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Halecostomi
Halecostomi is the name of a group of neopterygian fish uniting the halecomorphs (represented by the living bowfin and many extinct groups) and the teleosts, the largest group of extant ray-finned fish. The Halecostomi hypothesis and the Holostei hypothesis are two competing hypotheses explaining the evolutionary relationships of living ray-finned fish. The Holostei hypothesis is better supported, rendering the Halecostomi a paraphyletic group (i.e., rejecting the Halecostomi hypothesis). The Holostei hypothesis posits that Ginglymodi (gars and their fossil relatives) and Halecomorphi Halecomorphi is a taxon of ray-finned bony fish in the clade Neopterygii. The sole living Halecomorph is the bowfin (''Amia calva''), but the group contains many extinct species in several families (including Amiidae, Caturidae, Liodesmidae, ... form a clade, called Holostei, and that the Holostei are the sister group to the Teleostei. References Neopterygii Paraphyletic grou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holostei
Holostei is a group of ray-finned bony fish. It is divided into two major clades, the Halecomorphi, represented by a single living species, the bowfin ('' Amia calva''), as well as the Ginglymodi, the sole living representatives being the gars (Lepisosteidae), represented by seven living species in two genera ('' Atractosteus'', ''Lepisosteus''). The earliest members of the clade appeared during the Early Triassic, over 250 million years ago. Holostei was thought to be regarded as paraphyletic. However, a recent study provided evidence that the Holostei are the closest living relates of the Teleostei, both within the Neopterygii. This was found from the morphology of the Holostei, for example presence of a paired vomer. Holosteans are closer to teleosts than are the chondrosteans, the other group intermediate between teleosts and cartilaginous fish, which are regarded as (at the nearest) a sister group to the Neopterigii. The spiracles of holosteans are reduced to vesti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Halecomorphi
Halecomorphi is a taxon of ray-finned bony fish in the clade Neopterygii. The sole living Halecomorph is the bowfin (''Amia calva''), but the group contains many extinct species in several families (including Amiidae, Caturidae, Liodesmidae, Sinamiidae) in the order Amiiformes, as well as the extinct orders Ionoscopiformes, Panxianichthyiformes, and Parasemionotiformes. The fossil record of halecomorphs goes back at least to the Early Triassic epoch. The Halecomorphi exhibit a combination of ancestral features, such as most heavily mineralized scales, but also by more derived or "modern" features, particularly in the structure of the skull (e.g. position and shape of preopercles). Unique derived traits (synapomorphies) of the Halecomorphi include: *Unique jaw articulation in which the quadrate and symplectic participate in the joint. *Lengthened dorsal fins (in some species) *Two biconcave vertebrae per segment in the posterior body region (a condition known as d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Halecomorph
Halecomorphi is a taxon of ray-finned bony fish in the clade Neopterygii. The sole living Halecomorph is the bowfin (''Amia calva''), but the group contains many extinct species in several families (including Amiidae, Caturidae, Liodesmidae, Sinamiidae) in the order Amiiformes, as well as the extinct orders Ionoscopiformes, Panxianichthyiformes, and Parasemionotiformes. The fossil record of halecomorphs goes back at least to the Early Triassic epoch. The Halecomorphi exhibit a combination of ancestral features, such as most heavily mineralized scales, but also by more derived or "modern" features, particularly in the structure of the skull (e.g. position and shape of preopercles). Unique derived traits (synapomorphies) of the Halecomorphi include: *Unique jaw articulation in which the quadrate and symplectic participate in the joint. *Lengthened dorsal fins (in some species) *Two biconcave vertebrae per segment in the posterior body region (a condition known as dip ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bowfin
The bowfin (''Amia calva'') is a bony fish, native to North America. Common names include mudfish, mud pike, dogfish, grindle, grinnel, swamp trout, and choupique. It is regarded as a relict, being the sole surviving species of the Halecomorphi, a group of fish that first appeared during the Early Triassic, around 250 million years ago. The bowfin is often considered a " primitive fish" because they have retained some morphological characteristics of their early ancestors. The closest living relatives of bowfins are gars, with the two groups being united in the clade Holostei. Bowfins are demersal freshwater piscivores, commonly found throughout much of the eastern United States, and in southern Ontario and Quebec. Fossil deposits indicate Amiiformes were once widespread in both freshwater and marine environments across North and South America, Europe, Asia, and Africa. Now, their range is limited to much of the eastern United States and adjacent southern Canada, including ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amia Calva (white Background)
The bowfin (''Amia calva'') is a bony fish, native to North America. Common names include mudfish, mud pike, dogfish, grindle, grinnel, swamp trout, and choupique. It is regarded as a relict, being the sole surviving species of the Halecomorphi, a group of fish that first appeared during the Early Triassic, around 250 million years ago. The bowfin is often considered a "primitive fish" because they have retained some morphological characteristics of their early ancestors. The closest living relatives of bowfins are gars, with the two groups being united in the clade Holostei. Bowfins are demersal freshwater piscivores, commonly found throughout much of the eastern United States, and in southern Ontario and Quebec. Fossil deposits indicate Amiiformes were once widespread in both freshwater and marine environments across North and South America, Europe, Asia, and Africa. Now, their range is limited to much of the eastern United States and adjacent southern Canada, including the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alligator Gar Fish (white Background)
