Tannudiscus

Tannudiscus; Temporal range: Toyonian PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Trilobita
Order:	Agnostida
Suborder:	Eodiscina
Superfamily:	Eodiscoidea
Family:	Weymouthiidae
Genus:	Tannudiscus; Pokrovskaya, 1959
species
	T. tannulaicusPokrovskaya, 1959 (type) ; T. altusRepina, 1964 ; T. balanusRushton, 1966 ; T. bullaGabova, 2004 ; T. conicusZhou, 1982 ; T. dingusZhuravleva, Zadorozhnaya, Osadchaya, Pokrovskaya, Rodionova & Fonin, 1967 ; T. extensusZhuravleva, Zadorozhnaya, Osadchaya, Pokrovskaya, Rodionova & Fonin, 1967 ;

Last updated June 07, 2023

Tannudiscus Pokrovskaya (1959) ^[1] is a genus of Eodiscinid trilobites belonging to the family Weymouthiidae Kobayashi T. (1943),^[2] Order Agnostida (Salter 1864).^[3] It lived during the late Lower Cambrian, with remains found in Canada (Newfoundland), China (Gansu), The United Kingdom (England), and the Russian Federation (Tuva, Gorno-Altayskaya).^[4]

Taxonomy

The Weymouthiid family shows a trend of shortening the occipital ring. In Chelediscus and Tannudiscus the occipital ring is entirely obliterated as in the Agnostina suborder. Tannudiscus has some other characters it shares with the Agnostina, such as a glabella consisting of two lobes and the occipital ring divided into basal glabellar lobes. Both the glabella and pygidial axis are isolated from the border furrow, and the latter is undivided. It is therefore considered likely that the Agnostina descended directly from a species assignable to Tannudiscus. The earliest known Agnostina is Archaeagnostus (Peronopsidae).^[4] According to Cotton and Fortey (2005) Tannudiscus is polyphyletic.^[5]

Description

Tannudiscus lacks eyes and has a thorax of three segments. The glabella almost touches the anterior border and consists of two inflated lobes, the frontal one slightly wider than the posterior lobe—a characteristic that is further developed in the Condylopygidae. Posterior glabellar lobe lacks a spine. The occipital ring is formed into two basal lateral lobes. The border is convex, moderately wide, more so in front of the glabella and extends to rear of the glabella in some species. Pygidial axis is conical, with seven or eight rings, and may or may not reach posterior border furrow. The furrows defining the axial rings are indistinct or obsolete. Pygidial border is almost flat, but similar in width to the cephalic border.

Distribution

T. tannulaicus is known from the Lower Cambrian of the Russian Federation (Toyonian (= Stage 4, upper of two stages subdividing the un-named Cambrian Series 2), Shivelikskaya Suite, Tuva, Shivelik-Khem River, eastern Tannu-Ola Mountains).^[4]
T. balanus was originally described in the Lower Cambrian of England.^[6]Holotype is A 57119, held at the Sedgwick Museum of Earth Sciences, University of Cambridge; collected by Rushton from about 450m above base of the Purley Shale Formation, Camp Hill, St. Paul's Church, Stockingford, Nuneaton, Warwickshire, England [Closest ICS interval: Cambrian Series 3 – Terreneuvian Epoch].^[4] The species also occurs in the Toyonian, upper Redland Cove member, Brigus Formation of southeastern Newfoundland ^[7] and also has been found in the Lower Cambrian of the Russian Federation (Russian-Kazakhian Botomian Stage, Sanashtykgolskogo horizon, Shashkunarskaya suite).
T. conicus has been recovered from the late Lower Cambrian of China (Huocheng Formation, Borohoro district).^[8]
T. extensus is present in the Middle Cambrian of Russian Federation (Amgaian, Berikul Formation, Kiya River section, Kuznetsk Alatau).^[4]

Related Research Articles

Agnostus is a genus of agnostid trilobites, belonging to the family Agnostidae, that lived during the late Middle Cambrian – early Upper Cambrian. It is the type genus of the family Agnostidae and is subdivided into two subgenera, Agnostus and Homagnostus.

Acidiscus Rasetti, 1966, is a genus of Eodiscinid trilobite belonging to the family Weymouthiidae Kobayashi T. (1943), Order Agnostida Salter (1864). It lived during the Botomian stage = late Lower Cambrian Stage 4 ; the upper Botomian boundary corresponds to base of the Middle Cambrian, Miaolingian Series and Wuliuan stage.

Analox Rasetti, 1966 is a genus of Eodiscinid trilobites belonging to the family Weymouthiidae Kobayashi T. (1943), Order Agnostida It lived during the Botomian stage. It can easily be distinguished from other trilobites by the two furrows that extend forwards and sidewards from the front of the glabella.

