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In biological taxonomy, a grouping of organisms is said to be paraphyletic if it does not represent all the descendants of some common ancestor. Most schools of taxonomy advocate that groups reflect phylogeny instead, and so view the existence of paraphyletic groups in a classification as errors. Taxonomic groups that do share a common ancestor are called monophyletic.

I'm a little confused here. The last sentence seems to indicate monophyletic means "all share a common ancestor", but the first sentence seems to indicate that paraphyletic means "does not provide complete coverage of the set of all descendants of some common ancestor". Is the first sentence instead intended to mean "contains members which may not all share the same set of ancestors"? Chas zzz brown 11:21 Dec 6, 2002 (UTC)

Thanks for the clarification, Steve Chas zzz brown 07:51 Feb 12, 2003 (UTC)

This does not necessarily mean that older biologists meant to create them; more often it was just that they needed to have some taxonomy in order to organize the huge number of species in a way they could understand, and without modern scientific evidence, guesswork was required that later turned out to be wrong.

I don't think this is true. Older taxonomies in many cases contain groups which are obviously intended to be paraphyletic. For instance, it has long been understood that mammals and birds evolved from reptiles (making the reptiles paraphyletic), but only recently has the class Reptilia been objected to on these grounds.

I really did not like that paragraph but wondered how best to change it. The most charitable interpretation of it seems to be at the genus level, where many paraphyletic genera have been erected because of they have been classified by overall similarity, which necessarily includes plesiomorphies, rather than by recognizing apomorphies by a cladistic analysis.

In phylogenetics, a grouping of organisms is said to be paraphyletic if all the members of the group have a common ancestor but the group does not include all the descendants of the common ancestor.

This is a tautology, any group of organisms is vacuously paraphyletic as defined here (let A be a common ancestor, let B be a parent of A, and let C be a sibling of A sharing parent B. Then C is not in the group, but it is the descendent of a common ancestor of the group, namely B). It should probably read "In phylogenetics, a grouping of organisms is said to be paraphyletic if the group does not include all of the descendents of the most recent common ancestor of all the members." I would change the page but I don't want to introduce an error, in case this isn't what the author intended to say. --A5 00:25, 26 Mar 2004 (UTC)

Another confused reader here... what does this mean?

Groups which include all the descendants of a common ancestor are commonly termed monophyletic, although this term is sometimes taken to apply to paraphyletic groups as well, in which case they are called holophyletic.

The primary culprit is the unclear "they", but the whole sentence is as clear as mud. Should probably be broken into two carefully worded sentences. Perhaps it would be better to have three parallel definitions: paraphyletic, monophyletic, holophyletic, to make it clearer exactly how they're used and what the distinctions are. I'm not a science dunce, I promise! This just needs refining. [[User:CatherineMunro|Catherine\^talk]] 07:06, 28 Nov 2004 (UTC)

A5 is exactly right, the definition as it was made no sense:

In phylogenetics, a grouping of organisms is said to be paraphyletic if all the members of the group have a common ancestor but the group does not include all the descendants of the common ancestor.

To see why this makes no sense, consider this: some amphibian is a common ancestor for all members of Mammalia. Yet all reptiles are also descendants of this same amphibian, and therefore by this definition Mammalia is paraphyletic.

You can generalize the conclusion to any group, which shows the definition is obviously broken.

I'm not a biologist, but I would rather leave a definition that I believe to be correct than one I know to be wrong. (You know, Be bold). So I've made the change, feel free to comment. --Saforrest 00:35, Jan 28, 2005 (UTC)

the class Reptilia as traditionally defined is paraphyletic because that class does not include birds (class Aves), which are descended from reptiles.

This is not a good example since birds almost certainly came from warm-blooded dinosaurs, not reptiles. I haven’t changed it because a better example should be substituted. But someone should. David Shear, Oct 14, 2005.

Two points to this; classic Reptilia includes dinosaurs; how to reorganise the major subdivisions of Amniota is not something there is a clear agreement on, but promoting Dinosauria to the same level as Reptilia, Aves and Mammalia is not the only possibility. Second point, how about using apes as the example? - humans are descended from apes but not included amongst them. Of course, this could be on the creationist-avoidance principle Richard Gadsden 00:41, 23 September 2006 (UTC)[reply]

Birds are now considered to be part of Reptilia, I would delete that diagram if I knew how. —Preceding unsigned comment added by Tylersquare (talk • contribs) 18:51, 25 November 2008 (UTC)[reply]

Paraphyly in linguistics?

