Talk:Eldonioid

Should this be renamed Eldonioidea?

Eldonioidea and Eldoniidae are distinct taxa, and this page clearly covers the larger Eldonioidea. Should it be renamed?

Ixat totep (talk) 18:02, 31 October 2024 (UTC)

Swapped Eldonioid and Eldoniid, so this is now sorted out.

Ixat totep (talk) 05:04, 21 December 2024 (UTC)

They aren't, though; "Eldonioidea" is synonymous with Eldoniidae as it is actually defined, as far as I can tell, and the usage of "Eldoniidae" for a smaller group is erroneous. Mlvluu (talk) 23:24, 21 December 2024 (UTC)

@Mlvluu please see Schroeder, Natalie I.; Paterson, John R.; Brock, Glenn A. (2018). "Eldonioids with associated trace fossils from the lower Cambrian Emu Bay Shale Konservat-Lagerstätte of South Australia". Journal of Paleontology. 92 (1): 80–86. Bibcode:2018JPal...92...80S. doi:10.1017/jpa.2018.6. ISSN 0022-3360. S2CID 197586878. for an assessment of the class Eldonioidea (Dzik, 1991) with families Eldoniidae (Walcott, 1911) and Rotadiscidae (Dzik, 1991) (and informal group "Paropsonemids", although it looks like there's a Template:Taxonomy/Paropsonemida of which I was unaware).

The table I'm using as a source for the phylogeny is very much like the one (Li et al., 2018) used for the taxonomy (not cladograms) in Vetulicolia#Classification. And it's in a mainstream journal with multiple co-authors (not a McMenamin thing). Note that while the first version of the article was retracted, that DOI is for the corrected article (just in case you see the retraction and not the correction).

Also, while it's obviously valid to raise a concern at any time, I've made a point of leaving more than a month before renaming, and I had spread out various edits to the page moving towards focusing on Eldonioidea, so it's really irritating to have this objected to now and not on any of the other things I did to see if anyone would comment. Just venting a bit here. I did my best to telegraph this way in advance.

Ixat totep (talk) 01:02, 22 December 2024 (UTC)

Schroeder, Paterson & Brock (2018) does not formally redefine/redescribe/rediagnose Eldonioidea or Eldoniidae (as, for example, Lustri, Gueriau & Daley (2024) does for Offacolidae); rather, it just says things about the taxa presuming such redefinitions. I made sure to check that source before commenting.

Sorry for saying this so late; I hadn't actually bothered to look at the talk page until I saw your first reply here in my watchlist. Mlvluu (talk) 02:13, 22 December 2024 (UTC)

Welp, a couple of things then.

• Rotadiscus is definitely in Rotadiscidae (Dzik, 1991), not Eldoniidae (Walcott, 1911). As is shown in Template:Taxonomy/Rotadiscus and Template:Taxonomy/Rotadiscidae, which I did not set up.
• Eldonia is definitely in Eldoniidae (Walcott, 1911)
• Eldonioidea (Dzik, 1991) is definitely a formally declared class and formally referenced by at least some other workers (regardless of whether it is equivalent to Eldoniidae or not)
• The most important paper tying eldonioids to Cambroernida is Li, Yujing; Dunn, Frances S.; Murdock, Duncan J.E.; Guo, Jin; Rahman, Imran A.; Cong, Peiyun (May 10, 2023). "Cambrian stem-group ambulacrarians and the nature of the ancestral deuterostome". Current Biology. doi:10.1016/j.cub.2023.04.048., which calls them "eldonioids" throughout, and focuses on Rotadiscus, specifically. But they don't do a "Systematic Paleontology" thing because... idk, cladistics?

Cladistics and Linnaean taxonomy are uneasy bedfellows, and this is a prime example of things being published pretty clearly in one system without updating the other. I don't know how to square the circle, but here is where I come out:

• "Eldonioid" (and Eldonioidea) is definitely not wrong as a name for the larger form of the group
• If you're correct, then "Eldoniid" (and Eldoniidae) isn't either, but I'm having trouble squaring that with the use of Rotadiscidae; I can definitely find formal declarations involving each family (lmk if you want me to dig them up), even if I can't find a formal Systematic Paleontology section in one paper that pulls both together with Eldonioidea
• I renamed "Eldoniid" to "Eldonioid" instead of "Eldonioidea" specifically because the formal Linnaean groups seemed a bit squirrely (although not unsually so compared to other areas where there have been far more cladograms than systematic revisions), and Li et al. 2023 uses "eldonioid" when discussing their placement in Cambroernida

So, I don't see a reason to switch this page back to Eldoniid. I think Eldonioid is at least as correct, and to me seems more likely to be more correct when the dust settles. As Schroeter et al. 2018 notes, a formal revision of the group is long overdue, and many workers (nine between those two alone) are already using "eldonioid" for the larger group.

