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Featured status[edit]

This article is very close to featured article status. Have the editors who worked on it asked for peer review?—Encephalon | ζ | Σ 13:58:00, 2005-08-14 (UTC)


I've redirected the imedance link to point to impedance mismatch as the old link was redirecting to electrical impedance. Although it's not entirely appropriate, the old link was less so. — Graibeard 10:05, 30 November 2005 (UTC)

Image and Taxonomy[edit]

This article is very good, I might submit it to peer review. However, I think the image would be better if it were a living tetrapod, just for aesthetic reasons. Also, I'm going to simplify the sub-group section of the taxobox somewhat and create a more in-depth classification in the main body of the article.Dinoguy2 23:08, 16 January 2006 (UTC)

The classification confuses me. Most of the ranks intermediate between Tetrapoda and Amniota are called "family", which I thought only referred to a level below classes. I know that there are problems resolving traditional classification and cladistics, but I haven't really seen the "family" applied like this. Ardric47 00:52, 16 March 2006 (UTC)
This is a minor drawback of the mixed linnean/cladistic classification we've been using. Traditionally, those would be families below the class level, and can still be considered that. The reality is that one family evolved into another, into another, into a subclass, etc. The system we're using now basically allows a low rank to have high-rank descendants. This works for most groups, but can be confusing for things like primitive tetrapods, which have an extremely steep evolutionary gradient leading up to a few major traditional groups.Dinoguy2 02:05, 16 March 2006 (UTC)
What about terms from McKenna/Bell like "legion", "supercohort", or "mirorder"...or do those not apply here? Ardric47 02:47, 16 March 2006 (UTC)
They could be used, but I don't think most of the clades seperating those families out even have names. Until/if somebody finds names for them, I'm just going to streamline this down to something more simple. The progression is still reflected in the order of the families, so hopefully the point will still be clear.Dinoguy2 03:16, 16 March 2006 (UTC)
I laughed at the image. Wouldn’t it be better if you could see, and count, the creature’s legs? Wil 20:46, 29 April 2007 (UTC)

Phylogeny of early tetrapod diversification[edit]

This section needs a lot of work. More references are needed because many other paleontologists worked on this question (Milner, Carroll, Anderson, Pawley, Marjanovic, and myself, among others), and much of the text in the note is factually wrong (e.g. none of Ruta's analyses put Lissamphibia within Lepospondyly, but my anayses did). Michel Laurin (talk) 00:21, 1 January 2013 (UTC)

Something doesn't look right about the cladogram and its references. Originally it was supposedly based on a paper by Ruta el al, only the cladogram showed Laurin's contentious lepospondyl theory of lissamphibian origins. Even though the paper in question mentions that theory and reproduces Laurin's cladogram, attributing it to Ruta seems a bit much, especially since Ruta has been one the harshest critics of this theory. Then somebody added two more references to Laurin.
The main point is that this is a contentious theory. If 50% of scholars support theory A, 25% support theory B, 12.5% theory C, etc., there's nothing wrong with mentioning all three, so long as twice as much space is devoted to A as to B. Right now all we have is theory B and it's not even a close second. Zyxwv99 (talk) 21:26, 19 June 2015 (UTC)
Indeed, combining features of cladogram derived from works that yielded conflicting topologies is unorthodox. However, I disagree about how contententious issues must be dealt with, especially when the number of scientists involved is very low. There are about 6 specialists of this question worldwide, two of which support the lepospondyl hypotheeis. This is indeed a minority, but what does it mean with such low numbers? Also, don't forget that every theory that proved right was initially supported by a minority (including the now widely-accepted ideas that the earth is approximately spherical rather than flat, and that it turns around the sun, rather than the reverse). Majority has never been a safe guide for reliability in science. — Preceding unsigned comment added by Stranger forever (talkcontribs) 07:08, 20 June 2015 (UTC)
I'd like to start by fixing the cladogram I put in yesterday to show only relationships between modern forms. The next step is to convey, by words and by cladogram, what everyone agrees on, and nothing else. No fossil species, genus, or family of early tetrapods can be confidently assigned to crown tetrapods, to either of the two major subclades of crown tetrapods (amphibians and reptiliomorphs), or even to amniotes, except for those that have been confidently identified as lissamphibians, saurapsids, or synapsids. Since known lissamphibians only date back to the Early Triassic, saurapsids and synapsids to the Late Carboniferous, the result is that nearly all Carboniferous tetrapods, and a large percentage of Permian tetrapods, are of unknown affiliation. Then we can list forms that are of disputed affiliation, e.g., baphetoids, temnospondyls, embolomeres, etc. After that we can put in cladograms showing different points of view.
As for the "majority rule" thing, this is an issue of WP:UNDUE. "Giving due weight and avoiding giving undue weight mean that articles should not give minority views or aspects as much of or as detailed a description as more widely held views or widely supported aspects." In this case it's not how many paleontologists are promoting which view, but how widely accepted those views are. It becomes a problem when academics or their acolytes use the Wikipedia to promote contentious theories to the exclusion of the mainstream view. Zyxwv99 (talk) 20:24, 20 June 2015 (UTC)
(I'm double posting here.) The Paleozoic origins of lissamphibians is one of the more notable paleontology questions of our time. On Google Scholar Paleozoic+lissamphibia gets 177 hits just for papers published since 2011. Temnospondyl+lissamphibia get 185. Lepospondyli+lissamphibia gets 57.
In the book Amphibian Evolution: The Life of Early Land Vertebrates by Rainer,’’ R. Schoch says, “Here I follow the majority view on the origin of Lissamphibia, which holds that temnospondyls, members of a speciose clade encompassing almost 300 species, form the stem-group of lissamphibians (Bolt 1969; Milner 1993; Ruta and Coates 2007; Sigursen and Green 2011; Maddin et al. 2012).
I’m surprised you forgot to mention Michel Laurin as one of the advocates of the Lepospondyl hypothesis. He’s the most notable proponent of the Lepospondyl theory. Looking at your contribution history, I see you’ve made just under 100 edits in the last three years. A huge percentage of them seem to involve citing Michel Lauren as a reference. On the French Wikipedia you have edited the Michel Laurin article. Don’t worry, I’m not accusing you of being Michel Laurin. Besides, we all cited references that we’re familiar with. Also, in reviewing your contribution history, I’m not seeing anything nefarious or even POV. I was just curious. Zyxwv99 (talk) 23:33, 21 June 2015 (UTC)

A new tetrapod[edit]

An important tetrapod that was living is shallow water has been discovered. It is called Tiktaalik roseae. (Ted Daeschler from The Academy of Natural Sciences in Philadelphia, Neil Shubin from University of Chicago, and Farish A. Jenkins, Jr. from Harvard University) Illustrations:

  • Note that there are a couple of broken external links.

Lead paragraph[edit]

The lead paragraph seems to studiously exclude the term "reptile", instead talking about "lizards, crocodiles, dinosaurs", and mentioning snakes later. It doesn't mention turtles. Since the term "reptile" is very familiar, more inclusive, and not too shocking scientifically (= Sauropsids other than the birds), why isn't it mentioned? --Macrakis 14:38, 11 January 2007 (UTC)

Lion Picture[edit]

I dont get the lion picture, yes there is talk about vertebra, humans etc... but no lion... I think therefore the lion picture is not needed in the artical, but instead a reference picture to a human would. Scubafish (talk) 09:35, 9 June 2008 (UTC)

No references for over a year?[edit]

I notice that this article has suffered from a lack of references for over a year. WP:V requires every fact to be referenced. So, are references going to appear, or should this article be put up for deletion? Shinobu (talk) 13:11, 13 June 2008 (UTC)


I removed the lion picture because it made no sense to show a nice gradual evolution of sea creatures moving to land and then jump drastically to a photo of a lion. In times like these when creationists use any toe hold to attack science we shouldn't give them such an easy target. —Preceding unsigned comment added by (talk) 04:27, 18 June 2008 (UTC)

The new Komodo Dragon pic is awesome. Its my favorite animal. Pure win. —Preceding unsigned comment added by (talk) 19:22, 22 December 2009 (UTC)

Infact, it was added this year. I still love it. It also replace a Salamander, by way.