I have removed the paragraph "The term paraphyletic is also used in historical linguistics, with similar meaning. For example, there are scholars who believe that centum and satem are paraphyletic groups of Indo-European languages". It is so because these terms are not believed (by some linguists) to be paraphyletic but polyphyletic rather. See Talk:Indo-European languages for details. --Grzegorj 16:55, 23 August 2005 (UTC)[reply]

The term is used in several Wiki articles on various languages, however.17:51, 29 November 2007 (UTC) —Preceding unsigned comment added by Adresia (talk • contribs)

Classification Logic

I'm quite curious: if one has to strictly apply the paraphyletic rule to name groups, there would logically be but one group, that is the group of the first species originated on Earth: such a group, containing the single species from which all others have originated, must contain all such species. So where is the limit really put? It's not really discussed in the article... Gbnogkfs 25 May 2006, 21:34 (UTC)

Could you be a little bit more specific? What is the paraphyletic rule? I know but one: do not include groups proven to be paraphyletic in the classification. Alexei Kouprianov 10:36, 26 May 2006 (UTC)[reply]

You say it's better not to include paraphyletic groups in classification. The problem is that you can't apply this rule to every group, except if you want to create only one group, which is of course against the scope of a classification in the first place.

To make an example: let's consider the Mammal and Reptile classes. Let's consider the most recent ancestor to all mammal and reptiles: in which class would you include it? If you put it in the Mammal class, then the mammal class is paraphyletic; if you put it in the Reptile class, then the reptile class is paraphyletic; if you put it in a third class, then that class is paraphyletic.

The result is that if you want to create only non-paraphyletic groups, you are forced to put mammals, reptiles and their common ancestor into the same class.

Eventually, repeating this process, all the living beings have to be put in the same class.

There is common agreement even among anti-paraphyleticists on the existance of more than one class: where do you put a limit in the refusal of paraphyletic groups? Gbnogkfs 26 May 2006, 22:18 (UTC)

No, you've got it all wrong. Just as the authors of the Wiki-article. The taxa do not include ancestors. Even the monophyletic ones. They include all (in case they are monophyletic) or some (in case they are non-monophyletic, i.e. para- and polyphyletic) terminal taxa (indivisible units of the analysis) believed to be descendants of the hypothetical most recent common ancestor. This comes from a logical premise that only sister-group relationships (and not the ancestor-descendant relationships) can be proven. Note, please, that I am just repeating an argument from the thirty-year old debates. It is all in the 1970--1980s. No matter for a discussion on this point any longer. Alexei Kouprianov 22:25, 26 May 2006 (UTC)[reply]

I can't really get the whole of your answer, but then if the article is wrong, why doesn't anybody amend it? Gbnogkfs 26 May 2006, 23:33 (UTC)

Well, I just did. I am sorry I was too technical (I was trained as a taxonomist). I hope that my reformulation of the article makes this less esoteric. Alexei Kouprianov 10:44, 27 May 2006 (UTC)[reply]

So taxa are used only for "clades", with the exclusion of common ancestors: that is, for exemple, that the most common ancestor of Mammalia and Reptilia (and all of the ancestors of this last, in fact) is not included in any class (while being, for exemple, a member of the chordates). That's interesting: it was not clear at all! Gbnogkfs 27 may 2006, 12:43 (UTC)

That's even more interesting. None of the still existing or fossil species could be unambiguously identified in principle as the most recent common ancestor of mammals, reptiles, mammals+reptiles, as well as of any other group. Hence, there is no real problem of classifying the ancestor. The real ancestor when discovered could pose a major problem, but no one is able to prove that this or that particular fossil really is the ancestor. The logically correct way to deal with fossils is to regard them as sisters (not mothers) of other fossil or recent groups. Alexei Kouprianov 13:57, 27 May 2006 (UTC)[reply]

Indeed: a very sperimental approach. Thanks for the biology lessons :) Gbnogkfs 27 may 2006, 20:42 (UTC)

Definition re-broken

I happened upon this page again and saw that the definition had been re-broken since User:Saforrest's fix long ago (and other intervening fixes by other users). It said: "In phylogenetics, a group of organisms is said to be paraphyletic (Greek para = near and phyle = race) if the organisms have the same common ancestor, and the group does not contain all the descendants of this ancestor." I changed it to: "In phylogenetics, a group of organisms is said to be paraphyletic (Greek para = near and phyle = race) if the group contains its most recent common ancestor, but does not contain all the descendants of that ancestor." The definition was most recently broken by User:Pgan002. Please take care when rewording the definition. Roughly, all organisms on Earth have a common ancestor, and no non-trivial group of organisms contains all of the descendants of this ancestor. I also fixed the reference to Polyphyly. A5 16:17, 19 August 2006 (UTC)[reply]

