Talk:Dimetrodon

Comment away Image

Commented away File:Dimetrodon2.jpg because it's not a Dimetrodon (GRr#*☇☹♏☭☠☢üXx!!), it's an Edaphosaur. Said: Rursus ☺ ★ 15:08, 1 June 2007 (UTC)

Seems to be a representation of the so-called Naosaurus, a composite of Dimetrodon and Edaphosaurus. Is that a painting from Charles Knight? If so, it can stay in the pop culture section. ArthurWeasley 15:59, 1 June 2007 (UTC)

It's certainly a Naosaur! ;-) But still, to me it looks like an extraordinarily morose Edaphosaurus that newly have been at the dentist to get an extraordinarily big paying bill. Said: Rursus ☺ ★ 11:24, 3 June 2007 (UTC)

The image HERE, indicates that Naosaurus is one paleontologists chimera, a Dimetrodon head put upon the body of an Edaphosaur. Pop culture it is: like Styganthropus piltdowni. Said: Rursus ☺ ★ 11:51, 3 June 2007 (UTC)

I can see how it's not a Dimetrodon. Dimetrodon had straight neural spines, while Edaphosaurus had them curved. Giant Blue Anteater 21:49, 9 June 2007 (UTC)

Wrong. Edaphosaurs have spikes on their neural spines. The great new illustrations have the spines curved. Giant Blue Anteater 07:38, 16 June 2007 (UTC)

Has historical significance, so I think it could be included where it is discussed. Also, we have many other interesting but unused images on Commons, and lots of space here. FunkMonk (talk) 02:39, 22 August 2013 (UTC)

Dimetrodon: a SYNAPSID

I am tired of this. first, tanystropheus is part of wikiproject dinosaurs (it isnt even related) and mow dimetrodon is featured on wikiproject amphibians and reptiles, although it is niether. Please reasign it to wikiproject synapsids, if such a thing exists.T.Neo 15:21, 28 August 2007 (UTC)

There is simply no wikiproject synapsid but you are welcome to initiate it if you like. In the meantime, the article Dimetrodon is maintained by the wikiproject amphibians and reptiles team. Please note that wikiprojects do not function as categories, it is just saying which team claims responsability over an article. Tanystropheus is maintained by the Wikiproject dinosaur because this animal was one thought to be a dinosaur. ArthurWeasley 15:36, 28 August 2007 (UTC)

Also remember that traditionally synapsida is a subclass of reptilia... the whole reptile/synapsid split (actually synapsid/sauropsid) is pretty new and probably not widely known about outside vert paleo... not sure who started defining reptilia to exclude mammals anyway. Probably whoever defined Amniota as a clade ;)

Either way, the fact that it's called WP: Reptiles and amphibians pretty much implies it's meant to be a project for all non-mammalian, non-avian tetrapods, doesn't it? There is no monophyletic clade containing Amphibia (crown group) and Reptilia (sauropsids) in the cladistic sense. Dinoguy2 16:05, 28 August 2007 (UTC)

Synapsids are no longer considerd reptiles as they do not have scaly skin and do not excrete uric acid. I would be glad to initiate a wikiproject synapsids. T.Neo 12:31, 30 August 2007 (UTC)

Only one problem: how do I initiate a wikiproject synapsids? T.Neo 12:35, 30 August 2007 (UTC)

No... they're no longer considered reptiles because somebody re-defined Reptilia specifically to exclude them, so that Amniota would not refer to the same clade as Reptilia. I believe (don't have a cite handy) early synapsids did indeed have scales based on pelycosaur skin impressions. While modern synapsids don't excrete uric acid I don't know of evidence saying primitive members did not, and that was never used as part of any definition anyway. Dinoguy2 14:46, 30 August 2007 (UTC)

I still dont think synapsids are reptiles but the thought that pelycosaurs had scales is fascinating. but what about the later synapsids(therapsids) when did fur appear? and what was the skin covering for dicynodonts? T.Neo 13:36, 31 August 2007 (UTC)

I don't think any evidence of fur is known for anything earlier or more primitive than Castorocauda lutrasimilis actually... hopefully somebody will correct me if I'm wrong. As far as I know the skin covering of non-mamaliaform therapsids is totally unkown. And it's fine that you don't think synapsids are reptiles, just be aware that this is because of a human-made, arbitrary definition that there are alternatives to, and not anything "real" about the animals themselves. This is an easy mistake to make in the new cladistic system that doesn't take physical features into account when making classifications.Dinoguy2 17:48, 31 August 2007 (UTC)

I dont think synapsids are truly reptiles, but probably very similar. Scary that people can play around with classifications put animal where they might not belong. 196.208.83.113 10:57, 1 September 2007 (UTC)

Pronunciation

This is a topic that covers at least all extinct life forms known under scientific name: there is an IPA-help pronunciation, sometimes a phonetic spelling. The problem i see there, that those pronunciations are English, and i dont really get the clue, why in an English article the ENGLISH pronunciation would need to be explained; but rather the original Greek one would be in need (something like Dee-ME-tro-don). Help and suggestions welcome.--84.63.244.80 (talk) 05:20, 26 November 2007 (UTC)

Trivia

There seems to be something of an edit conflict over what should be included in the trivia section between SteveOC 86 and Puncharoo. Personally I tend to be leaning towards Puncharoo's side. Is there any real reason to remove his additions? Abyssal leviathin (talk) 00:35, 2 March 2008 (UTC)

The relevant guidelines are here: Wikipedia:Handling trivia. See especially the section on Connective Trivia.

Are these minor appearances of Dimetrodon important to the shows/games mentioned? A good test is to see if they're discussed in those articles. Checking a few, Strong Bad and World of Warcraft don't mention this animal at all. If it's not important enough an appearance to make it into the parent article, it's certainly not important enough for this one. Dino-Riders mentions Dimetrodon briefly and includes it in a list, but that may still not be important enough to the topic of Dimetrodon to include it here. Wikipedia is not a giant game of Six Degrees of Kevin Bacon you know! ;) Dinoguy2 (talk) 21:12, 2 March 2008 (UTC)

Additionally, I think this statement from the article sums up my philosophy on trivia: "an ideal Wikipedia article would present its subject in a straightforward but well-organized way, and refer the reader to other articles or outside resources where more details can be found." What additional information about or relating to Dimetrodon can be found in articles like Zoo Tycoon 2: Extinct Animals, or Super Sentai? I'm not seeing any. The only 'interesting' information seems to be that these things mention Dimetrodon. That's trivia for it's own sake, and is useless. Somebody playing Zoo Tycoon may want to learn more about Demetrodon, but why would somebody reading about Dimetrodon want to learn about Zoo Tycoon? Dinoguy2 (talk) 21:41, 2 March 2008 (UTC)

I didn't intend to get into an edit confict, I was trying to follow the guidlines shown above. From my experiance on wiki it can be difficult to persuade certain people about the relevance of pop culture to science articles and many of the prehistoic creature articals get it a lot which can be frustrating at times. It's also difficult to judge wether people are aditing in good faith or just trying to vandalise. I really should have sent a message to his user page, it's difficult not to come off strong when writing short messages in the edit summery. Steveoc 86 (talk) 01:24, 3 March 2008 (UTC)

Intro sentence.

As of right now, the intro contains this:

"It was more closely related to mammals than to true reptiles (Sauropsida), like dinosaurs, lizards and birds."

What is that sentence trying to say? That dinosaurs, lizards and birds are types of true reptiles? That dinosaurs, lizards and birds are like dimetredon with regards to being more closely related to mammals than to true reptiles? Or that dinousaurs lizards and birds are rather the opposite of dimetroden in this regard, being more closely related to true reptiles than to mammals? --Atethnekos (talk) 04:55, 1 May 2008 (UTC)

I'll rephrase this--the first option is the intent. Dinoguy2 (talk) 01:15, 2 May 2008 (UTC)

contested statement removed

• The climate of Europe and North America in the Early Permian was probably arid to continental, so Dimetrodon was probably adaptable. {{Fact|date=December 2006}}

Please do not reinsert this information without a citation--BirgitteSB 15:43, 4 June 2008 (UTC)

Relationship

Is Dimetrodon one of our cousins?Phthinosuchusisanancestor (talk) 12:06, 1 January 2009 (UTC)Phthinosuchusisanancestor

All living things are related. So Dimetrodon is one of our "cousins", for a loose enough definition of "cousin", but so are tapeworms, sea sponges, venus fly traps, and amoeba. Relationships are only meaningful in a relative sense - we're more closely to Dimetrodon than to some other creatures, and also less closely than some other creatures. All that can be meaninfully said is: (a) we are the closest surviving relatives of Dimetrodon, although we are tied for this position with all other mammals, and (b) Dimetrodon is the most closely related to us of all well-known non-mammalian fossils, for a certain value of "well-known". In particular, Dimetrodon and us are more closely related to each other than either of us is to dinosaurs, trilobites, or the like. However, it's still less closely related to us than a number of well-known extinct mammals, like mammoths and saber-toothed cats. It's also less closely related to us than a number of only-moderately-known non-mammalian synapsids like gorgonopsids. -- Milo —Preceding unsigned comment added by 195.241.9.38 (talk) 21:12, 25 December 2009 (UTC)

"Dimetrodon is also known as an ancestor of modern humans." This can't possibly be true, can it? That dimetrodon is known to be an ancestor to humans? — Preceding unsigned comment added by 209.205.243.16 (talk) 13:02, 17 August 2012 (UTC)

No, this is a gross oversimplification. The fact is that Dimetrodon is closely related to the ancestors of all modern mammals including humans. But this type of fact is too boring for a show like Walking With Monsters (which was listed as the source). They need to make things sound more sensational than the truth to get ratings ;) MMartyniuk (talk) 18:29, 17 August 2012 (UTC)

Sail structure

I'm a little confused about the sail. From what I can gather, the vertical structure of the sail is provided by exaggerated spinous process projections. From my limited understanding of its anatomy, this would seem to have a few practical implications:

1. The animal would be unable to collapse the sail. It would always be fully fanned open and perpendicular to its back.

2. Torquing the sail could cause a serous injury to the animal, unless there's some sort of mechanism to prevent this.

The sail structure seems very impractical. But I'm sure I'm just not understanding how it interfaces with the rest of the body. Could someone knowledgable please address these points of confusion in the article?

Thanks. --Loqi (talk) 21:41, 12 May 2009 (UTC)

Correct, the sail was in no way collapsible. Each sail-supporting spine was anchored to a different vertebrae, and connected by flexible skin. So when the animal walked or ran, or curved its body in a manner that torqued the sail, the sail could 'bend' along with it. The animation for this in the TV series Walking With Monsters is a good example if you can find it. I don't have any papers on Dimetrodon anatomy or biomechanics from which I could update the article unfortunately (if such papers even exist), but I'll look around. Dinoguy2 (talk) 17:48, 13 May 2009 (UTC)

Thanks for that Dinoguy2. I found the Walking with Monsters animation. http://www.youtube.com/watch?v=mvcIoOhtPDQ The artists showed an unexpected running stride, with much more horizontal undulation than I would've expected.

If the main purpose of the sail is temperature regulation, they'll need some mechanism to capture the benefits. (Blood flow control in the sail skin?) When the article says they get more time to be active, this implies that the sail must have some way of grabbing "good" temperature while avoiding "bad" temperature.

