small skeleton in the background is a Baltic Ringed Seal, which gives some idea of scale.
These are impressive specimens, especially the Stellers sea cow (Hydrodamalis gigas), I believe that they also have a Stellers sea cow skeleton at the San Diego Museum of Natural History as well
What a great example of how weird and fascinating a place the internet is!
According to this link, Steller's Seacow in Museums - Searchable Pages , this individual is a juvenile with 2 metres of growth still to put on! It is also one of the only specimens we have that died of natural causes before the species was described by western naturalists.
