Arthropods Template‑class

This template is within the scope of WikiProject Arthropods, a collaborative effort to improve the coverage of arthropods on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.ArthropodsWikipedia:WikiProject ArthropodsTemplate:WikiProject ArthropodsArthropods articles Template This template does not require a rating on Wikipedia's content assessment scale.

There is an excellent likelihood that any newly published arthropod phylogeny will change -sometimes radically- certain groupings with varying degrees of support for each grouping (ML, Bayesian, etc) ranging from strong to insignificant. Rather than heedlessly cater to the phylogeny du jour, I argue this template should show some conservatism to better withstand future changes, and of course, facilitate reader navigation (the ultimate purpose of any navbox). In particular, the recent template changes to myriapods group Centipedes with Millipedes, a grouping based on a weakly supported tree in Miyazawa et al. (2014) who state that only the position of Symphyla is well-resolved, while "relationships among the remaining three classes could not be resolved due to low node support." I realize there is always room for debate about which tree or classification system to use, but urge that only well-supported schemes with strong, secondary support (e.g. multiple confirmation) be used when possible. I'm less familiar with recent advancements in pancrustacean classification, but my sentiments remain the same. If there is significant disagreement between multiple, well-supported trees, then perhaps it would prudent to eschew the hierarchical scheme and simply list descendent taxa (e.g. simply list all 4 myriapod classes unsorted, as was previously the case). FUTON bias and recentism bias should also be kept in mind.--Animalparty-- (talk) 21:34, 8 August 2014 (UTC)Reply[reply]

Accoring to this review by Edgecombe et al. 2014 the consensus about crustacean phylogeny is close to the results of Oakley et al. 2013 (the source currently cited by the template), with the exceptions that there is no consenus for Thecostraca being closer to Copepoda than to Malacostraca, no consenus for a sister group relationship between Cephalocarida and Branchiopoda (because there is too little research about the relationships of Cephalocarida) and no consenus for a sister group relationship between Mystacocarida and Ichthyostraca sensu stricto (though I haven't seen any research contradicting it). The review also says that Pycogonida is likely sister to Euchelicerata.

For Hexapoda, the review by Kjer et al. 2016 says that the results of Sasaki et al 2013 (the source currently cited by the template) have not been subsequently corroborated. The review also says that Misof et al. 2014 is close to the current consensus but implies that there is not a strong consensus about the relationships among the four classes. Lophotrochozoa (talk) 20:19, 21 January 2017 (UTC)Reply[reply]

I'm afraid the caution recommended way back when was justified. The "Pancrustacea" is not a good taxon, and nor are several of the others associated with it. We should either simplify the list so that it's better future-proofed, or choose a newer source to provide some slightly more plausible tree-structure. Chiswick Chap (talk) 15:17, 29 November 2023 (UTC)Reply[reply]

@Chiswick Chap: Can I ask what source(s) suggest that "Pancrustacea" is not a good taxon? Maybe I'm not looking for them in the right places, but a lot of the recent articles I've seen seem to confirm Pancrustacea or assume it's a valid clade. Monster Iestyn (talk) 20:07, 1 December 2023 (UTC)Reply[reply]

A few things.

A minor thing is that "Pan-X" normally means "The clade of all of X including its stem group", but PC doesn't. Minor.

A bigger thing is that as Pancrustacea documents, since 2005 there have been at least 8 different interpretations of the group, so that freezing any one of them into a template means a) guessing which one to use b) implying "in Wikipedia's voice" that we know that that one is correct, and c) reconstructing the template every few years, not ideal to say the least in any of these three ways.

A third thing can be seen over at Arthropod, which gives the following charming interpretation of the phylogeny:

Given that the Hexapods emerged from deep within the Crustacea, that's not ideal either. Chiswick Chap (talk) 08:48, 2 December 2023 (UTC)Reply[reply]

@Chiswick Chap: I see, thanks for explaining.

The "Pan-" name issue I understand, though does that mean Panarthropoda is also problematic for including extant relatives of arthropods?

As for the second point... from what I understood it doesn't seem to be disputed that hexapods are derived from crustaceans at least, but I can see that how the crustaceans are related to each other is still up in the air. For instance a study published a few months ago (Bernot et al. (2023)) apparently rejects Multicrustacea (which is used in this template...). But by far the general concept of "Pancrustacea" itself (or whatever name would be better for it... Tetraconata?) is generally considered monophyletic. So I wonder if the template should be neutral to these studies, keeping Pancrustacea but not Oligostraca, Multicrustacea or Allotriocarida or any supra-class group except Hexapoda (so just crustacean classes + Hexapoda classes)?

That might work. My view is that templates, since we don't really ever seem to source them, should be as neutral as possible about anything even vaguely controversial. Cladograms with sources and commentary explaining how hypothetical they are, are a different matter. Chiswick Chap (talk) 13:53, 2 December 2023 (UTC)Reply[reply]

@Chiswick Chap  Done I have now updated the template accordingly. It now displays Pancrustacea again, but divides the classes into just "Crustacea" and Hexapoda. Monster Iestyn (talk) 15:14, 2 December 2023 (UTC)Reply[reply]

As for the last point ...that cladogram's sourcing actually seems to be suspect. That particular piece of the cladogram you pasted here is at least probably taken from the cited 2008 article (see figure 3), but some of the rest of that cladogram is not. It doesn't use Tactopoda (it gives a polytomy for the members of Panarthropoda instead), Lorcifera is not included in Scalidophora (unlike in the Arthropod article's cladogram), and Chaetognatha isn't even mentioned in the article. Monster Iestyn (talk) 13:49, 2 December 2023 (UTC)Reply[reply]

On the issue of Pancrustacea (and Panarthropoda), the problems with the names are discussed in detail by Haug & Haug (2015). Panarthropoda was proposed for the group containing Crustacea and Hexapoda (as sister taxa), so the current concept is quite different. As mentioned above, the concept of pan- groups are widely used for crown and total groups and for Pancrustacea there is the unusual feature that it doesn't include the taxon without the pan- prefix (i.e. Crustacea). However, these objections seems a minority view and Pancrustacea is widely used. On the other hand, WoRMS rejects Pancrustacea and Tetraconata and uses Crustacea "as the accepted name, being the oldest, most widely used and best established name"; Hexapoda is one of the classes within. Unfortunately the author of the comment isn't given, although Geoff Boxshall and Sammy De Grave are recent editors of the Allotriocarida and Hexapoda pages. The WoRMS approach seems to mirror that of Cetartiodactyla and Artiodactyla, where the older name in a new circumscription prevailed. —  Jts1882 | talk  10:06, 4 December 2023 (UTC)Reply[reply]

A short note, I would be very grateful if editors who know what is contained within this template could try and make it more readable. As a lay reader I can barely understand it at all. Some ways readability could be improved:

• Remove special formatting (vertical text, 'small' and 'large' text)
• Renaming the title to make it lay-reader friendly
• Giving more prominence to terms lay readers are familiar with

I am sure editors have put a lot of effort into this template, for which I thank them, but it could be improved. Cheers, --Tom (LT) (talk) 01:00, 14 January 2015 (UTC)Reply[reply]