More than half a billion years ago, the Grand Canyon was not the arid landscape we know today but a shallow, tropical sea ...

Paleozoic Era (541 - 252 million years ago) Cambrian Period (541 - 485 million years ago): Cambrian Explosion; rapid diversification of life, including the first hard-bodied organisms.

A 500-million-year-old sea squirt is the evolutionary clue we need to understand our humble beginnings With no teeth, bones, or shell, this ‘watery sack’ is a rare fossil find that tells us a ...

In places where sea-floor oxygen levels are a bit higher — about 0.5–3% of concentrations at the sea surface — animals are more abundant but their food webs remain limited: the animals still ...

The speed of transition seemed so shockingly abrupt that it amazed and worried even Charles Darwin. It has long been called the “Cambrian explosion." We now know it was not quite so abrupt.

These proxies seemed to indicate that oxygen concentrations in the oceans rose in several steps, approaching today's sea-surface concentrations at the start of the Cambrian, around 541 million ...

The Cambrian Explosion, a period in time when life on Earth diversified dramatically, was likely caused by several factors, including gene changes, sea level rise and an influx of calcium into the ...

Twenty million years after the Cambrian explosion, something lethal wiped out almost half of all sea life in the world. For years, it was believed that the mass death event was caused by low ...

The Cambrian explosion, as it is called, produced arthropods with legs and compound eyes, worms with feathery gills and swift predators that could crush prey in tooth-rimmed jaws.