Dozens of perfectly preserved sperm coiled up inside the reproductive tract of a 100-million-year-old female microcrustacean have been identified as the oldest animal sperm ever found.

This tiny crustacean ( Myanmarcypris hui ) had a sexual encounter just before getting trapped in amber that had flowed from a nearby tree, says Renate Matzke-Karasz at Ludwig Maximilians University in Munich, Germany.

The roughly 50 intact sperm cells nestled inside the organs of this newly discovered species of ostracod – small …