Talk:Synapsid

Article merged: See old talk-page here

I previously added the mammalia class, which was ommited I think in this section

"Fused arch" ??

What "fused arch", synapsid refers to the number and placement of temporal openings in the skull; one, low on either side as opposed to two in the reptilian diapsida. Another word for apsis is fenestra. In much the same sense, a syncline is a down warp in folded strata.

I known, the standard place for the latest entry is at the bottom where it will get the least attention. If putting it at the top torques anyone to much, go ahead the synplace it. J.H.McDonnell (talk) 23:21, 12 September 2010 (UTC)

Missing items in taxobox

The subgroups of pelycosaurs and caseasaurs are covered in the text. Ought these not to be included in the taxobox as well? (I would add them myself, but I know little of the science of taxonomy and might easily do something stupid, so I would prefer to leave it to someone who knows what they are doing.) SpectrumDT 19:41, 22 October 2005 (UTC)

This page says there are 4500 species of mammals but the page on mammals says there are 5500. Which is right? Smeapancol 19:14, 7 January 2006 (UTC)

"believed to have been caused by poisonous volcanic gas"

Surely there are a whole range of theories on the causes of the Permian-Triassic event —This unsigned comment was added by 82.23.1.206 (talk • contribs) 23:45, 1 April 2006.

You're right. I've edited the article to reflect the ambiguity. bcasterline t 00:47, 2 April 2006 (UTC)

Clasification + Phylogeny

I've switched the classification scheme we had into two parts- classification and taxonomy. This seems to work a bit better aesthetically, as it removes unranked taxa from the ranked list, and presents an unambiguous cladogram to better reflect evolutionary relationships. I welcome discussion on this, and will accept if it's met with universal hatred and gets reverted :) Dinoguy2 20:02, 25 May 2006 (UTC)

I love it... ;-) Fedor 12:52, 6 September 2006 (UTC)

"Mammal-like reptiles" ??? Synapsids include mammals. Someone plese look into this. —Preceding unsigned comment added by 202.78.232.177 (talk • contribs) 22:16, 9 January 2007 202.78.232.177

The key here is 'traditionally'. Traditionally Synapsids did not include mammals, but were treated as a subclass of Reptilia. Hopefully, use of the word 'traditionally' implies that this is an outdated term. Dinoguy2 19:48, 10 January 2007 (UTC)

I think i should combine mammals with synapsids. Because they're in the same class right? We should do the same thing with birds put into reptiles. User:4444hhhh

I don't think they've ever been put in the same class. Synapsids, in phylogenetic taxonomy, include mammals, but this system does not use any kind of ranks. Traditionally, Synapsids have been ranked as a Subclass of Class Reptilia. More recently, Benton ranked them as a Class seperate from reptiles and paraphyletic with respect to mammals (that is, it doesn't include mammals, because they were kept in a seperate class. As far as I know, creating a class that includes all synapsids would be original research. Same for reptiles and birds, though a new class is sometimes used for dinosaurs and birds, usually either Dinosauria or Archosauria. But the dinosaur wikiproject has decided to use Benton's scheme for them as well, and he uses Class Sauropsida for reptiles and class Aves for birds. Dinoguy2 03:02, 21 March 2007 (UTC)

Isn't traditionally Synapsida one of three subclasses of Reptilia? Petter Bøckman (talk) 13:43, 2 June 2009 (UTC)

One of four traditional subclasses, yes. Romer's scheme divided reptiles into Anapsida, Diapsida, Synapsida, and Euryapsida (which turned out to be polyphyletic). Dinoguy2 (talk) 16:52, 2 June 2009 (UTC)

I suppose Synapsida as a class is from Benton? Petter Bøckman (talk) 19:55, 2 June 2009 (UTC)

He may have been the first to make Synapsida a class but I'm not sure. He's one of the few vert paleo workers that's even using ranks anymore, so it wouldn't surprise me. Dinoguy2 (talk) 23:01, 2 June 2009 (UTC)

Non-Mammal Synapsid

Are there any existant non-mammal synapsids? -- 20:22, 26 August 2007 (UTC)

I think it's safe to say that all non-mammal synapsids are extinct. See Evolution of mammals, which notes in the intro: “From the point of view of cladistics, mammals are the only surviving synapsids.” --Mathew5000 21:29, 26 August 2007 (UTC)

Shouldn't humans be listed as well here?

