Trilobites 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 Atdabanian stage of the Early Cambrian period and they flourished throughout the lower Paleozoic before slipping into a long decline, when, during the Devonian, all trilobite orders except the Proetida died out. The last trilobites disappeared in the mass extinction at the end of the Permian about 251.9 million years ago. Trilobites were among the most successful of all early animals, existing in oceans for almost 270 million years, with over 22,000 species having been described.
Dalmanites is a genus of trilobite in the order Phacopida. They lived from the Late Ordovician to Middle Devonian.
Globampyx is an extinct genus raphiophorid trilobites. It lived during the later part of the Arenig stage of the Ordovician Period, approximately 478 to 471 million years ago. Species of the genus are known from Canada, Norway (Svalbard) and Sweden.
Pytine is an extinct genus of asaphid trilobites. Species lived during the later part of the Arenig stage of the Ordovician Period, approximately 478 to 471 million years ago. Various species are found in the Svalbard, Valhallfonna Formation, Olenidsletta, Member, of Spitzbergen, Norway, the Megistaspis (Paramegistaspis) planilimbata Zone of the 'Shumardia Shale' of Sweden, Jujuy Province, Argentina, early Arenig-aged strata of Jiangxi province, China, and Darriwilian-aged strata in Western Hunan province, China. The type species, P. graia, has seven thorax segments, and lacks the rapier-like glabellar spine, that occurs in many other raphiophorids. The Chinese species, by contrast, have only six thoracic segments. So far, only the type species, and one of the Chinese species, P. laevigata, are known from complete specimens.
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, Sweden, the Russian Federation and the United States.
Illaenus is a genus of trilobites from Russia and Morocco, from the middle Ordovician.
Eodiscina is trilobite suborder. The Eodiscina first developed near the end of the Lower Cambrian period 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.
Trinodus is a very small to small blind trilobite, a well known group of extinct marine arthropods, which lived during the Ordovician, in what are now the Yukon Territories, Virginia, Italy, Czech Republic, Poland, Denmark, Sweden, Svalbard, Ireland, Scotland, Wales, Iran, Kazakhstan and China. It is one of the last of the Agnostida order to survive.
Galbagnostus is an extinct genus of agnostid trilobite. It lived during the Lower and Middle Ordovician.
Prospectatrix is a genus of trilobites of average size, that lived in the Lower Ordovician and is probably ancestral to the other genera of the Cyclopygidae family. Its eyes are only moderately enlarged and it has six or seven thorax segments.
Cyclopygidae is a family of asaphid trilobites from the Ordovician. Cyclopygids had an extratropical distribution, and there is evidence that they lived in darker parts of the water column. Cyclopygids are characterized by enlarged eyes, with a wide angle of view, both horizontal and vertical, reminiscent of the eyes of dragonflies. These typically touch the glabella directly on the side. Cyclopygids all lack genal spines, but Symphysops carries a forward directed frontal spine on the glabella. It is presumed that at least the members of the genus Pricyclopyge swam upside down and had bioluminescent organs on the third thorax segment. Cyclopygids had between 7 and 5 thorax segments, a wide and stout axis, and short side lobes.
Carolinites is a genus of trilobite, assigned to the Telephinidae family, that occurs during the Lower and Middle Ordovician. Carolinites had a pantropical distribution, and there is evidence that it lived in upper parts of the water column. The free cheeks of Carolinites are largely covered by its huge eyes, except for the attachment of large genal spines that extend downward, backward and lateral and gradually curving further backward. The glabella is slightly bulbous, the occipital ring is well defined, but further transglabellar furrows are lacking. The thorax has 10 segments. The axis of the pygidium is highly vaulted, with a curved spine emerging almost perpendicular to the midline and ending parallel to it and a node on each of the other three segments. Carolinites is known from what are today Australia (Tasmania), Canada (Alberta), China, France, Spitsbergen, and the United States (Utah).
Taklamakania is a genus of asaphid trilobites of the family Raphiophoridae that lived during the late Caradoc of Inner Mongolia, China. Like all raphiophorids it is blind, with a headshield that is subsemicircular, carrying genal spines and a forward directed spine on the central raised area, with the front of the glabella inflated and the natural fracture lines of the cephalon coinciding with its margin. It is easily distinguished from most other raphiophorids by the 3 thorax segments. Pseudampyxina, Nanshanaspis, and Kongqiangheia also have only 3 such segments, but all three lack the frontal spine that emanates from the glabellum of Taklamakania species. All other raphiophorid genera have at least 5 thorax segments. Three species, T. tarimensis, T. tarimheensis, and T. xinjiangensis, have been assigned to this genus so far.
The Illaenidae are a family of trilobites in the order Corynexochida. 223 currently accepted species in 24 genera are known from the Ordovician. Some scholars include the Panderiidae in the Illaenidae, but this is not generally supported.
Gog is a genus of large, flattened asaphid trilobite from the Middle Arenig-aged Svalbard, Valhallfonna Formation, Olenidsletta, Member, of Spitzbergen, Norway, and the Upper Arenig-aged Dawan Formation in Hubei, China.
Telephinidae is a family of pelagic trilobites with large wide-angle eyes, occupying most of the free cheeks, downward directed facial spines and 9-10 thorax segments. The family is known during the entire Ordovician and occurred in deep water around the globe.
Bulbaspis is a late Ordovician genus of asaphid trilobites of the family Raphiophoridae found primarily in upper Ordovician-aged deepwater marine strata of Kazakhstan, China, and possibly Tasmania. Species of Bulbaspis are similar to other raphiophorids such as Ampyx and Raphiophorus, save that the long spine that emanates from the glabella of the latter two genera has been modified into a knob-like or bulb-like structure in Bulbaspis that developed incrementally in the animal's growth. The function of the bulb is currently unknown: one hypothesis suggests sexual selection may have had a role in its evolution in the genus.
Nanshanaspis is a genus of asaphid trilobites of the family Raphiophoridae that lived during the late Caradoc of Inner Mongolia, China. Like all raphiophorids it is blind, with a headshield that is subsemicircular, carrying genal spines and a forward directed spine on the central raised area, with the front of the glabella inflated and the natural fracture lines of the cephalon coinciding with its margin. It is easily distinguished from most other raphiophorids by the 3 thorax segments. Pseudampyxina, Taklamakania, and Kongqiangheia also have only 3 such segments, while all other raphiophorid genera have at least 5 thorax segments, leading to the erection of the subfamily "Taklamakaniinae" to contain these four genera. "Taklamakaniinae" was dissolved and its members absorbed into Raphiophorinae when further study showed the close similarities the "taklamakaniids" had to the juvenile forms of various raphiophorinids. Specimens of Nanshanaspis, for example, closely resemble juveniles of Globampyx trinucleoides.
Typhlokorynetes plana is a species of small, button-shaped asaphid trilobites of the family Raphiophoridae that lived during the Early Tremadocian of Vermont, United States.
Trinucleioidea is a superfamily of trilobites. Traditionally placed within the Asaphida, it is now sometimes considered its own order, Trinucleida.
