"Stella II and Antha"
 

Hydrodamalis gigas
52" Steller's sea cow w/ baby. The last generation.
Artist: William Monteleone
 
Georg Willhelm Steller discovered these animals on Bering Island near Kamchatka in the early 1700's. Steller's sea cows are related to dugongs, and more distantly to manatees. The first difference you'll notice is the size. Steller's grew to 25 ft while dugongs seldom exceed 12 ft. Steller's had also lost their teeth and their finger bones during the course of evolution. Instead of chewing with teeth, they munched on kelps with a hard knobby palate. Also the forelimbs were reduced to club-like appendages which they used to scrape algae off the rocks. Another noticable difference was the rough "bark-like" skin. Unlike any living sirenians Stellers' had unusually craggy skin which supported all sorts of creatures like whale lice and barnacles.