Talk:Fossils of the Burgess Shale/GA1

GA Review

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Reviewer: hamiltonstone (talk) 23:04, 11 October 2009 (UTC)

I will undertake this review. The article is neutral, stable and generally well written. The scholarship is of a very high standard. The large range of images appears to be in order; Kudos to the several creators of original work, including nominator Philcha, for their commitment to creating and providing such good illustration of an article.

Specific points

• First sentence of the lead has too many clauses and should not begin "These fossils". I have attempted an improvement.
• Lead text has some idiosyncratic writing "rather thin", "fairly tough", "largely regarded". These expressions lack precision. Choose more concise language, and deal with the nature of qualifiers in the body text. For example, say simply "thin" in the lead, then explain how thin - or how their thickness compares with others - in the body text.
• the fossils "were stored on high shelving in back rooms". It isn't entirely clear where. Although Walcott was with the Smithsonian, it hasn't been made clear that he was undertaking the work for the Smithsonian and that this was/is therefore where his collection of fossils was/is kept (and in any case, a lay person won't know where that would be - a city in the US? Which one?)
• "Between 1962 and the mid-1970s Alberto Simonetta re-examined some of Walcott's collection and suggested some new interpretations". We haven't been told what the original interpretations were, nor is the nature of these re-interpretations outlined. A few extra sentences are I think in order in this section, including a para that sets out in simple terms Walcott's (and his colleagues') initial interpretations. This would set the scene more effectively.
• There is an issue - at least in my browser - with the appearance of the key to image "File:Crown n Stem Groups 01.png", whereby the text "crown group" is partly obscured by "stem group". This may need tweaking.

More anon. hamiltonstone (talk) 23:04, 11 October 2009 (UTC)

• I provided some more context for lay readers regarding recent finds - I hope my wording doesn't make experts wince.

More anon. Sorry for the slow and fragmentary progress. hamiltonstone (talk) 16:53, 13 October 2009 (UTC)

• At the end of the geology section is this phrase: "during which the environment was essentially stable". The preceding sentences have created a picture of a physical environment that was anything but stable (mudslides etc that "abruptly washed large volumes of mud off the platform"). Is the intention to say the climate was essentially stable?
• A tedious suggestion for which I apologise: some refs have retrieval dates, some don't, and not all are in the same date format. Improved consistency would be good.The refs are otherwise of an exceptionally high standard.

More anon. hamiltonstone (talk) 17:31, 14 October 2009 (UTC)

Lead

• Thanks for fixing the "too many clauses " - and for making me notice that I omitted the initial discovery in 1886, which I've added! --Philcha (talk) 08:04, 12 October 2009 (UTC)
• Re thickness of fossil layers, we already have the total thickness. If I added the avg thickness of individual layers the result would be "The fossil beds are in a series of shale layers, averaging 30 millimetres (1.2 in) and totalling about 160 metres (520 ft) in thickness, that built up beside the face of a high undersea limestone cliff." What do you think? --Philcha (talk) 08:04, 12 October 2009 (UTC)

• Better. How about "The fossil beds are in a series of shale layers, averaging 30 millimetres (1.2 in) and totalling about 160 metres (520 ft) in thickness. These layers were deposited against the face of a high undersea limestone cliff." hamiltonstone (talk) 17:27, 14 October 2009 (UTC)

Done, thanks! --Philcha (talk) 17:31, 14 October 2009 (UTC)

Discovery, collection, and re-examinations

• Added (on high shelving in back rooms) "at the Smithsonian Institution" --Philcha (talk) 08:04, 12 October 2009 (UTC)
• Walcott's and Simonetta's interpretations are quite different from and superseded by interpretations starting by Whittington & co's work in the 1970s.
  • Walcott, like his contemporaries, assumed the fossils represented members of known modern taxa - the article notes that his contemporaries accepted Walcott's analyses. But work from Whittington onwards made it clear that these are not known modern taxa - their initial conclusions pointed towards to whole major that were previously unknown, including unfamiliar phyla. Then Briggs and Whittington starting using the cladistic approach, which led to seeing these fossils as evolutionary "aunts and cousins" of modern taxa. --Philcha (talk) 08:04, 12 October 2009 (UTC)
  • Simonetta's interpretations did not challenge Walcott's approach but added many details in reconstructions. Gould described these as "aethestecially lovely but fanciful" (Wonderful Life p.129), and Whittington commented, "the evidence for them was not brought out clearly" (paleo-diplo-speak for the same opinion Gould expressed forthrightly). The article's mention of Simonetta is intended to show how little interest there was in the Burgess fossils from the early 1930s to the start for Whittington's work. --Philcha (talk) 08:04, 12 October 2009 (UTC)

OK, I think I see what you are trying to do here. What seems needed is a discussion of the interpretation of the fossils, which should begin with Walcott's now superceded analysis. This could be achieved in at least a couple of different ways:

• by modifying ""Discovery, collection, and re-examinations" to include a historical summary of interpretations - something very much like the two points you made above; or
• Shorten "Discovery, collection, and re-examinations" to just outline the discovery and collection of fossils, then move on to the geology, and deal with all interpretations, both early and contemporary, in "Theoretical significance", perhaps re-badging the section "Interpretation and theoretical significance". hamiltonstone (talk) 16:42, 13 October 2009 (UTC)

Specific fossils are discussed in Fossils_of_the_Burgess_Shale#Notable_Burgess_Shale_fossils, including Anomalocaris (an amusing detective story), Opabinia (classified in the 1970s as part of a novel phylum, more recently as a fairly close relative of arthropods) and an outline of the messy halwaxiid debate including Wiwaxia, Orthrozanclus and Odontogriphus. The debate about the "halwaxiids" have been going since 1990, and can only be outlined here - must get back to try to make more sense of Halwaxiida some time.

