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In
taxonomy Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a specific classification scheme. Originally used only about biological ...
, a group is paraphyletic if it consists of the group's
last common ancestor In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms ...
and all its descendants, but excluding a few—typically only one or two—
monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic grou ...
subgroups. The group is said to be paraphyletic ''with respect to'' the excluded subgroups. In contrast, a monophyletic group (a
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, monophyletic – that is, composed of a common ancestor and all its lineage (evolution), lineal descendants - on a phylogenetic tree. R ...

clade
) includes a common ancestor and ''all'' of its descendants. The terms are commonly used in
phylogenetics In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanism ...

phylogenetics
(a subfield of
biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms, Development ...

biology
) and in the
tree model In historical linguistics Historical linguistics, also termed diachronic linguistics, is the scientific study of language change over time. Principal concerns of historical linguistics include: # to describe and account for observed change ...
of
historical linguistics Historical linguistics, also termed diachronic linguistics, is the scientific study of language change Language change is variation over time in a language A language is a structured system of communication used by humans, including s ...
. Paraphyletic groups are identified by a combination of
synapomorphies 279px, trait states. In phylogenetics, apomorphy and synapomorphy refer to derived characters of a clade A clade (; from grc, , ''klados'', "branch"), also known as a monophyletic group or natural group, is a group of organisms that are mon ...
and symplesiomorphies. If many subgroups are missing from the named group, it is said to be polyparaphyletic. The term was coined by
Willi Hennig Emil Hans Willi Hennig (20 April 1913 – 5 November 1976) was a German German(s) may refer to: Common uses * of or related to Germany * Germans, Germanic ethnic group, citizens of Germany or people of German ancestry * For citizens of German ...

Willi Hennig
to apply to well-known taxa like Reptilia (
reptiles Reptiles, as most commonly defined, are the animals in the class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or ...

reptiles
) which, as commonly named and traditionally defined, is paraphyletic with respect to
mammal Mammals (from Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meaning "to share" or "to be i ...
s and
bird Birds are a group of warm-blooded vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With ...

bird
s. Reptilia contains the last common ancestor of reptiles and all descendants of that ancestor, including all extant reptiles as well as the extinct
synapsids Synapsids are a group of animals that includes mammal Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals constituting the class (biology), class Mammalia (), and characterized by the presence of mammary glan ...
, except for mammals and birds. Other commonly recognized paraphyletic groups include
fish Fish are aquatic Aquatic means relating to water Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the ...

fish
,
monkey Monkey is a common name that may refer to most mammals of the infraorder In biological classification In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structur ...

monkey
s, and
lizard Lizards (suborder Lacertilia) are a widespread group of Squamata, squamate reptiles, with over 6,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic as it excludes the s ...

lizard
s.


Etymology

The term ''paraphyly'', or ''paraphyletic'', derives from the two
Ancient Greek Ancient Greek includes the forms of the Greek language Greek ( el, label=Modern Greek Modern Greek (, , or , ''Kiní Neoellinikí Glóssa''), generally referred to by speakers simply as Greek (, ), refers collectively to the diale ...
words (), meaning "beside, near", and (), meaning "genus, species", and refers to the situation in which one or several monophyletic subgroups of organisms (e.g., genera, species) are ''left apart'' from all other descendants of a unique common ancestor. Conversely, the term ''
monophyly In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic grou ...
'', or ''monophyletic'', builds on the Ancient Greek prefix (), meaning "alone, only, unique", and refers to the fact that a monophyletic group includes organisms consisting of ''all'' the descendants of a ''unique'' common ancestor. By comparison, the term ''
polyphyly A polyphyletic group or assemblage is a set of organisms, or other evolving elements, that have been grouped together based on characteristics that do not imply that they share a common ancestor that is not also the common ancestor of many othe ...
'', or ''polyphyletic'', uses the Ancient Greek prefix (), meaning "many, a lot of", and refers to the fact that a polyphyletic group includes organisms arising from ''multiple'' ancestral sources.


