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The PaleozoicEra is the earliest of three geologic eras of the Phanerozoic Eon. The name Paleozoic was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words palaiós and zōḗ, "life", meaning "ancient life").
The Silurian is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at 443.8 million years ago (Mya), to the beginning of the Devonian Period, 419.2 Mya. The Silurian is the shortest period of the Paleozoic Era. As with other geologic periods, the rock beds that define the period's start and end are well identified, but the exact dates are uncertain by a few million years. The base of the Silurian is set at a series of major Ordovician–Silurian extinction events when up to 60% of marine genera were wiped out.
The Silurians are a race of reptilian humanoids in the long-running British science fiction television series Doctor Who. The species first appeared in Doctor Who in the 1970 serial Doctor Who and the Silurians, and were created by Malcolm Hulke. The first Silurians introduced are depicted as prehistoric and scientifically advanced sentient humanoids who predate the dawn of man; in their backstory, the Silurians went into self-induced hibernation to survive what they predicted to be a large atmospheric upheaval caused by the Earth capturing the Moon.
Doctor Who and the Silurians is the second serial of the seventh season in the British science fiction television series Doctor Who. It was first broadcast in seven weekly parts on BBC1 from 31 January to 14 March 1970.
In the geologic timescale, the Ludfordian is the upper of two chronostratigraphic stages within the Ludlow Series. Its age is the late Silurian Period, and within both the Palaeozoic Era and Phanerozoic Eon. The rocks assigned to the Ludfordian date to between 425.6 ± 0.9 Ma and 423.0 ± 2.3 Ma. The Ludfordian Stage succeeds the Gorstian Stage and precedes the Pridoli Epoch. It is named for the village of Ludford in Shropshire, England. The GSSP for the Ludfordian is represented as a thin shale seam, coincident with the base of the Leintwardine Formation, overlying the Bringewood Formation in England.
In the geologic timescale, the Gorstian is an age of the Ludlow Epoch of the Silurian Period of the Paleozoic Era of the Phanerozoic Eon that is comprehended between 427.4 ± 0.5 Ma and 425.6 ± 0.9 Ma, approximately. The Gorstian Age succeeds the Homerian Age and precedes the Ludfordian Age. The age is named after Gorsty village southwest of Ludlow. The base of the age is marked by Graptolites tumescens and Graptolites incipiens. The type section is located in a quarry in the Elton Formation at Pitch Coppice, Shropshire, United Kingdom.
In the geologic timescale, the Homerian is an age of the Wenlock Epoch of the Silurian Period of the Paleozoic Era of the Phanerozoic Eon that is comprehended between 430.5 ± 0.7 Ma and 427.4 ± 0.5 Ma, approximately. The Homerian Age succeeds the Sheinwoodian Age and precedes the Gorstian Age.
In the geologic timescale, the Sheinwoodian is the age of the Wenlock Epoch of the Silurian Period of the Paleozoic Era of the Phanerozoic Eon that is comprehended between 433.4 ± 0.8 Ma and 430.5 ± 0.7 Ma, approximately. The Sheinwoodian Age succeeds the Telychian Age and precedes the Homerian Age.
In the geologic timescale, the Telychian is the age of the Llandovery Epoch of the Silurian Period of the Paleozoic Era of the Phanerozoic Eon. The Telychian Age was between 438.5 ± 1.2 million years ago (Ma) and 433.4 ± 0.8 Ma. The Telychian Age succeeds the Aeronian Age and precedes the Sheinwoodian Age. The name of the interval is derived from the Pen-lan-Telych Farm near Llandovery, Powys, Wales. The GSSP is located within the Wormwood Formation.
In the geologic timescale, the Rhuddanian is the first age of the Silurian Period and of the Llandovery Epoch. The Silurian is in the Paleozoic Era of the Phanerozoic Eon. The Rhuddanian Age began 443.8 ± 1.5 Ma and ended 440.8 ± 1.2 Ma. It succeeds the Himantian Age and precedes the Aeronian Age.
In the geological timescale, the Ludlow Epoch occurred during the Silurian Period, after the end of the Homerian Age. It is named for the town of Ludlow in Shropshire, England.
In the geological timescale, the Llandovery Epoch occurred at the beginning of the Silurian Period. The Llandoverian Epoch follows the massive Ordovician-Silurian extinction events, which led to a large decrease in biodiversity and an opening up of ecosystems.
The Lau event was the last of three relatively minor mass extinctions during the Silurian period. It had a major effect on the conodont fauna, but barely scathed the graptolites, though they suffered an extinction very shortly thereafter termed the Kozlowskii event that some authors have suggested was coeval with the Lau event and only appears asynchronous due to taphonomic reasons. It coincided with a global low point in sea level caused by glacioeustasy and is closely followed by an excursion in geochemical isotopes in the ensuing late Ludfordian faunal stage and a change in depositional regime.
In the geologic timescale, the Přídolí Epoch is the uppermost subdivision of the Silurian Period, dated at between 423 ± 2.3 and 419.2 ± 3.2 mya. The Přídolí Epoch succeeds the Ludfordian Stage and precedes the Lochkovian, the lowest of three stages within the Lower Devonian geological epoch. It is named after one locality at the Homolka a Přídolí nature reserve near the Prague suburb, Slivenec, in the Czech Republic. The GSSP is located within the Požáry Formation, overlying the Kopanina Formation. Přídolí is the old name of a cadastral field area.
"Cold Blood" is the ninth episode in the fifth series of British science fiction television series Doctor Who, which was first broadcast on 29 May 2010 on BBC One. It was written by Chris Chibnall and directed by Ashley Way. It is the second episode of a two-part story, the first episode being "The Hungry Earth", which features the return of the reptilian humanoid Silurians.
"The Hungry Earth" is the eighth episode of the fifth series of the British science fiction television series Doctor Who, which was first broadcast on 22 May 2010 on BBC One. It was written by Chris Chibnall, who had previously written for Doctor Who and its spin-off series, Torchwood. It is the first episode of a two-part story, the second episode being "Cold Blood", and features the return of the Silurians, a reptile-like humanoid race last seen in 1984's Warriors of the Deep.
The Brassfield Formation, named by A.F. Foerste in 1906, is a limestone and dolomite formation exposed in Arkansas, Ohio, Kentucky, Indiana, Tennessee and West Virginia in the United States. It is Early Silurian in age and well known for its abundant echinoderms, corals and stromatoporoids. In Ohio, where the unit has escaped dolomitization, the Brassfield is an encrinite biosparite with numerous crinoid species.
The Wenlock is the second epoch of the Silurian. It is preceded by the Llandovery Epoch and followed by the Ludlow Epoch. Radiometric dates constrain the Wenlockian between 433.4 and 427.4 million years ago.
Kockelellidae is an extinct conodont family.
Distomodus is an extinct genus of conodonts.
References
- ↑ Occurrence of Kockelella variabilis Walliserin the Aymestry Limestone of Shropshire. F. H. T. Rhodes & G. Newall, Nature 199, 166 - 167 (13 July 1963); doi:10.1038/199166a0
- ↑ Taxonomy and evolution of Kockelella (Conodonta) from Silurian of Sardinia. Enrico Serpagli and Carlo Corradini, Bollettino della Societa Paleontologica Italiana, 01/1999; 38(2), pages 275-298
