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Concerning V's Deuterostome Heritage

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In the following article the authors describe Skeemella clavula from the Middle Cambrian Pierson Cove Formation of the Drum Mountains of Utah. It is similar to vetulicolians but also has arthropod characteristics, which they claim casts new doubt on the deuterostome affinity of vetulicolians.

Briggs, DE, Lieberman BS, Halgedahl SL & Jarrard RD (2005), A new metazoan from the Middle Cambrian of Utah and the nature of Vetulicolia. Palaeontology 48: 681-686--Likearock 14:37, 6 August 2006 (UTC)[reply]

Not according to: Dominguez, Patricio and Jeffries, Richard. (2003). Fossil evidence on the origin of appendicularians. Paper read at International Urochordate Meeting 2003. Abstract at [2] - URL retrieved June 22, 2006. The Mysterious El Willstro (talk) 06:36, 28 June 2012 (UTC)[reply]

Inclusion of Yunnanozoa

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Should we adjust the taxobox to mention the possible inclusion of the Yunnnanozoa, or no? Also, I thought they were related to hemichordates.--Mr Fink 17:37, 11 March 2007 (UTC)[reply]

The hypothesis is that Yunnanozoans are related to, not part of, Vetulicolia. In any case, the classifications remain speculative and contentious. -- Donald Albury 13:00, 18 March 2007 (UTC)[reply]
Indeed. I think this article may be best structured to first detail the 'facts' (i.e. their morphology, perhaps ecology) then the more dubious business of their taxonomy. I might get onto it it now... Martin (Smith609 – Talk) 19:17, 24 November 2008 (UTC)[reply]

Polished up References Section

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I made is consistent in format, not to mention consistently actually referenced in the Article. You're welcome. :-) Seriously, though, let's not let it get sloppy like it was again. The Mysterious El Willstro (talk) 06:38, 28 June 2012 (UTC)[reply]

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Inconsistent

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The article needs some serious editing, as it is highly inconsistent: the opening sentence and the Classification section describe Vetulicolia as phylum within Deuterostomia. The text contains various inconsistent statements about its classification. The latest paper (2024) is used to show a cladogram in which it is a paraphyletic stem group within Chordata. Peter coxhead (talk) 16:59, 29 September 2024 (UTC)[reply]