BTW your edit about "a small sea creature Orthrozanclus, possibly a mollusc or a polychaete worm" goes a little further than Conway Morris & Caron (2007) say. They present 2 possibilities about the halwaxiids, including Orthrozanclus: (a) they are "cousins" of molluscs and slightly more distantly related to annelids and brachiopods; (b) conversely, halwaxiids may be "cousins" of annelids and brachiopods and slightly more distantly related to molluscs - but SCM & JBC do not suggest that any halwaxiid is specifically closer to annelids than to brachiopods. The "Notable Burgess Shale fossils" section is circumspect about this, saying "Orthrozanclus was also drawn into the complex debate about whether Wiwaxia is more closely related to molluscs or to polychaete worms".

My last version of "Discovery, collection, and re-examinations" uses Sanctacaris, Othrozanclus, etc. to illustrate that discoveries are still being be made in the Burgess. I'm not at all convinced that going into more detail about Walcott's, Simonetta's and other pre-1970s interpretations in this article would help readers:

• This article gives a brief overview of some fossils, usually those that have aroused debate. There are a lot more, but list them would make this article rather long (and it's already not small).
• For fossils interpreted by Walcott, the articles on individual fossils are a better place to mention Walcott's interpretations, e.g. at Opabinia or Hurdia (which did not make the cut for this article). --Philcha (talk) 18:17, 13 October 2009 (UTC)

• I don't think i made my intention clear. You are quite right that the interpretation of individual fossils would be better treated elsewhere. But in an article on "fossils of the Burgess Shale", some text about how the original discoverer / collector interpreted them in general is very much in order. (BTW, when one considers the significance of the Burgess, isn't it amazing that "As of 2008 only two in-depth studies of the mix of fossils in any part of the Burgess Shale had been published"?! Not querying it, just found it very surprising :-)) hamiltonstone (talk) 17:23, 14 October 2009 (UTC)

Back to the critters you commented on in section "Discovery, collection, and re-examinations", how about "led to the description in the 1980s of Sanctacaris, an arthropod, and of Orthrozanclus in 2007, which became part of the debate about the relationships of the halwaxiids to modern lophotrochozoan invertebrates" (with additional refs, mainly those used later in section Fossils_of_the_Burgess_Shale#Notable_Burgess_Shale_fossils). --Philcha (talk) 08:36, 14 October 2009 (UTC)

The issue for me here is accessability to the lay reader. I'm not relly fussed what the descriptions are (for example, I just took "possibly a mollusc or a polychaete worm" from the linked WP article). I'm happy for it to be corrected I just wanted some plain-ish English words to tell the reader what these discoveries were in general terms. Turning to your last proposal, it is an improvement but "...the relationships of the halwaxiids to modern lophotrochozoan..." gets us back to the same challenge. Why not just "...the [evolutionary/similar word] relationships between the many different mid-Cambrian period life forms..." or similar. hamiltonstone (talk) 17:23, 14 October 2009 (UTC)

The problem is that the halwaxiid issue is complex. As I said, mollusc vs polychaete is inaccurate. "relationships between the many different mid-Cambrian period life forms" is inaccurate the other way - the issue does not involve the majority of Burgess taxa, e.g. excludes arthropods and their "cousins", priapulids, chordates (if the candidates actually were chordates), sponges, echinoderms, etc. "Lophotrochozoan" is accurate. How about "... debate about the relationships of the halwaxiids to modern lophotrochozoa (the super-phylum that includes molluscs, annelids, brachiopods and a few other phyla)" --Philcha (talk) 17:39, 14 October 2009 (UTC)

• That's a step forward, but "halwaxiids" is just as much the problem, so it too needs explanation, and things may get cumbersome. I know you're going to hate this, but what about ""relationships between some of the many different mid-Cambrian period life forms found in sections of the Burgess Shale" ;-) ? hamiltonstone (talk) 17:45, 14 October 2009 (UTC)

"relationships between some of the many different mid-Cambrian period life forms" could include all the taxa listed in my last comment, most of which have nothing to do with the debate in question. "lophotrochozoa" is a complex concept, mainly based on molecular phylogeny analyses (comparisons of DNA) on modern animals (molluscs, annelids, brachiopods, phoronids, etc.), and I see no prospect of shrink-wrapping this to the brevity required in an overview like Fossils of the Burgess Shale. "halwaxiids" is not quite complex but still probably too much to shrink-wrap. "relationships between some of the many different mid-Cambrian period life forms" also gives no wikilinks thaat hardy readers could use to find out more about these critters.

How about "... and of Orthrozanclus in 2007, which has strong resemblances to both Wiwaxia and Halkieria, and became part of the debate about whether these animals were more closely related to molluscs or to annelids."(with additional refs, mainly those used later in section Fossils_of_the_Burgess_Shale#Notable_Burgess_Shale_fossils)

Except that's a bit of mouthful, and the same sentence starts with Sanctacaris. Possible alternative: "The continuing search for Burgess Shale fossils since the mid-1970s has led to the description of an arthropod Sanctacaris in the 1980s[11] and in 2007 of Orthrozanclus, which looked like a slug with a small shell at the front, chain mail over the back and long spines round the edges.[ref]" That gives a mental picture and a hint of the weirdies to come, and the evolutionary complexities are covered in Fossils_of_the_Burgess_Shale#Notable_Burgess_Shale_fossils. --Philcha (talk) 08:20, 16 October 2009 (UTC)

OK, let's give that a shot, and see how it looks when we're done. hamiltonstone (talk) 11:15, 16 October 2009 (UTC)

Done. --Philcha (talk) 12:25, 16 October 2009 (UTC)

How the fossils were preserved

• I'm a little confused by the thread of argument across the first two paras of this section. Half way through para 1 it appears we are being introduced to Caron and Johnson's thesis that burial is more or less in situ. The remaining text of para 1 presents some of the evidence, including: "Other evidence for burial where the animals had lived includes the presence of tubes and burrows". Para 2 does not begin with a lead sentence in the normal manner - a sentence that tells us what the para is going to be about. It reads as though a fairly arbitrary break has been inserted from the previous para. However, the first sentence includes the fact that "no burrows under the sea-floor have so far been found in the Burgess Shale". This appears to contradict the Caron and Johnson evidence just above. Is this second para presenting a contradictory thesis to C&J's? Not obviously: shortly afterward, we are told of a fact "...which suggests they were not transported far if at all". Can you have a shot at re-organising this a little, perhaps including some more signposting of argument / counterargument? Para 1 begins doing this very well - the problem is para 2 I think.

