The oldest known sperm in the world has been discovered, locked in a piece of amber that solidified when behemoths like Spinosaurus dominated the Earth.
The giant sperm comes from a much more miniscule creature than the toothy Spinosaurus: an ostracod, a crustacean that looks like a shrimp dressing up as a clam for Halloween. Known colloquially as “seed shrimp,” ostracods typically grow just a few tenths of an inch long. Their bodies are protected by a bivalve shell, from which tiny, crab-like appendages sometimes protrude.
There are thousands of ostracod species alive today, and many boast giant sperm cells, the longest of which unspools to a jaw-dropping 0.46 inches (11.8 millimeters), far longer than the animal that produces it. Now, scientists have found an example of this enormous sperm in an ostracod from the Cretaceous period, 100 million years ago. It’s the oldest unambiguous example of any animal sperm by 50 million years.