Furongian

The Furongian is the fourth and final series of the Cambrian. It lasted from 497 to 485.4 million years ago. It succeeds the Miaolingian series of the Cambrian and precedes the Lower Ordovician Tremadocian stage. It is subdivided into three stages: the Paibian, Jiangshanian and the unnamed 10th stage of the Cambrian.[1]

Naming

The Furongian was also known as the "Series 4" of the Cambrian and replaced the older term "Upper Cambrian" and equivalent to the local term "Hunanian". The name "Furongian" was ratified by the International Commission on Stratigraphy in 2003. Furong (芙蓉) means "lotus" in Mandarin and refers to Hunan which is known as the "lotus state".[2]

Definition

The lower boundary is defined in the same way as the GSSP of the Paibian stage. Both begin with the first appearance of the trilobite Glyptagnostus reticulatus around 497 million years ago.[3] The upper boundary is the lower boundary and GSSP of the Tremadocian stage which is the first appearance of the conodont Iapetognathus fluctivagus around 485.4 million years ago.[4]

Subdivisions

The following table shows the subdivisions of the Furongian series/epoch:[1]

Epoch Stage Age (mya)
Lower Ordovician
Floian 477.7
Tremadocian 485.4
Furongian
Stage 10 489.5
Jiangshanian 494
Paibian 497
Series 3
Guzhangian 500.5
Drumian 504.5
Stage 5 509

Biostratigraphy

The base of two of three stages of the Furongian are defined as the first appearance of a trilobite. The base of the Paibian is the first appearance of Glyptagnostus reticulatus and the base of the Jiangshanian is the first appearance of Agnostotes orientalis.[2][5] The still unnamed Cambrian Stage 10 might be defined as the first appearance of Lotagnostus americanus or the conodont Eoconodontus notchpeakensis.[6]

The Furongian can be divided into a number of trilobite zones:

Series Stage Trilobite zone Trilobite GSSP
Furongian Stage 10 Saukia zone (upper part), Eurekia apopsis zone, Tangshanaspis Zone, Parakoldinioidiazone, Symphysurina zone[6] Lotagnostus americanus (undecided)
Jiangshanian Ellipsocephaloides zone, Saukia zone (lower part)[6] Agnostotes orientalis
Paibian ? (?) Glyptagnostus reticulatus
Cedaria

References

  1. ^ a b "GSSP Table - Paleozoic Era". Geologic Timescale Foundation. Retrieved 17 November 2012.
  2. ^ a b Peng, Shanchi; Babcock, Loren; Robison, Richard; Lin, Huanling; Rees, Margaret; Saltzman, Matthew (30 November 2004). "Global Standard Stratotype-section and Point (GSSP) of the Furongian Series and Paibian Stage (Cambrian)" (PDF). Lethaia. 37 (4): 365–379. doi:10.1080/00241160410002081. Retrieved 14 September 2012.
  3. ^ "GSSP for the Paibian". Retrieved 12 November 2012.
  4. ^ "GSSP for the Cambrian - Ordovician Boundary". Retrieved 17 November 2012.
  5. ^ "GSSP for Jiangshanian". Retrieved 12 November 2012.
  6. ^ a b c Landing, E.; Westrop, S.R.; Adrain, J.M. (19 September 2011). "The Lawsonian Stage - the Eoconodontus notchpeakensis FAD and HERB carbon isotope excursion define a globally correlatable terminal Cambrian stage". Bulletin of Geosciences: 621–640. doi:10.3140/bull.geosci.1251.
Acanthodus

Acanthodus is an extinct genus of conodonts.

Acanthodus humachensis and A. raqueli are from then Late Cambrian (late Furongian) or early Ordovician (Tremadocian) of the Santa Rosita Formation in Argentina.

Cambrian Stage 10

Stage 10 of the Cambrian is the still unnamed third and final stage of the Furongian series. It follows the Jiangshanian and precedes the Ordovician Tremadocian stage. The proposed lower boundary is the first appearance of the trilobite Lotagnostus americanus around 489.5 million years ago, but other fossils are also being discussed (see below). The upper boundary is defined as the appearance of the conodont Iapetognathus fluctivagus which marks the beginning of the Tremadocian and is radiometrically dated as 485.4 million years ago.

Cambrian–Ordovician extinction event

The Cambrian–Ordovician extinction event occurred approximately 488 million years ago (m.y.a.). This early Phanerozoic Eon extinction event eliminated many brachiopods and conodonts, and severely reduced the number of trilobite species.

