New Classification (Class Reptilia)

[Ken Kinman]

Dear All,
      I have stated for several years my plans to eventually dismember Order Thecodontiformes, and that day has come.  It has been split into four taxa---Proterosuchiformes, Suchiformes, Plesion Scleromochlus, and the base of Dinosauriformes.  Note also that I no longer split dinosaurs into two separate orders (which should make a lot of dinosaur workers happy).

     And as I promised Curtis Clark, I am including three intermediate taxa (the third being a "crown group" Archosauria).  This arrangement is remarkably reminiscent of my tripartite classification of Diptera (where Brachycera holds a position similar to that of Diapsida here).  Order Testudiniformes (turtles) is still incertae sedis (see notes at end for more information on that).  I am relatively pleased with this revised classification, considering the uncertainties of reptilian phylogeny and it being at the epicenter of strict cladism (and thus a nightmare of conflicting and superfluous clade names).
         --- Cheers,
                Ken Kinman
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CLASS REPTILIA%%
    1  COTYLOSAURIA% (primitive reptiles)
          1  Diadectiformes
          2  Pelycosauriformes%
         _a_ Therapsiformes%
         _a_ {{Mammalia}}
          3  Mesosauriformes
          4  Millerettiformes
          5  Procolophoniformes
          ?  Testudiniformes (note**)
          6  Plesion Captorhinidae
          7  Plesion Protorothyrididae
          8  {{Diapsida}} (= Lepidosauria
                     plus Archosauria)

     _1_ LEPIDOSAURIA% (basal diapsids)
          1  Araeosceliformes
          2  Plesion Coelurosauravus
          3  Plesion Apsisaurus
          4  Younginiformes
          5  Eolacertiliformes
          B  Sphenodontiformes
          C  Squamatiformes
          6  Ichthyosauriformes
          B  Sauropterygiformes
          ?  Thalattosauriformes
          7  Choristoderiformes
          8  Trilophosauriformes
          B  Rhynchosauriformes
          9  Protorosauriformes
         10  Proterosuchiformes%
         _a_  {{Archosauria}}

    _1_ ARCHOSAURIA% (ruling reptiles)
          1  Suchiformes% (basal crurotarsans)
         _a_  Crocodyliformes
          2  Plesion Scleromochlus
          B  Pterosauriformes
          3  Dinosauriformes%
         _a_  {{Aves}}

_a_ CLASS AVES

_b_ CLASS MAMMALIA

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    **NOTES:  The position of Testudiniformes (turtles) has become highly contentious in recent years.  I am leaving turtles in Cotylosauria for now, since they have been allied with Captorhinidae and also two different groups of Procolophoniformes.  Some workers believe turtles are "secondarily anapsid" members of Diapsida, perhaps allied with Sauropterygiformes.  I have no strong feelings about this one way or the other (although a diapsid ancestry for turtles would be very thought provoking).

     And for those of you wondering why Order Diadectiformes is included at the base of Reptilia, I made that decision in March 2002, announced on DML (Dinosaur Mailing List).  Some of the reasons I offered at that time were:   "The diadectiforms had a breathing system much more like reptiles than amphibians, they almost certainly laid primitive amniotic eggs, and there are several other morphological characters that also support this division.  The amphibian Family Solenodonsauridae will now be regarded as the sister group of Amniota (thus making Amniota equivalent to the cladistically defined Cotylosauria Gauthier et al., 1988 and/or Anthracosauria sensu Laurin, 1998)."

     Gauthier's greatly expanded clade Cotylosauria would even include birds, which is just plain weird.  Birds are NOT cotylosaurs unless you define them that way (and Phylocoders are going to get an earful if they formally define Cotylosauria that way later this year).  So please don't do it.  It would be advisable to go with Anthracosauria (or a slightly expanded Amniota).  I believe that someone also proposed Amniotaformes for this clade, but I don't like that one either.  Brace yourselves for even more clade names in the next few years.  <yikes>