Ludlow epoch

In the geological timescale, the Ludlow epoch (from 422.9 ± 2.5 million years ago to 418.7 ± 2.7 million years ago) occurred during the Silurian period, after the end of the Homerian age. It is named for the town of Ludlow in Shropshire, England.

The Ludlow epoch is subdivided into two stages: Gorstian and Ludfordian.

Paleontology

Arthropods

Arctinurus boltoni
Arctinurus boltoni

References

  1. ^ Jeppsson, L.; Calner, M. (2007). "The Silurian Mulde Event and a scenario for secundo—secundo events". Earth and Environmental Science Transactions of the Royal Society of Edinburgh. 93 (02): 135–154. doi:10.1017/S0263593300000377.
  2. ^ Munnecke, A.; Samtleben, C.; Bickert, T. (2003). "The Ireviken Event in the lower Silurian of Gotland, Sweden-relation to similar Palaeozoic and Proterozoic events". Palaeogeography, Palaeoclimatology, Palaeoecology. 195 (1): 99–124. doi:10.1016/S0031-0182(03)00304-3.
Arctinurus

Arctinurus boltoni is a large (up to 30 cm) lichid trilobite of the mid-Silurian. This trilobite reached about eight inches in length, though the normal adult carapace was about four inches. It lived in moderately deep-water in semi-tropical regions. Arctinurus fossils have been found in Europe and North America. Arctinurus was first reported during the construction of the Erie Canal through soft Silurian shales and mudstones in upstate New York. Before the late 1990s, complete Arctinurus fossils were very rare. The vast majority of complete specimens were commercially mined near Middleport New York, USA, in a shallow quarry in the Rochester Formation, and the trilobite is now relatively common in museum, university and private collections. Arctinurus tended to have epibionts attached to the carapace.

Carcinosoma

Carcinosoma (meaning "crab body") is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of Carcinosoma are restricted to deposits of late Silurian (Late Llandovery to Early Pridoli) age. Classified as part of the family Carcinosomatidae, which the genus lends its name to, Carcinosoma contains seven species from North America and Great Britain.

Carcinosomatid eurypterids had unusual proportions and features compared to other eurypterids, with a broad abdomen, thin and long tail and spined and forward-facing walking appendages. They were not as streamlined as other groups but had considerably more robust and well developed walking appendages. In Carcinosoma, these spined walking appendages are thought to have been used to create a trap to capture prey in. The telson (final segment of the body) of Carcinosoma appears to have possessed distinct segmentation, Carcinosoma is the only known eurypterid to possess this feature.

At 2.2 meters (7.2 ft) in length, the species C. punctatum is the largest carcinosomatoid eurypterid by far and is among the largest eurypterids overall, rivalling the large pterygotid eurypterids (such as Jaekelopterus) in size. Other species of the genus were considerably smaller, with most ranging from 70 centimeters (2.3 ft) to 100 centimeters (3.3 ft) in length.

Cyathaspis

Cyathaspis is the type genus of the heterostracan order Cyathaspidiformes. Species are found in late Silurian strata in Europe, especially in Great Britain and Gotland, Sweden. The living animal would have looked superficially like a tadpole, albeit covered in bony plates composed of the tissue aspidine, which is unique to heterostracan armor.

Cyathaspis ludensis is the earliest British vertebrate fossil. It was found in rocks at Leintwardine in Herefordshire, a noted fossil locality.

Elegestolepis

Elegestolepis is a primitive shark that lived during the Silurian and Devonian periods. It was closely related to Mongolepis and Polymerolepis. It is only known from placoid scales discovered in Russia before 1973. The oldest of these scales have been dated back to the Ludlow epoch (427.4 Ma to 423 Ma), making Elegestolepis the oldest known shark.Elegestolepis dates back to about four hundred and twenty million years ago, but some scales that may yet represent another shark ancestor are known from four hundred and fifty million years ago. Although the placoid scales of Elegestolepis are accepted to be those of a shark, subtle differences in the scales suggest that Elegestolepis itself may have been quite different in appearance to modern sharks. It is not known what Elegestolepis looked like.

Entelognathus

Entelognathus primordialis (“primordial complete jaw”) is a placoderm from the late Ludlow epoch of Qujing, Yunnan, 419 million years ago.A team led by Min Zhu of the Academy of Sciences' Institute of Vertebrate Paleontology and Paleoanthropology in Beijing discovered the intact, articulated fossil in rock formations at Xiaoxiang reservoir.

Eysyslopterus

Eysyslopterus is a genus of eurypterid, an extinct group of aquatic arthropods. Eysyslopterus is classified as part of the family Adelophthalmidae, the only clade within the derived ("advanced") Adelophthalmoidea superfamily of eurypterids. One fossil of the single and type species, E. patteni, has been discovered in deposits of the Late Silurian period (Ludlow epoch) in Saaremaa, Estonia. The genus is named after Eysysla, the Viking name for Saaremaa, and opterus, a traditional suffix for the eurypterid genera, meaning "wing". The species name honors William Patten, an American biologist and zoologist who discovered the only known fossil of Eysyslopterus.

Eysyslopterus is a little-known basal genus that was distinguished from the rest of adelophthalmids by the position near the head margin of the eyes, different from the rest of its relatives. Its carapace was parabolic (approximately U-shaped) and with transverse deep furrows forming the ornamentation. With an estimated length of 8 cm (3.1 in), Eysyslopterus was a small eurypterid. It lived in a nearshore lagoonal quiet community along other eurypterid species.

