Talk:Kimberella/GA1

GA Review

Initial Impressions

My first GA review, but this thing has been sitting unreviewed for a long time and I'm going to take a crack at it. As I'm seeing it, there are definitely some things to clear up before this will pass GA.

• The geologic timescale on the left hand side does not display properly in IE or in Firefox at any of the resolutions I've tried, the text does not line up with the scale and spills into the text below. The Ediacaran biota page has a similar (the same?) block, and that displays properly, so I'm not sure why this one is funky.

I've move the timeline to my sandbox. I asked the template's developer to help me fix it, but so far no response. The problem is that the template wants to spread wider than there's room for with a such a long infobox, and doesn't like the DIV I put round it as a corset. -- Philcha (talk) 11:39, 12 July 2008 (UTC)

• WP:LEAD:

1. The lead should also be a brief summary of everything else covered in the article. In this particular case, it should probably include the location of the major finds, the apparent age, etc.. It's helpful to just look at the structure of the article: each section (other than references) should have at least a one line summary in the lead. The lead should be able to stand as a brief article by itself.

Expanded - what do you think? -- Philcha (talk) 13:03, 12 July 2008 (UTC)

1. Explaining that the fossil casts doubt on a broadly accepted premise (the Cambrian explosion) is well worth mentioning in the lead, since it establishes that the organism is more than trivially notable.

? Done -- Philcha (talk) 13:03, 12 July 2008 (UTC)

• Some basic facts and clarifications:

1. When was the first example formally described?

Added to "Classification" -- Philcha (talk) 11:39, 12 July 2008 (UTC)

1. There is more information given on the White Sea find than the Ust'Pinega find. Is there anything substantially different between the two groups? When were they discovered?

"in the Ust’ Pinega Formation in the White Sea region of Russia". I used "White Sea area" elsewhere as it will be more easily recognised by readers.-- Philcha (talk) 11:39, 12 July 2008 (UTC)

No differences reported between the various specimens (except size - an apparently continuous range from 3mm to 15cm in length, which the sources interpret as a growth sequence). The Ediacara biota generally seem to have been global, and I've read a paper (not relevant to this article, noted at Talk:Ediacaran biota) which argues that the main influence on relative species abundance was sea-floor and current conditions). -- Philcha (talk) 11:39, 12 July 2008 (UTC)

1. What is the source of the name? (Not critical, but commonly covered).

No mention in the sources, and Google didn't help. -- Philcha (talk) 13:03, 12 July 2008 (UTC)

1. "Kimberella′s body was metameric (built as a series of repeated "modules"), but without visible segmentation;" If the modules aren't segments, what is contained in each module?

The sources say "metameric" but the only "metameric" feature I've found in them is the bands of dorso-ventral muscles. I thought the description of these went more naturally with the transverse ventral muscles to explain the rippling motion of the foot.

I could re-phrase a group of sentences:

Kimberella′s body had no visible segmentation but was metameric (built as a series of repeated "modules"), with well-developed bands of dorso-ventral muscles (running from top to bottom). It had a single, broad, muscular "foot" and smaller transverse ventral muscles (i.e from side to side on the underside of the body). The combination of the bands of dorso-ventral and transverse ventral muscles probably enabled Kimberella to move by making the foot ripple.[Fedonkin 1997 and 2007]

Would that work for you? -- Philcha (talk) 11:39, 12 July 2008 (UTC)

I've used the phrasing above. -- Philcha (talk) 18:48, 12 July 2008 (UTC)

• The article needs copy editing, which is a very vague complaint, but here are some places to start:

1. Some of the language appears to be intentionally imprecise. For example: "The edges of the fossils are crenulated or scalloped, apparently bearing 44 lobes." Don't write into a corner, but if you're being intentionally vague, explain why a stronger statement is inappropriate. Why is the number unclear? Are the fossils broken and the number an estimate? Do all of them have 44?