Good Gravy[edit]

I am not a scientist or anything of the sort, but please, give me a break with this article:

Since their blood contained more salt than freshwater, they could simply get rid of ammonia through their gills. When they finally returned to the sea again, they could not recover their old trick of turning ammonia to urea, and they had to evolve salt excreting glands instead. Lungfishes do the same when they are living in water, making ammonia and no urea, but when the water dries up and they are forced to burrow down in the mud, they switch to urea production. Like cartilaginous fishes, the coelacanth can store urea in its blood, as can the only known amphibians that can live for long periods of time in salt water (the toad Bufo marinus and the frog Rana cancrivora). These are traits they have inherited from their ancestors.

And not a single reference! Do you wiki-whateveryouares just make this stuff up as you go along? "Ammonia to urea", switching back and forth, losing their ability to do this and that...come on. Do you actually purport these notions to be SCIENCE???

Get out of here. —Preceding unsigned comment added by (talk) 05:49, 22 September 2008 (UTC)


I have marked (I hope correctly) the Evolution section of this article as having the wrong type of tone for a Wikipedia article. It is very conversational and phrases like "maybe we shouldn't underestimate the early juvenile tetrapods either." just don't feel like I'm reading Wikipedia, but perhaps the script of a low-brow television documentary. My first is in ptarmigan (talk) 23:58, 29 October 2008 (UTC)

Fair point, I've removed the tag and fixed what seem to me obvious issues. Be Bold! and fix any others you see, or delete offending paragraphs with a suitable explanation. Some of the stuff looks rather like original research so citations are needed, and in general inline citing would be a great improvement. It'll be much appreciated if you can help with this! . dave souza, talk 11:08, 16 November 2008 (UTC)

Fresh start, 2010[edit]

This article has multiple problems.

  • Tetrapoda is a major division of the vertebrates and constitute the major extant terrestrial fauna, yet this article does not mention any of the extant groups other than in passim, with next to nothing about the evolution of the group save within the basal labyrinthodont groups.
  • The article is very long (over 51 kilobytes), and much of the text is rather wordy. Several of the topics are covered in depth in other articles.
  • Some parts of the article seem to be about pro-tetrapod Tetrapodomorpha rather than tetrapods.
  • References are mostly lacking throughout.

I propose a rewrite and tightening up of the articles, and moving topics of more general interest to their own topics. Petter Bøckman (talk) 10:06, 25 October 2010 (UTC)

I agree. There's a lot of good information here, but most of it's unreferenced. Maybe we could move most of the information in "Anatomical features of early tetrapods" and the beginning of the "Evolution" section to different articles. I'm in favor of making a new article, Origin of tetrapods, for this information, which relates to the fish-tetrapod transition. The tetrapod article, meanwhile, can focus on all tetrapods in general, especially living ones. Smokeybjb (talk) 19:57, 25 October 2010 (UTC)
Most of the info (when sourced, and frankly condensed a bit) are good candidates for origin of tetrapods, some of the anatomy bits too. The basic framework isn't bad, and can serve as a basis for a comparative anatomy section for the whole range of tetrapods. I've got my trusty ol' Romer and Hilderbrand & Goslow ready ;-) I think the evolutionary history can stay much as it is, but the amphibian/reptilian bit of it could be condensed a bit as well. Perhaps some of it can be used to augment Reptile#Evolutionary history.
I think a good starting point would be to find out what we would like the Origin of tetrapods article to look like, and start to transfer bits of the article. For the time being, the two can share this page, until we see how they start to shape up. I would love to find good use for some of your illustrations too! Does it sound OK to you? Petter Bøckman (talk) 20:26, 25 October 2010 (UTC)
Sure, some of my illustrations might be useful. If you have any requests, I can always make some new ones. We can look at articles like Origin of birds and Evolution of mammals as guides to a tetrapod origins article. It should probably include a section on anatomy, which, for the most part, can be transferred from the tetrapod article so long as we add lots more references. We could also touch on classification, explaining the difference between tetrapods and tetrapodomorphs, and explaining all the other groups, Linnean and phylogenetic. A history of study section would probably be a good idea, too. Smokeybjb (talk) 00:23, 26 October 2010 (UTC)
I think the Evolution of mammals is the more relevant of the two, in that it like mammalian evolution is well stocked with fossils and with little academic dispute over who is the ancestor of who. I guess we'll just have to start doing cut-paste work and see where we end up. Petter Bøckman (talk) 09:30, 26 October 2010 (UTC)
Perhaps this article should be a lot shorter. Footprints found at the Zachelmie Quarry in Poland push back four-footed walking some 20 million years -- much earlier than any of the creatures illustrated here. Bazl406 (talk) 17:03, 10 January 2011 (UTC)
Link to the relevant papers? --Cyclopiatalk 17:06, 10 January 2011 (UTC)
Papers here: [1][2] Petter Bøckman (talk) 11:33, 12 January 2012 (UTC)
  1. ^ Niedźwiedzki & al. (2010): Tetrapod trackways from the early Middle Devonian period of Poland. Nature no 463, pp 43–48 DOI: 10.1038/
  2. ^ Uppsala University (2010, January 8). Fossil footprints give land vertebrates a much longer history. ScienceDaily. Retrieved January 8, 2010, from /releases/2010/01/100107114420.htm

External links[edit]

There's far too many external links on this page, some of which may be most useful as external links and some of which may be best incorporated as references. I'm not sure which to keep or which to integrate so I've moved them to this talk page for people more familiar with the topic to sort through. If others disagree with this removal, feel free to re-add the links but please consider the advice at Wikipedia:External links. Otherwise, re-add the {{External links}} tag but with an updated date parameter. ClaretAsh 14:01, 13 February 2012 (UTC)

External links
Devonian tetrapods
Carboniferous tetrapods


The universal tetrapod characteristics of front limbs that bend backward at the elbow huh? my elbows don't bend backward!! (talk) 14:18, 23 March 2012 (UTC)

Actually it does, it is just a matter of whet angle you see things from. If you were standing on all four, and bent your elbow without lifting the hand (i.e like lowering yourself during push-ups), the elbow joint is flexes backwards. The normal thing to say about a human is that the lower arm flexes upward or forward, but humans is a special case, being bipedal and all. When reading these descriptions, one must take into account a kind of generalized tetrapod body plan, like that of a lizard or salamander. In them, the elbow most certainly bends backwards. Petter Bøckman (talk) 14:37, 23 March 2012 (UTC)
Actually most tetrapods have wrists that function as simple hinge joints and elbows that can do the same but also rotate. Our knees and ankles are the opposite, with hinge-like knees and rotating ankles. This was not the case in the earliest tetrapods, but evolved independently in each lineage as it became terrestrial, probably as a result of common inherited biomechanical factors Zyxwv99 (talk) 22:24, 1 August 2015 (UTC)


Please see the discussion at Template talk:Taxonomy/Teleostomi, where we are discussing how to handle the taxon Eugnathostomata. Bob the WikipediaN (talkcontribs)

new paper on ichthyostega lim joint mobility[edit]

Abstract: The origin of tetrapods and the transition from swimming to walking was a pivotal step in the evolution and diversification of terrestrial vertebrates. During this time, modifications of the limbs—particularly the specialization of joints and the structures that guide their motions—fundamentally changed the ways in which early tetrapods could move. Nonetheless, little is known about the functional consequences of limb anatomy in early tetrapods and how that anatomy influenced locomotion capabilities at this very critical stage in vertebrate evolution.

Here we present a three-dimensional reconstruction of the iconic Devonian tetrapod Ichthyostega and a quantitative and comparative analysis of limb mobility in this early tetrapod. We show that Ichthyostega could not have employed typical tetrapod locomotory behaviours, such as lateral sequence walking. In particular, it lacked the necessary rotary motions in its limbs to push the body off the ground and move the limbs in an alternating sequence.

Given that long-axis rotation was present in the fins of tetrapodomorph fishes, it seems that either early tetrapods evolved through an initial stage of restricted shoulder and hip joint mobility or that Ichthyostega was unique in this respect. We conclude that early tetrapods with the skeletal morphology and limb mobility of Ichthyostega were unlikely to have made some of the recently described Middle Devonian trackways.

