Steller's sea cow

Steller's sea cow Temporal range: Pleistocene– C. E. 1768
Skeleton at the Finnish Museum of Natural History
Conservation status
Extinct (1768)  (IUCN 3.1)[1]
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Sirenia
Family:	Dugongidae
Genus:	†Hydrodamalis
Species:	†H. gigas
Binomial name
†Hydrodamalis 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[2][3][4][5]
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 sirenian described by Georg Wilhelm Steller in 1741. At that time, it was found only around the Commander Islands in the Bering Sea between Alaska and Russia; its range extended across the North Pacific during the Pleistocene epoch, and likely contracted to such an extreme degree due to the glacial cycle. It is possible indigenous populations interacted with the animal before Europeans. Steller first encountered it on Vitus Bering's Great Northern Expedition when the crew became shipwrecked on Bering Island. Much of what is known about its behavior comes from Steller's observations on the island, documented in his posthumous publication On the Beasts of the Sea. Within 27 years of its discovery by Europeans, the slow-moving and easily-caught mammal was hunted into extinction for its meat, fat, and hide.

Some 18th-century adults would have reached weights of 8–10 t (8.8–11.0 short tons) and lengths up to 9 m (30 ft). It was a member of the family Dugongidae, of which the 3 m (9.8 ft) long dugong (Dugong dugon) is the sole living member. It had a thicker layer of blubber than other members of the order, an adaptation to the cold waters of its environment. Its tail was forked, like that of whales or dugongs. Lacking true teeth, it had an array of white bristles on its upper lip and two keratinous plates within its mouth for chewing. It fed mainly on kelp, and communicated with sighs and snorting sounds. Steller believed it was a monogamous and social animal living in small family groups and raising its young, similar to modern sirenians.