Furongian

The Furongian, also called the Late Cambrian, was the last part of the Cambrian period. It happened from 497 to about 487 million years ago. This time came after the Miaolingian and before the Lower Ordovician Tremadocian Stage.

During the Furongian, Earth saw many important changes in life. The world had many new sea creatures, and many groups of animals were evolving. Scientists split this time into three smaller parts, called stages: the Paibian, the Jiangshanian, and the unnamed 10th stage of the Cambrian. Learning about 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 was the last part of the Cambrian. It 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. 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. 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. They help us understand the order of events from long ago.

Major events

At the start of the Furongian epoch, the number of different species stopped dropping. Variety returned to earlier levels. Later, another drop happened, reducing variety by about half. After that, there were small changes until 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 sea level. During this time, special activity deep inside the Earth happened in a place that is now part of the Iberian Peninsula.

Paleontology

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

Later discoveries in South China helped scientists learn more about the rock layers and changes in the number of species during this time. Many fossils of trilobite-agnostoid animals were 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.