@Peter coxhead Agreed, and I'm happy to take this on as I've been working on some adjacent projects and have a bunch of relevant papers downloaded already. "Taxonomy and evolution", "Classification", and much of what is now the introduction need to be merged. Much of the rest of the introduction should go in an "Anatomy" or "Description" section, and the footnote should be given a short "Etymology" section as many other pages have. The introduction needs to concisely give the just the most up-to-date theory or theories.
The Saccorhytus stuff can be removed (except possibly for a brief note to keep anyone from re-adding it) as it's pretty solidly proven to be unreleated. The arthropod theory should be briefly explained without distracting from the main line of evidence associating Vetulicolians with Chordates.
I am thinking along these lines, using [brackets] for text without its own subheading:
  • [concise introduction] (revised 1st paragrah)
  • Etymology (basically that footnote)
  • Description (2nd paragraph of current introduction)
  • Ecology and lifestyle (as-is)
  • Taxonomy and evolution (see above)
    • [brief history of placement debate]
    • Phylogeny (cladogram and, if it seems like no well-sourced cladogram can cover everything, tree listing of all species)
I will also do more source and citation tidying, as I find the current text unreadable because the citations are so enormous (thank you to everyone who added detailed citations!) I tend to use the harvnb form, and will migrate to that unless someone will be really upset about it (I'm happy to do extra work to make it all consistent).
I'll give it a bit to see if anyone objects here and then follow the above plan. Alternate plans are welcome, and I don't feel possessive- I just like to write out a plan on the talk page before doing major rework if a page has a history of discussions.
Ixat totep (talk) 22:46, 10 November 2024 (UTC)[reply]
Some of the confusion seems to have been introduced when someone tried to remove the Linnaean terms in favor of cladistic ones, leading to over-use of "clade" for a group that is likely to be an evolutionary grade. Since Vetulicolians were discovered well into the cladistic era, I'm inclined to favor that terminology throughout, and only note the Linnaean ranks in the discussion of the history of classification and placement. "Vetulicolia" has been assigned various ranks, and trying to use those consistently in the text would be a hassle.
With that in mind, more neutral terms like "group" or "taxon" are probably best except when discussing theories that specifically advocate for clade or grade. As always, alternate proposals are welcome.
Ixat totep (talk) 23:01, 10 November 2024 (UTC)[reply]
@Ixat totep: all seems good to me. Peter coxhead (talk) 07:44, 11 November 2024 (UTC)[reply]
@Peter coxhead OK I have done a first pass at this. I plan to make some of the citations more specific by adding page numbers as soon as I get a chance. I tried to focus on secondary sources (books and review articles) as much as possible, and took out all of the blow-by-blow of who said what in which paper. I used primary sources where no good coverage was available in secondary ones.
I have some other ideas on things to add or further edit, but I'm not sure when I'll get to those. I think my changes address the fundamental problem, though, so I removed the note.
Ixat totep (talk) 20:56, 8 December 2024 (UTC)[reply]
Which evolutionary grade do you have in mind? There are two possible options here, I think, and one makes more sense, I think. Mlvluu (talk) 23:11, 8 December 2024 (UTC)[reply]
...Nevermind, it's made clear in your edits.
Note that Mussini et al. (2024) only marginally touches on vetulicolians, as it is mainly a paper on Pikaia, and also mistakenly puts the possible origin of the notochord after Yunnanozoon despite it being evident in Nesonektris and Vetulicola. I don't think it's particularly reliable for determining the phylogeny or evolution of vetulicolians.
Something I find more compelling is the tunicate relationship (which can take a few different forms, as summarized in Aldridge et al. (2007) (https://doi.org/10.1111/j.1475-4983.2006.00606.x), with some proposed flaws patched by the Nesonektris paper, García-Bellido et al. (2014) (https://doi.org/10.1186/s12862-014-0214-z)). I could've sworn I had read a paper on the copelate relationship, but I can't find it anymore... Mlvluu (talk) 23:40, 8 December 2024 (UTC)[reply]
@Mlvluu I stepped in to make things more consistent based on what was there. I'm happy to discuss other revisions, but that wasn't what I was trying to clean up.
I disagree with you on Mussini et al, though– Pikaia was the key but the result was the phylogeny involving Vetulicolians, and the revisitation of Romer's somato-visceral hypothesis, which they spend most of the Discussion session discussing. I read the bit about notochords and Yunnanozoon as acknowleging the debatable presence of the notochord in Nesonektris. The supplemental material includes a tree with that notochord scored as present, and it comes out the same.
Having read everythingn I could get my hands on regarding Vetulicolia, I don't find the tunicate arguments convincing, personally, although I'll take a look at those papers again.
What is the "copelate relationship"?
All of that said, I don't see a wikipedia article author's role as picking our favorite theories here. The most recent review article (prior to Mussini et al) pointed to a stem chordate placement as the consensus, so that's what I cited. A recent secondary source is more important than my opinion. Mussini et al. was the one already used for the cladogram, and happened to illustrate the consensus that the secondary source claimed, and backed it up with new information not addressed by the tunicate proposals.
Ixat totep (talk) 03:24, 9 December 2024 (UTC)[reply]
