Key Words: Geologic Eras

Geologists and paleontologists use a system to measure time that relates to our Earth's rock layers. It helps scientists describe the timing and relationships between events that have occured during Earth's history. Time is measured in millions of years ago (MYA).

  • Protozoic (~2500-542 MYA)
    The first complex single-celluar and first multi-cellular life begins.
  • Paleozoic (~542-251 MYA)
    Complex muli-cellular life begins. The Cambrian is the first part of the Paleozoic era.
  • Mesozoic (~251-65.5 MYA)
    Dinosaurs are the dominant life form, so it is commonly called the Age of Dinosaurs.
  • Cenozoic (~65.5 MYA to present)
    Mammals diversify in the Cenozoic, so it is commonly called the Age of Mammals.

My Cambrian Aquarium

trilobite fossilWelcome to My Cambrian Aquarium, an interactive science website dedicated to the Cambrian period.

What is the Cambrian? It is the first part of the Paleozoic era in Earth’s geological history, which is the era preceding the Mesozoic era of dinosaur domination. It spans from 543 to 490 million years ago.

Why is the Cambrian period so important? It was in this brief span of Earth’s history that nearly all major animal groups first appeared. It’s also here that we see the development of skeletons and vertebrates. Because of this, the Cambrian is key to understanding the evolution of vertebrates, including humans. Cambrian fossils were first discovered in the Burgess Shale formation in Canada in 1909, and have since been found in the United States, China and other parts of the world.

Imagine what the Earth was like 500 million years ago. Scientists know from geological evidence that our planet was covered largely covered by shallow seas. At one time, the Earth's continents had been joined in a single super-continent. As the Cambrian began, the super-continent began to fragment into smaller continents, which do not always correspond to the ones we see today. Plants had not yet evolved, and the land was devoid of vegetation and inhospitable to life as we know it. However, ocean life was thriving. At this time, animals and especially vertebrates began to form ecological niches and become successful life forms.

Why is it called the Cambrian Explosion?

Almost all body plans for animals first appeared in the fossil record during the Cambrian period, in a relatively short span of only 53 million years.

cute anomalocarisLet's Explore the Cambrian

Click here to begin our journey in the Early Cambrian.

Or, use the "Explore" menu at the top of the page.