It would be nice if somebody could dig up the whole paper, sinse the trackway bit in the abstract is very intresting.Aliafroz1901 (talk) 11:01, 4 July 2012 (UTC)

Wolud be nice to include but I do not have access to this paper. Somebody could add a few bits based on the abstract for now. MMartyniuk (talk) 12:55, 13 July 2012 (UTC)
I've requested a copy at resource exchange for the Tiktaalik reconstruction. I'll add something if I get access to the paper.-- OBSIDIANSOUL 21:55, 23 July 2012 (UTC)
I've added it to the from fins to feet section. Not sure if that's the best place. Feel free to relocate.-- OBSIDIANSOUL 03:12, 24 July 2012 (UTC)
Seems good to me. In the fullness of time, I have plans to move the whole bit about the evolution to a "Evolution of tetrapods" article, leaving this article to discuss the features common to all tetrapods. Petter Bøckman (talk) 11:58, 24 July 2012 (UTC)
Unfortunately nothing specific seems to be of much use to the Tiktaalik reconstruction though. As for the trackway bit, the study concludes:
Given our results, could an Ichthyostega-like early tetrapod have produced similar trackways to some of those recently described from the Middle Devonian? All available evidence fromlimb joint mobility and axial anatomy indicates that such animals could not have made symmetrical gait ‘foot’ prints. In particular, these early tetrapods probably lacked the necessary rotary motions in their limbs (and perhaps lateral flexion of the vertebral column) to push the body off the substrate and progress using alternating limb movements. Maybe as yet unknown tetrapod species (or known taxa that currently lack postcranial material) with different joint mobility and axial anatomy made these traces; available data cannot yet answer this conundrum. Nonetheless, the analysis presented here supports the possibility that Ichthyostega-like animals could produce synchronous (parallel) trackways, as our findings indicate that such a trace should consist of a series of bilateral forelimb impressions.
-Pierce, S. E.; Clack, J. A.; Hutchinson, J. R. (2012). "Three-dimensional limb joint mobility in the early tetrapod Ichthyostega". Nature. 486: 523–6. PMID 22722854. doi:10.1038/nature11124. 
-- OBSIDIANSOUL 12:18, 24 July 2012 (UTC)
I suppose what this study tells us is that the terrestrial locomotion of Ichthyostega was unique. It has either appeared independent of the more salamander-like walking pattern seen in the Zachełmie quarry footprints, or it has evolved from it. Petter Bøckman (talk) 08:02, 25 July 2012 (UTC)


Citing Broili 1913 in the taxobox as the authority for the name Tetrapoda seems doubtful. Though I have not been able to obtain the text of Broili's 1913 papers (cited by Roy L. Moodie in 1915), I note that Friedrich von Huene uses the term in quite the modern sense in "The skull elements of the Permian Tetrapoda in the American Museum of Natural History, New York", written in 1912 and translated into English in 1913. Among other animals, the paper discusses the familiar tetrapods Diadectes, Captorhinus, and Dimetrodon. Von Huene exhibits no concern that his readers might fail to understand the term Tetrapoda in his title, which suggests that it was in common use in 1912. He does refer to work by Broili, but he does not attribute the term Tetrapoda to him. Is there justification, nonetheless, for leaving Broili 1913 as the authority in the taxobox? If not, can a better authority be suggested? Peter M. Brown (talk) 17:28, 21 September 2012 (UTC)

This article cite Tetrapoda Haworth, 1825. Same as this. Burmeister (talk) 21:59, 21 September 2012 (UTC)
I believe that the term actually goes back to the classification of mammals by Aristotle, who distinguished the Tetrapoda from the Dipoda and the Apoda. Richard Owen (1859) so attributes the term and does not mention that it had acquired a more inclusive meaning by his day. We cannot use Haworth without some reason to think that he was using the term in a sense closer to the current one than to Aristotle's. Peter M. Brown (talk) 01:27, 22 September 2012 (UTC)
Pretty sure Aristotle predated Linneaus... aren't names prior to Systema Natura considered ineligible? I know the ICZN itself does not cover anything above the Family group but I've never seen a name cited to any author pre-dating the 18th century. "We cannot use Haworth without some reason" The only reason we need to use anything is a majority of current and verifiable sources, whether or not those sources are themselves justified is not really our problem. Unless there is a current verifiable source which validly argues that the consensus is wrong in 'legal' cases like priority. MMartyniuk (talk) 09:36, 22 September 2012 (UTC)
Owen is a reliable source. Do read his comments. He would not have spoken as he did if his 1859 audience thought of Tetrapoda as a group that included amphibians. Peter M. Brown (talk) 15:23, 22 September 2012 (UTC)
With Huene & Gregory 1912 using Tetrapoda (and apparently not even as a new name), there clearly is no justification for leaving Broili 1913 in the taxobox. (I think I've read Broili 1913, and it doesn't use the name as new either.) Aristotle, on the other hand, is completely out of the question because names that predate the 10th edition of Systema Naturae are (in zoology) only eligible if they're in Clerck's (1757) book on Swedish spiders.
Haworth 1825 clearly does not count, because that work uses the name Tetrapoda for four-footed lizards only, with no connection to the modern concept.
However, it's a good question if Tetrapoda was ever erected as a new name. I've seen papers by Broili (1903 or 1904, I don't remember) that use the German vernacular, Tetrapoden, with no indication if a formal name Tetrapoda existed. Perhaps the vernacular form became so widespread that people ended up assuming a formal Tetrapoda must exist and started using it...
I'll change the taxobox to say "unknown before 1912 (see talk page)".
David Marjanović (talk) 11:38, 3 October 2012 (UTC)
Perhaps it would be an idea to have a small section in the article devoted to authority, if it does not violate WP:OR? Petter Bøckman (talk) 14:04, 3 October 2012 (UTC)
In research papers on Google Scholar it's usually "Tetrapoda Goodrich 1930", occasionally "Tetrapoda Haworth, 1825 sensu Goodrich 1930". What we have now "authority unknown, before 1912" looks like OR. Zyxwv99 (talk) 15:59, 15 February 2015 (UTC)
Clack says it's Goodrich 1930 here. That's good enough for me. Zyxwv99 (talk) 20:59, 12 June 2015 (UTC)
The problem here is that "tetrapod" is simply a vernacular Latin word that's been co-opted by a scientific name (see also "quadruped"). If we currently had a formal taxon named "Quadrupedes", we would not need to cite anybody who ever wrote the phrase "four-footed" in Latin as an authority. If Google Scholar sources list Goodrich 1930, then this is what should be used unless there is a published analysis disputing this. Dinoguy2 (talk) 16:17, 26 July 2015 (UTC)

No {{Page needed}} in Zimmer book?[edit]

In Tetrapod#Origin, it is claimed that the "transition from a body plan for breathing and navigating in water and a body plan enabling the animal to move on land involved a series of changes taking place throughout most of the 56.8 million years that make up the Devonian period." The reference is to Carl Zimmer, At the Water's Edge (1998). In this edit on 19 September, I tagged the claim with {{Page needed}}: where in this 290-page book is there support for the claim? As there was no response, I deleted the claim on 26 September. The following day, my edit was reverted; the summary reads "Reverted deletion, the whole book is about this, it's not a single page or few pages."

I have the book before me. Chapters 1–4 do relate to the tetrapod water-to-land transition. 5–9 seem mainly to be concerned with whales. Chapter 10 concludes the book, drawing on previous material to advance some general claims about macroevolution. In view of the extended discussion of whales, "the whole book" is certainly not about something that happened in the Devonian. A page scan using the Amazon preview reveals that the number 56.8 occurs nowhere. Support for the Wikipedia claim is presumably to be found in the first four chapters, but one should be able to verify a claim without plowing through the 116 pages involved in detail; I have skimmed them, which is more than I think should be expected, and I do not see the claim well supported. If this is what the whole four chapters are about, one might expect to find the claim at the beginning, but Chapter 1 opens with an account of Richard Owen's boyhood. I submit that verifiability is lacking.

