Tsunyidiscus

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Tsunyidiscus
Temporal range: Late Atdabanian
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Tsunyidiscus niutitangensis linedrawing.jpg
linedrawing of Tsunyidiscus niutitangensis
Scientific classification
Kingdom:
Animalia
Phylum:
Arthropoda
Class:
Trilobita
Order:
Agnostida
Suborder:
Eodiscina
Family:
Tsunyidiscidae

Zhang, 1980
Genus:
Tsunyidiscus

W. Chang, 1966
Species
  • T. niutitangensis(Chang ,1964) (Type)
  • T. aclis(Zhou, 1975)
  • T. acutus(Sun, 1983)
  • T. armatus(Zhang & Zhu, 1980)
  • T. chintingshanensis(Lu, 1942)
  • T. limbanodusQian in Zhang et al., 1980
  • T. longquanensis(Zhang and Zhu in Zhang et al., 1980)
  • T. pengshuiensisZhang & Clarkson, 2012
  • T. pertenusLin et al., 2004
  • T. yanjiazhiensisS. Zang et al. in Yin and Li, 1978

And see text

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 (up to 7mm), 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. [1]

Contents

Description

Like other Agnostida the exoskeleton of Tsunyidiscus is diminutive and isopygous with 3 fulcrate thoracic segments. The cephalon has a strongly parabolic outline and maximum width (tr.) usually anterior the to genal angles. Glabella extremely narrow, lateral glabellar furrows usually obscure, with a rounded and expanded frontal glabellar lobe. The occipital ring (LO) is at least as long as L1, usually expanded laterally, and may bear a sharp posteriorly directed spine. Long, curved posterior fixigenal spines may be present. The occipital furrow is transverse and uninterrupted. Facial sutures proparian. Librigenae are 0.5% as long as the cephalon. The pygidium has a narrow multi=segmented axis (with five, six or more segments). The thoracic and pygidial axial segments may carry nodes. [1] [2]

Species and distribution

= Emeidiscus planilimbatus, Mianxiandiscus badaowanensis, M. emeiensis, M. gaoqiaoensis, M. jinningensis, M. sichuanensis
Collected in the Lower Cambrian of China (Atdabanian: Jinning, 24.7° N, 102.7° E [3] and Maotianshan 24.0°N, 102.0°E, [4] Yuanshan Formation, Yunnan).
Present in the Lower Cambrian of China (Atdabanian, Shuijingtuo Formation, Yichang and Zgui, Yangtze Gorge Area, Hubei, 111°E, 30.5°N) [2]
Occurs in the Lower Cambrian of China (Atdabanian: Weng'an, Longshancun Section, Niutitang Formation, Guizhou, 27.1°N, 107.5°E) [3]
= T. kaiyangensis, Eodiscus chintingshanensis, Guizhoudiscus chintingshanensis, G. kaiyangensis, H. chintingshanensis
Occurs in the Lower Cambrian of China (Zhongxin). [5]
= Shizhudiscus longquanensis
= Hebediscus niutitangensis
Known from the Lower Cambrian of China (Atdabanian: Jinning, 24.7° N, 102.7° E [3] and Malong, 25.4° N, 103.4° E, [6] Yuanshan Formation, Yunnan; Zhijin, Gezhongwu Section, [3] and Weng'an, Longshancun Section, Niutitang Formation, GuiZhou, 26.7°N, 105.8°E.
= T. orientalis, Hebediscus orientalis, Hupeidiscus orientalis
Found in the Lower Cambrian of China (Atdabanian: Huanglian Member, Jiumenchong Formation, 28.2°N, 109.2°E, Taijiang, Wuhe Member, Jiumenchong and Bianmachong Formations, 26.7° N, 108.3° E); [3] Botomian: Weng'an, Longshancun Section, Mingxinsi Formation, Guizhou, 27.1°N, 107.5°E; [3] Atdabanian: Pangwangcun Member, Huangboling Formation, Anhui, 30.1°N, 117.0°E [3]
Present in the Lower Cambrian of China (Atdabanian: Shuijingtuo Formation, Yangtze Gorge, Hubei, 30.8° N, 111.3° E). [8]

