Talk:Evolution of mammals

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older entries[edit]

Epipubic bones also found in males, both with and without pouches.


Very impressive article, folks - one of the best I've seen on Wikipedia in the last year or so. Thanks! -- Writtenonsand (talk) 13:18, 17 November 2007 (UTC)

Evolution as "experimenting". Tweak?[edit]

"Multituberculates ... are a fine example of how evolution was "experimenting" in the Mesozoic." --- I suggest that we tweak this sentence, as IMHO even with the scare quotes on "experimenting" it tends to re-inforce the popular misconception that evolution is conscious or teleological rather than stochastic. -- Writtenonsand (talk) 13:34, 17 November 2007 (UTC)

I certainly don't want to encourage misconceptions that evolution is conscious or teleological. But I couldn't think of an alternative phrasing which was not much longer, and the article is rather long already. If you can think of an alternative that adds no more than a handful of words to the length, that would be good.Philcha (talk) 16:41, 17 November 2007 (UTC)

Section "Expansion of ecological niches" - add further taxonomic clarification?[edit]

The section Expansion of ecological niches in the Mesozoic lists "mammaliforms and true mammals" -- I suggest that we add in a note on the relevent order for each item listed, in order to give readers a better sense of the taxonomic picture. E.g., "Castorocauda (order Docodonta), which lived in the mid Jurassic ..." -- Writtenonsand (talk) 13:44, 17 November 2007 (UTC)

I'm not happy with this idea as it would increase the length and complexity of a long, complex article. IMO: the general reader doesn't need it and wouldn't understand it; specialists know the taxonomic context already; intermediate readers can get the taxonomic context from the linked articles on the animals mentioned.Philcha (talk) 16:44, 17 November 2007 (UTC)

clade template[edit]

Great article! Have you ever used the Clade template before? It'll preserve formatting of the cladograms regardless of page size or resolution, and it looks cleaner because it's not set aside in a box, with individual "---"s. For comparison, here's your first tree:

      +-- Amphibians ---------------------------------------

And here is a quick conversion to Clade template:









If you're interested, I could convert them for you (not right now, though), or if you'd like to do them yourself, I have a few examples here. J. Spencer (talk) 15:21, 17 November 2007 (UTC)

Intersting idea. I tried reducing the browser window width and your clade template behaved better than the "ASCII art". How would it work for something more complex, e.g. Fossil-based_family_tree_of_placental mammals? Philcha (talk) 16:54, 17 November 2007 (UTC)
Hmm... the extra information makes it look trickier, but I'll give it a shot. J. Spencer (talk) 00:15, 18 November 2007 (UTC)

Unless there's something I don't understand (which is entirely possible), doesn't the clade graph imply that Therapsid and Pelycosaur are sister clades. Would this be more correct:









Ennisj (talk) 09:32, 14 December 2009 (UTC)

How's this? I had to flip some clades to make the appearance better, so the order is not exactly the same.


Xenarthra (Paleocene)
(armadillos, anteaters, sloths)


Pholidota (early Eocene)


some extinct groups X


Insectivora (Late Cretaceous)
(hedgehogs, shrews, moles, tenrecs)


Zalambdalestidae X (late Cretaceous)


Macroscelidea (late Eocene)
(elephant shrews)


Anagaloidea X

Glires (early Paleocene)

Lagomorpha (Eocene)

Rodentia (late Paleocene)
(mice & ratssquirrels,


Scandentia (mid Eocene)
(tree shrews)


Plesiadapiformes X

Primates (early Paleocene)


Dermoptera (late Eocene)

Chiroptera (late Paleocene)


Ferae (early Paleocene)

 Ungulatomorpha (late Cretaceous) 

Hilalia X


Perissodactyla (late Paleocene)
(odd-toed ungulates:
horses, rhinos, tapirs)

Tubulidentata (early Miocene)

 Paenungulata ("not quite ungulates") 

Sirenia (early Eocene)
(manatees, dugongs)

Proboscidea (early Eocene)

Hyracoidea (early Eocene)

 Eparctocyona (late Cretaceous) 

Arctostylopida X (late Paleocene)


Mesonychia X (mid Paleocene)
but not closely related
to modern carnivorans)


Cetacea (early Eocene)

Artiodactyla (early Eocene)
(even-toed ungulates:

(some extinct groups) X

J. Spencer (talk) 02:02, 18 November 2007 (UTC)

Thanks for trying, but I prefer to stick with the "ASCII art". I run my screen at 800x600 because I have poor eyesight, and at 800x600 the template causes a lot of horizontal scrolling. With the "ASCII art" one can mitigate that by reducing the insets. Is there any way to reduce horizontal scrolling when using the template? Also in this particular case I find the "ASCII art" version easier to read because most modern mammals are descended from the Epitheria.
I've just had a rather wild idea, which I'm surprised I didn't think of before. Could cladograms be represented by expandable / collapsible trees, similar to those used for folders by Windows Explorer and many email programs? The same approach is also used in some Web pages, using DHTML. Could that be made to work in Wikipedia, and would it be acceptable? Philcha (talk) 18:18, 21 November 2007 (UTC)
I have no clue how one would include DHTML, but if it could be made to work (the now-absent Josh Grosse created the clade template), I don't see why not. J. Spencer (talk) 22:36, 21 November 2007 (UTC)
I've posted the suggestion at Wikipedia talk:Village pump (proposals) Philcha (talk) 16:32, 24 November 2007 (UTC)
There is a problem here... Pholidota is shown as quite separate from Ferae, but Ferae (as it is currently defined) is a clade containing Carnivora and Pholidota. If the connection between Pholidota and Carnivora is rejected, then shouldn't Ferae in this diagram be replaced by Carnivora?

Lactation / suckling and neck ribs[edit]

Someone added to the section "Lactation"

This is an interesting idea, but the way it is currently presented has major weaknesses:

  • No citations.
  • Ambiguity. Would neck ribs prevent the mother from producing milk or the baby from taking it? I expect the latter but then the phrasing could be a lot clearer. I'd also like more explanation of why neck ribs are such an obtacle.
  • Logic. If correct, the presence of neck ribs would imply no suckling but absence of neck ribs would no imply suckling - in fact one would expect to find (eventually) transitional forms with no neck ribs but without suckling.
  • Position - at present it breaks the flow of the text.