Peter M. Brown (talk) 22:33, 13 October 2012 (UTC)

I'll look into it. On the other hand, the trackway from the Zachełmie quarry have put a dent in conventional wisdom on the matter. A full rewrite of the section may be necessary. Petter Bøckman (talk) 12:23, 14 October 2012 (UTC)
Why a full rewrite? Doesn't Tetrapod#Denizens of the swamp provide an adequate account of the Zachełmie trackway? Peter M. Brown (talk) 15:22, 14 October 2012 (UTC)

Wojciechowice trackways[edit]

Szczecin or Oder Lagoon, on the Polish-German border

In Tetrapod#Origin, it is claimed that the transition to "a body plan enabling the animal to move on land" occured in the first half of the Devonian. In support, an article is cited which argues from the Wojciechowice trackways for some anatomical developments. It does not claim, however, that these enabled any vertebrates to move about on land. The closest it comes is to note that the environment might have been intertidal and that, if it was, it would have "allowed marine ancestors of tetrapods gradually to acquire terrestrial competence". The claim is not made, however, that the environment was in fact intertidal; it might have been lagoonal and, as the Lagoon article notes, the term is often restricted to bodies of water with little or no tidal flow. Peter Brown (talk) 15:17, 23 October 2012 (UTC)

True, the tracks could have been made by a half-submerged animal. What about something to the effect of "the basal components of which ...", indicating that while the critter had lungs, feet and toes, it wasn't really a dry land animal. For its fundamentally aquatic existence, we have Clack to support that true terrestrial life didn't really evolve until the Carboniferous. Petter Bøckman (talk) 20:13, 23 October 2012 (UTC)
There's been a lot more research on this since 2010. They've revised the date to 391 mya based on a more thorough review of the conodonts above and below the track-bearing strata. They found that these conodonts were not just a particular subspecies, but a new species with a match in Kazakhstan that's been radiometrically dated. Next, the found out that it was definitely a lagoon with an average depth of one to two meters, with marine organisms characteristic of saltwater environments, but with occasional influx of fresh water. Average water temperature 30° C (86° F). There were low islands with sparse vegetation. They can't identify the plants as they have found only roots, but the were vascular. (The first trees would have been evolving right about then.) The tetrapods themselves are now thought to have been fully aquatic. Clack has contributed a paper on this, specifically addressing the Polish trackways. Her point is that four-footed walking and terrestriality are two completely different things. The theory now is that these were fully aquatic animals walking underwater, on the bottom, but that they occasionally stuck one foot out of the water, planted it on dry land, leaving an occasional single footprint, then went back in the water. Zyxwv99 (talk) 23:39, 11 May 2015 (UTC)
Doing a little more digging on this, it looks like the dry tracks (three trackways on different strata) were all made by animals described as juvenile tetrapods, 50 cm long. They were made on bacterial mats that cracked when stepped on, leaving a broken-glass pattern. No anatomical details of the feet were preserved, and no digit impressions. The gait was diagonal sequence except one trackway that switched to ladder-like. There was no evidence of belly or tail dragging. The reason for supposing that they were tetrapods is that they were found at the same site as confirmed tetrapods, and because no other animal is known that could have left such trackways. The lack of belly drag could conceivably be explained by an Ichthyostega-like ribcage, but not the lack of tail drag. Since tetrapods with rigid spines at this date would overturn the standard model of monophyly within Tetrapoda (including fossil forms), it sets the bar very high on the strength of evidence required. This may explain why the dry tracks haven't been getting much attention from paleontologists, even though they consider the underwater tracks to be of tremendous importance. Zyxwv99 (talk) 00:01, 19 May 2015 (UTC)

New attempt at taxonomy[edit]

The newly installed taxonomy section is a great improvement over its predecessors and is much superior to many on Wikipedia. Most importantly, the limitation to infraclasses makes it short enough that the general reader is unlikely to be put off by a tiresome list down to the family or genus level. All taxa are wikilinked, so a reader who is really interested can drill down to subordinate levels. Each taxon is accompanied by an intelligible characterization using common names. In the interest of neutrality, perhaps a note should be added that some systematists would object to the use of paraphyletic taxa, with the birds excluded from Archosauria for example, but an insistence on monophyly would produce a far less approachable classification. Peter Brown (talk) 18:38, 4 December 2012 (UTC)

The classification is more or less the most modern version of the classical classification I could find. I have tried to make that clear in the introductory text, but we could put in a sentence or two on the use of groups in their traditional paraphyletic sense. Petter Bøckman (talk) 12:00, 5 December 2012 (UTC)


I am doubtful about the inclusion of the Trituberculata as an infraclass within Theria. A date-limited search of uses of the term since 2000 on Google Scholar shows the word used only as a species name: as a plant (Portulaca trituberculata) or as an arthropod (Hesslandona trituberculata, Tetragnatha trituberculata, and Randallia trituberculata). According to Tatarinov (1977), Cope introduced the name as a mammalian taxon in 1883, but as an order, not an infraclass. In any case, strictly historical uses — those not found in recent work — should not be used unless indicated as such.

Another problem is inconsistency with other Wikipedia articles. Theria indicates that the taxon consists just of the Eutheria and the Metatheria, and Metatheria concurs. Hildebrand and Goslow apparently have another definition for Theria, a definition that allows Trituberculata to be included as a third infraclass under Theria. Someone who has access to their book (I don't) should note that other definition in the Theria article. If Theria is defined in terms of Trituberculata, then it becomes important to improve the latter article, which provides no useful delimitation of the group.

Can the line for Infraclass Trituberculata simply be omitted, with a note in the reference that Hildebrand and Goslow include it? Or would this leave some mammals out?

Peter Brown (talk) 18:38, 4 December 2012 (UTC)

I was a bit puzzled over the Trituberculata as well, but the Trituberculata article support H&G's use. Again, I think we are in the middle of the raging phylogenetic/Linnaean/crown-group/traditional war. I think it would be better to add a note rather than to remove the link. Petter Bøckman (talk) 12:00, 5 December 2012 (UTC)


Wow, fascinating to see a publication in the 21st century not only using Odontognathae, but including them in Neornithes! It's like finding a living cynodont or something... I don't have this source--is there any reasoning behind that or have they not read any literature on prehistoric birds since Marsh? MMartyniuk (talk) 20:23, 4 December 2012 (UTC)

It's quaint, isn't it? It is mostly a continuation question I think. It's a book mostly in Romer's comparative anatomy vein, hence they have used a conservative classification that serve that purpose rather than striving for the newest. They don't strike me as particularly unfamiliar with relevant literature. Petter Bøckman (talk) 12:00, 5 December 2012 (UTC)
What is the purpose of including hesperornithiformes and ichthyornithiformes among modern bird,s exactly? The idea that they are close relatives of modern gulls and loons was debunked over half a century ago and is no longer supported by a single worker in the field. There would need to be a pretty good reason for knowingly including incorrect information in a supposedly scientific work. Or are they using Neornithes in an idiosyncratic way equivalent to some uses of Ornithurae (i.e. the taxon containing Hesperornis and modern birds)? MMartyniuk (talk) 12:53, 5 December 2012 (UTC)
I suppose it's the latter. It is what Romer did (his description is "birds with a modernized skeleton"). Now, he did not have the Enantiornithes, (not known in his days), so he has tailed birds without carina in one subclass and those without tail but with carina in another. My guess is they elected to continue that tradition. There's nothing wrong in principle with extending Neornithes back to round up all that doesn't fall in the other subclasses, except just this little branch of the tree seems to be what the crown-group people consider their personal home turf.
I have two suggestions to solve this:
1) Ad a note that this unit is now usually called Ornithurae, with a suitable source.
2) Drop all infraclasses from the list (this will also solve the Theria problem). Petter Bøckman (talk) 18:48, 5 December 2012 (UTC)
Both are workable solutions that have been used elsewhere. I'd support #2 though, since there's no real reason to be getting into infraclasses at such a high-level page (and infraclasses vary widely from taxonomist to taxonomist anyway). Gotta hand it to Romer--even without 99.99% of currently known fossil bird diversity, he agrees with current evidence that the carina appears just about the same time the tail is lost. MMartyniuk (talk) 19:47, 5 December 2012 (UTC)
Yeah, I think you're right. I'll just let Peter Brown chime in, then I'll remove the infraclasses unless he has a better suggestion.Petter Bøckman (talk) 20:19, 5 December 2012 (UTC)
Yes, that's best. Besides the problems noted, Ichthyosauria is pretty much always called an order, not an infraclass, so all three breakdowns of subclasses into infraclasses are problematic. Peter Brown (talk) 22:16, 5 December 2012 (UTC)
Fixed. I also think the section should be merged with the section "Linnaean classification" above it. They cover more or less the same ground. Petter Bøckman (talk) 08:12, 6 December 2012 (UTC)
I agree. As used, there's currently no difference between "groups" and "Linnaean taxa". MMartyniuk (talk) 20:13, 6 December 2012 (UTC)

I have combined the two, and added a bit of taxonomic history. See if you like it.