Unfortunately academics writing for other academics often omit the "signposting of argument / counterargument", expecting their readers pick up without effort what they regard as very simple logic. The logic is: (a) It was the corpses were deposited in anoxic conditions, otherwise bacteria would have the remains before they could fossilise; (b) Since the animal can't have lived in anoxic conditions, they must have been transported before burial; (c) Caron & Jackson undermined this implication by showing that at least some animals lived where they were then buried (denying the consequent); (d) therefore (next para) they need to find conditions where the non-transported animals could have lived (i.e. oxic) but could have been fossilised (possibly buried in adjacent anoxic conditions) - and one solution is oxic water above the seabed but anoxic water permeating the sediment in which the remains were buried and fossilised.

While I don't think I can signpost quite so explicitly without running into WP:V, I think I can make it clearer by rearranging a bit. Try this:

The processes responsible for the exceptional preservational quality of the Burgess Shale fossils are far from clear. The interpretation of what is preserved depends partly on two issues that are interlinked: whether the animals were buried where they lived, or washed long distances by sediment flows; and whether the water at the burial sites was anoxic or provided enough oxygen to sustain animals. The traditional view is that soft bodies and organs could only be preserved in anoxic conditions, otherwise oxygen-breathing bacteria would have made decomposition too rapid for fossilization. This would imply that the sea-floor animals could not have lived there.

However, in 2006 Caron and Jackson concluded that some of the sea-floor animals were buried where they lived. Many fossils represented partially-decayed soft-bodied animals such as polychaetes, which had already died shortly before the burial event, and would have been fragmented if they had been transported any significant distance by a storm of swirling sediment. Other evidence for burial where the animals had lived includes the presence of tubes and burrows, and of assemblies of animals preserved while they fed – such as a group of carnivorous priapulids clustered round a freshly-moulted arthropod whose new cuticle would not yet have hardened. Fossilized swimming organisms were also buried immediately below where they lived. Some fossils, such as Marella, are almost always the right way up, which suggests they were not transported far if at all. Others, such as Wiwaxia, are often at odd angles, and some fossils of animals with shelly or toughened components very rarely contain remains of soft tissues. This suggests that genera were transported by different distances, although most were buried where they had lived.

The typical wrinkled "elephant skin" texture of microbial mats

Fossil tracks are rare and no burrows under the sea-floor have so far been found in the Burgess Shale. These absences have been used to support the idea that the water near the sea-floor was anoxic. However it is possible that the water just above the sea-floor was oxygenated while the water in the sediment below it was anoxic, and also possible that there simply were no deep-burrowing animals in the Burgess Shale. Fossils known as Girvanella and Morania may represent members of microbial mat communities. Morania appears on about a third of the slabs Caron and Jackson studied, and in some cases presents the wrinkled "elephant skin" texture typical of fossilized microbial mats. If such mats were present, they may have provided food for grazing animals and possibly helped to preserve soft bodies and organs, by creating oxygen-free zones under the mats and thus inhibiting the bacteria that cause decomposition.

Is that an improvement? --Philcha (talk) 13:09, 16 October 2009 (UTC)

• Yes, but it has two issues, one old and one new. The issue that is still a problem is the apparent contradiction about burrows: "Other evidence for burial where the animals had lived includes the presence of tubes and burrows..." yet "Fossil tracks are rare and no burrows under the sea-floor have so far been found". These cannot both be correct. The new issue is that the para that begins "Fossil tracks are rare..." Needs an introductory sentence telling the reader what the subject of this paragraph is.

The anoxic/oxic and indigenous/transported issues are like simultaneous equations in high school algebra. You can solve either on its own, you need to produce a partial solution to one, feed that into the 2nd, then use the solution to the 2nd to finish the solution of the 1st.

Coming back to the issues you raised:

• "tubes" generally refers to habitations standing above the surface, as in modern Tube worms and pre-Burgess Cloudina. "burrows" can include horizontal just under the surface, as well as deeper burrows. To put it in perspective, Trace fossils and substrates of the terminal Proterozoic–Cambrian transition: Implications for the record of early bilaterians and sediment mixing (2002) says some Early Cm burrows at other sites are 1-2cm, while The Trace Fossil Record of the Burgess Shale (Mangano & Caron, conference presentation Aug 2009; will become a publish paper in time) says most Burgess burrows are less than 3mm deep. I would not like to cite the conference presentation until it becomes a paper, but Caron & Jackson (2006) on Burgess taphonomy (how things were fossilised), which is cited, also notes the absence of deeper burrows below the surface of the seafloor. How about "... includes the presence of tubes and shallow burrows ..." and "and so far no burrows deeper under the sea-floor have been found"? --Philcha (talk) 12:15, 17 October 2009 (UTC)
• The first para deals with the indigenous/transported "equation". The 2nd para, "Fossil tracks are rare..." is about the 2nd "equation", anoxic/oxic. Mangano & Caron (conference, Aug 2009) regards the shallowness of Burgess burrows as evidence that the water was oxic down to the surface of the seabed but changed sharply to anoxic below the surface. That would reconcile the evidence of local animals with the fact that anoxic conditions preserve buried remains. Although I would not want to cite that, Caron & Jackson (2006) on Burgess taphonomy suggest oxic water above the seafloor and anoxic below. As an introductory sentence how about "The presence of animals at the sites just before burial events suggest that the water there was oxygenated. However, fossil tracks are rare ...". --Philcha (talk) 12:15, 17 October 2009 (UTC)

• I think the "How the fossils were preserved" section may be back to front. I suggest it should begin with what is the second last para (ie. starting "Burgess shale type preservation is defined as..."), then have paras 1, 2, 3, 4, while the current last para stays as the last para. This revised order would mean that we are first introduced to the nature of the preservation before moving to the more complex discussion of how this came to happen.

  I think it would be a mistake to separate the significant features of Burgess-type preservation (fairly hard parts as films, very soft parts in 3-D, rest lost) from the periods in which Burgess-type preservation occurred. At present I prefer the setting (anoxic or not, local or transported) before the details of preservation, as I think that flows better from the geological setting in the prev section. I suggest we re-visit this after looking at how to handle anoxic or not, local or transported. --Philcha (talk) 12:34, 16 October 2009 (UTC)

• In other respects, this section is good.

