Talk:Small shelly fauna

Comments pasted in from user Talk pages
The following copied here from user Talk pages -- Philcha (talk) 20:18, 31 July 2008 (UTC)

This looks pretty comprehensive now, although I'm certainly no expert. The one criticism I'd make is that it's a little piecemeal. I'm not sure if there's much that can be done about this – the list of different shells is by its nature very bitty. But I do think the structure needs a bit of a look at – I'd put the list later and introduce the concept of skeletonisation, and perhaps their significance, sooner. It doesn't really flow or "tell a story" at the moment. And one other thing – the iron pyrite gastropod is an very interesting aside, but does it really have a place in this article? Perhaps Exoskeleton would be a more worthy home. (Oh – you got there first!)

Keep up the good work,

Martin  (Smith609 – Talk)  14:01, 31 July 2008 (UTC)


 * Thanks for the comments, I'll take seriously your proposal that the big ideas should come first in Small shelly fossils. The point of the snail with the pyrite mini-skirt is that it uses a "traditional" material for the usual shell and what's handy for the new-fangled pelmet. Does that not come over clearly enough? -- Philcha (talk) 15:47, 31 July 2008 (UTC)


 * I'm just not sure it's 100% relevant – maybe it's a flow issue but it strikes be as misplaced. If you want to keep it then don't let me stop you! :Martin  (Smith609 – Talk)  16:02, 31 July 2008 (UTC)


 * I've restructured Small shelly fauna as you suggested. Time to get it promoted? -- Philcha (talk) 17:56, 31 July 2008 (UTC)


 * I'm taking a more thorough look through now, and think I would like to see the "minerals used" section expanded a little. I guess that's why the mollusc stood out – you've given the reader some good information about a living creature, but very little about the topic of the article.  Why would calcite be easier to precipitate than aragonite, and what would cause the regional differences you seem to have inferred?  How did the organisms precipitate the minerals in the first place? What are the roles of structural proteins? Martin  (Smith609 – Talk)  19:53, 31 July 2008 (UTC)
 * I'm not sure about the relevance of how variations in ocean chemistry make it easier to precipitate calcite or aragonite. In fact I don't understand why organisms apparently prefer aragonite in favourable chemical situations, or what general principle of evolution it highlights. So in oceano-chemical Philistine mode I simply said sometimes they use this, sometimes that. Can you explain it to this ignoramus in words of 1 syllable?
 * OTOH to me the snail with the pyrite mini-skirt makes a point about conservatism re existing features versus opportunism re new features. -- Philcha (talk) 20:33, 31 July 2008 (UTC)


 * Also, I'm curious as to how "non-mineralised tubes" fall under the juristiction of the small shelly fossils? Martin  (Smith609 – Talk)  20:07, 31 July 2008 (UTC)
 * (P.S. done reviewing)
 * Good question. Bengtson's article was "Small Skeletal Fossils", and "non-mineralised tubes" fall into that category, but probably not into small shellies. It's all the fault of these boring predators that didn't fancy Sinotubulites. I suppose If I delete "non-mineralised tubes" and the description of Sinotubulites I could get away with no further description of Sinotubulites in the bit about boring predators' attacks on Cloudina and their distaste for Sinotubulites. What do you think? -- Philcha (talk) 20:33, 31 July 2008 (UTC)
 * You could probably do away with the generic name altogether and just say "other organisms" where necessary. Martin  (Smith609 – Talk)  19:06, 1 August 2008 (UTC)

Evolutionary significance
I'm still a little concerned that outlining Budd's argument in so much detail risks appearing to conflict with Kimberella - Budd doubts whether any pre-Cambrian critter were triploblastic, mainly on methodological grounds ("parsimony"), while AFAIK no-one has recently explicitly questioned that Kimberella is a genuine triploblastic bilaterian. The origins of triploblastic bilaterians are to complex an issue for Small shelly fauna to go into, e.g. which came first, triploblasts or bilaterians?

