 The researchers that made the discovery believe that the "Saccorhytus" is a common ancestor to all previously-known deuterostomes.Fossils of one major deuterostome group, the echinoderms (whose modern members include sea stars, sea urchins and crinoids), are quite common from the start of Series 2 of the Cambrian, .The Mid Cambrian fossil "Rhabdotubus johanssoni" has been interpreted as a pterobranch hemichordate.