A 505-million-year-old fossil suggests jellyfish pre-date dinosaurs.
Since jellyfish don't have any bones, fossils of ancient jellies are challenging to find. But in 2007, a preserved jellyfish fossil was discovered in Utah that's thought to be over 505 million years old. Dinosaurs lived from about 245 million to 66 million years ago, meaning jellyfish pre-date them by at least 250 million years.