Talk:Evolution of tetrapods

Comments from Ecapelle

• Expansion on the origin could add to the history of the article. More evolution information on pre-tetrapods.

• Palaezoic tetrapods: citations needed.

• Add to Cenozoic tetrapods (empty).

• Pictures of fin versus bony foot and the evolution among them could supplement the article.

Ecapelle (talk) 04:12, 24 March 2014 (UTC)

Usefulness of this article?

Is the article in it's current form actually necessary? It seems to just copy content from the tetrapod article. IMO, 1 of the articles should be changed or this article should be deleted. Blaylockjam10 (talk) 05:45, 9 April 2014 (UTC)

Looking at Talk:Tetrapod#Evolution_of_Tetrapods it seems like the intent was to spin off a section from the tetrapod article as a standalone article but the original article was never updated to summarise the spun-off section. I've made an attempt at that. To do things properly, the main "evolution of tetrapods" article will need its lead updated more in line with other "evolution of" articles and some of these changes should be merged in. On the other hand, I'm not sure this split really works as much of the remainder of the tetrapod article is about early tetrapods so needs the evolution section to put it in context.TuxLibNit (talk) 23:25, 29 May 2014 (UTC)

In this edit I merged in the changes others had made to the Tetrapod copy before I summarised it. In these edits I refactored the lead, section headings etc to fit a basic "Evolution of" style. So all the actions I identified above as "to do" are now done. I'm still not convinced that this split is working but at least both articles do now reflect the intent to split. TuxLibNit (talk) 00:28, 1 June 2014 (UTC)

Front page:

• Wikipedia:Today's featured article/April 25, 2015

Amphibians is running on the 25th, and this article is linked to in the blurb. It might make sense to improve the article before the 25th. --Harizotoh9 (talk) 13:23, 9 April 2015 (UTC)

First paragraph of lede needs work.

First it says "the earliest tetrapods derived from neither lobe-finned fishes nor ray-finned fishes." Everybody knows that humans, mammals, birds, dinosaurs, and all other tetrapods belong to the clade of lobe-finned fishes, also known as fleshy-limbed vertebrates. Even the reference cited says as much if you actually read it.

Next, the second footnote references a 1997 paper by Jenifer Clack which she has since retracted in light of the 2010 trackway discovery in Poland. Zyxwv99 (talk) 20:14, 2 May 2015 (UTC)

I have fixed the first error, but disagree with the second. I can find no formal retraction of Clack's 1997 paper, nor anything in the 2010 that contradicts either the paper or the statement on the page. Of the two trackways described in the 2010 paper, the authors explicitly hypothesize one is subaquatic, and make no mention of the other in that regard. However, the lack of tail or body drag suggests both are formed by aquatic walking. HCA (talk) 03:02, 3 May 2015 (UTC)

Two versions of the the 2012 edition of Clack's book Gaining Ground are available on Google Books. If you find the book on Google Books, then click on "more editions" you will see the 2002 and two 2012 editions. Try clicking on the bottom one of the 2012 editions. Then search on the word "Poland." Here you will see several pages updating and revising what she said in the 2002 edition, which was similar to the 1997 research paper. Fortunately, she didn't actually have to "retract" anything. That's because she never made any definitive claims to begin with. Instead, she criticized other paleontologists for over-interpreting the evidence, reading more into it than was there. She also acknowledged that future fossil finds could prove that they were right after all. In the 2012 editions she expresses astonishment at the new finds and acknowledges that the paleontologists she had criticized might not have been so wrong after all. She also mentions raindrop impressions and dessication cracks associated with the Polish tetrapod trackways, not something one would expect to find under water.

Although the 2010 paper from Poland is behind a paywall, the supplementary material is freely available. here "Trackway of a walking animal preserved on a semi-dry surface with raindrop structures" "tracks preserved on thin and dry microbial mats" "probably made by walking animals in subaerial conditions" "Trackway of a walking animal preserved on a semi-dry surface with raindrop structures". Zyxwv99 (talk) 21:32, 3 May 2015 (UTC)

So, there's a number of problems with the referenced statement. First, I think the statement about the inability to move on land is almost certainly incorrect, based on a variety of extant organisms which manage just fine with less specialized morphologies (e.g. walking catfish), as well as a forthcoming (but as yet unpublished) paper. That said, current trackways are highly ambiguous - even the cracked mud could have formed *after* the subaquatic trakcway bed was exposed due to tide or drought. On top of that, I'm extremely suspicious of any putative subaerial trackway that doesn't have belly/body drag or at least tail drag, as it would require not just the strength and morphology to lift the entire body clear of the substrate but also the entire tail. I propose we dodge the entire issue for now, and state something to the effect of how known trackways are ambiguous and the extent of the terrestrial locomotion of early tetrapods is unknown. HCA (talk) 22:29, 3 May 2015 (UTC)

You seem to be confusing "early" with "basal." Although the tetrapods that made the Polish trackways are chronologically early, the are universally accepted as nowhere near basal (and therefore not necessarily belly-draggers). The discovery of these trackways has revolutionized tetrapod studies in the same way as the asteroid theory has revolutionized our understanding of how the non-avian dinosaurs became extinct. If you want to sidestep the modern scientific consensus and continue with you own original research, please feel free. Zyxwv99 (talk) 20:50, 4 May 2015 (UTC)

I used the term "early" because that's a word in the sentence we're discussing; I am perfectly aware of the differences between early and basal, as well as the implications of these tracks. The sentences under discussion claim that "...little evidence supports the idea that any of the earliest tetrapods could move about on land..." because "...the known trackways do not indicate they dragged their bellies around. Presumably, the tracks were made by animals walking along the bottoms of shallow bodies of water." Now, logically think it through: If the Poland tracks were formed subaquatically, they do not refute that sentence. If the Poland tracks were made subaerially, the lack of a body drag suggests they were made by more morphologically derived tetrapods (in spite of their early date), which, in turn, means that they must have been preceded by more morphologically primitive (and yet undiscovered) forms of uncertain terrestrial capabilities. Again, the sentence is technically correct, because, while the trackway makers would be both terrestrial and chronologically early, they must have been preceded by still earlier undiscovered forms, unless you wish to argue that the Poland tracks (and tetrapod evolution) are the product of a Hopeful Monster.

