About 17 million years ago, a shrimp-like creature had sex in a cave in Australia, but instead of an afterglow, she got hit almost immediately with what one scientist thinks was a "torrential rain of bat droppings," reports Australia's ABC News. Her misfortune then is scientists' delight today, because the chemicals in the bat guano preserved both her and the sperm still inside her. "Nobody has ever seen sperm fossilized like this before," says a palaeontologist from the University of New South Wales. "This is the oldest sperm in the world."
Scientists actually found four female ostracods and one male preserved in the bat cave, and all had sperm inside them, reports USA Today. In fact, the male had what's known as "giant sperm" coiled within, so called because it can be up to four times the creature's actual length. Modern males have the same trait. "These guys were actively in a state of reproduction," explains the palaeontologist. "They were going about it and then suddenly tables turned and all of a sudden all biological activity stopped and they were sent into the future as a time capsule just doing what they were doing." (In other sea-creature news, click to read about a newly discovered jellyfish.)