What I meant by "torquing" is if something shoves one of the vertical bone projections, it becomes a huge wrench against a single spinal vertebra. That seems like a very dangerous liability. Is there some kind of anatomical safety feature to protect the vertebrae? --Loqi (talk) 00:05, 21 May 2009 (UTC)

I'm not sure what circumstances would lead to torquing the sail laterally... do you mean, say, in intraspecific combat? The spines are pretty slender, I imagine they'd snap before causing any injury to the backbone. Or the animal would simply tip over on its side. It couldn't cause a wrench against a single vert because its connected to all the other spines by a fairly narrow piece of skin that wouldn't allow much lateral independent motion without pulling the other ones along. Dinoguy2 (talk) 05:14, 21 May 2009 (UTC)

Naosaurus

Naosaurus is being redirected here incorrectly, since it is a synonym of Edaphosaurus. This may be due to a confusion with Neosaurus, but I don't know how to fix redirects. CFLeon (talk) 20:17, 14 August 2010 (UTC)

Fixed. To visit the redirect page, after it redirects you there will be a link under the page title saying "Redirected from x," just click the link to the redirect and it'll take you to its page for you to edit. Abyssal (talk) 20:35, 14 August 2010 (UTC)

GA Review

This review is transcluded from Talk:Dimetrodon/GA1. The edit link for this section can be used to add comments to the review.

Reviewer: Maky (talk · contribs) 20:21, 1 September 2012 (UTC)

I will be doing this review soon. It looks like an interesting read. – Maky ^« talk » 20:21, 1 September 2012 (UTC)

Comments:

• "Most Dimetrodon species ranged in length from 1.7 metres (5.6 ft) and are estimated to have weighed between 28 kilograms (62 lb)." – No range given. Given the sentence that follows it, I'm confused.

Fixed. That was an error using Template:Convert. Smokeybjb (talk) 03:46, 2 September 2012 (UTC)

• I know I do this with subfossil lemur genera, but given number of species and the extreme differences in size, is there a reason why each species doesn't merit its own article? I would understand it if they were very similar or poorly known from the fossil record, but it feels like we should be able to say much more. What brought this up is that I looked at the link for Tappenosaurus, and it says that it's from the Middle Permian, but Dimetrodon is from the Early Permian... yet this article said they were found together. Since there's such a variety of Dimetrodon species, I figured I'd look to see if they all are listed as Early Permian. I know the other article isn't part of this GAN, but it's important that we're consistent, and I wasn't able to check that consistency.

My mistake with Tappenosaurus. I rechecked some papers and Dimetrodon material hasn't been found in the same formation, so it's still restricted to the Early Permian. As for the species, there seems to be a consensus originating from Wikiproject Dinosaurs that articles stop at the genus level, at least for long-extinct taxa. I don't think enough information exists for each Dimetrodon species to have its own article (a lot of them are distinguished by very small details in the skull or vertebrae, and others are based on a few scraps of bone) but a List of Dimetrodon species article may be a good idea. The same was done in List of Psittacosaurus species. Smokeybjb (talk) 04:19, 2 September 2012 (UTC)

• Sphenacodontids are not introduced or linked on first mention.

Linked sphenacodontid and mentioned in the lead that Dimetrodon is in the family Sphenacodontidae. Smokeybjb (talk) 03:46, 2 September 2012 (UTC)

• A summary for File:Archaeothyris BW.jpg is needed on Commons. Other images used could use sections for their summary on Commons. (Basically, standard clean-up work for older uploads.) The latter isn't required for GA, but is always good to do.

Done. Thanks for all the input so far. Smokeybjb (talk) 04:26, 2 September 2012 (UTC)

• It might be good to explain or link anatomical words like "proximal" or "distal" for those not versed in anatomy.

Done. Smokeybjb (talk) 22:35, 2 September 2012 (UTC)

• "Many follow Haack's 1986 paper in concluding that the sail was poorly adapted to absorbing and releasing heat." – I thought it said above that it Haack claimed it was good for absorbing but not releasing heat.

Fixed. You're right, just bad at releasing heat. Smokeybjb (talk) 22:57, 2 September 2012 (UTC)

• "Based on these differences, the mounted skeletons... are males... are females" – Are the the sources certain, or is this speculation? The caption of the photos sounds less certain than the text. Just checking.

Definitely speculative. I've reworded the text to say "have been hypothesized" and "may be" males and females. Smokeybjb (talk) 22:42, 2 September 2012 (UTC)

• I suggest adding non-breaking spaces between numbers and units (e.g. 60 million years), abbreviated genera and species names (e.g. D. cruciger), and anything else that would be hard to follow if they got broken apart at the end of a line.

Done. Smokeybjb (talk) 22:29, 2 September 2012 (UTC)

• "Paleontologists believed..." – I don't know... call me a hard-liner, but I cringe every time I hear the word "believe" used in scientific discussion. Belief, to me, means accepting something regardless of proof. I prefer "thought", "suspected", "reasoned", etc... But again, maybe I'm just being too picky.

Not at all. It's an important distinction to make. Smokeybjb (talk) 22:32, 2 September 2012 (UTC)

• "Below is a cladogram modified from the analysis of Benson (in press)..." – I don't think it's "in press" any more.

It looks like it's still in press. It's still listed as a "forthcoming article" here, and hasn't yet been printed in an issue of the journal. Smokeybjb (talk) 22:29, 2 September 2012 (UTC)

Following the DOI link, I see: "Version of record first published: 27 Mar 2012" Maybe I'm not seeing it... – Maky ^« talk » 01:05, 4 September 2012 (UTC)

Yes, but that's the date it was published online ahead of print. The official publication date is when it's printed in a paper issue of the journal. Sometimes an article makes its way into an issue the year after it first appears online, which might turn out to be the case for this article. Then it would end up being Benson (2013). Smokeybjb (talk) 01:53, 4 September 2012 (UTC)

• "Dimetrodon was first described by American paleontologist Edward Drinker Cope. ... In 1878, Cope established the name Dimetrodon when he described the species Dimetrodon incisivus..." – I assume these are the same year? To me, it's a little awkward because I start off wanting to know when, but it isn't mentioned until later, at which point the article starts giving dates for other publications.

Reworded. How is it now? Smokeybjb (talk) 03:52, 4 September 2012 (UTC)

Good for me. – Maky ^« talk » 17:08, 4 September 2012 (UTC)

• "In 1897, Case and his colleague Georg Baur followed Cope’s original classification by placing Dimetrodon as a rhynchocephalian." – Didn't Cope initially put them in this group?

Changed the wording to "reclassified". Smokeybjb (talk) 03:52, 4 September 2012 (UTC)

• The "History of study" section seems a bit long, and seems like it should be broken into subsections. Also, it spends a lot of time talking about the history of synapsid taxonomy, which I know Dimetrodon played an important role... It's making me wonder if some of the material might fall outside the scope of the article. However, let's discuss this before you remove anything. It may be fine as is.

The main reason I wanted to talk about taxonomy is to explain the various interpretations of where Dimetrodon fit in evolutionary terms. A lot of the information might do better in another article like Synapsida, but I still think some of it is important to mention. Maybe the history section could be split up entirely, with the naming of different species under the "Species" subsection of the "Classification" section, and the classification of Dimetrodon under the "Evolutionary relationships" subsection. If we keep the "History of study" section, I think the subsection headings should be titled either by time period (like "Nineteenth century", "Early twentieth century") or by researcher (Cope, Case, Romer). What do you think? Smokeybjb (talk) 04:09, 4 September 2012 (UTC)

I definitely agree that some of the information could moved/copied to Synapsid, and maybe some could be trimmed from the article. (Don't be afraid to use a "See also..." or "Main article..." below the subheadings.) Also, I like the first idea, where stuff is moved under "Species" and "Classification". I'm not sure if I like the idea of subsections by time period or researcher. – Maky ^« talk » 17:08, 4 September 2012 (UTC)

OK, since I can't really think of a way to discuss how the evolutionary relationships of Dimetrodon have changed without drifting into how larger-level taxonomy has changed, I've removed those paragraphs. Most of it will probably end up in the synapsid article once I get around to it. As it is now, the "Evolutionary relationships" section already alludes to some of the old classification schemes. Smokeybjb (talk) 20:50, 5 September 2012 (UTC)

• "Clear Fork Group, the Wichita Group, and the Pearce River Group" – Since these are red-linked, could you provide (in parentheses) information about where the location of these groups?

OK, mentioned that they are exposed in north-central Texas and south-central Oklahoma. Smokeybjb (talk) 03:52, 4 September 2012 (UTC)

• "According to Olson, the land-based large-herbivore-dominated land ecosystems continued into the Mesozoic Era and are still present today while the aquatic-based ecosystems are rarer than they were in the Early Permian, existing today in places such as the Everglades." – This really seems to fall out of scope for the article. I think it can also be misleading, especially for people not versed in paleoecology. Your thoughts?

I think you're right. I took it out so it just says that the Everglades is a good model for the ecosystem of Dimetrodon. Plus, it seems like Olson was making some big generalizations about how ecosystems have changed since then. Smokeybjb (talk) 03:52, 4 September 2012 (UTC)

• In the lead: "...and went extinct around 30 million years before the appearance of the first dinosaur in the Triassic period." – I'm not sure if this can be seen as a summary of material from the body, unless I missed something.

That's a mistake. I corrected it to 60 million years, which is also mentioned in the beginning of the section on evolutionary relationships. Smokeybjb (talk) 03:52, 4 September 2012 (UTC)

Glad we caught that! – Maky ^« talk » 17:08, 4 September 2012 (UTC)

• In the lead: "...and there is evidence that juveniles lived in different environments than adults to avoid competition and predation." – I thought this was discredited?

I changed the wording to "cast doubt." I can't find any mention of the idea after Brinkman's paper, so it's hard to say he had the last word on the subject. Smokeybjb (talk) 01:53, 4 September 2012 (UTC)

In the lead, maybe change the wording from "there is evidence" to "there may be evidence", or something like that? – Maky ^« talk » 17:08, 4 September 2012 (UTC)

Done. Smokeybjb (talk) 20:13, 5 September 2012 (UTC)

• Is there any information about the appendicular skeleton? It seems like some of the major differences between the older reconstructions and modern reconstructions have to do with how Dimetrodon carried its weight.

There's one paper that goes into detail on the arms of Dimetrodon, but it's from 1927 and there might not be much useful information to include in this article. I'm guessing a lot of the features are also seen in other early synapsids and may be out of scope for the article, but I'll read through and see. Smokeybjb (talk) 01:53, 4 September 2012 (UTC)

Yeah, I kept sensing that when I read the article. I couldn't tell if I was reading an article about synapsids or Dimetrodon. But that will happen when you talk about topics this closely related. Unfortunately, it makes it a challenge to sort where the information should go. I recommend compiling a list of topics for each subject and sorting the information based on how you divide that list. With topics that have to be in both, choose one article to summarize and the other to provide details. Again, use "See also..." or "Main article..." as needed. (The nice part about this is that you will also be greatly improving Synapsid in the process.) – Maky ^« talk » 17:08, 4 September 2012 (UTC)

I couldn't find any specific information on the appendicular skeleton of Dimetrodon. The paper goes into detail about reconstructing muscles, but I bet that by now most of it is obsolete. I think the differences in how Dimetrodon carries itself in restorations has more to do with the modern trend of making animals look more active and less sluggish than with different anatomical interpretations. I did find some good information on the tail, though. Smokeybjb (talk) 20:13, 5 September 2012 (UTC)

• Source check: "Dimetrodon kempae was named on the basis of a single humerus, and may therefore be a nomen dubium indistinguishable from other species of Dimetrodon." – According to your source, it says "it may pertain to a sphenacodontid of some other genus."

