| 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 Sheinwoodian is a first stage of the Wenlock series, corresponding to the Sheinwoodian age of the Wenlock epoch. It lasted from approximately 433.4 Ma to around 430.5 Ma (million years ago). It is preceded by the Telychian age of the Llandovery epoch and is followed by the Homerian age of the Wenlock epoch.
Definition[]
The GSSP of the Sheinwoodian stage and the whole Wenlock series was ratified in 1980. The lower boundary is fixed in the base of the Buildwas Formation in Hughley Brook, UK, and approximately related to the base of the Cyrtograptus murchisoni Graptolite Biozone.[2]
Sheinwoodian life[]
Most life forms lived in the seas. Numerous gastropod shells are known from the Sheinwoodian. Genera include Poleumita, Ruedemannia, Promourlonia, Prosolarium, Cyrtostropha and Platyosoma. Straight-shelled cephalopods like Orthoceras hunted in the water column. Trilobites remained relatively numerous. Various Odontopleurid (Taemasaspis, Laethoprusia, Ceratocephala, Edgecombeaspis), proetid (Pseudogerastos, Gerastos, Westropia, Scharyia) and phacopid (Homalonotus, Dalmanites, Phacopidella, Encrinurus) genera are known from the Sheinwoodian sediments. Numerous ostracods (Dizygopleura, Beyrichia, Dibolbina, Mastifobolbina) inhabited coastal waters and the open ocean. Eurypterids such as Dolichopterus, Erettopterus, Eurypterus and Holmipterus hunted in shallow waters. At that time, arachnids, their close relatives, had already appeared. Palaeophonus is one of the oldest known scorpions. Primitive myriapods already lived in land, near fresh water bodies.
Conodonts like Paltodus and Hindeodella lived in the shallow seas. Various jawless galeaspids (Meishanaspis, Sinogaleaspis, Xiushuiaspis, Changxingaspis) probably fed on detritus. There was an evolution of jawed fishes, including the recently appeared cartilaginous fishes like Sinacanthus.
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.