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Dinichthys herzeri is an extinct, giant, marine arthrodire placoderm from the Late Devonian (Famennian stage) of Ohio and Tennessee. It was comparable in size, shape, and ecological role to the better-known Dunkleosteus. Originally described in 1868 by John Newberry on the basis of an incomplete skull roof and mandibles (AMNH 81), this species remains imperfectly known to this day.
For much of the 20th century, many unrelated large arthrodires were classified together within this genus, including species now assigned to Dunkleosteus, Eastmanosteus, and Titanichthys. Today, Dinichthys is considered a monotypic genus, containing only the type species, D. herzeri. Similarly, in a 2010 analysis, the family Dinichthyidae that once held a wide range of arthrodire genera was redefined as comprising only Dinichthys.
The type species of Dunkleosteus was originally described as Dinichthys terrelli by Newberry in 1873. After complete exoskeletons of this species were discovered in the early 20th century Din. terrelli served as the basis for life reconstructions of the genus as opposed to the fragmentary Din. herzeri, even long after terrelli was separated into Dunkleosteus by Jean Pierre Lehman in 1956. As a result, most illustrations captioned as Dinichthys are actually pictures of Dunkleosteus.
Its relative, Titanichthys, may have rivaled it in size.
These particular animals may have reached lengths of 10 m (33 ft) and are estimated to have weighed in at 3.6 tonnes. Titanichthys is a genus of giant, aberrant marine placoderm from shallow seas the Late Devonian of Morocco and Eastern North America. Many of the species approached Dunkleosteus in size and build. Unlike its relative, however, the various species of Titanichys 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.
Heterosteus
Heterosteus is an extinct genus of heterosteid placoderm known from remains discovered in Europe and Greenland.
This genus includes the largest species in the family, and are among the largest arthrodires, as well, with the type species, H. asmussi, having an estimated body length of up to 6 metres (19 ft 8 in).The genus differs from Herasmius by having the orbits on slightly longer eyes talk-like projections. The various species are found in Givetian-aged deposits in Europe and Greenland. With the except of the German H. rhenanus, all species are known from freshwater deposits: H. rhenanus is based on fragments found in a marine deposit.
Homosteus
Homosteus is a genus of flattened arthrodire placoderm from the Middle Devonian. Fossils are found primarily in Eifelian-epoch aged strata of Europe, Canada, Greenland, and Estonia.All of the species had comparatively large, flattened heads with, as suggested by the upward opening orbits, upward-pointing eyes.These adaptations suggest that the various species were benthic predators.
The headshield of H. latus is about one meter long.
Holonema
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 the armor, but the Gogo Reef species, H. westolli, is known from whole, articulated specimens. According to these specimens, species of Holonema lived by grazing on stony, horn-shaped, stromatolite-like algae called oncholite, apparently by snipping off the points with a specialized snout.
A large species from Givetian-aged strata in Novaya Zemlya, Russia, known only from two plates from one individual"s trunk shield has reached up to 5 m in length.
Plourdosteus
Plourdosteus is an extinct genus of placoderm, which was relatively widespread in Euramerica during the Givetian to Frasnian ages of the Devonian.The name Plourdosteus commemorates the Plourde family at Miguasha.
They are characterized by bone shell that covers the head and the front of the body.Length up to 6 meters.
Antineosteus
Antineosteus rufus from the upper Emsian of the Czech Republic is described based on two fragments of large dermal plates discovered in the Suchomasty Limestone. The original length of the animal is inferred to have exceeded that of Tityosteus rieversae - the largest Lower Devonian placoderm recorded so far. The occurrence of A. rufus in the Prague Basin is consistent with other giant homostiids in several areas. These animals were apparently adapted to plankton- feeding, although they appeared in the conditions of collapsed diversity of the planktic communities during the “Devonian Nekton Revolution”. This successful feeding strategy made them the first vertebrates occupying the nutrient-rich ecospace producing the largest animals up to the present.
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