I hope the person who added this material will respond here or by editing that part of the article. Otherwise I'll remove it in 2 weeks. Philcha (talk) 14:56, 15 December 2007 (UTC)

I've removed the remarks about neck ribs. Philcha (talk) 18:12, 29 December 2007 (UTC)

What came first, preening or lactation? Per my observation, preening clearly led to lactation. David W. Lambert, 14830 Local time - Sat Aug 2, 22:26 EST 2014 — Preceding unsigned comment added by (talk) 03:32, 3 August 2014 (UTC)

Great work![edit]

Great work, Philcha! My compliments, you assembled a great article! DaMatriX (talk) 00:00, 22 December 2007 (UTC)

Agreed. May I make a suggestion that the article Evolution of mammalian auditory ossicles could use some of the same hand. Especially, the drawings of the jaw-to-middle ear transitional forms. TomS TDotO (talk) 11:20, 29 February 2008 (UTC)

Hair/fur helping mammals survive K-T extinction[edit]

I've removed from the end of "(earliest evolution of) Hair / fur" the following sentence: "The possession of such insulation is thought to be one of the several reasons that mammals triumphed the K-T extinction." It provides no refs to support it, and I've never seen any such suggestion from a credible source. Philcha (talk) 18:35, 29 December 2007 (UTC)


To improve accessibility, could we have a timeline similar to {{Permian graphical timeline}} in the article? This would give an overview of development of key features with approximate dates, and would be more meaningful for readers who aren't familiar with the eras and their dates.-gadfium 20:21, 14 April 2008 (UTC)

Seconded. The article as it stands, in this and other respects, seems aimed not at a general population but at university undergraduates at least. Elsewhere in the encyclopaedia, for certain topics, it might be reasonable to assume a higher level of education (Madhamaka Philosophy, for example), but that is not true for this topic. High school students as well as people with a general interest might visit this page and would be familiar with neither the divisions of mammals you have chosen or the eras that you have chosen as your timeline.

-- (talk) 18:20, 12 July 2015 (UTC)

Good article nomination[edit]

This article ought to be nominated at Wikipedia:Good article nominations. Cheers! Wassupwestcoast (talk) 01:07, 19 April 2008 (UTC)


There is a press release which reports about research on the origins of the mammalian placenta. Should something about this be included as one of the distinctively mammalian features which evolved?

Stanford University Medical Center (2008, April 17). Clues To Ancestral Origin Of Placenta Emerge In Genetics Study. ScienceDaily. Retrieved April 19, 2008, from Clues To Ancestral Origin Of Placenta Emerge In Genetics Study TomS TDotO (talk) 13:13, 19 April 2008 (UTC)

Perhaps, if we can get the peer-reviewed article and it actually covers the same ground ("news" articles often contain off-the-cuff comments and personal opinions that the researchers did not include in the the peer-reviewed article). The news article is wrong on at least 1 point, where it says, "the placenta initially evolved through repurposing genes the early mammals inherited from their immediate ancestors when they arose more than 120 million years ago." If these genes are "in common with birds and reptiles" they were inherited from the last common ancestor of mammals and reptiles (possibly a basal amniote) over 320M years ago.
Please keep suggesting things! It's like football (soccer or gridiron) - most moves break down, but eventualy you SCO-O-O-O-O-ORE. Philcha (talk) 14:54, 19 April 2008 (UTC)

Evolution of Man - A Different View[edit]



A hypothesis is proposed that mammals evolved directly from amphibians rather than from reptiles. Also, how paedoneogenesis and sexual selection could account for man’s attributes including a larger brain relative to other mammals.


It is usually assumed and taught that mammals including man have evolved from reptiles, which in turn evolved from amphibians.

Reptiles have a vascular system that has developed from the right aortic arch. A similar system appertains in birds, which have an accepted evolution from reptiles (ornithischian dinosaurs). They appeared in the Cretaceous period (145 million years ago).

Mammals have a vascular system that has developed from the left aortic arch. Reptiles have a skull whose jaw is derived from several bones. Mammals have a bony separation of the swallowing and breathing passages. Mammals have functional differentiation of teeth. Reptiles’ teeth are usually all similar and replaceable. The limbs are lateral in reptiles but evolved ventrally in mammals. These differences are to be seen over the millennia.

To determine the origin therefore of mammals one must search further back in time for an ancient amphibian with bilateral aortic arches that could have allowed the left aortic arch to become dominant. The progenitors of the amphibia are the lung fish (dipnoae), which have many affinities to the amphibia such as lungs and an ability to respire partially through the integument.

It is probable that primitive lungs developed in Devonian times (400 million years ago) in fish that lived in pools that were drying out. Nasal pouches in fish have an olfactory function, but in the lungfishes nostrils appear with associated skull changes and the fish is able to breathe bypassing the mouth. Lungfish have fleshy fins with skeletal support that have the beginnings of jointed limbs and radiating terminations. The ancient lungfishes had now the opportunity to develop the tetrapod gait and ability to utilise the atmosphere direct for respiration.

In Devonian times the first amphibia, the Stegocephalia appeared. An example was Eryops, a crocodile like animal about six feet long which was adapted to both aquatic and terrestrial environments. Reptiles lay eggs on land whereas amphibia lay their eggs in water. These shell less eggs could have been retained in the oviduct whilst development proceeded and this way the evolution of placentae could occur. The placenta is thought to have evolved from the allantois of the egg, which is an umbilical extension of the gut.

The Reptilia evolved from stem reptiles called cotylosaurs that in turn evolved from amphibia. Dimetrodon being an example. Reptiles started to make their appearance in the Carboniferous era, (360 million yeas ago). The first reptiles were the lizard like cotylosaurs. The stem reptiles gave rise to two great groups, the archosaurs (dinosaurs and crocodiles) and the lepidosaurs (lizards and snakes).

In the later Permian (290 million years ago) animals with mammalian features appear. For example Cynognathus had a differentiated dentition with a secondary palate and the limbs supported the body ventrally.

In the Triassic (245 million years ago) it is thought these early mammals became viviparous, that is gave birth to their shell less young. By the Cretaceous (145 million years ago) mammals had started to differentiate into the marsupials and placentals which suckled their young. These appear to have mainly been small active rodent like animals. If like present-day rodents they were nocturnal it would have necessitated being homoeothermic (warm blooded), aided by a furry coat.

These early mammals are thought to have been insectivores and from arboreal species the early progenitors of the primates evolved in the Paleocene (65 million years ago).

Originally it was thought that man evolved from tree climbing primates, but many now believe that man evolved from ground living free roaming animals with a lifestyle similar to baboons. Rather like ‘Lucy’ the hominid, one of whose relative’s footprints have been left to posterity in the Oldivai gorge.

Important evolutionary features developed; binocular vision to scan the horizon aided by bipedal gait to see over the savannah. The upper limbs could now become manipulative.

In the Miocene about 14 to 20 million years ago primitive apes (Dryopithecines) branched into two groups. One of which gave, rise to the early tree dwelling apes about 7 million years ago, whilst the other group lived in open country. This latter group gave rise to Australopithecus, which includes ‘Lucy’, who had a true bipedal gait, but with features of both hominids and apes.

In the Pleistocene about 1.5 to 3 million years ago Homo habilis (‘the tool maker’) made an appearance to be followed by Homo erectus, to be supplanted by Homo sapiens.

