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.
Eldredgeops rana is a species of trilobite from the middle Devonian period. Their fossils are found chiefly in the northeastern United States, and southwestern Ontario.
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 Late Ordovician 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 ("volvation"), a biological defense mechanism that is widespread among smaller trilobites but further perfected in this genus.
Dalmanites is a genus of trilobite in the order Phacopida. They lived from the Late Ordovician to Middle Devonian.
Walliserops is a genus of spinose phacopid trilobite, of the family Acastidae, found in Lower to Middle Devonian age rocks from the Anti-Atlas Mountains of Morocco. All species of Walliserops possess a three-pronged "trident" that protrudes from the glabella. Walliserops is most closely related to the genus Comura.
Parahughmilleria is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of Parahughmilleria have been discovered in deposits of the Devonian and Silurian age in the United States, Canada, Russia, Germany, Luxembourg and Great Britain, and have been referred to several different species. The first fossils of Parahughmilleria, discovered in the Shawangunk Mountains in 1907, were initially assigned to Eurypterus. It would not be until 54 years later when Parahughmilleria would be described.
The Devonian Mahantango Formation is a mapped bedrock unit in Pennsylvania, West Virginia, and Maryland. It is named for the North branch of the Mahantango Creek in Perry and Juniata counties in Pennsylvania. It is a member of the Hamilton Group, along with the underlying the Marcellus Formation Shale. South of Tuscarora Mountain in south central Pennsylvania, the lower members of this unit were also mapped as the Montebello Formation. Details of the type section and of stratigraphic nomenclature for this unit as used by the U.S. Geological Survey are available on-line at the National Geologic Map Database.
Erbenochile is a genus of spinose phacopid trilobite, of the family Acastidae, found in Lower to Middle Devonian age rocks from Algeria and Morocco. Originally described from an isolated pygidium, the first complete articulated specimen of E. erbeni revealed the presence of extraordinarily tall eyes:
"Straight-sided towers of lenses... with [up to] 18 lenses in a vertical file"
Anchiopsis is a genus of trilobite in the order Phacopida, which existed in what is now New York, U.S.A. It was described by Delo in 1935, and the type species is Anchiopsis anchiops, which was originally described as Calymene anchiops by Green in 1832.
Tarijactinoides is a genus of trilobites in the order Phacopida, which existed in what is now Bolivia. It was described by Suárez Soruco in 1971, and the type species is Tarijactinoides jarcasensis.
Coronura is a trilobite in the order Phacopida, that existed during the Middle Devonian in what is now New York, U.S.A. It was described by Hall and Clarke in 1888, and the type species is Coronura aspectans, which was originally described under the genus Asaphus by Conrad in 1841. The species was described from the Onondaga Formation. Fossils of Coronura have also been found in Indiana, and in the Emsian to Givetian Floresta Formation, Altiplano Cundiboyacense, Colombia.
Dipleura is a genus of trilobites in the order Phacopida. It was described by Green in 1832, and the type species is Dipleura dekayi. The type locality was in the Hamilton Group in New York.
Cordania is an extinct genus of trilobites that lived from the Early to Middle Devonian.
The Milwaukee Formation is a fossil-bearing geological formation of Middle Devonian age in Milwaukee County, Wisconsin. It stands out for the exceptional diversity of its fossil biota. Included are many kinds of marine protists, invertebrates, and fishes, as well as early trees and giant fungi.
Viaphacops is a genus of trilobites in the order Phacopida, family Phacopidae, that lived during the Middle Devonian, and is known from North and South America, Asia.
The Floresta Formation is a geological formation of the Altiplano Cundiboyacense in the Eastern Ranges of the Colombian Andes. The sequence of siltstones, shales, coquinas and sandstone beds dates to the Devonian period; Late Emsian, Eifelian and Early Givetian epochs, and has a maximum thickness of 600 metres (2,000 ft). The unit is highly fossiliferous; brachiopods, bryozoans, gastropods, trilobites, corals and bivalves have been found in the Floresta Formation. Some fragments of Placoderm fish fossils were found in the Floresta Formation, while the overlying Cuche Formation is much richer in fish biodiversity.
The Cuche Formation is a geological formation of the Floresta Massif, Altiplano Cundiboyacense in the Eastern Ranges of the Colombian Andes. The sequence of siltstones, shales, and sandstone beds dates to the Late Devonian and Early Carboniferous periods, and has a maximum thickness of 900 metres (3,000 ft).
Hollardops is a genus of trilobite in the order Phacopida that lived during the Devonian. Their fossils are found in the upper Emsian of western Europe and in the lower Emsian to lowermost Eifelian of North Africa. The type species, Asteropyge mesocristata, was described from Algeria by Le Maître in 1952. The genus Hollardops was erected by Morzadec in 1997. In the same year, Lieberman & Kloc erected Modellops and Philipsmithiana but those genera are regarded as subjective synonyms of Hollardops. The 10-segmented thoracic condition of Hollardops is a rare feature among acastid trilobites that almost always have 11 thorax segments. Van Viersen & Kloc (2022) revisited Hollardops and described a number of new species from the Devonian of Morocco. They also regarded Pennarbedops Bignon & Crônier, 2013 as a synonym of Hollardops. Van Viersen & Kloc construed Hollardops as a scavenger or predator with well-developed eyes, that used its shovel-like cephalon to plough the top layers of the sediment in search of food. Hollardops had small pits horizontally along the fringe of the exoskeleton; these are believed to have housed setae that allowed the trilobite to closely monitor its surroundings.
The Windom shale or Windom member is a member of the Moscow formation in New York. It preserves fossils going back to the Givetian stage of the middle Devonian. The Windom shale is widely known for its high quality trilobite fossils.
Tolkienia is an extinct genus of trilobite in the family Acastidae. It consists of three species split from Comura based on morphological differences. The genus was present during the Emsian stage of the Early Devonian epoch around 400 Ma.
