Agnostida is an order of arthropod which first developed near the end of the Early Cambrian period and thrived during the Middle Cambrian. They are present in the Lower Cambrian fossil record along with trilobites from the Redlichiida, Corynexochida, and Ptychopariida orders. The last agnostids went extinct in the Late Ordovician.
Harpetida is one of the nine orders of the extinct arthropod class Trilobita. The first harpetid trilobites appear in the Upper Cambrian, and the last species die out at the end of the Devonian period.
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.
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.
Cromus is a genus of phacopid trilobites in the family Encrinuridae, that existed during the upper Silurian in what is now the Czech Republic. The genus was described by Barrande in 1852, and the type species is C. intercostatus. It also contains the species C. canorus.
Deacybele is a genus of trilobites in the order Phacopida, that existed during the upper Ordovician in what is now Ireland. It was described by Whittington in 1965, and the type species is Deacybele arenosa, which was originally described under the genus Calymene by McCoy in 1846. The type locality was the Avoca Formation.
Denckmannites is a trilobite in the order Phacopida, that existed during the upper Silurian in what is now the Czech Republic. It was described by Wedekind in 1914, and the type species is Denckmannites volborthi, which was originally described under the genus Phacops by Barrande in 1852. It also contains the species Denckmannites morator, and Denckmannites primaevus. The type locality was the Kopanina Formation.
Didrepanon is a trilobite in the order Phacopida, that existed during the upper Silurian in what is now England. It was described by Lane in 1971, and the type species is Didrepanon falcatum. The type locality was in Sedgley.
Duftonia is a trilobite in the order Phacopida, that existed during the upper Ordovician in what is now England. It was described by Dean in 1959, and the type species is Duftonia lacunosa. The type locality was the Dufton Shale Formation, from which the generic name was derived.
Emsurina is a genus of trilobites in the order Phacopida, that existed during the upper Cambrian in what is now Russia. It was described by Sivov in 1955, and the type species is Emsurina sibirica. The type locality was the Tolstochikhin Formation in Salair.
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.
Erratencrinurus is a genus of trilobites in the order Phacopida, that existed during the upper Ordovician in what is now northern Germany. It was described from glacial erratics by Krueger in 1972, and the type species is Erratencrinurus capricornu.
Frencrinuroides is a genus of trilobites in the order Phacopida, that existed during the upper Ordovician in what is now the United States. It was described by Lesperance and Desbiens in 1995, and the type species is Frencrinuroides capitonis, which was originally described under the genus Encrinuroides by Frederickson in 1964. The type locality was the Bromide Formation in Oklahoma.
Heliomeroides is a trilobite in the order Phacopida, that existed during the upper Ordovician in what is now the United States. It was described by Evitt in 1951, and the type species is Heliomeroides teres. The type locality was the Lincolnshire Formation in Virginia.
Isalaux is a trilobite in the order Phacopida, that existed during the upper Ordovician in what is now the United States. It was described by Frederickson and Pollack in 1952, and the type species is Isalaux canonensis. The type locality was the Harding Formation in Colorado.
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".
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.
