of the three orders to living millipede groups. Some authors place Arthropleuridea within the Chilognatha, as a sister group to all living Chilognathan millipedes (Pentazonia + Helminthomorpha). An alternate hypothesis breaks up the subclass: placing the orders Arthropleurida and Eoarthropleurida within the basal Penicillata (as sister to the living Polyxenida), and leaving only Microdecemplicida as a sister group to the living Chilognatha. Under this hypothesis, Arthropleuridea would be paraphyletic. See also Archipolypoda, another extinct group of millipedes including the earliest known air-breathing animal Euthycarcinoidea, a group of enigmatic arthropods that may be ancestral to myriapods Colonization of land, major evolutionary stages leading to terrestrial organisms References Millipede taxonomy Arthropod subclasses Prehistoric arthropod taxa Carboniferous myriapods Devonian myriapods Silurian myriapods Pridoli first appearances