Talk:Halwaxiida

The dorsal sclierete spikes look a little like 'morphed' versions, of the lateral 'side plates', on Anomalocaris & Opabinia. —Preceding unsigned comment added by 66.235.26.150 (talk) 18:40, 1 March 2011 (UTC)

Contributions from Cambrian explosion revision 220751202 which could perhaps be included in the article
Wiwaxia, found so far only in the Burgess Shale, had chitinous armor consisting of long vertical spines and short overlapping horizontal spines. It also had what looked like a radula (chitinous toothed “tongue”), a feature which is otherwise only known in molluscs. Some researchers think the pattern of its scales links its closely to the annelids (worms) or more specifically to the polychaetes (“many bristles”; marine annelids with leg-like appendages); but others disagree.

Orthrozanclus, also discovered in the Burgess Shale, had long spines like those of the wiwaxiids, and small armor plates plus a cap of shell at the front end like those of the halkieriids. The scientists who described it say it may have been closely related to the halkieriids and the wiwaxiids.

Halkieria resembled a rather long slug, but had a small cap of shell at each end and overlapping armor plates covering the rest of its upper surface – the shell caps and armor plates were made of calcium carbonate. Its fossils are found on almost every continent in early to mid Cambrian deposits, and the “small shelly fauna” deposits contain many fragments which are now recognized as parts of Halkieria’s armor. Some researchers have suggested that halkieriids were closely related to the ancestors of brachiopods (the structure of halkieriids' front and rear shell caps resembles that of brachiopod shells) and to the wiwaxiids (the pattern of the scale armor over most of their bodies is very similar). Others think the halkieriids are closely related to molluscs and have a particularly strong resemblance to chitons.

Odontogriphus is known from almost 200 specimens in the Burgess Shale. It was a flattened bilaterian up to 12 cm (5 in) long, oval in shape, with a ventral U-shaped mouth surrounded by small protrusions. The most recently found specimens are very well preserved and show what may be a radula, which led those who described these specimens to propose that it was a mollusc. But others disputed the finding of a radula and suggested Odontogriphus was a jawed segmented worm belonging to the Lophotrochozoa (a “super-phylum” which contains the annelids, brachiopods, molluscs and all other descendants of their last common ancestor).

More sources

 * AN EARLY CAMBRIAN RADULA / ; Journal of Paleontology, May 2008  by Butterfield, Nicholas J;

Competing theories
-- Philcha (talk) 12:10, 7 August 2008 (UTC)
 * Articulata, uniting arthropods and annelids - see citation at Coway Morris & Peel 1995.

Butterfield cladogram
Couldn't find a cladogram in recent NJB work; suspect the one drawn will have to be based on what he writes less explicitly about the relationships he is prepared to accept, and that he proposes for Wiwaxia etc. Martin  (Smith609 – Talk)  21:11, 15 August 2008 (UTC)


 * I checked the article history and got the impression you drew the Butterfield cladogram. Am I right about that? If so, can you remember from what source(s) you (re)constructed the Butterfield cladogram? If not, we may have a major problem. -- Philcha (talk) 21:35, 15 August 2008 (UTC)


 * Ah, yes. Looking at the date, I suspect that he presented it at PalAss - indeed, that does ring a bell now I think back to it.  If you fancy a bit of beaurocratic banter, we could debate the suitability of a reliable yet unverifiable source, or closely read "Hooking some stem group worms", which I suspect will support the cladogram.  Or you could plonk on the PalAss2007 reference and hide this discussion from the GA reviewers...  Martin  (Smith609 – Talk)  21:44, 15 August 2008 (UTC)

