Talk:Halkieriid

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The article was uncategorized, so I changed that. I put it in categories of two different phyla becausein the article it's stated Halkieria was a mollusc while on the brachiopod article it's also considered a possible ancestor. ExuTrancaRede 19:47, 8 October 2006 (UTC)

Added "under the remit of the Cambrian explosion taskforce". -- Philcha (talk) 15:53, 1 August 2008 (UTC)

Sources[edit]

Vol. 315. no. 5816, pp. 1255 - 1258 DOI: 10.1126/science.1137187

  • 1st artic specimen found by Conway Morris et al at Sirius Passet Showdown on the Burgess Shale
  • Simon Conway Morris (2006 June 29) Darwin's dilemma: the realities of the Cambrian ‘explosion’ Philos Trans R Soc Lond B Biol Sci. 2006 June 29; 361(1470): 1069–1083 doi: 10.1098/rstb.2006.1846  -criticises Vinther and Nielsen (2005) idea that H. is mollusc, and a lot of other good stuff. Full PDF!
  • Simon Conway Morris and Jean-Bernard Caron, Halwaxiids and the Early Evolution of the Lophotrochozoans, Science 2 March 2007, Vol. 315. no. 5816, pp. 1255-1258, DOI: 10.1126/science.1137187 - and Oikozetetes, a new Burgess halkieriid.
    • This paper also mentions the role of the siphogonuchitids in the phylo analysis, mainly as a complication - we may need to get a handle on these before getting into serious phylo. Guess what? There's no WP article on siphogonuchitids!

-- Philcha (talk) 08:24, 2 August 2008 (UTC)


Less direct / immediately usable:

Article title[edit]

At present Halkieriid redirects to Halkieria, which was fair enough when H. evangelista was the only well-studied species. However Porter, S.M. (May 2004). "Halkieriids in Middle Cambrian Phosphatic Limestones from Australia". Journal of Paleontology 78 (3): 574–590. doi:10.1666/0022-3360(2004)078<0574:HIMCPL>2.0.CO;2. Retrieved 2008-08-01.  reports 1 new genus plus 2 other unclassified species from Mid-Cambrian rocks of the Georgina Basin in Australia. I suggest we make Halkieriid a separate article and move as much content as possible to it – even if we find that Halkieria should then redirects to Halkieriid. -- Philcha (talk) 15:39, 1 August 2008 (UTC)

Sounds an eminently sensible idea. I'd vote for moving this page to Halkeriid and redirecting the genera there, to avoid unnecessary duplication. Martin (Smith609 – Talk) 18:49, 1 August 2008 (UTC)
Good point about redirecting other genera - Halwaxiida has a red link to Australohalkieria.
In fact Halwaxiida looks like a good place for the heavy phylogenetic lifting - if so, a certain bold gang should liberate appropriate it. -- Philcha (talk) 23:06, 1 August 2008 (UTC)
Eventually, we should have the other genera on their own articles, while keeping all of the specifically Halkieria-pertinent information here..--Mr Fink (talk) 22:33, 1 August 2008 (UTC)
Long-term you're right - but it might be a very long time before anyone finds sufficiently complete specimens of the other genera to justify separate articles; AFAIK only H. evangelista is fairly complete and the others are defined on collections of sclerites that resemble each other and differ from H. evangelista’s. -- Philcha (talk) 23:06, 1 August 2008 (UTC)
True, it's just that I think it would be unnecessary to turn Halkieria into a redirect while we expand on Halkieriid and Halwaxiida.--Mr Fink (talk) 23:08, 1 August 2008 (UTC)
While I haven't workd right through all the sources I've identified, I'd expect the Halkieria-specific content of the current article to double at most. If Halwaxiida does the heavy phylogenetic lifting, the corresponding part of Halkieriid / Halwaxiida is likely to get shorter, leaving a family-level article of quite reasonable size. Since we need the family-level article to accommodate the fragmentary genera, I think that for now it should handle the descriptions of all genera. Later if knowledge of any of the genera — most probably Halkieria — increases enough to justify its own article, we can split it out. -- Philcha (talk) 23:21, 1 August 2008 (UTC)

Thoughts[edit]

Good work on this article! I'm not familiar with the subject at all, but nothing strikes me as particularly untoward. One thing that doesn't sit too comfortably is your description of cladogram stability - you say "it falls apart if the organisms' characteristics are changed even slightly"; the lay reader may not understand how characters of a fossil organism can be changed. Perhaps "interpreted differently" or "the range of characters used is modified" would give a better reflection of the nature of the uncertainty.

It would be nice to get an expert opinion on the article, although I suspect it might be difficult to find one - perhaps a peer review would be helpful. I am guessing you are still working out the best place to locate the cladistic discussion, although I think there's a decent case for including the current discussion as is in this article. As ever, a GA reviewer could probably pick up on a couple of stylistic points, but otherwise it's looking like a pretty good job - I think you're ready to start on the lead!

Martin (Smith609 – Talk) 20:38, 15 August 2008 (UTC)

Re "it falls apart if the organisms' characteristics are changed even slightly", SCM & Caron write "is not robust", and I had to figure out a paraphrase that would be more intelligible. I took "is not robust" to refer to sensitivity testing.
In Halwaxiida I rephrased it:
They concluded that "Hypothesis 1" fitted the available data better, but fell apart if there were minor changes in the characteristics used.
The problem is that "is not robust" carries a large load of concepts relating to the use of mathematical models, especially for paleontology. Explaining it properly for non-specialists would require a paragraph in its own right and would probably constitute WP:OR or, if we found an appropriate methodological citation, WP:SYNTH.
"fell apart" is probably not the right phrase. Empirically, one might see large changes in output (cladogram structure) as a result of small changes in inputs (characters used, values or weightings of these characters, etc.).
Any ideas on how to get round this? -- Philcha (talk) 21:54, 15 August 2008 (UTC)
Hmm.. How about something along the lines of "the data provide only weak support for / only weakly constrain either cladogram"? Martin (Smith609 – Talk) 08:40, 16 August 2008 (UTC)
Thanks, but I don't think that quite what SCM & Caron meant. It's actually more complicated, because my understanding (??) is that the 2 cladograms arise from setting PAUP 2 different constraints about the positions of Kimberella and Odontogriphus, and I've seen articles say that PAUP is very sensitive to that, especially on the "maxiumum parsimony" setting.
My understanding (?? again) is that SCM & Caron found "Hypothesis 1" a better fit to the data, but "not robust", and that's why I thought they were talking about sensitivity analysis. -- Philcha (talk) 13:35, 16 August 2008 (UTC)