Since mammals evolved from therapsids and we humans are mammals, I believe we should be listed under the current living synapsids of today. Suffor 14:46, 1 September 2007 (UTC)

Note that synapsids as they are treated here are paraphyletc--that is, they expressly exclude the mammals. That's what the * means in the taxobox, for example. Dinoguy2 14:50, 1 September 2007 (UTC)

Actually, the article's intro expressly includes mammals as synapsids. --Mathew5000 17:11, 1 September 2007 (UTC)

Mammal-like reptiles

4444hhhh, I noticed you redirected Mammal-like reptiles to this page. While my pro-merger arguments on the other article's talk page have not been answered, I do believe this material should not be lost but properly merged in, for the reasons which I stated there. If you want to do it, be my guest, otherwise I will have a go at it myself. Gnostrat (talk) 03:36, 20 January 2008 (UTC)

Er... I'm dinoguy, not synapsidguy, but doesn't (didn't) the term 'mammal-like reptile' refer to therapsids specifically? I've never heard Dimetrodon or Edaphosaurus referred to that way. The term you're looking for is 'stem-mammal.' Dinoguy2 (talk) 03:19, 18 March 2008 (UTC)

Well mammal like reptile is an old term anyway, i suppose though that it reffered to all synapsids (including non therapsids like Dimetrodon) apart from true mammals (they are a different class) are mammal like repitiles.Lemming42 (talk) 20:04, 18 March 2008 (UTC)

I could be wrong, but I presume a stem-mammal is an actual mammal which diverged earlier than the last common ancestor shared by the crown-group (i.e. monotremes plus therians). If it's a fossil synapsid that didn't even fulfill the classic criterion for inclusion in Mammalia — the single dominant jaw joint between dentary and squamosal — it can't be called a stem-mammal. One suggestion (can't remember whose) was to call the non-mammalian members paramammals.

I know of a single site (Palaeos) that describes therapsids, but not pelycosaurs, as "mammal-like reptiles". It's an excellent resource in nearly every way, but I think it's mistaken in this overly restricted usage (and see here for a site that takes the opposite view from Palaeos). Mammal-like characters emerged by stages including, for example, the appearance of differentiated teeth in sphenacodontids like Dimetrodon. Classic works from at least the 1960s to the present (Romer, Carroll, Benton) all refer to pelycosaurs and therapsids together as the (so-called) "mammal-like reptiles". Gnostrat (talk) 21:35, 18 March 2008 (UTC)

Ok, if those authors used it that way that's good enough for me (though this should be cited, the use of mammal-like reptile is currently unsourced). Actually all the citations could use an overhaul, many are incomplete and mixed in with notes that could really be worked into the main text, to conform with the style and layout of similar articles. As for stem-mammal, I was using it in the PhyloCode sense--i.e., all members of a clade excluding the crown clade. So "stem mammal" would mean any synapsid that is not a member of monotremes+marsupials+placentals. Dinoguy2 (talk) 00:00, 19 March 2008 (UTC)

The PhyloCode is fatally flawed, and I now have cause to hate it even more! If you are right, under the PhyloCode a "stem-mammal" could mean either (1) a mammal that isn't in the crown-group, or, amazingly, (2) a synapsid that isn't even a mammal. Well, Carroll (1988) did suggest, half-seriously, that all synapsids might be incorporated into the Class Mammalia, but I never imagined that a new code would turn a jest into a requirement. I had considered removing "stem-mammal" from the lead section (it's unsourced too) but now I guess I will have to leave it in and request some confirmation.

Anyway, I'll be adding citations for "mammal-like reptiles" and fix up the notes (one of them is superfluous, in fact). There's just a couple of them that are citing an entire article, but they're short articles and I imagine that will suffice until somebody can put in some specific page references. Gnostrat (talk) 09:34, 19 March 2008 (UTC)

Sorted the citations, though there are still too few of them so if some experts could muck in, that'd be great. Come on guys, you had to use sources when you first wrote this stuff. By the way, Dinoguy, I bet you don't refer to dinosaurs as "stem-birds", do you? : ) Gnostrat (talk) 21:53, 22 March 2008 (UTC)

Changing classifications

I've removed the following paragraph from the above-named section and I'm putting it here for further discussion. Perhaps it could be reinserted after it's been shortened and amended:

Most taxonomists who apply the caladistic approach consider tetrapods to fall within the Sarcopterygian Class (making Synapsida an Infraclass within the Class Sarcopterygii). The classification of this article takes somewhat of a traditional approach, considering tetrapods to be a sister group to the Sarcopterygians, whereas most authorities consider tetrapods to be descendents of Sarcopterygian fish. In the classification table to the upper right, notice the names that have an asterisk (*) denoting that they are paraphyletic groups. Paraphyletic groups are not a quality of the cladistic approach to taxonomy.