It was preceded by the less-documented (but probably more extensive) End-Botomian extinction event around 517 million years ago and the Dresbachian extinction event about 502 million years ago.

The Cambrian–Ordovician event ended the Cambrian Period, and led into the Ordovician Period in the Paleozoic Era.

Cheiruridae

Cheiruridae is a family of phacopid trilobites of the suborder Cheirurina. Its members, as with other members of the suborder, had distinctive pygidia modified into finger-like spines. They first appeared in the uppermost Cambrian (upper Furongian), and persisted until the end of the Middle Devonian (Givetian). Currently about 657 species assigned to 99 genera are included.

Cheirurina

Cheirurina is a suborder of the trilobite order Phacopida. Known representatives range from the uppermost Cambrian (upper Furongian) to the end of the Middle Devonian (Givetian). Cheirurina is made up of a morphologically diverse group of related families.

Conodont

Conodonts (Greek kōnos, "cone", + odont, "tooth") are extinct agnathan chordates resembling eels, classified in the class Conodonta. For many years, they were known only from tooth-like microfossils found in isolation and now called conodont elements. Knowledge about soft tissues remains limited. The animals are also called Conodontophora (conodont bearers) to avoid ambiguity.

Conodonts are considered index fossils, fossils used to define and identify geological periods.

Damesellidae

Damesellidae is a family of odontopleurid trilobites found in late Middle to Late Cambrian marine strata, primarily of China. Damesellids are closely related to the odontopleurids of Odontopleuridae, but are not nearly as spinose, nor possess spines as exaggerated as Odontopleuridae. Like Odontopleuridae odontopleurids, damesellids have broad, bar-shaped cranidia with ledge-like borders. Damesellidae may represent transitional forms between more primitive, possibly ancestral ptychopariids and more advanced odontopleurids.

Guzhangian

The Guzhangian is an uppermost stage of the Miaolingian Series of the Cambrian. It follows the Drumian Stage and precedes the Paibian Stage of the Furongian Series. The base is defined as the first appearance of the trilobite Lejopyge laevigata around 500.5 million years ago. The Guzhangian-Paibian boundary is marked by the first appearance of the trilobite Glyptagnostus reticulatus around 497 million years ago.The name Guzhangian is derived from Guzhang County in Hunan Province of China.

The GSSP is defined in the Huaqiao Formation in Hunan, China. The precise base of the Guzhangian is a limestone layer 121.3 m above the base Huaqiao Formation at the Louyixi section (28.7200°N 109.9647°E / 28.7200; 109.9647), where Lejopyge laevigata has its first appearance.

Jiangshanian

The Jiangshanian is the middle stage of the Furongian series. It follows the Paibian stage and is succeeded by the still unnamed Stage 10 of the Cambrian. The base is defined as the first appearance of the trilobite Agnostotes orientalis which is estimated to be 494 million years ago. The Jiangshanian lasted until approximately 489.5 million years ago.The Cambrian stage was named after Jiangshan, a city in China's Zhejiang province.The GSSP of the Jiangshanian is the "Duibian B Section" (28.815967°N 118.614933°E / 28.815967; 118.614933), west of the village of Duibian, and 10 km north of Jiangshan. The outcrop belongs to the Huayansi Formation.

Lejopyge laevigata

Lejopyge laevigata is a species of agnostid trilobite belonging to the genus Lejopyge. It existed during the Guzhangian to the Paibian Age (around 500.5 to 497 million years ago) of the Cambrian. It has a cosmopolitan distribution and is an important index fossil in biostratigraphy.

Lichida

Lichida is an order of typically spiny trilobite that lived from the Furongian to the Devonian period. These trilobites usually have 8–13 thoracic segments. Their exoskeletons often have a grainy texture or have wart or spine-like tubercles. Some species are extraordinarily spiny, having spiny thoracic segments that are as long or longer than the entire body, from cephalon (head) to pygidium (tail). The sections of the pygidia are leaf-like in shape and also typically end in spines.

The order is divided into two families, Lichidae, and Lichakephalidae. Some experts group the families of the closely related order Odontopleurida within Lichida, too, whereupon the family is then divided into three superfamilies, Dameselloidea, containing the family Damesellidae, Lichoidea, containing the families Lichidae and Lichakephalidae, and Odontopleuroidea, containing the family Odontopleuridae.