A mystery that has never been explained is why man among the apes is relatively hairless. I would suggest that this is due to sexual selection of juvenile characteristics, which when associated with the ability to reproduce is termed paedoneogenesis.

This would explain the disappearance of the heavy brow and the less prominent jaw. The young of mammals have a relatively larger brain compared with the adult. Retention of this attribute could explain the superior intelligence of man over other apes.

Thus, in my opinion the evidence indicates that man and the rest of the mammalia evolved direct from an amphibian ancestor and not by way of reptiles, which independently arose from the amphibia. Dr t c mayer (talk) 14:50, 2 July 2008 (UTC)

First, that's nice, but original research. We can't use it unless you submit it to a journal and get published.
Second, your research is a bit redundant, as a majority of modern researchers agree that mammals did not evolve from reptiles, they evolved from a common tetrapod ancestor that was not reptile (Sauropsida), but what would be generically called and "amphibian" (though that name is formally restricted to the modern group containing frogs and salamanders). Derived characteristics of reptiles are absent in mammals and stem-mammals: dry skin, scales, etc. In fact skin impressions from early synapsids show "fishapod" style dermal scales instead of reptilian scales. Your paper doesn't appear to cite any other sources. More research of relevant lit might be useful in demonstrating this view is not new ;) Dinoguy2 (talk) 01:55, 3 July 2008 (UTC)

Are all modern Afrotheria from Africa and South America?[edit]

The article (Family tree of placental mammals according to molecular phylogenetics section) says:

The grouping together of the Afrotheria has some geological justification. All surviving members of the Afrotheria live in South America or (mainly) Africa.

This statement isn't true - one of the surviving species of this group is Elephas maximus, also known as the Asian Elephant, lives (as the name suggests) in Asia. (talk) 11:45, 27 July 2008 (UTC)

Good point! Does anyone know the evolutionary history of Proboscidea? For example if the fossil record showed that the earliest Proboscidea were African, the Afrotheria hypothesis remains viable — otherwise it could be in trouble. I know that Afrotheria is a clade based on DNA, not on bones. But DNA analysis can't tell us when or where earlier members of the clade lived, which is IMO essential in order to do a good job of incorporating's point into the article. -- Philcha (talk) 13:55, 27 July 2008 (UTC)
I found the following statement in Amebelodon:
Amebelodon is a member of a diverse group of primitive proboscideans called gomphotheres, a group that also gave rise to the modern elephants and their close relative the mammoth. Amebelodon first appeared in the Great Plains and Gulf Coast regions of North America during the late Miocene, roughly between 9 and 8 million years ago...
This would seem to mean that modern elephants evolved from a North American species from 8-9 million years ago, which means that the point about Afrotheria seems not to be true. (talk) 08:29, 11 August 2008 (UTC)
Scientists map elephant evolution says the African and Indian elephant lineages diverged about 7.6 MYA, in Africa. However I don't know the earlier history of the elephant lineage. -- Philcha (talk) 23:40, 11 August 2008 (UTC)

The earliest Proboscidea were African and lived 60000000 yeres ago. The reason there are Asian and Northamarican Proboscideans is that these continents were connected by land bridges a few million years ago. — Preceding unsigned comment added by Aliafroz1901 (talkcontribs) 08:04, 22 July 2012 (UTC)

Where are humans?[edit]

Just to point out I couldn't see humans anywhere in the definition of a mammal Phthinosuchusisanancestor (talk) 19:01, 22 October 2008 (UTC)

Humans are mammals, so they "inherit" all the defining features of mammals. OTOH specifically human characteristics can't be used in defining "mammal" as they would not apply to the vast majority of mammals. -- Philcha (talk) 19:06, 22 October 2008 (UTC)

Evolution of Vivipary?[edit]

This is a glaring omission for me. How and when did synapsids move from an egg-laying model to giving birth to live young? How did vivipary evolve? —Preceding unsigned comment added by Captainsiberia (talkcontribs) 03:08, 2 April 2009 (UTC)

While researching for the work on this article I did a while ago, I found nothing on the subject - so I guess it's a glaring omission for the scientists too. The best evidence would be a fossil of a pregnant mammal, but fossilisation is rare and probably most animals that were fossilised have not been discovered.
OTOH the earliest known marsupial, Sinodelphys, and the earliest known eutherian, Eomaia, date from about 125 million years ago, so it's a reasonable bet that viviparity appeared before then. However stating that in the article would be original research, which WP forbids. If you find a good source for info on this, please include it in the article or post it in the Talk page.
BTW viviparity is more common among animals than you might think - some sponges (!), all scorpions, platyctenid ctenophores, some sharks and probably several other animals I don't know about. --Philcha (talk) 07:18, 2 April 2009 (UTC)

Eotherapsid hypothesis for the origin of Monotremata[edit]

Ivakhnenko, Mikhail F. (2009). "Eotherapsid hypothesis for the origin of Monotremata". Paleontological Journal 43 (3): 237–250.  Aleksey (Alnagov (talk) 09:25, 23 June 2009 (UTC))

Cladogram Template ( Inconsistency[edit]

This might just be nitpicking, but i noticed the cladogram (morphological) under the section 'Evolution of major groups of living mammals' is very slightly different to the original over at In particular, there are quite a few extra '+' signs on the one reproduced here. As i understand the system used by, the '+' signs represent missing or unnamed clades. Therefore, i'm not too sure what the following part of the cladogram means:


   +--Xenarthra (late cretaceous)
   |  (armadillos, anteaters, sloths)

If you replace the '+' sign with a name, you get the following:


   |--Xenarthra (late cretaceous)
   |  (armadillos, anteaters, sloths)

This doesn't make much sense as you have two clades name (both Eutheria and unnamed) that unite the two following clades.

Please can someone knowledgable on this or maybe a member of take a look at this? Many thanks.

Darkuser999 (talk) 17:12, 12 October 2009 (UTC)

So there's another problem with the cladogram. This one is about the location of culogos, bats, plesiadapiforms and primates in relation to one another.

If one visits the plesiadapiform entry or looks at some other cladograms on Wikipedia and elsewhere (although the conflict within wikipedia is far more relevant), culogos are positioned differently with respect to the others (bats separate from all, culogos as a sister clade to primatamorphs). I have seen a number of statements to the effect that new research supports this latter formulation, but I am not a biologist and don't keep up with research to that degree of specificity. If it hits Nature, etc., I'll have probably read it. Otherwise, it's outside my specialty and out of sight out of mind.

Still, the evolutionary relationships of major clades within vertebrata and the radiation of bilaterians are quite interesting to me so I would like very much if someone could look at this cladogram & the one on (for example) the plesiadapiform entry & determine which is most correct given research (or, if possibly both are in error when compared to current research).