Phylogenetics


In cladistics

Groups that include all the descendants of a common ancestor are said to be ''
monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic grou ...

monophyletic
''. A paraphyletic group is a monophyletic group from which one or more subsidiary
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, monophyletic – that is, composed of a common ancestor and all its lineage (evolution), lineal descendants - on a phylogenetic tree. R ...

clade
s (monophyletic groups) are excluded to form a separate group. Philosopher of science Marc Ereshefsky has argued that paraphyletic taxa are the result of
anagenesis Anagenesis is the gradual evolution Evolution is change in the Heredity, heritable Phenotypic trait, characteristics of biological populations over successive generations. These characteristics are the Gene expression, expressions of genes th ...
in the excluded group or groups. Cladists do not grant paraphyletic assemblages the status of "groups" or reify them with explanations, because they represent evolutionary non-events A group whose identifying features evolved convergently in two or more lineages is ''
polyphyletic 300px, Cladogram of the primates, showing a monophyly (the simians, in yellow), a paraphyly">monophyly.html" ;"title="primates, showing a monophyly">primates, showing a monophyly (the simians, in yellow), a paraphyly (the prosimians, in cyan, inc ...

polyphyletic
'' (Greek πολύς 'polys'' "many"). More broadly, any taxon that is not paraphyletic or monophyletic can be called polyphyletic. Empirically, the distinction between polyphyletic groups and paraphyletic groups is rather arbitrary, since the character states of common ancestors are inferences, not observations. These terms were developed during the debates of the 1960s and 1970s accompanying the rise of
cladistics Cladistics (; ) is an approach to biological classification In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular ...

cladistics
. Paraphyletic groupings are considered problematic by many taxonomists, as it is not possible to talk precisely about their phylogenetic relationships, their characteristic traits and literal extinction. Related terms are
stem group upright=1.5, Two distinct crown groups (in red) are illustrated, connected by an ancestor (black circle). The two groups form a larger crown group (lilac). In phylogenetics In biology Biology is the natural science that studies life and ...
,
chronospecies A chronospecies is a species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organ ...

chronospecies
, budding cladogenesis, anagenesis, or 'grade' groupings. Paraphyletic groups are often relics from outdated hypotheses of phylogenic relationships from before the rise of cladistics.


Examples

The
prokaryotes A prokaryote () is a single-celled organism A unicellular organism, also known as a single-celled organism, is an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contig ...

prokaryotes
(single-celled life forms without cell nuclei) are a paraphyletic grouping, because they exclude the
eukaryotes Eukaryotes () are organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous system that embodies the Life#Biology, properties of life. It is a synonym for "Outline ...
, a descendant group.
Bacteria Bacteria (; common noun bacteria, singular bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typ ...

Bacteria
and
Archaea Archaea ( ; singular archaeon ) constitute a domain Domain may refer to: Mathematics *Domain of a function, the set of input values for which the (total) function is defined **Domain of definition of a partial function **Natural domain of a pa ...

Archaea
are prokaryotes, but archaea and eukaryotes share a common ancestor that is not ancestral to the bacteria. The prokaryote/eukaryote distinction was proposed by Edouard Chatton in 1937 and was generally accepted after being adopted by Roger Stanier and C.B. van Niel in 1962. The botanical code (the ICBN, now the ICN) abandoned consideration of bacterial nomenclature in 1975; currently, prokaryotic nomenclature is regulated under the ICNB with a starting date of 1 January 1980 (in contrast to a 1753 start date under the ICBN/ICN). Among plants,
dicotyledon The dicotyledons, also known as dicots (or more rarely dicotyls), are one of the two groups into which all the flowering plant The flowering plants, also known as Angiospermae (), or Magnoliophyta (), are the most diverse group of Embryophyte ...
s (in the traditional sense) are paraphyletic because the group excludes
monocotyledon Monocotyledons (), commonly referred to as monocots, (Lilianae ''sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one Embryo#Plant embryos, embryonic leaf, or cotyledon. Th ...
s. "Dicotyledon" has not been used as a botanic classification for decades, but is allowed as a synonym of Magnoliopsida.The history of flowering plant classification can be found under . Phylogenetic analysis indicates that the
monocot Monocotyledons (), commonly referred to as monocots, (Lilianae ''sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one Embryo#Plant embryos, embryonic leaf, or cotyledon. The ...
s are a development from a
dicot The dicotyledons, also known as dicots (or more rarely dicotyls), are one of the two groups into which all the flowering plant Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "a ...
ancestor. Excluding monocots from the dicots makes the latter a paraphyletic group.. "It is now thought that the possession of two cotyledons is an ancestral feature for the taxa of the flowering plants and not an apomorphy for any group within. The 'dicots' ... are paraphyletic ...." Among animals, several familiar groups are not, in fact, clades. The order
Artiodactyla The even-toed ungulates (Artiodactyla , ) are ungulate Ungulates ( ) are members of the diverse Ungulata which primarily consists of large mammals with . These include s such as s, es, and s; and s such as , s, s, s, , , and es. s such as , ...

