Ovatoryctocara

Ovatoryctocara; Temporal range: Middle Cambrian (Ovatoryctocara zone) PreЄ Є O S D C P T J K Pg N ↓
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Trilobita
Order:	Corynexochida
Suborder:	Corynexochina
Family:	Oryctocephalidae
Subfamily:	Oryctocarinae [1]
Genus:	Ovatoryctocara; Tchernysheva, 1962
Species
	O. ovata(Tchernysheva, 1960) (Type) synonym Oryctocara ovata; O. angusta(Tchernysheva, 1962) synonym Oryctocara angusta O. angusta ssp. angusta; O. angusta ssp. snegirevae(Suvorova, 1964) synonym Oryctocara snegirevae; ; O. doliiformisKorovnikov & Shavanov, 2008; O. granulata (Tchernysheva, 1962) synonyms O. yaxiensis, Oryctocara granulata;

Last updated April 30, 2019

Ovatoryctocara is a genus of small corynexochid trilobites from the Cambrian, that lived in what now are Siberia, China, Greenland and Canada (Newfoundland). Ovatoryctocara can be recognised by the combination of the following characters: the central raised area of the cephalon (or glabella) is approximately cylindrical and has two rows of four triangular or round pits. The thorax only has 5 or 6 segments. The tailshield (or pygidium) has an axis (or rhachis) of 6 to 12 rings, the pleural furrows are well developed and the border is absent or narrow as a hair.^[2]

A genus is a taxonomic rank used in the biological classification of living and fossil organisms, as well as viruses, in biology. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclature, the genus name forms the first part of the binomial species name for each species within the genus.

Corynexochida is an order of trilobite that lived from the Lower Cambrian to the Late Devonian. Like many of the other trilobite orders, Corynexochida contains many species with widespread characteristics.

Trilobites are a group of extinct marine arachnomorph arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the Atdabanian stage of the Early Cambrian period, and they flourished throughout the lower Paleozoic era before beginning a drawn-out decline to extinction when, during the Devonian, all trilobite orders except the Proetids died out. Trilobites disappeared in the mass extinction at the end of the Permian about 252 million years ago. The trilobites were among the most successful of all early animals, existing in oceans for over 300 million years.

Etymology

The name of the genus is derived from its type Oryctocara ovata. Ovata refers to its oval overall shape, the Ancient Greek ὀρύκτης (oryctos) means "digger", and the Latin cara is a word for "head" or "face".

The Ancient Greek language includes the forms of Greek used in Ancient Greece and the ancient world from around the 9th century BCE to the 6th century CE. It is often roughly divided into the Archaic period, Classical period, and Hellenistic period. It is antedated in the second millennium BCE by Mycenaean Greek and succeeded by medieval Greek.

Latin is a classical language belonging to the Italic branch of the Indo-European languages. The Latin alphabet is derived from the Etruscan and Greek alphabets and ultimately from the Phoenician alphabet.

Biostratographic significance

The species of the genus Ovatoryctocara occur near the lower limit of the Middle Cambrian in Siberia. The first appearance datum (FAD) of Ovatoryctocara granulata was proposed as the defining marker for the lower limit of the Wuliuan. O. granulata is moderately widespread (East Siberia, South China, Greenland, and Newfoundland).^[2]

First appearance datum is a term used by geologists and paleontologists to designate the first (oldest) appearance of a species in the geologic record. In other words, FADs represent the geologically oldest fossil of a particular species that has so far been discovered.

The Wuliuan stage is the fifth stage of the Cambrian, and the first stage of the Miaolingian Series of the Cambrian. It was formally defined by the ICS in 2018. Its base is defined by the first appearance of the trilobite species Oryctocephalus indicus; it ends with the beginning of the Drumian stage, marked by the first appearance of the trilobite Ptychagnostus atavus around 504.5 million years ago.

