I am looking for good contemporary sites (or cites, or explanations by knowledgeable people) regarding the cladistic higher-taxon taxonomy of two groups: the amniotes and the placental mammals.
As most people interested in paleontology know, the former classification divided reptiles (along with birds and mammals) into the Anapsids (cotylosaurs and turtles) with no foramen, the Synapsids with only a temporal foramen (pelycosaurs, mammal-like reptiles, and mammals), the Euryapsids with an upper foramen (largely marine Mesozoic reptiles), and the Diapsids with both temporal and upper foramina. The Diapsids were then broken down into Archosaurs (pterosaurs, dinosaurs, birds, and crocodiles) and Lepidosaurs (snakes, reptiles, and tuatara), on grounds I didn’t understand, each group of course including extinct families and orders. It would appear that modern cladistics suggest that not ancestral amniotes but the paleontologists classifying them had holes in their head!
And there are something like 30 orders of placental mammal, counting extinct groups like Tillodonts, Condylarths, and Litopterns. But as of the last material I have, it seems that asking any ten paleomammalogists will give you ten different groupings of those orders into superorders or cohorts.
So anyone who happens to have access to a good authoritative modern analysis of these groups is invited to link to it or discuss it.
This certainly isn’t the final word on the relationships, but I’ve found The Tree of Life (it’s their mammal page, showing the relationship of the Eutherians to other mammals) site very helpful in clarifying relationships and pretty well supported and up-to-date.
No doubt someone with a greater knowledge of phylogeny will come along soon with other sources, many of which will contradict the site I just posted.
Oh, crap. Scratch my comment about “up to date” - I just noticed the site I link to mentions that the tree hasn’t been updated since 1995, and refers you to the references below (many of which are more recent than 1995) for more current information.
For what it’s worth, cladists don’t define “reptiles” that way (at least, none that I’m aware of). Amniota consists of two groups: the Sauropsida and Synapsida. Within the Sauropsids, we find Anapsids (turtles, etc.) and Eureptilia (“proper” reptiles). Sauropsida, then, represents what a cladist would consider more or less equivalent to the Linnaean Class Reptilia (with the exception that Aves is to be found nested deep within the Eureptilia). Diapsids are a subset of Eureptilia (pretty much, all Eureptiles excluding the Protorothyrididae). The old “Euryapsida” is something of a problem; some researchers recognize it, some don’t. The old defintinon of “ichthyosaurs, plesiosaurs, and their allies” doens’t hold up any more, since, as it turns out, ichthyosaurs and plesiosaurs aren’t really closely related (at least, not close enough to constitute a monophyletic group). Plesiosaurs are found within the Sauria (Eureptilia>Diapsida>Neodiapsida>Sauria>Lepidosauromorpha>Sauropterygia), while Ichthyosauria is a sister clade to Sauria.
As far as up-to-date analyses of assorted reptile and mammal groups…I dunno. I tend to use the Palaeos website for most of my online taxonomic needs. They tend to spell out where they differ from other authorities, and give alternative classifications for particualrly contentious groups, as well as links to other sites discussing various groups. It’s a good place to start, at least.
