Jiangshanian

The Jiangshanian is an important time period in Earth's history, part of the middle section of the Furongian series. It came after the Paibian Stage and was followed by another stage called Stage 10 during the Cambrian period.

Scientists mark the start of the Jiangshanian by the first appearance of a special kind of trilobite called Agnostotes orientalis. This happened about 494.2 million years ago, and the Jiangshanian lasted until around 491 million years ago.

This stage is named after the city of Jiangshan in Zhejiang province, China. Scientists chose this place to mark the start of this time in the fossil record. The Jiangshanian helps us learn about how life on Earth was changing during this part of the Cambrian explosion, when many new animals were appearing in the oceans.

Stratigraphy

The Jiangshanian is a middle stage of the Furongian series in the Cambrian period. It began about 494.2 million years ago when a trilobite called Agnostotes orientalis first appeared.

Scientists chose a place called the Duibian B Section, west of the village of Duibian and north of Jiangshan, to define this stage. Another possible location near the Kyrshabakty River in southern Kazakhstan was suggested but is still being discussed.

Major events

At the start of the Jiangshanian time, many new species appeared, similar to what happened in the middle of the Guzhangian. After this, a period called the Jiangshanian extinction began, lasting from about 493.9 to 491.3 million years ago. This event caused many species to disappear. After that, there were smaller changes in the number of species until the start of the Ordovician period.

Paleontology

Scientists found about 50 different groups of ancient animals and plants from the Jiangshanian time period. These fossils come from places like the Sandu Formation in Guangxi, South China, and the Wiśniówka Sandstone Formation in Poland. The fossils include simple plants called algae, small sea animals called graptolites, and many types of arthropods. Arthropods are animals with hard outer shells and jointed legs, like aglaspidid and mollisoniid forms.

Fossils of trilobites, which are extinct sea creatures with hard shells, have also been found. They were found in places such as western Tasmania and the Wichita Mountains in Oklahoma, USA. Some of the trilobite groups found include Parabolina, Hedinaspis, Eugonocare, and Cermatops. These discoveries help scientists learn about the world from millions of years ago.