Acidiscus

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Acidiscus
Temporal range: Botomian (Olenellus-zone)
Acidiscus linedrawing.jpg
Acidiscus birdi
Scientific classification
Kingdom:
Animalia
Phylum:
Arthropoda
Class:
Trilobita
Order:
Agnostida
Suborder:
Eodiscina
Superfamily:
Eodiscoidea
Family:
Weymouthiidae
Genus:
Acidiscus

Rasetti, 1966
Type species
Acidiscus birdi
species
  • A. birdiRasetti, 1966 [1]
  • A. hexacanthusRasetti, 1966
  • A. theristesRushton, 1966

Acidiscus Rasetti, 1966, [2] is a genus of Eodiscinid trilobite belonging to the family Weymouthiidae Kobayashi T. (1943), [3] Order Agnostida Salter (1864). [4] It lived during the Botomian stage [1] = late Lower Cambrian Stage 4 (upper of two stages subdividing the unnamed Series 2); the upper Botomian boundary corresponds to base of the Middle Cambrian, Miaolingian Series and Wuliuan stage.

Contents

Etymology

Taxonomy

Stigmadiscus cladogram.png

A cladogram showing the relationship between several species of the genera Acidiscus, Bolboparia and Stigmadiscus [6] [7] Acidiscus is most closely related to Bolboparia and slightly more distantly to Stigmadiscus. Synapomorphies for Acidiscus-Bolboparia include anterolateral cephalic spines and a large preoccipital glabellar tubercle or spine. Both of these features have been considered as being diagnostic of Acidiscus (e.g., Rushton, 1966; Rasetti, 1966;) but they are shared with Bolboparia. Synapomorphies of Bolboparia include a sharply tapered and pointed glabella, no occipital spine, tubercles confined to posterior part of the cephalic border, strongly inflated genae, and a sculpture of tightly packed coarse granules. Stigmadiscus is characterised by an inflated posterior part of the glabella, the loss of anterolateral cephalic spines and a preoccipital glabellar node, and in having a very narrow cephalic border.

Among genera currently assigned to Weymouthiidae Kobayashi, 1943 (Jell in Whittington et al. 1997), Rushton (1966, p. 12) noted that, “Acidiscus Rasetti differs from Serrodiscus but slightly”, although several of the characteristics in the former genus that he listed, include the preoccipital glabellar and anterolateral cephalic spines, and the configuration of the lateral glabellar furrows.

Distribution

Ecology

A. birdi occurs in association with other Weymouthiidae ( Acimetopus , Analox , Bathydiscus , Bolboparia , Leptochilodiscus , Serrodiscus ), Calodiscus, several species of Olenellus , and Bonnia (Dorypygidae). [8]

Description

Like all Weymouthiidae, Acidiscus lacks eyes and facial sutures. The cephalic border carries one or two pairs of marginal spines. The glabella does not reach the border furrow and has two short pit-like pairs of lateral furrows. Occipital and genal spines are present. Thorax unknown, but all weymouthiids in which it is known have three segments. The pygidium is much like that in Serrodiscus , with an axis composed of ten rings. Pleural fields unfurrowed. [9]

Related Research Articles

<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.

<i>Bathydiscus</i>

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

<i>Bolboparia</i>

Bolboparia is an extinct genus of eodiscinid agnostid trilobites. It lived during the late Lower Cambrian in what today Canada and the United States.

Leptochilodiscus Rasetti, 1966 [= Kerberodiscus Bassett et al., 1976] is a genus of Lower Cambrian Eodiscinid trilobite belonging to the family Weymouthiidae Kobayashi (1943), Order Agnostida. It lived during the Botomian stage = late Lower Cambrian Stage 4 ; the upper Botomian Stage boundary corresponds to base of both the Middle Cambrian Wuliuan stage and Miaolingian Series.

<i>Ninadiscus</i>

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.

<i>Oodiscus</i>

Oodiscus is an extinct genus of small size trilobite, with three known species. It lived during the Toyonian in what are now Canada and the USA.

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

Parapagetia 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 524 to 518.5 million years ago. This faunal stage was part of the Cambrian Period.

Semadiscus is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It has been collected from the Lower Cambrian of Canada (Newfoundland), Russia, and the United States. Only the headshield is known, and it may well be that it would be better to include it in Serrodiscus.

<i>Chelediscus</i>

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.

<i>Tsunyidiscus</i> Genus of trilobites

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.

<i>Weymouthia</i> (trilobite)

Weymouthia is an extinct genus of eodiscinid agnostid trilobites, which lived at the end of the Lower Cambrian, in what are now the eastern United States, England, Siberia and China.

<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>Mallagnostus</i>

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).

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

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.

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 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>Jinghediscus</i>

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).

<i>Serrodiscus</i>

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

  1. 1 2 SEPKOSKI, J. (2002). "A compendium of fossil marine animal genera (Trilobita entry)". Bulletins of American Paleontology. 364: 560. Archived from the original on 5 September 2006. Retrieved 12 January 2008.
  2. ↑ RASETTI, F., 1966. New Lower Cambrian trilobite faunule from the Taconic sequence of New York. Smithsonian Miscellaneous Collections148, 1-52.
  3. ↑ 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.
  4. ↑ 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.
  5. ↑ RASETTI, F. (1966). "New Lower Cambrian trilobite faunule from the Taconic sequence of New York". Smithsonian Miscellaneous Collections. 148 (9): 1–52.
  6. ↑ WESTROP, S. R.; LANDING, E. (2011). "Lower Cambrian (Branchian) eodiscoid trilobites from the lower Brigus Formation, Avalon Peninsula, Newfoundland, Canada". Memoirs of the Association of Australasian Palaeontologists. 42: 209–262.
  7. ↑ 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.
  8. 1 2 Paleobiology Database. "East Chatham Quad, unnamed fm., NY (Cambrian of the United States) (trilobite)" . Retrieved 19 December 2012.
  9. 1 2 WHITTINGTON, H. B. et al., 1997. Part O, Treatise on Invertebrate Paleontology. Revised, Volume 1 – Trilobita – Introduction, Order Agnostida, Order Redlichiida.
  10. ↑ RUSHTON, A.W.A. 1966. The Cambrian Trilobites from the Purley Shales of Warwickshire. Palaeontographical Society Monographs (1): p. 16, pl. 1, figs. 20 a, b.
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