Cambrian trilobites

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 Artiopoda. They are present in the Lower Cambrian fossil record along with trilobites from the Redlichiida, Corynexochida, and Ptychopariida orders, and were highly diverse throughout the Cambrian. Agnostidan diversity severely declined during the Cambrian-Ordovician transition, and the last agnostidans went extinct in the Late Ordovician.

alt=Akantharges trilobite fossil|thumb|Akantharges

Asaphida is a large, morphologically diverse order of trilobites found in marine strata dated from the Middle Cambrian until their extinction during the Silurian. Asaphida contains six superfamilies (Anomocaroidea, Asaphoidea, Cyclopygoidea, Dikelocephaloidea, Remopleuridoidea and Trinucleioidea), but no suborders. Asaphids comprise some 20% of described fossil trilobites.

Redlichiida is an order of trilobites, a group of extinct marine arthropods. Species assigned to the order Redlichiida are among the first trilobites to appear in the fossil record, about halfway during the Lower Cambrian. Due to the difficulty to relate sediments in different areas, there remains some discussion, but among the earliest are Fallotaspis (suborder Olenellina), and Lemdadella (suborder Redlichiina), both belonging to this order. The first representatives of the orders Corynexochida and Ptychopariida also appear very early on and may prove to be even earlier than any redlichiid sp

Olenellus is an extinct genus of redlichiid trilobites, with species of average size (about long). It lived during the Botomian and Toyonian stages of the Lower Cambrian (Olenellus-zone), , in what is currently North America, part of the palaeocontinent Laurentia.

Redlichia is a genus of redlichiid trilobite in the family Redlichiidae, with large to very large species (up to long). Fossils of various species are found in Lower Cambrian (Toyonian)-aged marine strata from China, Korea, Pakistan, the Himalayas, Iran, Spain, southern Siberia, and Antarctica, and from Middle Cambrian (Ordian)-aged marine strata of Australia.

Paradoxides is a genus of large to very large trilobite found throughout the world during the Middle Cambrian period. One record-breaking specimen of Paradoxides davidis, described by John William Salter in 1863, is . The cephalon was semicircular with free cheeks ending in long, narrow, recurved spines. Eyes were crescent shaped providing an almost 360° view, but only in the horizontal plane. Its elongate thorax was composed of 19–21 segments and adorned with longish, recurved pleural spines. Its pygidium was comparatively small. Paradoxides is a characteristic Middle-Cambrian trilobite of th

thumb|right|250px|Elrathia kingii growth series with holaspids ranging from 16.2 mm to 39.8 mm in length

Olenoides is a genus of trilobite from the Cambrian period. Its fossils can be found with soft body parts intact in the Burgess Shale in Canada. Fossils of this genus can also be found in the Wheeler Shale and Marjum Formation of Utah in the United States of America, among other localities. Species within this genus range in size, with most being medium-sized trilobites (Olenoides Serratus from the Burgess Shale can be up to 9 centimeters in length). Specimens of Olenoides Superbus, pictured on the right, an especially large species, can reach sizes of well over 10 centimeters in length. Oleno

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.

Olenellina is a suborder of the order Redlichiida of trilobites that occurs about halfway during the Lower Cambrian, at the start of the stage called the Atdabanian. Olenellina are arguably the earliest trilobites in the fossil record as members of Redlichiina, although Ptychopariida and Eodiscina follow soon after. The suborder died out when the Lower Cambrian passed into the Middle Cambrian, at the end of the stage called Toyonian. A feature uniting the Olenellina is the lack of rupture lines (or sutures) in the headshield, which in other trilobites assist the periodic moulting (or ecdysis),

Ellipsocephalus Zenker, 1833, is a genus of blind Cambrian trilobite, comprising benthic species inhabiting deep, poorly lit or aphotic habitats. E. hoffi is a common trilobite mainly from central Europe (Czech Republic).

Redlichiina is a suborder of the order Redlichiida of trilobites. The suborder contains three superfamilies: Emuelloidea, Redlichioidea and Paradoxidoidea. These trilobites are some of the oldest trilobites known. They originated at the beginning of the Cambrian Period and disappeared (possibly by evolving into members of the Ptychopariida order) at the end of the middle Cambrian.

Ogygopsis is a genus of trilobite from the Cambrian of Antarctica and North America, specifically the Burgess Shale. It is the most common fossil in the Mt. Stephen fossil beds there, but rare in other Cambrian faunas. Its major characteristics are a prominent glabella with eye ridges, lack of pleural spines, a large spineless pygidium about as long as the thorax or cephalon, and its length: up to 12 cm. File:Ogygopsis reconstruction.jpg|Reconstruction of Ogygopsis klotzi in the Burgess Shale File:Royal Tyrrell Ogygopsis klotzi.jpg|At the Royal Tyrrell Museum of Palaeontology

Eodiscina is trilobite suborder. The Eodiscina first developed near the end of the Lower Cambrian period (late Atdabanian) 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.

