| 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 Homerian is a second and upper stage of the Wenlock series, corresponding to the Homerian age of the Wenlock epoch. It lasted from approximately 430.5 Ma to around 427.4 Ma (million years ago). It is preceded by the Sheinwoodian age of the Wenlock epoch and is followed by the Gorstian age of the Ludlow epoch.
Definition[]
The GSSP of the Homerian stage was ratified in 1980. The lower boundary is fixed within upper part of the Apedale Member of the Coalbrookdale Formation, Homer, UK, and related to the first appearance of the graptolite species Cyrtograptus lundgreni.[2]
Homerian life[]
Most animals lived in the seas. Numerous brachiopods (Dolerorthis, Isorthis, Salopina) and bivalves (Slava, Leptodesma, Rhombopteria) inhabited seabeds. Cephalopods, such as Dawsonoceras, hunted in water column. Graptolites like (Colonograptus, Spinograptus, Plectograptus) were distributed in seas around the world.
Among arthropods, trilobites were common. Various proetid (Radnoria, Harpidella), phacopid (Fragiscutum, Didrepanon, Sphaerexochus) and lichid (Hemiarges, Dicranogmus, Dicranopeltis) trilobites are known from the Homerian deposits of the Cornwallis Island, Canada. On land at that time, the inhabitants were mainly small myriapods (Pneumodesmus, Albadesmus, Cowiedesmus), scorpions and, possibly, early wingless insects.
Cowielepis
Conodonts, the toothy relatives of the vertebrates, remained a large group. Homerian genera include Panderodus, Hindeodella, Kockelella, Ozarkodina and Trichonodella. Various jawless fish (Thelodus, Oeselaspis, Tremataspis, Ariaspis, Vernonaspis) swam near the seabed and fed on detritus. Jawed fishes like Cowielepis were less common.
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.