I understand that there are significant periods when theories are hashed out when it is not clear which is the best interpretation. That's fine. Perhaps pages that deal with finer-grained cladograms in other entries need to have multiple options spelled out there and this one left until the science is more clear. But as long as WP has internal inconsistencies, we should try to either fix or explain them so non-scientists don't look at them and take it as evidence that we don't know what we're doing.

And, y'know, to pass on the best info possible. That too.

Thanks folks. —Preceding unsigned comment added by Cripdyke (talkcontribs) 03:42, 14 September 2010 (UTC)

Dating the Platypus-Echidna split[edit]

Under the Monotremes heading, the article says that the finding that Teinolophos was a Cretaceous platypus shows that the platypus and echidna lineages diverged earlier, but that seems to contradict a recent finding that implies that they split only about 19-48 million years ago.

Doesn't that seem like it needs to be included here? —Preceding unsigned comment added by (talk) 21:25, 14 October 2009 (UTC)

Go for it. Looks like there are 2 competing views to be summarised: (a) T. was a basal monotreme, before the platypus and echidna lineages diverged, possibly quite recently; and (b) T. was a platypus, and the platypus and echidna lineages diverged before T. Please add the citation for the paper you mentioned. --Philcha (talk) 22:09, 14 October 2009 (UTC)


A great article! There's one omission for me though - akinesis. Most amniotes have kinetic skulls apart from mammals, which is an important character of mammals. In Kardong (Vertebrate Evolution), he explains that the primary reason for Akinesis is because of the formation of a secondary palate, which prevents movement relative to the braincase; the secondary palate is required for suckling in infants. I might add this in a couple of weeks (after my exams!), although it has to be said I would have thought akinesis would have been unnecessary anyway due to the strength of the dentary-squamosal joint and the associated lateral mobility of the jaw. But I guess you can't really disagree with Kardong. Oliverjknevitt (talk) 14:29, 22 May 2010 (UTC)

You may also want to write the akinesis article. It currently is a redirect to hypokinesia. - UtherSRG (talk) 14:43, 22 May 2010 (UTC)
It's a little more complex when you look at how amniotes originates in the Late Carboniferous and almost split. The major groups of are:
  • Sauropids, which include lizards (Late Carboniferous), crocodilians (Triassic), dinosaurs (Triassic), and birds (Late-ish Jurassic). Most sauropids have kinetic skulls, except for birds. I haven't researched this but guess that the evolution of birds' large brain forced the braincase to expand and dominate the skull, making it rigid.
  • Synapsids developed rigid skulls very quickly. Their only living members are mammals.
  • Anapsids may have 1 ancestor or more - paleologists are divided. Most died out in the Permian-Triassic extinction event, but 1 group survived into the Triassic.
  • Testudines (turtles, tortoises, etc.) are the greatest puzzle to paleologists. The anapsid skull looks "primitive", but the eariest fossil testudines, in the Triassic, already have the legs inside the ribcage

Controversial phylogenetics?[edit]

"One often feels compelled to try to explain the evolution of features that do not appear in fossils. This endeavor often involves Molecular phylogenetics, a technique that has become popular since the mid-1980s but is still often controversial because of its assumptions, especially about the reliability of the molecular clock."

The wording of this is quite odd. "compelled" by whom? Also, molecular phylogenetics is used by thousands of studies (the phrase is in about 30,000 articles, according to Google Scholar), so I don't think it is still "controversial". Like any method, it must be used appropriately. The molecular clock assumption is often violated, which is true, but 1) molecular phylogenetic methods to infer a topology or even tree with branch lengths do not depend on a clock, and 2) there are methods that can provide dates even in the absence of a molecular clock.

--Bcomeara (talk) 20:55, 19 August 2010 (UTC)

I created this article in 2007 or 2008, because Mammal was very inaccurate. At the time molecular phylogenetics was regarded as poor at dating. In 2009-2010 a combination of more powerful computers and more advanced software provide more accurate dating - although a run usually takes 4 to 6 weeks. --Philcha (talk) 22:05, 19 August 2010 (UTC)

Outdated, incorrect term "mammal-like reptiles" does not need to be in the first sentence[edit]

Does anyone agree that this phrase does not be in the first sentence? I put a comment that this term has been used in the past at the end of the second paragraph. It does not seem appropriate to put this in the first sentence. Even at Synapsida it is not in the first sentence. Thegreyanomaly (talk) 03:27, 12 May 2011 (UTC)

The term mammal-like reptile may be outdated in phylogenetic taxonomy, but it is not incorrect per se. Calling it incorrect is mixing phylogeny and classification. It is a common term found in any number of textbooks. I believe it warrants mentioning early on, if not in the first sentence, at least in the lede. Synapsida is a difficult concept, in principle it denotes the whole synapsid line, but is used almost exclusively for the non-mammalian grade. This ambiguity is very difficult to get across to a layman (not to mention lower grade students). Using mammal-like reptiles when one actually wish to refer to the non-mammalian grade is better, as the definition is very clear and has been stable for over a century. Petter Bøckman (talk) 10:41, 12 May 2011 (UTC)

(I updated the section title from "the lead" to "first sentence"). We are not talking about removing the phrase all together. I am talking about moving it from the first sentence to later on in the lead. Does it really need to be in the first sentence, when it is bolded at the end of the second paragraph (which is also part of the lead)? Thegreyanomaly (talk) 00:08, 13 May 2011 (UTC)

I think it needs to be in the first paragraph. The paragraph is not too well written anyhow, and stumbles over itself trying to explain phylognetic concepts rather than the evolution of mammals. A rewrite is in order. I would suggest covering basic mammals evolution in the first paragraph, and use the last paragraph of the lede to detail problematic concepts like Crown Mammalia, Mammaliformes and Synapsida. Petter Bøckman (talk) 07:44, 13 May 2011 (UTC)

Ok so you at least agree it doesn't have to be in the first sentence, just the first para. Right now I think throwing "sometimes called "mammal-like reptiles"" right in the first sentence randomly is rather confusing. Thegreyanomaly (talk) 07:54, 13 May 2011 (UTC)

One solution would be to identify the ancestors as therapsids, thus avoid the term "reptiles" if that is the aim. The basic idea must be to inform the reader than mammals did not appear out of thin air, but evolved from somewhere, in this case a group of rather strange looking ugly critters Petter Bøckman (talk) 08:02, 13 May 2011 (UTC)

"true" vs "crown" mammals[edit]

Hi, Petter Bøckman. I see you've changed "true mammals" to "crown mammals". I admit "crown mammals" is more exact. But I think "true mammals" is easier for general readers, who usually are not aware of phylogenic / cladistic terms. --Philcha (talk) 11:09, 13 May 2011 (UTC)

