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Orodontiformes
Orodontiformes is an extinct group of cartilaginous fish, known from the Late Devonian and Carboniferous periods. They are part of Euchondrocephali (Holocephali ''sensu lato''), making their closest living relatives chimaeras. Most members are only known from teeth, which are low and rounded, and designed for crushing prey (durophagy). The group in its totality has been described as "undoubtedly artificial" (i.e. non-monophyletic).Ginter, M., Hampe, O., and Duffin, C.J., 2010, Chondrichthyes. Paleozoic Elasmobranchii: teeth, in Schultze, H.-P., ed., Handbook of Paleoichthyology, v. 3D: München, Friedrich Pfeil, pp. 109-117 Several species of '' Orodus'' are known from specimens preserving the body as well as the teeth. Description According to Ginter et al 2010, the teeth of Orodontiformes are distinguished by the following features: The only known members of the Orodontiformes known from skeletal material are two species of '' Orodus'', ''Orodus greggi'' ''and Orodus micropte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Euchondrocephali
Holocephali (Sometimes spelled Holocephala; Greek for "complete head" in reference to the fusion of upper jaw with the rest of the skull) is a subclass of cartilaginous fish. While the only living holocephalans are three families within a single order which together are commonly known as chimaeras, the group includes many extinct orders and was far more diverse during the Paleozoic and Mesozoic 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, elasmobranchs such as sharks and rays, during the Early Devonian or Silurian period. Extinct holocephalans are typically divided into a number of orders, although the interrelationships of these groups are poorly understood. Several different definitions of Holocephali exist, with the group sometimes considered a less inclusiv ... [...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] |
Cartilaginous Fish
Chondrichthyes (; ) is a class of jawed fish that contains the cartilaginous fish or chondrichthyans, which all have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fish'', which have skeletons primarily composed of bone tissue. Chondrichthyes are aquatic vertebrates with paired fins, paired nares, placoid scales, conus arteriosus in the heart, and a lack of opercula and swim bladders. Within the infraphylum Gnathostomata, cartilaginous fishes are distinct from all other jawed vertebrates. The class is divided into two subclasses: Elasmobranchii (sharks, rays, skates and sawfish) and Holocephali ( chimaeras, sometimes called ghost sharks, which are sometimes separated into their own class). Extant chondrichthyans range in size from the finless sleeper ray to the over whale shark. Anatomy Skeleton The skeleton is cartilaginous. The notochord is gradually replaced by a vertebral column during development, e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orodus
''Orodus'' (from , 'beautiful' and 'tooth') is an extinct genus of orodontiform cartilaginous fish. Fossils are known from the late Devonian to Late Carboniferous of Europe, Asia and North America. Most species are only known from their rounded, ridge covered teeth, designed for crushing prey (durophagy). The genus has a long and complicated taxonomic history, and numerous species have been assigned to the genus that are now either considered invalid or unrelated to true orodontids. Two species, ''O. greggi'' and ''O. micropterygius'' from the Carboniferous of North America are known from remains preserving the body.Ginter, M., Hampe, O., and Duffin, C.J., 2010, Chondrichthyes. Paleozoic Elasmobranchii: teeth, in Schultze, H.-P., ed., Handbook of Paleoichthyology, v. 3D: München, Friedrich Pfeil, pp. 109-117 ''O. greggi'' reached around long, while ''O. micropterygius'' just reached . These remains show that these species of ''Orodus'' lacked fin spines on their dorsal fins ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Devonian
The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian period at million years ago (Megaannum, Ma), to the beginning of the succeeding Carboniferous period at Ma. It is the fourth period of both the Paleozoic and the Phanerozoic. It is named after Devon, South West England, where rocks from this period were first studied. The first significant evolutionary radiation of history of life#Colonization of land, life on land occurred during the Devonian, as free-spore, sporing land plants (pteridophytes) began to spread across dry land, forming extensive coal forests which covered the continents. By the middle of the Devonian, several groups of vascular plants had evolved leaf, leaves and true roots, and by the end of the period the first seed-bearing plants (Pteridospermatophyta, pteridospermatophyt ... [...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] |
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] |
Durophagy
Durophagy is the eating behavior of animals that consume Seashell, hard-shelled or exoskeleton-bearing organisms, such as corals, shelled mollusks, or crabs. It is mostly used to describe fish, but is also used when describing reptiles, including fossil turtles, placodonts and invertebrates, as well as Osteophagy, "bone-crushing" mammalian carnivores such as hyenas. Durophagy requires special adaptions, such as blunt, strong teeth and a heavy jaw. Bite force is necessary to overcome the physical constraints of consuming more durable prey and gain a competitive advantage over other organisms by gaining access to more diverse or exclusive food resources earlier in life. Those with greater bite forces require less time to consume certain prey items as a greater bite force can increase the net rate of energy intake when foraging and enhance fitness in durophagous species. In the order Carnivora there are two dietary categories of durophagy; bonecrackers and bamboo eaters. Bonecrackers ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monophyletic
In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent common ancestor (or more precisely an ancestral population), i.e. excludes non-descendants of that common ancestor # the grouping contains all the descendants of that common ancestor, without exception Monophyly is contrasted with paraphyly and polyphyly as shown in the second diagram. A ''paraphyletic'' grouping meets 1. but not 2., thus consisting of the descendants of a common ancestor, excepting one or more monophyletic subgroups. A '' polyphyletic'' grouping meets neither criterion, and instead serves to characterize convergent relationships of biological features rather than genetic relationships – for example, night-active primates, fruit trees, or aquatic insects. As such, these characteristic features of a polyphyletic grouping ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heterodont
In anatomy, a heterodont (from Greek, meaning 'different teeth') is an animal which possesses more than a single tooth morphology. Human dentition is heterodont and diphyodont as an example. In vertebrates, heterodont pertains to animals where teeth are differentiated into different forms. For example, members of the Synapsida generally possess incisors, canines ("dogteeth"), premolars, and molars. The presence of heterodont dentition is evidence of some degree of feeding and or hunting specialization in a species. In contrast, homodont or isodont dentition refers to a set of teeth that possess the same tooth morphology. In invertebrates, the term heterodont refers to a condition where teeth of differing sizes occur in the hinge plate, a part of the Bivalvia Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
