Talk:Mammaliaformes

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Most taxa are extinct, aren't they? The sign is missing everywhere. — Preceding unsigned comment added by 5.204.104.126 (talk) 12:00, 23 June 2014 (UTC)

Picture

OK, I'm still laughing, so bear with me here...why is there a picture, in this article regarding mammaliaforms, of a hedgehog? Does someone have some news to share with the scientific community regarding this creature, formerly thought to be a modern placental mammal? --Kaz 18:14, 7 March 2006 (UTC)

Why not? All living mammals are also Mammaliaformes. I chose a hedgehog because its cranial morphology and molar pattern are fairly similar to the ancestral state. It definitely is a modern placental mammal (and therefore a mammaliform). I'm not really catching the joke. --Aranae 21:54, 7 March 2006 (UTC)

It's best to represent a clade by a primitive representative, one that possesses features (especially synapomorphies) shared by all members of the clade. Ideally we'd show a fossil from close to the root of the clade. However, if the hedgehog is the best we can do, then we need an explanation along the lines you give in the paragraph above. Gdr 22:38, 13 March 2006 (UTC)

Right now, the mammal page has a lion image, insect has a honeybee, rodent has a capybara, primate has a baboon, odd-toed ungulate has a zebra, even-toed ungulate has a rocky mountain goat, mollusk has a squid, etc. I would argue that all of those display very derived characters compared to other members of the group. The consensus seems to be that anything in the clade will do for a taxobox image. I would be happy to see any other mammaliaform take the place of the hedgehog image, I just don't see the point in having no image when there are so many to choose from. Right now, the only non-mammal mammaliaform that currently has an image is Castorocauda, which would be fine (perhaps better) if there's no problem claiming fair use for that one. Otherwise we're stuck with a mammal. There are a few early fossil mammals, Repenomamus, Fruitafossor, Deltatheridium (more potential copyright problems), and Leptictidium (copyright?). Any interest in any of these? I don't care if it's a human, zebra, or Morganucodon, I just think there should be an image. --Aranae 23:15, 13 March 2006 (UTC)

I think the articles you listed need better pictures too! Copyright concerns aside, I think the Castorocauda picture would be better than the hedgehog. But the hedgehog would be OK with a note its that "cranial morphology and molar pattern are fairly similar to the ancestral state". Gdr 23:37, 13 March 2006 (UTC)

I'm adding the Castorocauda image. It's been used elsewhere in a similar format and, if copyright doesn't allow it, we can always change it later. --Aranae 23:56, 13 March 2006 (UTC)

The Castorocauda image was replaced with one of Adelobasileus; I have changed it back. According to the definition in Rowe 1988, Mammaliformes is limited to the the last common ancestor of Morganucodontidae and (Crown) Mammalia and all its descendants, a definition that rules out Adelobasileus. Recent writers, e.g. Sues and Fraser 2010, repeat this definition. Though Mikko Haaramo does include this genus, it is preferable to use Castorocauda, uncontroversially a mammaliaform.

Seus and Fraser also differ from Haaramo in that they explicitly exclude Sinoconodon. Rowe does as well: Rowe, T. B. (1993). "Phylogenetic systematics and the early history of mammals". In F. S. Szalay; et al. (eds.). Mammal Phylogeny. Vol. 1. Springer-Verlag. pp. 129–145. ISBN 0387978542. {{cite encyclopedia}}: Explicit use of et al. in: |editor= (help); Unknown parameter |separator= ignored (help)

Peter M. Brown (talk) 17:44, 9 January 2012 (UTC)

Taxonomy

Ok, as I'm not part of wikiproject mammals I'm not going to force this system or anything, but I'd liek to point out that in most pages dealing with taxonomy, especially in the reptile sections, we've been using a classification system based on evolutionary taxonomy, rather than pure cladistic or pure Linnean. Basically, taxa are given regular linnean ranks based on agreed upon standards. Lower taxa can contain other "major" (usually crown-group or similar) higher taxa based on agreed-upon cut-off points. For example, the Order Therapsida (class Synapsida) contains the class Mammalia even though the later is higher rank. This has worked very well as a comprimise between the two camps, and provides added usefulness to the average reader by keeping the taxoboxes Linnean (they really are useless from a purely cladistic point of view, unless they include hundreds of unranked taxa). This also helps keep the taxonomy and taxoboxes standard across entries, which makes the animal pages more user friendly.

