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Trilobites are an extinct group of arthropods, so named because their body is divided lengthwise into 3 lobes (right, middle, left). Their bodies also usually have 3 distinct regions, the head, thorax, and tail (pygidium). Trilobites were most diverse in the Cambrian and Ordovician Periods and were abundant up through the end of the Devonian. After that they were rare until their final extinction at the end of the Permian.
Olenellus gilberti dates to the early Cambrian Period.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Redlichiida
Pioche Formation, Lincoln Co., Nevada
Early Cambrian, 530 Ma
Denver Museum of Science & Nature
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Acadoparadoxides briareus.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Redlichiida
Jbel Wawrmast Formation, Anti-Atlas Mountains, Morocco
Middle Cambrian, 510 Ma
Black Hills Institute Museum, South Dakota
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Andalusiana sp. trilobite.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Redlichiida
Morocco
Cambrian Period
Chicago Field Museum
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Tiny trilobites, only a few mm long, such as this Peronopsis interstrictus may have been pelagic, swimming in the water column above the bottom.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Agnostida
Millard Co., UT
Cambrian Period
Chicago Field Museum
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Olenoides nevadensis.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Corynexochida
Cambrian Period
Black Hills Institute Museum, South Dakota
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Modocia typicalis.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Ptychopariida
Utah
Cambrian Period
Black Hills Institute Museum, South Dakota
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Conocoryphe sulzeri trilobite fossil.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Ptychopariida
Czech Republic
Cambrian Period
Chicago Field Museum
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Isotelus sp.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Asaphida
Ontario, Canada
Ordovician Period
Black Hills Institute Museum, South Dakota
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Isotelus gigas
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Asaphida
Louisiana and Missouri
Ordovician Period
Chicago Field Museum
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Stalk-eyed trilobites such as this Neoasaphus kowalewskii may have buried themselves in the mud with just their eyes sticking out.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Asaphida
Wolchow River, Russia
Middle Ordovician Period
Black Hills Institute Museum, South Dakota
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Fossil of Asaphus latus
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Asaphida
St. Petersburg, Russia
Ordovician Period
Chicago Field Museum
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A group of Onnia superba trilobites.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Asaphida
Morocco
Ordovician Period
Chicago Field Museum
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Homotelus bromidensis mass death assemblage.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Asaphida
Ordovician Period
Black Hills Institute Museum, South Dakota
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Homotelus bromidensis mass death assemblage.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Asaphida
Carter Co., OK
Ordovician Period
Chicago Field Museum
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Dikelokephalina sp. mass death assemblage.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Asaphida
Morocco
Early Ordovician Period, 475 Ma
Wyoming Dinosaur Center
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Hoplolichas furcifer fossil.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Lichida
St Petersburg, Russia
Ordovician Period
Chicago Field Museum
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Selenopeltis bucchi trilobites.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Odontopleurida
Ktaoua Formation, Morocco
Ordovician Period
Black Hills Institute Museum
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Paraceraurus exsull trilobite
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Phacopida
St Petersburg, Russia
Ordovician Period
Chicago Field Museum
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Gabriceraurus sp.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Phacopida
Ottawa, Ontario
Ordovician Period
Chicago Field Museum
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Cybele panderi trilobite fossil
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Phacopida
St Petersburg, Russia
Ordovician Period
Chicago Field Museum
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Kolihapeltis rabatensis trilobite
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Corynexochida
Erfud, Morocco
Devonian Period
Chicago Field Museum
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Thysanopeltis speciosa fossil.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Corynexochida
Morocco
Devonian Period
Chicago Field Museum
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The long spines of Ceratarges spinosus and other trilobites probably served as defense against predators.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Lichida
Morocco
Devonian Period
Chicago Field Museum
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Some trilobites, especially during the Devonian Period, developed elaborate horns and spines, presumably for defense. This is Dicranurus monstrosus.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Odontopleurida
Morocco
Middle Devonian Period
Museum of Ancient Life, Utah
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Koneprusia brutoni trilobite fossil.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Odontopleurida
Morocco
Devonian Period
Chicago Field Museum
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Phacops rana death assemblage.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order tbd
Sylvania, OH
Silica Shale; Middle Devonian Period
Museum of Ancient Life, Utah
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Burmeisterella sp.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order tbd
Morocco
Early Devonian Period
Museum of Ancient Life, Utah
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Psychopyge sp. The function of its elongated "snout" is uncertain, but may have had a sensory function.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order tbd
Morocco
Devonian Period
Museum of Ancient Life, Utah
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The trident horns of Walliserops trifurcates may have functioned as sensory structures, defense, or in male-male combat.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order tbd
Morocco
Devonian Period, 375 Ma
Wyoming Dinosaur Center
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Another example of Walliserops trifurcates.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Phacopida
Morocco
Devonian Period
Chicago Field Museum
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Kayserops megaspina fossil.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Phacopida
Morocco
Devonian Period
Chicago Field Museum
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Cordania wessmani trilobite fossil
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Proetida
Coal Co., OK
Devonian Period
Chicago Field Museum
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The Order Proetida was the only group of trilobites to survive the late Devonian extinction event. After the Devonian, trilobites, such as thisGriffithides bufo, were rare.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Proetida
Crawfordsville, Indiana
Carboniferous Period
Chicago Field Museum
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The Permian was the last period with trilobites. They went extinct at the end of the Permian. Ditomopyge decurtata is thus one of the last trilobites.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Proetida
Wichita, Kansas
Permian Period
Chicago Field Museum
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Silurian trilobites, including Gravicalymene celebra (far left) and Bumastus ioxus (top left)
Middle Silurian Period, 425 Ma; Wisconsin
Denver Museum of Science & Nature
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Life model of the trilobite Olenoides sp.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Corynexochida
Cambrian Period
Museum of Ancient Life, Utah
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Life modelsof the trilobite Phacops rana, one of which is enrolled.
Taxonomy: Subphylum Trilobitomorpha; Class Trilobita; Order Phacopida
Middle Devonian Period; Ohio
Museum of Ancient Life, Utah
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