Nübler-Jung and Arendt argue that the principal innovation in the chordate lineage was the obliteration of the mouth on the neural side (as in hemichordates, arthropods, and annelids) and the development of a new mouth on the non-neural ventral side.
Nübler-Jung e Arendt argumentan que a principal innovación na liñaxe dos cordados foi a obliteración da boca no lado neural (como en hemicordados, artrópodos, e anélidos) e o desenvolvemento dunha nova boca no lado ventral non neural.