Summary of the situation
Please amend if you think there are significant errors or omissions, as this is a complex package of articles and the analysis of options needs to start off on the correct basis: -- Philcha (talk) 21:18, 28 August 2008 (UTC)
 * 5 articles heavily involved (at present): Halwaxiid, Halkieriid, Wiwaxia, Orthrozanclus, Odontogriphus.
 * These feature in a phylogenetic debate that's gone on since 1990.
 * This debate has effectively 3 sides.
 * Caron (et al), Scheltema (et al) & Eibye-Jacobsen say Wiwaxia is a mollusc (stem or crown), and so are the rest.
 * Butterfield says Wiwaxia is an annelid / polychaete, halkieriids are sister group to molluscs, etc.
 * Conway Morrris initially (1985, 1990) regarded Wiwaxia as a mollusc, but since then has wandered around looking for a consensus position.
 * Some obscure small shelly fauna sclerites called siphogonotuchids look very like those of halkieriids
 * Another connection between Halkieriid and Chancelloriidae (Porter, 2008), which could upset the other phylogenies.
 * The scope for duplication of phylogenetic analysis content is huge. Duplication would be the easy way out, but some reviewer's bound to grumble.
 * Each article has to give some of the details, otherwise it becomes "he said ..., she said ...".

Historical vs thematic presentation
At present the debate is presented chronologically in all the articles. This is good in terms of completeness, but increases duplication - especially in the case of Butterfield, whose views appear to have changed the least.

Alternatives:
 * Report the current view of each party, drawing earlier material only when necessary.
 * Not too hard for Butterfield, Scheltema and Eibye-Jacobsen, whose positions have not changed significantly.
 * Tricky for Caron. Caron, Scheltema, et al (2006) goes for (near-)molluscs. Conway Morris and Caron (2007) goes for 2 possible hypotheses. Seems to depend whether Caron is lead author.
 * Tricky for Conway Morris, who went for (near-)molluscs in 1985 and 1990, but Conway Morris and Caron (2007) goes for 2 possible hypotheses.
 * Risk of misrepresentation / misleading summarization.
 * Try to group the views. Very tricky:
 * Greater risk of misrepresentation / misleading summarization.
 * Scheltema et al (2003) consider and Eibye-Jacobsen (2004) consider only Wiwaxia. Almost all of Butterfield's arguments focus on Wiwaxia.
 * OTOH Caron, Scheltema et al (2006) and Conway Morris and Caron (2007) present cladograms covering the whole package of animals.

Best of both worlds?
One episode on the career of the chess player Howard Staunton is very controversial (commentators occasionally use unparliamentary language). I created The Staunton-Morphy controversy to house a blow-by-blow account to which Howard Staunton can refer. Then the chess gang (including Philcha) can figure out how to produce a neutral summary in Howard Staunton.

Advantages of adopting this approach for Halwaxiid and related articles:
 * The blow-by-blow account gives us a quick reference for use in discussions, e.g. with reviewers.
 * Then we can provide a simpler "current view of each party" in Halwaxiid, and subsets of that in the articles about the individual animals.
 * Might actually ease maintenance, provided everyone updates the blow-by-blow account first.

Disadvantages: -- Philcha (talk) 21:54, 28 August 2008 (UTC)
 * The chess gang seem a bit unwilling to tackle the contentious job of summarising the controversy in Howard Staunton.
 * Can we be sure every one will update the blow-by-blow account of the Halwaxiid controversy first.?


 * My feeling would be that only the current interpretations need to be mentioned in each article. I do like the "summary style" approach, so I guess it would be nice to be able to give a brief account on each genus's page, linked to a central discussion - either in Halwaxiid, or (perhaps better?) in a summary article at e.g. Lophotrochozoan roots and stems.
 * Instinctively I would arrange the accounts in an "interpretation by interpretation" order, as a good argument doesn't expire. So perhaps a "Caron currently thinks this, SCM now thinks this, and Butterfield has maintained throughout that this" approach would do the job. That lets you develop each hypothesis without worrying about order of publication.  A time based system probably works too, and I guess it highlights how the description of new genera has changed viewpoints.
 * As far as maintenance is concerned, hopefully if we make the presence of the main article obvious enough, that will remain reasonably up-to-date. And in all honesty it is most likely to be one of us making any updates!
 * Martin  (Smith609 – Talk)  08:32, 29 August 2008 (UTC)