If you want to rewrite the article to deny the distinction between eldoniids and rotadiscids, I'm not going to get in an edit war with you. But I don't think there's any clear statement of anything, anywhere for these groups. Just a lot of piece-meal things that aren't consistent with each other. Schroeder+Li is the closest thing to making sense of it, to me.

Ixat totep (talk) 03:36, 22 December 2024 (UTC)

...Wait, there's something completely off with my understanding.

I could've sworn I had read in an iteration of this article something about Dzik (1991) defining Velumbrellida as essentially a junior synonym of Eldoniidae...

Sorry about that. It was just a mistake on my part. I'd say 'Velumbrellida' would technically be the senior synonym here, and 'Eldonioidea' just invalid as a clade, but I think that could run against the precedent set by the Hurdiidae article... Mlvluu (talk) 04:03, 22 December 2024 (UTC)

I think you're right about Vulumbrellida and Eldoniidae.. But i'm not 100% sure. I'd have to go back and look. It seemed like pretty much everyone ignord the Velumbrellida part of the proposal. I've only see Eldonioidea and Rotadiscadae of his higer taxa in use.

Anyway, I tend to argue rather emphatically, but I do realize I still might be wrong. This is the best sense I could make of it, but also I don't want to make up certainty where there shouldn't be any.

Ixat totep (talk) 04:40, 22 December 2024 (UTC)

OK I went back through Dzik's 1991 paper:

Dzik, Jerzy (1991). "Is fossil evidence consistent with traditional views of the early metazoan phylogeny?" (PDF). In Simonetta, AM; Conway Morris, S (eds.). The early evolution of Metazoa and the significance of problematic taxa. Oxford: Clarendon Press. pp. 47–56.

(which is a pain because even though he defines new classes and families, he just does it in the middle of paragraphs in the text, and that PDF does not have text indexed for search).

If Dizk had written out a Systematic Paleontology matching the text (which is in a long paragraph starting at the end of page 50 with the phylum assignment, with most of the rest near the end of that paragraph halfway through column 1 of page 51), it would look like:

• Phylum Tentaculata
  • Class Eldonioidea n. cls. ("conical, lobate mantle instead of cylindrical (as in the Bryozoa) or bivalved (as in the Brachiopoda) ones")
    • Order Dinomischida n. ord. ("long peduncle and deeply lobate mantle")
      • Genus Dinomischus
    • Order Velumbrellida n. ord. ("circular, disc shaped body with reduced peduncle")
      • Family Eldoniidae (Walcott, 1911) ("with radial ribs")
        • Genus Eldonia (Walcott, 1911)
        • Genus Velumbrella (Stasińska, 1960)
        • Genus Yunnanomedusa (Sun & Hou, 1987) [=Stellostomites Sun & Hou, 1987)]
      • Family Rotadiscidae n. fam. ("with almost smooth discs ornamented only by growth lines")
        • Genus Rotadiscus (Sun & Hou, 1987)

---

After that, the next sighting of Class Eldonioidea (Dzik, 1991) that I've found is:

Chen, Jun-Yuan; Zhu, Mao-Yan; Zhou, Gui-Qing (1995). "The Early Cambrian medusiform metazoan Eldonia from the Chengjiang Lagerstätte". Acta Paleontologica Polonica. 40 (3): 213–244.

• Class Eldonioidea (Dzik, 1989)
  • Genus Eldonia (Walcott, 1911) [Yunnanomedusa (Sun & Hou, 1987); =Stellostomites Sun & Hou, 1987)]
    • E. ludwigi (Walcott, 1911)
    • E. eumorpha (Sun & Hou, 1987)

I don't know why Chen says Eldonioidea is from Dzik, 1989, when the book The Early Evolution of Metazoa and the Significance of Problematic Taxa was published by Cambridge University Press on November 29, 1991. Dzik himself later gives the class as Eldonioidea (Dzik, 1991). We'll just sweep that under the rug, I think. Chen emends Eldonioidea as follows:

Medusiform lophophorates with radially-symmetrical disc either soft-bodied or sclerotized. U-shaped alimentary canal coiled subhorizontally. Mouth placed near anus, both facing ventrally. The mouth surrounded by a lophophore. Vascular system consisting of numerous radially-extended sacs, radially-extended vascular canals radiating from central ring canal to periphery.

