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WikiProject Amphibians and Reptiles (Rated C-class, Top-importance)
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The urinary bladder and allantois[edit]

"The bladder of amphibians is thought to be homologous with the allantois (a fetal excretory organ) of amniotes. The bladder of turtles, Sphenodon and some lizards is formed by retention of part of the fetal allantois. Bladders are absent in crocodilians, snakes, some lizards, and most birds, because the urine of these is semisolid, consisting mostly of uric acid. In mammals the bladder is formed from part of the allantois and from the urodeum (a subdivision of the cloaca). The bladder empties into the cloaca in tetrapods except for therian mammals, in which it has a separate external opening called the urethra."

"The bladder and the urethra develop from the urogenital sinus. The bladdder also develops in part from the allantois. The hindgut and the allantois empty into the cloaca early in development. The cloaca ends as the cloacal plate, a region of ectoderm and endoderm without intervening mesoderm. The urorectal septum develops in that region of the cloaca where the allantois and the hindgut meet. This septum grows toward the cloacal plate and divides it into an anal canal and a urogenital sinus. The cloacal plate then gets divided into an anal membrane and a urogenital membrane with a perineal body in between. The mesonephric duct empties into the urogenital sinus. The urogenital sinus and the allantois enlarge to form the urinary bladder."

As far as I can see, the allantois does contribute to the formation of the urinary bladder in amniotes.


Is there a published reference for referring Aminota to the rank of Microphylum? If so, it should be listed and discussed in the text, especially as I've seen this being migrated to taxoboxes on other pages.Dinoguy2 22:01, 17 August 2006 (UTC)

Amniota is the name of a clade. I don't see how it can be forced to fit into taxoboxes, which are based on a more traditional classification scheme. Other than this item in a forum of some kind, the only references I can find for 'microphylum' in the sense used in the taxoboxes are on Wikipedia or derived from Wikipedia. It looks like a neologism to me, complicated by the fact that 'microphylum' and 'microphyllum' are used as species names. -- Donald Albury(Talk) 21:58, 18 August 2006 (UTC)
To be fair, Amniota was coined before the advent of phylogenetic taxonomy, so it is not only a clade. I'm not sure what it's traditional rank would be, though Benton (2004) lists it as "Series". I prefer leaving it unranked, as Benton tends to use a lot of superfluous ranks.Dinoguy2 23:53, 18 August 2006 (UTC)
And in any case, calling 'Amniota' a 'microphylum' looks like a real problem. I cannot find any instance of 'microphylum' and 'Amniota' on the same web page in a Google search that is not in WP or copied from WP. I'm going to bring this up over at Wikipedia talk:WikiProject Tree of Life. -- Donald Albury(Talk) 11:11, 19 August 2006 (UTC)
Note--the forum you linked, Dalbury, is the Dinosaur mailing List. While an amazing resource, there is a lot of original research that goes on (good thing for paleontologists, bad thing for an encyclopedia). The use of microphylum there is, within the context of the post, definately original research. I've seen similar examples of the author's shoehorning cladistic research into Linnean ranks on the internet before, and I suspect this is how the use of microphylum, etc., came about.Dinoguy2 03:09, 20 August 2006 (UTC)
I removed the reference to microphylum from the article. If there is a classification out there that applies that rank to amniotes, "microphylum" could be mentioned in the context of that classification, but it's confusing to have such an obscure rank in the article's first sentence.

Problem with Taxonomy section[edit]

The Taxonomy section shows the Class Synasida containing the Order Therapsida, which in turn contains the Class Mammalia. You really can't mix traditional classification and cladistics this way.This needs to organized like Synapsid is. -- Donald Albury 22:55, 5 February 2007 (UTC)

Fixed it. Dinoguy2 23:01, 5 February 2007 (UTC)

No phylogram of amniotes?![edit]

Erm, we need one. Badly. Samsara (talk  contribs) 14:45, 3 June 2007 (UTC)

Do-dom: Samsara (talk  contribs) 14:49, 3 June 2007 (UTC)

Are amniotes a polyphyletic group?[edit]

