A fossil of the trilobite Pseudoasaphus praecurrens. This specimen dates back 460–468 million years ago to the Darriwilian age of the Middle Ordovician epoch and was discovered near Saint Petersburg, Russia in the Koporka River deposits. It is 18.4 × 10 × 4.4 cm in size and has a mass of about 580 g.
Photo credit: Didier Descouens