I've commented out "The edges of the fossils are crenulated or scalloped, apparently bearing 44 lobes" as it's not supported by the citation (Glaessner 1959) nor by any of the Fedonkin papers I've seen (including those cited). -- Philcha (talk) 13:03, 12 July 2008 (UTC)

Are there any other areas of "intentional imprecision" you can highlight? I'm not promising I can fix them, as interpreting soft-bodied fossils is difficult and imprecisions may reflect what the sources say - we'd have to look at them case by case. -- Philcha (talk) 13:03, 12 July 2008 (UTC)

Philcha (talk) 13:03, 12 July 2008 (UTC)

1. "In 2001 and 2007 Fedonkin suggested that the feeding mechanism might be a retractable proboscis with hook-like organs at its end." Using just the surname is normal for journal articles, but an encyclopedia usually uses the full name and gives a one-phrase biography the first time a person is mentioned.

I've wikilinked Fedonkin ealier in ""Classification". -- Philcha (talk) 13:03, 12 July 2008 (UTC)

1. There's some rogue punctuation, a few run-on sentences, and other things to fix.
2. I would avoid using parenthetical statements and abbreviations (i.e., etc...) in the actual text. They're not wrong, but the writing should "look" relatively formal.

Just a first look. I'll probably have more later. SDY (talk) 07:22, 12 July 2008 (UTC)

General comment: only the White Sea specimens appear to have been dated with any precision.

I look forward to your next batch of comments. Many thanks! -- Philcha (talk) 13:03, 12 July 2008 (UTC)

PS re style:

• Can you please give some exmaples.
• We might have to discuss "the writing should look relatively formal". I think the primary audience for a general-purpose encyclopedia should be non-specialists and certainly non-academics - in fact I try to keep asking myself how it would look to a curious 12-year old (as I was when I got interested in palaeontology). Hence I prefer to avoid jargon (for example "rather modern-looking Cnidarians" is a translation of "crown-group Cnidarians" in Erwin & Davidson 2002) and to define it if I feel forced to use it. In theory wikilinks should get round that, but:
  • The articles available for wikilinking vary a lot:
    • Some are too technical to help out a non-specialist.
    • Some are too narrow in scope, for example coelom is all about vertebrate and specifically human anatomy. The medical crowd have a lot to answer for.
    • Some are stubs, as triploblast is now.
    • Some look dubious to me, like protostome (for a start the opening sentence "Protostomia ... are a taxon of animals needs to be justified, as protostome later treats ecdysozoa as a sub-group but priapulids, which are classified as ecdysozoans, dod not have coelom; and that's just the start of a big debate).

There's also a usability problem: the reader side-track to get an explanation of some jargon, has to look for it in an article that wasn't designed to explain the jargon term(s), and loses context within and possibly understanding of the article he / she was reading in the first place (humans are poor at stack processing). -- Philcha (talk) 13:37, 12 July 2008 (UTC)

What I mean by "relatively formal" is just that the kind of things that you would use on a talk page or a conversation (i.e. side comments like this) should be avoided whenever possible. Compare:

1. "The Cambrian explosion is an apparent rapid increase in the disparity (range of basic "designs") of animals in the Early Cambrian period, starting after 543 million years ago and finishing before 518 million years ago."
2. "The Cambrian explosion is an apparent rapid increase in the variety of types of animals in the Early Cambrian period, starting after 543 million years ago and finishing before 518 million years ago."

Just as a side note, I would avoid the word design in a paleontology article.

I've changed it to "... apparent rapid increase in the range of basic body structures of animals ...". It would not be helpful to introduce the standard phrase "body plan" because: it would have to be explained, but it's only relevant once; "body plan" is often associated with "phylum", and it would be really unhelpful to open up the complex issue of "phylum" vs "stem group" and "crown group" when it only occurs once. If you can think of a better simple phrase, I'd be glad to hear it. -- Philcha (talk) 18:48, 12 July 2008 (UTC)

That seems fine. SDY (talk) 20:43, 12 July 2008 (UTC)

Some other language to compare:

1. "These palaeontologists are wary of reading too much into Kimberella's association with Radulichnus marks, as other groups of organisms bear structures capable of making similar marks."
2. "Dr. soandso and other paleontologists have stated that these marks may not be the scratches from a radula since other organisms have structures that can make similar marks."

