Wuliuan

The Wuliuan is an important time period in Earth's history. It was the fifth stage of the Cambrian period and the first stage of the Miaolingian Series. Scientists defined it in 2018.

The start of the Wuliuan is marked by the first appearance of a special trilobite called Oryctocephalus indicus. It ends when another trilobite, Ptychagnostus atavus, first appears, about 504.5 million years ago.

The exact spot that marks the beginning of the Wuliuan is in the Wuliu-Zengjiayan section of the Kaili formation, near Balang Village in the Miaoling Mountains of Guizhou, China. This spot is called the 'golden spike'. It helps scientists identify this important time in Earth's past.

GSSP

Three places were looked at to mark the start of the Wuliuan stage: near Balang in Guizhou province (China), Split Mountain in Nevada (USA), and along the Molodo river in Russia. In 2018, scientists chose the Wuliu-Zengjiayan section in China as the official spot. They picked the first appearance of a trilobite called Oryctocephalus indicus to show the beginning of this stage.

Major events

The Wuliuan stage is an important time for tiny sea creatures called trilobites. During this time, a group of trilobites called the Olenellids disappeared. This change in ancient sea life happened at the same time as a shift in the chemistry of carbonate rocks.

Paleontology

During the Wuliuan time, many different kinds of ancient sea creatures lived and left fossils behind. One group, called graptolites, became very diverse. We also know of many other sea animals from this time, such as trilobites, agnostoids, hurdiids, and bradoriids. They all lived in the oceans long ago.