There was at least one paper that proposed that vetulicolians, or at list vetulicolides, are closely related to copelates(/"appendicularians"/"larvaceans") based on the 90-degree torsion of the tail, reduced gill slits, and I think maybe something else.
What is this "most recent review article"? Mlvluu (talk) 03:55, 9 December 2024 (UTC)[reply]
@Mlvluu I think I remember seeing that 90-degree torsion article, I'll try to dig it up and also make sure I have the right justification on the review article sorted tomorrow morning. I think what i did was get a sense of where things seemed to be trending and then worked backwards through articles I'd marked as secondary sources to find the most recent supportive quotes that weren't really contradicted anywhere obvious. But I'll go back through with an eye for the tunicate stuff and see if there's something that supports it just as clearly/recently.
BTW when I say "review" article, I literally just mean an article that says its a review of other research and doesn't try to introduce new theories (or only does so in passing as a "future directions for research include" sort of thing).
Ixat totep (talk) 04:08, 9 December 2024 (UTC)[reply]
...But which is this specific article of which you speak? Mlvluu (talk) 04:15, 9 December 2024 (UTC)[reply]
Also, what’s with Pikaia, a notochord-less animal, being more derived than chorded Vetulicolia?
And also, Banffozoa has gut diverticula… which are protostome-only.
I think Mussini (2024)’s phylogeny has a few critical flaws. IC1101-Capinatator (talk) 07:06, 9 December 2024 (UTC)[reply]
OK, I have made some edits to highlight the monophyletic-sister-group-to-tunicates theory, although it really does seem to fade from the literature after the 2010s. I had to go back to 2014 to find a cladogram (please lmk or just replace it if you know of a suitable newer one- I didn't have time for an exhaustive search. I will keep looking, and will update the text based on what I found. Even if the tunicate theory is mostly dropped, I'll admit that as the next-most-recent theory, it is more worthy of note than others.
@Mlvluu the specific article is Onai et al. 2023, which is a review article conducted by researchers with no connection to the existing theories (see WP:SCHOLARSHIP for review articles counting as secondary sources, and secondary sources being preferred). I had thought it was obvious but then realized I buried it in the last section- I have now moved it to the lede, but also reworked the lede to acknowledge the tunicate theories. Although I had to use Gee (2018) to find a recent secondary source for the tunicate theory, and he in fact favors a stem-chordate placement.
I do not consider Aldridge et al. 2007 a solid source for the tunicate theory because its base phylogeny is too outdated. It places tunicates next to "Euchordata" (Cephalochordata+Vertebrata), a theory that has been thoroughly disproven in favor of Olfactores (Tunicata+Vertebrata). It was also written during the brief period when an endostyle was seen as present in vetulicolians, a theory that was subsequently dropped by its own advocate. Those two things throw off a fair number of points in their analysis, such as how they regard segmentation.
García-Belldo et al.(2014 seems to be the best/most recent source for the tunicate theory. I did find a newer cladogram in A long-headed Cambrian soft-bodied vertebrate from the American Great Basin region (Lerosy-Aubril and Ortega-Hernández 2024), but it placed Vetulicolia as sister to a group consisting of Cephalochordata and Tunicata, which is not an arrangement I've seen advocated anywhere else. I'm not comfortable putting such a significant reworking of chordate phylogeny in this article just to show a near-tunicate placement. That sort of claim belongs in the Chordata article, at least until it is ratified more broadly.
@IC1101-Capinatator I don't think it's our job as Wikipedia editors to judge whether a scientific paper has good or bad methodology. If it's in a reputable peer-reviewed journal (and I believe it is, although I would like to know if there is evidence to the contrary), then appropriate experts have already deemed it to be worth reading. The question of a notochord in Pikaia and how that influences the analysis is addressed in the paper, and the way notochord presence impacts the tree is shown in the diagram (whether it's addressed sufficiently or not is, again, not for us to determine per WP:SCHOLARSHIP).
Our job here is to convey the current state of science, without getting too caught up in the back-and-forth. The trend towards supporting a stem chordate placement is completely independent of Mussini et al. 2024, and is equally valid with a monophyletic Vetulicolia (as most stem-chordate-favoring workers seem to have assumed). However, detailed cladograms for vetulicolians are rare. Mussini is the only source I can find for a stem-chordate cladogram for vetulicolians.
Unlike Lerosy-Aubril and Ortega-Hernández's cladogram, Mussini's places the extant groups in the consensus positions, so the only controversy is the placement of vetulicolians. The point of including the cladogram is to illustrate the current hypotheses, including those controversies. Now that it is paired with the cladogram from García-Bellidos, we have a full illustration of the two positions.
Regarding the gut diverticula and a protostome affinity, that has been mitigated by the discovery of a vetulicolian with both gut diverticula and a notochord, which I have now added to the article in the "History of identification" section.
I hope that addresses everything. After the latest reworking I'm not entirely happy with the division of things between the initial part of "Taxonomy and evolution" and the later "History of identification" subsection, which were split so we could get the seriously outdated or disproven hypotheses (Arthropoda, Kinorhynchia, anything to do with Saccorhyhitida) out of the main flow of the text. I'll probably rework it more if no one else sorts it out- suggestions welcome. Ixat totep (talk) 00:30, 10 December 2024 (UTC)[reply]

