Paibian

The Paibian was the earliest time period of the Furongian Series in the Cambrian System, which is part of Earth's ancient history. It marks the beginning of the Furongian Epoch during the Cambrian Period. This time period came after the Guzhangian Stage and was followed by the Jiangshanian Stage.

Scientists define the start of the Paibian by looking for a special kind of small sea creature called a trilobite, named Glyptagnostus reticulatus. This trilobite first appeared about 497 million years ago, signaling the beginning of the Paibian. The end of the Paibian, and the start of the Jiangshanian Stage, is marked by the appearance of another trilobite called Agnostotes orientalis, which happened around 494.2 million years ago.

The Paibian helps scientists understand how life was changing on Earth millions of years ago during the Cambrian explosion, a time when many new kinds of animals were appearing in the oceans. Studying this period gives us clues about the early history of life and how Earth’s ecosystems developed long ago.

GSSP

The name comes from Paibi, a village in Hunan, China. The Global Boundary Stratotype Section and Point (GSSP) is found in the Paibi section in the Wuling Mountains, near Huayuan County. It is marked by the first appearance of a specific fossil called Glyptagnostus reticulatus, which is located 396 meters above the start of the Huaqiao Formation at the main location.

Major events

At the time between the Guzhangian and Paibian ages, many kinds of animals disappeared, reducing the number of species by about 45%. This change happened at the same time as a big drop in life called the Marjuman extinction, which scientists can see in fossils of trilobites and brachiopods in Laurentia. There were two parts to this drop in species: a smaller one during the Guzhangian, lasting about 1.8 million years, and a bigger one during the Paibian, lasting 1.2 million years. After this, the number of species slowly went back to what it was before.

Around the time the Guzhangian turned into the Paibian, something called the Steptoean positive carbon isotope excursion began. This was a big change in the amount of carbon in the world. Scientists think it happened because deep water without oxygen moved into shallower parts of the ocean. This change affected trilobites, causing their numbers to drop at the start and end of this period. Even though the world cooled a bit after this started, which helped life come back, later warming made things harder for ocean life again.

Paleontology

The Paibian time period is known for fossils of small sea creatures called agnostoid genera. Some important ones are Glyptagnostus, Homagnostus, Pseudagnostus, and Acmarhachis. These fossils help scientists learn about life from very long ago.