On display at the Denver Museum of Nature and Science, a tooth from an ancient Carcharodon shark:
I’ve posted about Carcharodon Megalodon here before — it was a giant shark that lived millions of years ago. But Carcharodon is a genus of sharks — it also includes the modern day great white shark. This tooth is placarded as belonging to a Carcharodon and dating to about 20 million years back (the early Miocene epoch). Based on its size (tough to measure since it’s behind glass, but easily the size of a man’s hand) and age, it’s likely from a Megalodon. You can easily imagine that this would fit comfortably in a beast some 25 meters (82 feet) long.