Talk:Crown group

message: Is it not the case that biologists sometimes use the term "crown group" or "the crown group" to refer to the crown group of all living organisms?  If so, the article does not seem to mention it.  -- Dominus (talk) 17:40, 6 October 2008 (UTC)
replies: text: Read the article before commenting on it! In discussing birds, for example, writing "crown-group birds" is essential if, for example, one wants to exclude animals like Archaeopteryx. Peter Brown (talk) 16:38, 15 April 2013 (UTC)
thread_title:  "The" crown group 

message: I check pages listed in :Category:Pages with incorrect ref formatting to try to fix reference errors. One of the things I do is look for content for orphaned references in wikilinked articles. I have found content for some of :Crown group's orphans, the problem is that I found more than one version. I can't determine which (if any) is correct for this article, so I am asking for a sentient editor to look it over and copy the correct ref content into this article.
Reference named "Budd2000":
From Amiskwia: 
From Cambrian explosion: 
I apologize if any of the above are effectively identical; I am just a simple computer program, so I can't determine whether minor differences are significant or not. AnomieBOT⚡ 19:28, 25 October 2008 (UTC)
thread_title:  Orphaned references in [[:Crown group]] 

message: :Part of the problem is that "sister group" is ambiguous.  In a strict sense, clade F is a sister of clade G if and only if (a) neither includes the other and (b) every clade that is larger than F and includes F also includes G. Condition (b) is so strong, though, that we can seldom be at all confident that any two groups are sisters in this sense.  We cannot definitively rule out on morphological grounds the possibility that there is an unknown species S, in neither F nor G, such that some clade contains F and S but not G.
 
:In concrete applications, the term is more widely used.  Percy M. Butler has written that, if docodont dentition is similar in certain respects to that of Kuehneotherium and Woutersia, then the docodonts must be considered a sister-group of the Kueneotheriidae.  Surely, he meant only to rule out that any known clade includes the Docodonta and not the Kueneotheriidae.  He was not predicting that such a clade will never need to be defined.
:The reference is 
:Sisters in the narrow sense can be identified only by molecular sequencing, which requires that both candidates be extant.  This is irrelevant in the context of the present discussion.
:Peter M. Brown (talk) 17:21, 2 January 2012 (UTC)
replies: text: Since the phylogenetic nomenclature specifically refers to a phylogenetic tree, I think we can rather safely assume that there's a "secret" condition built into the definition, i.e. restricted to groups included in this study. Often, a second condition, that of having extant members seems to be assumed, again without specifically stating it (birds-crocodiles being the standard point in question). The third (and also usually not communicated condition) is of course known. On a very fine scale (i.e. species scale), even DNA sequencing won't help you if you if the sister group isn't known and you don't have a sample to work from. Another thing is that when we are down to the species scale, paraphyly starts to become an acute problem and the phylogenetic conditions of bifurcating branches and ancestral species going extinct are not met any more. Petter Bøckman (talk) 18:25, 2 January 2012 (UTC)
replies: text: Absolutely! All definitions only make sense in relation to a specified tree. Peter coxhead (talk) 01:54, 3 January 2012 (UTC)
replies: text: We probably can't say that enough times when dealing with these kinds of articles. Also, there probably should be an article on sister groups. Petter Bøckman (talk) 07:35, 3 January 2012 (UTC)
replies: text: Edit: Sister group is now up. Petter Bøckman (talk) 08:01, 3 January 2012 (UTC)

text: Good point! Petter Bøckman (talk) 13:20, 4 January 2012 (UTC)
thread_title: Sister group

message: A source has been asked for regarding the "common" definition of birds and mammals. What will be adequate sources for the common definition? The best I can come up with is the definitions given in non-specialist woks like encyclopedias. Here's what UXL Encyclopedia of Science (2002) has to say on birds:
Birds are warm-blooded vertebrate (having a backbone) animals whose bodies are covered with feathers and whose forelimbs are modified into wings.
This definition is obviously trait-based. Would this be suitable? Petter Bøckman (talk) 12:41, 13 August 2012 (UTC)
replies: text: Oh, good enough, though early members of Aves probably weren't warm-blooded. Peter M. Brown (talk) 17:27, 13 August 2012 (UTC)
replies: text: I suppose that depends on how you define "warm-blooded". The dino-people are adamant that the whole Archosauria had some degree temperature control. The coelosaurids appear to have been fairly warm blooded. Whether they all were running at an avian 42 degrees centigrade is anyones guess, but it seems reasonable to expect they at least had a constant temperature in the 30ies, probably in the upper range. Research on growth in Archaeopteryx indicate they grew slowly (reptilian style), so the full modern 42 degree temperature was probably beyond them. We do on the other hand include the spiny ant eater in the warmblooded cohorts, and it has a temperature fluctuation around 31 degrees. I'm fairly sure Archaeopteryx could beat that.
I'll source the "common definition" at once. Petter Bøckman (talk) 07:31, 14 August 2012 (UTC)
thread_title: The "common definition"

message: This sentence has an "unsourced" tag to it. Exactly what is unsourced here?
This has led to a confusion over the exact extension of well known taxa like birds and mammals.Laurin, M. & Anderson, J.S. (2004): Meaning of the Name Tetrapoda in the Scientific Literature: An Exchange. Systematic Biology no 53 (vol 1): pp 68-80. 
Petter Bøckman (talk) 10:41, 20 August 2012 (UTC)
replies: text: It is claimed that the use of the prefix "stem" to indicate a stem group, e.g. "Stem-Aves" or "Stem-Arthropoda", has led to a confusion. Neither source uses or discusses "stem" as a prefix, however, except in the context "stem-based", which is not the usage under discussion. Peter M. Brown (talk) 14:08, 20 August 2012 (UTC)