I've added a sentence explaining the term. There's nothing inherently 'true' about about the crown group (nothing inherently 'crowny' either for that matter), it is all about naming convention. I object to the term "true" since it indicates that e.g. multituberculates are somehow "untrue" mammals, i.e. have major traits that would set them off relative to the 'true' group. The term 'crown' at least is fairly neutral, and easily understood relative to a tree analogy. Petter Bøckman (talk) 11:59, 13 May 2011 (UTC)
Multituberculates quite probably are crown mammals, though. Ucucha 12:04, 13 May 2011 (UTC)
Just now discovered that myself, sigh. I guess I need another example... Petter Bøckman (talk) 12:09, 13 May 2011 (UTC)
Morganucodontids will do, I think. If I recall correctly, there is also the problem that people disagree about the definition of "Mammalia": some make it equal to the crown group of living mammals (and therefore, possibly excluding multis), while others use Mammalia in the meaning of Mammaliaformes. Ucucha 12:16, 13 May 2011 (UTC)
The problem is that while the crown group approach to defining well known taxa is not universally accepted (not even within the phylogenetic taxonomy circles), it is quite commonly in some quarters (notably dinosaur studies). Some of the PhyloCode people are very keen on pushing the "crown-group-as-the-only-acceptable-group" stance, particularly for birds and mammals, but without being explicit about it. I find it advisable to call crown groups 'crown this' and 'crown that', to avoid confusion (Mammalia (traditional) vs. Crown Mammalia being a salient point). Interestingly, even the term 'crown group' sees other uses, see for instance Australosphenida and Ausktribosphenidae. Petter Bøckman (talk) 12:26, 13 May 2011 (UTC)
We can't win. See Evolution_of_mammals#Mammals_or_mammaliformes.3F. --Philcha (talk) 13:02, 13 May 2011 (UTC)
That shouldn't stop us from saying crown mammals when we mean crown mammals. Being consequent in using the terms mammaliformes and crown mammals we neatly avoid the whole discussion. See Rowe & al for an example of this approach in a very relevant mammal article. Petter Bøckman (talk) 13:19, 13 May 2011 (UTC)
Philcha, you wrote the (original and not very mutated) section Evolution_of_mammals#Mammals_or_mammaliformes? yourself, including the statement "Although this now appears to be the majority approach,...". This statement did never have an inline reference. The sentence before has one; unhappily, the link (at the moment = note 23) now is stale. You may be right, but then there should be some (tertiary) sources supporting the claim. JoergenB (talk) 19:20, 10 July 2011 (UTC)
In the 13 May 2011 discussion above, Petter Bøckman's comments at 11:59 and 13:19 are spot on. And using the phrase "true mammals" does nothing to help the general reader; it promotes the misunderstandings referred to in the 11:59 comment, while "crown mammals," with a Wikilink to Crown group, can lead the reader to a clear understanding of the concept. Is there some reason to stop at only two replacements of "true mammal" by "crown mammal"? There are half a dozen more occurrences of the former phrase that invite such replacement. Peter M. Brown (talk) 16:52, 21 January 2012 (UTC)
Completely agree. --Dr. Günter Bechly (talk) 13:17, 22 January 2012 (UTC)

Triassic takeover[edit]

My revisions of October 9 and October 11 are made in response to dissatisfaction, as noted in italic purple, with the following text. Discussion is welcome.

The catastrophic Permian-Triassic mass extinction slightly more than 250 million years ago killed off about 70 percent of terrestrial vertebrate species, and the majority of land plants.
As a result:
  • Ecosystems and food chains collapsed, and the recovery took about 6 million years.
  • The survivors had to re-start the struggle for dominance of their former ecological niches — even the cynodonts, which had seemed on the way to dominance at the end of the Permian.
The 6 million year figure is low. For consistency with the Lystrosaurus article, I'm calling it 30 million. What figure one uses, of course, depends on one's criterion for a recovery's being complete.
After a complete collapse of the ecosystem, the former niches no longer exist, so there can be no struggle to dominate them. To survive, a species must carve out a new niche in the transformed world.
The claim about the cynodonts seems to be that there was a trend in the late Permian which, had it continued, would have resulted in cynodont dominance. This is dubious. To suggest such a trend, note it below, on this page, and the matter can be discussed
But the cynodonts lost out to a previously obscure group of sauropsids, the archosaurs (which include the ancestors of crocodilians, dinosaurs and birds). This reversal of fortunes is often called the "Triassic takeover". Several explanations have been offered for it, but the most likely is that the early Triassic was predominantly arid and therefore archosaurs' superior water conservation gave them a decisive advantage. All known archosaurs have glandless skins and eliminate nitrogenous waste in a uric acid paste containing little water, while the cynodonts probably excreted most such waste in a solution of urea, as mammals do today; considerable water is required to keep urea dissolved.
As there are indeed several explanations, reporting only one is open to the charge of violating WP:UNDUE . My revision is open to the same charge, but I have at least refrained from endorsing the proffered explanation.
The Triassic takeover was gradual — in the earliest part of the Triassic cynodonts were the main predators and lystrosaurs were the main herbivores, but by the mid-Triassic archosaurs dominated all the large carnivore and herbivore niches.
As regards predators, Benton 2004, p. 140 is quite clear that dominance passed directly from the gorgonopsians and titanosuchids to the archosaurs. The cynodonts never held this baton. Disagree? Discuss below. As regards herbivores, "Triassic takeover" has been defined only with reference to cynodonts and archosaurs, so the situation of the lystrosaurs is irrelevant.
But the Triassic takeover may have been a vital factor in the evolution of cynodonts into mammals. The cynodonts' descendants were only able to survive as small, mainly nocturnal insectivores.
The wording suggests that the mammals supplanted the the cynodonts during the Triassic. This is not correct, as the tritylodonts survived until the Middle Cretaceous.
Further, the statement that the mammals "were only able to survive" in their ecological niche, while strictly true, suggests that they were somehow more limited than other taxa. On the contrary, all organisms are so limited. Hawks can only survive as aerial predators; fish, only underwater.

Peter M. Brown (talk) 17:27, 11 October 2011 (UTC)

Early mammal metabolism[edit]

The Warm-bloodedness section notes, correctly, that

Modern monotremes have a lower body temperature than marsupials and placentals.

It then adds, however

So the main question is when a monotreme-like metabolism evolved in mammals.

It does not follow that this is "the main question" or even that some mammals prior to the monotreme-therian divergence had "a monotreme-like metabolism." The last common ancestor of monotremes and therians may have had a basal metabolism characteristic of the monotremes, of the therians, or neither.

The next sentence underscores the point:

The evidence found so far suggests Triassic cynodonts may have had fairly high metabolic rates, but is not conclusive.

If premammalian cynodonts had a therian level of metabolism, basal mammals could well have inherited it. In that case, the level decreased somewhere in the lineage leading to the monotremes.

