To help us understand this joke, let's take a look at the two meanings of the word mammoth.
1 - A mammoth (noun): a bit like a dinosaur that was very big and looked like an elephant.
2 - Mammoth (adjective): very large, "Cleaning up all the mess after last night's party was a mammoth task. Thanks for helping."
Skeleton - the bones of a human or an animal.
Paleontology - the study of old bones and fossils as a way of getting information about the history of life on Earth.