Ninadiscus Korobov, 1980, is a genus of Eodiscinid trilobite belonging to the family Weymouthiidae Kobayashi (1943), Order Agnostida Salter (1864). It lived during the Botomian Stage = late Lower Cambrian Stage 4 ; the upper Botomian boundary corresponds to the base of the Middle Cambrian, the Miaolingian Series and Wuliuan Stage.

Chelediscus Rushton, 1966, is a genus of Eodiscinid trilobite belonging to the family Weymouthiidae Kobayashi T. (1943), Order Agnostida Salter (1864). The Treatise assigns this genus to the Calodiscidae; Cotton and Fortey (2005) however move it to the Weymouthiidae. Chelediscus lived during the later part of the Botomian stage.

Tsunyidiscus is a trilobite belonging to the Suborder Eodiscina. Tsunyidiscus appeared near the end of the Lower Cambrian, during the late Atdabanian stage of geologic time and some collections suggest it may have survived into the Botomian. The genus is very small, oculate and isopypous with a narrow dome-shaped glabella and a narrow bullet-shaped pygidial axis. Thorax consists of three segments. Tsunyidiscus is the only genus currently attributed to the family Tsunyidiscidae.

Pagetia Walcott, 1916. is a small genus of trilobite, assigned to the Eodiscinid family Pagetiidae and which had global distribution during the Middle Cambrian. The genus contains 55 currently recognized species, each with limited spatial and temporal ranges.

Acmarhachis is a genus of trilobite in the order Agnostida, which lived in what are now Australia, Canada, China (Anhui), Kazakhstan, Russia (Kharaulakh), and the US. It was described by Resser in 1938, and the type species is Acmarhachis typicalis.

Lotagnostus is a genus of very small trilobites in the order Agnostida, which lived on the outer continental shelves worldwide, during the late Upper Cambrian. It was described by Whitehouse in 1936, and the type species is Lotagnostus trisectus, which was originally described as a species of Agnostus by Salter in 1864.

Mallagnostus Howell, 1935, is a trilobite genus belonging to the family Weymouthiidae Kobayashi T. (1943), Order Agnostida Salter (1864) according to Whittington et al. 1997. It lived during the late Lower Cambrian, with remains found in USA, Canada (Newfoundland), Spain, England, Russia, Mongolia, and the early Middle Cambrian as reported from China and Russia (Yakutia).

Galbagnostus is an extinct genus of agnostid trilobite. It lived during the Lower and Middle Ordovician.

The Weymouthiidae Kobayashi 1943 are an extinct family of eodiscinid agnostid trilobites. They lived during the late Lower Cambrian and earliest Middle Cambrian in the so-called Olenellus- and Eokochaspis-zones in the former paleocontinents of Laurentia, Avalonia, Gondwana. The Weymouthiidae are all blind and lack free cheeks.

<span class="mw-page-title-main">Condylopygidae</span>

The Condylopygidae Raymond (2013) are a family of small trilobites that lived during the Middle Cambrian, and found in Canada, the Czech Republic, Germany, France, Spain, England, Wales, Sweden, and the Russian Federation (Siberia). They uniquely differ from all other Agnostina in having the frontal glabellar lobe wider than the rear lobe. The Condylopygidae are the only family assigned to the Condylopygoidea superfamily.

Condylopyge Hawle and Corda (1847) is a genus of agnostid trilobite that lived during the late Lower and early Middle Cambrian, in what are today Canada, the Czech Republic, England and Wales, France, Germany, Italy, Morocco, the Russian Federation, Spain, Turkey and Sweden. It can easily be distinguished from all other Agnostida because the frontal glabellar lobe is notably wider than the rear lobe. It belongs to the same family as Pleuroctenium but the frontal glabellar lobe does not fold around the rear lobe, as it does in that genus. Condylopyge is long ranging, possibly spanning the early Cambrian Terreneuvian Series in Nuneaton, central England into at least Drumian strata at various locations elsewhere.

Geragnostus is a genus of very small agnostid trilobites whose fossils are found Ordovician-aged marine strata from Eurasia, North America and Argentina.

The Calodiscidae Kobayashi, 1943 [nom. transl. Öpik, 1975 ex Calodiscinae Kobayashi, 1943] are a family of trilobites belonging to the order Agnostida that lived during the Lower Cambrian. They are small or very small, and have a thorax of two or three segments. The Calodiscidae includes five genera.

Jinghediscus Xiang & Zhang, 1985 is a genus of Eodiscinid trilobite belonging to the family Weymouthiidae Kobayashi T. (1943), Order Agnostida It lived during the lower Middle Cambrian, with remains found in China (Xinjiang) and Australia (Queensland).

