A new Trapa from the middle Miocene of Zhangpu, Fujian, southeastern China

The Zhangpu biota from the middle Miocene, located in the Fotan Group of Fujian, southeastern China, is renowned for being an ancient megathermal seasonal rainforest ecosystem. This paper presents the description of a new species of Trapa (Trapoideae, Lythraceae) based on the examination of well-preserved fossil fruits from the Fotan Group, adding to knowledge of the freshwater plant diversity within the Zhangpu biota. Trapa haominiae n. sp. has medium-sized fruits with four horns that are more or less similar in form and size. The horns are expanded nearly horizontally or slightly upward pointing, with a spiny, harpoon-like apex bearing retrorsely barbed spines. Trapa haominiae is among the earliest, unequivocal fossil record of Trapa in the world. The fruit morphology of T. haominiae confirms a close relationship between Trapa and Hemitrapa. The discovery of the present fossil, along with horned fruits of Hemitrapa zhangpuensis, and the pollen grains of Sporotrapoidites weiheensis and S. erdtmanii from the same geological layer, indicates that the Trapoideae were important components of the freshwater ecosystem in Zhangpu during the middle Miocene.