In standard Linnean practice, Mammaliaformes is a subclass within Mammalia. In evolutionary taxonomy, which tries to take the best of Linnean and phylogenetic taxonomy, it would be either a subclass or superorder of Class Synapsida, since phylogenetically they are not true mammals, and more information is conveyed by keeping them as mammal-like synapsids. Anyway, just a suggestion.Dinoguy2 14:55, 20 April 2006 (UTC)

We're almost one year later and I decided to follow your suggestions, something I already did earlier this monthDaMatriX 19:46, 11 April 2007 (UTC)

Mammal vs. Almost Mammal

Hi, all, this is an interesting article. But as a moderately informed layperson, I'm finding it a little hard to follow. It might help if an expert could lay out more clearly what characteristics separate mammals from other non-mammal mammaliaformes. Thanks for reading this. JamestownArarat 01:09, 5 October 2007 (UTC)

That would depend on which of the several competing definitions of Mammalia you are using. 85.8.12.78 (talk) 10:50, 12 May 2008 (UTC)

Misspelled title

I believe the correct spelling is Mammaliformes. At a guess I'd say that the article is following Michael Benton's Vertebrate Palaeontology where an extra letter creeps in, but it's clearly an error. Following standard Latin practice, you would add the termination -formes directly to the stem vowel -i-. This is the procedure with every order of fishes and birds. In Nature, it's spelled Mammaliformes in every paper where I've noticed it. Gnostrat (talk) 23:06, 19 May 2008 (UTC)

Morganucodonta

The cladogram in the article seems to exclude the Morganucodonta. Is this how it's supposed to be (if so, why?) or has it been a mistake? DaMatriX (talk) 16:53, 25 July 2009 (UTC)

Definition

Kielan-Jaworowska et al. have not defined Mammaliaformes

Kielan-Jaworowska, Cifelli, and Luo 2004 (henceforth KCL) cannot appropriately be cited as the source for a definition of Mammaliaformes, as this work does not provide such a definition. What the authors do is to define Mammalia, using the definens repeated in the Wikipedia article; this is not the same thing. They do go on to claim that their definition is equivalent to that of Mammaliaformes sensu Rowe 1988, but that does not transform their definition of Mammalia into a definition of Mammaliaformes. I have accordingly deleted the reference to the 2004 work.

If the definitions were, in fact, equivalent, we could replace KCL by Rowe 1988 as the source for this definition. They are not equivalent, however. Rowe defines Mammalia as "comprising the most recent common ancestor of living Monotremata (Ornithorhynchidae and Tachyglossidae) and Theria (Marsupialia and Placentalia) and all of its descendants" and then defines Mammaliaformes as comprising "the last common ancestor of Morganucodontidae and Mammalia and all its descendants." This excludes Sinoconodon, a fact that Rowe recognizes in a 1993 paper while reaffirming his 1988 definition. In KCL's formulation, Sinoconodon is included in Mammalia by definition.

KCL makes mention of Figure 4 in Rowe's 1988 paper, which does reflect his opinion, at the time, that Sinoconodon was included in Mammaliaformes as he defined it. Even if Rowe is interpreted as intending this figure to be taken as an alternate definition, an interpretation he nowhere suggests, that definition is not equivalent to KCL's definition of Mammalia, as the figure does not include the Docodonta.