Artiodactyla
(
even-toed ungulate The even-toed ungulates (Artiodactyla , ) are ungulates—hoofed animals—which bear weight equally on two (an even number) of their five toes: the third and fourth. The other three toes are either present, absent, vestigial, or pointing poster ...
s) as traditionally defined is paraphyletic because it excludes
Cetacea Cetaceans (from la, cetus Cetus () is a constellation, sometimes called 'the whale' in English. The Cetus (mythology), Cetus was a sea monster in Greek mythology which both Perseus and Heracles needed to slay. Cetus is in the region of the ...

Cetacea
ns (whales, dolphins, etc.). Under the ranks of the ICZN Code, the two taxa are separate orders. Molecular studies, however, have shown that the Cetacea descend from artiodactyl ancestors, although the precise phylogeny within the order remains uncertain. Without the Cetaceans the Artiodactyls are paraphyletic. The class
Reptilia Reptiles are tetrapod Tetrapods (; from Greek 'four' and 'foot') are four-limbed animals constituting the superclass Tetrapoda . It includes extant and extinct amphibians, reptiles (including dinosaurs and therefore birds), and synapsids ...

Reptilia
, as traditionally defined, is paraphyletic because it excludes birds (class
Aves Birds are a group of warm-blooded vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With ...

Aves
) and mammals. Under the ranks of the ICZN Code, these three taxa are separate classes. However, mammals hail from the
synapsids Synapsids are a group of animals that includes mammal Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals constituting the class (biology), class Mammalia (), and characterized by the presence of mammary glan ...
(which were once described as "mammal-like reptiles") and birds are sister taxon to a group of dinosaurs (part of
Diapsida Diapsids ("two arches") are a group of amniote Amniotes (from Greek ἀμνίον ''amnion'', "membrane surrounding the fetus", earlier "bowl in which the blood of sacrificed animals was caught", from ἀμνός ''amnos'', "lamb") are a cla ...
), both of which are "reptiles". Romer, A. S. & Parsons, T. S. (1985): ''The Vertebrate Body.'' (6th ed.) Saunders, Philadelphia. Alternatively, reptiles are paraphyletic because they gave rise to (only) birds. Birds and reptiles together make
Sauropsids Sauropsida ("lizard faces") is a clade A clade (; from grc, , ''klados'', "branch"), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, monophyletic—that is, composed of a common ancestor and al ...
, a clade of
Amniota Amniotes (from Greek ἀμνίον ''amnion'', "membrane surrounding the fetus", earlier "bowl in which the blood of sacrificed animals was caught", from ἀμνός ''amnos'', "lamb") are a clade A clade (; from grc, , ''klados'', "bran ...

Amniota
that is the sister group of the clade that includes mammals.
Osteichthyes Osteichthyes (), popularly referred to as the bony fish, is a diverse taxonomic Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may al ...

Osteichthyes
, bony fish, are paraphyletic when circumscribed to include only
Actinopterygii Actinopterygii (New Latin New Latin (also called Neo-Latin or modern Latin) is the revival of Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally spoke ...
(ray-finned fish) and
Sarcopterygii Sarcopterygii (; ) — sometimes considered synonymous with Crossopterygii () — is a taxon In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, ...

Sarcopterygii
(lungfish, etc.), and to exclude
tetrapod Tetrapods (; ) are four-limbed animals constituting the superclass Tetrapoda (). It includes extant Extant is the opposite of the word extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a sp ...
s; more recently, Osteichthyes is treated as a clade, including the tetrapods. The "wasps" are paraphyletic, consisting of the narrow-waisted
Apocrita The Apocrita are a suborder (biology), suborder of insects in the order Hymenoptera. It includes wasps, bees, and ants, and consists of many families. It contains the most advanced hymenopterans and is distinguished from Sawfly, Symphyta by the n ...
without the
ant Ants are eusocial Eusociality (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population i ...

ant
s and
bee Bees are flying insects closely related to wasps and ants, known for their role in pollination and, in the case of the best-known bee species, the western honey bee, for producing honey. Bees are a monophyly, monophyletic lineage within the ...

bee
s. The sawflies (
Symphyta Sawflies are the insects of the suborder In biological classification, the order ( la, wikt:ordo#Latin, ordo) is # a taxonomic rank used in the classification of organisms and recognized by the nomenclature codes. The well-known ranks in de ...
) are similarly paraphyletic, forming all of the
Hymenoptera Hymenoptera is a large order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanliness Cleanliness is both the abstract state of being clean and free from germs, dirt, trash, or wa ...

