Cambrian Stage 10

Stage 10 of the Cambrian is the last part of the Furongian series. It comes after the Jiangshanian and before the Ordovician Tremadocian Stage.

Scientists think the start of Stage 10 is when a special trilobite called Lotagnostus americanus first appeared. This trilobite lived about 491 million years ago. They also study other fossils to help define this time.

The end of Stage 10 is marked by a tiny fossil called a conodont named Iapetognathus fluctivagus. This helps scientists know when the Tremadocian Stage of the Ordovician began, around 486.85 million years ago. Studying these fossils helps us learn how life on Earth changed long ago.

Naming

The 10th stage of the Cambrian does not yet have an official name from the ICS. Some scientists call it the "Lawsonian," after Lawson Cove in the Wah Wah Mountains in Utah. Another name is the North American Skullrockian Stage. In 2011, a third name, "Nelegerian," was suggested, after the Neleger River in Yakutia.

Stratotype

The ICS is still deciding which rock layer and fossil marker will define the start of the 10th Cambrian stage.

One suggestion was a site near Duibian in Zhejiang, China. But many scientists now prefer a site called Steamboat Pass in the House Range of Utah. If they use a special type of ancient tooth called a conodont, many more places could work, like sites in Australia, Kazakhstan, and Canada. Scientists are looking at different fossils, such as the first appearance of a type of trilobite called Lotagnostus americanus, or another ancient tooth called Cordylodus andresi. Many like the idea of using Eoconodontus notchpeakensis because it can be found all over the world.

Subdivisions

Cambrian Stage 10 can be split into smaller parts using different types of ancient sea life. Scientists study tiny teeth from ancient sea creatures called conodonts to help sort these parts. They also look at trilobites, which were like bugs with hard shells, to learn more about this stage.

Cambrian Stage 10