The sperm was found in the reproductive tract of a newly mated female ostracod that swam in the oceans 100 million years ago, during the time of the dinosaurs, Newshub reports.
Ostracods, or shells, are the small crustaceans that still exist today. Some of them, including the one found in Myanmar, Myanmarcypris hui, reproduce with the help of a kind of giant sperm. Such fossils are rare: the second oldest ostracod sperm found in Australia dates back 17 million years ago.
According to the authors of the study on the find and published in the publication Proceedings of the Royal Society B: Biological Sciences, a comparison of sperm and reproductive organs of modern ostracods and that found in Myanmar shows that there is no difference between them. This is "a prime example of evolutionary stagnation".
The find also "doubles the age of the oldest uniquely fossil animal sperm", - the researchers said. The previous oldest specimen was 50 million years old and was found in a cocoon of an annelid worm found in Antarctica in 2015.
"The emergence of a complex reproductive mechanism that includes giant sperm has improved mating success and may have been an important contribution to the late Mesozoic explosive spread of the Cypridoidea superfamily, which includes the vast majority of modern non-marine ostracods", - the researchers also write. Previously, the ostracods Myanmarcypris hui were unknown to science.
The photo shows the pairing of two ostracods and the image of the female reproductive tract filled with sperm.