Mallagnostus

Mallagnostus; Temporal range: Toyonian to early Middle Cambrian PreꞒ Ꞓ O S D C P T J K Pg N
	Mallagnostus desideratus, cephalon
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	† Trilobita (?)
Order:	† Agnostida
Family:	† Weymouthiidae
Genus:	† Mallagnostus ; Howell, 1935
Species
	M. desideratus(Walcott, 1890b) synonym Agnostus desideratus; M. limbatus(Pokrovskaya, 1959) synonym Ladadiscus limbatus; M. llarenai (Richter & Richter, 1941) ;
Synonyms
	LadadiscusPokrovskaya, 1959

Last updated January 03, 2025

Mallagnostus Howell, 1935,^[1] is a trilobite genus belonging to the family Weymouthiidae Kobayashi T. (1943), ^[2] Order Agnostida Salter (1864) ^[3] according to Whittington et al. 1997. ^[4] It lived during the late Lower Cambrian, with remains found in USA (New York), Canada (Newfoundland), Spain, England, Russia (Tuva, Gorno-Altayskaya), Mongolia, and the early Middle Cambrian as reported from China (Tian Shan) and Russia (Yakutia).

Taxonomy

Mallagnostus was originally described as belonging to the Agnostina, but it is more appropriately placed in the Eodiscina. Within the Weymouthiidae, Mallagnostus belongs to a clade that further includes Tannudiscus , Jinghediscus and the Agnostina.^[5]

Distribution

M. desideratus Walcott, 1890, ^[6] is from the Lower Cambrian Olenellus Zone of North America.
M. limbatus Pokrovskaya, 1959, ^[7] has been collected from the upper Lower Cambrian of New York, ^[5] and the Toyonian of the Russian Federation (Obruchev stage, Shivelig Formation, Shivelig-Khem River, Tuva, Altay-Sayan, Siberia, 51.4° N, 94.2° E) ^[8]
M. llarenai Richter and Richter, 1941, ^[9] is found in the late Lower Cambrian of Spain (serratus Band, Herrerias-Mergel Formation, Cala). ^[5]

Ecology

Mallagnostus limbatus occurs with Tannudiscus tannuolaicus, Menneraspis striata, Beldirella pulchra and Cheiruroides maslovi.^[8]

Description

Mallagnostus is isopygous and, like all Weymouthiidae, lacks eyes and facial sutures. The cephalon is semi-elliptical with unfurrowed glabella (in one species there are lateral indentations). The glabella does not quite reach the broad border furrow. The occipital ring (L0) is short (sag.), ill-defined, and does not carry a spine. Anterior border of cephalon is long, only gently convex, and becomes shallower further from the axis. The border furrow runs into the margin just in front of the genal angle. Thorax of three segments, as in all other Weymouthiidae where the thorax is known. The pygidial axis is conical with at least eight rings, and does not extend to the posterior border furrow. Pleural fields smooth. ^[5]

Related Research Articles

Acidiscus 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.

Acimetopus 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.

Analox 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.

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

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.

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.

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.

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.

Acmarhachis is a genus of trilobites 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.

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.

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

Morocconus is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It is still debated if it lived at the very end of the Lower Cambrian or at the very beginning of the Middle Cambrian. Morocconus notabilis is the only known species in this genus.

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

The Peronopsidae comprise the earliest family of the Agnostina suborder. Species of this family occurred on all paleocontinents. The earliest representatives of this family first occur just before the start of the Middle Cambrian, and the last disappeared just after the start of the Upper Cambrian.

The Weymouthiidae 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.

Toragnostus is a genus of trilobites restricted to the late Middle Cambrian. Its remains have been found in the United States, Greenland, Denmark, China, Sweden, the Russian Federation, and Kazakhstan. Its headshield and tailshield are almost completely effaced and it has two 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.

Hebediscidae is 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.

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

↑ HOWELL, B. F. 1935. Cambrian and Ordovician trilobites from Herault, southern France. Journal of Paleontology9 (3): 222-238
↑ KOBAYASHI, 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.
↑ WHITTINGTON, H. B. et al. Part O, Treatise on Invertebrate Paleontology. Revised, Volume 1 – Trilobita – Introduction, Order Agnostida, Order Redlichiida. 1997.
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
↑ WALCOTT 1890. Descriptive notes of new genera and species from the Lower Cambrian or Olenellus zone of North America. Proceedings of the United States National Museum, 12: 33 - 46.
↑ 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].
1 2 OSADCHAYA, D.V.; KASHINA, L.N.; ZHURAVLEVA, I.T.; BORODINA, N.P. (1979). "Stratigrafiya i arkheotsiaty nizhnego kembriya Altaye-Sayanskoy skladchatoy oblasti [Lower Cambrian stratigraphy and archaeocyatha of the Altay-Sayan fold belt]". Trudy Instituta Geologii I Geofiziki, Sibirskoye Otdeleniye (380): 1–215.cited inPaleobiological Database. "Mallagnostus".
↑ RICHTER, R., & RICHTER, E., 1941. Die Fauna des Unter-Kambriums von Cala in Andalusien. Abhandlungen der senckenbergischen naturforschenden Gesellschaft, 455: 90 pp., 83 figs., 4 pls., Frankfurt.

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[1] HOWELL, B. F. 1935. Cambrian and Ordovician trilobites from Herault, southern France. Journal of Paleontology9 (3): 222-238

[2] KOBAYASHI, 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.

[4] WHITTINGTON, H. B. et al. Part O, Treatise on Invertebrate Paleontology. Revised, Volume 1 – Trilobita – Introduction, Order Agnostida, Order Redlichiida. 1997.

[Treatise-5] 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

[6] WALCOTT 1890. Descriptive notes of new genera and species from the Lower Cambrian or Olenellus zone of North America. Proceedings of the United States National Museum, 12: 33 - 46.

[7] 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].

[Osadchaya-8] 1 2 OSADCHAYA, D.V.; KASHINA, L.N.; ZHURAVLEVA, I.T.; BORODINA, N.P. (1979). "Stratigrafiya i arkheotsiaty nizhnego kembriya Altaye-Sayanskoy skladchatoy oblasti [Lower Cambrian stratigraphy and archaeocyatha of the Altay-Sayan fold belt]". Trudy Instituta Geologii I Geofiziki, Sibirskoye Otdeleniye (380): 1–215.cited inPaleobiological Database. "Mallagnostus".

[9] RICHTER, R., & RICHTER, E., 1941. Die Fauna des Unter-Kambriums von Cala in Andalusien. Abhandlungen der senckenbergischen naturforschenden Gesellschaft, 455: 90 pp., 83 figs., 4 pls., Frankfurt.

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Mallagnostus Temporal range: Toyonian to early Middle Cambrian PreꞒ Ꞓ O S D C P T J K Pg N

Mallagnostus desideratus, cephalon
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	† Trilobita (?)
Order:	† Agnostida
Family:	† Weymouthiidae
Genus:	† Mallagnostus Howell, 1935
Species
M. desideratus(Walcott, 1890b) synonym Agnostus desideratus M. limbatus(Pokrovskaya, 1959) synonym Ladadiscus limbatus M. llarenai (Richter & Richter, 1941)
Synonyms
LadadiscusPokrovskaya, 1959