Rowe's 1993 paper is Rowe, T. B. (1993). "Phylogenetic systematics and the early history of mammals". In F. S. Szalay; et al. (eds.). Mammal Phylogeny. Vol. 1. Springer-Verlag. pp. 129–145. ISBN 0387978542. {{cite encyclopedia}}: Explicit use of et al. in: |editor= (help); Unknown parameter |separator= ignored (help)

Peter M. Brown (talk) 18:47, 11 January 2012 (UTC)

By Rowe’s definition, Adelobasileus and Sinoconodon are not mammaliaforms

I have changed the definition of Mammaliaformes to one equivalent to that provided in Rowe (1988), where the taxon is first defined. Mammaliaformes comprises "the last common ancestor of Morganucodontidae and Mammalia and all its descendants," with Mammalia defined as the mammal crown group. This excludes Sinoconodon and Adelobasileus. Inasmuch as peer-reviewed papers like Soares et al. (2011) have characterized these two genera as mammaliaforms, further discussion of my choice is necessary.

Rowe introduced the term "Mammaliaformes" in order to accommodate some of the extinct animals that were traditionally called "mammals" but fell outside the crown mammals, the clade to which he limited the term "Mammalia". He was well aware that, though his definition encompassed some animals that were outside the crown but to which "Mammalia" had often been applied, it left some out: in particular, he considered that the Haramiyida lay outside of the Mammaliaformes. A consistent adherent of phylogenetic taxonomy, he argued that his phylogenetic definitions are to be preferred to the traditional trait-based definitions.

Though his 1988 cladogram shows Sinoconodon as a mammaliaform, he soon concluded otherwise. The cladogram in a 1993 paper, cited in the subsection above, exhibits his revised view that Sinoconodon is less closely related to crown mammals than are the Morganucodontidae and that, therefore, this genus is not included in Mammaliaformes. His shift exhibits a central feature of the phylogenetic orientation in taxonomy, one that advocates of this approach have put forward as an important virtue: if a taxon is defined phylogenetically, its content may change with the progress of science, but the definition is insensitive to such shifts. There is a clear contrast between this orientation and that of Benton, who argues in a 2000 paper that it is usually more important to preserve the membership of a taxon than its definition.

In a paper that appeared in 1993, Spencer Lucas and Zhe-Xi Luo reaffirmed the position of Sinoconodon as less closely related than Morganucodon to monotremes and therians and added Adelobasileus as another genus, one that they termed mammalian, that was also less related. On this view of the relationships, one now generally accepted, Adelobasileus is not a mammaliaform in Rowe's sense. More recent writings, for example that of Bonaparte et al. (2005), also presuppose that Adelobasileus is not a mammaliaform. In a 2011 paper, Rowe reiterates that Morganucodon is the basal-most member of Mammaliaformes.

As I note above, writers like Soares have referred to Adelobasileus and Sinoconodon as mammaliaforms. Though I can cite no relevant secondary sources, I suspect that this usage arose as follows. Under the influence of the phylogenetic systematists, it became unfashionable in some circles to classify as mammals animals that were not in the crown group. Those on this bandwagon who respected the detailed studies of authors like Lucas and Luo but scorned their usage of "Mammalia" therefore sought some other term that was less inclusive than "Eucynodontia" to characterize Sinoconodon and Adelobasileus. Though Rowe's term "Mammaliamorpha" might have served, they adopted "Mammaliaformes" for the purpose. Indirectly, they were including animals in Mammaliaformes on just the sort of trait-based basis that they officially rejected: the inclusion was a consequence of others' assignment of the animals in question to Mammalia based on traits.

To the practitioner of trait-based taxonomy, it is pointless to apply the term "Mammaliaformes" to Adelobasileus, Sinocodon, or any other animal; "Mammalia" will do just fine. To the adherent of phylogenetic taxonomy, applying the term to these genera would be incorrect; the meaning was fixed once and for all in 1988 and nothing that has happened since has provided a reason for it to change. If anyone reading the present comment is aware of yet another approach, one that does provide a rationale for assigning these genera to Mammaliaformes, please do explain below; such an approach does need to be mentioned in the article.

