|
Chondrichthyes
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] |
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] |
Holocephalimorpha
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 inclu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shark
Sharks are a group of elasmobranch cartilaginous fish characterized by a ribless endoskeleton, dermal denticles, five to seven gill slits on each side, and pectoral fins that are not fused to the head. Modern sharks are classified within the Division (taxonomy), division Selachii and are the sister group to the Batoidea, Batomorphi (Batoidea, rays and skate (fish), skates). Some sources extend the term "shark" as an informal category including Extinction, extinct members of Chondrichthyes (cartilaginous fish) with a shark-like morphology, such as hybodonts. Shark-like chondrichthyans such as ''Cladoselache'' and ''Doliodus'' first appeared in the Devonian Period (419–359 million years), though some fossilized chondrichthyan-like scales are as old as the Ordovician, Late Ordovician (458–444 million years ago). The earliest confirmed modern sharks (Selachii) are known from the Early Jurassic around , with the oldest known member being ''Agaleus'', though records of true shar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Batomorphi
Batomorphi is a division of cartilaginous fishes, commonly known as rays, this taxon is also known as the superorder Batoidea, but the 5th edition of ''Fishes of the World'' classifies it as the division Batomorphi. They and their close relatives, the sharks, compose the subclass Elasmobranchii. Rays are the largest group of cartilaginous fishes, with well over 600 species in 26 families. Rays are distinguished by their flattened bodies, enlarged pectoral fins that are fused to the head, and gill slits that are placed on their ventral surfaces. Anatomy Batomorphs are flat-bodied, and, like sharks, are cartilaginous fish, meaning they have a boneless skeleton made of a tough, elastic cartilage. Most batomorphs have five ventral slot-like body openings called gill slits that lead from the gills, but the Hexatrygonidae have six. Batomorph gill slits lie under the pectoral fins on the underside, whereas a shark's are on the sides of the head. Most batomorphs have a flat, mantle-l ... [...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] |
Lamniformes
The Lamniformes (, from Greek ''lamna'' "fish of prey") are an order (biology), order of sharks commonly known as mackerel sharks (which may also refer specifically to the family Lamnidae). It includes some of the most familiar species of sharks, such as the great white shark, great white as well as less familiar ones, such as the goblin shark and megamouth shark. Members of the order are distinguished by possessing two dorsal fins, an anal fin, five gill, gill slits, eyes without nictitating membranes, and a mouth extending behind the eyes. Species in two families of Lamniformes – Lamnidae and Alopiidae – are distinguished for maintaining a higher body temperature than the surrounding waters. Members of the group include Macro-predator, macropredators, generally of medium-large size, including the largest macropredatory shark ever, the extinct ''Otodus megalodon,'' as well as large planktivores. Although some authors have argued that the Late Jurassic ''Palaeocarcharias'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rajiformes
Rajiformes is one of the four Order (biology), orders in the clade Batomorphi, often referred to as the superorder Batoidea, flattened cartilaginous fishes related to sharks. Rajiforms are distinguished by the presence of greatly enlarged pectoral fins, which reach as far forward as the sides of the head, with a generally flattened body. The undulatory pectoral fin motion diagnostic to this taxon is known as Batoid locomotion, rajiform locomotion. The eyes and Spiracle (vertebrates), spiracles are located on the upper surface of the head and the gill slits are on the underside of the body. Most species give birth to live young, although some lay eggs enclosed in a horny capsule ("mermaid's purse"). Characteristics Rajoids typically have a dorsoventrally flattened body. The snout is slender and pointed and the wide mouth, often covered with a fleshy nasal flap, is on the underside of the head. The eyes and well-developed spiracles are located on the top of the head. In most spec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orectolobiformes
