³1username³2JoshuaGrosse³2name³2text_default³2version³21³2ts³2982038682³2ip³2209.66.79.109³2data³2newauthor³31³3minor³30³3text³3'''Subphylum Urochordata'''

'''Subphylum Cephalochordata'''

'''Subphylum Craniata'''

The classification of vertebrates is awful.  Most of the standard groups - Agnatha, Osteichthyes, Sarcopterygii, Amphibia, Reptilia - are woefully paraphyletic and have either been abandoned or extended.  The results, though, have not settled in and so we are left with a mess.  Here's a tree to work from.

 Myxini (hagfish)
 Vertebrata
   Petromyzontiformes (lampreys)
   Various extinct forms
   Gnathostoma
     Placodermi - extinct
     Chondrichthyes (cartiligenous fish)
     Acanthodii - extinct
     Osteichthyes
       Actinopterygii (ray-finned fish)
       Sarcopterygii
         Various extinct forms
         Coelocanthamorpha
         Dipnoi (lungfish)
         Tetrapoda
           Various extinct forms
           Lissamphibia
           Amniota
             Synapsida
               Various extinct forms
               Mammalia
             Anapsida
               Various extinct forms
               Chelonia (turtles)
             Diapsida
               Various extinct forms
               Lepidosauromorpha
                 Various extinct forms
                 Squamata (lizards, snakes)
                 Sphenodontida (tuataras)
               Archosauromorpha
                 Various extinct forms
                 Crocodylomorpha (crocodiles, alligators)
                 Dinosauria
                   Various extinct forms
                   Aves (birds)
³3summary³3*³2tscreate³2982038682³2keepts³2982039266³2id³21076³2host³2cobrand.bomis.com³2revision³21³1username³2JoshuaGrosse³2name³2text_default³2version³21³2ts³2982039266³2ip³2209.66.79.109³2data³2text³3'''Subphylum Urochordata'''

'''Subphylum Cephalochordata'''

'''Subphylum Craniata'''

Vertebrate classification is awful.  Most of the standard groups are paraphyletic, and so have either been extended (B) or abandoned.  What's left is a mess that hasn't really settled into place yet.  The following is a minimal tree including most traditionally class-level groups:

 Myxini (hagfish)
 Vertebrata
   Petromyzontiformes (lampreys)
   ''Various extinct forms''
   Gnathostoma
     Placodermi ''- extinct''
     Chondrichthyes (cartiligenous fish)
     Acanthodii ''- extinct''
     Osteichthyes B
       Actinopterygii (ray-finned fish)
       Sarcopterygii B
         ''Various extinct forms''
         Coelocanthamorpha
         Dipnoi (lungfish)
         Tetrapoda
           '''Various extinct forms''
           Lissamphibia
           Amniota
             Synapsida
               '''Various extinct forms'''
               Mammalia
             Anapsida
               '''Various extinct forms'''
               Chelonia (turtles)
             Diapsida
               '''Various extinct forms'''
               Lepidosauromorpha
                 '''Various extinct forms'''
                 Squamata (lizards, snakes)
                 Sphenodontida (tuataras)
               Archosauromorpha
                 '''Various extinct forms'''
                 Crocodylomorpha (crocodiles, alligators)
                 Aves (birds)
³3minor³31³3newauthor³30³3summary³3*³2tscreate³2982038682³2keepts³2982039315³2id³21076³2host³2cobrand.bomis.com³2revision³22³1username³2JoshuaGrosse³2name³2text_default³2version³21³2ts³2982039315³2ip³2209.66.79.109³2data³2newauthor³30³3minor³31³3text³3'''Subphylum Urochordata'''

'''Subphylum Cephalochordata'''

'''Subphylum Craniata'''

Vertebrate classification is awful.  Most of the standard groups are paraphyletic, and so have either been extended (B) or abandoned.  What's left is a mess that hasn't really settled into place yet.  The following is a minimal tree including most traditionally class-level groups:

 Myxini (hagfish)
 Vertebrata
   Petromyzontiformes (lampreys)
   ''Various extinct forms''
   Gnathostoma
     Placodermi ''- extinct''
     Chondrichthyes (cartiligenous fish)
     Acanthodii ''- extinct''
     Osteichthyes B
       Actinopterygii (ray-finned fish)
       Sarcopterygii B
         ''Various extinct forms''
         Coelocanthamorpha
         Dipnoi (lungfish)
         Tetrapoda
           ''Various extinct forms''
           Lissamphibia
           Amniota
             Synapsida
               ''Various extinct forms''
               Mammalia
             Anapsida
               ''Various extinct forms''
               Chelonia (turtles)
             Diapsida
               ''Various extinct forms''
               Lepidosauromorpha
                 ''Various extinct forms''
                 Squamata (lizards, snakes)
                 Sphenodontida (tuataras)
               Archosauromorpha
                 ''Various extinct forms''
                 Crocodylomorpha (crocodiles, alligators)
                 Aves (birds)
³3summary³3*³2tscreate³2982038682³2keepts³2982039893³2id³21076³2host³2cobrand.bomis.com³2revision³23³1username³2JoshuaGrosse³2name³2text_default³2version³21³2ts³2982039893³2ip³2209.66.79.109³2data³2text³3'''Classification'''

The traditional classification of vertebrates is a mess, with a wide variety of paraphyletic groups that have either been abandoned or extended (here marked B).  Unfortunately, no particularly standard system has settled in to replace it; the problem is there have been too many adaptive radiations.  For now, here is a minimal tree of living forms including most traditionally class-sized groups:

 Urochordata
 Cephalochordata
 Craniata
   Myxini (hagfish)
   Vertebrata
     Petromyzontiformes (lampreys)
     Gnathostoma
       Chondrichthyes (cartiligenous fish)
       Osteichthyes B
         Actinopterygii (ray-finned fish)
         Sarcopterygii B
           Coelocanthamorpha
           Dipnoi (lungfish)
           Tetrapoda 
             Lissamphibia (frogs, toads, salamanders)
             Amniota
               Mammalia
               Chelonia (turtles)
               Squamata (lizards, snakes)
               Sphenodontida (tuataras)
               Crocodylomorpha (crocodiles, alligators)
               Aves (birds)

Information on characteristics of each group and a more detailed classification thereof should probably go under its headline - eg details of skeletal system and listing of jawless fishes under Vertebrata.
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