Based on this and related articles, it seems that synapsids and sauropsids are two different lineages of amniotes which have evolved separately and are not directly related to one another. This means that "amniota" is a polyphyletic group, and therefore it is not a valid clade by the standards of modern cladistics. Is this correct? —Preceding unsigned comment added by (talk) 15:26, 29 March 2008 (UTC)

The problem here is that the use of cladistic taxonomy makes it very hard to classify basal organisms, like Casineria, in a meaningful way. While the split between synapsids and sauropsids is a deep one, it does not run all the way to the bottom, and there's always the question of turtles, which may represent an even earlier split. This is the kind of situation that cladistic taxonomy is not well suited to deal with. Petter Bøckman (talk) 09:46, 14 April 2009 (UTC)
Cladistic taxonomy, which is almost universally accepted by people working on early amniotes, does not create a problem. Basal organisms are difficult to place into one or the other lineage coming off a node simply because they are basal. This is not a problem to be solved by the erection of artificial categories, but reality. —Preceding unsigned comment added by Struvite (talkcontribs) 16:13, 9 March 2010 (UTC)
The Amniota (proper name) would be polyphyletic only if derived from different amphibians. Polyphyly has to do with their ancestry, not the lineages contained within. Of course the same question can be asked of the Sauropsida and of the Synapsida. Best ignore most of the cladobabble. J.H.McDonnell (talk) 00:05, 15 September 2010 (UTC)

Problems with links[edit]

The Out of the swamps external link does not work, when I tried to get on it it said "HTTP 404 not found" —Preceding unsigned comment added by Phthinosuchusisanancestor (talkcontribs) 21:40, 14 November 2008 (UTC)

It works now.Petter Bøckman (talk) 09:48, 14 April 2009 (UTC)


I am a mammal, and I have two legs (last I checked). (talk) 19:59, 10 September 2009 (UTC)

You noticed those two elongated things that grow from your shoulders? They also count as "poda". (talk) 02:18, 28 January 2012 (UTC)
Response to "Tetrapodal?"
You may be a mammal with two legs, however, you evolved from mammals with four legs. Your arms are an evolutionary response to bipedalism. The same goes for birds (which are actually reptiles).Ronald Van Heest (talk) 14:01, 5 September 2010 (UTC)
so... snakes and birds and people are all tetrapods based on geneaology? Is there a classification for animals that currently have four legs and lay eggs? — Preceding unsigned comment added by (talk) 19:06, 18 May 2012 (UTC)
Tetrapoda is a clade, so every descendent of the first tetrapods are by definition tetrapods whether they have 4 legs or 2 or 0. Quadruped refers to animals which locomote on 4 legs and wouldn't include whales and snakes and humans. --holizz (talk) 12:11, 6 April 2014 (UTC)
Re: Response to "Tetrapodal?"
Whales are considered amniotes, and whales are not tetrapodal. This invalidates the claim that all amniotes are tetrapodal. — Preceding unsigned comment added by (talk) 22:08, 15 August 2013 (UTC)

Phylogenetic classification[edit]

The ranked taxonomy of amniotes taken from Benton is not really phylogenetic. At best it is a hybrid of the "traditional" system and a phylogenetic classificiation. I don not believe that it is very widely used. The (or a) real phylogenetic classification is the one given in the cladogram: in phylogenetics a cladogram and a classification are one in the same. As written the article also gives the impression that the "traditional" system still is in widespread use. It is not, although it persists in some textbooks.Struvite (talk) 16:26, 9 March 2010 (UTC)

