Abstract
Obirafructus kokubunii gen. & sp. nov. (family Incertae Sedis; order Saxifragales) is proposed based on a permineralized reproductive axis bearing at least 42 spirally arranged follicles. No bracts, perianth, stamens, nor their vestiges are present on the axis or the follicle stalk. It is therefore part of single flower and not an inflorescence. The axis is 57 mm long, woody, and contains scalariform perforations on the vessel walls. The flower is inferred to be unisexual, as in Cercidiphyllaceae (Saxifragales). The lower part, which may have borne male organs, is missing. The follicles consist of a conduplicate carpel with marginal placentas alternately bearing 90–100 seeds in two rows. The follicle has dorsal and ventral ridges and the ventral suture dehisces at maturity. The carpel probably has an apical style and stigma at anthesis. The ovules are bitegmic, anatropous. A nucellar cap plugs the micropyle. The seeds are slightly winged, which may represent hydrochory and/or anemochory. Based on these features, Obirafructus kokubunii probably inhabited a fluvial plain. The follicle clusters of Joffrea and Jenkinsella (fossil Cercidiphyllaceae) apparently resemble those of O. kokubunii; but they represent inflorescences. Obirafructus kokubunii adds a new morphotype to the past diversity of basal Saxifragales.
