Size and Weight:
About the Mastodon:
As if the differences between mammoths and mastodons weren't confusing enough, the deceptively mammothy-sounding genus name "Mammut" actually belongs to what most people call the North American Nastodon. (Technically speaking, the early elephants known as mastodons--"nipple teeth"--browsed on leaves, while woolly mammoths grazed on grass, like modern cows.) Also, the Mastodon shouldn't be confused with two similar-sounding genera: Stegomastodon was a genus of prehistoric elephant only remotely related to Mammut, and Mastodonsaurus wasn't even a mammal, but a prehistoric amphibian.
Of the various species of Mastodons, only the North American variety had a coat of hair, one of the reasons it's so often confused with the Woolly Mammoth. European and Asian mastodons died out millions of years ago, during the Pleistocene epoch, but Mammut americanum persisted well into the Ice Age (around 10,000 B.C.), when it was hunted to death by early human settlers, who coveted its meat, its fur, and its five-foot-long horns--which doubtlessly were employed as ornaments or ground up into "magical" powders.
Interestingly, Mastodon fossils have been dredged up almost 200 miles off the coast of the northeastern U.S., showing how high water levels have risen over the past few million years (and, ominously, hinting at the coastal flooding that may occur in the near future given our current spate of global warming).