You'll find Bentons hybrid system all over Wikipedia. If you wish to argue against it's use (I'm personally not too fond of it either), Wikipedia:WikiProject Amphibians and Reptiles#Paleontological references is the place to speak your mind on this matter. As for the old system, it is very common once you get outside of specialist literature. As such is merit mention. Petter Bøckman (talk) 18:51, 9 March 2010 (UTC)
I don't object to it being mentioned, just to the implication that it is accepted among people working in the field. In the same way a history of chemistry would be incomplete without discussion of the four ancient elements, but would be inaccurate if it suggested that modern chemists still spoke in terms of 'earth' and 'fire.' The same with Benton's system. I'm not saying take it down, I just object to calling it phylogenetic. It is not. As for specialist literature, that's pretty much all there is when it comes to 'amniotes.' It's not a traditional group, like 'birds' and 'fish,' but a category that never has been widely used outside of specialist literature and textbooks. The problem is so few people actively work on amniotes as amniotes that textbook accounts rarely change to accommodate new discoveries and interpretations. Struvite (talk) 22:06, 9 March 2010 (UTC)

Amniote egg and terrestrial reproduction[edit]

The amniote egg traditionally has been considered a major evolutionary advance that permitted vertebrates to reproduce on dry land, freeing them of the need to return to standing water. I intend to revise this article (with references) to reflect recent challenges to this view, and in particular to point out that 1. we have no direct evidence, and essentially no indirect evidence, of how the first amniotes or their ancestors reproduced. There is no reason to assume that the reproductive mode of modern amphibians is primitive or that the amniote egg evolved from anything resembling a frog egg. Some of the features of amniote eggs that have been interpreted as adaptations to terrestrial reproduction may in fact be primitive. 2. Amniote eggs provide no more protection from dehydration than amphbian eggs, even modern amphibian eggs. Eggs buried in underground nests need no such protection as the water potential of soil in such nests is higher than the physiological water potential of vertebrate eggs. 3. buildup of nitrogenous waste in terrestrial eggs is not the serious problem it often is assumed to be. 4. Terrestrial eggs need no special adaptations for gas exchange.

It may be best to create a separate section dealing with the amniote egg.

I'm new here and wanted to give a heads up before I make a lot of changes Struvite (talk) 17:06, 9 March 2010 (UTC)

As long as you can back up your statements with credible sources, I can't see any problems. It might be a good idea to make a separate article on the amniote egg as you suggested, the two can be merged later if we want to. Petter Bøckman (talk) 18:56, 9 March 2010 (UTC)
Thanks for the suggestion. that probably is what I will do.Struvite (talk) 22:07, 9 March 2010 (UTC)

Stem amniote?[edit]

In the lede, the first amniotes are described as The first amniotes (referred to as "basal amniotes" or "stem amniotes"). This is misleading, as it indicates the stem group amniotes are limited to to the proper egg-laying animals. While "basal amniotes" is not a very precise term, stem amniota denotes a very wide assemblage, including most of (if not all) of the groups traditionally assigned to Reptiliomorpha, including Seymouria, Eogyrinus and Archeria, not to mention quite a few fossil tadpoles. The labyrinthodont tree is not well understood, and the actual content of "stem amniota" is a matter of some dispute, and may even contain some groups traditionally assigned to Temnospondyli. As such, the term "stem amniotes" is useless, and I have removed it from the lede. Petter Bøckman (talk) 07:09, 4 May 2011 (UTC)

Sauropsida, a junior synonym of Reptilia[edit]

With the Mesosauridae evolving within the Parareptilia (= Anapsida). Sauropsida should be considered a junior synonym of Reptilia.

Tsuji, L. A., and J. Müller. 2009. Assembling the history of the Parareptilia: phylogeny, diversification, and a new definition of the clade. Fossil Record, 12(1): 71-81.

Modesto, S. P. 2006. The cranial skeleton of the Early Permian aquatic reptile Mesosaurus tenuidens: implications for relationships and palaeobiology. Zoological Journal of the Linnean Society, 146: 345-368. Ronald Van Heest (talk) 14:07, 5 September 2010 (UTC)

No, Sauropsida can't be synonymised with Reptilia. Reptilia is defines by traits, Sauropsida by phylogeny. Appart from the fundamental difference in approach, the content is stil different. While Casineria is a reptile, it is not a s Sauropsid, and the mammal-like reptiles are are excluded from Sauropsida, while birds are included (unlike in Reptilia). The two are fundamentally different systematic units.--Petter Bøckman (talk) 08:19, 6 September 2010 (UTC)


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