Logical Inconsistencies

It was shown, however, that the inclusion of ancestors in the classification leads to unavoidable logical inconsistencies

Alexei, you would have to concede that the above statement is a matter of debate even today. I think the article should be edited to highlight some of the aspects of the differing approaches. Ordinary Person 13:13, 30 November 2006 (UTC)[reply]

Well, I said everything I could in my posts from May 27. If one can prove that exactly this or that fossil bone is the actual ancestor of some recent group it's fine with me. I only doubt it is in principle possible. As soon as we include ancestors in the scheme, some taxa turn to be inherently paraphyletic. If the whole scheme was invented to avoid paraphyly, why let it back in? Alexei Kouprianov 14:14, 30 November 2006 (UTC)[reply]

That's a reasonable point. I wonder if some of this discussion can be worked into the article without dewikifying it. Ordinary Person 15:02, 30 November 2006 (UTC)[reply]

Well, it was. The problem is that the definition in the very first paragraph of the article is not under my full control. I am mostly active in Russian Wiki and I come here from time to time just to make few corrections here and there. Meanwhile someone usually replaces a more theoretically rigorous but somewhat obscure definition with something more agreeable from the common sense perspective. The situation is getting more complicated because an average zoologist or botanist usualy does not pay attention to such subtlities, and, especially in the textbooks, one may find rather commonsensical definitions for mono-, poly-, and paraphyly, which are a bit far from the rigorous logic of original theories back in the 1980s, when the cladistic swords weren't yet rusty being stained with blood of the pheneticists and evolutionary taxonomists... I'll try to come back in a couple of days to try and reformulate the definition agaun but I can not guarantee that it will stay for ever. (Note: I am not complaining! It is just the way the things are...) Alexei Kouprianov 18:15, 30 November 2006 (UTC)[reply]

"Paraphyletic to"

We should define the common usage "paraphyletic to", as in "reptiles are paraphyletic to birds". It is arguably clearer (especially for a general audience) to say "reptiles are paraphyletic, because they exclude birds" which is almost as concise, but the "paraphyletic to" wording is pretty common and baffling if you don't know the shorthand. The only thing holding me back is that the dictionaries and glossaries I consulted only defined paraphyletic, not the usage with "to". So I don't have a source. Kingdon (talk) 19:50, 14 March 2008 (UTC)[reply]

Paraphyly, a concept not that difficult

The concept of paraphyly and paraphyletic taxa is realy quite simple. Best to start off putting cladobabble aside, to borrow Alan Kashlov's term. Cladistics may give a good picture of evolutionary progression and continuum, but it does not ordinarily give the best picure of how small groups fit within larger groups, such as how genera fit into families and families into orders.

A paraphyletic group or taxon is simply one that does not include all its descendants, as generally stated. Examples of paraphyleitc taxa are the Nautiloidea which do not include the Ammonoidea and Coleoidea to which they gave rise; Synapsid Pelycosuaria which does not include descentant mammalia, and Dinosauria in the normal sense that excludes the derived birds (Aves)

All taxa to be valid must be monophyletic, whether one is talking from a taxonomic or cladistic perspective. In other words it must have a single common ancestor, at least generically. All valid paraphyletic taxa are also monophyletic. The terms are not muturally exclusive. One, monophyly referes to ancestory, the other, paraphyly refers to partial inclusion. I suppose a group that included all the descendants from the most recent common ancestor would be holophyletic. Mammals and birds are holophyletic because there are no exluded descendants, none having yet evolved.

Polyphyletic taxa are another matter, in some ways the opposite of monophyletic. A polyphyletic taxon is one with more than one most recent common ancestor, united by some convergent feature. The bird-mammal example is a fair one. Although both are warm blooded, one, birds, has its orgin in the dinosaurs, the other, mammals in the cynodonts. A better example is the Nautilida and Ammonoidea, both coiled ectocochliate cephalopods. A single taxon lumping the Nautilida and Ammonoidea exclusively would be polyphyletic, and invalidsince the Nautilida are derived from the Oncocerida and the Ammondea come from the Orthocerida. The Oncoceroda and Orthocerida are only remotely related nautiloid cephalopods just as birds and mammals are remotely related amniote tetrapods. Polyphyletic taxa, which are invalid, are the result of convergence that results in the appearance of being closely related.