An alligator is a large reptile in the Crocodilia order in the genus ''Alligator'' of the family Alligatoridae. The two extant species are the American alligator (''A. mississippiensis'') and the Chinese alligator (''A. sinensis''). Additionally, several extinct species of alligator are known from fossil remains. Alligators first appeared during the Oligocene epoch about 37 million years ago. The name "alligator" is probably an anglicized form of ', the Spanish term for "the lizard", which early Spanish explorers and settlers in Florida called the alligator. Later English spellings of the name included ''allagarta'' and ''alagarto''. Evolution Alligators and caimans split in North America during the early Tertiary or late Cretaceous (about 53 million to about 65 million years ago). The Chinese alligator split from the American alligator about 33 million years ago and probably descended from a lineage that crossed the Bering land bridge during the Neogene. The modern Ame ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clade
A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, the equivalent Latin term ''cladus'' (plural ''cladi'') is often used in taxonomical literature. The common ancestor may be an individual, a population, or a species (extinct or extant). Clades are nested, one in another, as each branch in turn splits into smaller branches. These splits reflect evolutionary history as populations diverged and evolved independently. Clades are termed monophyletic (Greek: "one clan") groups. Over the last few decades, the cladistic approach has revolutionized biological classification and revealed surprising evolutionary relationships among organisms. Increasingly, taxonomists try to avoid naming taxa that are not clades; that is, taxa that are not monophyletic. Some of the relationships between org ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ginglymodi
Ginglymodi is a clade of ray-finned fish containing modern-day gars (Lepisosteidae) and their extinct relatives, including the family Lepidotidae and the orders Semionotiformes and Kyphosichthyiformes, and various other extinct taxa. Ginglymodi is one of the two major subgroups of the infraclass Holostei, the other one being Halecomorphi, which contains the bowfin and its fossil relatives. Fossil record The fossil record of ginglymodians goes back at least to the Anisian stage of the Triassic period, over 240 million years ago. ''Eosemionotus'' is one of the earliest ginglymodians. ''Acentrophorus'', another taxon from the Wuchiapingian stage of the late Permian, and ''Paracentrophorus'' from the Early Triassic epoch, could be even earlier members of the group. Ginglymodi was diverse and widespread during the Mesozoic era, but they represent a depauperate lineage today. The group first evolved in marine environments, but several lineages made separate tr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paraphyletic
In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be paraphyletic ''with respect to'' the excluded subgroups. In contrast, a monophyletic group (a clade) includes a common ancestor and ''all'' of its descendants. The terms are commonly used in phylogenetics (a subfield of biology) and in the tree model of historical linguistics. Paraphyletic groups are identified by a combination of Synapomorphy and apomorphy, synapomorphies and symplesiomorphy, symplesiomorphies. If many subgroups are missing from the named group, it is said to be polyparaphyletic. The term was coined by Willi Hennig to apply to well-known taxa like Reptilia (reptiles) which, as commonly named and traditionally defined, is paraphyletic with respect to mammals and birds. Reptilia contains the last common ancestor of reptiles a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phylogeny
A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological species or other entities based upon similarities and differences in their physical or genetic characteristics. All life on Earth is part of a single phylogenetic tree, indicating common ancestry. In a ''rooted'' phylogenetic tree, each node with descendants represents the inferred most recent common ancestor of those descendants, and the edge lengths in some trees may be interpreted as time estimates. Each node is called a taxonomic unit. Internal nodes are generally called hypothetical taxonomic units, as they cannot be directly observed. Trees are useful in fields of biology such as bioinformatics, systematics, and phylogenetics. ''Unrooted'' trees illustrate only the relatedness of the leaf nodes and do not require the ancestral root ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cladogram Of Basal Actinopterygians And Neopterygians
A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to descendants, nor does it show how much they have changed, so many differing evolutionary trees can be consistent with the same cladogram. A cladogram uses lines that branch off in different directions ending at a clade, a group 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 can be 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 ance ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hypotheses
A hypothesis (plural hypotheses) is a proposed explanation for a phenomenon. For a hypothesis to be a scientific hypothesis, the scientific method requires that one can test it. Scientists generally base scientific hypotheses on previous observations that cannot satisfactorily be explained with the available scientific theories. Even though the words "hypothesis" and "theory" are often used interchangeably, a scientific hypothesis is not the same as a scientific theory. A working hypothesis is a provisionally accepted hypothesis proposed for further research in a process beginning with an educated guess or thought. A different meaning of the term ''hypothesis'' is used in formal logic, to denote the antecedent of a proposition; thus in the proposition "If ''P'', then ''Q''", ''P'' denotes the hypothesis (or antecedent); ''Q'' can be called a consequent. ''P'' is the assumption in a (possibly counterfactual) ''What If'' question. The adjective ''hypothetical'', meaning "ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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