I substantially agree with this, but do you think that this page is the appropriate place to argue the case? We don't write essays here, and it's only tangentially related to the subject of this article. Besides, if Sarcopterygii were ranked as a class, Synapsida would rank considerably lower than an infraclass. (I.e. Sarcopterygii > Rhipidistia > Tetrapodomorpha > Tetrapoda > Neotetrapoda > Reptiliomorpha > Cotylosauria > Amniota > Synapsida). Nobody would like to get these clades ranked in a coherent hierarchy better than I would, but we do need some sort of taxonomic consensus for that before we can put it on Wikipedia : ) Gnostrat (talk) 02:34, 7 March 2008 (UTC)

Don't get stuck on the limiting rules of cladistics. Paraphyletic groups , or taxa, are perfectly fine even if they don't fall ideally in the cladistic scheme of things. If you want to designate them with an asterisk, ok by me. Cladistics and normal (traditionl) taxonomy view things from different perspectives, cladistics from the point of view of evolutionary continua, traditional taxomomy from the prespective of broader and broader moprhologic similarities (heiracharal taxa). The use of one doesn't (or at least shouldn't) invalidate the other.

As for those pesky paraphyletic groups that some seem to have a problem with, whether "valid" or not, they are certainly usefull. Cladistic sequences in which there are no ranks should be distingushed from ordinary taxonomic hierarchies or sequences in which derived taxa can take on rank equal to or greater than their immediate predicessor; such as having Class Mammalia derived from suborder Cynodontia (which make perfectly good taxonomic even if not cladistic sense) . J.H.McDonnell (talk) 23:26, 12 September 2010 (UTC) —Preceding unsigned comment added by J.H.McDonnell (talk • contribs) 00:04, 30 July 2008 (UTC)

Mammals as Synapsids

The article implies and states several times that mammals are synapsids. However, as synapsida and mammalia are both classes, I don't see how they can coexist like that. Can somebody clarify this?

Also, are there any extant synapsids, or are they all extinct? Asriel (talk) 12:41, 11 May 2008 (UTC)

Well mammals are synapsids. So as for extant synapsids go, you are one! The taxonomy of Synapsida and Mammalia is confusing as Wikipedia uses that of Benton (2004). Mike intentionally made Class Synapsida paraphyletic, so Class Mammalia does not fall within Synapsida. Strange but true. However, trying to create a rank-based taxonomy with Mammalia within Synapsida would suffer from an exceptional growth in taxonomic ranks about the Class level. For now, its a good compromise Mark t young (talk) 15:25, 11 May 2008 (UTC)

I'll just add that the section on 'Changing Classifications' explains it. Phylogenetically considered, mammals are synapsids. Nobody disagrees with that, but the formal ranking of Mammalia as a class in its own right is traditional, going back to Linnaeus himself. It's the old problem of fitting the fossils into a classification originally devised for living animals. Linnaeus' groupings have been changed before, of course, and I understand there have been proposals to formally demote the mammals to a subgroup of Synapsida. It would indeed require inserting lots of new ranks in between Class Synapsida and the living orders of mammals, but it could be done, and would probably look something like this:

• Class Synapsida
  • Subclass Eupelycosauria
    • Infraclass Sphenacodontia
      • Division Therapsida
        • Legion Mammalia

Tradition stinks. Classification needs to reflect reality. 72.192.219.19 (talk) 00:42, 7 July 2011 (UTC)

More's the pity that we can't do it like that on Wikipedia. But we can't invent classifications, we can only report them, and for any major shakeup of Wikipedia's classification I guess we have to wait until there's some sort of consensus for change among taxonomists, or at least make a decision to go with some other scheme that's at least as authoritative as Benton's. In the meantime, we're left with this awkward compromise of a clade Synapsida that includes mammals, but a class Synapsida that doesn't. Just to annoy you (well, it annoys me), I should point out that there's a very vocal school of taxonomy which, far from putting its energy into necessary improvements to the accepted Linnaean classification, is campaigning instead to sweep it away, ranks and all.

