Information: - Chondrostei are primarily cartilaginous fish showing some degree of ossification. It is thought that the cartilaginous condition is derived, and that the ancestors of this group were bony fish with fully ossified skeletons. Members of this group share with the Elasmobranchii certain features such as the possession of spiracles, a heterocercal tail and the absence of scales. Nevertheless, the fossil record suggests they have more in common with the teleosts. The Chondrostei is probably a paraphyletic grouping; the fifty-two living species are divided among two orders, the Acipenseriformes (sturgeons and paddlefishes), and the Polypteriformes (reedfishes and bichirs). - Neopterygii are a group of Actinopteri animals. Neopterygii means "new fins". Only a few changes occurred during their evolution from the earlier actinopterygians. They appeared sometime in the Late Permian, before the time of the dinosaurs. The Neopterygii are a very successful group of fish, because they can move more rapidly than their ancestors. Their scales and skeletons began to lighten during their evolution, and their jaws became more powerful and efficient. While electroreception and the ampullae of Lorenzini are present in all other groups of fish, with the exception of hagfish (although hagfish are not Actinopterygii, they are Agnathans}, Neopterygii have lost this sense, even if it has later been re-evolved within Gymnotiformes and catfishes, which possess nonhomologous teleost ampullae. - The Triassic is a geologic period and system which spans 50.9 million years from the end of the Permian Period million years ago (Mya), to the beginning of the Jurassic Period Mya. The Triassic is the first period of the Mesozoic Era. Both the start and end of the period are marked by major extinction events. The Triassic was named in 1834 by Friedrich von Alberti, after the three distinct rock layers ("tri" meaning "three") that are found throughout Germany and northwestern Europered beds, capped by marine limestone, followed by a series of terrestrial mud- and sandstonescalled the "Trias". - The teleosts or Teleostei (Greek: "teleios", "complete" + "osteon", "bone") are by far the largest infraclass in the class Actinopterygii, the ray-finned fishes, and make up 96 percent of all fish. This diverse group arose in the Triassic period and members are arranged in about 40 orders and 448 families. Over 26,000 species have been described. Teleosts range from giant oarfish, measuring or more, and ocean sunfish weighing over , to the minute male anglerfish "Photocorynus spiniceps", just long. As well as torpedo-shaped fish built for speed, teleosts can be flattened vertically or horizontally, be elongated cylinders or take specialised shapes as in anglerfish and seahorses. Teleosts dominate the seas from pole to pole and inhabit the ocean depths, estuaries, rivers, lakes and even swamps. - The reedfish, ropefish (more commonly used in the United States), or snakefish, "Erpetoichthys calabaricus", is a species of freshwater fish in the bichir family and order. It is the only member of the genus Erpetoichthys. It is native to West and Central Africa. The reedfish possesses a pair of lungs in addition to gills, allowing it to survive in very oxygen-poor water. It is threatened by habitat loss through palm oil plantations and urban development. - Catfish (or catfishes; order Siluriformes or Nematognathi) are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the three largest species, the Mekong giant catfish from Southeast Asia, the wels catfish of Eurasia and the Piraiba of South America, to detritivores (species that eat dead material on the bottom), and even to a tiny parasitic species commonly called the candiru, "Vandellia cirrhosa". There are armour-plated types and there are also naked types, neither having scales. Despite their name, not all catfish have prominent barbel. Members of the Siluriformes order are defined by features of the skull and swimbladder. Catfish are of considerable commercial importance; many of the larger species are farmed or fished for food. Many of the smaller species, particularly the genus "Corydoras", are important in the aquarium hobby. Many catfish are nocturnal, but others (many "Auchenipteridae") are "crepuscular" or "diurnal" (most "Loricariidae or" "Callichthyidae" for example). - Sturgeon is the common name for the 27 species of fish belonging to the family Acipenseridae. Their evolution dates back to the Triassic some 245 to 208 million years ago. The family is grouped into four genera: "Acipenser", "Huso", "Scaphirhynchus" and "Pseudoscaphirhynchus". Four species may now be extinct. Two closely related species, "Polyodon spathula" (paddlefish) and "Psephurus gladius" (Chinese paddlefish, possibly extinct) are of the same order, Acipenseriformes, but are in the family Polyodontidae and are not considered to be "true" sturgeons. Both sturgeons and paddlefish have been referred to as "primitive fishes" because their morphological characteristics have remained relatively unchanged since the earliest fossil record. Sturgeons are native to subtropical, temperate and sub-Arctic