A new effort to date the early history of modern animals finds a lot of evolutionary dawdling.
RISING DAWN The evolutionary extravaganza of the Cambrian period about 550 million years ago spawned early arthropods such as the Olenoides trilobite and the Sidneyia spider-cousin, immortalized here in Canada’s Burgess Shale.
Log in
Subscribers, enter your e-mail address for full access to the Science News archives and digital editions.