Miaolingian

The Miaolingian is the third Series of the Cambrian period, and was formally named in 2018. It lasted from about 509 to 497 million years ago and is divided into 3 stages: the Wuliuan, the Drumian, and the Guzhangian. The Miaolingian is preceded by the unnamed Cambrian Series 2 and succeeded by the Furongian series.

Nautiloid

Nautiloids are a large and diverse group of marine cephalopods (Mollusca) belonging to the subclass Nautiloidea that began in the Late Cambrian and are represented today by the living Nautilus and Allonautilus. Nautiloids flourished during the early Paleozoic era, where they constituted the main predatory animals, and developed an extraordinary diversity of shell shapes and forms. Some 2,500 species of fossil nautiloids are known, but only a handful of species survive to the present day.

Odontopleuridae

Odontopleuridae is a family of odontopleurid trilobites found in marine strata throughout the world. Odontopleurids of Odontopleuridae first appear in Late Cambrian-aged marine strata, and the last genera perish by the end of the Frasnian stage during the Late Devonian. The members of Odontopleuridae are famous for their spinose appearance, having long, often numerous spines along the edges of their exoskeletons, and derived from ends of segments or tubercle ornaments.

Orsten

The Orsten fauna is fossilized organisms preserved in the Orsten lagerstätten of Late Series 3, Stage 4 to Furongian (Upper Cambrian) rocks, notably at Kinnekulle and on the island of Öland, all in Sweden.

The initial site, discovered in 1975 by Klaus Müller and his assistants, exceptionally preserves soft-bodied organisms, and their larvae, who are preserved uncompacted in three dimensions. The fossils are phosphatized and silicified, thus the delicate chitinous cuticle and soft parts are not affected by acids, which act upon the limestone nodules within which the fossils have survived. Acids dissolve the limestone, revealing the microfossils in a recovery process called "acid etching". To recover the fossils, more than one and a half tons of Orsten limestone have been dissolved in acid, originally in a specifically designed laboratory in Bonn, more recently moved to Ulm. The insoluble residue is scanned by electron microscope.The Orsten fauna has improved our understanding of metazoan phylogeny and evolution, particularly among the arthropods, thanks in part to unique preservation of larval stages. The Orsten sites reveals the oldest well-documented benthic meiofauna in the fossil record. For the first time, fossils have been found of tardigrades ("water bears") and apparently free-living pentastomids.The Cambrian strata consist of alum shales with limestone nodules (the Alum Shale Formation), which are interpreted as the products of an oxygen-depleted ("dysoxic") marine bottom water habitat of a possibly offshore seashelf at depths of perhaps 50–100 m. The bottom was rich in organic detritus, forming a soft muddy zone with floc in its surface layer.

Other Orsten fauna have been found in Nevada, eastern Canada, England, Poland, Siberia, China and the Northern Territory of Australia.

Ottoia

Ottoia is a stem-group archaeopriapulid worm known from Cambrian fossils. Although priapulid-like worms from various Cambrian deposits are often referred to Ottoia on spurious grounds, the only clear Ottoia macrofossils come from the Burgess Shale of British Columbia, which was deposited 508 million years ago. Microfossils extend the record of Ottoia throughout the Western Canada Sedimentary Basin, from the mid- to late- Cambrian.

Paibian

The Paibian is the lowest stage of Furongian series of the Cambrian. It follows the Guzhangian (3rd series of the Cambrian) and is succeeded by the Jiangshanian stage. The base is defined as the first appearance of the trilobite Glyptagnostus reticulatus around 497 million years ago. The top, or the base of the Jiangshanian is defined as the first appearance of the trilobite Agnostotes orientalis around 494 million years ago.

The name is derived from Paibi, a village in Hunan, China. The GSSP is defined in the "Paibi section" (Wuling Mountains, Huayuan County), an outcrop of the Huaqiao Formation. The base is the first occurrence of Glyptagnostus reticulatus which is 396 m above the base of the Huaqiao Formation at the type locality (28.3895°N 109.5257°E / 28.3895; 109.5257).

Plectronocerida

Plectronocerida is a primitive order from which subsequent cephalopod orders are ultimately derived.

Pteraspidomorphi

Pteraspidomorphi is an extinct class of early jawless fish. They have long been regarded as closely related or even ancestral to jawed vertebrates, but the few characteristics they share with the latter are now considered as primitive for all vertebrates.

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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