Ah, I didn't notice that. I added some more information on it. Smokeybjb (talk) 01:53, 4 September 2012 (UTC)

Overall, a very good, informative article. I learned a lot. Once we settle the remaining issues above, I'll be glad to pass the article. – Maky ^« talk » 01:05, 4 September 2012 (UTC)

A suggestion for making this a good article is to split up some of the longer chapters (like the sail and the fossil species history) into smaller subchapters. As of now, much of the article comes across as a wall of text and is very hard to read. Petter Bøckman (talk) 20:01, 12 September 2012 (UTC)

Yes, this is the basic suggestion I have been waiting on. It goes a little beyond just being a wall of text, but also includes scope issues. I am giving the nominator time to resolve the issues. – Maky ^« talk » 19:09, 13 September 2012 (UTC)

Actually, I looks like I missed some edits and replies. I will recheck the scope issue once the flagged issues in the article and on the talk page are addressed. – Maky ^« talk » 19:12, 13 September 2012 (UTC)

I've been away from editing for the past few days, so sorry I couldn't address this sooner. How about just removing the section on the history of species names? Average readers probably aren't looking for this level of detail, and I can add it to a List of Dimetrodon species article that I proposed earlier. Smokeybjb (talk) 20:12, 14 September 2012 (UTC)

I have tried to split up the longer sections a bit, I hope it helps. I agree the history section can go in a list of Dimetrodon species, it is rather dominating where it is. The sail section is stil on the long side, I can't really see how I should carve it up. Petter Bøckman (talk) 20:45, 15 September 2012 (UTC)

Thanks for helping out. I'm transferring some of the information in the history section to the under-construction species article at my sandbox, so I'll do some trimming to this article soon. I'm thinking of keeping some paragraphs on fossil collectors and Cope's first descriptions since they are relevant to Dimetrodon as a whole. As for the sail section, I agree it might be on the long side, but I think if it is split it will appear very fragmented. Smokeybjb (talk) 21:17, 15 September 2012 (UTC)

Sorry for the delayed response. I think a lot of what is being discussed on the talk page will help make the finishing moves towards GA. I've been monitoring it loosely, and will try to find time to check in soon to re-evaluate. But at this point, with all the discussion going on, I wouldn't be able to pass it GA. Once things are resolved there, I will take another look. – Maky ^« talk » 15:30, 17 September 2012 (UTC)

• The discussion on the talk page appears to have concluded 20 days ago, and the last edit to the article is over a month old. Is there any chance that this review can be revived and some action taken soon? Many thanks. BlueMoonset (talk) 23:32, 22 October 2012 (UTC)

• Sure. I'll try to review it again tomorrow night. There was a very long discussion on the talk page that started up just as I was about to wrap things up, and I've been waiting for an "all clear" to resume the review. – Maky ^« talk » 00:54, 23 October 2012 (UTC)

New comments

• There are some weasel words, such as "...is thought to..." or "Some recent studies argue..." that need to be addressed in the article.

I removed the first one, but the studies (Haack, 1986; Tomkins et al., 2010) are attributed later in the text. WP:WEASEL says that these phrases can be used in the lead so long as they are attributed later on. Smokeybjb (talk) 17:17, 30 October 2012 (UTC)

Fair enough. – Maky ^« talk » 02:26, 1 November 2012 (UTC)

• Under "Skull", I don't think the heading "General shape" is needed. Usually, I put very general information directly under a header, and then categorized extensive details under subheaders.

Removed. Smokeybjb (talk) 16:55, 30 October 2012 (UTC)

• The D. grandis skull image could use a better caption. A lot of people like to include a link to the location the photo was taken, but that's what the description field is for on Commons. Anyway, that kind of stuff only advertises for the organization and doesn't provide helpful information to the reader. The sexual dimorphism comparison caption is better, but again, the location links are already given both on Commons and in the body text.

I removed the link to the museum for the skull, but not for the sexually dimorphic skeletons because I think the institution names are necessary for identifying the specific skeletons already mentioned in the text (I could find their specimen numbers if you'd prefer). Smokeybjb (talk) 16:55, 30 October 2012 (UTC)

There is also the location in the taxobox, which seems a little too much, IMO. Again, it comes across as advertising, and I've seen many attempts to replace images in articles with the sole purpose of noting the image location (e.g. a particular zoo). That's why I'm a little touchy about it. As for the comparison, my opinion isn't as strong. It could stay as is, if you like. Otherwise, I would personally do as you suggest—mention the specimen numbers in the body, and then reference the specimen numbers in the caption instead of the locations. It's up to you. – Maky ^« talk » 02:26, 1 November 2012 (UTC)

I managed to find specimen numbers for two of the skeletons (one of which now happens to be in Denver, not Harvard) and replaced the Field Museum photo since that skeleton doesn't seem to be the same as the one referenced in the source. I can't find the specimen number for the Michigan skeleton. Ideally I could replace it with a photo of the Denver skeleton, but the only images I could find of it on Flickr ([1][2][3][4][5]) don't have suitable licenses for upload to Commons. Maybe the caption could just say "the left skeleton may represent the male type and the right skeleton may represent the female type." What do you think? Smokeybjb (talk) 20:11, 1 November 2012 (UTC)

Damn... I'm sorry to see a good image get replaced by a poor-quality one (with bad reflections). Otherwise, yes, I would go with that simpler caption. – Maky ^« talk » 22:55, 1 November 2012 (UTC)

I went to the AMNH a few months ago and took a picture of the skeleton - not as good in quality as the Field Museum photo, but better than the one currently in the article. I'll upload it. Smokeybjb (talk) 23:34, 1 November 2012 (UTC)

• Please either link or briefly explain "caniniforms".

Done. Smokeybjb (talk) 16:55, 30 October 2012 (UTC)

• Link first mention of transitional.

Done. Smokeybjb (talk) 16:55, 30 October 2012 (UTC)

• Is there a reason for the forced line break before the "Sail" section? IMO, it creates unnecessary white space.

Removed. It might have been added to prevent sandwiching of the "Sail" section between the two pictures, but the page looks fine without it on my screen. Smokeybjb (talk) 16:55, 30 October 2012 (UTC)

IMO, that kind of stuff is so situational (based on browser, resolution, browser width, etc.) that I don't see why it matters. As long as we test things out as best we can, that's all we can do. It looks fine to me. – Maky ^« talk » 02:26, 1 November 2012 (UTC)

• The caption for the old restoration should probably explicitly state that it is no longer considered accurate and explain a tiny bit more about the short tail inaccuracy.

Done. Smokeybjb (talk) 16:55, 30 October 2012 (UTC)

Perfect! – Maky ^« talk » 02:26, 1 November 2012 (UTC)

• Link first instance of "sexual selection".

Done. Smokeybjb (talk) 16:55, 30 October 2012 (UTC)

• Under "Species", I almost feel like the table belongs in the list article and that a brief summary and shorter lists are needed in this section. Your thoughts?

I'm not sure. It would be hard to summarize the species without getting into the history of their naming, which was why I moved the descriptions to a new species article. I think the table is a good way of seeing at a glance which species are currently included in the genus, and which are no longer recognized. The table would be redundant in the species article, since all the information it contains is already expressed in words. Smokeybjb (talk) 17:01, 30 October 2012 (UTC)

Let me think about this while you address the lingering caption issue above. From my experience, list articles usually involve tables (with an informational lead at the top), while articles usually have text and maybe a small table or bulleted list. My gut tells me that this article should have a bullet list with a very brief summary of what is in the list article, and that the table belongs with the list. For GA, I may just let this go. If the article were to go to FAC, I would expect some discussion on this point. – Maky ^« talk » 02:26, 1 November 2012 (UTC)

I'm going to let this issue pass, though I will not strike it. Again, if this article goes to FAC, I feel it should be revisited with a more careful reading of WP:TABLE. (It may be fine... but it depends on how things are interpreted, I think.) But for GAN, I think it's fine. – Maky ^« talk » 22:55, 1 November 2012 (UTC)

• Link first mention of Red beds.

Done. However, the Red beds article isn't about the Texas and Oklahoma Red Beds in particular. Maybe a red link to Red Beds of Texas and Oklahoma (or some other name of that sort) would be better? Smokeybjb (talk) 16:55, 30 October 2012 (UTC)

Yes, sorry... I thought it was the appropriate article because I didn't look closely. The red link is fine. Hopefully someone creates the article. Maybe create a stub since you have a source that mentions it? (That would be "extra credit", IMO.)  ;-) – Maky ^« talk » 02:26, 1 November 2012 (UTC)

• Link first mention of description.

Done. Smokeybjb (talk) 16:55, 30 October 2012 (UTC)

• In the lead, I would suggest noting that it was primarily found in North America and only recently discovered in Europe. It might even be good to list which states/regions have the richest Dimetrodon finds.

Done. I also added a mention of the Red Beds. Smokeybjb (talk) 16:55, 30 October 2012 (UTC)

• I'm not sure the subheading "Paleoenvironment" is needed under "Paleoecology"—the material seems general enough for that section.

Removed. Smokeybjb (talk) 16:55, 30 October 2012 (UTC)

The article looks much better and feels much more like an article about Dimetrodon than it does an article about synapsids and the history of their study. Once these issues are resolved, I feel comfortable passing the article. – Maky ^« talk » 00:51, 24 October 2012 (UTC)

Oops, I've been away from editing for a while with real life chores and forgot about this review! I'll get started on addressing your new comments today, and hopefully we can wrap this up. Smokeybjb (talk) 16:27, 30 October 2012 (UTC)

GA review (see here for what the criteria are, and here for what they are not)

1. It is reasonably well written.

   a (prose): b (MoS for lead, layout, word choice, fiction, and lists):

2. It is factually accurate and verifiable.

   a (references): b (citations to reliable sources): c (OR):

3. It is broad in its coverage.

   a (major aspects): b (focused):

4. It follows the neutral point of view policy.

   Fair representation without bias:

5. It is stable.

   No edit wars, etc.:

6. It is illustrated by images, where possible and appropriate.

   a (images are tagged and non-free images have fair use rationales): b (appropriate use with suitable captions):

7. Overall:

   Pass/Fail:

Thanks for the review! Sorry for slowing the process down with my absence these past few weeks. I really appreciate all the help you've given. Smokeybjb (talk) 01:23, 2 November 2012 (UTC)

Positive allometry

It's been brought up[6] that positive allometry is an unnecessarily technical point for this article to mention. I'm disagreeing because I think it is adequately explained and it is an important term in the study of thermoregulation in Dimetrodon and other animals (see this study, which uses the term). Saying surface area increases faster than mass was an error, but that doesn't mean it's incorrect to describe the sail as an example of positive allometry. Smokeybjb (talk) 01:25, 10 September 2012 (UTC)

Of course, the sail is an example of positive allometry. If pointing this out will increase the reader's understanding of the issues around the sail's function, and if the statements using the concept are readily understandable and accurate, I'm all for it. I don't see that these conditions are met, however, nor have I seen a way of meeting them, so—in the edit linked above—I provided what I regarded as an adequate presentation of the matter without use of the concept.

We are told that

Positive allometry has been taken as evidence that the sail of Dimetrodon evolved through sexual selection, since individuals with large sails relative to their body size may have attracted more mates.

Positive allometry is not evidence for such evolution, since the competing hypothesis, that the sail evolved for thermoregulation, also predicts positive allometry.

I do not see how

. . .surface area increases rapidly in comparison to increasing mass. . . .

(the wording Smokeybjb proposes) is an improvement over the prior wording:

. . .surface area increases faster than mass. . . .

The statement with "in comparison" is rather obscure. What is being compared? The rate of increase in surface area vs. the rate of increase in mass? And is it the implied result of the comparison that the former is greater? This is just to say that surface area increases faster than mass, which is admitted to be incorrect. What, then, is the intended meaning of the proposed statement?

A related matter: If the word "scaling" is to be used, some clarification is needed. The meaning is not one found in standard dictionaries. The closest definition in The Free Dictionary is "To make in accord with a particular proportion". But who is doing the making: human investigators? Human activity is not "beneficial for thermoregulation" among dimetrodons.

