Palæos:		Arthropoda
METAZOA		EuArthropoda

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Euarthropoda

ARTHROPODA  
|--Trilobita
`--Euarthropoda
   |--Myriapoda  
   |  `--Chilopoda  
   `--+--Chelicerata  
      |  `--Arachnida  
      `--Pancrustacea  

The Euarthropoda were originally conceived as "Schizoramia": those arthropods that possess branched appendages as opposed to those with only a simple unbranched limb ("uniramous").  That arrangement looked like this:

<==o ARTHROPODA
   |--o SCHIZORAMIA 
   |   |-- CHELICERATA  
   |   `-- CRUSTACEA 
   `--o ATELOCERATA/UNIRAMIA
      |-- MYRIAPODA 
      `-- HEXAPODA 

The above cladogram shows the Schizoramia as sister group to the Myriapoda + Hexapoda (see rival phylogenies).  However, we follow the "Pancrustacea" school of thought, which unites hexapods and crustaceans.  To provide some stability to the region, it is useful to have a clade which unites all four living branches of the arthropods.  This is it.  

Phylum Schizoramia Hou & Bergström, 1997

Many forms that occur in the Chengjiang lagerstätten have been described by Jan Bergström and Hou Xianguang (the discoverer of the Chengjiang fauna), who follow an intuitive "key-character" approach.  In their monograph, Hou & Bergström present the following subdivisions of the Schizoramia, including two new superclasses, the Proschizoramia and the Lamellipedia:

Superclass: Proschizoramia
          Class: Yunnanata
          Class: Paracrustacea
          Class: Megacheira 
          Class: Sanctacaridea

Superclass: Crustaceomorpha 
          Class: Pseudocrustacea (incl. Agnostida)
          Class: Crustacea

Superclass: Lamellipedia 
          Class: Marellomorpha 
          Class: Artiopoda
          Class: Trilobita 
          Class: Chelicerata 

Note that much of this arrangement is not accepted by many workers in this field

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