Miaolingian

The Miaolingian or Mid-Late Cambrian is the third Series of the Cambrian Period, and it was formally named in 2018. It lasted from about 506.5 to 497 million years ago and is divided into three stages: the Wuliuan, Drumian, and Guzhangian. This time period is important for understanding the development of many early animals and other life forms on Earth.

The Miaolingian comes after the unnamed Cambrian Series 2 and is followed by the Furongian series. It is named after the Miaoling Mountains in southeastern Guizhou Province, China. Studying this period helps scientists learn about how life evolved during one of Earth's most exciting times, the Cambrian Explosion, when many new types of animals first appeared in the oceans.

Definition

Before being officially named in 2018, several suggestions were made for important fossils to mark the start of this time period. Two main trilobite fossils, Ovatoryctocara granulata and Oryctocephalus indicus, were considered because they appeared close to 506.5 million years ago. Scientists chose Oryctocephalus indicus to mark the beginning, placing this marker in rock layers known as the Kaili Formation in Wuliu-Zengjiayan, Guizhou, China.

The end of the Miaolingian is marked by the appearance of another trilobite fossil called Glyptagnostus reticulatus, which appeared around 497 million years ago. This same marker also defines the start of the following time period, the Furongian, and is linked to the Paibian Stage.

Subdivision

The Miaolingian is divided into three main stages: the Wuliuan, Drumian, and Guzhangian. Before it, there was a stage called the Ordian, used in Australia, but scientists are still unsure if it belongs to the Miaolingian or the time just before it.

Major events

During the time when the Cambrian Series 2 ended and the Miaolingian began, a significant event happened to a group of ancient sea creatures called trilobites. Many types of trilobites, especially those from the families Ollenellidae and Redlichiidae, went extinct. This change happened in places like Laurentia and South China. After this extinction, a new trilobite named O. indicus appeared. In areas where fossils of O. indicus are not found, scientists use special chemical data to identify this boundary in Earth's history.

Paleontology

During the Miaolingian time period, graptolites—small, ocean-dwelling animals—spread widely across the seas. Two families of graptolites, called Rhabdopleuridae and Dithecodendridae, began to evolve early in this period. One common graptolite from the Wuliuan stage was Sphenoecium, known for its strong colonies found around the world.