"Wary of reading too much into" is a phrase I'd avoid in formal writing. Report what they say, not what they think. A direct quote might also be appropriate. Additionally, since whether the marks are radulchinus or not is in question (if there were other molluscs in the same strata that would be equally notable), so I'm guessing the question isn't association but rather identification.

The marks are Radulichnus because that's the name that's been assigned to them. The issue is whether they were made by animals with radulas.

Re "These palaeontologists ...", I've changed that to "Nicholas J. Butterfield argues that ...". OTOH I think it's safer to leave "However, some sceptics feel that the available evidence is not enough .." as is, because one of the co-authors of Martin et al (2000) is Fedonkin, and papers in which Fedonkin is lead author state outright that Kimberella is a mollusc (1997, 2007). Can you think of a way to sort out that mess? -- Philcha (talk) 18:48, 12 July 2008 (UTC)

The problem with "some skeptics" is the WP:WEASEL guideline. It might be best to just leave off the "some" and say "skeptics" and cite it. Saying "some" leaves the reader with the impression that there is another relevant viewpoint that you aren't covering. SDY (talk) 20:43, 12 July 2008 (UTC)

"In other words Kimberella is part of a body of evidence which indicates that animals were diversifying long before the start of the Cambrian." This may have NPOV issues, since it "takes sides" in the debate.

Rephrased. -- Philcha (talk) 18:48, 12 July 2008 (UTC)

I'm not sure whether Radulichnus should be capitalized each time it's used (not familiar with the term), but it should probably only be wikilinked once. Since it wikilinks here, it may be more appropriate to just leave it as explained jargon and not link it until it has a separate article.

Thanks for pointing out that Radulichnus wikilinks to Kimberella; I've unlinked it.

Radulichnus should be capitalized and italicised (like e.g. Canis) because trace fossils are treated as pseudo-genera. -- Philcha (talk) 18:48, 12 July 2008 (UTC)

That makes sense, though last I saw they were just capitalized. SDY (talk) 20:43, 12 July 2008 (UTC)

Making it accessible is mostly about avoiding or explaining jargon, avoiding complicated sentence structures, and providing examples. Explanations for exhibits at a natural history museum is probably the "target" for the level and style of language.

A one-line jargonless explanation of what a protostome is, for example, lets a reader keep reading without having to jump to a second article. Mention that protostomes are a group that includes a great variety of animals such as earthworms, clams, and spiders. The article should be able to stand on its own without links, because people can and do print them out.

In general, if you're going to be unclear about something, such as "This musculature probably enabled Kimberella to move by making the foot ripple." then the article should be clear why it's being unclear. Is this a proposed mechanism? Is it being compared to a snail's locomotion? Is there some evidence from nearby trace fossils?

Fedonkin 2007 says "The complex musculature of this peripheral foot was able to create a “running wave” used for locomotion (gliding over the floor), ..." and that's all. I think I should remove "probably". -- Philcha (talk) 18:48, 12 July 2008 (UTC)

If there isn't any notable dissent, that sounds good. Comparing it to a living animal may help for comprehension. SDY (talk) 20:43, 12 July 2008 (UTC)

If you're going to leave something out because the information simply isn't known, such as the date of the Australian find, just have the article say "this hasn't been done yet." You might want to include some possible dates on the range of age of nearby fossils (i.e. it was found with spoo, and spoo has been found from 314 mya to 666 mya). SDY (talk) 16:39, 12 July 2008 (UTC)

I've added "The fossils from the Ediacara Hills have not been dated precisely."