Shenzianyuloma

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Mark McMenamin seems to be generally considered dubious and unreliable as a palaeontologists, and peer reviews of the Shenzianyuloma paper point out that the interpretations provided by McMenamin are not sufficiently justified. The taxon also seems to be largely ignored in the literature by other authors, except in Sui, Zhao & Dong (2021). How should this be addressed and cited in the article? Mlvluu (talk) 12:26, 11 December 2024 (UTC)[reply]

@Mlvluu
Mark McMenamin seems to be generally considered dubious and unreliable as a palaeontologists,
Can you provide a source for this? I'm not particulary disputing it, I'd just like to see evidence from within published scientific works.
peer reviews of the Shenzianyuloma paper point out that the interpretations provided by McMenamin are not sufficiently justified.
Is there a way to access these, or cite them in an article? I have journal access through Wikipedia, but not through any other institution. Also, are these the same peer reviews that ultimately approved the publication? My impression is that Geosciences is a WP:RELIABLESOURCE, but I don't really know how to read journal metrics in detail.
The taxon also seems to be largely ignored in the literature by other authors, except in Sui, Zhao & Dong (2021)
Well, it was only published in 2019. It's ignored by Mussini et al. (2024), but I've not been able to find any other post-2019 papers or books that list an even sort-of complete set of vetulicolian genera. The most recent such listing prior to Mussini is Li et al. (2018) which provides the base phylogeny used under "Classification." So it's no surprise that it does not include Shenzianyuloma (or Alienum, if that's even really a vetulicolian). Also, compare to Ooedigera, which was discovered in 2011. It's included in both Li and Mussini (and McMenamin), and in García-Bellido et al. (2014), but otherwise I don't recall seeing any further comment on it. Only one of those is post-2019, and I think I'd need to see more than a lack of appearance in a single study that might have been expected to include Shenzianyuloma before deeming it "ignored."
How should this be addressed and cited in the article?
My preference is for the article to only reflect what has been published in WP:RELIABLESOURCE. If someone has published a peer-reviewed response disputing McMenamin (2019), then we can and should include that when mentioning Shenzianyuloma. Or if there is a peer-reviewed or otherwise reliable assessment of problems with McMenamin's paleontology in general, that also can be cited. For example, Barry Fell, who was a respected marine biologist and expert on sea urchins, also published pseudoscience "archeology" books in retirement. It is easy to find evidence of both the quality of his work on echinoids, and the lack of scientific rigor in his pseudo-archeology.
But if there is no such WP:RELIABLESOURCE then we do nothing. We don't editorialize based on what's essentially gossip. I have my opinions about certain workers and their biases and flaws, but if one of those workers publishes something relevant and no one publishes commentary agreeing with my sentiments, then I set those sentiments aside and include the publication. If there's really a problem, then eventually someone will publish about it. Degan Shu, in particular, seems likely to respond to any problematic claims involving Vetulicolia. The scientific literature in all disciplines is full of such responses, so if anything the lack of such a response indicates a certain level of passive acceptance. Ixat totep (talk) 15:24, 11 December 2024 (UTC)[reply]
I had meant to add more info on gut diverticula anyway so I did that, and also added a note that Shenzianyuloma has not been further reviewed since discovery. Without citable work discussing either Shenzianyuloma or McMenamin's scholarship, I think that's the most that can be done. It should provoke future editors to add more material if and when it becomes available.
Ixat totep (talk) 16:01, 11 December 2024 (UTC)[reply]
I'm not sure about sources directly criticizing McMenamin (such a thing is hard to find when the Google Scholar results are cluttered by articles by McMenamin himself; I think @Ta-tea-two-te-to would know more about this), but Wikipedia editors (and the general online palaeontology community) generally seem to agree that McMenamin papers are not reliable. Mlvluu (talk) 16:08, 11 December 2024 (UTC)[reply]
