| 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 Ludfordian is a second and upper stage of the Ludlow series, corresponding to the Ludfordian age of the Ludlow epoch. It lasted from approximately 425.6 Ma to around 423.0 Ma (million years ago). It is preceded by the Gorstian and is followed by the Pridoli.
Definition[]
The GSSP of the Ludfordian stage was ratified in 1980. The lower boundary is fixed in the section near Ludlow, UK, and approximately related to base of Saetograptus leintwardinensis Graptolite zone.[2]
Ludfordian life[]
Most life developed in the seas. The seabed was covered with numerous bivalves like Solemya, Pterinea, Fuchsella and Goniophora. Various orthoceratoid cephalopods such as Orthoceras, Paraphragmites, Michelinoceras and Leurocycloceras swam in the water column.
There were still many trilobites among arthropods. Cheirurus and Ananaspis, members of the order Phacopida, were found in the Ludfordian strata of Alticola Limestone, Cellon-Lawineriss section, Austria. Eurypterids remained varied and numerous, from relatively small members like Erettopterus and some species of Pterygotus to large Carcinosoma that reached 2 m in length.
Numerous small jawless fish like Phlebolepis, Gomphodus and Thelodus fed on detritus. The number of jawed fish has increased noticeably. Andreolepis and Nostolepis are known from the Ludfordian of the upper Hemse beds at Gogs in Sweden.
Land animals of that time remained few in number and therefore are not studied well enough. In the Ludfordian strata of Wales, the fossil fragments of scorpions are known.[3] It can be assumed that primitive terrestrial hexapods already existed then.
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.
- ↑ J. A. Dunlop, P. A. Selden (2013). "Scorpion fragments from the Silurian of Powys, Wales". Arachnology 16 (1): pp. 27-32 DOI:10.13156/arac.2013.16.1.27