Short answer on extant synapsids: they're called mammals. All the others are extinct, though. More precisely: if you run into a Moschops on your travels, the entire zoological community will beat a path to your door. Gnostrat (talk) 16:02, 11 May 2008 (UTC)

Gents, classification and phylogeny are not the same thing. Synapsida is a perfectly valid class (or subclass of Reptilia if you follow a more traditional approach), and Mammalia is a perfectly valid class. At the same time, we all agree on the actual phylogeny here. Whether mammals have evolved from the synapsids or are surviving synapsids is a matter of semantics. The two statements express exactly the same phylogeny. Petter Bøckman (talk) 17:36, 7 July 2011 (UTC)

Consistency problem

The article can't seem to decide whether the mammalia are contained in the synapsida, or the synapsida are paraphyletic. Please make a choice and stick to it, because as it stands it's just contradictory and confusing. If notable alternative classifications exist, relegate them to a footnote. Shinobu (talk) 05:07, 27 December 2008 (UTC)

Which part specifically is contradictory or confusing? Dinoguy2 (talk) 15:03, 27 December 2008 (UTC)

There is very unfortunately no consensus on this sort of thing and this page reflects the opinions of taxonomists. Innotata 21:34, 26 October 2009 (UTC) —Preceding unsigned comment added by Innotata (talk • contribs)

Metabolism: possible language difficulty

"Some synapsids (including mammals) also have a warm-blooded metabolism, even though early synapsids, such as pelycosaurs, were most certainly cold-blooded." In British English, "most certainly" means "definitely". In US English (I think) it means "almost certainly" (i.e. probably). Which meaning is intended here? Wardog (talk) 10:07, 15 January 2009 (UTC)

I suspect that this was a typo. I've changed it to "early synapsids, such as pelycosaurs, are believed to have been cold-blooded."
We might very well want to cite this.
AFAIK, "most certainly" is not normally used in US English to mean "almost certainly" / "probably".
(I see that the expression "most certainly" occurs over 400 times in Wikipedia articles, and it looks like most of those would be clearer if rephrased.) -- 201.37.230.43 (talk) 16:14, 5 February 2009 (UTC)

Jawjoint

This section has seen some re-writing, but still only make sense to those intimately familiar with the various bones of the primitive tetrapod skull. I think the only way to get the point across to the general public is through illustrations. Petter Bøckman (talk) 20:38, 17 December 2009 (UTC)

Posture?

Do we really want to include the idea that limb posture in some way indicates metabolism? I mean, yes, it's an idea from the scientific literature, but it's a pretty damned stupid one, with zero support beyond a correlation based on an N=2 and no legitimate biomechanical justification that I'm aware of. Mokele (talk) 03:19, 3 February 2010 (UTC)

Don't blame me, blame Benton. N is 3 anyway (Reptiles, birds and mammals), and posture says something about mode of running/walking, which is obviously tied to metabolism. When I get better time, I'll cite the curled up Thrinaxodons. What buggs me is that I haven't been able to track down the two alleged skin imprints (skutes and fur respectively). I see them mentioned here and there, but never with a traceable citation. Petter Bøckman (talk) 08:33, 3 February 2010 (UTC)

EDIT: Comming to think of it, this theory hangs on the thecodontts. They had an erect pose, were they homeotherms or semi-homoetherms in any way? Hm, hm, hm Petter Bøckman (talk) 14:29, 3 February 2010 (UTC)

That's the thing - just because synapsids became more erect during the same time they became endotherms doesn't mean erect stance indicates endothermy. Hell, you can say the same thing about fur, since I have a hard time believing insulation was a major issue in the baking heat of the Permian desert or swamp. Studies on extant organisms show that "sprawling" lizards have the same net cost of transport (calories/meter) as mammals of the same size, and the primary problem with sprawling limbs (muscular effort to maintain posture) shows up in the highly-crouched limbs of most small mammals. Now, there's a fair possibility that posture controls speed for larger animals, because bone is weaker in torsion than in bending, but even that's dubious for a link to endothermy (plenty of ectotherms are quite fast, and anything smaller than a dog has a high bone safety factor regardless of metabolism).

In general, I'm wary of inferring metabolism from gross skeletal morphology, precisely because we have such a limited data set, but also because data on extant animals simply doesn't support some of the claims being made, particularly with regard to locomotion "efficiency" (the mis-use of which in locomotion is a pet peeve of mine). I think it's fair to note the increasingly erect posture, but we should either omit the implication about metbolism, or include a reference on modern studies showing the lack of difference between mammals and lizards of the same size (random trivia fact - snakes *also* have the same cost of transport as mammals & lizards when the snake is laterally undulating, so limbs *really* don't matter). Mokele (talk) 16:52, 3 February 2010 (UTC)

Are those values for ordinary walking speed, or do they include running? Sprawling gait leads to a sideways swinging backbone, and the mass that moves sideways when a big goanna or a crocodile walks is substantial. When they run, I would think they would need energy to counter the effect of sideways mass movement? I would assume the same to be true for a Dimetrodon, Walking with Monsters (episode II) has a very good reconstruction of one running. Or are we now in the land of original research/speculation here? Petter Bøckman (talk) 17:52, 3 February 2010 (UTC)

Class or subclass?