Hymenoptera
except for the Apocrita, a clade deep within the sawfly tree.
Crustacean Crustaceans (Crustacea ) form a large, diverse arthropod taxon which includes such animals as crabs, lobsters, crayfish, Caridea, shrimp, krill, Dendrobranchiata, prawns, woodlice, barnacles, copepods, amphipoda, amphipods and mantis shrimp. The ...
s are not a clade because the
Hexapoda The subphylum Hexapoda (from Greek language, Greek for 'six legs') comprises most species of arthropods and includes the insects as well as three much smaller groups of wingless arthropods: Springtail, Collembola, Protura, and Diplura (all of the ...
(insects) are excluded. The modern clade that spans all of them is the Tetraconata. One of the goals of modern taxonomy over the past fifty years has been to eliminate paraphyletic "groups", such as the examples given here, from formal classifications.


Paraphyly in species

Species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individu ...

Species
have a special status in systematics as being an observable feature of nature itself and as the basic unit of classification. Some articulations of the
phylogenetic species concept In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individu ...
require species to be monophyletic, but paraphyletic species are common in nature, to the extent that they do not have a single common ancestor. Indeed, for sexually reproducing taxa, no species has a "single common ancestor" organism. Paraphyly is common in
speciation Speciation is the evolutionary process by which populations evolve to become distinct species. The biologist Orator F. Cook coined the term in 1906 for cladogenesis, the splitting of lineages, as opposed to anagenesis, phyletic evolution within ...

speciation
, whereby a mother species (a
paraspeciesA paraspecies (a paraphyletic species) is a species, living or fossil, that gave rise to one or more daughter species without itself becoming extinct. Geographically widespread species that have given rise to one or more daughter species as periphera ...
) gives rise to a daughter species without itself becoming extinct. Research indicates as many as 20 percent of all animal species and between 20 and 50 percent of plant species are paraphyletic. Accounting for these facts, some taxonomists argue that paraphyly is a trait of nature that should be acknowledged at higher taxonomic levels. Cladists advocate a phylogenetic species concept that does not consider species to exhibit the properties of monophyly or paraphyly, concepts under that perspective which apply only to groups of species. They consider Zander's extension of the "paraphyletic species" argument to higher taxa to represent a category error


Uses for paraphyletic groups

When the appearance of significant traits has led a subclade on an evolutionary path very divergent from that of a more inclusive clade, it often makes sense to study the paraphyletic group that remains without considering the larger clade. For example, the
Neogene The Neogene ( ) (informally Upper Tertiary or Late Tertiary) is a geologic period and system that spans 20.45 million years from the end of the Paleogene The Paleogene ( ; also spelled Palaeogene or Palæogene; informally Lower Tertiary or E ...

Neogene
evolution of the
Artiodactyla The even-toed ungulates (Artiodactyla , ) are ungulate Ungulates ( ) are members of the diverse Ungulata which primarily consists of large mammals with . These include s such as s, es, and s; and s such as , s, s, s, , , and es. s such as , ...
(even-toed ungulates, like deer, cows, pigs and hippopotamuses - note that
Cervidae Deer or true deer are hoofed ruminant mammals forming the family (biology), family Cervidae. The two main groups of deer are the Cervinae, including the muntjac, the elk (wapiti), the red deer, and the fallow deer; and the Capreolinae, includ ...

Cervidae
,
Bovidae The Bovidae comprise the biological family Family ( la, familia, plural ') is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy; it is classified between order (biology), order and genus. A family may be divided into su ...
,
Suidae Suidae is a family In human society A society is a Social group, group of individuals involved in persistent Social relation, social interaction, or a large social group sharing the same spatial or social territory, typically subject ...
and
Hippopotamidae :''This is the article on the family Hippopotamidae; for the main article on hippos, see Hippopotamus The hippopotamus ( ; ''Hippopotamus amphibius''), also called the hippo, common hippopotamus or river hippopotamus, is a large, mostly herbi ...

