Paleontology professor Petey at the museum, standing in front of a mastodon skeleton. An extinct group of mammal species related to elephants, they inhabited North and Central America and became extinct at the end of the Pleistocene era some 10,000 to 11,000 years ago. Of the genus Mammut, they were members of the order Proboscidea. They lived in herds and fed on a mixed diet of grazing until adopting the North American fast food diet. Petey explains that the mastodons did not survive due to their vacuous diet of Ho Hos, Pop Tarts, Sugar-frosted Coco Bombs and cheese whiz.