Taxonomy

Cladogram of the relations within the monotypical family Tsunyidiscidae, with other Eodiscina and with the ancestral genus Bulaiaspis (Redlichiina, Chengkouaspidae) Tsunyidiscus cladogram.png
Cladogram of the relations within the monotypical family Tsunyidiscidae, with other Eodiscina and with the ancestral genus Bulaiaspis (Redlichiina, Chengkouaspidae)

Ancestors

Tsunyidiscus is the oldest known eodiscoid. The glabella of Tsunyidiscus is extremely similar to that of Dipharus clarki, and distinct from all other eodiscoids. D. clarki is thought to represent an immature stage of the redlichioid Bulaiaspis rather than an eodiscoid. This is because of the dominant palpebroocular ridges, extremely long librigenae, and free pleural tips on the pygidium of variable numbers of segments. In short: Tsunyidiscus is thought to have developed through paedomorphosis from Bulaiaspis. [1]

Descendants

Three lineages are thought to have evolved from Tsunyidiscus. First the Hebediscidae, that themselves gave rise to the Weymouthiidae, which contain Tannudiscus, the probable ancestor of the Agnostina. Second the Yukoniidae, who sprouted the Eodiscidae. And finally the Calodiscidae. [1]

Related Research Articles

<i>Agnostus</i> Extinct genus of trilobites

Agnostus, is a genus of agnostid trilobite 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.

<i>Acimetopus</i>

Acimetopus Rasetti, 1966, 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 base of the Middle Cambrian, Miaolingian Series and Wuliuan stage.

<i>Analox</i>

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.

Meniscuchus is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the Botomian stage, which lasted from approximately 522 to 516 million years ago. This faunal stage was part of the Cambrian Period. Meniscuchus has been found in the USA, Canada, Russia and Australia.

<i>Dicerodiscus</i>

Dicerodiscus is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the early part of the Botomian stage, in China. Four species have been assigned to it. Dicerodiscus is unique for an eodiscoid in having conspicuous and curved spines that are attached anteriorly, and at their base are directed outward perpendicular to the midline, before gradually bending further backwards.

Resserops is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the middle of the Atdabanian or the early part of the Botomian stage, which lasted from approximately 524 to 518.5 million years ago. This faunal stage was part of the Cambrian Period. It has been found in Spain and southern Morocco. It can be recognised by the sabre-like spines of the headshield that are a smooth continuation of the frontal edge, and the enlarged spines on the 9th segment of the thorax.

Egyngolia is a genus of very small sized Trilobites, that lived during the Lower Cambrian in what are today the Russia Federation, Mongolia, and South Australia.

<i>Sinodiscus</i> Extinct genus of trilobites

Sinodiscus is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the late Atdabanian stage, which lasted from 530 to 524 million years ago during the early part of the Cambrian Period.

Lemdadella is an extinct genus of redlichiid trilobites that lived during the late Atdabanian stage, which lasted from 530 to 524 million years ago during the early part of the Cambrian Period.

<i>Pagetia</i> Genus of trilobites

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.

<i>Eoredlichia</i> Extinct genus of trilobites

Eoredlichia is an extinct genus of trilobite of average to large size. It lived during the early Cambrian in the Chengjiang fauna of Yunnan, China, and in Australia and Thailand. Eoredlichia is compounded of the Greek ἠώς and Redlichia, a later but related genus, so it means "early Redlichia". The species epithet intermedia means intermediate, indicating it is morphologically intermediate between other species. Eofallotaspis gives rise to Lemdadella, and thence to Eoredlichia and the other Redlichiidae.

Eodiscina

Eodiscina is trilobite suborder. The Eodiscina first developed near the end of the Lower Cambrian period and became extinct at the end of the Middle Cambrian. Species are tiny to small, and have a thorax of two or three segments. Eodiscina includes six families classified under one superfamily, Eodiscoidea.