Peter M. Brown (talk) 02:47, 7 February 2012 (UTC)

A strange paragraph

In the section Mammaliaformes in life is the paragraph:

Mammaliaforms have several common structures. Most importantly, mammaliaforms have highly specialized molars, with cusps and flat regions for grinding food. This system is also unique to mammals, although it seems to have evolved convergently in stem-mammals multiple times.

If the specialized molars referred to are indeed common to all mammaliaforms, then they are a synapomorphy of the clade, not teeth that evolved convergently in different mammaliaform subgroups. If such molars did evolve convergently in some group, therefore, this group cannot be contained in the mammaliaforms. These non-mammaliaforms must be mammals, though, since it is asserted that such molars are unique to mammals. What mammals are not mammaliaforms? Adelobasileus and Sinoconodon come to mind—they have been called mammals and, as I argue in the preceding section, they are not mammaliaforms—but there are not a whole lot of cases of this sort. Even if mammalian molars did evolve convergently in these genera, rather more instances are needed to flesh out the claim that the convergent evolution happened "multiple times."

The problem is somewhat alleviated if "common structure" means only a structure that commonly occurs. The first sentence could be modified to make this clear. It would then be necessary to replace "mammaliaforms" by "some mammaliaforms" in the second sentence, which would rather weaken the force of "Most importantly".

Note, in any case, that "mammal" cannot mean "crown-group mammal" in the third sentence; as no stem-group mammal is a crown-group mammal, no stem-group mammal can have a characteristic that is unique to crown-group mammals. Since, as the article notes, the term "mammaliaform" is principally used by writers who do use "mammal" to mean "crown-group mammal", it should be made clear that it is used here in another sense.

I do not want to delete the whole paragraph. It seems to be saying something worthwhile about molars. Any idea what that might be?

Peter M. Brown (talk) 17:12, 15 March 2012 (UTC)

Mammaliaformes are just mammals. That's why it's so confusing. People are trying to force them into some weird proto-mammal category with no sensible criteria. 72.73.109.8 (talk) 15:26, 20 January 2014 (UTC)

Synapsids & mammaliaformes - what's the difference?

It looks to me (a non-expert) that this is a subset of the synapsids. Could that be made clearer to the casual reader, perhaps explaining where the mammaliaformes diverge from other synapsids? --Chriswaterguy talk 01:53, 20 October 2012 (UTC)

I don't see a point in bringing in the synapsids, since we can't assume that the casual reader has ever heard of the group. Synapsida is just one of six superior taxa listed in the taxobox; why distinguish mammaliaforms from other synapsids rather than from, for example, other prozostrodontians? from other teleostomes? Peter Brown (talk) 02:35, 20 October 2012 (UTC)

Someone who understands taxonomy will see that Mammaliaformes is a sub-clade of Synapsida. In other words, all Mammaliaforms are Synapsids, while not all Synapsids are Mammaliaforms. Therefore separate, dedicated articles “Synapsid” and “Mammaliaformes” are more than justified.--Solomonfromfinland (talk) 18:44, 18 March 2016 (UTC)

Sinocodon; Mammaliamorpha

This article is inconsistent on whether Sinocodon was a member of Mammaliaformes. The following passage suggests that it was: “In particular, trait-based taxonomy generally includes Adelobasileus and Sinoconodon in Mammalia, though they fall outside the Mammaliaformes definition.” However, the cladogram below places Sinocodon just outside the Mammaliaformes. Meanwhile, the article “Sinocodon” implies that Sinocodon was a member of Mammaliaformes: “Although the animal is closely related to Morganucodon, it is regarded as the most basal of the mammaliaforms.” Likewise, the article “Tritylodontidae” has a cladogram which places Sinocodon within Mammaliaformes .

Also, since both this article and the article“Sinocodon” mention the name “Mammaliamorph(a)”, which this article describes as a somewhat more inclusive clade than Mammaliaformes, I suggest a dedicated article titled “Mammaliamorpha”. (Currently, “Mammaliamorpha” redirects to “Mammaliaformes”.)--Solomonfromfinland (talk) 18:39, 18 March 2016 (UTC)

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