Peter M. Brown (talk) 13:37, 10 September 2012 (UTC)

First point about positive allometry not being evidence of sexual selection: it is stated as evidence of sexual selection in the paper I linked to (Tomkins et al., 2010). Maybe you disagree with the paper's interpretations, but that is original research. As far as I know, there hasn't been a more recent study that has specifically questioned the findings of Tomkins et al.. Second point about thermoregulation: the article is comparing the rate of increase in the sail's surface area vs. the rate of increase in mass. The sail's actual rate of increase in surface area is greater than would be expected if it were used only for thermoregulation, as explained in the paper. The surface area of the sail would be expected to increase at a certain rate relative to the increase in overall body mass in order to be an effective thermoregulator. But the paper explains that it is increasing faster than that expected rate, and in the authors' opinions, that is evidence of sexual selection. I don't think "surface area increases rapidly 'in comparison to increasing mass" means "surface area increases faster than mass", but if you think there's a better way to word it, please suggest it. Smokeybjb (talk)

Responding to your points:

• As I have explained, I'm not able to parse the "in comparison to" version in a way that makes it correct, and I don't think your readers will be able to do so. As far as an alternate wording, I think that my edit was acceptable:

It is beneficial for thermoregulation when surface area increases at least as fast as mass as individuals get larger. Larger-bodied animals generate. . . .

Another alternative is to use your wording above: not only is the allometry positive, but the sail's actual rate of increase in surface area is greater than would be expected if it were used only for thermoregulation.

My view is that mere positive allometry falls so far short of what is needed for thermoregulation that it's not even worth mentioning.

Peter M. Brown (talk) 19:59, 10 September 2012 (UTC)

• Further, what Tomkins et al. take as evidence for sexual selection as the principal function of the sail is not that the allometry is positive but that it greatly exceeds what is useful for thermoregulatory purposes. What they say (italics mine) is:

• If the trait has an allometry significantly in excess of the exponent expected from physics, then an alternative explanation is needed. In these cases, sexual selection must be a strong candidate. . . .

• We found that sail height scales with an exponent significantly greater than expected for an organ dedicated to the dissipation of heat ( L^1.69 vs. L^1.125 ). . . .

• . . .the allometry is too steep for heat dissipation to be the primary adaptation favoring sail evolution.

Positive allometry means an exponent greater than 1. If thermoregulation were the primary function of the sail, positive allometry would be expected with an exponent of 1.125, but the exponent actually found is 1.69. What is significant is not that 1.69 is greater than 1, so that the allometry is positive, but that it is significantly greater than 1.125.

This is a carefully written and impressive paper. It is not surprising that no more recent study that has specifically questioned its findings. What it takes as evidence for sexual selection as the driver of sail size, however, is not that the allometry is positive but that it is so much greater than what would be required for thermoregulation.

Peter M. Brown (talk) 18:36, 12 September 2012 (UTC)

Thanks for the input, sorry I couldn't reply sooner. I realize the presence of positive allometry alone isn't evidence for sexual selection, and I agree the wording of this part of the article should be changed. It might clear things up if the sexual selection and thermoregulation paragraphs are switched. That way, the role of positive allometry in thermoregulation can be discussed, then its unusual steepness in Dimetrodon, corresponding to sexual selection, can be discussed. Smokeybjb (talk) 19:30, 14 September 2012 (UTC)

I have some reservations about the conclusion in this paper. A trait used in sexual display will almost always be strongly dimorphic. Particularly the sail, with it's long bony spines would have been costly to both produce and maintain. If (let's say) the males used it for establishing dominance or impressing females (or both), it would be no need for the females to produce the same sail, particularly as she would have to spend resources on eggs (costly in vertebrates and particularly so in amniotes). Similar display structures in males and females are either used in courtship display (like the fancy tailfeathers and whooping in cranes), non-sexual dominance display (like the very visible markings in many sea-birds competing for nest sites) or in species recognition. There seem to be some dimorphism in Dimetrodon, but not at all enough indicate the primary reason for the sail being used primarily for sexual display. I have no doubt the sail also served a social function, but such a large and costly structure is likely to primarily have served more basal functions like thermoregulation. I think a decent analogy would be the tusks in elephants, which are primarily used for feeding and defence, but also used for sexual display (between males).Petter Bøckman (talk) 07:58, 17 September 2012 (UTC)

Phylogenetic vs. Linnaean taxonomy

According to the article. "Today most paleontologists prefer a classification system called phylogenetic systematics over Linnean taxonomy." According to WP:WEASEL, words like "most" are generally weasel words, though not if they appear in the topic sentence of a paragraph with attribution supplied by the the rest of the paragraph. This is not the usage here. The only article I have encountered that actually reports such counts is Laurin and Anderson (2004), "Meaning of the Name Tetrapoda in the Scientific Literature", Figure 2c, where phylogeny outnumbers morphology 5 to 3; hardly an overwhelming dominance. I rather suspect that the ratio differs radically between paleontological subfields. Peter M. Brown (talk) 16:44, 10 September 2012 (UTC)

How about something along the lines of "Phylogenetic systematics is more often used"? It's certainly the case for most of vertebrate paleontology nowadays, even if other areas of paleontology might not have embraced the change. Even though the name "tetrapod" may not always be used in a formal phylogenetic way according to Laurin and Anderson (2004), it doesn't mean phylogenetics isn't the dominant classification system. Smokeybjb (talk) 18:56, 10 September 2012 (UTC)

There are two areas where phylogenetic classification is particularly prevalent: Dinos and Synapsids. While I have no doubt most workers on Dimetrodon is using phylogenetic classification, it is by no means "the most common". Laurin estimates ranked (Linnaean) systematics is about 10 times as common as rankless phylogenetic classification in general (Laurin M (2010): The subjective nature of Linnaean categories and its impact in evolutionary biology and biodiversity studies, Contributions to Zoology, vol 79, pp 131–146.) In my view, the correct sentence would be something along the line of "A common system of classifying in vertebrate palaentology is phylogenetic taxonomy, where ...". Reading the section in question, one might ask why a full outline of the Reptile-Sauropsid debate is doing in this article. I suggest dropping all of it as it really is a matter for the Synapsid and Sauropsid articles. Petter Bøckman (talk) 21:13, 10 September 2012 (UTC)

It's a big jump, Petter, from saying that phylogenetic classification is prevalent in the study of dinosaurs and synapsids to saying that it is common in the entire field of vertebrate paleontology—OK, palaeontology. That would include the palaeontology of fish, which is surely a huge field. Are you confident that the stronger statement is warranted? Peter M. Brown (talk) 23:33, 15 September 2012 (UTC)

The reptile clade

As the article Reptile notes in the last sentence of the subsection "Antediluvian monsters", the amniotes other than the mammals and the birds are the animals currently considered considered to be reptiles. Since this group is not a clade, it is jarring to encounter the phrase "the reptile clade" in the first paragraph of Dimetrodon#Evolutionary relationships. While authors like Modesto and Anderson (2004) have promoted the identification of Reptilia with a clade, Sauropsida in their case, the Dimetrodon article should explain what is meant before using the term in a nonstandard way. Is Sauropsida, defined by Toby White as consisting of all amniotes closer to snakes than to St. Patrick, the clade in question? Or is it, perhaps, the crown group of extant sauropsids, a clade that probably did not originate until somewhat after the very first sauropsids? Is it the sister clade of Mesosauridae or, alternatively, of the parareptiles? (See the cladograms in the Parareptilia article.) Peter M. Brown (talk) 23:42, 11 September 2012 (UTC)

There's no lack of definitions of Sauropsida, variously anchored in a number of living and extinct forms. A fairly complete summary is given by Modesto & Anderson. Their argument however is that the term is virtually unknown outside scientific circles, and that the term "Reptilia" should have priority. Using their logic, Reptiles would be the clade Sauropsida as most commonly understood (Snakes/St. Patric definition). I suppose the section was written right after the Modesto & Anderson article, when the PhyloCode crowd felt the new definition would soon take over. It has had very little traction though, so I think it would be best to use Reptilia for the traditional grade, and Sauropsida when one wish to refer to the Sauropsidan clade.

Why not just call Sauropsida what it is: The branch that include modern reptiles and the birds?

I have said above and will repeat here that the whole first section on evolutionary relationship in this article should be dropped. This is an article about Dimetrodon, not about higher classification of the amniotes. Petter Bøckman (talk) 07:32, 12 September 2012 (UTC)

I disagree, given the likely amount of confusion among the general public about what exactly Dimetrodon is, there is a need for explicit clarification in the article. Abyssal (talk) 10:49, 12 September 2012 (UTC)

Sure, I can see we need to mention that Dimetrodon is not a dinosaur and belong to a different branch of the tree, but the whole Sauropsida/Reptilia dispute should not go in this article. It only contributes to clutter up the basic point, without contributing to clarify where on the tree Dimetrodon belongs. Petter Bøckman (talk) 13:07, 12 September 2012 (UTC)

I'll try simplifying it if I can, but I agree with Abyssal that the confusion should be sorted out in this article. Dimetrodon is well known by the general public, making this a high-traffic article read by people who probably know very little about the animal's classification, and likely have the misconception that it's a reptile or even a dinosaur.

When I wrote that part of the article, I was intending the "reptile clade" to be Sauropsida, and was intending to use "reptiles" as a term for any non-synapsid amniote, even stemward of crown group Reptilia. I changed the wording to "the clade that includes reptiles" to avoid this ambiguity. Smokeybjb (talk) 19:36, 14 September 2012 (UTC)

The reptiles are the amniotes that are neither mammals nor birds. That includes Dimetrodon; this is not a misconception. Even non-mammalian therapsids are called "mammal-like reptiles" in recent work. The dimetrodons were not dinosaurs, of course, and please do whatever you can can to combat the popular impression that they were! Before they're anywhere near old enough to be looking at Wikipedia, 7-year-olds find dimetrodons in their dinosaur toy sets. Our hope lies in the 11-year-olds who will delight in correcting others if only we can get the word to them somehow. Peter M. Brown (talk) 20:31, 14 September 2012 (UTC)

Well said, but calling Dimetrodon a reptile is still inaccurate. T.S. Kemp might be a well-respected paleontologist who still uses the term "reptile" in the sense of an evolutionary grade, but, to use the expression loosely, he's part of the old school. Not every paleontologist might embrace phylogenetic taxonomy, but it is certainly the dominant view in this area of vertebrate paleontology. This article should reflect the consensus view of the subject, which means that calling Dimetrodon a reptile is misleading and inaccurate.[7] Smokeybjb (talk) 21:06, 14 September 2012 (UTC)

As Petter says, phylogenetic taxonomy is dominant in synapsid paleontology. That orientation is neutral, however, on the question whether Dimetrodon is a reptile. Petter also says that "it would be best to use Reptilia for the traditional grade". As I note above, the Reptile article says that the amniotes other than the mammals and the birds are those considered reptiles today; as amniotes, birds, and mammals are all clades, this is a fully phylogenetic characterization. Even the Dimetrodon article says, "Cope had obtained [Dimetrodon] fossils along with those of many other Permian reptiles from several collectors"; the "other" implies that Dimetrodon is a Permian reptile.

Whether you agree or not, consider the position of the general reader who comes to the article thinking that Dimetrodon is a reptile. In the lead, when the reader encounters the clause "Dimetrodon is more closely related to mammals than it is to any reptile," he or she may be somewhat taken aback: isn't Dimetrodon a reptile? This doesn't make sense. . . .

The lead currently does not provide a smooth reading experience.

Further down, the reader encounters the discussion of Cope's work, which reinforces the sense that Dimetrodon is a reptile, something that has not been denied. The fact that the work in which Cope described the genus is called "The Theromorphous Reptilia" adds to the impression, as does the fact that "In the Linnean system, Reptilia was ranked as a class and Dimetrodon was ranked as a genus within that class." You and I know that that the Linnaean system is not dominant in current synapsid studies, but the general reader may not.

I suggest that you define the sauropsids as the animals more closely related to living reptiles than to mammals and use this term consistently instead of "reptiles". No need to abandon neutrality in the usage of "reptile" as applied to Paleozoic amniotes.