rivers, lakes and coastlines of Eurasia and North America. Sturgeons are long-lived, late-maturing fishes with distinctive characteristics, such as a heterocercal caudal fin similar to that of sharks, and an elongated spindle-like body that is smooth-skinned, scaleless and armored with 5 lateral rows of bony plates called scutes. Several species can grow quite large, typically ranging 712 feet (2-3 m) in length. The largest sturgeon on record was a Beluga female captured in the Volga estuary in 1827, weighing and long. Most sturgeons are anadromous bottom-feeders which migrate upstream to spawn but spend most of their lives feeding in river deltas and estuaries. Some species inhabit freshwater environments exclusively while others primarily inhabit marine environments near coastal areas, and are known to venture into open ocean. - A sister group or sister taxon is a phylogenetic term denoting the closest relatives of another given unit in an evolutionary tree. The expression is most easily illustrated by a cladogram: A, B, and C each represent a taxon: - Hagfish, the class Myxini (also known as Hyperotreti), are eel-shaped, slime-producing marine fish (occasionally called slime eels). They are the only known living animals that have a skull but no vertebral column. Along with lampreys, hagfish are jawless; they are the sister group to vertebrates, and living hagfish remain similar to hagfish from around 300 million years ago. - Acipenseriformes is an order of basal ray-finned fishes that includes the sturgeons and paddlefishes, as well as some extinct families. - Paddlefish (family Polyodontidae) are basal Chondrostean ray-finned fish. They have been referred to as "primitive fish" because they have evolved with few morphological changes since the earliest fossil records of the Late Cretaceous, seventy to seventy-five million years ago. Polyodontids are exclusively North American and Chinese. - Actinopteri is the sister group of Cladistia . Dating back to the Permian period , the Actinopteri comprise the Chondrostei ( sturgeons and paddlefishes ) and the Neopterygii ( bowfin , gars , and teleosts ) . In other words , the Actinopteri include all extant Actinopterygians , minus the Polypteridae ( African bichirs and ropefish ) . The Actinopteri includes : Chondrostei Acipenseriformes Acipenseroidei Neopterygii Amiiformes Amiidae Semionotiformes Lepisosteidae Teleostei Elopocephala Osteoglossomorpha - The Gymnotiformes are a group of teleost bony fishes commonly known as the Neotropical or South American knifefish. They have long bodies and swim using undulations of their elongated anal fin. Found exclusively in fresh water, these mostly nocturnal fish are capable of producing electric fields for navigation, communication, and, in the case of the electric eel ("Electrophorus electricus"), attack and defense. A few species are familiar to the aquarium trade, such as the black ghost knifefish ("Apteronotus albifrons"), the glass knifefish ("Eigenmannia virescens"), and the banded knifefish ("Gymnotus carapo"). - Elasmobranchii is a subclass of Chondrichthyes or cartilaginous fish. Members of this subclass are characterised by having five to seven pairs of gill clefts 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. - A cladogram (from Greek "clados" "branch" and "gramma" "character") is a diagram used in cladistics which shows relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to descendants or how much they have changed; many evolutionary trees can be inferred from a single cladogram. A cladogram uses lines that branch off in different directions ending at a clade, a groups of organisms with a last common ancestor. There are many shapes of cladograms but they all have lines that branch off from other lines. The lines can be traced back to where they branch off. These branching off points represent a hypothetical ancestor (not an actual entity) which is inferred to exhibit the traits shared among the terminal taxa above it. This hypothetical ancestor might then provide clues about the order of evolution of various features, adaptation, and other evolutionary narratives about ancestors. Although traditionally such cladograms were generated largely on the basis of morphological characters, DNA and RNA sequencing data and computational phylogenetics are now very commonly used in the generation of cladograms, either on their own or in combination with morphology. - The bichirs and reedfish (also called ropefish) comprise the Polypteridae, a family of archaic-looking ray-finned fishes and the sole family in the order Polypteriformes. - The Permian is a geologic period and system which spans 46.7 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 252.2 Mya. It is the last period of the Paleozoic Era; the following Triassic Period belongs to the Mesozoic Era. The concept of the Permian was introduced in 1841 by geologist Sir Roderick Murchison, who named it after the city of Perm. 'actinopteri' is related to which object entity through the relation of 'taxon rank'? Choices: - branch - class - family - genus - group - infraclass - order - series - species - subclass
infraclass