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Orthacanthus
''Orthacanthus'' is an extinct genus of fresh-water xenacanthiform cartilaginous fish, named by Louis Agassiz in 1843, ranging from the Upper Carboniferous into the Lower Permian. ''Orthacanthus'' had a nektobenthic life habitat, with a carnivorous diet. Multiple authors have also discovered evidence of cannibalism in the diet of ''Orthacanthus'' and of "filial cannibalism" where adult ''Orthacanthus'' preyed upon juvenile ''Orthacanthus.'' Synonyms of the genus ''Orthacanthus'' are ''Dittodus'' Owen, 1867, ''Didymodus'' Cope, 1883, ''Diplodus'' Agassiz, 1843, ''Chilodus'' Giebel, 1848 (preoccupied by ''Chilodus'' Müller & Troschel, 1844). During the Late Carboniferous-Early Permian, ''Orthacanthus'' was an apex predator of freshwater swamps and bayous in Europe and North America. Mature ''Orthacanthus'' reached nearly 3 meters (10 feet) in length. ''Orthacanthus'' teeth have a minimum of three cusps, two principal cusps, and an intermediate cusp, where the principal cusps are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orthacanthus Scale
''Orthacanthus'' is an extinct genus of fresh-water Xenacanthida, xenacanthiform cartilaginous fish, named by Louis Agassiz in 1843, ranging from the Upper Carboniferous into the Lower Permian. ''Orthacanthus'' had a nektobenthic life habitat, with a Carnivore, carnivorous diet. Multiple authors have also discovered evidence of cannibalism in the diet of ''Orthacanthus'' and of "filial cannibalism" where adult ''Orthacanthus'' preyed upon juvenile ''Orthacanthus.'' Synonyms of the genus ''Orthacanthus'' are ''Dittodus'' Owen, 1867, ''Didymodus'' Cope, 1883, ''Diplodus'' Agassiz, 1843, ''Chilodus'' Giebel, 1848 (preoccupied by ''Chilodus'' Müller & Troschel, 1844). During the Late Carboniferous-Early Permian, ''Orthacanthus'' was an apex predator of freshwater swamps and bayous in Europe and North America. Mature ''Orthacanthus'' reached nearly 3 meters (10 feet) in length. ''Orthacanthus'' teeth have a minimum of three cusps, two principal cusps, and an intermediate cusp, where t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xenacanthida
Xenacanthida (or Xenacanthiformes) is an order or superorder of extinct shark-like chondrichthyans (cartilaginous fish) known from the Carboniferous to Triassic. They were native to freshwater, marginal marine and shallow marine habitats. Some xenacanths may have grown to lengths of . Most xenacanths died out at the end of the Permian in the End-Permian Mass Extinction, with only a few forms surviving into the Triassic. Description The foundation of the tooth is prolonged lingually with a circlet button and a basal tubercle on the oral and aboral surfaces individually. The family Xenacanthidae consists of five genera: ''Xenacanthus'', '' Triodus'', '' Plicatodus'', '' Mooreodontus'' and '' Wurdigneria''; all of these are distinguished by cross sections of the points, crown center, length of the median edge, type of vertical cristae, and microscopic anatomy. Xenacanths are divided into two groups based on dental characteristics. Group one has tricuspid crowns containing two sto ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carboniferous
The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the Permian Period, Ma. It is the fifth and penultimate period of the Paleozoic era and the fifth period of the Phanerozoic eon (geology), eon. In North America, the Carboniferous is often treated as two separate geological periods, the earlier Mississippian (geology), Mississippian and the later Pennsylvanian (geology), Pennsylvanian. The name ''Carboniferous'' means "coal-bearing", from the Latin ("coal") and ("bear, carry"), and refers to the many coal beds formed globally during that time. The first of the modern "system" names, it was coined by geologists William Conybeare (geologist), William Conybeare and William Phillips (geologist), William Phillips in 1822, based on a study of the British rock succession. Carboniferous is the per ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enamel Pearl
Enamel pearls are developmental variations of teeth that present as beads or nodules of enamel in places where they are not normally observed ( ectopic enamel). Appearance and Location Enamel pearls most commonly present as spheroid in shape, but can also be conical, cylindrical, oval, teardrop, and irregularly shaped. They vary in size with an average diameter of 1.7mm. Enamel pearls are most frequently found in the root furcation of molars, and are not commonly seen in teeth with a single root, such as incisors and canines. Mechanisms of Formation Several theories of enamel pearl development exist, although no definitive mechanism has been established. Enamel pearls are composed primarily of enamel, but most also have a core of dentin within them. The most widely accepted theory suggests enamel pearls are formed from remnants of Hertwig’s epithelial root sheath (HERS), which adhere to the tooth surface after root development. During normal tooth development, after d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phoebodus