Peter M. Brown (talk) 14:40, 16 December 2011 (UTC)

I've had a look at it, see if you like it better now. Petter Bøckman (talk) 21:34, 16 December 2011 (UTC)
I'm still having some problems.
The platypus is homeothermic with tight temperature regulation to keep its body temperature about 32 °C. I therefore don't understand what it is about monotremes that you are comparing with therians in the first sentence. The fact that precise thermoregulation is found in all three extant groups is surely evidence—albeit not conclusive—that it was present in a common ancestor. Why should the 32° set point of a platypus be any more likely to be a secondarily derived trait than the 38° set point of a therian mammal?
I suggest dropping the final sentence of the section. It is unsourced and the same point is made, with citations, in the two following sections.
Peter M. Brown (talk) 22:58, 16 December 2011 (UTC)
Well, the temperature fluctuation of the echidna is rather large. It is likely bradythermy rather than poikilothermy, but it is still quite variable. If we are to speculate on what it primary and what it secondary, it could just as well be the very tight control of the platypus as the variable echidna that is the derived condition. Therians have all kinds of derived features, not at least a lot higher body temperature, so I see no reason to assume tight temperature control was a common trait. But you have a point, I suggest dropping the sentence. Petter Bøckman (talk) 23:13, 16 December 2011 (UTC)
Don't you go to bed? It's after midnight in Oslo!
I think that you are saying that "a lot higher body temperature" is a derived feature of therians. What is the basis for that?
For the phylogenetic bracketing to work, why need it be assumed that monotreme metabolism isn't a secondarily evolved trait? The suggestion of Watson and Graves in the cited paper is that the durations of cellular processes in monotremes be explained by supposing that an ancestor of extant monotremes had a body temperature of 37 °C. Though this is at the upper end of the 32°-to-37° bracket, it does not fall outside it, so there is no conflict between the cytological approach and the phylogenetic one.
As regards echidnas: they seem to have facultative homeothermy, arguably an advance over the obligate homeothermy of platypuses and, e.g., humans. They're homeothermic when they need to be, as when they're brooding eggs, but they don't bother otherwise.
I can guess from context, but what is bradythermy?
Peter M. Brown (talk) 00:28, 17 December 2011 (UTC)
Had a late-nighter. I have the house full of kids, it's the only time I have to do things like this. ;)
Bradythermy is just what you described as "facultative homeothermy". The echidna seems to switch to poikilothermy when it hits a lean patch, to save energy stores. There's a lot of the animals often thought of as cold blooded that can be surprisingly homeothermic when they need to (varanids, crocodiles). Bradythermy covers the lot.
I'm not sure I agree with your last edits. Phylogenetic bracketing of Morganucodon and Thrinaxodon will have the mammalian crown group at one side of the bracket, on the lower end it will have the assumed primitive amniote default condition (i.e. full poikilothermy). You can not use the crown-group as both upper and lower brackets when you look for stem group animals. It would be like looking for the parental care in Tyrannosaurus using owls and swifts as brackets (the normal brackets are crocodiles and birds). Granted, as Morganucodon and Thrinaxodon are much closer to mammals than to e.g. Hylonomus or Archaeothyris both in time and general anatomy, we guess they lay closer to the mammalian side of the envelope, but using the crown group to conclude they are at the upper range for extant species doesn't make any sense.
On a side-note, I see the same error done when people discuss dinosaur intelligence. They quote studies showing the brightest dinosaurs (Troodon I think) had an encephalization quotient almost in avian range. From that, they conclude that Velociraptor (who was a bit less brainy) showed complex behaviour similar to that associated with parrots and crows. "Almost in avian range" means below birds, close to, but still below. This means the smartest dinosaur was less brainy than the most stupid bird, not "almost as smart as the smartest". Whatever mental feats a Velociraptor could do, a chicken is likely to do them better. For our discussion, it means that Morganucodon and Thrinaxodon are likely to have been a tad less homeotherm than mammals. The question is whether the monotreme temperature of 32°C is the primitive state for mammals, or whether it is derived. I think my edit had that down fairly well. Petter Bøckman (talk) 19:41, 17 December 2011 (UTC)
I find your response puzzling.
Certainly, whether the monotreme temperature is primitive or derived is an interesting question. I don't see why you consider it the question. Whether the therian temperature is primitive or derived is also an interesting question.
Other than that, I agree with everything you say and cannot see that I have said anything different. As I do not even mention Thrinaxodon or Morganucodon, I surely am not "using the crown group to conclude that they are at the upper range for extant species." On the contrary, I think that very unlikely.
It is not clear which of my "last edits" you have a problem with. My very last edit was intended simply as a clarification of your text, which I thought I understood. If I got it wrong, please do fix it.
In principle, phylogenetic bracketing applies only to descendents of the last common ancestor of the anchoring taxa, though it may be suggestive as regards traits of other taxa that are closely related. Since both humans and platypuses have body temperatures in the range 32 °C to 37 °C inclusive, bracketing does predict that all crown mammals have had temperatures in this range.
My problem is with the implication in your revised text that the conclusion from phylogenetic bracketing somehow runs contrary to the thesis that, as Watson and Graves suggest, monotreme metabolism is a secondarily evolved trait. If their hypothetical 37 °C monotreme ancestor was a crown mammal then, since its body temperature does lie within the appropriate range, it provides additional support for the conclusion from bracketing. If it was not a crown mammal, it is irrelevant to that conclusion. In neither case does it conflict.
Peter M. Brown (talk) 01:48, 18 December 2011 (UTC)
Sorry, read that in a daze (the other side effect to a house full of toddlers). I still think the current versions comes off funny. I'd like to emphasize the traditional interpretation more, to make the contrast to the idea of a secondary lower temperature for monotremes stand out better. Petter Bøckman (talk) 08:55, 19 December 2011 (UTC)

Multituberculates belong in Crown Mammalia[edit]

I have revised the cladograms in the sections Family tree — cynodonts to mammals and Family tree of early crown mammals, moving the Allotheria into Crown Mammalia. I have also moved the Multituberculates subsection to the section on The earliest crown mammals with some revisions.

Prior to my edit, the position of the allotherians relied on a cladogram in created by Toby White. Though the explanation provided with this cladogram is certainly cogent, the fact remains that White's view is a minority one, and WP:UNDUE requires that articles "not give minority views as much of or as detailed a description as more widely held views." A look in Mikko's Phylogeny Archive makes clear the minority status of White's position: the five cladograms provided in the pages on Mammaliaformes and Mammalia all cite well-regarded sources and all place Allotheria in Crown Mammalia. Even White acknowledges that the inclusion of the multituberculates in Crown Mammalia is "generally taught."

White may well be correct. His view certainly deserves to be included in the article. Until it is more widely adopted, however, it should not be given such prominence.

