What it is
Steller’s sea cow was a huge, slow sirenian — a relative of dugongs and manatees — that grazed kelp. IUCN lists it as Extinct. Georg Wilhelm Steller described it during Vitus Bering’s 1741 expedition.
Range
By the time of European contact it survived only around the Commander Islands in the North Pacific. Bones show a wider North Pacific range earlier in the Holocene.
What happened
Fur-hunting crews killed the animals for meat, fat, and hide. They were easy to approach. The last were taken in 1768. Climate and earlier Indigenous hunting may have already shrunk the range; the final disappearance is a documented overkill.
When / status
Extinct, 1768 — one of the fastest recorded wipeouts of a large mammal.
Human role
Direct hunting by fur crews after 1741 finished a species already confined to islands.
Sources
IUCN Red List (Hydrodamalis gigas, EX); Steller’s 1741 account; 1768 last-kill date in later compilations.