Peter M. Brown (talk) 22:40, 14 September 2012 (UTC)

We shouldn't write for readers expectations, but for what is factual. It's not just my opinion that Dimetrodon is not a reptile, it is the (generally) accepted view, and sources can back that up (Angielczyk (2009) is one of them, explicitly stating that Dimetrodon is not a reptile). Cope's work describing Dimetrodon as a reptile is, I hope, taken by the reader as a historical interpretation and not the current view. Smokeybjb (talk) 23:30, 14 September 2012 (UTC)

"The reptiles are the amniotes that are neither mammals nor birds." That's one definition. There are others in wide use. It cannot be presented as a definitive statement without being biased. MMartyniuk (talk) 02:00, 15 September 2012 (UTC)

Yes, there are a number of definitions in wide use. Amniotes minus mammals and birds is one of them (Benton, Vertebrate Palaeontology, p. 33). I hope that, in this discussion, we can take that as given. As the purpose of Wikipedia is to provide information to nonspecialists who mean a variety of things by "reptile", a stipulation as to how the term is used in an article should be provided before the word appears in a sentence that would be false or absurd on one of the common meanings. This condition is not met in the Dimetrodon article as it stands.

Such a stipulation is awkward and totally unnecessary. The word word "reptile" does not have to be used. Instead of saying

In popular culture, Dimetrodon is often mistaken as a dinosaur. . . . However, Dimetrodon is more closely related to mammals than it is to any reptile, including dinosaurs. . . .

the article can say

In popular culture, Dimetrodon is often mistaken as a dinosaur. . . . However, Dimetrodon is more closely related to mammals than it is to any dinosaur. . . .

Petter Bøckman's suggestion, above, is the way to go: "Why not just call Sauropsida what it is: The branch that include modern reptiles and the birds?" There is no ambiguity in the phrase "modern reptile". Once Sauropsida is clearly defined, the term can be used consistently instead of Reptilia sensu Angielczyk.

Smokeybjb has written, "We shouldn't write for readers expectations". Surely, he doesn't mean what he seems to be saying. We write so that nonspecialists can read us comfortably and understand what we are saying. As any reading teacher can tell you, expectations are a huge part of successful reading. The fact that Angielczyk uses a word one way and Benton uses it another is irrelevant unless such usage is the matter under discussion. It isn't. The article is about Dimetrodon.

Peter M. Brown (talk) 15:22, 15 September 2012 (UTC)

What I mean to say is that this article shouldn't call Dimetrodon a reptile simply because a reader expects it to be a reptile. If it is to be called a reptile, it should be well supported. Since I don't think there's enough support to justify calling it a reptile, I don't think this article nor any other on Wikipedia should call it a reptile. Readers won't find this absurd since Dimetrodon probably isn't part of their image of what is and is not a reptile, and I doubt that teaching them it is not a reptile under modern uses of the word will send them into a fit of confusion. Furthermore, the issue of whether or not Dimetrodon is a reptile (in both the taxonomic and semantic sense) is vital for understanding what Dimetrodon really is. Smokeybjb (talk) 16:58, 15 September 2012 (UTC)

Responding to your points:

This article shouldn't call Dimetrodon a reptile.	Agreed. The term is too ambiguous.
I don't think this article or any other on Wikipedia should call it a reptile.	Agreed. The term is too ambiguous.
Readers won't find this absurd.	Our failure to call it a reptile? No, they'll probably not even notice it.
Dimetrodon probably isn't part of their image of what is and is not a reptile.	Disagree. Most people, unfortunately, think of Dimetrodon as a dinosaur and therefore a reptile.
I doubt that teaching them it is not a reptile under modern uses of the word will send them into a fit of confusion.	If we bring the matter up at all, though, we should make clear that only under some modern uses is it not a reptile.
The issue of whether Dimetrodon is a reptile is vital for understanding what Dimetrodon really is.	It is essential to communicate (1) that there is an ancient divergence with mammals on one side and dinosaurs and extant reptiles on the other and (2) that Dimetrodon falls on the mammal side. This can be expressed many ways. The ambiguous word "reptile" is best dispensed with as applied to Paleozoic animals, especially as "sauropsid" is available.

Peter M. Brown (talk) 19:41, 15 September 2012 (UTC)

Come on guys, this is starting to get silly. We all know the common understanding of the term "reptile" is that of a grade. Sure, there exists a few other definitions, but they are mostly restricted to specialist papers and are virtually unknown outside a small circle of vertebrate palaeontologists. What we need is to tell the reader that Dimetrodon belonged to a group of critters living well before the dinosaurs, and hailing from a quite different branch of the phylogenetic tree, the branch from which mammals eventually sprang. Meanwhile, "reptile" is a perfectly good descriptive term. Whether one wish to employ it as a formal systematic term or just as an informal descriptive term is a matter of taste, but as a term it is certainly not wrong. Petter Bøckman (talk) 19:45, 15 September 2012 (UTC)

Here's my suggestion for wording. This should cater to all:

Dimetrodon is often thought to be a dinosaur, but is in fact not.(ref) While a reptile in the vernacular sense, it belongs to a very different branch of the reptilian family tree. Dimetrodon and it's relatived belong to a group called synapsids, often called «mammal-like reptiles» - who eventually gave rize to mammals in late Triassic, while the dinosaurs belong to the other major branch, called Sauropsids. Dimetrodon was one of the early, sprawling forms, collectivly referred to as pelycosaurs, who were the most common large land animals in the early Permian, but were replaced by the more advanced and more mammal-like therapsids in the mid Permian,(ref) and Dimetrodon had died out 40 million years before the dinosaurs evolved.(ref)

Thus, while Dimetrodon and its relatives were generally reptile like and build and physiology, they are actually more closely related to mammals than to any living reptilian group.(ref) Because of the widely diverging branches being united under the term "reptile", it is common among researchers not to use the term, in stead using Synapsid for the whole branch of mammal-like reptiles and their mammal descendants, and Sauropsids for the branch containg all existing reptiles and the birds.(ref)

Petter Bøckman (talk) 20:22, 15 September 2012 (UTC)

I appreciate all the suggestions and I'm not trying to bicker, but I still don't entirely agree. The second part of Petter Bøckman's quote sounds good and would go far to clarify things, but I think the first part is putting undue weight on the popular conception of the word reptile and not enough on its established meaning in scientific literature (which is a phylogenetic meaning, like it or not). Saying that Dimetrodon "belongs to a very different branch of the reptilian family tree" implies to me that it is part of a reptile clade, since "family tree" invokes "phylogenetic tree". Here's how I'd modify the lead, keeping in mind that this article shouldn't go too deep into the definition of "reptile":

Dimetrodon is often mistaken as a dinosaur or as a contemporary of dinosaurs in popular culture, but it went extinct around 40 million years before the appearance of the first dinosaur in the Triassic period. Dimetrodon is thought to have been generally reptile-like in appearance and physiology, but it is actually more closely related to mammals than it is to any living reptilian group. Dimetrodon is often called a "mammal-like reptile" but is more properly termed a "basal synapsid"(ref) as most vertebrate paleontologists today place reptiles and mammals in separate evolutionary groups or clades called Synapsida and Sauropsida, respectively.

As it is phrased here, the placement of reptiles in Sauropsida doesn't mean reptiles = Saurospida. And there's no mention that Dimetrodon is not a reptile. Smokeybjb (talk) 20:52, 15 September 2012 (UTC)

True, the suggestion above do not say Sauropsida = reptiles. Sauropsida also contain birds (not reptiles in normal parlance) and depending on authors a number of extinct groups falling outside the crown group. Reptilia is not commonly understood as a clade. If you want to claim it is, you are forwarding an extraordinary claim and the burden of proof is on you. The "Dimetrodon is not a reptile" is only correct under a subset of definition of the term reptile, non of which are known outside very restricted circles, and not terribly relevant here anyway. We need to explain that 1) it was not a dinosaur, that it 2) was more closely related to mammals and 3) (bonus) that the term reptile has been dropped by many researcher (and why). The use of the term "reptile" in my suggestion is is likely to convey it had a sprawling gait, scaly skin (or scutes really, if we are to be exact), was ectotherm and laid leathery eggs, all of which is true as far as we know. Petter Bøckman (talk) 21:11, 15 September 2012 (UTC)

If we want to convey that Dimetrodon had a sprawling gait, scaly skin, was an ectotherm, and laid leathery eggs, it would be better to say that directly than to call it a reptile. I'm not trying to call Reptilia a clade, although I don't think the claim is that extraordinary, especially if Reptilia is taken to mean Sauropsida. But that's beside the point, and there's no mention of the reptile clade in the paragraph I suggested above. Smokeybjb (talk) 21:27, 15 September 2012 (UTC)

The anatomy of Dimetrodon is covered elsewhere, the effect i wanted was to remind the reader why this animal is confused with another reptilian group (the dinosaurs), hence the use of the term "reptile", and the discussion of that very term in the next section.

The only suggestion I have come across using Sauropsida as = Reptile is Modesto & Anderson, and they are even just suggesting such use. I haven't seen their suggestion have much traction outside PhyloCode circles, and let's face it, PhyloCoders are not the majority of scientist using the term "reptile", not to mention among the general public. In the rest of Wikipedia, the term reptile is taken to mean reptile in the common sense, and Sauropsids are called just that, Sauropsids. It is a sensible use of the terms both from a scientific and a communication POW, and I strongly suggest we stick to it. Petter Bøckman (talk) 21:45, 15 September 2012 (UTC)

This argument is getting drawn out. Many scientists use "reptile," but the subset of scientists who study and publish papers about synapsids do not take "reptile" to mean all amniotes minus mammals minus birds. I can't give you many sources that say what I am saying because most scientific papers pertaining to Dimetrodon nowadays have moved beyond that issue, and simply don't call Dimetrodon or any other synapsid a reptile. I think we can both agree on that. Getting back on topic, what's still at issue in this article is the first paragraph of the "Evolutionary relationships" section. Here it is, with mentions of reptiles underlined:

Dimetrodon is an early member of a group called synapsids, which include mammals and many of their extinct relatives. It is often mistaken as a dinosaur in popular culture, despite having become extinct around 40 million years (Ma) before the first dinosaurs appeared. As a synapsid, Dimetrodon is more closely related to mammals than it is to dinosaurs or any other reptile. In the late nineteenth and early twentieth centuries, most paleontologists called Dimetrodon a reptile in accordance with Linnean taxonomy. In the Linnean system, Reptilia was ranked as a class and Dimetrodon was ranked as a genus within that class. Although a close relationship between Dimetrodon and mammals was recognized at the time, mammals belonged to their own separate class and thus Dimetrodon was a "mammal-like reptile". Paleontologists thought that reptiles like Dimetrodon (note: this isn't saying that Dimetrodon is still a reptile) evolved into mammals in a reptile-to-mammal transition. More recently, phylogenetic taxonomy has become a common system of classification in vertebrate paleontology whereby groups are defined by shared common ancestors. Reptiles and mammals have been placed into clades, which are groups that include a common evolutionary ancestor and all of its descendants. Under phylogenetic systematics, the descendants of the last common ancestor of Dimetrodon and all living reptiles must include all living mammals because Dimetrodon is now known to be more closely related to mammals than it is to any reptile. (note: I'm hoping readers get that reptile is being used in the phylogenetic sense). To avoid mammals being in the clade that includes reptiles, neither Dimetrodon nor any other "mammal-like reptile" can be considered part of that clade. Descendants of the last common ancestor of mammals and reptiles (which appeared around 310 Ma in the Late Carboniferous) are therefore split into two clades: Synapsida, which includes Dimetrodon and mammals, and Sauropsida, which includes living reptiles and all extinct reptiles more closely related to them than to mammals.