• • Re. the 'No vertical fossils in BS' statement, see Mángano, Gabriela; Caron, Jean-Bernard (August 2009). "The Trace Fossil Record of the Burgess Shale" (PDF). In Smith, Martin R.; O'Brien, Lorna J.; Caron, Jean-Bernard (eds.). Abstract Volume. International Conference on the Cambrian Explosion (Walcott 2009). Toronto, Ontario, Canada: The Burgess Shale Consortium (published 31 July 2009). ISBN 978-0-9812885-1-2.. Martin (Smith609 – Talk) 01:38, 17 October 2009 (UTC)

Hi, Martin, welcome back. I guess you mean "No vertical trace fossils in BS". Re Mangano & Caron, I'd prefer to wait until they actually publish, as there may be changes compared with the conference proceedings. However it looks like they're highlighting a significant point, e.g. Trace fossils and substrates of the terminal Proterozoic–Cambrian transition: Implications for the record of early bilaterians and sediment mixing (2002) says some Early Cm burrows at other sites are 5-10 times as deep ("1-2 cm") as those Mangano & Caron found. --Philcha (talk) 05:51, 17 October 2009 (UTC)

Faunal composition

• "...more recent than the Phyllopod Bed (abbreviated "GPB")" Should this be Greater Phyllopod Bed?

Thanks, done. --Philcha (talk) 13:51, 16 October 2009 (UTC)

• "Conway Morris found that the shelly fossils in Walcott's Phyllopod Bed were about as abundant as in other shelly fossil deposits, but accounted for only 14% of the Phyllopod Bed fossils." This confused me. First, I thought that, in order for us to follow the subsequent arithmetic, we first need to know what the typical abundance is. But then I saw a different problem. The article uses four different descriptors for particular layers, and in this section it appears absolutely crucial to use exactly the right one at each point. The four are:
  • Walcott's Phyllopod Bed
  • Phyllopod Bed
  • Greater Phyllopod Bed
  • GPB.

In the preceding quote, it is not clear what "Phyllopod Bed" is. At least, I think that is why I'm confused :-)

"Phyllopod Bed" = Walcott's, about 2m high. "Greater Phyllopod Bed" aka "GPB" is a 70-metre set of layers of which Walcott's "Phyllopod Bed" forms the top 2m. After introducing "GPB" I (hopefully) always "GBP" for the big series and "Phyllopod Bed" for the smaller one. The survey of fauna by Conway Morris in 1986 covered the "Phyllopod Bed", while Caron & Jackson (2008) covered the GBP, but included some analysis of the "Phyllopod Bed" for comparison with Conway Morris (1986). Ain't geology and paleontology fun! --Philcha (talk) 13:51, 16 October 2009 (UTC)

• The line of argument here probably needs another bit of clarification. It talks about "shelly fossils". I presume therefore there are other sorts of fossils. That is, there are non-shelly creatures that are capable of fossilisation. However, the para appears to use a multiplier to estimate levels of biodiversity, and implies this is done by treating shelly fossils in contrast to creatures that "are unsuitable for fossilization". Hmm. I don't know if I'm going to be able to explain myself here. Might have to try again tomorrow.

Aaargh! Another case where the academics take it for granted, so sources for such "elementary logic" are scarce. "shelly fossils" = biomineralized, i.e. reinforced with minerals as in e.g. bivalves and many gastropods. These are the items most likely to be preserved in marine environments (in terrestrial environments, large skeletons of vertebrates are the dominant animal fossils). Non-mineralised fossils are usuually found in exceptionally favourable conditions.

Conway Morris (1986) found the same abundance of mineralised fossils in the Phyllopod Bed (exceptionally favourable conditions for nonmineralised fossils) as in other deposits. However in non-exceptional deposits only mineralised fossils survived. OTOH in exceptionally favourable beds such as the Phyllopod (and GBP, but CM did not cover this) nonmineralised account for 86% of fossil animals. He therefore reasoned that other non-exceptional deposits originally had the same abundance of non-mineralized animals as in the exceptionally favourable ones - but have not been found there becuase conditions there was poor for fossilising non-mineralized animals. I think a prettified version of CM's reasoning could just about squeeze past WP:V. However the preceding background about "shelly fossils" being much more easily fossilised than nonmineralised ones woudl have to endure 2 ordeals, by WP:V and WP:SYN. --Philcha (talk) 14:12, 16 October 2009 (UTC)

• The rest of "faunal composition" is good.

More anon. hamiltonstone (talk) 11:45, 16 October 2009 (UTC)

Notable Burgess Shale fossils

• "...resulting in a frank exchange of views". Either outline the frank exchange, or omit the remark.

The details are not important to go into here. What's more interesting is that it was remarkably heated by the standards of scientific journals. It's a midly example example that scientists are human too - and readers need a laugh after the heavy stuff in the first half of the article. --Philcha (talk) 13:27, 21 October 2009 (UTC)

• I don't think it's that heavy going, but in any case, the readers won't get a laugh unless the point is illustrated with some choice words. My suggestion stands :-) hamiltonstone (talk) 22:03, 21 October 2009 (UTC)

The last ref (Caron, Scheltema & co, 2007) quotes "Many of Butterfield’s misconceptions might well have been avoided had he taken the opportunity to examine all the new material that formed the basis of our study ...". A passage from their para is blunter but longer: "Unfortunately, most of Butterfield’s contentions are founded on questionable assessments of the fossil material and on assumptions about preservational biases. While his bold statements may sound reasonable to an audience unfamiliar with the taphonomic complexities of the Burgess Shale, Butterfield fails to present any credible new evidence to support them. Regrettably, his arguments serve only to obscure discussions on the correct phylogenetic placement of these organisms." This is undiplomatic by scientific standards, but not great comic dialogue. IMO "a frank exchange of views" is more fun as it leaves more to readers' imagination. --Philcha (talk) 22:49, 21 October 2009 (UTC) (typo fixed --Philcha (talk))

• "Three jawless fish have been found among the Chengjiang fossils, which are about 17 million years older than the Burgess Shale" This sentence appears as a non-sequitur at the end of the last description. I assume the implicit point is that the date for these fish supports the possibility that these other fossils can be chordates, but this needs to be spelled out.