Peter M. Brown (talk) 21:08, 20 January 2012 (UTC)

Mammals or mammaliaforms[edit]

My rewrite of 30 January 2012 is made in response to dissatisfaction with much of the previous text, as follows:

One result of these uncertainties has been a change in the paleontologists' definition of "mammal".
The uncertainties referred to, noted in the section preceding Mammals or mammaliaformes?, are the difficulties that a poor fossil record presents for the task of determining phylogeny. The change involved is a redefinition of Mammalia by those attempting to construct a phylogenetic basis for taxonomy, a project that is made more difficult by the uncertainties mentioned. These uncertainties provided no motivation for the redefinition.
For a long time a fossil was considered a mammal if it met the jaw-ear criterion (the jaw joint consists only of the squamosal and dentary; and the articular and the quadrate bones have become the middle ear's malleus and incus).
No support is provided for the historical claim that both the jaw structure and the ear structure have been traditionally required for mammalian status. A case can probably be made for the jaw criterion, but one for the ear is quite unlikely. Of the fifteen traditional definitions listed in Rowe (1988), ear structure is included in only four.
But more recently some paleontologists have usually defined "mammal" as the crown group mammals, i.e. the last common ancestor of monotremes, marsupials and placentals and all of its descendants. The need to address the animals that are more mammal-like than cynodonts, but less closely related to monotremes, marsupials and placentals, led to erecting the group Mammaliaformes to accommodate these primitive forms.
Phylogenetically, mammals are cynodonts. Unless a more restricted meaning of "cynodonts" is intended, and none is obvious, "the animals that are more mammal-like than cynodonts" is meaningless; no animal is more mammal-like than mammals. The phrase "less closely related", used in the second sentence above, standardly expresses a ternary relation: A is less closely related to B than to C. In the present context, A is the mammaliaforms and B is the extant mammals, but C is wholly mysterious.
Although this now appears to be the majority approach, some paleontologists have resisted it because it simply moves most of the problems into the new taxon without solving the original problem; the Mammaliaformes includes some animals with "mammalian" jaw joints and some with "reptilian" (articular-to-quadrate) jaw joints.
There has been no response to JoergenB's request, above, for a secondary-source citation supporting the claim that "this now appears to be the majority approach". The claim can therefore be deleted. Moreover, it is wholly obscure what "the original problem" is. No reason is provided why the facts about mammaliaform jaw joints should be problematic.
Despite these objections, this article follows the majority approach and treats most of the cynodonts' Mesozoic descendants as mammaliaformes.
Most of the cynodonts' Mesozoic descendants were crown mammals—see the chart in Luo (2007). By definition, crown mammals are mammaliaforms. There seems no room for objections.

Peter M. Brown (talk) 19:35, 30 January 2012 (UTC)

"Unconvincing" is not encyclopedic[edit]

In its first paragraph, the section Hair and fur includes the sentence, "Arguments that advanced therapsids already had hair are unconvincing." The source, Ruben and Jones (2000), does not contain the word "unconvincing" or any approximate synonym. In an encyclopedia, the word should only be used in the context unconvincing to so-and-so; to write that something is unconvincing without this qualification is simply to say that the writer is not convinced, a matter lacking in notability.

Of course, though WP edits have to be neutral, it is natural and acceptable that someone interested in a subject should have a point of view and hope to make contributions that lead others to agree. In particular, as National Geographic has recently stated that Thrinaxodon had whiskers, it is important to present the counterargument in some detail, with reliable sources. This can be done in an neutral manner, however. Using the term "unconvincing" is not acceptably neutral. The most effective course, I think, is to delete the sentence that I am challenging; the text then flows naturally into the following paragraph, which presents the actual arguments, most of which are ably reviewed in the Ruben and Jones article.

It is unfortunate that the image of Thrinaxodon in the lede shows anteroposterior streaks that are highly suggestive of hair. Perhaps a better image can be found. (The pinnae in the image are also inappropriate: pinnae enhance hearing only at frequencies over 10,000 Hz and, given its ear structure, Thrinaxodon could not have been sensitive to such frequencies.)

Peter M. Brown (talk) 20:05, 26 February 2012 (UTC)

Uuups, you are right! I know I have seen just the turn "unconvincing" in a recent article Ruben, thought it was this one. Will find a better source (and expression!). Petter Bøckman (talk) 21:32, 26 February 2012 (UTC)

What is a basal therian?[edit]

Standardly, both Eutheria and Metatheria have stem-based definitions, don't they? Eutherians are the mammals more closely related to humans than to kangaroos and metatherians are those more closely related to kangaroos. What, then, do we make of the text in the Theria subsection:

Theria ("beasts"), is the clade originating with the last common ancestor of the Eutheria (including placentals) and Metatheria (including marsupials). Although no convincing fossils of basal therians have been found (just a few teeth and jaw fragments). . . .

From the definitions, it would seem that, unless the eutherian/metatherian split was polytomous, the last common ancestor of Eutheria and Metatheria is the only therian that is neither a eutherian nor a metatherian. Are the "basal" therians restricted to this one species? If so, no fossil would be convincing. Or do some eutherians or metatherians count as basal—Juramaia, perhaps? Of Juramaia, though, much more than teeth and jaw fragments are available; we have vertebrae, ribs, clavicle, much of the right manus, etc. Why is not this a convincing fossil of a basal therian? Peter M. Brown (talk) 16:44, 26 August 2012 (UTC)

In this context I'd assume basal therian is shorthand for basal eutherians and/or basal metatherians. I agree that it's inaccurate to say no basal therians are known, using Juramaia etc. as examples. MMartyniuk (talk) 17:13, 26 August 2012 (UTC)
More likely, the reference is to fossils that cannot be reliably attributed to either Metatheria or Eutheria but are probably therian, such as Pappotherium, Tribotherium, and Kermackia. Those are all fragmentary fossils that, even if they are unlikely to represent a third polytomous branch of the Metatheria—Eutheria split, can't easily be placed on either side of it. In addition, it's fairly common to refer to more distant stem groups of Theria, such as dryolestoids, as "stem therians". Ucucha (talk) 03:24, 27 August 2012 (UTC)
Surely, to call an animal "basal" is to say something about its place in the evolution of the relevant taxon, not to comment on the paucity of relevant evidence. "Basal" is not synonymous with incertae sedis. What could be meant by calling the redlinked genera basal?
Anyhow, these genera are dated in the Cretaceous while Juramaia is Jurassic. If they are basal, surely the earlier mammal is as well, and the claim that "no convincing fossils of basal therians have been found" is incorrect.
Certainly, the dryolestoids are stem therians. The matter at hand is the usage of "basal", not "stem". Is it at all common to refer to dryolestoids as basal therians?
Peter M. Brown (talk) 15:07, 27 August 2012 (UTC)

Castorocauda and Tikitherium[edit]

I am reverting this edit to the Hair and fur subsection. (On this edit, the editor requested, "Please do not delete." Note that the edit I am reverting is a different one.)

