https://scitechdaily.com/giant-100-million-year-old-sperm-cells-discovered-the-oldest-known-sperm-cells/In another fascinating snapshot from deep time, an international team of paleontologists has reported the discovery of specimens of a minuscule crustacean that dates back to the Cretaceous (about 100 million years ago), conserved in samples of amber from Myanmar. The most spectacular find is a single female, which turns out on closer examination to contain giant sperm cells in its reproductive tract.
In fact, this is the oldest fossil in which sperm cells have been conclusively identified. Moreover, the specimen represents a previously unknown species of crustacean, which has been named Myanmarcypris hui. M. hui was an ostracod, as clearly indicated by the paired calcareous valves that form the carapace, whose form recalls that of a mussel shell.