 * You're right, who else matches our level of expertise on the subject? (saddos!)
 * I'll do the historical brain-dump article first. "Lophotrochozoan roots and stems" sounds like the title of a journal article (? Butterfield). For now I'll use "Debate about Cambrian Lophotrochozoans" - I think "Cambrian" is important, so readers won't expect it to cover e.g. protostome/deuterostome split or lophotrochozoans/ecdysozoan split. -- Philcha (talk) 09:47, 29 August 2008 (UTC)

Possible thematic presentation
Now that I've saved the saga at Debate about Cambrian Lophotrochozoans, I feel more comfortable about attempting a thematic approach. The biggest single problem is the 2 cladograms in Conway Morris & Caron (2007), but I wouldn't mind describing them separately. OTOH I like the advantages:
 * Easy to incorporate Scheltema et al (2003) and Eibye-Jacobsen (2004) as minor contributions  to one of the views, which is about right as they only considered Wiwaxia in detail.
 * Easy to incorporate any new players - of course if new players propose a really distinctive phylogeny they get a new section.

So the groupings would be:
 * Halwaxiids monophyletic, stem-group molluscs
 * Caron, Scheltema, et al (2006)
 * Conway Morris and Caron (2007), "Hypothesis 1"
 * Bit parts for Scheltema et al (2003) and Eibye-Jacobsen (2004); and for Conway Morris & Peel (1990).
 * Halwaxiids monophyletic, sister group to annelids and brachiopods
 * Conway Morris and Caron (2007), "Hypothesis 2"
 * "Halwaxiids" paraphyletic (note quotes)
 * Butterfield 1990 to present (sounds like a Mastermind special subject).
 * Conway Morris & Peel (1995) ??
 * I think "paraphyletic" is better than "polyphyletic" as Butterfield presents them as offshoots of a single polytomy and as excluding the other offshoots, molluscs, annelidus & brachiopods.

What do you think? -- Philcha (talk) 11:09, 29 August 2008 (UTC)


 * Sounds like it could work well. I quite like the "not monophyletic" phrasing you use in DaCL - it makes for one fewer jargon term, which can only be a good thing.  I would tend to consider them as polyphyletic, but I guess that as there is no overt claim about the inclusion of the last common ancestor either word could be used validly if you chose to do so.  Martin  (Smith609 – Talk)  02:06, 18 September 2008 (UTC)


 * Yikes, I've just noticed Caron, Scheltema, et al (2006) is "stem molluscs, but not monophyletic" I'll need to develop a new meta-taxonomy!
 * I've started a new sandbox page, User:Philcha/Sandbox/Halwaxiid, as this is complicated and will probably take a few attempts. -- Philcha (talk) 10:54, 18 September 2008 (UTC)

Another try
I now think a thematic presentation is not a great idea, as it would stretch even my liberal interpretation of WP:OR and WP:SYNTH too far - the point that Caron, Scheltema, et al (2006)'s position is "stem molluscs, but not monophyletic" illustrates this.

I'll now try a table to summarise what goes where. Note that the possible Halkieriid-Chancelloriidae link gets in as a possible spoiler. -- Philcha (talk)


 * I like it. Martin  (Smith609 – Talk)  13:00, 6 October 2008 (UTC)

Checklist:

"Weasel words" template
Since I've been pre-occupied with useful WP activities, I didn't notice that in Sept 2008 some (anon) put a banner "This article contains weasel words, vague phrasing that often accompanies biased or unverifiable information" at the top of the article. There's nothing unverifiable here. To support a claim that some of the info is biased, the perp would have to read and understand about a dozen scientfic papers. It would also have been helpful rather than annoying if the perp had provided some examples. So guess what I'm going to do now. --Philcha (talk) 19:50, 28 April 2009 (UTC)

Reference to broken DOI
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