Agnostotes orientalis is a species of agnostid trilobite belonging to the genus Agnostotes. It existed during the Jiangshanian Age of the Cambrian. It is an important index fossil in biostratigraphy.

<i>Litometopus</i> Extinct genus of trilobites

Litometopus is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the Botomian stage.

<i>Thoracocare</i>

Thoracocare is a minute to very small trilobite, that lived during part of the Middle Cambrian in what are today the states of Idaho, Nevada and Utah. It is the only trilobite known with just two thorax segments outside most members of the Agnostida order. It can be distinguished from Agnostida by the very wide subquadrate glabella, parallel-side or widening forward in the largest specimen, with the full front side touching the border. Two species are known, one, T. idahoensis, only from pygidia.

<i>Delgadella</i>

Delgadella is a diminutive trilobite that lived during the late Lower Cambrian and has been found in Russia, Mongolia, Spain, Italy (Sardinia), Portugal, Morocco and Canada (Newfoundland). It can be recognized by its strongly effaced headshield and tailshield, with narrow but distinct furrows and borders along its margins, and three thorax segments.

Tannudiscus Pokrovskaya (1959) is a genus of Eodiscinid trilobites belonging to the family Weymouthiidae Kobayashi T. (1943), Order Agnostida. It lived during the late Lower Cambrian, with remains found in Canada (Newfoundland), China (Gansu), The United Kingdom (England), and the Russian Federation.

The Hebediscidae Kobayashi, 1944, 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 Hebediscidae include five genera.

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.

<i>Cedaria</i>

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 halflength of the body. Cedaria lived during the early part of the Upper Cambrian (Dresbachian), and is especially abundant in the Weeks Formation.

References

  1. 1 2 3 4 Whittington, H. B. et al. Part O, Treatise on Invertebrate Paleontology. Revised, Volume 1 – Trilobita – Introduction, Order Agnostida, Order Redlichiida. 1997
  2. 1 2 Dai, T.; Zhan, X. (2011). "Ontogeny of the eodiscoid trilobite Tsunydiscus acutus from the Lower Cambrian of South China". Palaeontology. 54 (6): 1279–1288. doi: 10.1111/j.1475-4983.2011.01102.x . ISSN   0031-0239.
  3. 1 2 3 4 5 6 7 A. Yang, M. Zhu, J. Zhang and G. Li. 2003. Early Cambrian eodiscoid trilobites of the Yangtze Platform and their stratigraphic implications. Progress in Natural Science 13(11):861-866 |cited in=PBDB
  4. ↑ J. Yugan, H. Xianguang, and W. Huayu. 1993. Lower Cambrian pediculate lingulids from Yunnan, China. Journal of Paleontology 67(5):788-798|cited in=PBDB
  5. ↑ Paleobiology Database. "†Tsunyidiscus chintingshanensis Lu 1942 (trilobite)" . Retrieved 25 November 2012.
  6. ↑ M. Steiner, M. Zhu, Y. Zhao and B.-D. Erdtmann. 2005. Lower Cambrian Burgess Shale-type fossil associations of South China. Palaeogeography, Palaeoclimatology, Palaeoecology 220:129-152|cited in=PBDB
  7. ↑ Zhang, X.-G.; Clarkson, E.N.K. (2012). "Phosphatized eodiscoid trilobites from the Cambrian of China". Palaeontographica Abteilung A. 297 (1–4): 1–121. doi:10.1127/pala/297/2012/1. Archived from the original on 2013-02-11.
  8. ↑ S. Weiguo. 1986. Late Precambrian Pennatulids (sea pens) from the Eastern Yangtze Gorge, China: Paracharnia gen. nov Precambrian Research 31:361-375|cited in=PBDB
  9. ↑ Cotton, T.J.; Fortey, R.A. (2005). "5. Comparative morphology and relationships of the Agnostida". In Koenemann, S.; Jenner, R. (eds.). Crustacean Issues 16, Crustacea and Arthropod Relationships. Boca Raton: CRC Press.
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