The monophyly of Ecdysozoa, which comprise molting phyla, has received strong support from several lines of evidence. However, due to the lack of sequence data from "minor" phyla, the internal relationships of Ecdysozoa are still contended. We generated expressed sequence tags from a priapulid (penis worm), a kinorhynch (mud dragon), a tardigrade (water bear) and five chelicerate taxa by 454 trancriptome sequencing.