Glaessner 1959 does not provide a date (hardly surprising as dating tech has moved on); I don't have access to Glaessner & Wade 1966 or Wade 1972, but I'd be surprised if they were in a position to give dates even in 1972. I notice Ediacara biota is very light on dates. That's probably why the Martin et al(2000) paper was titled "Age of Neoproterozoic Bilatarian Body and Trace Fossils, White Sea, Russia: Implications for Metazoan Evolution" - getting such a precise date is pretty unusual, and the tech is fairly recent (see for example Permian–Triassic extinction event, for which good dating appeared only in 2000). OTOH I think it would be WP:OR to go into an explanation of the difficulties, because Glaessner 1959 says nothing about it; it was an accepted occupational hazard in those days. -- Philcha (talk) 18:48, 12 July 2008 (UTC)

Well, if there's no date, there's no date. As long as the article explains that there isn't one available I see no problem with it. SDY (talk) 20:43, 12 July 2008 (UTC)

I think you might be pushing too hard on the explanatory parentheses - Ediacara biota (FA) has a few, and so did the version 1 day before it was promoted. I've eliminated a few, and those in "Theoretical importance" may not be all that helpful to non-specialist readers (the next question is "what's a coelomnate?"). OTOH I think "... dorso-ventral muscles (running from top to bottom) ... and smaller transverse ventral muscles (i.e from side to side on the underside of the body)" needs the parenths as Anatomical_terms_of_location#Dorsal_and_ventral does not define "dorso-ventral" or "transverse". -- Philcha (talk) 18:48, 12 July 2008 (UTC)

They aren't "forbidden," but they should be used sparingly. My impression for this article is that what's included in parentheses could just be used instead of the jargon and send exactly the same message. If the article were spoken, what would the reader do with the parentheses? SDY (talk) 20:43, 12 July 2008 (UTC)

I've given some examples of how they can just be included in the main text. "Side to side on the underside" bugs me, but a better way to word it escapes me at the moment. SDY (talk) 21:01, 12 July 2008 (UTC)

Thanks for the adjustments you've made - they work fine for me.

BTW I'm not sure "If the article were spoken ..." is an effective way to make the point about parentheses, since speech tends to include little digressions like that. The only case where I've found "If the article were spoken ..." effective is in phrasing link text. -- Philcha (talk) 21:43, 12 July 2008 (UTC)

I think everything you've raised so far has been dealt with, except protostomes and deuterostomes. I'd better sleep on that, as circumlocutions would probably break the flow, and would become the largest elements of the paragraph. -- Philcha (talk) 21:43, 12 July 2008 (UTC)

You might want to phrase the protostome and deuterostome split as just a major diverging point in evolution and leave it at that. They're such broad groups that giving examples could really get off topic. One question: "A well-developed band of dorso-ventral muscles running from top to bottom." Top (attached to shell) to bottom (directly down, or out along the skirt)? Specifying will avoid people misreading "top to bottom" as "front to back." SDY (talk) 22:06, 12 July 2008 (UTC)

And I thought I was paranoid about avoiding ambiguity :-)

I've edited to say, "Each module included a well-developed band of dorso-ventral muscles running from the top to the single, broad, muscular "foot", and smaller transverse ventral muscles from side to side on the underside of the body." Fedonkin (1997 and 2007) says the skirt rippled, but is not specific about whether the major dorso-ventral muscles extended inot the skirt. -- Philcha (talk) 22:50, 12 July 2008 (UTC)

More clarifications

• "In 2001 and 2007 Fedonkin suggested that the feeding mechanism might be a retractable proboscis with hook-like organs at its end." How does this compare to a radula? Very similar? Totally different?

See the pics at Radula. The problem is Fedonkin did not provide details of what he had in mind. The titles of his papers call Kimberella a "mollusc-like" organism, so it could have been an "aunt" rather than a direct ancestor of modern molluscs. I've re-worded "Classification" to "sceptics feel that the available evidence is not enough to reliably identify Kimberella as a mollusc or near-mollusc" to handle this.

I've also re-worded the end of the "Theoretical importance section":

• "If Kimberella is very similar to a mollusc, ..." should handle Fedonkin's wording.
• "This would cast doubt on the idea that the main groups of animals appeared rather abruptly in the early Cambrian." There probably was a "Cambrian explosion" of disparity, even if most of the main body plans were established before then. -- Philcha (talk) 00:02, 14 July 2008 (UTC)

• "The White Sea strata have been dated to 555.3 ±0.3 million years of age by radiometric dating, using uranium-lead ratios in zircons found in overlying volcanic ash layers." Is the 555.3 figure for the overlying ash layer or for the strata containing the fossils?