Ah, I almost forgot:
There's a "Review Reports" button below the title on the page of the paper. Mlvluu (talk) 16:15, 11 December 2024 (UTC)[reply]
Note: Please keep in mind that I had never heard of Mark McMenamin before working on this page, and have no stake whatsoever in his reputation or the validity of his work, either here or elsewhere. All I care about is representing the science as published accurately and responsibly.
OK I read the reviews, and I honestly don't see the problem (although see also my responses to other concerns further down). The two first-round reviews found problems, and then the second-round review says:
This new version of the MS is significantly improved, compared to the original one, and the author has obviously significantly modified his text, so as to take into account the comments made during the first round of review. As it now stands, the MS offers a very-well written, up-to-date review of the current knowledge on these two groups of early deuterostomes, based on a relatively exhaustive literature, abundant illustrations, and the description of a new, weird-shaped vetulicolian from China. The diversity of interpretations about these early deuterostomes (and in particular, the vetulicolians) is much better expressed in this revised version.
and the remaining concern regarding a formal diagnosis for Shenzianyuloma was addressed in the response. The specimen was deposited with an appropriate authority and is available for other workers to examine.
Critical comments in first-round reviews that lead to a revision of the paper should not count against anything. Everyone writes bad first drafts now and then.
@Mlvluu to address your other points:
generally seem to agree that McMenamin papers are not reliable
I didn't see much to support such a broad claim in that discussion, but the linked fringe theory discussion was interetesting. However, there are several differences in the two situations:
  1. The fringe discussion mentions predatory journals, but (again AFAICT, contrary evidence welcome), Geosciences is not such a journal.
  2. McMenamin's fringe Ediacaran theories were, as noted, published in books in a way that is unusual for such claims. The closest thing here is that the Shenzianyuloma article is published in Geosciences rather than one of the usual paleontology suspects. That makes sense for the review portion (reviewing one field's state for workers in an adjacent field), but less so for a new taxon, but that's already clear from the citation itself (that's part of why we have citations!)
  3. The deletion discussion notes that no database had accepted Clementechiton, but both the Paleobiology Database and GBIF (which marks it as "accepted") include Shenzianyuloma.
So I don't see a reason for us to second-guess a non-predatory (AFAICT) journal and two databases. I have my quibbles with online databases and try to cite them sparingly, but since the deletion discussion mentioned them I feel it's relevant here.
and the general online palaeontology community
TBH, I don't care what people say online, only what they say in WP:RELIABLESOURCE. Yes, the Triassic kraken thing seems pretty bonkers, but looking on the Mark McMenamin page, there are ample cite-able sources saying so. No such sources exist regarding Shenzianyuloma despite the fossil being made available to the community. Contrast this with the rapid response to claims of Yanjiahella being the earliest echinoderm, or this brutal takedown of a radical reinterpretation of early Asterozoan phylogeny.
Even broken clocks are right twice a day. Good workers do bad work sometimes, and bad workers occasionally manage to pull something worthwhile together. If no one thinks McMenamin is worth responding to even though they think Shenzianyuloma is bunk, that's a problem in the scientific community and not one that Wikipedia should try to mitigate.
Yes, the Triassic kraken is a bizarre proposal and was rightly argued down. On the other hand... have you met the calcichordate hypothesis? It always seemed bonkers to me, and only got more so the more Jeffries duct-taped it to keep it viable. I think in the end it involved the loss of the stereom skeleton on at least three separate occasions? And of course, it was ultimately proven to be completely wrong, although it introduced some ideas regarding asymmetry that I've seen referenced elsewhere, and I think is what motivated the Olfactores hypothesis, which was ultimately vindicated.