Carpet sharks are sharks classified in the order (biology), order Orectolobiformes . Sometimes the common name "carpet shark" (given because many species resemble ornately patterned carpets) is used interchangeably with "wobbegong", which is the common name of sharks in the family Orectolobidae. Carpet sharks have five gill slits, two spineless dorsal fins, and a small mouth that does not extend past the eyes. Many species have barbel (anatomy), barbels. Characteristics The carpet sharks are a diverse group of sharks with differing sizes, appearances, diets, and habits. They first appeared in the fossil record in the Early Jurassic; the oldest known orectolobiform genera are ''Folipistrix'' (known from Toarcian to Aalenian of Belgium and Germany), ''Palaeobrachaelurus'' (Aalenian to Barremian) and ''Annea (fish), Annea'' (Toarcian to Bajocian of Europe). All species have two dorsal fins and a relatively short, transverse mouth that does not extend behind the eyes. Besides the nost ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hexanchiformes
The Hexanchiformes Help:IPA/English, /hɛkˈsæŋkɪfɔːrmiːz/ are a primitive Order (biology), order of sharks, numbering just five extant species in two Family (biology), families, Chlamydoselachidae and Cow shark, Hexanchidae. Chlamydoselachidae are also known as frilled sharks, these sharks are very rare fishes and typically reside in deeper waters. Hexanchidae are also known as cow sharks and are the lesser known of the two types of Hexanchiformes and also reside in deep waters. Taxonomy Due to their primitive anatomy, hexanchiforms were previously considered the most Basal (phylogenetics), basal group of sharks. However, more recent phylogenetic studies indicate that while primitive, they in fact belong to the superorder Squalomorphi, which also contains Squalidae, dogfishes, angelsharks, and sawsharks, although they are thought to be the most basal member of the group. Description Hexanchiform sharks have one spineless dorsal fin located over or behind the pelvic fin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plesioselachus
''Plesioselachus'' is an extinct genus of Late Devonian (Famennian) cartilaginous fish with uncertain classification, which contains only one species, ''P. macracanthus'' from the Waterloo Farm lagerstätte in South Africa. Known from a single incomplete articulated skeleton and some isolated remains, it is characterized by having a long dorsal spine with length about one third of body length. Description ''Plesioselachus'' was originally classified as elasmobranch, however a redescription placed it under Chondrichthyes since it lacks sufficient data to consider what subgroup it belongs to. The holotype specimen, which has a preserved length of shows most of postcranial elements while lacking most of the head. It is originally considered that preserved lower jaw ( Meckel’s cartilage) and upper jaw ( palatoquadrate), however these materials are more likely to belong to ceratohyal and hyomandibula. The vertebral column is fully preserved, and extends for toward the caudal fin. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Myliobatiformes
Myliobatiformes (), commonly known as stingrays, are one of the four orders of batoids, cartilaginous fishes related to sharks. They are members of the subclass elasmobranchs. They were formerly included in the order Rajiformes, but more recent phylogenetic studies have shown the myliobatiformes to be a monophyletic group, and its more derived members evolved their highly flattened shapes independently of the skates. Characteristics Myliobatiformes share physical characteristics of a long, thin tail with serrated spines and a pancake-like body. They share many characteristics with the batoid order Rajiformes, in which they were previously included. The key difference of the orders is the Myliobatiformes' single-lobed pelvic fin, lack of a mid-tail spine, and general lack of a dorsal fin. Myliobatiformes also possess stinging spines along the tail's base, and generally possess large pectoral fins that are completely fused (except Myliobatidae) to the head. They can camoufla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bandringa
''Bandringa'' is an extinct genus of elasmobranch known from the Pennsylvanian subperiod of the Carboniferous period. There is currently a single known species, ''B. rayi'', which constitutes the sole member of the monotypic family Bandringidae. The genus was described in 1969 by paleontologist Rainer Zangerl, and is known from exceptionally preserved individuals found in the Mazon Creek Lagerstätte of Illinois.R. Zangerl. (1969). ''Bandringa rayi'': A New Ctenacanthoid Shark form the Pennsylvanian Essex Fauna of Illinois. ''Fieldiana Geology'' 12:157-169 Discovery and naming The holotype specimen, FMNH PF 5686, is a juvenile individual which was found in an ironstone concretion in Illinois during the summer of 1967. This specimen was found by Ray Bandringa, to whom the genus and species owe their name. By 1979, two species from this genus were described, ''B. rayi'' and ''B. herdinae'', but the differences between the two were found to be taphonomic in origin. All Mazon Cre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
