| System (period) | Series | Stage (age) | Lower boundary, Ma | |
|---|---|---|---|---|
| Devonian | Lower | Lochkovian | 419.2±3.2 | |
| Silurian | Pridoli |  423.0±2.3
| ||
| Ludlow | Ludfordian | 425.6±0.9
| ||
| Gorstian | 427.4±0.5
| |||
| Wenlock | Homerian | 430.5±0.7
| ||
| Sheinwoodian | 433.4±0.8
| |||
| Llandovery | Telychian | 438.5±1.1
| ||
| Aeronian | 440.8±1.2
| |||
| Rhuddanian | 443.8±1.5
| |||
| Ordovician | Upper | Hirnantian | older | |
| Subdivisions and "golden spikes" according to IUGS as of September 2023[1] | ||||
The Telychian is a third and upper stage of the Llandovery series, corresponding to the Telychian age of the Llandovery epoch. It lasted from approximately 438.5 Ma to around 433.4 Ma (million years ago). It is preceded by the Aeronian age of the Llandovery and is followed by the Sheinwoodian age of the Wenlock. The earliest arachnids and cartilaginous fish are known from this stage.
Definition[]
The GSSP of the Telychian stage was ratified in 1984. The lower boundary is fixed in the Cefn-cerig Road Section within the Wormwood Formation in Wales, UK, between the last appearance of the brachiopod species Eocoelia intermedia and the first appearance of Eocoelia curtisi.[2]
Telychian life[]
Life was still concentrated in the seas. At this time, a huge number of brachiopods lived. They differ from bivalves by having an upper and lower valve, rather than a right and left one. Telychian brachiopod genera include Lingula, Striispirifer, Eospirifer, Nucleospira and Nalivkinia. Like brachiopods, gastropods (Coelozone, Hormotoma) lived on the seabed. Numerous orthocerids from the group of Cephalopoda hunted in the water column. All of them, including Geisonoceras, had hard external shells, which are found in abundance in fossils.
Stoermeropterus
Trilobites were not rare in the seas, although their taxonomic diversity noticeably decreased compared to the Ordovician. Such trilobites as Cyphoproetus, Encrinurus, Cheirurus and Ktenoura lived in the open ocean. The number of eurypterids increased, and many genera are known from the Telychian. They include Drepanopterus, Parastylonurus, Hardieopterus, Laurieipterus and Stoermeropterus. Bembicosoma, a bizarre relative of eurypterids, was found in a Telychian offshore sandstone in the United Kingdom. Other group related to eurypterids is Arachnida, and scorpions, the earliest arachnids, already existed in the Telychian. Dolichophonus is the oldest scorpion known by fossils, and it was discovered in the same strata as Bembicosoma.
Fish have also evolved actively. Among primitive jawed fish, the new group appeared. Sinacanthus, the oldest known chondrichthyan (cartilaginous fish), was found in the Telychian sediments of China.
References[]
- ↑ "Latest version of international chronostratigraphic chart". International Commission on Stratigraphy. https://stratigraphy.org/chart#latest-version.
- ↑ "GSSP Table - Paleozoic Era". https://timescalefoundation.org/gssp/index.php?parentid=77.