text: Ah, I think I know what has happened. When I wrote that section, it was about the use of crown groups. Somehow it has been moved and the term "crown" has been replaced with "stem". I'll reword it and you can see if it makes more sense now. Petter Bøckman (talk) 14:28, 20 August 2012 (UTC)
thread_title: Unsourced statement

message: I see you have cleaned up the article and removed some not much used terminology. Would it be an idea to have a sentence devoted to these terms, like "Further elaboration on the concept like zygon-, plesion- and scion groups have been proposed, but have not seen much use.", or something to that effect? Petter Bøckman (talk) 07:28, 6 September 2012 (UTC)
replies: text: The plesion does have sufficient notability to be discussed somewhere, though not in a section entitled " Other groups under the crown group concept". Perhaps it should have an article of its own. If you can source the statement you suggest by specifying who proposed scion and zygon groups, by all means include it. Peter M. Brown (talk) 13:36, 6 September 2012 (UTC)
thread_title: Removed sections

message: I get the feeling that these clearly exist, though usually unacknowledged b/c they are seen as undesirable from a phylognetic viewpoint, yet are useful from a taxonomic one for organizing the organisms in question. I've run in such a case in the latest classification of Apocynaceae (see my sandbox for details), but I'm not sure how to insert a mention of this in the article, which focuses strongly on the existence of stem groups where all the taxa forming the stem are extinct. Circéus (talk) 21:50, 27 February 2014 (UTC)
thread_title:  Stem group in extant taxon 

message: This article not only talks about "crown groups" but also of many other derived concepts such as "stem-groups", "basal groups", "zygon", "plesion", etc. They are all collectively named "accessory groups" in Aubert 2015. A formal analysis of phylogenetic terminology: Towards a reconsideration of the current paradigm in systematics. Phytoneuron 2015-66:1–54.
Shouldn't we rename this article so that the title is more relevant? BernZ (talk) 11:21, 12 December 2015 (UTC)
replies: text: I think there's a general problem with articles about phylogenetics/cladistics terminology. On the one hand, I don't think it really works to have separate articles on each of a set of closely related terms, as we have for Monophyly, Paraphyly and Polyphyly, for example, since this inevitably involves re-explaining the same things, potentially inconsistently. On the other hand, the individual terms have much better-known names than any collective name that fits. Although "accessory group" might be a more accurate article title, it's not exactly a "common name" as per WP:AT. I'm not sure what the answer is. I'd like to see a broader discussion of this issue. Peter coxhead (talk) 13:27, 13 December 2015 (UTC)
thread_title:  Misnamed article? 

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thread_title:  External links modified 

message: The introduction states that a crown group is one way to define a clade. Does this mean that clade and crown group are synonymous? The other way I can understand the lead is that a crown group is one kind of clade; but it remains unclear to me what would be an example of a clade that is not a crown group. Kent G. Budge (talk) 16:06, 8 July 2022 (UTC)
replies: text: It is my understanding that crown groups are specifically in regards to living species (in that it contains all of the extant/living members of the group, plus any extinct species that share the common ancestor). If a clade is entirely composed of extinct species, then it would not be called a crown group. So yes, a crown group is a type of clade, but they are non synonymous. Cougroyalty (talk) 17:11, 8 July 2022 (UTC)
replies: text: Thanks. That makes sense. Let's find a reliable source and put it in the article. --Kent G. Budge (talk) 17:16, 8 July 2022 (UTC)
replies: text: I think this is yet another example of a term that biologists often use differently while assuming there's a single common definition. See, for example, the last sentence of the section "Contents of the crown group". In a way, it's the complementary concept "stem group" that is more distinct – it's a way of defining and talking about a group that is not a clade. The real contrast is perhaps between the "crown clade" and the "total clade". This article begins with a sharper definition than my understanding of Hennig's original concept, and has some useful discussion points. Peter coxhead (talk) 13:35, 9 July 2022 (UTC)
thread_title:  Crown group versus clade 

message: This concept which abrupt rears its head in the "Palaeontological significance" is completely unexplained. A quick google search suggest this is not a broadly or commonly used term and even so, it clearly needs an explanation here as a layman's understanding of the basic concepts provides no help whatsoever understanding what it actually being said. Circéus (talk) 16:02, 14 October 2023 (UTC)
thread_title:  "phylogenetic telescoping" 

message: Both cladograms containing Aves show Aves as being in the place of Avialae, but when you click on the Aves links, they lead to a Wikipedia page defining Aves as being synonymous with Neornithes, despite said cladograms showing Neornithes as being inside of Aves.  I know that Aves has a disputed definition, but this seems like it would be extremely confusing to people unfamiliar with the topic, so I suggest that Aves should just be replaced with Avialae on both cladograms, and the links should lead to the Avialae page as well.
Also, the link in the caption of the first diagram saying "total group or pan-group" does nothing when I click on it.  Is the link broken, or is it just leading me back to the same page, as it seems like it would?  Why would there be a link to the page I'm already on?  Either way, I feel like it should be fixed. Thunderhawk256 (talk) 14:19, 11 April 2024 (UTC)
thread_title:  Diagram Links