First record of circinate vernation in bennettitalean foliage

摘要

The Bennettitales are Mesozoic gymnosperms with entire or pinnate leaves and complex reproductive structures. Although many forms superficially resemble cycads, particularly with regard to foliage macromorphology, bennettitaleans and cycads are not believed to be closely related at this time. Cuticular analysis of bennettitalean foliage from the Carman (Upper Triassic) of Austria reveals that Pterophyllum filicoides displays circinate vernation in the form of inwardly coiled leaf segments, which are strikingly similar to immature leaf segments seen in extant Cycas species. This discovery represents the first record of circinate vernation in the Bennettitales and may suggest that bennettitalean leaves resemble those of cycads not only with regard to macromorphology but also development.