Agnostidae is a
family
Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...
of
Agnostida
Agnostida is an order of arthropod 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 Artiopoda. They ar ...
trilobite
Trilobites (; meaning "three lobes") are extinct marine 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 ...
s. Like all Agnostina, they were eyeless and bore only two
thoracic
The thorax or chest is a part of the anatomy of humans, 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 divisions of the crea ...
segments. They ranged in
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 ancient Greek, βένθος (bénthos), meaning "t ...
waters across the globe from 508 to 461 million years ago, containing the following genera, among others:
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Acmarhachis''
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Agnostus''
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Aistagnostus
''Aistagnostus'' is a genus of trilobite in the order Agnostida, which existed in what is now Xinjiang, China. It was described by Xiang and Zhang in 1985, and the type species is ''Aistagnostus laevigatus''.Anglagnostus
''Anglagnostus'' is a genus of trilobite in the order Agnostida, which existed in what is now Shineton, England. It was described by Howell in 1935, and the type species is ''Anglagnostus dux'', which was originally described as a species of ''A ...
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Biciragnostus
''Biciragnostus'' is a genus of trilobite in the order Agnostida, which existed in what is now Kazakhstan
Kazakhstan, officially the Republic of Kazakhstan, is a transcontinental country located mainly in Central Asia and partly in Easter ...
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Connagnostus''
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Distagnostus''
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Eolotagnostus''
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Gymnagnostus''
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Homagnostus''
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Idolagnostus''
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Innitagnostus''
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Ivshinagnostus
''Ivshinagnostus'' is a genus of trilobite in the order Agnostida, which existed in what is now Kazakhstan
Kazakhstan, officially the Republic of Kazakhstan, is a transcontinental country located mainly in Central Asia and partly in Easte ...
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Kymagnostus
''Kymagnostus'' is a genus of trilobite in the order Agnostida, which existed in what is now Arkansas, United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country ...
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Lotagnostus''
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Micragnostus''
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Obelagnostus
''Obelagnostus'' is a genus of trilobite 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 surr ...
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Oncagnostus''
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Peronopsis
''Peronopsis'' (meaning "broach-like" or possibly "boot-like") is a genus of trilobite restricted to the Middle Cambrian. Its remains have been found in Asia, Australia, Europe, and North America.
Etymology
The subgenus ''Svenax'' is a cont ...
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Phalacroma''
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Phalagnostus''
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Quadrahomagnostus
''Quadrahomagnostus'' is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. They lived from 501 to 490 million years ago during the Dresbachian faunal stage of the late Cambrian period
The Cambrian Period ...
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Raragnostus''
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Semagnostus''
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Strictagnostus''
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Trilobagnostus''
References
Agnostoidea
Trilobite families
Cambrian first appearances
Middle Ordovician extinctions
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