A new seed plant with multi-ovulate cupules from the Upper Devonian of South China

Abstract

The Late Devonian (Famennian) witnessed the diversification of early seed plants (spermatophytes), which usually possess cupulate ovules as their female reproductive organs. Previous studies have described two such plants with uni-ovulate cupules from South China. Here, a new seed plant, Calycosperma qii gen. et sp. nov., is reported from the Upper Devonian Wutong Formation of Changxing County, Zhejiang Province, China, exemplifying the first occurrence of multi-ovulate cupules in South China and eastern Asia. This plant shows cupulate ovules and associated synangiate pollen organs. Cupules are goblet-shaped with the basal two-third fused and the distal one-third dissected into 16 linear tips. Each cupule bears two ovules at the bottom, below the bases of linear tips. Synangiate pollen organs terminate isotomously divided fertile branches and consist of three to six basally fused elongate microsporangia. The considerably fused cupule of Calycosperma suggests an earlier differentiation of multi-ovulate cupules in Famennian. Calycosperma shows the largest cupules among the known Devonian seed plants, which are inferred to provide greater protection to ovules and possibly imply a hydrochoric reproduction strategy for this plant.