Mammutosaurus

Mammutosaurus is an extinct species of sauropod that lived in what is now Alaska in 75-63 million years ago in the Cretaceous and Paleocene period. It was the first ever confirmed species of sauropod that had supported feathers (or feather-like structures) all over its body, after its fossilized remains with feather-like impressions were found. Like all sauropods, it was a herbivore that fed on leaves from conifers and other types of trees. It was about twice the size of the largest African elephant in history. Despite surviving past the Cretaceous-Paleocene mass extinction, it didn't make it pass into the Eocene. No one knows why, but it is possible that the Earth got much warmer after the mass extinction, too warm for this sauropod to survive for much longer.