I'm not trying to equate these situations- the calcichordate theory had a whole faction of defenders in a debate that ran for decades. But it is a good illustration that science allows for bonkers theories and responses to them, and handles such problems on its own without the help from us. The Triassic kraken was addressed with published statements from reputable paleontologists in reliable sources.
What we really need here is for someone to do an updated comprehensive revision of Vetulicolia, like Aldridge et al. (2007), or the one kind-of hidden (but really quite interesting) in Li et al. (2018). Such a revision would have to address all known genera and either include or intentionally exclude Shenzianyuloma. Until that happens, given the solid second-round review of the article in question, all we can do is note the lack of further work on the genus. Which is hardly a unique situation in paleontology articles included on Wikipedia. If we took down every taxon that's only known from one specimen with limited work done on it, there would be a lot fewer paleontology pages. Even if McMenamin is more-or-less a crank, he's a(n alledged) crank who revised his work to the point of getting it accepted in what one reviewer characterized as a "main-stream scientific paper", and that's what we need to work with. Ixat totep (talk) 18:10, 11 December 2024 (UTC)[reply]
@Mlvluu a more fruitful avenue of work might be regarding MDPI#Evaluation_and_controversies, as MDPI is the publisher of both Geosciences and Diversity (the journal publishing the paper from Sui, Zhao & Dong (2021)). It seems to have a wobbly reputation, in that there have been definite concerns, but also not enough to get the whole thing shut down or classified as irredeemably predatory.
A sentence following the bit under "History of identification" on Shenzianyuloma saying something like the following (existing text removed stricken through, new parts bolded):
The discovery of Shenzianyuloma brought to light a vetulicolian interpreted as having both a notochord (a definitively deuterostome trait) and gut diverticula, although this has not yet been further examined by other researchers. research on this genus has to date only been published through MDPI, which has faced questions regarding its publishing practices.(with appropraite citations borrowed from the MDPI page)
That still feels a bit aggressive to me, as I'm not sure the Vetulicolia article is the right forum for such statements, but if you feel such a statement is necessary, then I think that's more defensible as encyclopedic text than an attack on McMenamin by way of his other work. Ixat totep (talk) 18:36, 11 December 2024 (UTC)[reply]
@Mlvluu take a look at the edits I just did to Shenzianyuloma and see what you think of that approach. We should not need to replicate all of that in this article (e.g. the lack of Shenzianyuloma in the recent cladogram is obvious on the Vetulicolia page), but perhaps there is somehing worth mentioning. Ixat totep (talk) 19:42, 11 December 2024 (UTC)[reply]
I think it's fine just being on that article. It would seem bit tangential and shoehorny here, or so I think it looks when I visualize it in my mind...
Maybe I should try writing a paper about these things... Mlvluu (talk) 19:49, 11 December 2024 (UTC)[reply]
“Maybe I should try writing a paper about these things…”
Of course, there’s still the chelicerate paper for you to write first :) IC1101-Capinatator (talk) 21:26, 11 December 2024 (UTC)[reply]
To put a bow on this: I have now gone through all vetulicolian pages and replaced McMenamin 2019 with other suitable sources for everything except Shenzianyuloma. This article now only cites it for Shenzianyuloma, and I have added information about the suspect provenance to further indicate that Shenzianyuloma deserves heightened scrutiny. I have also added the publisher to the source citation (rare for journals, but it is allowed) and made it a wikilink so folks can see the discussion of concerns about the publisher on that page if they want. I think that does the best we can as far as balancing a proposed vetulicolian that no one has disputed in a peer-reviewed article with legitimate concerns regarding McMenamin's other work, and the somewhat wobbly status of MDPI as a reputable journal publisher.
Thanks for all of the info and discussion here!
Ixat totep (talk) 19:50, 15 December 2024 (UTC)[reply]

