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Ptyctodontida
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. On account of their radically reduced armor, some paleontologists have suggested that the Ptyctodontida were not actually placoderms, but actual holocephalians, some primitive group of elasmobranch fish, or even were the ancestors of the holocephalians, including the chimaeras. Thorough anatomical examinations of whole fossil specimens reveal that the profound similarities between these two groups are actually very superficial. The major differences ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Placoderm
Placoderms (from Ancient Greek πλάξ [''plax'', ''plakos''] 'Plate (animal anatomy), plate' and δέρμα [''derma''] 'skin') are vertebrate animals of the class (biology), class Placodermi, an extinct group of prehistoric fish known from Paleozoic fossils during the Silurian and the Devonian geological period, periods. While their endoskeletons are mainly cartilaginous, their head and thorax were covered by articulated armour (zoology), armoured plates (hence the name), and the rest of the body was scale (zoology), scaled or naked depending on the species. Placoderms were among the first jawed fish (their fish jaw, jaws likely Evolution, evolved from the first pair of gill arches), as well as the first vertebrates to have true tooth, teeth. They were also the first fish clade to develop pelvic fins, the second set of paired fins and the homology (biology), homologous precursor to hindlimbs in tetrapods. 380-million-year-old fossils of three other genera, ''Incisoscutum'', ''M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhynchodus
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. On account of their radically reduced armor, some paleontologists have suggested that the Ptyctodontida were not actually placoderms, but actual holocephalians, some primitive group of elasmobranch fish, or even were the ancestors of the holocephalians, including the chimaeras. Thorough anatomical examinations of whole fossil specimens reveal that the profound similarities between these two groups are actually very superficial. The major differences b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ptyctodus
''Ptyctodus'' is an extinct armour-plated fish of the late Devonian. ''Ptyctodus'' belongs to the family Ptyctodontidae and is of the class Placodermi. They share a close resemblance to modern day chimaeras (Holocephali). Fossils of this armour-plated fish have been found in locations such as in Russia, the Michigan Basis, and Arizona, United States. Description and paleobiology ''Ptyctodus'' species come in a variety of different sizes, measured data shows three specimens being 94 millimeters, 24 millimeters, 22 millimeters in length, 23 millimeters, 6 millimeters, 4 millimeter in height, and 18 millimeters, 7 millimeters, and 4 millimeters in thickness. Through time, an evolutionary morphological trait is that the species within Ptyctodontidae reduce the dermal armour. The dentition of the ''Ptyctodus'' has dental elements that are very similarly observed in ''chimaeroids''. Its dental plates are compressed into a thin cutting edge behind the symphysis and measure 3 inches ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holocephali
Holocephali (Sometimes spelled Holocephala; Romanization of Greek, Greek for "complete head" in reference to the fusion of Palatoquadrate, upper jaw with the rest of the skull) is a Subclass (biology), subclass of Chondrichthyes, cartilaginous fish. While the only living holocephalans are three families within a single Order (biology), order which together are commonly known as chimaeras, the group includes many extinct orders and was far more diverse during the Paleozoic and Mesozoic Era (geology), eras. The earliest known fossils of holocephalans date to the Middle Devonian period, and the group likely reached its peak diversity during the following Carboniferous period. Molecular clock studies suggest that the subclass diverged from its closest relatives, Elasmobranchii, elasmobranchs such as sharks and Batomorphi, rays, during the Early Devonian or Silurian period. Extinct holocephalans are typically divided into a number of orders, although the interrelationships of these gro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Palaeomylus
''Palaeomylus'' (meaning 'ancient grinder') is an extinct Devonian ptychodontid placoderm fish. There are seven species accepted in this genus: Etymology The generic name is derived from Greek (''Palaeo'', meaning "ancient") and (''mylos'', meaning "grinder"). Not to be confused with the junior homonym ''Palaeomylus'' , which is an early diverging member of the mammal group Glires. Discovery ''P. greenei'', ''P. crassus'', and the type species ''P. frangens'' were originally classified as a species of ''Rhynchodus'', before being moved to a new genus, ''Palaeomylus'', in 1891. The first was found in Wisconsin, while the latter two species were found in Ohio. ''P. predator'' was found near Gerolstein Gerolstein () is a town in the Vulkaneifel district of Rhineland-Palatinate, Germany. Gerolstein is a local municipality of the ''Verbandsgemeinde Gerolstein''. It has been approved as a ''Luftkurort'' (spa town). History As early as the Stone ..., Germany. References ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acanthothoracids
Acanthothoraci (''spine chests'') is an extinct group of chimaera-like placoderms closely related to the rhenanid placoderms. Superficially, the acanthoracids resembled scaly chimaeras and (relatively) heavily armored ptyctodonts. They were distinguished from chimaeras by their large scales and plates, a pair of large spines that emanate from their chests (thus, the order's name), tooth-like beak plates, and the typical bone-enhanced placoderm eyeball. They were distinguished from other placoderms by differences in skull anatomy and by patterns on the skull plates and thoracic plates that are unique to this order. Fossil record Fossils of the acanthothoracids are found in various deposits from the Lower Devonian throughout the world. Fossils of the Palaeacanthaspids are found in Eurasia and Canada, while the Weejasperaspids have only been found in the Taemas Wee Jasper reef, in Southeastern Australia. Ecology From what can be inferred from the mouthplates of fossil specim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eczematolepis
''Eczematolepis'' is an extinct genus of ptyctodontidan from the Milwaukee Formation of Wisconsin Wisconsin ( ) is a U.S. state, state in the Great Lakes region, Great Lakes region of the Upper Midwest of the United States. It borders Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michig .... Three species are known: ''E. fragilis'', ''E. pustulosus'' and ''E. telleri''.''Eastman, C. R.'' 1898 B, p. 55, fig. 49. 1899 B, p. 283. It was originally classified as the genus ''Acantholepis'' but that name was preoccupied. References Ptyctodontids Givetian extinctions Placoderm genera Fossil taxa described in 1892 {{Placoderm-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kimbryanodus
''Kimbryanodus'' is a genus of extinct ptyctodontid placoderm fish from the Frasnian of Australia.These placoderms can be told apart from others due to the large eyes, crushing tooth plates, long bodies, reduced armor, and a superficial resemblance to holocephalid fish. The group is so far the only Placoderms known with sexually dimorphic features. The fossils occur as small three dimensional isolated plates. Because of these new specimens the Ptyctodontid grouping got a taxonomic classification, it found that the genus ''Rhamphodopsis'' to be the most basal taxa In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and .... They are divided by having the more basal taxa having a median dorsal spine, a simple spinal plate, and a simple V-shaped overlap of the anterior lateral and the anter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhamphodopsis
''Rhamphodopsis'' is a genus of extinct ptyctodont placoderm from the Middle Devonian Old Red Sandstone of Scotland Scotland is a Countries of the United Kingdom, country that is part of the United Kingdom. It contains nearly one-third of the United Kingdom's land area, consisting of the northern part of the island of Great Britain and more than 790 adjac .... Species There are two species of ''Rhamphodopsis'' recognized. ''R. thrieplandi'' This is the type species, and the smaller of the two described species, the adult total length being up to 7 centimeters. The median dorsal spine is shorter than the anterior lateral spines. ''R. trispinatus'' This is a much larger, more robust species, the adult total length being up to 12 centimeters. The main way to distinguish small individuals of ''R. trispinatus'' from individuals of ''R. thrieplandi'' is that the median dorsal and anterior lateral spines of ''R. trispinatus'' are both proportionally equal lengths and are propo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