The sentence could clearly be revised and clarified, but without leaping to conclusions not supported by the text of the suggested citation. HCA (talk) 02:51, 6 May 2015 (UTC)

You're right. Now I'm looking at this part of the first paragraph: "While most species today are terrestrial, little evidence supports the idea that any of the earliest tetrapods could move about on land, as their limbs could not have held their midsections off the ground and the known trackways do not indicate they dragged their bellies around. Presumably, the tracks were made by animals walking along the bottoms of shallow bodies of water." The first part makes total sense, just not for the reasons given. Tetrapod trackways in Scotland show belly-dragging alongside tracks made without belly-dragging. This is generally understood to mean that belly-dragging occurred when the tide was lower, while non-belly-dragging occurred with the tide was higher and much of the animal's weight was supported by water. Zooming out and looking at the big picture, we have no fossils or tracks of the first tetrapods. They are thought to have been fully aquatic, using their "four legs bearing digits" mainly as paddles, and only occasionally venturing onto land or water so shallow that they might have used their paddles in the manner of a seal with it's flippers. For the earliest tetrapods it's more a question of definition than evidence. Tetrapods are defined (by paleontologists, apomorphically) as tetrapodomorphs with four legs bearing digits, with the understanding that digits are found in fully aquatic animals (various ray-finned fishes) that don't use them for walking, much less on dry land. Zyxwv99 (talk) 18:43, 6 May 2015 (UTC)

IMHO, the problem is how to convey this simply and clearly in one or two sentences, without getting bogged down in details, since it's a lede. Maybe something like "While most modern tetrapods are terrestrial, the early tetrapods and their relatives may have had significant difficulty moving on land." It's a bit weasel-wordy, but it also captures that there's a range of terrestrial locomotion difficulty and outcomes, from "stuggles to make any progress at all" to "effective and consistent but slow and lumbering". It also avoids a definitive declaration (always trouble in paleo), but can be generally considered self-evident since terrestrial locomotion is so different from aquatic locomotion. HCA (talk) 19:53, 6 May 2015 (UTC)

As far as I can see, you have not corrected the first error in the lead. And a sole reference to a site with unknown authors is not adequate. Macdonald-ross (talk) 19:42, 3 July 2015 (UTC)

Harvard references

The Harvard references in this article are all dead. Zyxwv99 (talk) 02:34, 5 June 2015 (UTC)

Which ones are those? I don't see any URLs directed to harvard.edu, though reference 24 is dead ( Geological Survey of Canada (2008-02-07). "Past lives: Chronicles of Canadian Paleontology: Eusthenopteron - the Prince of Miguasha". Retrieved 2009-02-10.) HCA (talk) 14:21, 5 June 2015 (UTC)

Harvard referencing is a style of reference used in the Tetrapod article. Some references in this style were imported into this article, but without the second part that goes at the bottom of the article. For example, if you look at the first paragraph of the lede in Tetrapod then click on footnote number 2, you will come to a reference that just says "Clack 2012, pp. 125–7". If you click on that, it takes you down to the Literature section (below References) where it says "Clack, J.A. (2012). Gaining ground: the origin and evolution of tetrapods (2nd ed.). Bloomington, Indiana, USA.: Indiana University Press." If you click on the book title, it takes you to the book on Google Books. The advantage is that people can reference the same source multiple time, but each time with different page numbers.

Harvard referencing is explained at WP:HARVARD and Template:Harvard citation documentation#Author-date citation templates. If you look at this article in edit mode and search on "harv" you will see quite a few instances. If you try clicking on any of them, it only gets you to the first step, but not the second one where the main publication info is supposed to be located.

This style of referencing was already being used both in this article and the Tetrapod article before I got here. I expanded it a little in the Tetrapod article so that the literature section there now includes some of the more widely referenced books. I'd like to add Benton's Vertebrate Palaeontology (2009) to the list. Right now this article uses Benton (2005) which is a little dated and impossible to find in Google Books. Much of the 2009 edition is visible in Google Books preview mode. There is also a 2014 edition, but in preview mode it doesn't show the page numbers. For this reason, I would use 2009 wherever possible and 2014 only when necessary.

Zyxwv99 (talk) 19:43, 6 June 2015 (UTC)

Merging?

Sorry if I missed any fragment here touching on this, but I don't see the question of merging this with the "skeletal changes..." article covered here, so I'm making this subheading for it... and regarding which, I would humbly vote... Nay. To me, these are two topics which, though related, are absolutely not equivalent in either scope or focus, and I very much hope shall not be combined. Indeed, it's somewhat puzzling why the proposal was made in the first place. Saturn comes back around (talk) 22:01, 17 June 2015 (UTC)

Huge contradiction

The tetrapod article says "Tetrapods evolved from the lobe-finned fishes". The first sentence of this article says "the earliest tetrapods derived from neither ray-finned nor lobe-finned fishes." Is that not a huge contradiction? Makes me wonder whether this article has suffered some vandalism.75.163.204.203 (talk) 05:31, 10 July 2015 (UTC)