Placodermi is a class of armoured prehistoric fish, known from fossils, which lived from the Silurian to the end of the Devonian period. Their head and thorax were covered by articulated armoured plates and the rest of the body was scaled or naked, depending on the species. Placoderms were among the first jawed fish; their jaws likely evolved from the first of their gill arches.
Dunkleosteus is an extinct genus of large arthrodire ("jointed-neck") fish that existed during the Late Devonian period, about 382–358 million years ago. It was a pelagic fish inhabiting open waters, and one of the first apex predators of any ecosystem.
Groenlandaspis is an extinct genus of arthrodire from the Late Devonian. Fossils of the different species are found in late Devonian strata in all continents except eastern Asia. The generic name commemorates the fact that the first specimens of the type species were found in Greenland.
The Emsian is one of three faunal stages in the Early Devonian Epoch. It lasted from 407.6 ± 2.6 million years ago to 393.3 ± 1.2 million years ago. It was preceded by the Pragian Stage and followed by the Eifelian Stage. It is named after the Ems river in Germany. The GSSP is located in the Zinzil'ban Gorge in the Kitab State Geological Reserve of Uzbekistan, 35 centimetres (14 in) above the contact with the Madmon Formation.
Titanichthys is an extinct genus of giant, aberrant marine placoderm from shallow seas of the Late Devonian of Morocco, Eastern North America, and possibly Europe. Many of the species approached Dunkleosteus in size and build. Unlike its relative, however, the various species of Titanichthys had small, ineffective-looking mouth-plates that lacked a sharp cutting edge. It is assumed that Titanichthys was a filter feeder that used its capacious mouth to swallow or inhale schools of small, anchovy-like fish, or possibly krill-like zooplankton, and that the mouth-plates retained the prey while allowing the water to escape as it closed its mouth. A study has since confirmed this assumption as its jaws are functionally closer to that of filter feeders like baleen whales and basking sharks, and it appears to have developed from benthic durophagists that became pelagic suspension feeders. This would make it the first (known) large-sized vertebrate filter feeder. Titanichthys was estimated to have reached a length of 7–7.6 m (23–25 ft), but Engelman (2023) suggested that Titanichthys was comparable in size to Dunkleosteus, likely measuring about or just over 4.1 metres (13.5 ft) in length.
Chotecops is a genus of trilobites from the order Phacopida, suborder Phacopina, family Phacopidae. It was initially erected as a subgenus of Phacops but some later authors thought it distinctive enough to raise its status. Species assigned to this genus occur between the Emsian and the Famennian. Chotecops is the most abundant trilobite in the Hunsrück Slate and due to the excellent preservation, often soft tissue such as antennae and legs have been preserved as a thin sheet of pyrite.
Dunkleosteidae is an extinct family of arthrodire placoderms that lived during the Devonian period. The gigantic apex predator Dunkleosteus terrelli is the best known member of this group.
Holonema is an extinct genus of relatively large, barrel-shaped arthrodire placoderms that were found in oceans throughout the world from the Mid to Late Devonian, when the last species perished in the Frasnian-Fammian extinction event. Most species of the genus are known from fragments of their armor, but the Gogo Reef species, H. westolli, is known from whole, articulated specimens.
Eastmanosteus is a fossil genus of dunkleosteid placoderms. It was closely related to the giant Dunkleosteus, but differed from that genus in size, in possessing a distinctive tuberculated bone ornament, a differently shaped nuchal plate and a more zig-zagging course of the sutures of the skull roof.
Incisoscutum is an extinct genus of arthrodire placoderm from the Early Frasnian Gogo Reef, from Late Devonian Australia. The genus contains two species I. ritchiei, named after Alex Ritchie, a palaeoichthyologist and senior fellow of the Australian Museum, and I. sarahae, named after Sarah Long, daughter of its discoverer and describer, John A. Long.
Homostiidae is a family of flattened arthrodire placoderms from the Early to Middle Devonian. Fossils appear in various strata in Europe, Russia, Morocco, Australia, Canada and Greenland.
Heterosteidae is an extinct family of moderately large to giant, flattened, benthic arthrodire placoderms with distinctive, flattened, triangular skulls that are extremely broad posteriorly, but become very narrow anteriorly.
Angarichthys hyperboreus is an extinct homostiid arthrodire placoderm from the Middle Devonian of Siberia. It is known from an infragnathal plate, an intero-lateral plate, and a marginal plate found from the Middle Devonian strata of the Tynep Series formation, in the Bakhta River basin, Tunguska Plateau. A. hyperboreus differs from Homosteus in that the former's marginal plate has a ridge where the central plate would have overlapped it, and in the infragnathal, which is curved sigmoidally, and bears at least seven tooth-like prongs nearer to the functional anterior end.
Microbrachius is an extinct genus of tiny, advanced antiarch placoderms closely related to the bothriolepids. Specimens range in age from the Lower Devonian Late Emsian Stage to the Middle Devonian Upper Givetian Stage. They are characterized by having large heads with short thoracic armor of an average length of 2–4 cm. There are patterns of small, but noticeable tubercles on the armor, with the arrangement varying from species to species. Specimens of Microbrachius have been found in Scotland, Belarus, Estonia, and China.
Qilinyu is a genus of early placoderm from the late Silurian of China. It contains a single species, Qilinyu rostrata, from the Xiaoxiang fauna of the Kuanti Formation. Along with its contemporary Entelognathus, Qilinyu is an unusual placoderm showing some traits more similar to bony fish, such as dermal jaw bones and lobe-like fins. It can be characterized by adaptations for a benthic lifestyle, with the mouth and nostrils on the underside of the head, similar to the unrelated antiarch placoderms. The shape of the skull has been described as "dolphin-like", with a domed cranium and a short projecting rostrum.
Kujdanowiaspis is an extinct genus of arthrodire placoderm fish from the Early Devonian of Podolia (Ukraine), Poland and Spain. Kujdanowiaspis is known from many fragmentary head shields and body armours.
Tityosteus is an extinct genus of homostiid arthrodire from the Early Emsian of the Early Devonian, with fossils known from Germany, the Ibero-Armorican Trough, and southern Siberia. It attained a length of 2.5 meters.
Atlantidosteus is an extinct genus of homostiid arthrodire from the Early to Middle Devonian of Morocco and Queensland. It contains two known species, A. hollardi and A. pacifica.
Cavanosteus is an extinct genus of homostiid arthrodire from the Emsian of Victoria, and New South Wales, Australia.
Cathlesichthys is an extinct genus of homostiid arthrodire from Wee Jasper, during the Early Devonian.
