Earth’s early animals moved upstream not long after conquering the seas, newly discovered fossils show.
Rocks near the California-Nevada border preserve traces of tiny worms that squiggled through river mud some 530 million years ago.
Earth’s early animals moved upstream not long after conquering the seas, newly discovered fossils show.
Rocks near the California-Nevada border preserve traces of tiny worms that squiggled through river mud some 530 million years ago.