Earlier I rephrased "To avoid mammals being in the reptile clade..." to "To avoid mammals being in the clade that includes reptiles...", avoiding the problem of implying a clade called Reptilia. Now, hopefully, there is no implication of Reptilia as a clade. The word "reptile" isn't being thrown around without careful explanation. So what remains a problem, specifically, in this article? Smokeybjb (talk) 22:02, 15 September 2012 (UTC)

I believe my version says effectively the same thing as what you quoted here, except is was shorter, more to the point and written in a style more easily digested by a layman. Experts don't need to learn abut all this, and the many points of clades, reptiles vs. ssauropsids etc is just obscuring the main point that Dimetrodon was not a dinosaur. Petter Bøckman (talk) 06:55, 16 September 2012 (UTC)

The problem I have is that your version is not saying the same thing, but is de-emphasizing phylogenetics and discussing evolution in an oversimplified way. I don't think the main point of an "Evolutionary relationships" section should be that Dimetrodon is not a dinosaur, but that Dimetorodon is a synapsid with a specific place on the phylogenetic tree. Perhaps the section should be rephrased "Phylogenetics". As for the section being too confusing for laypeople, I'm looking at WP:TECHNICAL, which emphasizes: 1) an accessible lead section; 2) prose understandable by general readers, knowledgeable readers, and expert readers; and 3) putting the most understandable parts of the article up front. The lead of this article is accessible to all three groups of readers and does a fine job explaining that Dimetrodon is not a dinosaur. The "Evolutionary relationships" section goes into greater detail and necessarily requires some technical language that might confuse general readers. However, this section is put near the end of the article and general readers can skip it if they are not interested in the intricacies of phylogenetics. WP:TECHNICAL says that increasing understandability "should be done without reducing the value to readers with more technical background", and I think that your shortening and simplifying of the section unfortunately reduces its value. Smokeybjb (talk) 15:58, 16 September 2012 (UTC)

Most people think of Dimetrodon as a dinosaur. Wikipedia should do its part in informing people that it was not. I concur with Smokeybjb as to the central significance of phylogenetics, as the point goes well beyond mere taxonomy; Dimetrodon is on our side of the family tree, not the dinosaur side, and it was the terror of its time. In those days, animals more closely related to the dinosaurs—Captorhinus for example—were merely prey for our relatives, including the dimetrodons.

How to make the point? The temporal gap between Dimetrodon and the dinosaurs is relevant, but much more important IMO is the phylogenetic fact that there is a fundamental division among the fully land-adapted vertebrates, one going back over 300 million years; we and Dimetrodon are on one side while the dinosaurs are on the other. The synapsid/sauropsid division is crucial background for understanding the importance of the fact that Dimetrodon was not a dinosaur.

The exposition must therefore start with the fundamental phylogenetic split. Merely noting that Dimetrodon was something called a synapsid and that it predates the dinosaurs, without even mentioning that the dinosaurs were not synapsids, falls seriously short. And introducing "reptiles", so far from being "vital", simply makes for unnecessarily difficult reading: the reader who comes to the article thinking that Dimetrodon was a reptile can only be puzzled by the statement (in the lead )," Dimetrodon is more closely related to mammals than it is to any reptile." More closely to mammals than to reptiles like other sphenacodontids? Reference to "the clade that includes reptiles" will be equally mysterious: doesn't each of the clades contain some reptiles?

Confusion will be forestalled if it is first explained that, as the term "reptile" is used by scientists, all reptiles are sauropsids. A further question, then, is whether this is a responsible thing to say. From Vertebrate Paleontology (Romer) to Vertebrate PalAeontology (Benton), nonmammalian synapsids have been considered reptiles. Martin Martyniuk correctly notes that theirs is only one of the meanings in wide use but it nevertheless is one and it cannot be dismissed out of hand. Under the Modesto/Anderson alternative, all reptiles will be sauropsids; as Petter Bøckman has noted, however, this has not seen widespread adoption. Perhaps Sauropsida#Cladistics and the Sauropsida can be faulted for denying outright that Reptilia is a clade, but to affirm that it is one would be no more acceptable.

Peter M. Brown (talk) 19:26, 16 September 2012 (UTC)

Alright, I will try to rephrase the lead so that "sauropsid" rather than "reptile" is used from the very start. However, saying that all reptiles are sauropsids "has not seen widespread adoption" is false. You seem to be calling an idea "widespread" because it appears in a few textbooks. Romer and Benton's books are of course very well respected, but Romer's was last published before phylogenetics was widely accepted and Benton is somewhat of a holdover from those pre-cladistic days. When you look at scientific literature as a whole -which, unlike a single textbook, is representative of scientific consensus- all reptiles are sauropsids. Given how widespread the all-reptiles-are-sauropsids notion is, I can dismiss the reptiles-include-synapsids meaning because it is the minority view on a topic (large-scale amniote taxonomy) that is beyond the scope of an article about the genus Dimetrodon. Smokeybjb (talk) 21:36, 16 September 2012 (UTC)

Update: I intended to remove the phrase "Dimetrodon is more closely related to mammals than it is to any reptile" in an earlier edit. I just removed it now. The next paragraph describes the relationship of Dimetrodon to mammals and reptiles in the way that has been suggested here. Smokeybjb (talk) 21:51, 16 September 2012 (UTC)

The reptile clade, part II

This is getting longish, splitting it up.

The point about this section being a bit down and therefore can be a bit more technical is a good one. With that, we can assume the reader get the point about Dimetrodon not being a dinosaur fairly quickly, and can elaborate more on the shift from the pelycosaur-dominated early Permian to the therapsid-dominated late Permian, and the phylogenetic position of Dimetrodon within the pelycosaurs and relative to the therapsids.

The blanket statement that synapsids are not reptile is not universally correct, and should be avoided. The statement that reptiles as used by scientists are the Sauropsids only is false, and should be avoided. The correct statement should be that a small subset of scientists, being the majority of vertebrate palaeontologists and a few herpetologists uses reptile only for Sauropsids (or a subset thereof). Again, this is well and truly beside the point of this article, and while it should be mentioned, it is better to avoid using reptile in a non-standard fashion in this article.

Smokeybjb's pint that the term "reptile" should not be thrown around without careful explanation is curious. For the general reader, "reptile" is the only therm they are likely to be familiar with. It is "sauropsid" and "synapsid" that need carefull explanation. Petter Bøckman (talk) 07:38, 17 September 2012 (UTC)

It is now agreed, I think, that a significant number of vertebrate paleontologists do include some synapsids among the reptiles. If so, doesn't the use of the phrase "true reptiles" in the lead involve undue weight? Are synapsid reptiles false reptiles? Peter M. Brown (talk) 00:54, 18 September 2012 (UTC)

How may vertebrate paleontologists aside from Romer, Benton, Kemp, and a few others actually consider synapsids reptiles? Look at any recent paper on early amniotes (that includes species descriptions, phylogenetic analyses, etc.) and I bet most would use reptiles in the restricted sense. To get an idea, if you do a Google Scholar search recent articles using terms like "Synapsida" or "Sphenacodontia" (say, since 2000),[8][9] you'll find hundreds of papers that don't call these animals reptiles. I wouldn't consider that a small subset. Anyway, for the sake of reaching an agreement with wording I moved the explanation of synapsids and sauropsids closer to the start of the lead so that the term "true reptiles" could be replaced with "sauropsids". Smokeybjb (talk) 01:31, 18 September 2012 (UTC)

Vertebrate palaeontologists are a subset of palaeontologists in general (most are micro-palaeontologists working with petroleum-related stratigraphy anyway), which again is a small subset of zoologists in general, so yeah, they are a small subset. I appreciate you coming into this from a vert.pal. perspective Smokey, but the term "reptile" is an old term in common use, both in many scientific and lay circles, and a subset of the vert.pal. people do not have any sole custody of how to interpret it. Wikipedia at large uses reptile in the traditional sense, and it would be stupid not to do so here too. The upheaval in systematics really have left us in a situation where most authors simply avoid using the term at all, so claiming one or the other is a bit besides the point (this is a general trend, not specific to "reptile".)

All we really need to do in this article is explaining the phylogenetic position of the Dimetrodon, and how it is related to dinosaurs and mammals respectively. Relevant topics is the sauropsid/synapsid or diapsid/synapsid splitt and the replacement of pelycosaurs by therapsids by the mid permian. It is fully possible to explain this satisfactory in both traditional (Romerian) and phylogenetic (Gautierian) terms. The only real challenge I see is explaining this in fairly neutral terms, but I think it is doable. The debate on what authors uses reptiles in such and such way is extremely marginal, and in my view do not belong here other than in a small comment like the one I suggested above. Petter Bøckman (talk) 07:41, 18 September 2012 (UTC)

Why is neutrality particularly challenging at this point? What bias is left to eliminate after the edits we've made in the course of the last two weeks? Remaining on Petter's list is an account of the replacement of pelycosaurs by therapsids, which will require presentation of both the competitive and the opportunistic theories of replacement, but both can be explained using the neutral terms "pelycosaur" and "therapsid". Peter M. Brown (talk) 22:32, 18 September 2012 (UTC)

To weigh in, I'm satisfied with the recent edits and I think the distinctions between phylogenetic and traditional classifications are now worded very well. As for the pelycosaur-therapsid replacement, I think it would be good to mention in the lead but it's probably out of the scope of this article to talk about different theories. It would be better to just say in this article that there was a faunal replacement after Dimetrodon, but not go into why. Smokeybjb (talk) 23:43, 19 September 2012 (UTC)

Sorry to have been offline for a while. Work, family life and all that... The article is better now, with the new heading, the content works better. I agree with Smokey that we don't need to go into the details of the pelycosaur-therapsid replacement. It is only relevant here in connection with the timing of Dimetrodon relative to dinosaurs. With that said, I still think a few of the longer sections should be split up into subsections to aid in reading. Petter Bøckman (talk) 21:23, 21 September 2012 (UTC)

Angielczyk

The Dimetrodon article says that "mammal-like reptiles" are termed "non-mammalian synapsids" in phylogenetic nomenclature, citing a paper by Angielczyk. This paper is largely concerned with promoting "tree thinking", i.e. conceptualizing the history of sarcopterygians from a phylogenetic standpoint. Another emphasis in the paper is Angielczyk's marked contempt for the phrase "mammal-like reptiles" which he characterizes as "outdated". Angielczyk makes the historical claim that increasing attention to phylogeny has resulted in what he sees as the abandonment of this "outdated" phrase. The claim in the Dimetrodon article is not historical, however; it seems to be saying that there is a standard called "phylogenetic nomenclature" according to which "non-mammalian synapsid" is an acceptable designation but "mammal-like reptile" is not. I do not see such a standard identified in Angielczyk's article. The PhyloCode comes to mind; Angielczyk does mention it briefly, but he does not claim that it favors "non-mammalian synapsid" over "mammal-like reptile". Indeed, it does not: PhyloCode Article 6.1 says that the code only regulates "established" names and Article 7.2 makes clear that only clade names can be established. "Non-mammalian synapsid" is not a clade name and so does not fall under the code.

As Petter Bøckman has argued at length above, "reptile" is a name often used for the paraphyletic group consisting of all amniotes other than mammals and birds. He likes to cite Colin Tudge on the matter; another source is palaeos.com, which is widely used as a reliable source in Wikipedia articles on paleontology. Among reptiles so conceived, some—those that are synapsids—have long been recognized as more mammal-like than the others.

Peter M. Brown (talk) 21:57, 30 September 2012 (UTC)

I don't quite get what you're trying to argue about Angielczyk. He is saying quite clearly that "mammal-like reptile" is not an acceptable term in phylogenetic standards. Here's a quote:

"In the past, non-mammalian synapsids were often colloquially referred to as mammal-like reptiles. They were 'mammal-like' because paleontologists understood that they were related to mammals and provided insight into the latter group’s evolution, but they were 'reptiles' because they lacked key characters that defined mammals, such as a single jaw bone or three middle ear bones. Examining the phylogeny in Fig. 4b shows why this terminology has been abandoned by scientists as tree thinking has become common and taxonomic groups have come to be defined by patterns of shared ancestry."