Distribution

O. ovata was found in the early Middle Cambrian of the Russian Federation (Ovatoryctocara granulata zone, Nekekit, Malaya Kuonamka, Olenek, Amyday, and Muna rivers, and into the lower Kounamkites zone, Molodo River, East Siberia).
O. angusta ssp. angusta is present in the early Middle Cambrian of the Russian Federation (lower part of the Ovatoryctocara granulata zone, Malaya Kuonamka, and Torkukuy rivers, East Siberia).
O. angusta ssp. snegirevae has been encountered in the early Middle Cambrian of the Russian Federation (Ovatoryctocara granulata zone, Molodo and Malaya Kuonamka Rivers; Amaday Horizon, Maya River, East Siberia).
O. doliiformis has been collected from the early Middle Cambrian of the Russian Federation (upper part of the Ovatoryctocara granulata zone, Molodo River, East Siberia)
O. granulata occurs in the early Middle Cambrian of the Russian Federation (Ovatoryctocara granulata zone, Nekekit, Malaya Kuonamka, Olenek, Amyday, and Muna rivers, and into the lower Kounamkites zone, Molodo River, East Siberia), China (O. granulata– Bathynotus holopyga zone, late Duyunian, Kaili Formation), latest Lower Cambrian of Greenland (upper Olenellus zone, Henson Glacier Formation) and of Canada (top of the Cephalopyge notabilis zone, Branche Cove Marl Member, Eastern Cove Branche, Newfoundland).^[2]

Bathynotus is a genus of trilobites of the family Bathynotidae. Its fossils have been found in the paleocontinents Laurentia, Gondwana, and - doubtfully - Siberia. It is characterized by a very wide axis in the thorax and an enlarged 11th segment that bears a long, backwardly directed spine on each side. Additionally, the 12th and 13th segments are narrow and fuse with the edge of the spine of the 11th segment.

Marocconus 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. Marocconus notabilis is the only known species in this genus.

Description

Very small to small trilobite (maximum length approximately 1 centimetre or 0.39 inches) of more or less oval overall shape. The head shield (or cephalon) has natural fracture lines that end at the tip of the genal angle or the rear margin (or it has gonatoparian or proparian facial sutures). The central area of the cephalon (or glabella) is cylindrical or slightly expanded midlength and/or at the frontal lobe. The furrows that show the segmented origin, are most distinct in the form of four sets of rounded or triangular pits, sometimes with a shallow depression between them at the midline. The glabella is almost touching the front of the cephalon (or the pre-glabellar field is short). Narrow eye ridges emerge from the back of the frontal lobe outward and slightly backward (± 20°). Thorax of 5 or 6 segments. Pygidium approximately the same size (isopygous) or larger (macropygous) than the cephalon, with an axis of 6 to 12 rings, and clear pleural furrows. The border is lacking or hair thin. The surface may be smooth or has granules.^[2]

The cephalon is the head section of an arthropod. It is a tagma, i.e., a specialized grouping of arthropod segments. The word cephalon derives from the Greek κεφαλή (kephalē), meaning "head".

Related Research Articles

Paradoxides is a genus of large to very large trilobites found throughout the world during the Mid Cambrian period. One record-breaking specimen of Paradoxides davidis is 37 cm (15 in). It has a semicircular head, free cheeks each ending with a long, narrow, recurved spine, and sickle-shaped eyes, providing almost 360° view, but only in the horizontal plane. Its elongated trunk was composed of 19-21 segments and was adorned with longish, recurved lateral spines. Its pygidium was comparatively small. Paradoxides is a characteristic Middle Cambrian trilobite of the 'Atlantic' (Avalonian) fauna. Avalonian rocks were deposited near a small continent called Avalonia in the Paleozoic Iapetus Ocean. Avalonian beds are now in a narrow strip along the East Coast of North America, and in Europe.

Eoagnostus is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the terminal Lower Cambrian (Toyonian), until the earliest Middle Cambrian.

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.

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.

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.

Peronopsis is a genus of trilobite restricted to the Middle Cambrian. Its remains have been found in Asia, Australia, Europe, and North America.

Asaphiscus is a genus of trilobite that lived in the Cambrian. Its remains have been found in Australia and North America, especially in Utah.

