Miaolingian

The Miaolingian is the third Series of the Cambrian Period, and was formally named in 2018. It lasted from about to  million years ago and is divided in ascending order into 3 stages: the Wuliuan, Drumian, and Guzhangian. The Miaolingian is preceded by the unnamed Cambrian Series 2 and succeeded by the Furongian series.

It is named after the Miaoling Mountains in southeastern Guizhou Province, China.

Definition
A number of proposals for fossils and type sections were made before it was formally ratified in 2018. The most promising fossil markers were seen to be the respective first appearances of either trilobite species Ovatoryctocara granulata or Oryctocephalus indicus, which both have an age close to million years ago. After some deliberation, the FAD of Oryctocephalus indicus was chosen to be the lower boundary marker, and the GSSP was placed in the Kaili Formation, Wuliu-Zengjiayan, Guizhou, China.

The Miaolingian-Furongian boundary has the same definition as the Paibian Stage. It is defined as the first appearance of Glyptagnostus reticulatus around million years ago.

Subdivision
The Miaolingian is subdivided into the following stages:

The Ordian stage, which is use in Australian chronostratigraphical scale, was originally supposed to be the lowest stage of the Miaolingian, but may belong to upper Series 2. As of 2024, the base of the Ordian is not defined yet.

Major events
At the Cambrian Series 2–Miaolingian boundary, the first major trilobite extinction, known as the Olenellid Biomere boundary, occurred. In particular, trilobites of the families Ollenellidae and Redlichiidae have been extinct in Laurentia and South China, respectively. The first O. indicus appear after this global extinction, and in areas where O. indicus fossils are absent, the Series 2–Miaolingian boundary is determined by chemostratigraphic data.

Paleontology
Benthic graptolites have reached a wide distribution in the Miaolingian. Encrusting colonies of the Rhabdopleuridae and erect growing branching colonies of the Dithecodendridae families evolved already at the beginning of the Miaolingian. The most common Wuliuan graptolite genus is Sphenoecium, whose robust colonies were found all over the world.