''Phoebodus'' is an extinct genus of phoebodontiform total group elasmobranch, known from over a dozen species found worldwide spanning the middle to late Devonian, making it one of the oldest known total group elasmobranchs. Most species are only known from their isolated tricuspid teeth, but one species, ''Phoebodus saidselachus'' from the Late Devonian of Morocco, is known from a complete skeleton, estimated to have been in total length in life, which shows that it had a slender body superficially similar to that of the living frilled shark. The teeth of ''Phoebodus'' and frilled sharks are also morphologically similar, and are designed for grasping prey. ''Phoebodus'' probably consumed small prey items that were capable of being swallowed whole. Species After Ivanov, 2021 * ''Phoebodus sophiae'' St. John & Worthen, 1875 (type). Australia, Iran, Mauritania, Poland, Spain, Portugal, United States (Indiana, Iowa, New York), Russia (Siberia). Middle Devonian (Givetian) * ''Pho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phoebodontiformes
Phoebodontiformes is an extinct group of elasmobranchs (''sensu lato''), known from the Devonian and Carboniferous periods. It includes the genera '' Phoebodus'', '' Diademodus'' and ''Thrinacodus''. ''Phoebodus'' and ''Thrinacodus'' have slender, elongate bodies. Their teeth are tricuspate (bearing three cusps). Some studies have recovered the group as paraphyletic. '' Jalodus'' and other members of the family Jalodontidae, which range from the Devonian to the Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ..., were formerly included in this order, but have subsequently been assigned to their own order, the Jalodontiformes. References Prehistoric cartilaginous fish orders Devonian cartilaginous fish Carboniferous cartilaginous fish {{paleo-cartilag ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Elasmobranchii
Elasmobranchii () is a subclass of Chondrichthyes or cartilaginous fish, including modern sharks ( division Selachii), and batomorphs (division Batomorphi, including rays, skates, and sawfish). Members of this subclass are characterised by having five to seven pairs of gill slits opening individually to the exterior, rigid dorsal fins and small placoid scales on the skin. The teeth are in several series; the upper jaw is not fused to the cranium, and the lower jaw is articulated with the upper. The details of this jaw anatomy vary between species, and help distinguish the different elasmobranch clades. The pelvic fins in males are modified to create claspers for the transfer of sperm. There is no swim bladder; instead, these fish maintain buoyancy with large livers rich in oil. The definition of the clade is unclear with respect to fossil chondrichthyans. Some authors consider it as equivalent to Neoselachii (the crown group clade including modern sharks, rays, and all o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrolagus Alberti
The gulf chimaera (''Hydrolagus alberti'') is a species of cartilaginous fish in the family Chimaeridae found near Mexico, the United States, and possibly Suriname. Its natural habitat is open sea A sea is a large body of salt water. There are particular seas and the sea. The sea commonly refers to the ocean, the interconnected body of seawaters that spans most of Earth. Particular seas are either marginal seas, second-order section ...s. References Gulf chimaera Fish of the Gulf of Mexico Gulf chimaera Taxonomy articles created by Polbot {{holocephalan-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chimaeras
Chimaeras are Chondrichthyes, cartilaginous fish in the order (biology), order Chimaeriformes (), known informally as ghost sharks, rat fish (not to be confused with rattails), spookfish, or rabbit fish; the last two names are also applied to Barreleye, Opisthoproctidae and Rabbitfish, Siganidae, respectively. At one time a "diverse and abundant" group (based on the fossil record), their closest living relatives are sharks and ray (fish), rays, though their last common ancestor with them lived nearly 400 million years ago. Living species (aside from plough-nose chimaeras) are largely confined to deep water. Anatomy Chimaeras are soft-bodied, shark-like fish with bulky heads and long, tapered tails; measured from the tail, they can grow up to in length. Like other members of the class Chondrichthyes, chimaera skeletons are entirely cartilaginous, or composed of cartilage. Males use forehead denticles to grasp a female by a fin during copulation. The Branchial arch, gill arche ... [...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] |
Ontogeny
Ontogeny (also ontogenesis) is the origination and development of an organism (both physical and psychological, e.g., moral development), usually from the time of fertilization of the ovum, egg to adult. The term can also be used to refer to the study of the entirety of an organism's lifespan. Ontogeny is the developmental history of an organism within its own lifetime, as distinct from phylogeny, which refers to the evolutionary history of a species. Another way to think of ontogeny is that it is the process of an organism going through all of the developmental stages over its lifetime. The developmental history includes all the developmental events that occur during the existence of an organism, beginning with the changes in the egg at the time of fertilization and events from the time of birth or hatching and afterward (i.e., growth, remolding of body shape, development of secondary sexual characteristics, etc.). While developmental (i.e., ontogenetic) processes can influen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