I'm not too happy about the tree from Ruta & Coats though. It is extremely detailed with regard to labyrinthodonts, but give no details of living groups. Also, the root of the tetrapod tree being as fuzzy as it is, I think the note below the tree should come further up, perhaps several simplified trees should be shown. We may also consider a small section on the various definitions of tetrapoda. The article currently seem to rely on either the traditional or Clack/Ahlbergs definition, but there are others, particularly crown groups definition which (if we are to believe Laurin) would leave the majority of animals discussed here outside tetrapoda. Petter Bøckman (talk) 10:31, 7 December 2012 (UTC)

Terrestriality in Acanthostega and Ichthyostega[edit]

According to the subsubsection Devonian tetrapods, "the earliest tetrapods, such as Acanthostega, were wholly aquatic and quite unsuited to life on land." This surely applies to Ichthyostega since, according to the section Anatomical features of early tetrapods, Ichthyostega was the earliest of the true tetrapods. Yet the subsubsection From fins to feet is inconsistent with this as it discusses Ichthyostega's "most likely method of terrestrial locomotion". If the earliest tetrapods were wholly aquatic then there was no terrestrial locomotion. Which better reflects scientific consensus? If there is no consensus, then the text should say, e.g., that Clack argued, not that she showed, that the earliest tetrapods were wholly aquatic. Peter Brown (talk) 21:35, 13 December 2012 (UTC)

Not quite. Acanthostega lived at the same time as Ichthyostega, but in every phylogenetic analysis it represent an earlier branch on the line. The evolution of terrestrial life must have been gradual (it really is a "great step", requiring a large amount of smaller adaptations), so it stand to reason that later groups were better at moving on land than earlier ones. We also have the problem that terms "life on land" and "terrestrial" (and even "primarily") aren't exactly precise terms. Do a mudskipper "live on land"? Is it "well adapted for terrestrial locomotion"? Are the giant slamanders "terrestrial"? What about a crocodile? In addition, different authors have different emphasis. Clack is interested in when and in what groups terrestriality evolved, Ahlberg is an anatomist and is looking for toes, Laurin want to draw phylogenetic trees. They ask different questions, and thus they get different answers. We end up having a situation where one is talking about terrestrial adaptations in a creature an other claims were basically a fish with toes utterly unsuited to life on land.
Having said that, Ichthyostega obviously had features that only makes sense of it occasionally dragged itself up on land. The legs of Acanthostega could possibly be used to drag it over land, but they could also have been used to push the animal along the bottom in very shallow water. Did it ever move on land? We don't know. In Ichthyostega's case we can be fairly sure it did. Whet we don't know is if it evolved its landlubbing habits on its own, or if they were common to the "post-Acanthostega" line. Whatever the case, it's movements appear to have been unique, it is fully possible Ichthyostega was the first land vertebrate of a line the ultimately failed, and that terrestriality only appeared many million years later. Petter Bøckman (talk) 23:10, 14 December 2012 (UTC)
All the same, the article is inconsistent, and the general reader will not be aware of these distinctions. Even if Acanthostega is more basal, Ichthyostega is one of the earliest tetrapods except perhaps in an unacceptably technical sense of "earliest". According to the Ichthyostega article, Clack agrees that the genus spent some time on land. Perhaps she did not claim the earliest tetrapods were wholly aquatic; perhaps the article misrepresents her view? Tetrapod#Palaeozoic tetrapods is abominably short on citations. Peter Brown (talk) 23:49, 14 December 2012 (UTC)
My idea with this article was to move out the evolution bit to a separate article, and expand the content to cover the whole of tetrapoda, not only the basal part. Unfortunately, life intervened. In my view, the Tetrapod#Palaeozoic tetrapods section should be cut down to a summary. Petter Bøckman (talk) 01:40, 15 December 2012 (UTC)
As I understand you, Ichthyostega must have been descended from earlier Acanthostega-like beasties that were, indeed, wholly aquatic. Since they were earlier than Ichthyostega, they must also have been earlier than Acanthostega, since these genera were contemporaries. The text is incorrect, therefore, in taking Acanthostega to be one of the "earliest tetrapods" under consideration. I am amending it accordingly. Peter Brown (talk) 14:47, 15 December 2012 (UTC)
Editing at 1:40 a.m. Oslo time! Do your kids really let you sleep late on Saturdays? Peter Brown (talk) 15:59, 15 December 2012 (UTC)
No, they don't. I never learn...
About "the earliest tetrapods", again we will need a section in this article dealing with definitions. If we follow Clack/Ahlberg, the earliest known side-branch is Elpistostege (normally considered a fish) and the second earliest is Elginerpeton (Clack & al. 2012). The feet is unknown in both though, making an assignment to tetrapoda a bit questionable. Then again, you have Laurin & Co who whose definition of tetrapoda excludes e.g. Seymouria and everything south of it. It really needs to be dealt with. Petter Bøckman (talk) 20:10, 15 December 2012 (UTC)

Tetrapod biodiversity trend[edit]

(I have moved the first two contributions here, with very minor adjustments to the first, from a user talk page.)

This edit, which I made today, has been reverted. As I imply in my edit summary, Sahney et al. (2010) does support the claim that, overall, the biodiversity of tetrapods has grown exponentially over time. They write that "The pattern of diversity increase for tetrapods appears to have been essentially exponential, with many setbacks and evident damping"; I don't read the part after the comma as negating any part of the clause before but merely as adding the information that there have been significant ups and downs within the overall exponential pattern of increase. I also don't see that the Laurin and Marjanović reference that I deleted provides significant support for the contention that lissamphibian diversity increased exponentially; rather, the paper assumes exponentiality and compares models embodying that assumption. My edit reflects these interpretations of these sources. Peter Brown (talk) 21:43, 14 January 2013 (UTC)