I'm also concerned that readers whose mental tool-kits don't already include cladograms will be confused by the notion of different levels of stem group, which Budd's analysis implies. I'll see if I can come up with a suitable annotated image that doesn't occupy half the page. -- Philcha (talk) 12:13, 1 August 2008 (UTC)

Which timeline?
reports 1 new genus plus 2 other unclassified species from Mid-Cambrian rocks of the Georgina Basin in Australia – so a family that produced many SSFs has been found later than the range of the current SSF timeline. I'm beginning to think Small shelly fauna should use the Halkieria timeline, which should then be extended to 585 MYA to include all Ediacara biota). -- Philcha (talk) 15:48, 1 August 2008 (UTC)


 * Just a guess, but were the sclerites of the post-SSF Halkeriids not preserved as small shellies, due to the closure of the taphonomic window?  Hence the animals were still about without appearing as SSFs. Martin  (Smith609 – Talk)  19:05, 1 August 2008 (UTC)


 * It appears the closure of the phospatisation window was protracted and geographically patchy: "Phosphatized fossils occur throughout the Monastery Creek Phosphorite Member" (Porter, 2008) -- Philcha (talk) 12:54, 17 August 2008 (UTC)


 * What's the link for Porter 2008 again? I can't find it anywhere. Martin  (Smith609 – Talk)  13:03, 17 August 2008 (UTC)


 * It would help if I got the date right - Porter (2004) above, mea culpa. (2008 was on similarity of halkiierid and chancelloriid sclerites) -- Philcha (talk) 13:26, 17 August 2008 (UTC)

Rename this article to correctly "Small shelly fossils"
Real and typical meaning of the term SSF it is Small Shelly Fossils. There is no specifically united "small shelly fauna" what once has appeared and disappeared.

Small Shelly Fossils assemblage(s) = small shelly fauna(s). The Small Shelly Fossils form several small shelly fossils assemblages (small shelly faunas).

SSF=Small Shelly Fossils has priority over SSF=small shelly fauna.

Small skeletal fossils are present in sediments of the whole Phanerozoic, but only in Late Precambrian-Early Cambrian these fossils are dominating and are of great importance to stratigraphy. Therefore the term "Small Shelly Fossils" is used only for Late Precambrian-Early Cambrian.

I consider that it is necessary rename this article: "Small shelly fauna" to correctly "Small shelly fossils".

Aleksey (Alnagov (talk) 12:55, 11 April 2009 (UTC))


 * Small shelly fossils redirects here. If this article were renamed, Small shelly fauna would have to redir to it - not worth the trouble as only WP editors would notice the difference.
 * The article mentions that originally the term applied only to fossils of Tommotian Age, but some authors have widened the meaning to incl e.g. Ediacaran Cloudina and some post-Tommotian fossils. --Philcha (talk) 16:54, 11 April 2009 (UTC)


 * I've seen SSF stand for both. 'Fauna' has a slightly larger scope as it allows speculation on the lifestyles of the animals while they were alive.  I can't see a strong case for moving to fossils, especially when 'SS fossils' redirects here. Martin  (Smith609 – Talk)  16:00, 12 April 2009 (UTC)


 * OK. Perhaps it is really senseless. I have reviewed articles about SSF in Russian and there name/phrase "мелкораковенная фауна" (the exact translation from Russian - "small shelly fauna") is used for rich assemblage/complex of small shelly fossils (Nemakit-Daldynian – Early Botomian -- less for Botomian-Toyonian for the objective reasons). In articles in Russian the English abbreviation "SSF" is often used but only as "small shelly fossils" for fossils (Early Cambrian -- for classical Early Cambrian small shelly fossils from Early Cambrian,…). Aleksey (Alnagov (talk) 18:54, 12 April 2009 (UTC))

Megabias
I reverted your paragraph about megabias as sections "Occurrence" and "Mode of preservation" already describes the unexpectedly late halkieriids from Australia, using citations by Porter and a couple of other authorities. --Philcha (talk) 19:08, 14 October 2010 (UTC)

Question
What's the relationship (if there is one) between the small shelly fauna and the Ediacara biota? —Preceding unsigned comment added by 71.142.240.36 (talk) 11:35, 13 December 2010 (UTC)


 * The terms Small shelly fauna and Ediacara biota are both ambiguous. See the timeline at Ediacaran period.
 * Most of the "Ediacara biota" fossils come from the range 555MA to 542MA and include animals that look like possible ancestors of Cambrian animals (Kimberella was a bilaterian and possibly a mollusc; Arkarua may have been an echinoderm; etc.), some possible animals with "symmetry of gliding reflection" (for example Yorgia) and some organisms whose classification is unclear.
 * Most of the fossils of the small shelly fauna come from the Tommotian stage of the Cambrian, but Bengston included in "SSF" Ediacaran fossils like Cloudina and post-Tommotian fossils like Microdictyon from the Maotianshan shales lagerstätte - but Microdictyon is now regarded as an "armoured worm". On the other hand some small shelly fauna fossils are easily diagnosed, for example Helcionellids was snail-like molluscs.
 * Confusing, isn't it? --Philcha (talk) 22:25, 15 December 2010 (UTC)