May be I'm getting too close to the subject, but "fish" implies craniate, which implies chordate. The history of the subject is that Pikaia was a big deal after being diagnosed as a chordate in the mid-1970s, but has been up-staged by the jawless fish from Chengjiang, where the fossils beds are about 17M years earlier. I could expand it to e.g. "While Pikaia was celebrated in the mid-1970s as the earliest known chordate,[ref a page from Wonderful Life], three jawless fish have been found among the Chengjiang fossils, which are about 17 million years older than the Burgess Shale[existing ref Conway Morris 2008)]--Philcha (talk) 13:31, 21 October 2009 (UTC)

Fish implies chordate, and that itself may need spelling out (we're both perhaps too close to the subject in that regard), but the thing that is implicit and really needs spelling out is the point about the time frame etc. Your proposal is an improvement. Put it in, and i'll have a read-through at the end and see if it solves the problem. hamiltonstone (talk) 22:03, 21 October 2009 (UTC)

• The rest of the section is good.

More anon - hopefully not as anon as last time :-) hamiltonstone (talk) 12:16, 21 October 2009 (UTC)

Theoretical significance

• This section barely mentions the Burgess Shale fossils. It gives multiple paragraphs of background before we get there, and when we do get there, it doesn't seem to be about the Burgess fossils to great degree. Of all the sections, this one needs the most work. It absolutely must begin with some sort of statement about why the Burgess Shale fossils have theoretical signficance, and the 'depth' of the background probably can be reduced. hamiltonstone (talk) 05:01, 22 October 2009 (UTC)

You're right on both points - it should start with a pointer to the significance of the BS, and the history can be slimmed down. OTOH I think the theory stuff (cladistics, stem groups) is needed, in order to explain the about-turn in the interpretation of the BS fossils. I'll prepare a draft in my sandbox, and post link when done. --Philcha (talk) 07:58, 22 October 2009 (UTC)

New draft at User:Philcha/Sandbox/Fossils_of_the_Burgess_Shale_-_Theoretical#New_draft_1. I've slimmed the history and add a few "pointer" sentences, but I think the basic structure should remain the same. After Darwin presented the dilemma, things went relatively quiet for about 80 years - but from the 1940s onwards new evidence and ideas became a trickle and then a flood. This was already going on before Whittington & co's re-analyses in the 1970s, but they provided a quantity and depth of detail with which other fossil beds could not compare.

• Darwin stated the options - the "explosive" view and the "long Proterozoic history that was hidden by the lack of fossils".
• The orthodox scepticism about Precambrian life from the 1860s to almost the early 1960s largely stifled debate for a long time.
• The debate from the 1940s onwards was ignited by new discoveries. In the 1970s the hypothesis of punctuated equilibrium titled the balance towards the "explosive" view.
• Whittington & co's discoveries entered this existing debate, and initially they were influenced by the "explosive" view.
• Meanwhile cladistics was developing for its own reasons (Willi Hennig was an expert on diptera). This is not explained in typical zoology or paleontology textbooks, so the article has to provide explanation.
• Whittington & co (esp. Briggs & Whittington) became dissatisfied with the chaotic picture of lots of unknown and short-lived phyla, and tried out cladistics.
• Later discoveries show BS-style critters widespread and going back at least 15M years earlier. Other discoveries extend the early evoluiton of animal into the Ediacaran.

• The version in your sandbox is an improvement, and should go into the article. I still feel that we're straying a fair way from "Fossils of the Burgess Shale", toward what one would expect in Cambrian explosion, when it comes to the scope of the text. I wouldn't hold it up at GA, but to my mind it stretches the definition of "focussed" in terms of article criteria. :-)

I understand your concern but the Burgess Shale fossils, while very important, was just one of the contributors to the current view of the early evelution of animals. Without the puzzle of the Cambrian explosion, the BS fossil would be just "Wow, that's weird." Without the swing from the Linnean to the cladistics approach to classification, the BS examples would be just a freak show. --Philcha (talk) 22:59, 22 October 2009 (UTC)

Have you suggestions on how to make it clear that the BS fossils were a piece of a jigsaw, although a big piece? --Philcha (talk) 23:01, 22 October 2009 (UTC)

Possibly. First, I have a question: did analysis of the Burgess Shale fossils affect the development / acceptability of cladistics, or was cladistics simply applied to the Burgess Shale to achieve new analytical understandings? hamiltonstone (talk) 02:49, 23 October 2009 (UTC)

The German entomologist Willi Hennig laid the foundations of cladistics in the 1950s, see Brysse or for convenience Cladistics#History_of_cladistics. Brysse says Hennig's work was first translated into English in the late 1960s, and that Briggs and Whittington gave cladistics a try out in the very early 1980s to see if it could make some sense of the BS critters. --Philcha (talk) 06:56, 23 October 2009 (UTC)

• Not sure whether that was an answer :-) My thinking was this: if cladistic analysis of the BS helped to develop the theory of cladistics / entrench it as a new method of paleontol. analysis / provide evidence in support of the utility of cladistics, then I can see a way tie this section into the subject (of the BS fossils) more closely. But if cladistics was simply used to analyse the BS without any of the above effects, then this material may not belong in a section on the Theoretical significance of the BS at all. A section on "theoretical significance of" a subject should be about the effect(s) of that subject (in this case, the subject is the fossils of the BS) on theory, not about the application of theory(ies) to the subject. But I am not familiar enough with the subject matter to know which it is in this case - hence my question. hamiltonstone (talk) 10:54, 23 October 2009 (UTC)

(outdent) I think I'm still looking for a clarification from you on this point: are you saying that the significance of cladistics in this context is that Briggs and Whittington were able to use it to interpret the BS fossils in a new way - and that is the only relationship between BS and cladistics? hamiltonstone (talk) 05:57, 25 October 2009 (UTC)

Your last comment is an accurate summary - cladistics clarified the BS fossils, not the other way round. The impact on interpretation of the BS fossils was immense - from viewing the "weird" forms as a proliferation of short-lived but distinct phyla to "aunts and cousins" of modern forms. Your next question may be "why explain cladistics here?" Some undergraduate textbooks have not yet included cladistics, so non-specialists need a shrink-wrapped summary - especially as the Cladistics article needs improvements and may be re-structured into a package of articles.