Gorstian

In the geologic timescale, the Gorstian is the age of the Ludlow epoch of the Silurian period of the Paleozoic era of the Phanerozoic eon that is comprehended between 422.9 ± 2.5 Ma and 421.3 ± 2.6 Ma (million years ago), approximately. The Gorstian age succeeds the Homerian age and precedes the Ludfordian age.

Longodus

Longodus is an extinct genus of thelodont, placed in its own family – Longopdidae – which existed in what is now Estonia during the Ludlow epoch of the upper Silurian period. The type and only species is Longodus acicularis.

Ludfordian

In the geologic timescale, the Ludfordian is the age of the Ludlow epoch of the Silurian period of the Paleozoic era of the Phanerozoic eon that occurred between 421.3 ± 2.6Ma and 418.7 ± 2.7 Ma (million years ago). The Ludfordian age succeeds the Gorstian age and precedes the Pridoli epoch. It is named for the town of Ludford in Shropshire, England.

The Lau event is a rapid pulse of cooling during the Ludfordian, about 420 million years ago; it is identified by a pulse of extinctions and oceanic changes. It is one of the series of fast sea-level and excursions in oxygen isotope ratios that signal fast switches between warm and cold climate states, characteristic of the Silurian climatic instability. The Lau Event occurred during an extended period of elevated seawater saturation state, explained by reservoirs of the planet's fresh water being locked up in massive polar ice caps. The sudden reappearance in normally saline marine environments of stromatolites and a mass occurrence of oncoids during the event suggested that minor extinction events like the Lau Event also resulted in periods of reduced grazing pressures on surviving "disaster biota", which can be compared to the aftermath of the more catastrophic end-Ordovician and end-Permian mass extinctions.

Ludlow Group

The Ludlow Group are geologic formations deposited during the Ludlow epoch of the Silurian period in the British Isles, in areas of England, Ireland, Scotland, and Wales.

Metacalymene

Metacalymene is a genus of trilobites in the order Phacopida, family Calymenidae. This genus is considered monotypic, containing only the type species:

Metacalymene baylei Barrande, 1846.These trilobites were nektobenthic detritivore. They lived in the Silurian period in the Ludlow epoch, from 422.9 ± 1.5 to 418.7 ± 2.8 million years ago.

Ornatifilum

Ornatifilum (Latin ornatus + filum, Ornamented filament) is an artificial form genus, which is used to categorise any small, branched filaments with external ornamentation.

It has been applied to microfossils of Devonian age with fungal affinities, though these taxa have since been recognized as an early growth form of Tortotubus.

Planiscutellum

Planiscutellum is a genus of trilobites in the order Corynexochida family Styginidae. These trilobites were nektobenthic detritivore. They lived in the Silurian period in the upper Ludlow epoch, from 422.9 ± 1.5 to 418.7 ± 2.8 million years ago.

Pneumodesmus

Pneumodesmus newmani is a species of millipede that lived in the Paleozoic. Its exact age is uncertain. It was originally interpreted as living 428 million years ago, in the Late Silurian; however, the study conducted by Suarez et al. (2017) indicates that it actually lived in the Early Devonian (Lochkovian). It is the first myriapod, and the oldest known creature to have lived on land. It was discovered in 2004, and is known from a single specimen from Stonehaven, Aberdeenshire, Scotland.

Qilinyu

Qilinyu rostrata is a "maxillate" placoderm from the late Ludlow epoch of Qujing, Yunnan, 419 million years ago.

Reston Group

The Reston Group is a Silurian to Devonian lithostratigraphic group (a sequence of rock strata) in the Southern Uplands terrane of southern Scotland and northernmost England. The name is derived from Reston in the Scottish Borders. The rocks of the Reston Group have also previously been referred to as 'Lower Old Red Sandstone and Lavas'

Tylopterella

Tylopterella is a genus of eurypterid, a group of extinct aquatic arthropods. Only one fossil of the single and type species, T. boylei, has been discovered in deposits of the Late Silurian period (Ludlow epoch) in Elora, Canada. The name of the genus is composed by the Ancient Greek words τύλη (túlē), meaning "knot", and πτερόν (pteron), meaning "wing". The species name boylei honors David Boyle, who discovered the specimen of Tylopterella.

It is a poorly-known genus whose carapace (dorsal plate of the prosoma, head) was semiovate bordered by a marginal rim, with eyes laterally placed, a preabdomen and postabdomen (the two halves of the abdomen) with six segments each and a short spike-like telson ("tail"). It reached a total length of 7.5 centimetres (2.9 inches). These characteristics place Tylopterella in the family Onychopterellidae together with Onychopterella and Alkenopterus.

Tylopterella is notable for its thick ornamentation and general body surface. Its paired tubercles or knobs in the top of its second to fifth segments differentiates it from many other eurypterids. This thickness that its body possessed is due to the highly saline conditions to which Tylopterella had to adapt in the Guelph Formation; other organisms with reinforced shells have also been found in the same place.

Wenlock epoch

The Wenlock (sometimes referred to as the Wenlockian) is the second series of the Silurian. It is preceded by the Llandovery epoch and followed by the Ludlow Group. Radiometric dates constrain the Wenlockian between 433.4 and 427.4 million years ago.

Wills Creek Formation

Wills Creek Formation is a mapped Silurian bedrock unit in Pennsylvania, Maryland, Virginia, and West Virginia.

Cenozoic era
(present–66.0 Mya)
Mesozoic era
(66.0–251.902 Mya)
Paleozoic era
(251.902–541.0 Mya)
Proterozoic eon
(541.0 Mya–2.5 Gya)
Archean eon (2.5–4 Gya)
Hadean eon (4–4.6 Gya)

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