Furongian

The Furongian, also known as the Late Cambrian, was the fourth and final part of the Cambrian period. It lasted from 497 to about 487 million years ago. This time came after the Miaolingian series and before the Lower Ordovician Tremadocian Stage.

During the Furongian, Earth saw many important changes in life. The world was filled with many new kinds of sea creatures, and many different groups of animals were evolving and changing. Scientists divide this time into three smaller parts, called stages: the Paibian, the Jiangshanian, and the unnamed 10th stage of the Cambrian. Studying the Furongian helps us understand how life on our planet developed long ago.

History and naming

The Furongian was also called Cambrian Series 4. It replaced an older name, Upper Cambrian, and is similar to a local name Hunanian. The name was officially approved by the International Commission on Stratigraphy in 2003. The word Fúróng (芙蓉) means 'lotus' in Mandarin and connects to Hunan, a place known as the "lotus state".

Definition

The Furongian, also called the Late Cambrian, began around 497 million years ago when a special kind of trilobite called Glyptagnostus reticulatus first appeared. This marks the start of this time period. The Furongian ended around 486.85 million years ago when another ancient creature, a conodont named Iapetognathus fluctivagus, first showed up. This period was the last part of the Cambrian time.

Main article: GSSP
Main articles: Paibian Stage, Tremadocian Stage

Subdivisions

The Furongian, also called the Late Cambrian, was the last part of the Cambrian period. It lasted from about 497 to 486.85 million years ago. This time came after the Miaolingian series and before the Lower Ordovician Tremadocian Stage.

The table below shows how scientists divide this time period into smaller parts:

Biostratigraphy

The Furongian period, which was the last part of the Cambrian, is split into stages based on when certain ancient sea creatures, called trilobites, first appeared. The start of the Paibian stage is marked by the first appearance of a trilobite named Glyptagnostus reticulatus, and the start of the Jiangshanian stage is marked by the first appearance of another trilobite named Agnostotes orientalis. The final stage, called Cambrian Stage 10, has not yet been fully named, but it may be defined by the first appearance of either Lotagnostus americanus or a tiny tooth-like fossil called Eoconodontus notchpeakensis.

During the Furongian, scientists can identify different time periods by looking at layers of rock that contain specific trilobite species. These layers are known as trilobite zones, which help us understand the order of events from long ago.

Major events

At the start of the Furongian epoch, a big drop in the number of different species ended. The amount of variety returned to what it was before. Later, another drop happened, reducing the variety by about half. After that, there were small changes until the time of the Ordovician began.

There was also an important change in the carbon in rocks near the start of the Furongian. Scientists aren't sure why this happened, but they think it might be related to big changes in the ocean or the level of the sea. During this time, special activity deep inside the Earth happened in a place that is now part of the Iberian Peninsula.

Paleontology

Scientists have noticed that many important soft-bodied animals from a time between the Cambrian Explosion and the Great Ordovician Biodiversification Event were not found for a long time. In 2019, this missing period was named the Furongian Biodiversity Gap. This gap might be due to fewer rocks from that time, special environmental conditions, or extreme weather. However, studying areas with Cambrian rocks showed that the gap happened because not enough Furongian rock layers had been examined closely enough, and not enough attention was given to fossils from this time.

Later discoveries in South China helped scientists learn more about the layers of rock and changes in the number of species during this time. Many fossils of trilobite-agnostoid animals have been found in Furongian rock layers in the Alum Shale Formation of Bornholm, Denmark. These include animals like Ctenopyge, Eurycare, Leptoplastus, Olenus, Parabolina, Peltura, Protopeltura, Sphaerophthalmus, Lotagnostus, and Triangulopyge. Benthic graptolites, such as Rhabdopleura, Dendrograptus, Callograptus, and Siberiograptus, were also found in Furongian rocks in South China.