SMITHSONIAN MAGAZINE - The biological history of leeches is difficult to study: Their tissue decomposes almost immediately, and their boneless bodies rarely fossilize.
But a geological formation in Wisconsin preserved a leech fossil for 437 million years, a new study finds. It’s the first-ever discovery of its kind—and an analysis of the preserved leech suggests the species could be much older than previously thought, preceding dinosaurs by 200 million years.
“A rare animal and just the right environment to fossilize it—it’s like hitting the lottery twice,” says Karma Nanglu, a paleontologist at the University of California, Riverside, and a co-author on the study, in a statement.