In the edit summary of the change I have reverted, the editor pointed out that "No Jurassic animal can be ancestor of a Triassic animal". The replaced text, however, says pretty much the same thing—more specifically that, since the last common ancestor of Castorocauda and extant mammals was an ancestor of a Triassic mammaliaform, this last common ancestor must have been Triassic as well. (In principle, it could have been Paleozoic, but this is not the objection offered.)

The text that the editor provided says that Castorocauda is the sister of Tikitherium. On the contrary, Luo and Martin (2007) chart the relation between these genera as follows:







Other docodonts

Castorocauda is included in Docodonta, which is the sister of Tikitherium, but Castorocauda is not itself the sister.

Peter M. Brown (talk) 16:22, 31 August 2012 (UTC)

Discussion on title of taxon evolution pages[edit]

Hi, There is a thread here you may be interested in, about a consistent naming for articles dealing with evolution of taxa. Thanks! --Cyclopiatalk 17:08, 26 November 2012 (UTC)

Eomaia is no eutherian, so the Eutheria subsection needs updating[edit]

Most of the Eutheria subsection is devoted to Eomaia. Now that O'Leary et al. (2013) has established that Eomaia is not a eutherian, there is a need for someone with adequate knowledge of Cretaceous eutherians to revise the subsection. Peter Brown (talk) 19:43, 5 April 2013 (UTC)

Hm, interesting mix of characters, wide pelvic opening and an epipubic bone. Makes one wonder how the reproduction system actually worked. Petter Bøckman (talk) 21:09, 5 April 2013 (UTC)
I'm not sure we should treat that as really solidly established yet. There are some aspects of the O'Leary paper that are hard to make sense of. Their story makes it hard to see how you end up with the known geographic distribution of Xenarthra, Afrotheria, Laurasiatheria, and Euarchontoglires. I would agree that the text should take the new information into account, though. Looie496 (talk) 20:52, 5 April 2013 (UTC)
  • Update: I've just done a revision of that section that I hope fixes the problem, and removed the tag. Please check that it is accurate and makes sense, if you have a chance. Looie496 (talk) 21:50, 5 April 2013 (UTC)
Well, I certainly can't complain that it's inaccurate or doesn't make sense. I'm not happy, though, with devoting most of the subsection to a single genus that might not even be a member of the infraclass and then ignoring the next 60 million years of evolution, which did contain uncontroversial nonplacental eutherians, to pick up the thread in the Cenozoic. What of Ukhaatherium and Zalambdalestes, which O'Leary does allow as Cretaceous eutherians? What of Cimolestes, Gypsonictops, and the Asioryctitheria? If there were no controversy about Eomaia, ignoring all Upper Cretaceous eutherians would still be a deficiency. As it is, the only information provided about any uncontroversial nonplacental eutherian is that one genus happens to have the name "Maelestes".
This is not a deficiency I am qualified to rectify. I just now dug these taxon names up; I know nothing of the animals' anatomy. I hope that someone reading this is able to help.
What of Montanalestes and Acristatherium? The O'Leary paper doesn't mention them, but their Wikipedia articles do say that they are eutherians, though they lived prior to 91 Ma. Do we need to mention the O'Leary paper in these articles? Peter Brown (talk) 03:12, 6 April 2013 (UTC)
Well, you know a lot more about it than I do, and I edited the article anyway :-). That's how things work around here, you can't rely on other people to fix articles, you just gotta do the best you can. The main thing is to make sure the statements you add are supported by the sources you cite, and don't worry too much about all the things you don't know. Regards, Looie496 (talk) 04:40, 6 April 2013 (UTC)
The dates provided by the O'Leary study are only minimum dates, using extreme methods to ensure that they were as firm as possible. The study has also come in for a lot of criticism, including the use of molecular and morphological methods that are considered obsolete and are known to produce erroneous results. The sheer number of data points used in the study is impressive to the layman, but is a red flag to researchers, to whom it smacks of the "throw in the kitchen sink" approach.

plain-English explanation of the issues

Technical Comment on “The Placental Mammal Ancestor and the Post–K-Pg Radiation of Placentals” Science

Neither phylogenomic nor palaeontological data support a Palaeogene origin of placental mammals, Biology Letters

Zyxwv99 (talk) 18:45, 11 March 2015 (UTC)


  • O'Leary, M. A.; et al. (2013). "The Placental Mammal Ancestor and the Post–K-Pg Radiation of Placentals". Science 339 (6120): 662–667. 
The dates for temporal range are usually based on fossil evidence, not molecular clock or other inferred evidence, so even if Eutheria is probably older, the date in the taxobox should stay with the oldest known fossil specimen that can be confidently assigned to that group, with a ghosted out extension for dubiously assigned members. Dinoguy2 (talk) 19:26, 11 March 2015 (UTC)
Your comments are off-topic. This article does not have a taxobox, no taxobox has been discussed here, nor has there been any issue in this topic regarding any discrepancy between fossil and molecular dates.Zyxwv99 (talk) 13:38, 12 March 2015 (UTC)

Hippo's Closest Living Relatives are Whales[edit]

Despite its physical resemblance to a pig, the hippo’s closest living relatives are cetaceans, such as whales and porpoises.[1]

adding information to erect limb section[edit]

I feel that there is lacking information under the Erect limbs. I would like to add additional information, I am doing this in part of a college class project. Would it be appropriate to add information about limb evolution under this title? I am a newbie to this type of assignment, any help would be greatly appreciated. — Preceding unsigned comment added by Nvarade (talkcontribs) 15:39, 20 March 2014 (UTC)

Comments from Ecapelle[edit]

  • More information could be added to the section on erect limbs.
  • Limb posture could use additional information and citations.
  • Pictures on the evolution of limbs (bony structures, etc.) could really supplement the words.
  • Research and add information on Hox gene expression in mammals and how this evolved over time (like we talked about in class with snakes and their loss of limbs).

Ecapelle (talk) 04:02, 24 March 2014 (UTC)

Double jaw joint illustration[edit]

The picture illustrating the double jaw joint (squamosal-dentary and quadrate-articular) ( does not make mechanical sense, since a jaw attached to the skull in two places in the manner depicted could not rotate in the plane of the picture. It could only rotate about the line connecting the two joints, and therefore the two joints had to line up on a line perpendicular to the plane of the picture and/or be very close to one another. In fact, looking at the drawings of Morganucodontidae skulls at reference 31 in the article, especially these two, it is obvious that this was the case. It might be better to use the latter drawing as the basis for an illustration, to avoid confusion. — Preceding unsigned comment added by (talk) 08:20, 11 September 2014 (UTC)

  1. ^