"Patterns of shared ancestry", "tree thinking", "phylogeny": all these terms imply that Angielczyk is speaking of phylogenetics when he says that "non-mammalian synapsid" is correct and "mammal-like reptile" is incorrect. Whether you like it or not, Dimetrodon cannot be called a reptile without a lengthy explanation that "reptile" is being used in the specific sense of a paraphyletic group including all amniotes except birds and mammals (which is not an obvious definition when you consider that many sources use "reptile" as all amniotes except birds and synapsids, or as another name for Sauropsida, or as crown-group reptiles). We've been over this before, so please stop trying to make the article say that Dimetrodon is a mammal-like reptile. Smokeybjb (talk) 23:36, 30 September 2012 (UTC)

Yes, there are many senses of "reptile", spelled out nicely in the Reptile article. "The amniotes exclusive of mammals and birds" is one, and I just stated it in seven words. If a more lengthy explanation is needed, the historical importance of the mammal-like reptile characterization requires that it be provided. In the article as it stands, the discussion in Dimetrodon#Phylogenetic classification may be adequate, though it does not provide a phylogenetic definition of the reptiles.

The passage you quote is precisely the historical claim I wrote of. Is the statement that "taxonomic groups have come to be defined by patterns of shared ancestry" what you are referring to as "phylogenetic standards"? Since the mammal-like reptiles and the nonmammalian synapsids are precisely the same group, their patterns of shared ancestry are identical; this can provide no reason for preferring the one locution over the other. "Synapsid" and "mammal" are clades, so "non-mammalian synapsid" is a phylogenetic characterization. "Amniote", "mammal" and "bird" are clades, so a definition of "reptile" in terms of the three is also fully phylogenetic. Angielczyk dislikes the phrase "mammal-like reptile" but he knows better than to reject the phrase by appeal to some sort of phylogenetic standards. Peter M. Brown (talk) 01:01, 1 October 2012 (UTC)

Don't get me wrong. I won't dispute the point that defining these animals as a kind of synapsid is more conducive to understanding than is defining them as a kind of reptile. I rather suspect that it better accords with productive research directions. It may well be that the traditional definition of "reptile" is, in an important sense, outdated. All I do dispute is that phylogenetic standards or phylogenetic nomenclature has an important bearing on the matter. Angielczyk is pushing a way of thinking, which is not the same thing as a standard or a nomenclatural code. Peter M. Brown (talk) 22:18, 1 October 2012 (UTC)

Now that neither "phylogenetic nomenclature" nor "phylogenetic standard" is present in the article, we can end this discussion. Peter M. Brown (talk) 13:31, 2 October 2012 (UTC)

Olson on paleoecology

As the article notes, Olson distinguishes three types of community.

The Type I community is described accurately in the Paleoecology section. However, if the characterization of Dimetrodon in the lead as "feeding mostly on aquatic animals like large fish and amphibians" is based on Olson's discussion and flow diagram of Type I communities, support is inadequate, and I see no other source in the article. Though his Figure 1 does show the aquatic vertebrates as the food source for the terrestrial vertebrates taken as a group, it is silent as to how much of any particular genus's food comes directly from the aquatic rather than the terrestrial realm. It is consistent with Olson's discussion for Dimetrodon to have relied for its sustenance mostly on other terrestrial vertebrates such as Edaphosaurus and Seymouria.

Dimetrodon is mentioned in the discussion both of Type II and Type III communities, which leaves the impression that some animals in this genus were members of communities of these types. Olson is explicit, however, that "The first definitely recognized occurrence of the Type II community is in the very early part of the late Permian", while "Type III has been specifically identified only in the Kazanian", in the Middle Permian. Neither can involve Dimetrodon, as the genus was limited to the Early Permian.

In the discussion of the Type III ecosystem, the article explicitly includes Edaphosaurus, though it is unknown from the Middle Permian. It also asserts that "most of the diet of Dimetrodon probably still came from large aquatic animals", though Olson's paper does not say that aquatic animals were ever its primary food.

Peter M. Brown (talk) 21:13, 20 September 2012 (UTC)

Unless it hunted in a way similar to Spinosaurus, I have difficulty seeing Dimetrodon hunting in water. Are there any newer articles on this? Petter Bøckman (talk) 21:29, 21 September 2012 (UTC)

In my mind, feeding on aquatic animals doesn't mean that Dimetrodon was an aquatic predator, but rather a riverside hunter. Dimetrodon is often shown taking on Xenacanthus: paleoartist Julius Csotonyi portrays it here and Bakker even illustrates it here, although he doesn't have it looking very competent in the end. But, I will go back to reread Olson's article and correct the issues that have been mentioned. Smokeybjb (talk) 22:50, 21 September 2012 (UTC)

More specifically, Bakker depicts Dimetrodon as unfamiliar with the likes of Xenacanthus. This would be consistent with the thesis that Dimetrodon's experience was mostly limited to terrestrial prey. Peter M. Brown (talk) 00:43, 22 September 2012 (UTC)

I just revised the paragraph on Olson's interpretations, keeping some information about Type II and III ecosystems that I think is still relevant. Sorry this wasn't done sooner, but I haven't found much time to edit lately. I'm hoping to resume the GA review, so please tell if you think there are any more problems with the article. Smokeybjb (talk) 00:40, 29 September 2012 (UTC)

I rather disagree about the inclusion of Type II and III ecosystems; this is an article about Dimetrodon, which did not participate in either. If you must discuss all three, preserving Olson's numbering of his types is pointless and confusing; better to be chronological, writing of Early, Middle, and Late Permian ecosystems in that order.

Olson did not claim, at least in the cited paper, that the Type III ecosystem supported the diversity of Late Permian therapsids. On the contrary, "Type III has been specifically identified only in the Kazanian of the Russian Permian in this study."

Dinocephalians are not known from the Late Permian or Early Triassic. Are you sure that any dicynodonts from these epochs were large? They certainly became big in the Middle Triassic, but the Permian Robertia, for example, was only 20 cm long. The Olson paper cannot be used a source, here, as it does not specifically mention either group. Therocephalians are mentioned only in the classification in the appendix, providing no data on their size prior to the Middle Triassic.

In the sentence beginning "However, insects" the word "However" indicates a contrast between what comes before and what comes after. Before, though, the text says that insects fed on land plants; afterwards, it says that Captorhinus fed on insects. Where is the contrast?

Peter M. Brown (talk) 15:34, 29 September 2012 (UTC)

Oops, I think I got Type II and III ecosystems mixed up: Olson said therapsids belonged to Type II and that Type III was supported by invertebrate herbivores. I took your advice and removed any mention of Types II and III. The "However" was meant to show that insects were present in the Type I community of the Red Beds even if they were a characteristic of Type III communities (which I wrongly stated as Type II). In any case, the contrast is no longer needed since I removed the lines about other community types. I was drifting from the source when I wrote about therapsids. There were some large Permian dicynodonts (Aulacephalodon, for example) and large therocephalians (scylacosaurids and akidnognathids), but since none of this is mentioned in Olson's paper and it's not very relevant to Dimetrodon, I took it out of the article. Smokeybjb (talk) 17:46, 29 September 2012 (UTC)

Dimetrodon kept "ear-jaw to ground" ??

Dimetrodon used the bottom back of its jaw to hear:

"In some therapsids, the angular, a bone located next to the articular, has a "reflected lamina," or bent plate, that looks like it might have served to support a membrane (tympanum) to detect vibrations. These vibrations were picked up by an arm of the articular bone that touched the tympanum (the retroarticular process), then passed through the jaw joint to the quadrate of the upper jaw, and from there, to the stapes. As the dentary increased in size, the articular and quadrate became smaller and less tightly attached to lower and upper jaw, respectively. As a result, these two bones were better able to transmit sound. The articular is known as the malleus in mammals, and it contacts the mammalian tympanic membrane its manubrium (the old retroarticular process). The reflected lamina of the angular forms the ectotympanic bone of mammals, a bony ring that supports the tympanic membrane. The therapsid quadrate becomes the incus, which still sits between malleus (articular) and stapes and transmits vibrations between them. As was certainly the case in the case of therapsids, movement of the stapes transmits sound to the inner ear, where it is turned into nervous impulses and sent to the brain."

http://animaldiversity.ummz.umich.edu/collections/mammal_anatomy/jaws_and_ears/

Why would an animal begin employing its jaw to hear? Beginning about 300Ma, early "sail-back" pelycosaurs, like Dimetrodon, were evidently sunning themselves in morning light, in order to accelerate their metabolism. Ipso facto, they were sunning themselves on exposed rocky outcrops, above and beyond vegetation in valleys below. Plausibly, whilst they lay sleepily sunning themselves, they rested their heads on the ground, between their paws. With their jaws mated flatly to the ground, low-frequency sounds, transmitted through bedrock, could have been heard. Dimetrodon may have been listening for the "seismic vibrations" of (say) huge herds of heavy herbivorous Caseidae thundering through the foliage beneath the (primitive) tree canopy cover. Imaginatively, Dimetrodons may have been laying about, head to the north, sunning themselves in the early mornings, on the norther flanks, of the Variscan mountains; unseen, in the valleys below, huge herds of herbivores ambled about, pounding the ground with their weight, and "seismically alerting" half-sleeping Dimetrodons on the ridges above -- who then jumped up, and waddled off quickly in the direction of the sounds, to investigate. Once the bottom back of the jawbone began to be employed, to transmit sound, up through the jaw joint, and into the ear; then the subsequent separation, miniaturization, and specialization, of the bones involved (angular & articulate --> tympanic collar & malleus, quadrate --> incus), becomes easily explicable, by conventional evolutionary gradualism. 66.235.38.214 (talk) 10:16, 23 October 2012 (UTC)

Any number of reptiles "hear" with their jawbone, particularly snakes who lack a tympanic membrane. Heck, even we mammals will pick up sound through the jawbone if we put it to the ground (try, it's a blast!). The above scenario is quite possible, if somewhat unencyplopedicly written. Petter Bøckman (talk) 12:55, 23 October 2012 (UTC)

The long quotation from the Animal Diversity Web says nothing about Dimetrodon as it is concerned only with therapsids. Dimetrodon was not a therapsid. Peter Brown (talk) 13:20, 23 October 2012 (UTC)

Dimetrodon was related to therapsids, yes? Both employed the bottom back of their jaws in hearing. Inexpertly, from "pelycosaurs through therapsids", even from c.300Ma, jaw bones began to be employed for hearing. The following Sci-Am article seemingly suggests, that early mammals (c.125Ma) did detect "sound through the ground":

http://www.scientificamerican.com/article.cfm?id=fossil-reveals-ear-evolution-in-action

Seemingly, "ground sound" detection was employed, from the first sail-back pelycosaurs c.300Ma, with gradually increasing specialization, until the evolution of full-fledged modern mammalian ears c.200Ma (e.g. Hadrocodium). i don't perceive any non-gradual, sudden, "quantum leaps" required to explain the evolution of the mammalian ear; the modern mammalian "bone chain" (hammer, anvil, stirrup) is a derived & degenerated & specialized remnant of the ancient jaw joint (which has separated off from the jaw & skull); the hammer-anvil joint is the relic remnant of the ancient proto-mammal jaw-joint; between our ears and jaws, modern humans retain the ancient "double jaw joint" of Triassic (?) proto-mammals.66.235.38.214 (talk) 21:47, 23 October 2012 (UTC)

Crocodylians and I think snakes also hear with their jaws. Regardless, this information should be represented on Wikipedia, but not in this article unless something can be found that discusses it explicitly for this genus. – Maky ^« talk » 22:17, 23 October 2012 (UTC)

