When did the Palaeomastodon become extinct?

Triceratops died out 65.5 million years ago during the K-T Extinction Event. The K-T Extinction Event wiped out all non-avian dinosaurs, pterosaurs, plesiOSaurs, mosasaurs, and 75% of all species in general. It is believed that the event was the result of a 6 mile wide asteroid that smashed into the Yucatan Peninsula of Mexico, leaving a 100 mile wide crater. So much dust and ash was launched into the atmosphere that sunlight was blocked for months or years. This caused plants to die, and thus the animals that ate them also died, including Triceratops.