The species was totally unknown to science until the late 1950’s, when it was first described from skulls and some sightings. Phocoena sinus – commonly called the vaquita, meaning little cow – is about 4.5 feet long, 120 pounds, and exists only in a small area in the northernmost part of the Upper Gulf of California in Mexico. Now, 55 years since its discovery, the smallest marine cetacean in the world is also the most endangered.