AP is reporting that the Yangtze River dolphin (Lipotes vexillifer) is "effectively extinct" following a 20 million year existence on this planet. A six week search yielded no sightings, down from thirteen sightings in 1997. It is believed that overfishing and sub-aquatic sonar pollution led to the extinction and that the species is the first cetacean to be rendered extinct by human action.
I don't suppose there's a breeding population in captivity?
Unsurprising, as I explain here.
Caledonian, I read elsewhere that the last captive specimen died a year or two ago. So no hope there. Someone has suggested we keep the DNA and resurect them later.