Fossilization is a complicated and time-consuming process. It normally happens when sediments are compacted under intense pressure combined with the replacement of organic matter by silica and other materials in a process referred to as petrification. Since most tissue, including skin, organs, and muscle, decays before full fossilization can occur, we mostly find bones. Though there are plenty of bones on this list, we’ve also included a host of other bizarre fossils. (Did someone say fossilized sperm? Oh, we did.) You’ll likely be shocked at some of the weird fossils on this list; ones that unfortunately don’t get as much media attention as they should, such as a turtle the size of a helicopter and an ancient arthropod orgy. Read on to discover the 25 Most Bizarre Fossils Ever Discovered.