Hi Peter. Sahney may mention exponential diversification (although I did not find this by searching the string of characters in their paper), but their graphics certainly don't support this claim. The Marjanovic & Laurin (2008) paper that I had added studies this in detail in lissampibians. The other one, by Ward et al. (2005) provides a thorough study with lots of primaty data on the end-Permian event. In my opinion, these two papers provide a much more solid justification for these parts of the text than the Sahney paper, which is why I added them. I retained the citation of Sahney for the main focus of that paper, which is the link between tropical rainforest habitat and tetrapod diversification. I have reverted this edit. I hope that you will agree with this. Best wishes, Stranger forever (talk) 22:23, 14 January 2013 (UTC)
In the passage I quote above, which I have now underlined, Sahney et al. are quite explicit: tetrapods diversified exponentially. Whether the graph in the article approximates an exponential increase well enough to be called "exponential" can be challenged, but the authors do think that it is sufficiently close and a conflicting view would be OR unless a source can be found. The edit summary associated with the reversion complains that the authors do not show the exponential pattern clearly, but verifiablity is a matter of what a source says, not what it shows. Further, my objection to citing Laurin and Marjanović stands: since their argument assumes exponentiality, it cannot support the claim that the increase among the lissamphibians was, in fact, exponential. Laurin and Marjanović do not make the claim for lissamphibians; Sahney et al. do make it for tetrapods. Peter Brown (talk) 00:21, 15 January 2013 (UTC)
Hi Peter. marjanovic & Laurin do not assume that lissamphibians diversified exponentially; they tested it by looking at how much of the temporal variance of lissamphibian-yielding localities is explained by an exponential diversification model. It turns out to be 86%, which is a lot. Their lissamphibian data fits an exponential model much better than the data of Sahney et al. (2010). Be careful, the paleontological literature contains exaggerated (sometimes even contradictory) claims about the significance of findings. I selected these two additional papers not because of the author's claims, but because of the amount of data, the adequacy of the analyses, and the extent to which both supported a given point. Stranger forever (talk) 06:33, 15 January 2013 (UTC)
Hi again. Sorry, I forgot to mention, in my last posting (immediately above) that a problem with the analysis in Sahney et al. (2010) is that it is done at the family level. Even though they excluded signletons in some (perhaps most or all) analyses, this creates problems because the size of families is very uneven; their contents ranges from one to over a thousand species (in general; Rana itself, in some nomenclatures, includes over a thousand species). Thus, when we want to discuss diversification, which is changes in numbers of evolutionary lineages, most evolutionary biologists would argue that such analyses should be done at the species level (but even there, some problems arise). I can also provide references for this, if need be, but this is getting far from the main topic. Also, note that Sahney et al. (2010) tested (statistically) only the correlation between number of ecomorphs and number of families. They did not, contrary to Marjanovic & Laurin (2008), test the exponential diversification model (I checked even in the Supplementary on-line materials), which they seem to support more from theoretical expectations than from their results (which do not match closely an exponential curve; it shows many phases of reduced diversity, and some increases could fit other models, such as linear expansion). So I really think that Sahney et al. (2010) cannot be cited as the sole source for this, and tetrapod diversification cannot be stated to be exponential without mentioning exceptions (crises); at least several biological crises have reduced its diversity, and one of the best-documented cases is in the paper by Ward et al. (2005) that I cited. Stranger forever (talk) 08:34, 16 January 2013 (UTC)
You say that Marjanović and Laurin determined that 86% of the temporal variance of lissamphibian-yielding localities is explained by an exponential diversification model. Are we both discussing this paper? I don't find the figure 86% anywhere. They do say that "most of our recovery potential functions explain at least 85% of the observed variance in the observed number of localities," but that's a rather different matter.
The Sahney et al. paper does have weaknesses. As you point out, counting families is not as good as counting species, but it's not worthless, either, and I'm not aware of a comparable paper that makes good this deficiency. Yes, there were intervals in which tetrapod diversity decreased and intervals in which linearity is a good fit, and these do detract from the degree to which diversity is an exponential function of time (with a positive exponent), but perhaps they do not detract that much. Does some other function of time, one with a modicum of rationale, provide a better fit for the whole course of tetrapod diversity from the Middle Devonian to the present? I am not aware of any that have been proposed.
Peter Brown (talk) 18:10, 16 January 2013 (UTC)
Hi Peter. Yes, we are talking about the same paper. The 86% figure appears as 0.856, for CI 5, row for R2, in Table 3. The recovery potential functions are indeed based on an exponential diversification model (just that for CI5, and augmented by the effect of crises for CI1-4). And I am not trying to discredit Sahney et al. (2010), I am just saying that for Lissamphibia, the Marjanovic & Laurin give much stronger evidence and more appropriate analyses. Note also that Sahney did not test for exponential diversification; they just suggest it in text. But really, the data are messy enough that without a proper statistical test, I would not make much of that. Stranger forever (talk) 17:25, 17 January 2013 (UTC)
So the problem is the term "exponentially"? I guess we all agree diversity has increased dramatically with time, both papers says as much. Could we solve this with substituting "exponentially" with "dramatically" or "profoundly" or "increasingly" or anything like that? The important thing is to get the main point across. Petter Bøckman (talk) 08:17, 18 January 2013 (UTC)
Petter, Stranger Forever and I are both are willing to assert exponentiality, Stranger Forever for Lissamphibia and I for Tetrapoda. Strangie is unhappy with including Sahney et al. because they don't perform a rigorous statistical test. I am now satisfied that the paper by Marjanović and Laurin does support exponentiality in lissamphibian diversity but am uncomfortable with including this minor point in the short Biodiversity section since the lissamphibians have never been a major component of the tetrapod population. I think that the present wording is a reasonable compromise. If you have a problem with exponentiality, though, the matter needs to be discussed further. Peter Brown (talk) 22:14, 18 January 2013 (UTC)
I agree that if you want to cite Sahney et al. (2010), you can mention increase in biodiversity, but you should not argue that it is exponential on that basis, so Petter is right about this. Another, not negligible problem that I mentioned above is using family counts as a proxy of biodiversity (very imprecise at best), but that does not mean the paper cannot be cited. I disagree a bit with Peter's perspective on the relevance of the lissamphibian data; sure, lissamphibians account for about 7000 extant species of tetrapods, so that is less than a third of the total. But extant Tetrapoda are composed of two sister-taxa: Lissamphibia and Amniota. There is strong evidence for exponential diversification in Lissamphibia, but not in Amniota. There is strong evidence of impact of biological crises in Amniota, but not on Lissamphibia. In my opinion, the differences in patterns, as currently documented, are such that biodiversity of evolution of the group should distinguish between what happened in both clades. That was part of the reason why I introduced the two citations (Marjanovic & Laurin 2008 and Ward et al. 2005). Stranger forever (talk) 06:47, 19 January 2013 (UTC)
Sahney, Benton & Ferry 2010 say that tetrapod diversity increased exponentially. The claim appears in Biology Letters, a peer-reviewed journal that ranks #15 in impact factor among biology journals. Surely, I don't need to trot out statistics on Benton. Are you saying that this is an unreliable source? If it is reliable, Wikipedia policy allows claims that it supports. Peter Brown (talk) 16:52, 19 January 2013 (UTC)
Peter, reliability has little relationship with impact factor of journals. The bottom line is simply that Sahney et al. 2010 did NO analyses to support their claim that diversification is exponential. So it would not matter even if it were published in Nature, Science, PNAS, or all three (and I don't think that these journals are more liable than others; on the contrary, I have seen lots of erroneous or unjustified statements in these journals too)! That is simply an unjustified, ad hoc statement, and as such, it does not matter who stated it, and where it was published. This is my last message on this topic, which I think we have exhausted (and me too!). I may have to retire from Wikipedia; this is not for me... Stranger forever (talk) 17:28, 19 January 2013 (UTC)

WHOA!! Let me not be one who has chased an expert out of Wikipedia! Your contributions, e.g. to the Lissamphibia and Paleontology articles as well as to talk pages, have been most valuable. Wikipedia's standards for reliability may differ from those you prefer, but surely there is enough overlap in actual application to make the effort worthwhile? Peter Brown (talk) 18:06, 19 January 2013 (UTC)

Sarcopterygian phylogeny[edit]

According to Tetrapod#External and internal nares, "molecular studies have indicated that lungfish are the closest living relatives of tetrapods." The statement is supported by a reference to a 2011 study that notes that the only living sarcopterygians are the tetrapods, the lungfish and the coelacanths and concludes from molecular evidence that lungfish are closer to tetrapods than to coelacanths; if we allow the missing premise that the sarcopterygians are a clade, this does imply the statement in the Wikipedia article.

However, the debate over the relative positions of these three groups has been going on for over twenty years. Is it perhaps irresponsible for the Wikipedia article to endorse what just happens to be the latest word on the subject — if, indeed, it is latest? This 2010 paper in Systematic Biology includes a cladogram showing lungfish more closely related to coelacanths than to tetrapods. 2010 is still pretty recent. Should the article be more neutral on the matter pending a clearer consensus among the scientists? Peter Brown (talk) 15:39, 4 February 2013 (UTC)

I don't think it would hurt. We should report the debate, and report that the general view today is that lungfish and tetrapods are each other living sister groups. I'm not sure how introduce it without sacrificing readability. Suggestions? Petter Bøckman (talk) 14:57, 12 February 2013 (UTC)
I consider myself pretty good at presenting things clearly. Is there a source I can cite, though, to the effect that Tetrapodomorpha-Dipnomorpha sisterhood is "the general view today"? Citing works that hold that view is easy but invite a [non-primary source needed] tag. By the way, welcome back. Peter Brown (talk) 18:33, 12 February 2013 (UTC)
Thanks. Needed a bit of hiatus. The cited article Rise of the Earliest Tetrapods: An Early Devonian Origin from Marine Environment cites 5 articles giving the same result as theirs. Perhaps we can get around this by saying something like "While the dispute over the phylogeny remains disputed (ref), a number of molecular studies favour lungfish as the closest living relatives of tetrapods (ref)." Would that do? Petter Bøckman (talk) 22:10, 12 February 2013 (UTC) EDIT: Hah, found an useable source: Fins into Limbs: Evolution, Development, and Transformation, edited by Brian K. Hall. Page 16 reads: "Most computer assisted analysis favour a lungfish-tetrapod grouping (Cloutier and Ahlberg 1996; Forey 1998; Zhu & al. 2001), although the coelacanth-tetrapod arrangement (Zhu and Schultze 2001) remains actively debated." I'd say that's fairly much what we need here. Petter Bøckman (talk) 22:25, 12 February 2013 (UTC)
I guess I'm confused. Tetrapods have internal nares. So do lungfish. Coelacanths, in contrast, don't belong to the internal-nares club. This would seem to provide reason to think that lungfish are more closely related to tetrapods than coelacanths are. Yet, somehow, consideration of nares led people to the opposite position, that coelacanths are more closely related. How did they come to that conclusion? Evidence seems to point the other way. Peter Brown (talk) 01:32, 13 February 2013 (UTC)
It's what I thought back in my student days too. The idea is that the internal nares in lungfish are so different from ours that they represent an independent development. There is some merit to the idea. Lungfish and (presumably) early tetrapods lived in shallows. The nares where thought of as similar solution to a similar problem. I have tried to explain it in the article, perhaps not very well though. It is a phenomenon we see time and again in evolution, just think of all vertebrate groups using the forelimbs as wings! Also notice the internal nares are not used to breath with, in elpistostegalians and many labyrinthodonts the spiracle served that function. They seem to have evolved as an adaption to smelling in extreme shallows with half the head above the waterline. Petter Bøckman (talk) 06:43, 13 February 2013 (UTC)