BTW I have not yet pasted in from User:Philcha/Sandbox/Fossils_of_the_Burgess_Shale_-_Theoretical#New_draft_1, as I thought there would be more discussion. Please try out a "New draft 2" at User:Philcha/Sandbox/Fossils_of_the_Burgess_Shale_-_Theoretical if you want to experiment - I remember a previous GA review where the sandbox approach helps us to clarify a complex subject. --Philcha (talk) 08:51, 25 October 2009 (UTC)

(undent)From talk:

Yeah, i'm still here. sorry about that. i've been scratching my head about this final section but have also mainly just been busy w real life. So. I have now undertaken a revision at User:Philcha/Sandbox/Fossils of the Burgess Shale - Theoretical. This is the version that I think should replace the current "Theoretical significance" section, and you wil see I have split it into two separate sections. This is in part because all material about cladistics did not belong under the heading "theoretical signifiance" (hence my questioning at the GA talk page).

My new version lacks a crucial final sentence that I am not well-enough informed to write (Too long since I did my geology degree, alas). It should say something like "The interpretation of the Burgess Shale fossils thus contributed to the debate about punctuated equilibrium / explosion / continuity of evolution by [fill in the blank here in plain English]." The problem is that at present, there is a brief reference to the interpretation by Whittington et al "as evidence that all the living bilaterian phyla had appeared in the Early Cambrian", but you need to join these dots for the lay reader to how this means the BS fossils were positioned as evidence on which 'side' of the debate. Once that is done, these sections are ready to go across. Even without that sentence, I think my version of your revision is an improvement of the current approach in the article. hamiltonstone (talk) 11:10, 31 October 2009 (UTC)

it really is one big debate that pulls in bits from different areas, as at my new previous draft. Maybe I'm not using the right signposts, perhaps because I've been working on this subject area since autumn 2007, and may take for granted the connections and the complexity. Let's see if breaking it down helps, then we can see when we need more signposts:

• The issue starts with Darwin's dilemma that his theory of evolution assumes a long, gradual development of life, including animals - but the fossils he recognised started in the Cambrian. Buckland note the phenomenon earlier, but did not have a theory of evolution,
• Most paleontogists from the mid-19th centuries to the 1960s were not just sceptic, they dogmatically assumed there was no Precambrian life (Walcott was an honourable exception). The discoveries of Sprigg and other discoveries in the Ediacaran from 1948 onwards and of Tyler & Baghoorn's discoveries of fossil cyanobacteria about 2,300 to 1,900 million years ago starting breakdown this resistance. But knowledge of Precambrian life had a long of catching up to do, and contributed little to 1970s debates.
• So the debate between an "explosion" (Cloud) and "a long history hidden by lack of earlier fossils" (Durham & Glaessner) was very little advanced than in Darwin's time. The punctuated equilibrium suggested that evolution was jerky.
• Whittington's & co. find a lot of fossils that appear not to be members of know phyla (at this point they knew only Linnean taxonomy). It seems that all these phyla appear abruptly (and unusual lower taxa, e.g. Marella), and that are short-lived. As result it seems that the Early Cambrian was extraordinary in both speed and variety.
• Meanwhile from left field the theory of cladistics have been developing. Short digression of the main relevant ideas of cladistics, since IMO many readers will not understand the principles (or have misconceptions).
• Whittington's & co. are dissatified with the apparent confusion in the Cambrian, and try out cladistics, which was "new" in UK at the time.
• Influenced by cladistics, the new and still currently dominant view that many of the "weirdies" are "aunts and cousins" of forms that survived to to-day.
• Fossils that are wide-spread and similar to those of the BS but about 17 MY before BS indicate that the real action was over 20 MY before the BS (frustratingly, we have so far no really good fossil beds during went the action must have been). However we now have some fossils even earlier that, in the Ediacaran (e.g. Kimberella) which suggest that some groups developed fairly gradually at various times, rather than in a Big Bang.

Does this help you to suggest how signposts could be placed. --Philcha (talk) 13:36, 31 October 2009 (UTC)

response

I have been reading these points and the attempted revisions (both yours and mine) over the last week and still have problems. Can you do two things please:

• First, rewrite this sentence from just above—"Influenced by cladistics, the new and still currently dominant view that many of the "weirdies" are "aunts and cousins" of forms that survived to to-day"—so that it is grammatical. It is the most important of your dot points I think, but I wasn't sure what was intended.

  The 1970s view (still used in Gould's Wonder Life, 1989) was that phyla and other higher-level taxa appeared very quickly in the Early Cambrian, and that many of these were very short-lived (geologically). Cladistics emphasises similiarities rather than differences, so that the odd-looking Early Cambrian forms became "aunts and cousins" of extant ones, rather than unexplained "weirdies". --Philcha (talk) 11:08, 6 November 2009 (UTC)

• Second, yes i think you may be too close to the detail of this material. Humour me with an attempt to explain in one or two sentences for a lay reader the theoretical significance of the BS fossils - that is, the significance of these fossils (and not the others more recently found) to theory(ies) in paleontology / evolution / systematics. I am not looking for the historical account of how the debate evolved (which you have provided and will be useful) but why the Burgess Shale fossils matter for theory. At this stage i am still not clear about why this stuff should be in this article, even though i am perfectly willing to believe that it does. Don't misunderstand my intention—I am not going to sugest those one or two sentences should become the only text to be under the heading. But I still need to get a handle on the key point you are trying to get across to the lay reader here. Ta. hamiltonstone (talk) 02:13, 6 November 2009 (UTC)

  I think the reasoning is a 3-step process rather than 2. Stage 1 was a paradigm shift in which Linnean classification was replaced by cladistics. The new paradigm (1) combined with the new BS fossil discoveries (2) produced a new interpretation of the BS fossils (3), as "aunts and cousins" rather than "weird wonders". Of course the chronological sequence was different: Linnean classification; Walcott's fossils and his interpretations; Whittington & co's re-analysis of these animals anatomy, in much greater detail, from early 1970s onward; the view of a profusion of "weird wonders"; the cladistics paradigm (introduced in late 1970s in UK; used by Whittington & co from 1980s onwards); the "aunts and cousins" view of BS fossils becomes and still is dominant.