The ”Fallotaspidoidea” are a superfamily of trilobites, a group of extinct marine arthropods. It lived during the Lower Cambrian (Atdabanian) and species occurred on all paleocontinents except for the Gondwana heartland (currently Latin America, most of Africa, Australia, Antarctica, India and China). A member of this group, Profallotaspis jakutensis, has long been the earliest known trilobite, but recently the redlichiid Lemdadella has been claimed as occurring even earlier.

Eoredlichia is an extinct genus of trilobite of average to large size (up to long, or when including the spine on the ninth thorax segment pointing horizontally to the back, that itself equals the main body length). It lived during the early Cambrian (late Atdabanian) in the Chengjiang fauna of Yunnan, China, and in Australia and Thailand. Eoredlichia is compounded of the Greek (eos, dawn) and Redlichia, a later but related genus, so it means "early Redlichia". The species epithet intermedia means intermediate, indicating it is morphologically intermediate between other species. Eofallotaspis

thumb|left|Kootenia assemblage at the Geological Museum in Copenhagen

Emuella is a genus of Cambrian trilobites of the family Emuellidae. Its fossils have been found in South Australia.

Yukoniidae S. Zhang, 1980 [nom. transl. et emend. Jell, in Whittington et al., 1997 ex Yukoniinae S. Zhang in W. Zhang, Lu et al., 1980] is a small family of trilobites, belonging to the Eodiscina.

fossil genus of trilobites

Conocoryphe is a genus of primarily eyeless trilobites belonging to the family Conocoryphidae. They lived during the Middle Cambrian period, about 505 million years ago. These arthropods lived on the sea bottom (epifaunal) and lived off dead particulate organic matter (a lifestyle called detritivorous).

Xystridura is a genus of redlichiid trilobite described originally from the Middle Cambrian (Miaolingian) strata of Queensland, Australia. The genus ranges upwards from Ordian into Florian Stages in terms of Australian Cambrian stratigraphic nomenclature.

Yunnanocephalus is a genus of ptychopariid trilobite. It lived during the late Atdabanian and Botomian stages, in what are currently Antarctica, Australia and China. It was a "moderately common" member of the Chengjiang Fauna.

Eodiscidae is a family of agnostid trilobites that lived during the final Lower Cambrian (late Toyonian) and the Middle Cambrian. They are small or very small, and have a thorax of two or three segments. Eodiscidae includes nine genera (see box).

The Paradoxididae are a family of trilobites, a group of extinct marine arthropods. They occurred during the late Lower Cambrian (Toyonian) and disappeared at the end of the Middle Cambrian. Representatives of this family have been found in the paleocontinents of Avalonia, Baltica, and Gondwana, now Canada (Nova-Scotia, New Brunswick, Newfoundland), USA (Massachusetts, South Carolina), England, Wales, Morocco, Spain, Czech Republic, Poland, Russia (Novaya Zemlya, Northern Siberia, North-East Yakutia), Mongolia, and Turkey. Species in this family can typically grow large to very large (over 30&

Redlichiidae is a family of redlichiid trilobites which lived from the Botomian to the Middle Cambrian period. It contains the following genera, divided between five subfamilies:

Nevadia is an extinct genus of redlichiid trilobites, with species of average size (about long). It lived during the Atdabanian stage, which lasted from 530 to 524 million years ago, in what are today Western Canada, the Western United States, and Mexico.

Emuellidae are a small family of trilobites, a group of extinct marine arthropods, that lived during the late Lower Cambrian (late Botomian) of the East Gondwana supercontinent, in what are today South-Australia and Antarctica.

Trinucleioidea is a superfamily of trilobites. Traditionally placed within the Asaphida, it is now sometimes considered its own order, Trinucleida. thumb|Damghanampyx ghobadipour fossil from Lashkark Formation, Ordovician, Damghan, Iran

Abakania is an extinct genus of corynexochid trilobite in the family Corynexochidae. It lived during the Botomian stage, which lasted from approximately 524 to 518.5 million years ago. This faunal stage was part of the Cambrian Period.

The Paradoxidoidea Hawle & Corda 1847, are a superfamily of trilobites, a group of extinct marine arthropods. They occurred during the late Lower Cambrian (Toyonian) and disappeared at the end of the Middle Cambrian.