So lungfishes' internal nares are so different from tetrapods' that they have long been seen as non-homologous. The natural conclusion, surely, is that tetrapod and lungfish internal nares evolved independently from a coelacanth-like fish. From an ancestral coelacanthimorph descended:

  • Coelacanths, still with no internal nares,
  • Tetrapods, with nice internal nares, and
  • Lungfish, with funny internal nares.

I fail to see why this conclusion suggests anything about the affinities of these three groups. The phylogeny





seems as compatible with these observations as either of the other two possibilities. Why was it rejected, early on? Peter Brown (talk) 16:23, 13 February 2013 (UTC)

Well, if we are to believe Kenichthys with the nares on the lipline is on our side of the tetrapod/lungfish divide (which is the general consensus), then internal nares have actually evolved independently in the two lines. When you include the fin/leg bones in the analysis, the older stance give more meaning. Lungfish "flshy stalks" skeloton looks nothing like the humerus-uluna/radius arrangement found in the first proper legs. The Latimeria on the other hand has just the sort of arrangement found in e.g Eusthenopteron. So you need to ad "limb skeleton nice" and "limb skeleton weird" to your characters list. Petter Bøckman (talk) 20:41, 13 February 2013 (UTC)

Choana? Choanae?[edit]

The article uses "choana" only in the singular. "Gogonasus and Panderichthys. . . had a choana" (emphasis added), suggesting that each animal had only one. Choana, however, redirects to the article Posterior nasal apertures, which starts out by saying "The choanae are separated by the vomer," which indicates that each animal has one vomer and two choanae. It also says that "the lungfish has internal nostrils too"; it doesn't say that they're choanae but also doesn't say that they aren't. Does a lungfish have a choana? If not, why don't its internal nostrils count? Does it have two of them? Do tetrapods have two? Peter Brown (talk) 18:33, 14 February 2013 (UTC)

You are (again) right, it should be choanae in the plural, as it is always two (at least in the critters under discussion here). This easily digested article neatly sums it up: Petter Bøckman (talk) 21:03, 14 February 2013 (UTC)
The cited article seems to say that the internal nostrils of lungfish evolved independently of tetrapod choanae but then, in the very last sentence of the article, it says "internal nostrils of lungfishes and tetrapod choanae are homologous". Aren't homology and independent evolution contradictory? Peter Brown (talk) 23:41, 14 February 2013 (UTC)

Evolution of tetrapod nares[edit]

The anatomy and phylogeny of lungfish are not relevant to the evolution of the tetrapod choanae; lungfish should be mentioned in this connection only to note that they are irrelevant despite the fact that they do have internal nares. I am accordingly removing the lungfish image from the External and internal nares subsubsection along with all mention of the lungfish's place in the phylogeny. The fact that tetrapods are more closely related to lungfish than to coelacanths does need to be mentioned somewhere in the Tetrapod article, but this subsubsection is not the place. Peter Brown (talk) 01:11, 19 February 2013 (UTC)

I should add that it was Petter Bøckman who, in the exchanges above, clarified matters so that I could modify the External and internal nares subsubsection as I did. It was he who wrote the subsubsection in the first place, and he is the source of any improvement resulting from my edits. Peter Brown (talk) 19:51, 19 February 2013 (UTC)

Eryops did not hear airborne sounds – needed another 140 MY[edit]

Large error in the article about hearing. It states: "Also, by utilizing vestigial fish jaw bones, a rudimentary ear was developed, allowing Eryops to hear airborne sound.". This is about 140 million years too early. Airborne sounds do not become detectable until well after the mammals split off and developed independently in the different lines. Reference to: Geoffrey A. Manley, An evolutionary perspective on middle ears, Hearing Research, Volume 263, Issues 1–2, May 2010, Pages 3-8, ISSN 0378-5955, 10.1016/j.heares.2009.09.004.

( Mark RiggleMark Riggle (talk) 19:46, 24 April 2013 (UTC)

Indeed, there's a lot of dated stuff in the older parts of this article. Petter Bøckman (talk) 20:21, 24 April 2013 (UTC)

Evolution of Tetrapods[edit]

That section is so huge, I decided to spin it off into its own article. The spin off article can be expanded, while the version in this article can be trimmed.

The article right now focuses too much on the evolution of tetrapods. It also needs to focus on modern tetrapods and other things. --Harizotoh9 (talk) 00:58, 10 March 2014 (UTC)

Nicely done, I support this for balance. Although it looks like the original text is still in this article. Can you summarize/abstract it to a paragraph after the Main article redirect? --Animalparty-- (talk) 09:29, 19 March 2014 (UTC)
I've had a go at summarising, but the result so far is still much more than a paragraph or two. I'm pretty happy with the summary origins section, although it could be made more compact like this. I'm less happy with the sections on geological periods. They seem too wordy but I'm not sure what to take out. The transition to land is important. Amniotes are important. The extinction events need some kind of mention to help explain why there was subsequent radiation. Covering a few extinct groups is useful for balance. Using dates rather than geological periods (and just presenting a timeline) might be briefer. Would that be OK? Or does this need to be chopped right back to a simplistic "Early tetrapods evolved into amphibians, reptiles, birds and mammals."?
Any problems with references should be preexisting - I haven't deliberately added new assertions and I think I preserved existing references. That said, if the summary settles down I should be able to thoroughly reference at least the origins section using ISBN 0-321-78235-6.
... and finally. I changed Eryops to Edops for not very good reasons. Feel free to change it back. TuxLibNit (talk) 23:03, 29 May 2014 (UTC)
On second thought, I'm not sure this split really works. Much of the remainder of the tetrapod article is about early tetrapods so needs the evolution section to put it in context. Is the summary enough?TuxLibNit (talk) 23:29, 29 May 2014 (UTC)
Tetrapods as a topic is concerned primarily with their evolution in the Devonian and Carboniferous, especially the evolution of their skeletal systems. The fact that Tetrapoda subsumes a great number of living forms is in itself not enough to make it notable. After all, Theria (mammals that give birth to live young) is not particularly notable, even though it includes all placental mammals and marsupials. The reason it's not notable is because it is usually not necessary. Combining two of the three major subclades of mammalia just creates useless clutter, except for paleontologists and evolutionary biologists. Many high-level taxons have this problem.
Tetrapods are notable for being the only lineage of vertebrates to have ever become terrestrial. This is notable because we humans are terrestrial vertebrates, because we consider our status as vertebrates and terrestrial animals notable, and because the organisms we consider most notable are other terrestrial vertebrates. On the other hand, we have ornithologists who study birds, herpetologists who study reptiles and amphibians, etc., so that most of the lower-level subclades of tetrapoda are already in some other department.
That's why tetrapod studies focuses mainly on things like the earliest amniotes and lissamphibians, or if they are not known, the earliest representatives of their major subclades (saurapsid, synapsid, anura, urodele, etc.) That plus basal tetrapods such as Acanthostega or Balenerpeton, with plenty about tetrapodomorph fishes, especially of the more derived variety.
Since most of the evidence comes from paleontology, and since bones are usually the only parts to fossilize, this topic will be mainly about the evolution of the skeletal system.
If you want to talk about living tetrapods, there are plenty of other articles that already do so. Zyxwv99 (talk) 22:49, 11 July 2015 (UTC)

