Jiangshanian

The Jiangshanian is an important time period in Earth's history. It is the middle part of the Furongian series, which belongs to the early part of the Cambrian period, a time when many early animals first appeared. The Jiangshanian comes after the Paibian Stage and is followed by an unnamed stage called Stage 10.

This stage is defined by the first appearance of a special kind of trilobite called Agnostotes orientalis. Scientists estimate this happened about 494.2 million years ago. The Jiangshanian period lasted until around 491 million years ago.

The name Jiangshanian comes from the city of Jiangshan in Zhejiang province, China. This is where scientists chose to define this important time in Earth's past, helping us understand how life developed long ago.

Stratigraphy

The Jiangshanian is a middle stage of the Furongian series in Earth's history. It follows the Paibian Stage and comes before the still unnamed Stage 10 of the Cambrian. The start of this stage is marked by the first appearance of a type of ancient sea creature called a trilobite, which scientists estimate happened about 494.2 million years ago.

Researchers have studied this stage in different places around the world. One important location is near a village called Duibian, west of the town of Jiangshan. Another suggested location is in southern Kazakhstan, near a river called Kyrshabakty. These places help scientists understand how layers of rock from this time period fit together.

Major events

At the start of the Jiangshanian time period, there was a lot of different species living, similar to what was seen in the middle of the Guzhangian. After that, a period called the Jiangshanian extinction happened, lasting from about 493.9 to 491.3 million years ago. This event reduced the number of species by about 55%. Following this, there were small changes in the number of species until the beginning of the Ordovician period.

Paleontology

Scientists have discovered nearly 50 different groups of ancient life in the Jiangshanian time layer in the Sandu Formation of Guangxi, in South China. These fossils include simple plants called algae, small sea animals named graptolites, and many types of small sea creatures like arthropods. They also found rare fossils in places like Poland.

In other areas, such as western Tasmania and the Wichita Mountains in Oklahoma, USA, scientists found fossils of trilobites — these were small sea animals with hard shells. Many different kinds of trilobites have been uncovered from this time period.