Paraphyly is an important principle in taxonomy. It keeps taxa from becoming overly diffuse to the point of having little meaning. It allows derived taxa to be asigned rank equal to that of the ancestral taxon as in Class Aves being equal to Class Dinosauria or Class Ammoidea being equal to Class Nautiloidea. Otherwise there'd be a case of diminishing returns. Paraphyly also keeps taxa in conversationally reasonable units. When we speak of dinosaurs we shouldn't have to add, non-avian. They are after all, aren't they.

John McDonnell —Preceding unsigned comment added by J.H.McDonnell (talk • contribs) 01:28, 25 July 2008 (UTC)[reply]

The problem with this incomplete definition of paraphyly

The problem with the definition of paraphyly as stated in this article is that it is incomplete. Paraphyly also includes the groups of presently existing biological species of monophyletic groups (that is, holophyletic groups and paraphyletic groups as defined in this article) of biological species (for example humans and chimps or chimps and gorillas). Groups including ancestors are ambiguous per definition, since thing and kind (i.e., thing and its properties) are not synonymous (or equal). Things do have properties, but properties do not have things. It means that there are two kinds of monophyletic groups: holo- and paraphyletic groups. Cladistics does not understand this fact, whereas the Linnean classification system incorporates it. Mats, presently at 83.254.23.241 (talk) 09:02, 19 January 2009 (UTC)[reply]

Shouldn't Agnatha be polyphyletic?

"Agnatha, jawless fish. This group contains two significant animal groups, hagfish and lampreys. Their nearest common ancestor is the ancestor of all vertebrates, so Agnatha is paraphyletic."

compare to:

"A group that does not contain the most recent common ancestor of its members is said to be polyphyletic" and "group of organisms is said to be paraphyletic if the group contains its most recent common ancestor but does not contain all the descendants of that ancestor"

Unless hagfish or lampreys include the ancestor to all vertibrates then it can't be a paraphyletic group. If the common ancestor to all vertibrates is included in either hagfish or lampreys then the article should make this clear.

I'm not going to alter the article myself as this isn't my field and I don't know which case is the correct one.

-- Michael Mortimore —Preceding unsigned comment added by 82.32.248.147 (talk) 08:11, 27 March 2009 (UTC)[reply]

Eubacteria?

The article at Neomura shows that, according to Thomas Cavalier-Smith, the Eubacteria are paraphyletic (for example, bacteria such as Actinobacteria are more closely related to Neomura than they are to, say, Cyanobacteria). Should this be included? It seems significant 24.34.94.195 (talk) 01:53, 8 September 2009 (UTC)[reply]

Originator of term?

Wasn't the term introduced by P.D. Ashlock, entomologist at University of Kansas?

72.49.254.33 (talk) 12:00, 11 October 2009 (UTC)[reply]

It's possible. The earliest use of paraphyletic given by the OED is the appearance in the translation of Willi Hennig's 1965 paper in Annual Review of Entomology. Do you have evidence of an earlier use by Ashlock? --Danger (talk) 18:13, 11 October 2009 (UTC)[reply]

Gobbledeygook

"Before that period the distinction between mono- and polyphyletic groups was based on the inclusion or exclusion of the most recent common ancestor. It was shown, however, that the inclusion of ancestors in the classification leads to unavoidable logical inconsistencies, and, in some schools of taxonomy, the phylogenetic pattern is described exclusively in terms of nested patterns of the sister group relationships between the known representatives of taxa without referring to the ancestor-descendant relationships."

What logical inconsistencies? What schools of taxonomy? Do you mean most recent of last common ancestor? Just what do you mean? If you follow sister group it takes you to cladistics and there sister group is defined as part of a clade. Why is known emphasized? Really, this unreferenced passage says nothing comprehensible at all, and it would not help to throw in a reference, much less a whole book without page numbers, such as Simpson. Reference what? At this point I have to say, either do it right or do not meddle.Dave (talk) 15:07, 24 January 2010 (UTC)[reply]