  From the point of view of the (bemused) lay reader - Whittington & co from the 1970s onwards produced much more detailed investigations of the anatomy of many BS fossils. At the time paleontologists used the traditional Linnean classification, which emphasised differences in types of organisms. This approach made many of the BS animals look nothing like later animals, and many of the BS animals looked very short-lived. Cladistics was developed in the 1950s onwards and initially for analysing relationships between insects. In the late 1970s English-speaking paleontologists saw cladistics as a possible way of making relationships between BS animals clearer. Increasingly detailed analysis from the early 1980s onwards developed a view of the stranger BS fossils as "aunts and cousins", and this is now the dominant view. --Philcha (talk) 11:08, 6 November 2009 (UTC)

For what it's worth, these are my picks as the sources most likely to quickly and directly support a section on theoretical signif:

• Collins, D. (August 2009). Misadventures in the Burgess Shale. Nature 460: 952–953
• Brysse, K. (2008). "From weird wonders to stem lineages: the second reclassification of the Burgess Shale fauna". Studies in History and Philosophy of Science Part C: Biological and Biomedical Sciences 39 (3): 298–313
• Conway Morris, S. 1998. The Crucible of Creation: The Burgess Shale and the Rise of Animals. Oxford University Press, Oxford.
• Simonetta, A. M. and E. Insom. 1993. New animals from the Burgess Shale (Middle Cambrian) and their possible significance for the understanding of the Bilateria. Bolletino di Zoologia, 60:97-107

I am particularly puzzled by the omission of Conway Morris's 1998 book, which would seem the most likely source of an accessible summary of matters relating to significance (though I concede i say this not having access to the book). I'll try and get a look at Collins to see what I think of its use in this context. hamiltonstone (talk) 02:53, 6 November 2009 (UTC)

Brysse (2008) is central on the paradigm shift. Budd (1996; doi:10.1111/j.1502-3931.1996.tb01831.x) makes good sense of the arthropods and near-arthropods that are the clearer of the 2 most discussed fossil groups of the BS (Wiwaxia and other halwaxiids are still contentious, as the citations at Halwaxiid show, some also cited at Fossils of the Burgess Shale). Collins, D. (August 2009) is history of exploration / collecting rather than theory. I'd be careful of Conway Morris (1998) as I've seen criticism this book was not as objective as it could be, especially in its comments about Gould's Wonderlife; and it's a pop science book, so interspersed with personalities and pretty things that get in the way of the analysis. Simonetta and Insom (1993): looks as fanciful as Simonetta's 1960's articles; proposes that Metaspriggina was an early chordate and also like some Ediacaran "vendobionta" such as Spriggina, which had a sort of set-off symmetry. --Philcha (talk) 11:08, 6 November 2009 (UTC)

That's fine on Brysse and Simonetta. But the Conway Morris book appears to me to be the most important work of its type. Unless you have reliable sources criticising it, i think it has to be used. Besides, it does not have to stand alone - Gould's account of things can be included too. While Conway Morris may be "pop science", the WP article would really benefit from using such a reliable source that talks explicitly about the theoretical significance of the BS (rather than about the BS per se, which is not the same thing). I'm still cogitating about this final section, but haven't had periods of uninterrupted time to apply to the question. If I can't get it sorted by the end of the weekend, i'll ask for a 2nd opinion at GAN and defer to that. To repeat though: my concerns are confined to the theoretical signif section - everything else is good. hamiltonstone (talk) 04:56, 11 November 2009 (UTC)

Hi, many thanks for the effort and patience you've shown on this. I could ask User:Smith609 to have look, if he's free - he's a paleo PhD student specialising in the BS and similar critters; while we get on really well, his priority is the science. Otherwise I could have a look for other good paleo editors. However, I'll leave the choice to you as have too many reviewers on the case might be confusing.

How ever this turns out, I'll keep looking on ways to clarify this - you have a head start compared with the typical non-specialist reader, and your concerns imply that improvement is needed. If I leave it alone for a couple months and then look again, that might blow away a mental block or two.

Wonder Life and The Crucible of Creation both have weaknesses, and I'd be uncomfortable about using them in the theoretical part of this article. Gould was a Marxist, he loathed anything that sounded like Social Darwinism, and as part of this he disliked any suggestion that survival of an evolutionary lineage was any way "on merit", which is why Wonder Life makes so much of "contingency" (i.e. it's all luck). The Crucible of Creation has been criticised for using Gould's views as a straw man in a rather spiteful way (SCM started with views similar to Gould's, but became increasingly impressed with convergent evolution, and later implied that human-level intelligence is nearly inevitable, although some other lineage might have been the first or only example). We can get better sources. --Philcha (talk) 07:53, 11 November 2009 (UTC)

I've been bold

Hi Philcha. I have mulled over your points and clarifications, and previous drafts, and decided to be bold and make a revision, based on your explanations, to the article. I hope it meets with your approval. My pleas are twofold:

• Whatever happens with this section, it has got to be clear that the BS fossils have theoretical signficance, not just that theories were applied to them.
• It has got to be simple enough, and leave out enough of the uncertainty within the academic community debate, to be understandable to the lay reader. To the extent that uncertainties and details and potentially contradictory individual fossils or fossil assemblages are significant, they should be discussed elsewhere, under cladistics, or the individual species, or Cambrian explosion etc. I think i've trimmed the detail to the right level for this article and for the lay reader.