I noticed User:FunkMonk changed the classification from class Reptilia, subclass Synapsida to class Synapsida. I reverted the edits as I'd personally like to retain the traditional classification, though bout classifications are valid. So don't let this become an edit war, this is not a matter of phylogeny (which is amply covered in the text anyway), only on what should go in the taxo-box to serve Wikipedia best. A small round of pros and cons, please? Petter Bøckman (talk) 18:18, 25 April 2010 (UTC)

Well, as I understand it, Synapsida are a subset of Amniota, not Reptilia. So what's the problem? Why keep outdated information? FunkMonk (talk) 18:23, 25 April 2010 (UTC)

Depends on how Reptilia is being used. Traditionally, Reptilia and Amniota are basically synonyms, and Reptilia is doubly paraphyletic wrt Aves and Mammalia. Newer evolutionary taxonomy schemes like Benton 2004 (which was the original basis for these pages, mostly my fault ;) ) try to reduce the paraphyly of Reptilia by making it synonymous with Sauropsida instead (as do some phylo definitions of Reptilia). Benton is the one who made Synapsida a class rather than subclass, but as far as I know he's also the ONLY one, making it a minority usage. On the other hand, we'd have to restrucute the classifications and possibly merge Reptilia with Amniota or really intertwine them the way Reptilia is currently intertwined with Sauropsida, if we went back to the "traditional" reptilian subclasses. But even then, some of those traditional subclasses are themselves multiply paraphyletic, like Euryapsida. So it's a sticky situation not helped by the fact that PhyloCode is still years away and there's no consensus definition of Reptilia. MMartyniuk (talk) 00:15, 26 April 2010 (UTC)

As MMartyniuk said, the whole systematic is in the process if recasting these days. What the outcome will be is anyones guess, personally i hope for a divorce between Linnaean and phylogenetic systematics (bout have their uses, but trying to combine them just muddies the water). Until we know, we'll just have to stick to something that is practical for the taxobox, and put all the back and forth in the text (see Reptile for a good example of just that). The question is: Is Benton's class going to be the stable and most used outcome, or are we better served by sticking to the traditional, though possibly outdated subclass? I saw Synapsida used as a subclass of Reptilia in a standard textbook printed as late as 2001, so while it is certainly not modern, I'm not sure I quite agree with "outdated". As the page "Reptilia" directs to now, using Synapsida as a subclass is OK, though it will no doubt draw flack from the cladisticans. --Petter Bøckman (talk) 12:06, 26 April 2010 (UTC)

Less Jargon/more succinctness

This page contains a lot of jargon making it difficult to follow, or possibly just too many synonyms in the introduction. It needs to have a more succinct introduction that is easier for someone unfamiliar with the topic. For instance:

"Primitive synapsids are usually called pelycosaurs; more advanced mammal-like ones, therapsids. The non-mammalian members are described as mammal-like reptiles in classical systematics,[2][3] but are referred to as "stem-mammals" or "proto-mammals" under cladistic terminology."

Are primitive ones more reptile-like? What is going on in the second sentence? Where is the part that says what makes it reptile-like and where is the part where it says it's mammal like if the page redirects from that entry? —Preceding unsigned comment added by 98.237.245.25 (talk) 08:04, 17 July 2010 (UTC)

You are right. The problem here is that this article is right in the middle of the battleground between cladistical and Linnaean nomenklature. I'll have a look at it. --Petter Bøckman (talk) 10:47, 17 July 2010 (UTC)

I've tried to clear it up, see if it is better now.--Petter Bøckman (talk) 06:01, 19 July 2010 (UTC)

Largest animal?

In "Evolutionary History" section there is this piece of information:

"Today, there are 5,400 species of living synapsids known as the mammals, including both aquatic (whales) and flying (bats) species, and the largest animal ever known to have existed (the blue whale)."

Well, the Amphicoelias fragilimus was far bigger than the blue whale, reaching 40 to 60 meters. — Preceding unsigned comment added by 186.212.123.245 (talk) 15:25, 5 July 2011 (UTC)

Not by mass, though. Abyssal (talk) 20:28, 7 July 2011 (UTC)