Nektaspida is an extinct order of soft-bodied arthropods proposed by Raymond in 1920; its taxonomic status is uncertain. Specimens are known from the early Cambrian to the upper Silurian periods. Whittington (1985) placed the order in the Trilobita. Cotton & Braddy (2000) place it in a new "Trilobite clade" containing the Trilobita, recognizing the close affinities of the nektaspids to trilobites. However this necessitates the inclusion of genera that look very little like trilobites. Strictly speaking, it is best placed in the stem-group to the chelicerata subdivision of the Arthropoda phylum.
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, but no suborders. Asaphids comprise some 20% of described fossil trilobites.
Phacops is a genus of trilobites in the order Phacopida, family Phacopidae, that lived in Europe, northwestern Africa, North and South America and China from the Early until the very end of the Devonian, with a broader time range described from the Late Ordovician. It was a rounded animal, with a globose head and large eyes, and probably fed on detritus. Phacops is often found rolled up, a biological defense mechanism that is widespread among smaller trilobites but further perfected in this genus.
Isotelus is a genus of asaphid trilobites from the middle and upper Ordovician period, fairly common in the Northeastern United States, northwest Manitoba, southwestern Quebec and southeastern Ontario. One species, Isotelus rex, is currently the world's largest trilobite ever found as a complete fossil.
Arachnomorpha is a subdivision or clade of Arthropoda, comprising the monophyletic group formed by the trilobites, other great appendage arthropods and trilobite-like families, and a diverse sister clade including the chelicerates. Great debate is held on the position of the Pycnogonida, which are currently thought not to be placed in the immediate vicinity of the Chelicerata. Arachnomorpha are considered the sister group to the crustaceans, which are increasingly being accepted as members of the mandibulate clade.
Greenops is a mid-sized Devonian trilobite of the order Phacopida, subfamily Asteropyginae. They are mainly reported from the mid-Devonian Hamilton Group of upstate New York and southwestern Ontario. A similar-looking trilobite from Morocco is often mis-labelled Greenops. Greenops had schizocroidal eyes, large genal spines and short, sharp spines at the tip of each segment of the pygidium ("tail"). Greenops lived in warm, fairly deep water. In the Hamilton Group of New York, they are found with Phacops, Dipleura and Bellacartwrightia, a trilobite that resembles Greenops but has much larger pygidial spines. In Ontario, they are found in the Widder Formation, which outcrops at Arkona, where they are, by far, the dominant trilobite.
Beecher's Trilobite Bed is a Konservat-Lagerstätte of Late Ordovician (Caradoc) age located within the Frankfort Shale in Cleveland's Glen, Oneida County, New York, USA. Only 3-4 centimeters thick, Beecher's Trilobite Bed has yielded numerous exceptionally preserved trilobites with the ventral anatomy and soft tissue intact, the soft tissue preserved by pyrite replacement. Pyritisation allows the use of X-rays to study fine detail of preserved soft body parts still within the host rock. Pyrite replacement of soft tissue is unusual in the fossil record; the only Lagerstätten thought to show such preservation were Beecher's Trilobite Bed, the Devonian Hunsrück Slates of Germany, and the Jurassic beds of La Voulte-sur-Rhône in France, although new locations are coming to light in New York state.
Calymenella is a genus of trilobites in the order Phacopida, which existed in what is now France during the upper Ordovician. It was described by Bergeron in 1890, and the type species is Calymenella boisseli. The species was described from the Glauzy Formation in the Montagne Noire mountain range.
Calymenesum is a trilobite in the order Phacopida that existed in what is now China during the middle Ordovician. It was described by Kobayashi in 1951, and the type species is Calymenesum tingi, originally described under the genus Calymene by Sun in 1931. The species was described from the Shistzupu Formation in Guizhou, China.
Chasmops is a trilobite in the order Phacopida that existed during the upper Ordovician in what is now Estonia. It was described by McCoy in 1849, and the type species is Chasmops odini, which was originally described under the genus Calymene by Eichwald in 1840. It also contains the species C. maxima.
Encrinuroides is a genus of trilobites in the order Phacopida, that existed during the upper Ordovician in what is now Wales. It was described by Reed in 1931, and the type species is Encrinuroides sexcostata, which was originally described under the genus Cybele by Salter in 1848. It also contains the species, Encrinuroides enshiensis, Encrinuroides insularis, and Encrinuroides rarus. The type locality was in the Sholeshook Limestone Formation.
The Walcott–Rust quarry is an excellent example of an obrution Lagerstätte. Unique preservation of trilobite appendages resulted from early consolidation (cementation) of the surrounding rock, followed by spar filling of the interior cavity within the appendages. The presence of so many well preserved trilobites in one location alone qualifies the beds as an exceptional trilobite site, but the beds are further distinguished as the source of the first trilobites for which appendages were definitively described.
The cephalon is the head section of an arthropod. It is a tagma, i.e., a specialized grouping of arthropod segments. The word cephalon derives from the Greek κεφαλή (kephalē), meaning "head".
Homagnostus is a genus of trilobite in the order Agnostida, which existed in what is now north Wales. It was described by Howell in 1935. The genus was originally considered to be Agnostus pisiformis var. obesus.
Micragnostus is a genus of trilobite in the order Agnostida, which existed in what is now north Wales. It was described by Howell in 1935, and the type species is Micragnostus calvus, which was originally described as a species of Agnostus by Lake in 1906.
Phalacroma is a genus of trilobite in the order Agnostida, which existed in what is now the Czech Republic. It was described by Hawle and Corda in 1867, and the type species is Phalacroma bibullatus, which was originally described as a species of Battus by Barrande in 1846.
Bumastus is an extinct genus of corynexochid trilobites which existed from the Early Ordovician period to the Late Silurian period. They were relatively large trilobites, reaching a length of 6 in (15 cm). They were distinctive for their highly globular, smooth-surfaced exoskeleton. They possessed well-developed, large compound eyes and were believed to have dwelled in shallow-water sediments in life.
Lejopyge laevigata is a species of agnostid trilobite belonging to the genus Lejopyge. It existed during the Guzhangian to the Paibian Age of the Cambrian. It has a cosmopolitan distribution and is an important index fossil in biostratigraphy.
Paleontology in Wisconsin refers to paleontological research occurring within or conducted by people from the U.S. state of Wisconsin. Wisconsin has a relatively sparse fossil record. Fossils found in Wisconsin are generally very old, most ranging from 500 to 300 million years in age. During the early part of the Paleozoic era, Wisconsin was covered by a warm, shallow sea that would be home to creatures like brachiopods, bryozoans, cephalopods, corals, crinoids, and trilobites. During the Silurian, Wisconsin was home to massive reef system that formed one of the most biodiverse habitats in all of North America at the time. The interval spanning the Permian, Mesozoic, Paleogene and Neogene are missing from the local rock record. During the Ice Age the local climate became cold. Seals, walruses, and whales left behind fossil remains in the state near the Great Lakes. On land, hemlock and spruce trees formed forests inhabited by creatures like giant beavers, horses, and woolly mammoths. The first fossil reef systems ever scientifically documented in North America were discovered in the area around Milwaukee. The Silurian reefs of the Milwaukee area were also the first known fossil reefs from the Paleozoic era. Their associated fauna is one of the most diverse from the period ever documented in North America. The Ordovician to Silurian trilobite Calymene celebra is the Wisconsin state fossil.