Cedaria is a small, rather flat trilobite with an oval outline, a headshield and tailshield of approximately the same size, 7 articulating segments in the middle part of the body and spines at the back edges of the headshield that reach half the length of the body. Cedaria lived during the early part of the Upper Cambrian (Dresbachian), and is especially abundant in the Weeks Formation.

Anabaraspis is a genus of redlichiid trilobite. A. splendens occurs in the uppermost Lower Cambrian and lowest Middle Cambrian of Russia. In Anabaraspis there is a long area in front of the glabella which is not differentiated in a border and a preglabellar field. This is a unique character in the family Paradoxididae. The frontal lobe of the central raised area of the headshield is slightly pointed, rather than rounded or truncate, a character shared with Plutonides, though, in Plutonides it hangs over the short anterior border.

Serrodiscus Richter and Richter 1941. is a genus of Eodiscinid trilobite belonging to the family Weymouthiidae Kobayashi T. (1943), Order Agnostida. It lived during the late Lower Cambrian, with remains found in Canada, China (Gansu), The United Kingdom (England), Germany (Silesia), Poland, the Russian Federation, and the United States. It is named for the spines on the ventral side of the pygidium, which give it a serrated impression.

References

↑ POKROVSKAYA N. V. 1959. The trilobite fauna and stratigraphy of the Cambrian deposits of Tuva. Akademiy Nauk, SSSR, Trudy, Geologisicheskogo, Instituta, Number 27, pp. 1-199, pls. 1-11. [In Russian].
↑ KOBAYASHI T. 1943. Brief notes on the Eodiscids 1, their classification with a description of a new species and a new variety, Proceedings of the Imperial Academy, Tokyo, Volume 19, pp. 37-42.
↑ SALTER, J. W. 1864: On some new fossils from the Lingula-flags of Wales. Quarterly Journal of the Geological Society of London, 20, 233 – 241.
1 2 3 4 5 WHITTINGTON H. B.; et al., eds. (1993). Treatise on Invertebrate Paleontology, Part O., Revised.
↑ COTTON, T. J.; FORTEY, R. A. (2005). "Comparative morphology and relationships of the Agnostida". In Koenemann, S.; Jenner, R. (eds.). Crustacea and Arthropod Relationships. Crustacean Issues. Vol. 16.
↑ RUSHTON, A. W. A. 1966. The Cambrian Trilobites from the Purley Shales of Warwickshire. Palaeontographical Society Monographs (1): p. 22 pl. 3 figs. 9 a-c.
↑ RUSHTON, A. W. A. (2011). "8> Midland microcraton". A Revised Correlation of the Cambrian Rocks in the British Isles. Bath: the geological Society Publishing house. ISBN 9781862393325 . Retrieved 27 November 2013.
↑ HUANLING, L.; ZHIYI, Z.; YUNAN, N.; ZHIQIANG, Z. (December 1996). "III. Stratigraphic framework - 11. Cambrian". Phanerozoic Geology of Northwest China. Beijing. p. 135. ISBN 9067642282 . Retrieved 27 November 2013.

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[1] POKROVSKAYA N. V. 1959. The trilobite fauna and stratigraphy of the Cambrian deposits of Tuva. Akademiy Nauk, SSSR, Trudy, Geologisicheskogo, Instituta, Number 27, pp. 1-199, pls. 1-11. [In Russian].

[2] KOBAYASHI T. 1943. Brief notes on the Eodiscids 1, their classification with a description of a new species and a new variety, Proceedings of the Imperial Academy, Tokyo, Volume 19, pp. 37-42.

[3] SALTER, J. W. 1864: On some new fossils from the Lingula-flags of Wales. Quarterly Journal of the Geological Society of London, 20, 233 – 241.

[Treatise-4] 1 2 3 4 5 WHITTINGTON H. B.; et al., eds. (1993). Treatise on Invertebrate Paleontology, Part O., Revised.

[5] COTTON, T. J.; FORTEY, R. A. (2005). "Comparative morphology and relationships of the Agnostida". In Koenemann, S.; Jenner, R. (eds.). Crustacea and Arthropod Relationships. Crustacean Issues. Vol. 16.

[6] RUSHTON, A. W. A. 1966. The Cambrian Trilobites from the Purley Shales of Warwickshire. Palaeontographical Society Monographs (1): p. 22 pl. 3 figs. 9 a-c.

[7] RUSHTON, A. W. A. (2011). "8> Midland microcraton". A Revised Correlation of the Cambrian Rocks in the British Isles. Bath: the geological Society Publishing house. ISBN 9781862393325 . Retrieved 27 November 2013.

[8] HUANLING, L.; ZHIYI, Z.; YUNAN, N.; ZHIQIANG, Z. (December 1996). "III. Stratigraphic framework - 11. Cambrian". Phanerozoic Geology of Northwest China. Beijing. p. 135. ISBN 9067642282 . Retrieved 27 November 2013.

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