Mammal Whiskers evolved with the first Therians c.150Ma; perhaps the removal, of "jaw ears", upwards towards the top of the head, in modern mammals, reflects whiskers being employed to detect ground vibrations, with the ears specializing for aerial sounds? If so, then i would predict, that Monotremes, lacking whiskers, still have "ground sound detecting jaw ears"... according to that article, "The external opening of the [Monotreme] ear still lies at the base of the jaw". Uncritically accepted, Therian whiskers do correlate with upwards removal of ears towards the top of the head, a coincidence which could possibly be meaningful. 66.235.38.214 (talk) 22:28, 23 October 2012 (UTC)

Again, what does this have to do specifically with Dimetrodon (per the sources)? I suggest taking this discussion to the appropriate talk page. – Maky ^« talk » 22:41, 23 October 2012 (UTC)

What point is there in taking it to any talk page? This is pure OR. Per WP:TPG, "Article talk pages should not be used by editors as platforms for their personal views on a subject." The only source 66.235.38.214 has cited adds some details about the evolution of the mammalian auditory ossicles from jaw-joint bones; it provides no support whatever for his "sound from the ground" thesis. (If there was a mandibular tympanum, as some writers have held, jaw bones would have received sound from the air.) Peter Brown (talk) 02:53, 24 October 2012 (UTC)

Monotreme ears are "inefficient for reception of high-frequency airborne vibrations but well suited for bone-conducted hearing":

http://www.nature.com/nature/journal/v377/n6545/abs/377141a0.html

what is non-aerial, bone-conducted hearing, if not a "ground sound" seismic sensor? The above-cited article seems to point towards that general direction; something for those most knowledgeable to watch for, perhaps; and if/when warranted, add to the article. Therapsids, generally; and Dimetrodons, specifically; are well worthy of discussion.66.235.38.214 (talk) 06:54, 24 October 2012 (UTC)

Much later, Yanocondon from c.125Ma had low-lying ears, for seismically sensing sounds from the ground; they were plausibly burrowers. Inexpertly, popular portrayals of precursors to mammals (e.g. Before the Dinosaurs, Walking with Dinosaurs) emphasize burrowing behaviors. Burrowers might benefit from "seismic sensors" capable of perceiving "earth shaking" predators pounding around above. Is there any evidence, that earlier Permian period reptiles were burrowers too?

http://www.scientificamerican.com/article.cfm?id=fossil-reveals-ear-evolution-in-action

66.235.38.214 (talk) 07:37, 24 October 2012 (UTC)

The footfalls of humans can be detected at ~1km, and those of elephants at perhaps over ~30km. "Ground sound" seismic sensors would plausibly have enabled early sail-back reptiles, like Dimetrodon, to sense (large) prey items at long, over-the-horizon distances:

http://physiologyonline.physiology.org/content/22/4/287.full

"Ground sound" seismic sensing, as explanation for retasking jawbones (from the feeding apparatus!) into the hearing system, seems plausible; perhaps somebody "in the field" knows something, or could keep an eye out in the literature; and update the Wiki article with appropriate, pertinent information? 66.235.38.214 (talk) 07:51, 24 October 2012 (UTC)

For purposes of pleasure in pursuing paleontology, c.300Ma, earth days were only about 23 hours long, i.e. earth years were about 380 x 23 hour days long (extra fortnight per year). Ipso facto, c.150Ma, as modern mammals were differentiating from monotremes, years were about 373 x 23.5 hour days long (extra week per year). 66.235.38.214 (talk) 08:16, 24 October 2012 (UTC)

I certainly can no longer complain of a shortage of references. And I do apologize for my dismissive tone. Nevertheless, you run afoul, if not of WP:ORIGINAL, then of WP:SYNTHESIS: "Do not combine material from multiple sources to reach or imply a conclusion not explicitly stated by any of the sources." If you contend that this is not what you are doing, you are invited to ask for advice at the No Original Research Noticeboard "regarding material that might be original research or original synthesis." To me, though, the matter is pretty clear. Maky, do you agree? If so, we are both experienced and respected enough in matters Wikipedian that it would be irresponsible of 66.235.38.214 to proceed, on any talk page, without obtaining an opinion. Peter Brown (talk) 20:44, 24 October 2012 (UTC)

"Original research" is defined as "advancing a position"; i'm merely citing sources, and seeking to discuss Dimetrodons, on the talk page, for purposes of potentially improving the article page, which i have not edited. For example, discussion of the sociality, or lack thereof, of Dimetrodons, would seemingly be relevant, pertinent, and improve the article, which currently makes no mention, of the social behavior, of the animals. 66.235.38.214 (talk) 12:53, 25 October 2012 (UTC)

There is no evidence these animals were social at all, as far as I know. If there were, it would likely be published at some point and we could then discuss it in the article. Right now, discussing the possibility of something based on nothing but pure speculation would give the false impression that there is some reason to think these animals were social, which there isn't. Sort of like discussing the effect their pink spots would have had on camouflage, if they had pink spots, which we have no way of knowing. MMartyniuk (talk) 16:09, 25 October 2012 (UTC)

66.235.38.214 denies that a position is being advanced. What then is the point of bringing in crocodylians, snakes, therians, monotremes, and Yanoconodon? I thought that the intent was to suggest homologies that would tell us something about Dimetrodon. This would be advancing a position, though. Reliable sources that attribute traits to these various amniotes are of no use in a Wikipedia article about Dimetrodon unless they also maintain that Dimetrodon shared these the traits homologously. None of the sources that have been cited do so. Peter Brown (talk) 18:16, 25 October 2012 (UTC)

Not a direct ancestor to any mammal?

The article states "it is not a direct ancestor of any mammals". Aren't the pelycosaurs in the same line as all mammals? --RisingSunWiki 03:26, 29 December 2013 (UTC)

How does that make this particular genus an ancestor? FunkMonk (talk) 03:34, 29 December 2013 (UTC)

Okay, I understand what you mean now that I've done some more research. So which genus of sphenacodontia is the ancestor of mammals? And how do scientists know that dimetridon is not the ancestral genus? Most web pages claim that dimetridon isn't the common ancestor, but how is that known for sure? --RisingSunWiki 14:43, 29 December 2013 (UTC)

Among other things, we (as in the scientific community) can not be sure which genus/species of sphenacodontid is the ancestor of mammals until we have discovered and identified literally all the species and genera of sphenacodontids that ever lived, and analyzed them. That, and there were several genera of sphenacodontid running around during Dimetrodon's time, who's to say that Dimetrodon, and not, say, Varanosaurus or Ophiacodon, was, specifically, the "ancestor of mammals"? And having said that, Dimetrodon is probably not an ancestor of mammals because it is a very specialized genus of sphenacodontid.

Having said that, too, this talkpage is for discussing how to improve the article, and is not a forum to determine whether or not Dimetrodon is or is not the "direct ancestor of mammals."--Mr Fink (talk) 17:41, 29 December 2013 (UTC)

This article does a good job explaining why we can't ever be sure that a fossil species is directly ancestral to some group, and that all that we can say is that it and that group share a common ancestor. Dimetrodon may be very close to the line that leads to mammals, but it can't be said to be on that line. In any case, most recent phylogenetic analyses find the whole of Sphenacodontidae to be a sister group of Therapsida (the group that includes mammals) and Dimetrodon to be one of the most deeply nested taxa within Sphenacodontidae, so Dimetrodon couldn't possibly be a direct ancestor of mammals. Smokeybjb (talk) 21:52, 29 December 2013 (UTC)

With all the caveats posted by FunkMunk and Smokeybjb above, Ophiacodon is probably closer to the line leading to the therapsids (and thus to mammals). The article could perhaps mention that while Dinetrodon belongs to the branch that gave rise to the therapsids, it is likely not the genus from which they evolved, an "uncle" rather than a "father". There's a small critter name Nikkasaurus that seems to be transitional. Petter Bøckman (talk) 09:51, 30 December 2013 (UTC)

Dimetrodon has unique characteristics (called synapomorphies) that are unique to itself and not other sphenacodonts or other synapsids closer related to mammals. These synapomorphies include both the sail and other more subtle features of the skeleton. Because Dimetrodon has a sail etc., and other sphenacodonts and mammals do not, it is more likely to assume that these unique features died out with Dimetrodon, rather than assume that all of them were lost to evolution as Dimetrodon evolved into other sphenacodonts and then finally mammals. It is more likely that other sphenacodonts with fewer of these synapomorphies are closer to the actual ancestors of mammals. MMartyniuk (talk) 11:16, 30 December 2013 (UTC)

Okay, thanks everyone, I understand this issue better now. Although, quite honestly, there is a part of me that's kind of dissapointed that Dimetrodon didn't turn out to be my ancestor :-( RisingSunWiki 13:27, 30 December 2013 (UTC)

"We can pick our friends, but we can't pick our family."--Mr Fink (talk) 16:11, 30 December 2013 (UTC)

List of Dimetrodon species

It seems a bit odd that List of Dimetrodon species is separate, when one would want to find all info about the animal here. This article isn't even close to the split limit (which is 100,000 bytes) at 55,000 bytes. It seems Psittacosaurus was used as template, but that is a old FA (from 2006), from then the standards were different, and the list has now been merged back. Any thoughts, Smokeybjb? FunkMonk (talk) 15:02, 21 December 2015 (UTC)

Missing info: brain and extinction

There is nothing at all on dimetrodon's brain (how big? Was it smart as dinosaurs?) or on why it went extinct. Fig (talk) 11:22, 31 December 2015 (UTC)

Outdated reference?

The article (at Description/Skin) cites "Petr Konstantinovich Tchudinov, 1965, "New Facts about the Fauna of the Upper Permian of the USSR", Journal of Geology, 73:117-30". (I brought the reference over from the article, Estemmenosuchus, to fill out a bare name-and-date reference.) Is a fifty-one-year-old article on paleontology still a reliable source? Specifically, is that article still reliable? J. D. Crutchfield | Talk 16:31, 2 May 2016 (UTC)

I have deleted a couple of new references to the Tchudinov article added by @VRB TO:, on the assumption that Tchudinov (1965) is no longer a reliable source. If Tchudinov's speculations are still considered valid, there should be more recent, reliable sources saying so. J. D. Crutchfield | Talk 20:45, 9 May 2016 (UTC)

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Merge proposal

I propose thatList of Dimetrodon species and Dimetrodon borealis be merged into Dimetrodon . I think that the content in the List of Dimetrodon species and Dimetrodon borealis articles can easily be explained in the context of the Dimetrodon article. the information List of Dimetrodon species article could just be explained in another category called 'information' in the species table . The 'Descirption' part of the borealis article could be the 'information' for it in the species table. Then 'History of study' in borealis could be part of the 'Classification history' of Dimetrodon as a sub-section. Thank you for understanding. 65.255.88.233 (talk)

• Either that, or into List of Dimetrodon species. Or possibly both into this one (which I would prefer). FunkMonk (talk) 8:35 pm, Yesterday (UTC+2)

Or even have D. borealis be its own subsection?--Mr Fink (talk) 02:38, 8 May 2017 (UTC)

I don't think that is a good idea. Both of the two articles have good lengths, and the Dimetrodon article is long enough as it is. Petter Bøckman (talk) 06:46, 8 May 2017 (UTC)

There are some guidelines at WP:Article length, at 58 kb, this one shouldn't be too long... But it's a matter of "philosophy", personally, I prefer having as much info in one place, so I don't have to chase links into a labyrinth. Unless an article is extremely long, such as Tyrannosaurus, but this article isn't even close. FunkMonk (talk) 08:47, 8 May 2017 (UTC)

Let's start small. Can we all agree that the information in List of Dimetrodon species should be put in the species table in Dimetrodon??65.255.88.233 (talk) 15:50, 8 May 2017 (UTC)

Either that, or in the history section. If I had written the article, I would have dealt with the discovery of each species chronologically in the history section as prose. Lists in articles are also discouraged, per WP:embedded lists. FunkMonk (talk) 16:18, 8 May 2017 (UTC)

Yes, that would make it much more easier to read the article.65.255.88.233 (talk) 22:04, 8 May 2017 (UTC)