If you are happy with this revision (copyediting aside), i'm happy with it at GA. See what you think. hamiltonstone (talk) 01:49, 13 November 2009 (UTC)

hamiltonstone, I think you've provided most of the link phrases we both felt were needed, and encouraged me to add a couple more. At the same time, the text must avoid scientific inaccuracies, and that limits how far the text can be simplified. It's not as difficult as maths, where readers run out of steam at 15-year old level if they don't assimilate the concepts and notations. But you know from geology that diagrams and simple text run out of steam when the processes that form rocks start to require some chemistry (I'm thinking of e.g. diagenesis and metamorphism).

I'm still concerned about your "it has got to be clear that the BS fossils have theoretical significance, not just that theories were applied to them." The fossils are material for testing and comparing hypotheses. The initial devising of hypotheses is not understood and may be idiosyncratic - e.g. Bob Bakker as a teenager though "there's something with our dinosaurs" (his reaction to current reconstructions), and Einstein said the germ of the special theory of relativity was his speculations about how the universe looked from the point of a photon. The significance of the BS fossils is in testing, comparing and refining hypotheses, and the hypotheses were largely consequences of other hypotheses, plus one paradigm shift. In addition, the BS carried the whole burden of evidence until the early 1980s; then serious analysis of Ediacaran organisms and preliminary results for Chengjiang provided more info about the timescales and the types of organisms. The story as a whole is a like a real-life detective - there's no master clue or flash of insight that solves the case just like that; the initial evidence is fragmentary, some turns out to be irrelevant or even misleading, the significant of other items is ignored for a long time; early speculations may suggest searches for further evidence; gradually the evidence and speculations become coherent enough for hypotheses to be tested and compared; eventually there's a verdict; some cases go to appeal, and some of these are overturned.

So get what, I've had another go:

• The Durham / Glaessner hypothesis (long history obscured by gaps in fossil record) goes back to its place in the chronology (1970s), otherwise it looks like Cloud and co. ("explosive") held the field in the early 1970s - there was a "gradual vs explosive" debate before Whittington & co. published their re-analysis of the BS fossils. However, I've prefaced this debate with your "Darwin's view – that gaps in the fossil record accounted for the apparently sudden appearance of diverse life forms – still had scientific support over a century later".
• Added "The fossils of the Burgess Shale were hidden in store rooms until the 1960s" until Whittington and co got to work. A slight simplication, as Simonetta (1960s) and earlier a guy called Hutchinson produced "fanciful" reconstructions of Opabinia, see Wonderful Life.
• Edited to "the fossils became central to the debate about how quickly animals arose, and were interpreted as evidence that all the living bilaterian phyla had appeared in the Early Cambrian". "became" is vital - the BS fossils were almost completely ignored between Walcott's death and the work of Whittington & co. (the exceptions being Simonetta and Hutchinson).
• Re cladistics, changed "a new approach to evolutionary systematics" to "which appeared in the 1950s". Cladistics started as an attempt to make sense of living insects, and for over a decade the literature was all in German. What was new in the 1970s was the English-speakig paleontologists got excited about cladistics.
• Reinstated "In the 1990s it was suggested that some Ediacaran fossils from 555 to 542 million years ago, just before the start of the Cambrian, may have been primitive bilaterians, and one, Kimberella, may have been a primitive mollusc." AFAIK this was the first credible evidence of Precambrian animals more complex than jellyfish. The BS and Chengjiang fossils were evidence that the Cambrian explosion was already completed. Some very, very early Cambrian fossils (Helcionellids in the small shelly fauna) looked like molluscs. But Kimberella make it credible to look a further 13 MY further back in time.
• Removed "Thus the fossils of the Burgess Shale went from being considered evidence in support of an 'explosive' beginning to Cambrian life, to being understood as evidence of a more gradual evolution of animal diversity." This sentence takes one side in a going debate. For example Budd, who produced the lobopod-Anomalocaris-arthropod cladogram in the article, regards the Cambrian explosion as "rapid but resolvable" and thinks (last I looked) than Precambrian animals were diploblastic (composed of main 2 cell leyers, as jellyfish and other cnidaria are). Butterfield described Kimberella as a "probable bilaterian", i.e. he places no bets. On the other Fedonkin thinks Kimberella was a near-mollusc, and Erwin and Davidson (2002) regarded the animal as "most likely of protostome affinity" ( triploblastic and one of the 2 "hyper-groups"^TM that have a gut that runs all the way from the mouth to the anus). IMO this issue is too complex to handle at all in Fossils of the Burgess Shale. --Philcha (talk) 09:53, 13 November 2009 (UTC)

OK, thank you - i've enjoyed collaborating on this, and I am sorry I've been pretty slow to respond to your very diligent actions in response to each point that i've raised. I think this now meets the two criteria i was concerned about: the use of jargon; and ensuring it "stays focused on the topic without going into unnecessary detail". Perhaps your last point, just above, could be covered by a sentence along these lines: "The fossils of the Burgess Shale continue to be important to the ongoing analysis of the origins of Cambrian life." It would just be nice to have a sentence that wraps things up. i will leave that in your hands - i am passing this article. hamiltonstone (talk) 01:43, 16 November 2009 (UTC)

Other minor stuff no longer under consideration

• Re text "crown group" partly obscured by "stem group", in what browser & version plus OS and version, plus any settings that affect text size? --Philcha (talk) 08:49, 12 October 2009 (UTC)

  If it's IE 7 or higher, I think I know the answer. IE (incl v 6) used to ignore absolute sizes (e.g. in px), contrary to WCAG. IE 7 has now caused confusion by introducing 2 mechanisms:

  • Text resizing affects text but not images. This is what can mess up annotated images, as the text is scaled up but the image content and frame are not. FF and Opera do not use the mechanism.
  • Zoom also scales the image as well as text annotations, and thus does not mess up the relative sizes and locations of annotations in annotated images. FF and Opera have had zoom for years, and it's more useful as it also scales text implemented as part of an image (e.g. as in the WP logo).

  The zoom control sequences (CTRL and + to increase, CTRL and - to decrease) are the same in FF, Opera and IE. In FF and Opera, there also menu items for zoom, which show the control sequences. In IE 7 only text resizing appears in the menu - in order to learn zoom, users must look up some external source. --Philcha (talk) 11:31, 23 October 2009 (UTC)