Cambrian Stage 10

Stage 10 of the Cambrian is the last and still-unnamed part of the Furongian series. It comes after the Jiangshanian and right before the Ordovician's Tremadocian Stage. Scientists look for a special trilobite called Lotagnostus americanus to mark the start of this stage, which happened about 491 million years ago. They are also studying other fossils to help define this boundary. The end of Stage 10 is marked by the appearance of a conodont named Iapetognathus fluctivagus, which signals the beginning of the Tremadocian about 486.85 million years ago. This stage is important for understanding the changes in life on Earth during this ancient time.

Naming

The 10th stage of the Cambrian has not yet been given an official name by the ICS, though several local names are used. Some scientists suggest calling it the "Lawsonian" after Lawson Cove in the Wah Wah Mountains of Utah. Another name, the Skullrockian Stage, also refers to part of this time period in North America. In 2011, a third name, "Nelegerian", was proposed, named after the Neleger River in Yakutia.

Stratotype

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

One suggestion was a site near Duibian in Zhejiang, China. But now, many experts prefer Steamboat Pass in the House Range of Utah. If they use a special type of ancient creature called a conodont, many more places could work, like sites in Australia, Kazakhstan, and Canada. Scientists are looking at different ancient animals, such as the trilobite Lotagnostus americanus or conodonts like Cordylodus andresi and Eoconodontus notchpeakensis, to mark the beginning of this stage. The appearance of Eoconodontus notchpeakensis is popular because it is found all over the world and does not change much in different environments.

Subdivisions

Cambrian Stage 10 can be divided into smaller parts using different groups of fossils. Scientists look at special types of conodonts and trilobites to help sort these smaller parts. These fossils help tell us more about the order of layers in the rock and what life was like during this time.