Rhipidistia vs Sarcopterygii vs Osteichthyes[edit]

@Jmv2009: I've reverted these edits for the following reasons:

  • It is not clear how referencing Rhipidistia in either place is an improvement. I think it makes the article less accessible and according to my Vertebrate Life (ISBN 0-321-78235-6, p191) and some others, Rhipidista has fallen into disuse (actually it says "rhipidistians" but thats close enough for me). On this second point, try finding a secondary or tertiary reference for the clade definition being in wide use (it needs more than a primary source that proposes this definition).
  • Specifically on the change in the lead, this sentence is referenced to Clack2012, so unless that reference uses "Rhipidistia" you need to provide a new reference.
  • Specifically on the change in the "Fish ancestors" section, your change has a wider impact on the "Origins" section. The reference to Osteichthyes in Lobe fins worked as a reference back to the Osteichthyes in the "Fish ancestors" section. With Rhipidistia in "Fish ancestors", we're now jumping around rather less coherently. Ultimately it comes down to a choice about where to start the narrative. IMO we should not start with a group (Rhipidistia) that (AFAIK) is significant primarily as an ancestor to Tetrapods. That amounts to saying "tetrapods evolved from the ancestors of tetrapods", which is not very helpful.

TuxLibNit (talk) 23:09, 31 May 2014 (UTC)

I didn't know the 'Rhipidistia hypothesis' was controversial, and the Rhipidistia article doesn't mention it. Please correct the Rhipidistia AND lungfish article with your wiseness. I thought Rhipidistia would be a good middle point, because Rhipidistia clearly are fishes, and they contain current lung fishes. What is the smallest group containing lungfishes and Tetrapods?Jmv2009 (talk) 07:32, 1 June 2014 (UTC)

I'm not claiming wiseness, just asking questions. I don't understand what you mean by 'Rhipidistia hypothesis'. I'm not trying to dispute that tetrapods are derived from rhipidistia under either the original paraphyletic taxonomic definition or a new cladistic definition. First and foremost I'm questioning whether the term is useful as the starting point for a discussion of tetrapod evolution. This may depend on how rhipidistia is currently defined (which the current wikipedia article is unclear on). If rhipidistia includes the ancestors of tetrapods by definition then I think we need to start the article at an earlier point and say where rhipidistia come from.
To answer your specific points:
  • In my Vertebrate Life, the smallest group containing lungfish and tetrapods is unnamed. It consists of Tetrapodamorpha and an unnamed group that consists of Dipnoi (lungfishes) and Porolepiformes. The smallest named group is Sarcopterygii (which adds coelacanths).
  • Rhipidistia is in use on about 19 pages. I'm in no hurry to start changing them all. Bear in mind that based on the refs I have I'd be describing Rhipidistia as disused and reviewing current uses on wikipedia for removal. I might edit just rhipidistia to see what happens.
  • I'm still at least half-expecting someone to come up with references to back up a cladistic redefinition of rhipidistia (I've tried to find such, but without success so far). Since you've been making edits in this area I was hoping you'd be in a position to help.
I hope that is clear. TuxLibNit (talk) 20:34, 1 June 2014 (UTC)


Someone recently added material relating to an alleged new taxon called Paramphibia. The only evidence for this is material published by the inventor of the concept. Google Scholar has nothing on "paramphibia" or "paramphibians." I think it fails the notably test even for a mention. It is currently described in the voice of the Wikipedia as if it were an established fact. Zyxwv99 (talk) 00:55, 22 February 2015 (UTC)

On the one hand, these things take time to make a presence on google, but on the other hand, yes, we should wait until the paper describing it comes out first before inserting it into the article.--Mr Fink (talk) 01:57, 22 February 2015 (UTC)

Do list for Origins section[edit]

I've been chipping away at this section, but still have changes I want to make. Just thought I'd mention them here. First, I'd like to add two subsections, one on the evolution of terrestriality, the other on the first crown tetrapods. I want to keep both subsections short. The Ancestry subsection is what was here before I got here. Since it is already discussing limbs, lungs, and water environments in terms of salinity, I'd like to separate that out into three different paragraphs. I think the stuff about freshwater environments is incorrect or obsolete. Clack says that most early lobe-finned fish could probably tolerate both salty and fresh water, although sometimes it's hard to tell. There's new information on elpistostegalians indicating that they were not as fresh-water as people thought. It also seems like a red herring, sine salinity didn't seem to be an issue for them. And finally, early tetrapods were still capable of swimming across the sea to another continent, although these would not have necessarily been long ocean voyages since continents were close together. The part of limbs just needs some minor corrections. Some but not all lineages of tetrapodomorphs had bone-for-bone homology in the first two mesomeres, while all early lobe-finned fishes had bone-for-bone homology for the first mesomere. Laurin in "How vertebrates left the water" has a good overview of the subject that we should try to work in the Anatomy section. Next, the lung problem. With each passing year things keep leaning more strongly towards "lungs came first." I think giving equal time to swim bladders is undue weight. However, it's not a done deal yet, so we need to be careful how we word it. Then there's the book from 1969 (Cobert, Vertebrate something) that's hard to find, and we are using to reference a topic that has evolved at lot since 1969. Anyway, those are some of the issues I'm struggling with. Zyxwv99 (talk) 22:59, 31 May 2015 (UTC)

Do list for section Anatomical features of early tetrapods[edit]

This (largely unreferenced) section was moved from the Amphibian article. The introduction is full of cruft that repeats information found elsewhere in this article. Much of the remaining content is specific to amphibians. I'm reluctant to take out anything without having something better to replace it with, but it looks as if this needs a total rewrite. I'll try to tackle it one section at a time, maybe starting with the skeletal system. First the skull, then axial (spine), then appendicular (limbs) Zyxwv99 (talk) 00:51, 11 June 2015 (UTC)

Skip template for taxobox[edit]

Linking the parent to teleosts seems odd and uninformative of the actual parent clades. Why not use a skip template to link it to a dummy version of Tetrapodomorpha, as here? [1] This will allow the taxobox to display the correct parent without forcing all the fish supertaxa into tetrapod taxoboxes. I'd do this myself but the template is locked for admins only. Dinoguy2 (talk) 14:15, 5 July 2015 (UTC)

I was wondering about that myself. It's actually "teleostomi" which is something else altogether. Teleosts are the most common kind of ray-finned fish today, while teleostomi are the common ancestor of bony fish and "spiny sharks." That's actually worse, since even fewer people have heard of teleostomi. If you think you can improve the taxobox, please do. I was afraid to tamper with it because I have no experience with taxoboxes. Zyxwv99 (talk) 20:21, 5 July 2015 (UTC)
I would simply make a skip taxon to Elpistostegalia, the immediate parent group of Tetrapoda (the skip template will not break any ranks in the fish boxes). But I can't because for some reason the taxobox here is locked for admin only. Dinoguy2 (talk) 16:07, 26 July 2015 (UTC)


There are no living fish tetrapods. The illustration Amphiprioninae in the fish order Perciformes; they arent tetrapods. Some early fish species being tetrapods is not the same thing at all. The text didnt confirm this opening assertion and it wasnt ref'd. I suspect a subtle vandalism but perhaps a genuine mistake? ♫ SqueakBox talk contribs 02:51, 12 August 2015 (UTC)

Probably a mistake. The closest thing we have to extant fish tetrapods would probably be the lungfish, but...--Mr Fink (talk) 03:52, 12 August 2015 (UTC)


The taxobox for this article has been extensively debated (see above) and some consensus was reached.

The new additions by Mrjulesd give a specific taxonomic position to Temnospondyli and Lepospondyli; but these groups have different positions in the various phylogenetic hypotheses illustrated by cladograms in the article, so it is at best somewhat misleading and at worst partisan to include them in the taxobox, and yes, I know classification and phylogeny aren't exactly the same thing. I think, in short, that the taxobox was better before. Would be curious to know what other editors think. Chiswick Chap (talk) 13:31, 13 January 2017 (UTC)

Chiswick Chap well I've removed the groups as you've suggested. I think the important point is that the Batrachomorpha gave rise to the Amphibians, as that is more familiar to most. --Jules (Mrjulesd) 13:41, 13 January 2017 (UTC)
Many thanks. Chiswick Chap (talk) 14:01, 13 January 2017 (UTC)