Nesonektris and "Form A" classifications

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The Vetulicolia#Classification section is almost entirely drawn from Li et al. (2018). There are only four exceptions:

Post-2018 taxa

Two are Alienum and Shenzianyuloma, both of which were discovered after that paper (see above for further discussion regarding Shenzianyuloma), and I'm perfectly comfortable just citing their discovery papers for placement as neither requires any other change to the classification.

"Form A"

One is "Form A", which is weird but gets referenced in various places, but is not discussed in Li et al. presumably because it has not been formally described. It was also not mentioned in Aldridge et al. (2007).

I'm reasonably comfortable placing it with the given citation. One could argue that placement under Banffidae rather than directly under Banffozoa/Heteromorphida is warranted by the diagnostic criteria for Banffiata and Banffidae being inherited from Banffozoa, which was emended to include the contents of Heteromorphida, but as no source has done that, I think it's best to leave it directly under the class. Contrary opinions welcome.

A few sources misconstrue "Form A" as a species within Heteromorphus, but as noted in the citation, Shu (2005) is clear that it is a distinct member of Heteromorphida. (I'm working on a Banffozoa page which will better explain the Banffozoa vs Heteromorphida confusion- it's not really relevant for placing "Form A", I don't think)

Nesonektris

The last is Nesonektris, which was placed directly under Class Vetulicolida CHEN and ZHOU 1997 by Garcîa-Bellido et al. upon discovery, but moved to Didazoonidae by Li et al. (2018) in the same paper that reclassified Yuyuanozoon into that family. The paper goes into extensive detail about Yuyuanozoon based on new specimens to justify its reassignment. But there is no mention on Nesonektris outside of the table laying out the overall phylogeny. This is odd because two other potentially controversial entries in that table get a note: Beidazoon regarding its placement in Vetulicolidae rather than Beidazoonidae, and Skeemella regarding the ongoing questions about its vetulicolian-ness.

The authors emended the diagnostic criteria of Didazoonidae to:

Bilaterally symmetrical animal with clear subdivision of body into presumed anterior and posterior sections. Neither the subquadrate to ovoid anterior section nor the posterior section is biomineralized. The anterior section has a large, circular opening at the presumed anterior end of the animal, posterior of which are six subdivisions demarcated by five lines; five, presumed laterally positioned, oval openings on both sides of the anterior section coincide with the lines of subdivision. Segments of posterior section may bear up to six annulations.

The morphological information in the Nesonektris row of the table includes "Anterior opening: Anterior edge vertical", "Anterior section: Subquadrate in lateral view, lateral groove narrow", "Lateral pouches: no pouches observed", "Posterior section: Internal rod-like structure extends along axis of posterior section", and "Anus: Terminal."

Earlier in the paper, the authors define the terminology "lateral pouches/openings" to replace what they view is the unwarranted assumption that these are gill pouches.

So, to me, the lack of pouches documented in the table contradicts their own diagnostic criteria. The "Anterior opening" entries for the other Didazoonids, including Yuyuanozoon, mention a "circumventing feature", which is not mentioned for 'Nesonektris, which makes the assignment even more confusing to me.

I also noticed that (as cited in the page), while the Paleobiology Database has accepted Yuyuanozoon as a Didazoonid, it has left Nesoniktris directly under Class Vetulicolida per G-B et al.

So, the question is whether to leave things as I have it, with Nesonektris an exception backed up by G-B and PBDB, or whether it should be under Didazoonidae for consistency. I'm kind-of relying on PDBD here as the arbiter of what is appropriate, but I'm familiar enough with it to know that it has many, many inconsistencies of its own. Is there a better approach? Ixat totep (talk) 20:14, 11 December 2024 (UTC)[reply]

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