This might be where the confusion comes in, because Chen didn't bother with Eldoniidae, even though Dzik included it. Chen notes that Rotadiscus (Sun & Hou, 1987), Hullingia (Narbonne et al. 1991), Velumbrella (Stasińska, 1960), and Paropsonema (Ruedmann 1916) might be related to Eldonia, and after listing those stated:

The eldonioids, therefore, appear to have been widespread in the Early Paleozoic Oceans

So clearly all of these were considered at least potential "eldonioids", making the omission of Eldoniidae and Rotadiscidae all the more puzzling.

---

There are more papers that reference either Eldoniidae or Rotadiscidae, but I haven't found one that references both by name until Schroeder, with one exception: What appears to be a dissertation (it notes an "advisor" on the title page) by MacGabhann in 2012 that completely reworks everything based on claims that various names are invalid, ending up with class Eldoniata (=Eldonioidea), family Maoyanidiscidae (=Rotadiscidae), and new family Paropsonemidae. I'm not sure what to do with that, it seems to be ignored by Schroeder, and I know dissertations as sources are tricky.

The paper that sort-of follows MacGabhann is:

Hagadorn, James W.; Allmon, Warren D. (2019-01-01). "Paleobiology of a three-dimensionally preserved paropsonemid from the Devonian of New York". Palaeogeography, Palaeoclimatology, Palaeoecology. Studies in Honor of Prof. David J. Bottjer. 513: 208–214. doi:10.1016/j.palaeo.2018.08.007.

which does not declare a Systematic Paleontology, but ends §5 "Other dorsally preserved paropsonemids" by saying that Discophyllum, Eldonia, Maoyanidiscus, Pararotadiscus, and Paropsonema "share sufficient synapomorphies that they merit formal grouping but can be informally referred to as eldonids."

┻━┻ ︵ヽ(`Д´)ﾉ︵ ┻━┻

So clearly they agreed with renaming Rotadiscus but did not adopt any of MacGabhann's higher divisions.

---

So what appears to have happened is that the idea of Eldonioidea as Dinomischida+Vellumbrellida was quickly dismissed, and Velumbrellida was (AFAICT) never mentioned again. So Velumbrellida became de-facto synonymous with Eldonioidea, not Eldoniidae. @Mlvluu I might actually owe you an apology for furthering the confusion b/c I think I wrote this sentence from the current article:

...and Vellumbrellida. The latter order was divided into Eldoniidae and Rotadiscidae. Most subsequent authors doubt a close relationship between Dinomischus and eldoniids. As a result, "Eldonioid" and "Eldoniid" have been used interchangeably by many recent publications...

which does not seem quite right. The confusion over eldoniod vs eldoniid (or eldonid) doesn't seem directly related, as Eldoniidae and Rotadiscidae were clearly defined under Eldonioidea (by way of the now-ignored Velumbrellida).

@Mlvluu I do want to acknowledge your valid point that a table is not a formal reassignment (and Li et al. 2018's table of vetulicolians was accompanied by a formal reassignment where necessary, even though only one of the two was actually explained and adopted by other researchers). So my treatment of Schroder as analogous to Li 2018 was flawed.

But I don't think there's a better option. I am inclined to update the Taxonomy section basedon Schroeder, because what's there at the moment is not sourced at all (except one bit to Schroeder!). The fundamental Eldonioidea/Eldoniidae/Rotadiscidae set up by Dzik remains valid.

For the assignment to Cambroernida, Caron et al. 2010 just uses the informal term "Eldoniids" in their systematic paleontology, but the mention Eldonia, Stellostomites, Rotadiscus, and Pararotadiscus, and I don't think anyone has ever assigned Rotadiscus to Eldoniidae, so we can treat this as the larger group established by Dzik. And the later cambroernid paper focusing on Rotadiscus (Li et al. 2023) uses the term "eldonioids."

So I think Schroeder 2017 for updated internal phylogeny (compatible with Dzik 1991), and Li 2023 for external phylogeny despite informal terms (because the soft-bodied Rotadiscus preservation seems to address Schroeder's uncertainty over the cambroernid assignment), are the sources to use.

Ixat totep (talk) 18:10, 22 December 2024 (UTC)