"Diadectes" is the best known diadectid, with six species named since its initial description. In a 2005 phylogenetic analysis, most species of "Diadectes" formed a clade with "Diasparactus zenos". Two species, "Diadectes absitus" and "Diadectes sanmiguelensis", were placed in more basal positions. These species possess primitive characteristics found in non-diadectid forms, such as "Limnoscelis" and "Tseajaia". Because "D. absitus" and "D. sanmiguelensis" were placed far from other species of "Diadectes" in the analysis, their assignment to the genus was questioned. The same results were found in the 2010 analysis. Two new genera were erected in the study to include "D. abstus" and "D. sanmiguelensis". "D. sanmiguelensis", the more basal of the two forms, was placed in the new genus "Oradectes". "D. abstus" was renamed "Silvadectes".