Martin et al (2000) says the zircons were from a volcanic ash layer sandwiched between 2 layers that contained Kimberella fossils. I've fixed that in the text. Thanks for spotting the problem! -- Philcha (talk) 00:02, 14 July 2008 (UTC)

BTW re your previous query about dates of finds in other areas, Martin et al say, "The two most abundant and diverse body and trace fossil assemblages--those from the Flinders Ranges (10, 21) in South Australia and White Sea coast in Russia (22), which account for 60% of the well-described Ediacaran taxa (23)--have neither numerical age nor direct chemostratigraphic constraints. In this report, we summarize the biostratigraphy and age of the Zimnie Gory exposure along the White Sea in Russia, and place the spectacularly preserved trace and body fossils, including the triploblastic bilaterian Kimberella (24), into a global chronostratigraphic framework." In other words the age of most fossils of Kimberella has not been determined precisely. -- Philcha (talk) 00:02, 14 July 2008 (UTC)

We obviously still need a good quick and dirty explanation of what protostomes and deuterostomes are. These are the only concerns I have remaining, though I'm still bubbling over whether we need to include some more "context" since we don't have the timescale that's having technical problems. SDY (talk) 22:40, 13 July 2008 (UTC)

I still haven't thought of a good quick and dirty explanation of what protostomes and deuterostomes are. The issue is about how the embryo develops. A dent called the blastopore forms, deepens and breaks through on the far side, so that the resulting "tunnel" forms the gut. In protostomes the site of the initial dent forms the mouth and the far end of the "tunnel" forms the anus. Deuterostomes are the other way round - the dent forms the anus and the far end of the "tunnel" forms the mouth. That's about as quick and dirty as it gets, but would increase the length of the final para by about 50%. And I'd then have to hunt down a ref for something that's in Zoology 101. It's often harder to get good refs for the basics than for the advanced stuff, but I may know a source.

There's another template that I could use for now (see for example the big pic at top right of Cambrian substrate revolution), using a graphic for the bars. I'll do that tomorrow. Please remind me firmly if I forget! -- Philcha (talk) 00:02, 14 July 2008 (UTC)

Replacement timeline done. -- Philcha (talk) 09:37, 14 July 2008 (UTC)

Our one last point of resistance, which actually belongs in the lead since that's the first time we use protostome.

Deuterostomes are distinguished by their embryonic development; in deuterostomes, the first opening (the blastopore) becomes the anus, while in protostomes it becomes the mouth.

In protostome development, the first opening in development, the blastopore, becomes the animal's mouth. In deuterostome development, the blastopore becomes the animal's anus.

Either would work. The first is from the deuterostome article, and I'll let you guess where the second is from. Dropping the reference to the blastopore is probably fine in either case since it's not important to wikilink it here and it gets rid of those nasty and evil commas cutting up our short and declarative sentences. (breath)

I don't think it belongs in the lead — I checked the first 4 items at Wikipedia:Good_articles#Natural_sciences and they only wikilink tech terms, without adding explanations.

I'm still thinking about how to explain it. The version I suggested above gives a clearer picture. Getting refs for any explanation is harder than I expected, as my paleontology textbook does not explain it and the only useful things I've found on Google are lecturers' notes for Zoology 101. -- Philcha (talk) 08:37, 15 July 2008 (UTC)

Do you realise just how much trouble you've caused? In retaliation, I'm not going to spare you the details. The protostome-deuterostome distinction was formulated when most comparative embryology involved only Drosophila and vertebrate embryos, but it turns out that these are idionsyncratic members of their respective super-groups. My quick-n-dirty explanation of the deuterostome gut tunneling through to rip the critter a new mouth was accurate enough. But with protostomes the blastopore's edges close up in the middle, leaving gaps at the ends (think of a figure 8, or the frame of a pair of spectacles), which form the mouth and anus; then the gut forms a loop; then the mouth and anus move to opposite ends - see Evolution of the bilaterian larval foregut. So it appears that "protostome" is a misnomer. This is another fine mess you've got me into!