Hippopotamidae
, the families that contain these various artiodactyls, are all monophyletic groups) has taken place in environments so different from that of the
Cetacea Cetaceans (from la, cetus Cetus () is a constellation, sometimes called 'the whale' in English. The Cetus (mythology), Cetus was a sea monster in Greek mythology which both Perseus and Heracles needed to slay. Cetus is in the region of the ...

Cetacea
(whales, dolphins, and porpoises) that the Artiodactyla are often studied in isolation even though the cetaceans are a descendant group. The
prokaryote A prokaryote () is a single-celled organism A unicellular organism, also known as a single-celled organism, is an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contig ...
group is another example; it is paraphyletic because it is composed of two Domains (Eubacteria and Archaea) and excludes (the
eukaryotes Eukaryotes () are organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous system that embodies the Life#Biology, properties of life. It is a synonym for "Outline ...
). It is very useful because it has a clearly defined and significant distinction (absence of a cell nucleus, a
plesiomorphy In phylogenetics In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, phy ...

plesiomorphy
) from its excluded descendants. Also, some systematists recognize paraphyletic groups as being involved in evolutionary transitions, the development of the first tetrapods from their ancestors for example. Any name given to these hypothetical ancestors to distinguish them from tetrapods—"fish", for example—necessarily picks out a paraphyletic group, because the descendant tetrapods are not included. Other systematists consider reification of paraphyletic groups to obscure inferred patterns of evolutionary history. The term "
evolutionary grade In alpha taxonomy, a grade is a taxon united by a level of morphological or physiological complexity. The term was coined by British biologist Julian Huxley, to contrast with clade A clade (; from grc, , ''klados'', "branch"), also known ...
" is sometimes used for paraphyletic groups. Moreover, the concepts of
monophyly In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic grou ...
, paraphyly, and
polyphyly A polyphyletic group or assemblage is a set of organisms, or other evolving elements, that have been grouped together based on characteristics that do not imply that they share a common ancestor that is not also the common ancestor of many othe ...
have been used in deducing key genes for barcoding of diverse group of species.


Independently evolved traits

Current phylogenetic hypotheses of tetrapod relationships imply that
viviparity Among animals, viviparity is development of the embryo inside the body of the parent. This is opposed to oviparity which is a reproductive mode in which females lay developing eggs that complete their development and hatch externally from the mo ...
, the production of offspring without the external laying of a fertilized egg, developed independently in the lineages that led to humans (''Homo sapiens'') and southern water skinks (''Eulampus tympanum'', a kind of lizard). Put another way, viviparity is a synapomorphy for
Theria Theria (; Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximatel ...
within mammals, and an autapomorphy for ''
Eulamprus tympanum ''Eulamprus'' is a genus of lizards, commonly known as water skinks, in the subfamily Lygosominae of the Family (biology), family Scincidae. The genus is native to Australia. Taxonomy The genus ''Eulamprus'' belongs to a clade in the ''Sphenomo ...
'' (or perhaps a synapomorphy, if other ''Eulamprus'' species are also viviparous). "Groups" based on independently-developed traits such as these examples of viviparity represent examples of
polyphyly A polyphyletic group or assemblage is a set of organisms, or other evolving elements, that have been grouped together based on characteristics that do not imply that they share a common ancestor that is not also the common ancestor of many othe ...
, not paraphyly.


Not paraphyly

*
Amphibious fish 300px, Mudskippers (''Periophthalmus gracilis'' shown) are among the most land adapted of fish (excepting, from a cladistic perspective, tetrapods), and are able to spend days moving about out of water. Amphibious fish are fish that are able to le ...
are polyphyletic, not paraphyletic. Although they appear similar, several different groups of amphibious fishes such as
mudskipper Mudskippers are amphibious fish 300px, Mudskippers (''Periophthalmus gracilis'' shown) are among the most land adapted of fish (excepting, from a cladistic perspective, tetrapods), and are able to spend days moving about out of water. Amphibious ...