Insertion of linguistics by tim

Hello Tim. I got on this article from linguistics myself, as I saw linguistics terms being tossed casually around there. Historical linguistics is using the family tree model, which naturally developed into phylogeny. However, biological classification is in a state of flux so we want to be careful how far to extend the analogy. But I found that the biological articles couldn't even be understood. As to your changes, they are not the best changes to make. Yes, something on linguistics should be in there. You are getting a bit ahead of me. I was going to do it, but first things first. No, it does not belong at the top of the page. This is primarily a biological not a linguistics article. Moreover, you're not saying anything about it. We need to define what it means when paraphyly is applied to linguistics. Merely quoting another WP article I believe is against the policy. WP is NOT a source for WP articles unless they are about WP. Now, we are not lacking in linguistics in these cladistics articles. Check Cladistics. In each case the linguistics is mentioned under non-biological uses at the bottom. So, I'm moving you to the bottom. Moreover, since you have said nothing, there is nothing to move. So, I;m taking out your quote of the WP article. We need a place holder, however, so I'm putting in a single introductory statement. Anyone including you can expand it, but I have to warn you it is a steep subject so if you are not prepared perhaps you should wait for someone else. For myself I thought, first let's get the biology clear and then we can take on the linguistics. Finally, you took the picture from the top. Unless you have a better biological picture I am putting it back on top. Thanks for your interest in the topic.Dave (talk) 13:05, 25 January 2010 (UTC)[reply]

I added a reference to the linguistics section. I will say this, though, in my personal experience, most historical linguists would not use the term. Really, only the very small subset who also use computational phylogenetic methods would ever use the term. --Limetom 03:05, 18 April 2010 (UTC)[reply]

Logical inconsistency

The version as of 05:08, 17 October 2010 contains an important inconsistency. The first paragraph said:

"A group of taxa is said to be paraphyletic if the group contains its last common ancestor but does not contain all the descendants of that ancestor."

Later the definition was given as:

"A paraphyletic group is a monophyletic group from which one or more of the clades is excluded to form a separate group (as in the paradigmatic example of reptiles and birds, shown in the picture)."

The first definition is not correct; if we take a monophyletic group of classified entities and randomly remove some of them we don't necessarily get a paraphyletic group. The second definition is correct for current usage: the missing members must form monophyletic groups -- actually I think generally the term is only used when one such group is missing, i.e. a 'crown and stem' classification. I have edited the article to ensure consistency with the later definition. Peter coxhead (talk) 10:45, 5 December 2010 (UTC)[reply]

Reptilia has two groups missing (Aves and Mammalia). Your changed wording still covers it, though.--Curtis Clark (talk) 17:13, 5 December 2010 (UTC)[reply]

Thanks, good example (depending on how you define the full Reptilia clade). I think that paraphyly is usually a term employed with one missing monophyletic group, but clearly there can be more than one (i.e. 'stem and crowns' rather than 'stem and crown'). My definition in the opening sentence was still not quite right though: it has to be "if the group consists of all the descendants of a possibly hypothetical closest common ancestor minus ...". I think that the following are the completely correct definitions of the three kinds of classification as currently used:

Monophyly = all descendants of the closest common ancestor of the group's members (plus the closest common ancestor if ancestors are being included in the classification).
Paraphyly = a monophyly minus one or more sub-monophylies
Polyphyly = everything else.

In particular I can't find a neat form of words to define polyphyly other than as "what is left". The definitions I've seen are usually also applicable to paraphylies. Is there one? Peter coxhead (talk) 15:15, 6 December 2010 (UTC)[reply]

The sentence "Reptiles would be monophyletic if they were defined to include Mammalia and Aves" is confusing in light of the accompanying picture. It doesn't show Mammalia as a descendant of the node Reptilia. According to the picture, Amniota would have to be thrown in as well, so I am adding a brief explanation.

Why have three articles?

Please see Talk:Monophyly#Why_have_three_articles where I have asked why there should be separate articles on monophyly, paraphyly and polyphyly. Please leave comments there. Peter coxhead (talk) 15:57, 6 December 2010 (UTC)[reply]

Vertebrates derived from invertebrates

The article was saying : "Invertebrates are defined as all animals other than vertebrates, although vertebrates are derived from this larger group". I removed "larger", because it implies that vertebrates are a subset of invertebrates.Stefan Udrea (talk) 10:37, 15 January 2011 (UTC) I mean, I can buy that birds are some kind of reptiles, but I can't buy that vertebrates are invertebrates, it's a glaring oxymoron.Stefan Udrea (talk) 11:07, 15 January 2011 (UTC)[reply]

@@ Line 167: / Line 167: @@
 :::* Polyphyly = everything else.
 ::: In particular I can't find a neat form of words to define polyphyly other than as "what is left". The definitions I've seen are usually also applicable to paraphylies. Is there one? [[User:Peter coxhead|Peter coxhead]] ([[User talk:Peter coxhead|talk]]) 15:15, 6 December 2010 (UTC)
+The sentence "Reptiles would be monophyletic if they were defined to include Mammalia and Aves" is confusing in light of the accompanying picture.  It doesn't show Mammalia as a descendant of the node Reptilia.  According to the picture, Amniota would have to be thrown in as well, so I am adding a brief explanation.
 == Why have three articles? ==