I've inserted a summary of this, without Laurel & Hardy, as the middle para of "Theoretical importance". I'll try to forget what I wrote and look at it again later to-day with fresh(?) eyes to see if I can make it shorter or simpler.

PS If you copyedit it, do not wikilink anus - those bloody medics again! -- Philcha (talk) 11:08, 15 July 2008 (UTC)

Almost forgot something: do we have a citable ma for the proto/deutero split? Probably helpful to explain why it being a protostome causes a bit of a stir, and it's sorta there, but having a "we thought it was this, but we're not so sure because there's a clear date here that doesn't add up." We should also explain bilaterian -> protostome -> mollusc is the expected branch on the phylogenetic tree. SDY (talk) 23:37, 14 July 2008 (UTC)

That is such a controversial topic that Kimberella should avoid it — the subject could become an article in its own right, wikilinked by Protostome and Deuterostome. If Kimberella is a protostome, it's the earliest known fossil of either group. Vernanimalcula (about 580 million years ago) may be a coelomate, but AFAIK no-one has tempted to specify whether it may have been protostome or deuterostome. Some researchers use molecular phylogeny techniques to estimate the age of the split, but that's really controversial: even if you only use mol phylo to investigate the structure of evolutionary "family trees", there's a risk that random mutations over periods shorter that 555 M years can cause errors by accidentally producing features that resemble some completely different organisms's DNA / RNA (think of Shakespeare and a million monkeys); and using mol phylo to date evolutionary events is seriously controversial, as it assumes that the "molecular clock" runs at a predictable rate. In fact even the family tree aspect is still uncertain, see for example this set of lecturer's notes. Molecular biologists suggest dates for the split ranging from 1,200 million years ago to 670 million years ago ±60 M yrs., see last para of Pushing Back the Origins of Animals. -- Philcha (talk) 09:05, 15 July 2008 (UTC)

In that case, the article should, in my opinion, mention that there isn't a consensus. Ultimately, if the article is going to bring up protostomes and deuterostomes, it should explain why anyone should care. The ontogeny, in my mind, isn't that important overall. For K. proto/deutero is mostly relevant because of the bubbling pot it stirs. If we're going to call it controversial, we need to explain what is contested, and that it is such a sore point is a very relevant piece of information for the article. SDY (talk) 15:31, 15 July 2008 (UTC)

I'm not at all sure about that:

• The article is about Kimberella, not about the exact(ish) date of the proto/deutero split.
• The much less divisive controversy related specifically to Kimberella is whether it was a fully paid-up protostome. Section "Classification" already mentions scepticism about this. If it was, then at most it indicates that the split was no later than about 600 million years ago to 580 million years ago, which is at the bottom end of the range of mol phylo estimates. The issue about whether Kimberella was a genuine protostome will be decided (if ever) by further analysis of Kimberella fossils, not by arguments about the date of the proto/deutero split.
• None of the sources cited mentions the larger controversy about the date of the proto/deutero split. I mentioned it only to explain why I thought the Kimberella should not get itself dragged into it.

I think there's a good case for a separate article about the early evolution of animals, to which Protostome, Deuterostome, Bilaterian and probably Cambrian explosion could link. I don't think I'm ready for that yet, but might be in 6 to 12 months if I get lucky with sources while researching other articles -- for example IIRC there's serious argument about whether the protostomes are monophyletic, about the idea that protostomes and deuterostomes might separately have evolved the bilaterian form, and even about whether Cnidaria might have been basically bilaterian, but with radial symmetry over-laying that at a very early stage in their ontogeny and phylogeny. Of course if someone else feels up to it, I'd do what I can to help. -- Philcha (talk) 22:35, 15 July 2008 (UTC)

OK, thanks for the clarification. I wasn't expecting a full discussion of the controversy here, just a one-sentence mention that "there is no date and information that might lead to one would resolve an important controversy in paleontology." If nothing else, it establishes to your average reader that Kimberella is not "just another rock" and goes to establish notability, if not notoriety.

