5. Steller’s Sea Cow (Hydrodamalis gigas)
The enormous Steller’s sea cow was first documented in 1741 near the Bering Sea. Closely related to manatees, this gentle giant could grow up to 30 feet long. Tragically, it survived just 27 years after its discovery, hunted relentlessly for its meat and hide. Its docility and slow movement made it especially vulnerable, serving as a stark warning about the risks faced by isolated, unadapted species.
