Steller's sea cow

Steller's sea cow
Drawing of a dead female published by Peter Simon Pallas in 1840, thought to be the only one drawn from an actual specimen
Conservation status
Extinct  (1768) (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Sirenia
Family:	Dugongidae
Subfamily:	†Hydrodamalinae
Genus:	†Hydrodamalis
Species:	†H. gigas Zimmermann, 1780
Map showing the position of the Commander Islands to the east of Kamchatka. The larger island to the west is Bering Island; the smaller island to the east is Copper Island.
Synonyms
List of synonyms Hydrodamalis H. stelleri Retzius, 1794 Rytina R. manatus borealis Illiger, 1811 R. borealis Illiger, 1815 R. cetacea Illiger, 1815 R. stelleri Desmarest, 1819 R. borealis Cuvier, 1836 R. stelleri Burmeister, 1837 R. gigas Gray, 1850 Manati M. gigas Zimmermann, 1780 M. balaenurus Boddaert, 1785 M. borealis Link, 1795 Trichechus T. manatus borealis Gmelin, 1788 T. borealis Shaw, 1800 Sirene S. borealis Link, 1794 Nepus N. stelleri Fischer, 1814 Stellerus S. borealis Desmarest, 1822 Haligyna H. borealis Billberg, 1827 Manatus M. gigas Lucas, 1891

Steller's sea cow (Hydrodamalis gigas) is an extinct species of sirenian that was discovered in 1741. At the time of its discovery, it was found only in the Commander Islands, which are situated in the Bering Sea between Alaska and Russia. Its closest living relative is the dugong (Dugong dugon), which is the sole surviving member of the Dugongidae, of which Steller's sea cow was also a part. It was among the largest mammals other than whales to have existed into the Holocene epoch, reaching weights of 8–10 metric tons (8.8–11.0 short tons) and lengths of 9 metres (30 ft).

Steller's sea cow was the largest of all sirenians, and had a much thicker layer of blubber than other sirenians; this was an adaptation to the cold waters of its environment. The tail was forked, like that of cetaceans. As opposed to teeth, it had an array of white bristles, and two keratinous plates used for chewing. It was mute and made snorting sounds and sighs. It was monogamous and gregarious, living in small family groups. It fed solely on kelp. It probably cared for its young, like extant sirenians.

Georg Wilhelm Steller discovered Steller's sea cow in 1741 on Vitus Bering's Great Northern Expedition when he and his crew were shipwrecked on Bering Island. Much of what is known about the sea cow in life comes from Steller's account on the island documented in his posthumous publication "The Beasts of the Sea". Within 27 years of discovery by Europeans, the slow-moving and easily captured Steller's sea cow was hunted into extinction for its meat, fat, and hide, though sightings have been claimed after 1768.