Have I misunderstood your comments? I thought that "If Kimberella was a mollusc-like protostome, the protostome and deuterostome lineages must have split significantly before 550 million years ago." established a conditional and approximate "not later than" date for the proto/deutero split. -- Philcha (talk) 08:44, 16 July 2008 (UTC)

At any rate, the ultimate problem that comes up is simply that we're throwing jargon around (protostome, etc...) and there's no explanation for what that jargon means. That guideline is basically what I'm trying to address as a reviewer. The alternative is to avoid the jargon entirely. SDY (talk) 23:57, 15 July 2008 (UTC)

Does the recently-added 2nd para of "Theoretical importance" not deal adequately with "protostome" and "deuterostomes"? Or are you concerned about other jargon or elsewhere in the article? -- Philcha (talk) 08:44, 16 July 2008 (UTC)

It's fine now. I think it's safe to assume that a reader knows what a mollusc is and that's not too jargonish, and bilaterian is rather self-explanatory. SDY (talk) 15:06, 16 July 2008 (UTC)

Timeline

The timeline template expert User:Smith609 has just fixed the timeline at User:Philcha/Sandbox#Time_line_for_Kimberella. Would you like to check it out in all your browsers? We'd prefer to use the timeline rather than my image-based work-round, as the timeline version is easier to maintain.

By the way, User:Smith609 also contributed about half the content of Kimberella. -- Philcha (talk) 23:18, 15 July 2008 (UTC)

Timeline and text

The timeline and the text don't seem to line up that well. Just going from top to bottom:

1. "Last putative Ediacaran" - The article doesn't really give a scope for the Ediacaran period. This marker on the timeline could actually just be taken out for simplicity, or the article could give a line of give context about Ediacaran fauna in general (i.e. "the earliest known complex multicellular organisms") and where Kimberella fits in this group.

Removed. -- Philcha (talk) 21:12, 16 July 2008 (UTC)

2. "Cambrian Explosion" - The article talks about the start of the Cambrian at 543 ma, but it doesn't give any context for when the explosion started, just "after". It's a tolerable ambiguity, but if it can be easily rectified then it's worth changing. If that opens another can of cnidarians, leave it be. The end is clearly explained at 518 ma in the text. I'd also make it Cambrian explosion(?) instead of ?Cambrain explosion, but that's just editorial.

The end is easy - it must have finished by the time of the Sirius Passet lagerstätte, 518 MYA. The start is often said to be around 530 MYA, but that's really just an assumption, since before Sirius Passet the Cambrian fossil record is patchy and there are no earlier Cambrian lagerstätten to preserve soft-bodied organisms / parts - so I'd treat the start as another can of cnidarians. -- Philcha (talk) 21:12, 16 July 2008 (UTC)

3. "Last Ediacaran communities" - See #1.

Removed. -- Philcha (talk) 21:12, 16 July 2008 (UTC)

4. Kimberella - No problems.

5. Charnia - Why is it relevant? Is it just a benchmark that gives context? Is it related?

Removed. -- Philcha (talk) 21:12, 16 July 2008 (UTC)

6. Aspidella - See #5. Including a note at the bottom of the table explaining that these two are other notable examples of Ediacarans is probably sufficient.

Removed. -- Philcha (talk) 21:12, 16 July 2008 (UTC)

7. Gaskiers glaciation. Is the dark green line for the glaciation or for Aspidella? Why is this relevant?

Removed. -- Philcha (talk) 21:12, 16 July 2008 (UTC)

8. "First Ediacaran megafossil" - See #1. Avoid or explain the word megafossil.

Removed. -- Philcha (talk) 21:12, 16 July 2008 (UTC)

9. ? Embryos? - I assume this is the Doushantuo formation in general, and it might be helpful to just call it that consistently. Lagerstätte (in the last paragraph) is unnecessary jargon. The embryos in themselves are irrelevant to this article, the Doushantuo is a meaningful benchmark.

