Agnostidae is a

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Agnostida Agnostida are an order of extinct arthropods which have classically been seen as a group of highly modified trilobites, though some recent research has doubted this placement. Regardless, they appear to be close relatives as part of the Artiopod ...

trilobite Trilobites (; meaning "three-lobed entities") are extinction, extinct marine arthropods that form the class (biology), class Trilobita. One of the earliest groups of arthropods to appear in the fossil record, trilobites were among the most succ ...

s. Like all Agnostina, they were eyeless and had only two

thoracic The thorax (: thoraces or thoraxes) or chest is a part of the anatomy of mammals and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main ...

segments. These trilobites inhabited

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from the Ancient Greek word (), meaning "the depths". ...

waters worldwide from 508 to 461 million years ago. The family includes the following genera, among others: *''

Acmarhachis ''Acmarhachis'' is a genus of trilobites in the order Agnostida, which lived in what are now Australia (Queensland, Tasmania), Canada (British Columbia, Newfoundland, Northwest Territories), China (Anhui), Kazakhstan, Russia (Kharaulakh), and the ...

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Agnostus ''Agnostus'' is a genus of agnostid trilobites, belonging to the family Agnostidae, that lived during the late Middle Cambrian – Upper Cambrian (about 506 to 485 million years ago). It is the type genus of the family (biology), family Agnostida ...

'' *'' Aistagnostus'' *'' Anglagnostus'' *''

Biciragnostus ''Biciragnostus'' is a genus of trilobites in the order Agnostida, which existed in what is now Kazakhstan Kazakhstan, officially the Republic of Kazakhstan, is a landlocked country primarily in Central Asia, with a European Kazakhstan, sma ...

'' *'' Connagnostus'' *'' Distagnostus'' *''

Eolotagnostus ''Eolotagnostus'' is a genus of trilobites in the order Agnostida, which existed in what is now Gansu, China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population excee ...

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Gymnagnostus ''Gymnagnostus'' is a genus of trilobites in the order Agnostida, which existed in what is now Oaxaca Oaxaca, officially the Free and Sovereign State of Oaxaca, is one of the 32 states that compose the political divisions of Mexico, Federati ...

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Homagnostus ''Homagnostus'' is a genus of trilobites in the order Agnostida, which existed in what is now north Wales Wales ( ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by the Irish Sea to the ...

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Idolagnostus ''Idolagnostus'' is a genus of trilobites in the order Agnostida, which existed in what is now Queensland, Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Au ...

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Innitagnostus ''Innitagnostus'' is a genus of trilobites in the order Agnostida, which existed in what is now Queensland, Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the A ...

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Ivshinagnostus ''Ivshinagnostus'' is a genus of trilobites in the order Agnostida, which existed in what is now Kazakhstan Kazakhstan, officially the Republic of Kazakhstan, is a landlocked country primarily in Central Asia, with a European Kazakhstan, sma ...

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Kymagnostus ''Kymagnostus'' is a genus of trilobites in the order Agnostida, which existed in what is now Arkansas Arkansas ( ) is a landlocked state in the West South Central region of the Southern United States. It borders Missouri to the north, ...

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Lotagnostus ''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 tris ...

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Micragnostus ''Micragnostus'' is a genus of trilobites in the order Agnostida, which existed in what is now north Wales. It was described by Howell in 1935, and the type species is ''Micragnostus calvus'', which was originally described as a species of ''Agno ...

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Obelagnostus ''Obelagnostus'' is a genus of trilobites in the order Agnostida, which existed in what is now Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and ...

'' *'' Oncagnostus'' *''

Phalacroma ''Phalacroma'' is a genus of trilobite in the order Agnostida, which existed in what is now the Czech Republic The Czech Republic, also known as Czechia, and historically known as Bohemia, is a landlocked country in Central Europe. The co ...

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Phalagnostus ''Phalagnostus'' is a genus of small trilobites, in the order Agnostida. It lived during the Middle Cambrian, in what are now Canada (Newfoundland and Northwest Territories), China, the Czech Republic, Denmark, England, France, the Russian Federa ...

'' *'' Quadrahomagnostus'' *'' Raragnostus'' *'' Semagnostus'' *'' Strictagnostus'' *'' Trilobagnostus''

References

Agnostoidea Trilobite families Cambrian first appearances Middle Ordovician extinctions {{agnostida-stub