| Pseudogygites | |
|---|---|
 | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | † Trilobita |
| Order: | † Asaphida |
| Family: | † Asaphidae |
| Genus: | †Pseudogygites Kobayashi, 1934 |
| Type species | |
| Asaphus canadensis Chapman, 1856 | |
Pseudogygites is an extinct genus of trilobites from the Middle and Upper Ordovician. [1]
The pygidium and the cephalon are about equal in size and shape. The glabella is expanded forward, reaching to the anterior margin. Pseudogygites has short genal spines and small compound eyes located in the center of the cephalon with the glabella in between. The pygidium contains faint pleural furrows and no axial rings. [1] Pseudogygites species can reach 25 centimetres (10 in) in length and 10 cm (4 in) in width. [1]
Pseudogygites is found in late Ordovician oil shales in New York, Ontario, and Southampton Island in the Canadian Arctic. [1] Pseudogygites species are known from exposures of the Billings Shale and Blue Mountain formations.[ citation needed ]
Four species have been described:
Phacopidae is a family of phacophid trilobites that ranges from the Lower Ordovician to the Upper Devonian, with representatives in all paleocontinents.
Dalmanites is a genus of trilobite in the order Phacopida. They lived from the Late Ordovician to Middle Devonian.
Deiphon is a distinctive genus of Silurian phacopid trilobites of the family Cheiruridae found in Western and Central Europe, and in Central and Eastern United States. The type species, D. forbesi, from England, Bohemia, and Sweden, was discovered and described by the French paleontologist, Joachim Barrande in 1850.
Triarthrus is a genus of Upper Ordovician ptychopariid trilobite found in New York, Ohio, Kentucky, and Indiana, eastern and northern Canada, China and Scandinavia. It is the last of the Olenid trilobites, a group which flourished in the Cambrian period. The specimens of T. eatoni that are found in the Beecher's Trilobite Bed, Rome, New York area are exquisitely preserved showing soft body parts in iron pyrite. Pyrite preservation has given scientists a rare opportunity to examine the gills, walking legs, antennae and digestive systems of trilobites, which are rarely preserved. Triarthrus is therefore commonly used in science texts to illustrate trilobite anatomy and physiology.
Olenoides was a trilobite from the Cambrian period. Its fossils are found well-preserved in the Burgess Shale in Canada. It grew up to 10 cm long.
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.
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, the Russian Federation and the United States.
Pagetia is a genus of very small, agnostid trilobites, assigned to the family Eodiscidae, and that had a global distribution during the Middle Cambrian. The genus contains 55 currently recognized species, each with a limited spatial and temporal distribution.
Chancia is an extinct genus of Cambrian trilobite. It was a "fast-moving epifaunal detritivore" from Canada and the United States. Chancia was a particle feeder. Its major characteristics are a normal glabella but an enlarged cephalon due to a pre-glabellar field in front of the glabella, as well as developed eye ridges, medium-sized genal spines, and an extremely small pygidium.
Soomaspis is a genus of small to average size marine arthropods in the Liwiidae Family, that lived during the late Ordovician. Fossil remains of Soomaspis were collected from the Soom Shale Lagerstätte in Western Cape, South Africa. Soomaspis looks like a large, soft agnostid trilobite. It has a headshield wider than the tailshield (pygidium), and in between them three thoracic body segments (somites). The genus is monotypic, its sole species being Soomaspis splendida.
Pseudonaraoia is a genus of small marine arthropods within the family Naraoiidae, that lived during the late Middle Ordovician period. The only species presently known is Pseudonaraoia hammanni.
Galbagnostus is an extinct genus of agnostid trilobite. It lived during the Lower and Middle Ordovician.
Ogygiocarella is a genus of asaphid trilobites. It occurred during the Middle Ordovician.
Thoracocare is a minute to very small trilobite, that lived during part of the Middle Cambrian in what are today the states of Idaho, Nevada and Utah. It is the only trilobite known with just two thorax segments outside most members of the Agnostida order. It can be distinguished from Agnostida by the very wide subquadrate glabella, parallel-side or widening forward in the largest specimen, with the full front side touching the border. Two species are known, one, T. idahoensis, only from pygidia.
Pleuroctenium is a genus of very small agnostid trilobites whose fossils are found in Middle Cambrian-aged marine strata of Canada, Czech Republic, England and Wales, France, and Sweden. Species of Pleuroctenium can be easily distinguished from all other agnostids because the frontal lobe of the central raised area of the headshield is wider than and folds around the rear lobe.
Diplorrhina is a genus of trilobites, a well known class of extinct marine arthropods. It lived during the early Middle Cambrian in what are now the Czech Republic and the North Siberian plateau. Like all agnostina it has a headshield (or cephalon and tailshield (or pygidium of approximately the same shape and size, and two thorax segments. Like other members of the Peronopsidae family, it lacks a furrow connecting the furrow surrounding the central raise area of the cephalon and the furrow that defines the border of the cephalon. Both the cephalon and the pygidium lack spines. It is difficult to distinguish from many other peronopsids.
Geragnostus is a genus of very small agnostid trilobites whose fossils are found Ordovician-aged marine strata from Eurasia, North America and Argentina.
Cyclopyge is a genus of small to average size trilobites that lived during the Ordovician. Like all members of the family Cyclopigidae, it has very large convex eyes, that cover most of the free cheeks, and in some species touch each other. The eyes almost touch the large glabella. The occipital ring has merged with the rest of the glabella. The glabella does not extend into a frontal thorn. The cephalon lacks genal spines. The 6 thorax segments have short pleurae. The pygidium is rather large, and often rather effaced. These are features that also occur in other Cyclopygidae, and are indications of a pelagic lifestyle.
Illaenus crassicauda is a species of trilobites belonging to the family Illaenidae. These trilobites lived in the middle Ordovician and in the Silurian age. Fossils of this species have been found in the sediments of Sweden and Russia.
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