Information about Symplesiomorphy
A symplesiomorphy or symplesiomorphic character is in cladistics a trait which is shared (a symmorphy) between two or more taxa, but which is also shared with other taxa which have an earlier last common ancestor with the taxa under consideration. They are therefore not an indication that the taxa considered are more closely related to each other than to the more distant taxa, as all share the more primitive trait. A close phylogenetic relationship, that the taxa form a certain clade to the exclusion of certain other taxa, can only be shown by the discovery of synapomorphies: shared traits that have originated with the last common ancestor of the taxa considered, or at least in the branch, not including the taxa to be excluded, leading to it.
The concept of the symplesiomorphy shows the danger of grouping species together on the basis of general morphologic similarity, without distinguishing between resemblances caused by either primitive or derived traits, as was common before cladistics became popular in the 1980s.
A famous example is pharyngeal gill breathing in bony and cartilaginous fishes. The former are more closely related to Tetrapoda (terrestrial vertebrates, which evolved out of a clade of bony fishes) that breathe via their skin or lungs, rather than to the sharks, rays, et al.. Their kind of gill respiration is shared by the "fishes" because it was present in their common ancestor and lost in the other living vertebrates.
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The concept of the symplesiomorphy shows the danger of grouping species together on the basis of general morphologic similarity, without distinguishing between resemblances caused by either primitive or derived traits, as was common before cladistics became popular in the 1980s.
A famous example is pharyngeal gill breathing in bony and cartilaginous fishes. The former are more closely related to Tetrapoda (terrestrial vertebrates, which evolved out of a clade of bony fishes) that breathe via their skin or lungs, rather than to the sharks, rays, et al.. Their kind of gill respiration is shared by the "fishes" because it was present in their common ancestor and lost in the other living vertebrates.
See also
Cladistics is a philosophy of classification that arranges organisms only by their order of branching in an evolutionary tree and not by their morphological similarity, in the words of Luria et al. (1981).
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For the journal, see .
A taxon (plural taxa), or taxonomic unit, is a name designating an organism or group of organisms. A taxon is assigned a rank and can be placed at a particular level in a systematic hierarchy reflecting evolutionary..... Click the link for more information.
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In evolutionary biology, a synapomorphy is a derived character state shared by two or more terminal groups (taxa included in a cladistic analysis as further indivisible units) and inherited from their most recent common ancestor.
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The term morphology in biology refers to the outward appearance (shape, structure, color, pattern) of an organism or taxon and its component parts. This is in contrast to physiology, which deals primarily with function.
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worldwide view of the subject.
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A gill is a respiration organ that functions for the extraction of oxygen from water and the excretion of carbon dioxide. Unlike many small aquatic animals, which can absorb oxygen through the entire surface of their bodies, more complex aquatic organisms have gills specially
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Osteichthyes
Huxley, 1880
Classes
Actinopterygii
Sarcopterygii
Osteichthyes (IPA: /ˌɒstiːˈɪkθiːz/) are a taxonomic superclass of fish, also called
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Huxley, 1880
Classes
Actinopterygii
Sarcopterygii
Osteichthyes (IPA: /ˌɒstiːˈɪkθiːz/) are a taxonomic superclass of fish, also called
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Chondrichthyes
Huxley, 1880
Subclasses and Orders
See text.
The Chondrichthyes or cartilaginous fishes are jawed fish with paired fins, paired nostrils, scales, two-chambered hearts, and skeletons made of cartilage rather than bone.
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Huxley, 1880
Subclasses and Orders
See text.
The Chondrichthyes or cartilaginous fishes are jawed fish with paired fins, paired nostrils, scales, two-chambered hearts, and skeletons made of cartilage rather than bone.
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Tetrapoda
Broili, 1913
Classes
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Broili, 1913
Classes
- Amphibia
- Aves
- Mammalia
- Sauropsida (Reptilia)
- Synapsida
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Vertebrata
Cuvier, 1812
Classes and Clades
See below
Vertebrates are members of the subphylum Vertebrata (within the phylum Chordata), specifically, those chordates with backbones or spinal columns.
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Cuvier, 1812
Classes and Clades
See below
Vertebrates are members of the subphylum Vertebrata (within the phylum Chordata), specifically, those chordates with backbones or spinal columns.
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SHARK
General
Vincent Rijmen, Joan Daemen, Bart Preneel, Antoon Bosselaers, Erik De Win
1996
KHAZAD, Rijndael
Cipher detail
Key size(s):| 128 bits
Block size(s):| 64 bits
Substitution-permutation network
6
In cryptography,
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General
Vincent Rijmen, Joan Daemen, Bart Preneel, Antoon Bosselaers, Erik De Win
1996
KHAZAD, Rijndael
Cipher detail
Key size(s):| 128 bits
Block size(s):| 64 bits
Substitution-permutation network
6
In cryptography,
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Batoidea
Orders
Rajiformes - common rays and skates
Pristiformes - sawfishes
Torpediniformes - electric rays
See text for families.
Batoidea
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Orders
Rajiformes - common rays and skates
Pristiformes - sawfishes
Torpediniformes - electric rays
See text for families.
Batoidea
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Vertebrata
Cuvier, 1812
Classes and Clades
See below
Vertebrates are members of the subphylum Vertebrata (within the phylum Chordata), specifically, those chordates with backbones or spinal columns.
..... Click the link for more information.
Cuvier, 1812
Classes and Clades
See below
Vertebrates are members of the subphylum Vertebrata (within the phylum Chordata), specifically, those chordates with backbones or spinal columns.
..... Click the link for more information.
Cladistics is a philosophy of classification that arranges organisms only by their order of branching in an evolutionary tree and not by their morphological similarity, in the words of Luria et al. (1981).
..... Click the link for more information.
..... Click the link for more information.
Cladistics is a philosophy of classification that arranges organisms only by their order of branching in an evolutionary tree and not by their morphological similarity, in the words of Luria et al. (1981).
..... Click the link for more information.
..... Click the link for more information.
In evolutionary biology, a synapomorphy is a derived character state shared by two or more terminal groups (taxa included in a cladistic analysis as further indivisible units) and inherited from their most recent common ancestor.
..... Click the link for more information.
..... Click the link for more information.
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