mudskipper
s and
lungfish Lungfish are freshwater rhipidistian vertebrates belonging to the Order (taxonomic rank), order Dipnoi. Lungfish are best known for retaining ancestral characteristics within the Osteichthyes, including the ability to breathe air, and ancestral ...
es evolved independently in a process of
convergent evolution Convergent evolution is the independent evolution Evolution is change in the heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to their offspring; eit ...
in distant relatives faced with similar ecological circumstances. *
Flightless bird Flightless birds are bird Birds are a group of warm-blooded vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), ...
s are polyphyletic because they independently (in parallel) lost the ability to fly. * Animals with a
dorsal fin A dorsal fin is a fin A fin is a thin component or appendage attached to a larger body or structure. Fins typically function as foils that produce lift or thrust Thrust is a reaction (physics), reaction force (physics), force described ...
are not paraphyletic, even though their last common ancestor may have had such a fin, because the
Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles and the Age of Conifers, is the second-to-last era An era is a span of time defined for the purposes of chronology or historiography, as in the regnal eras in the history of a given monarchy ...
ancestors of porpoises did not have such a fin, whereas pre-Mesozoic fish did have one. *
Quadrupedal The zebra is a quadruped. Quadrupedalism is a form of terrestrial locomotion where a tetrapod Tetrapods (; from Greek 'four' and 'foot') are four-limbed animals constituting the superclass Tetrapoda . It includes extant and extinct amph ...
archosaur Archosauria ("ruling reptiles") is a clade A clade (), also known as a monophyletic group or natural group, is a group of organism In biology, an organism () is any organic, life, living system that functions as an individual entity. ...
s are not a paraphyletic group.
Bipedal Bipedalism is a form of terrestrial locomotion Terrestrial locomotion has evolved Evolution is change in the heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from ...

Bipedal
dinosaurs like ''
Eoraptor ''Eoraptor'' () is a genus of small, lightly-built, basal saurischian dinosaur Dinosaurs are a diverse group of reptiles of the clade A clade (; from grc, , ''klados'', "branch"), also known as a monophyletic group or natural group, ...

Eoraptor
'', ancestral to quadrupedal ones, were descendants of the last common ancestor of quadrupedal dinosaurs and other quadrupedal archosaurs like the crocodilians.


Non-exhaustive list of paraphyletic groups

The following list recapitulates a number of paraphyletic groups proposed in the literature, and provides the corresponding monophyletic taxa.


Linguistics

The concept of paraphyly has also been applied to
historical linguistics Historical linguistics, also termed diachronic linguistics, is the scientific study of language change Language change is variation over time in a language A language is a structured system of communication used by humans, including s ...
, where the methods of
cladistics Cladistics (; ) is an approach to biological classification In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular ...

cladistics
have found some utility in comparing languages. For instance, the
Formosan languages The Formosan languages are the languages of the indigenous peoples of Taiwan, all of which are Austronesian. The Taiwanese indigenous peoples recognized by the government are about 2.3% of the island's population. However, only 35% speak their ...

Formosan languages
form a paraphyletic group of the
Austronesian languages The Austronesian languages (, , , ) are a language family A language family is a group of language A language is a structured system of communication used by humans, based on speech and gesture (spoken language), Signed language, sign ...
because they consist of the nine branches of the Austronesian family that are not
Malayo-Polynesian The Malayo-Polynesian languages are a subgroup of the Austronesian languages, with approximately 385.5 million speakers. The Malayo-Polynesian languages are spoken by the Austronesian peoples outside of Taiwan, in the island nations of Southeast A ...
and are restricted to the island of
Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia East Asia is the eastern region of Asia Asia () is Earth's largest and most populous continent, located primarily in the Eastern Hemisphere, Eastern and N ...

Taiwan
.Greenhill, Simon J. and Russell D. Gray. (2009.) "Austronesian Language and Phylogenies: Myths and Misconceptions About Bayesian Computational Methods," in ''Austronesian Historical Linguistics and Culture History: a Festschrift for Robert Blust'', edited by Alexander Adelaar and Andrew Pawley. Canberra: Pacific Linguistics, Research School of Pacific and Asian Studies, The
Australian National University The Australian National University (ANU) is a national research university located in Canberra Canberra ( ) is the capital city of Australia. Founded following the Federation of Australia, federation of the colonies of Australia as t ...
.


See also

*
Glossary of scientific naming This is a list of terms and symbols used in scientific names for organisms, and in describing the names. For proper parts of the names themselves, see List of Latin and Greek words commonly used in systematic names. Note that many of the abbreviati ...


Notes


References


Bibliography

*
Paraphyletic groups as natural units of biological classification


External links

* {{Phylogenetics Phylogenetics Paraphyletic groups