Lonchodomas is a genus of trilobites, that lived during the Ordovician. It was eyeless, like all raphiophorids, and had a long straight sword-like frontal spine, that gradually transforms into the relatively long glabella. Both the glabellar spine and the backward directed genal spines are subquadrate in section. Lonchodomas has five thorax segments and the pleural area of the pygidium has two narrow furrows. Lonchodomas occurred in what are today Argentina, Canada (Newfoundland), Estonia, Latvia, Norway, the Russian Federation and the United States.

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.

Phalagnostus is a genus of small trilobites, in the order Agnostida. It lived during the Middle Cambrian, in what are now Canada, China, the Czech Republic, Denmark, England, France, the Russian Federation, Wales, Sweden, and possibly the United States (Vermont). The headshield is almost entirely effaced and wider than the tailshield. The pygidium is also very effaced, but the ovate pygidial axis is well defined and a border furrow is also present.

Mallagnostus is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the upper Lower Cambrian, with remains found in USA, Canada (Newfoundland), Spain, England, Russia, Mongolia, and the lower Middle Cambrian according to fossils from China and Russia (Yakutia).

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.

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.

Tchernyshevioides is a diminutive trilobite that lived during the early Middle Cambrian (Amgaian) and has been found in the Russian Federation and the Jbel Wawrmast Formation of Morocco.

Diplorrhina is a genus of trilobites, a well known class of extinct marine arthropods. It lived during the early Middle Cambrian in what are now the Czech Republic and the North Siberian plateau. Like all agnostina it has a headshield (or cephalon and tailshield (or pygidium of approximately the same shape and size, and two thorax segments. Like other members of the Peronopsidae family, it lacks a furrow connecting the furrow surrounding the central raise area of the cephalon and the furrow that defines the border of the cephalon. Both the cephalon and the pygidium lack spines. It is difficult to distinguish from many other peronopsids.

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.

Jinghediscus is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the lover 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 halflength of the body. Cedaria lived during the early part of the Upper Cambrian (Dresbachian), and is especially abundant in the Weeks Formation.

Tricrepicephalus is an extinct genus of ptychopariid trilobites of the family Tricrepicephalidae with species of average size. Its species lived from 501 to 490 million years ago during the Dresbachian faunal stage of the late Cambrian Period. Fossils of Tricrepicephalus are widespread in Late Cambrian deposits in North America, but is also known from one location in South-America. Tricrepicephalus has an inverted egg-shaped exoskeleton, with three characteristic pits in the fold that parallels the margin of the headshield just in front of the central raised area. The articulating middle part of the body has 12 segments and the tailshield carries two long, tubular, curved pygidial spines that are reminiscent of earwig's pincers that rise backwards from the plain of the body at approximately 30°.

Plutonides is a genus of trilobite, an extinct group of marine arthropods. Species occur in the middle Middle Cambrian of Russia (Siberia), Mongolia, England and Wales, Sweden, eastern Canada, and the Czech Republic. The frontal lobe of the central raised area of the headshield overhangs the short frontal border and it is slightly pointed, rather than rounded or truncate. This character is shared with Anabaraspis, but in Anabaraspis there is a wide area in front of the glabella without a differentiated border and preglabellar field.

References

↑ Shergold, J. H. (1969). Oryctocephalidae (Trilobita: Middle Cambrian) of Australia (PDF). Bulletin. 104. Department of National Development: Bureau of Mineral Resoures, Geology and Geophysics. pp. 1–66.
1 2 3 4 Naimark, E.; Shabanov, Y.; Korovnikov, I. (2011). "Cambrian Trilobite Ovatoryctocara Tchernysheva, 1962 from Siberia" (PDF). Bulletin of Geosciences. 86 (3): 405–422. doi:10.3140/bull.geosci.1272.

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[1] Shergold, J. H. (1969). Oryctocephalidae (Trilobita: Middle Cambrian) of Australia (PDF). Bulletin. 104. Department of National Development: Bureau of Mineral Resoures, Geology and Geophysics. pp. 1–66.

[NSK-2] 1 2 3 4 Naimark, E.; Shabanov, Y.; Korovnikov, I. (2011). "Cambrian Trilobite Ovatoryctocara Tchernysheva, 1962 from Siberia" (PDF). Bulletin of Geosciences. 86 (3): 405–422. doi:10.3140/bull.geosci.1272.