| Neophlyctaenius Temporal range: Late Devonian | |
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| Genus: | Neophlyctaenius |
| Species: | N. sherwoodi |
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| Neophlyctaenius sherwoodi Denison, 1950 | |
Neophlyctaenius is an extinct genus of placoderm fish, which lived during the Late Devonian period of North America. [1]
Gnathostomata are the jawed vertebrates. The term derives from Greek: γνάθος "jaw" + στόμα "mouth". Gnathostome diversity comprises roughly 60,000 species, which accounts for 99% of all living vertebrates. In addition to opposing jaws, living gnathostomes have teeth, paired appendages, and a horizontal semicircular canal of the inner ear, along with physiological and cellular anatomical characters such as the myelin sheaths of neurons. Another is an adaptive immune system that uses V(D)J recombination to create antigen recognition sites, rather than using genetic recombination in the variable lymphocyte receptor gene.
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. Placoderms are paraphyletic, and consist of several distinct outgroups or sister taxa to all living jawed vertebrates, which originated among their ranks. This is illustrated by a 419-million-year-old fossil, Entelognathus, from China, which is the only known placoderm with a type of bony jaw like that found in modern bony fishes. This includes a dentary bone, which is found in humans and other tetrapods. The jaws in other placoderms were simplified and consisted of a single bone. Placoderms were also the first fish to develop pelvic fins, the precursor to hindlimbs in tetrapods, as well as true teeth. Paraphyletic groupings are problematic, as one can not talk precisely about their phylogenic relationships, their characteristic traits and literal extinction. 380-million-year-old fossils of three other genera, Incisoscutum, Materpiscis and Austroptyctodus, represent the oldest known examples of live birth.
Dunkleosteus is an extinct genus of arthrodire placoderm fish that existed during the Late Devonian period, about 358–382 million years ago. The name Dunkleosteus combines the Greek ὀστέον, osteon, meaning "bone", and Dunkle, in honor of David Dunkle of the Cleveland Museum of Natural History. It consists of ten species: D. terrelli, D. belgicus, D. denisoni, D. marsaisi, D. magnificus, D. missouriensis, D. newberryi, D. amblyodoratus, and D. raveri; some of which are among the largest placoderms to have ever lived. The largest species, D. terrelli grew up to 8.79 m (28.8 ft) long and 4 t in weight. Dunkleosteus could quickly open and close its jaw, like modern day suction feeders, and had a bite force of 6,000 N at the tip and 7,400 N at the blade edge. Numerous fossils of the various species have been found in North America, Poland, Belgium, and Morocco.
Ctenurella is an extinct genus of ptyctodont placoderm from the Late Devonian of Germany. The first fossils were found in the Strundevalley in the Paffrather Kalkmulde.
Arthrodira is an order of extinct armoured, jawed fishes of the class Placodermi that flourished in the Devonian period before their sudden extinction, surviving for about 50 million years and penetrating most marine ecological niches.
Rhenanida is an order of scaly placoderms. Unlike most other placoderms, the rhenanids' armor was made up of a mosaic of unfused scales and tubercles. The patterns and components of this "mosaic" correspond to the plates of armor in other, more advanced placoderms, suggesting that the ancestral placoderm had armor made of unfused components, as well.
The ptyctodontids ("folded-teeth") are placoderms of the order Ptyctodontida, containing the family Ptyctodontidae. With their big heads, big eyes, reduced armor and long bodies, the ptyctodontids bore a superficial resemblance to modern day chimaeras (Holocephali). Their armor was reduced to a pattern of small plates around the head and neck. Like the extinct and related acanthothoracids, and the living and unrelated holocephalians, most of the ptyctodontids are thought to have lived near the sea bottom and preyed on shellfish.
Brindabellaspis stensioi is a flat-snouted placoderm with a platypus-like snout from the Early Devonian of the Taemas-Wee Jasper reef in Australia. When it was first discovered in 1980, it was originally regarded as a Weejasperaspid acanthothoracid due to anatomical similarities with the other species found at the reef.
Campbellodus decipiens is an extinct ptyctodontid placoderm fish that lived around 380 million years ago. Its fossil remains have been found preserved in perfect three-dimensional form from the Gogo Formation of Western Australia. Originally it was described from large tooth plates and isolated skull roof bones by Miles & Young (1977). Long (1995) restored the complete fish based on new material found at Gogo in the mid 1980s, and described by Long (1997).
Phyllolepis is the type genus of Phyllolepida, an extinct taxon of arthrodire placoderm fish from the middle to late Devonian. The species of Phyllolepis, themselves, are restricted to the Famennian-aged freshwater strata of the Late Devonian, around 360 million years ago. Fossils of this genus have been found primarily in Europe and North America. The end of the Devonian saw them disappear in a mass extinction.
Arctolepis is an extinct genus of placoderm fish, which lived during the Early Devonian period. Fossils of Arctolepis have been found in what is now Norway and Michigan.
Huginaspis is an extinct genus of placoderm fish, which lived during the Middle Devonian period of Spitsbergen, Norway.
Austrophyllolepis is an extinct genus of phyllolepid arthrodire placoderm from Middle to Late Devonian freshwater strata of Australia. The type species, A. ritchiei is found in Givetian to early Frasnian-aged freshwater strata near what is now Mount Howitt. A second species, A. dulciensis, is found from Middle Devonian freshwater strata from the Dulcie Sandstone of Georgina Basin, Central Australia.
Turrisaspis elektor is an extinct species of groenlandaspid arthrodire placoderm . It is known only from trunk fragments from the Catskill Formation from the Upper Devonian of Clinton County, Pennsylvania .
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.
Austroptyctodus gardineri is a small ptyctodontid placoderm fish from the Upper Devonian Gogo Formation of Western Australia. First described by Miles & Young (1977) as a new species of the German genus Ctenurella. Long (1997) redescribed the German material and found major differences in the skull roof pattern so assigned it to a new genus, Austroptyctodus. This genus lacks spinal plates and has Ptyctodus-like toothplates.
Fallacosteus turneri is an extinct species of arthrodire placoderm from the late Devonian of the Gogo Formation of Western Australia. As with almost all other camuropiscids, F. turnerae had an elongated snout that may have enhanced its hydrodynamic streamlining.
Walterosteus is a genus of small selenosteid arthrodire placoderms known from the Upper Frasnian Kellwasserkalk facies of Late Devonian Germany and Morocco.
Microbrachius is an extinct genus of tiny, advanced antiarch placoderms closely related to the bothriolepids. Complete articulated specimens show that the armored section of the body had an average length of 2-4 cm. Species of Microbrachius are characterized by having large heads with short thoracic armor. Specimens of Microbrachius have been found in Scotland, Belarus, Estonia, and China. Specimens range in age from the Lower Devonian Late Emsian Stage to the Middle Devonian Upper Givetian Stage.
Cowralepis is an extinct genus of phyllolepid placoderm of Givetian Cowra, New South Wales, and several juveniles of various stages of growth have also been discovered.
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