Talk:Prototheria

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[edit] prototheria and australosphenida -- what's the difference

I'm not a zoologist or anything so I don't know what the story is here. Do the terms "prototheria" and "australosphenida" have different definitions? Are they synonymous, and if so which is used more in the scientific literature?

Template:Mammals does not recognize "prototheria" as a subclass; it uses "australosphenida" instead.

Perhaps the best solution would be to merge the two articles, and then indicate what the differences are, if any, as well as which context each term is used in.

See also Talk:Monotreme#Australosphenida = Prototheria?. --Mathew5000 22:18, 24 August 2007 (UTC)

Prototheria used to include everything that was a mammal but wasn't a therian — i.e. not just monotremes but also fossil groups like triconodonts, morganucodonts, docodonts and multituberculates. Almost nobody now seems to think this is a natural grouping — some of the 'prototherians' are more closely related to therians than they are to other 'prototherians'. But there's wide disagreement on which ones are closest to Theria and what the exact branching order is. The only thing that is clear is that the old subclass Prototheria can no longer be sustained on cladistic grounds, and should either be abandoned or redefined. The nucleus around Monotremata could be called Prototheria sensu stricto or Australosphenida, according to taste.

If you check out Mammal classification, you'll find that different workers have different schemes. One that isn't mentioned there is Michael J. Benton, Vertebrate Palaeontology (3rd ed., 2005, ISBN 0-632-05637-1) which does assign a rank for Australosphenida, as follows:

• Class Mammalia
  • Subclass Mammaliaformes
    • Infraclass Holotheria
      • Superdivision Australosphenida
      • Superdivision Theriimorpha (includes Triconodonta, Multituberculata & Theria)

Until higher-level mammalian taxonomy settles down, my advice would be to enter Australosphenida in the taxobox as 'unranked'. I would definitely NOT make Monotremata or Australosphenida subordinate to Prototheria, or use Prototheria at all on classification tables and taxoboxes (it means different things to different people). That might change if taxonomists were to reach agreement on a new definition.

Since the name 'Prototheria' could be on the way out but 'Australosphenida' hasn't yet fully established itself, the preferable course might be to merge both articles into Monotreme and deal with it there. Hope I've been of some help and haven't left you more confused than before! Gnostrat 01:09, 30 August 2007 (UTC)

Thanks -- that's a good explanation. I think the Wikipedia article (prototheria) needs to be rewritten to explain that. It’s unsatisfactory the way this article begins by describing prototheria as ‘the subclass’ to which monotremata belongs, if in fact there is currently some dispute within the literature as to whether the term should be used at all, and if so how it should be defined. Actually I have found that a lot of Wikipedia's articles on mammalian taxons are mutually contradictory because different articles are using different scientists’ proposals for classification, but each article is written as if it were absolute fact, rather than one competing proposal (or sometimes a historical usage). Merging the article prototheria into the article monotremata would be one option, although it might be better to leave prototheria as its own article, but instead of defining it as a subclass of mammals, define it as a taxonomic term in relation to mammals, which historically was used to refer to a subclass containing monotremata although the latest evidence indicates that usage is unsatisfactory. Or something like that. --Mathew5000 07:07, 30 August 2007 (UTC)

Those of us who lie awake at night counting clades would sleep easier if we had a settled classification, but these things are only hypotheses after all, and science is about hypothesis testing and dumping. Nevertheless it ought to be possible to devise a robust 'skeleton' classification for use on taxoboxes, selecting only nodes which are unlikely to be controverted, while leaving the contentious ones for discussion in the articles. But the current system really needs an overhaul in any case, to drag it into the cladistic age. I mean, monophyletic Aves and Mammalia side by side with paraphyletic classes Sauropsida and Synapsida?? (Sure, a lot of taxonomists are still doing it but it's unsustainable in the long run and Wikipedia should go with the avant-garde.) And who calls marsupials and placentals subclasses any more?? Good grief!

I've some other articles that need fixing up, then I'll see what I can do with Prototheria and Australosphenida, if nobody else has got round to them first. Though it's one thing to condense years of reading this stuff into a few paragraphs of explanation, and quite another thing to track down specific sources for definitions and groupings. Gnostrat 19:34, 31 August 2007 (UTC)

Thanks Gnostrat. When you have time, perhaps you could also look at Triconodonta. The current version of that article has some odd wording, stating: Many other extinct groups of Mesozoic mammals are now placed just outside Mammalia proper, at least according to the cladistic definition of the word "mammal". I assume it's trying to say that many fossils which had previously been considered extinct nontherian mammals are now classified as not being mammals at all. If that's what it means, it is badly worded because within the same sentence it calls those fossils mammals and then says they are not mammals. --Mathew5000 22:27, 1 September 2007 (UTC)

You assume correctly, and it does need re-wording, but there's a more serious problem with the sentence you quoted. Currently, we have disagreement on the best way to define Mammalia and, once again, an article which treats one contentious proposal as "THE cladistic definition". I'll bring this up on the Triconodonta talk page soon. Heck, I'll probably fix it first and explain it afterward. Gnostrat 00:52, 8 September 2007 (UTC)

Great; thank you. --Mathew5000 06:38, 8 September 2007 (UTC)