Removed. -- Philcha (talk) 21:12, 16 July 2008 (UTC)

In general, there are several things in the timeline that raise more questions than they answer for the article. SDY (talk) 18:51, 16 July 2008 (UTC)

I've added bars to indicate the time ranges of the Ediacara biota and Doushantuo formation, which are mentioned. It ain't pretty, mainly because the time range of the Doushantuo formation is pretty long and the dates of the fossil-bearing bits are "poorly constrained". If you don't like the result I'll try moving the furniture around. -- Philcha (talk) 21:12, 16 July 2008 (UTC)

The qi flows well with this arrangement of furniture. It looks a little barren, though. Can we shrink it down without causing major problems? I've never messed with these types of diagrams before, so I'm not exactly sure how to fix it and it's frankly just a cosmetic issue. Not having the bars overlap the words is another cosmetic fix, but again nothing to get excited about. SDY (talk) 21:21, 16 July 2008 (UTC)

The height wasn't too hard. I've put arrows on "Doushantuo formation" and "Ediacara biota" so that periods don't have arrows and everything else does. I don't see a decent way to prevent the bars from overlapping the words. The convention these diagrams usually follow is period names on the bars, notes just to the right of the bars. But in this case Doushantuo formation and Ediacara biota need inner bars because they cover such a long time-span, and that kicks "Ediacaran" (period) to the right. If I put the innner bars on the right, then it looks as if "Kimberella" is pointing to one of them. -- Philcha (talk) 21:52, 16 July 2008 (UTC)

Status as of 18July2008

The only remaining question is the one that was raised on the bottom of the talk page about the Doushantuo's time period. If that can be addressed and nothing else comes up, I think we're just about done. SDY (talk) 08:27, 18 July 2008 (UTC)

It surprised me too, but that's the range given by U-Pb Ages from the Neoproterozoic Doushantuo Formation, China, which is cited in Doushantuo formation. Perhaps the problem is that the formation has a long time span but fossils have only been found (so far) in a small part which is "poorly constrained".

But your query has reminded me that I should update the refs in the timeline - thanks! -- Philcha (talk) 10:19, 18 July 2008 (UTC)

Done. -- Philcha (talk) 10:47, 18 July 2008 (UTC)

Replaced one section title. Speaking of the references in the table, is there any clear way to tie them to what piece of the table they support? SDY (talk) 16:32, 18 July 2008 (UTC)

I hope "the table" is the timeline, otherwise I've really messed up. I've put refs against the critters and sub-periods but left the ones at the bottom. To my surprise I can if necessary remove the ones at the bottom, as the timeline template's notes allow the full mark-up with cite templates - many templates don't like such rich food. What do you think?

BTW I suggest this should not be regarded as a general precedent: some outer templates break if you give them complex inner mark-up; and sometimes the layout is so crowded that adding ref numbers may make them less readable. -- Philcha (talk) 17:21, 18 July 2008 (UTC)

Just looking at it there are some cosmetic problems too because of the superscript. The ones at the bottom are sort of redundant now. From the standpoint of "cite this" I'm honestly not sure if just giving the numbers elsewhere in the article (and citing them there) is sufficient for the graphic. I've dropped a question at WT:V. My gut feeling is that if the number is somewhere in the text and clearly cited there, the timeline (why do I keep writing table?) can just say it.

Mostly I just want to make it obvious which source is being used for the Doushantuo formation such that if someone has a question about why it seems so widespread on the timeline they know where the article got the information. SDY (talk) 17:37, 18 July 2008 (UTC)

I'm not keen on the superscripts either - I'm now working on Small shelly fauna and the timeline for that is going to be difficult enough anyway, because so many relevant things happen 525-520 MYA.

Given your objective of making it obvious which source is being used for the Doushantuo formation, perhaps it would be helpful to remove the superscripts and change the info at the bottom to e.g.

References for dates:

Doushantuo formation

What do you think? -- Philcha (talk) 18:35, 18 July 2008 (UTC)

That definitely meets the objective. SDY (talk) 19:43, 18 July 2008 (UTC)

Done. -- Philcha (talk) 20:37, 18 July 2008 (UTC)