User blog comment:Xilinoc/Ch. 542 - THE BLADE IS ME/@comment-3250274-20130619162621/@comment-3250274-20130619164257

Maybe it was filler that stated that Jushiro and Shunsui had the only dual spirit zanpakutos. I cannot find a reference. Although, I swear it was in the Soul Society arc around when they were confronted by Yama. Note: Reference #38 on Yamamoto's page. []