De bestiis marinis

Steller's classic work, published in Latin in 1751 and in German in 1753, contains the only scientific description from life of the Steller's sea cow (Hydrodamalis gigas), as well as the first scientific descriptions of the fur seal or "sea bear" (Callorhinus ursinus), Steller's sea lion (Eumetopias jubatus), and the sea otter (Enhydra lutris).
Steller's sea cow was a sirenian, or manatee, inhabiting the North Pacific Ocean and Bering Sea. It was first discovered by Europeans in 1741 and rendered extinct by 1768. It was a 30-foot long, plant-eating aquatic mammal, weighing up to 12 tons, that lived in large herds on the coasts of Alaska and Kamchatka.
Steller made his observations as part of Vitus Bering's second voyage, during which the crew was shipwrecked for 9 months on Bering Island, from November 1741 to August 1742.