Fossil fruits and pollen grains of Trapa from the Upper Pliocene of Sanying Formation (Yunnan, China)

Aye Thida Aung , Cédric Del Rio (1) , Teng‐xiang Wang , Jia Liu , Tao Su

1 Xishuangbanna Tropical Botanical Garden

Trapa (water chestnut or water caltrop) is a genus of annual free-floating plant mostly native from Africa and Eurasia and included in the family Lythraceae. The genus only contains 8 species today but has a huge number of fossil species in the Neogene, mainly based on fruits as well as pollen grains. In China, several fossil species have been previously recorded during the Miocene and Pliocene, but few with detailed description. Here we describe a new species of fruits from the Pliocene of the Sanying Formation, Yangjie coalmine, western Yunnan based on the following characters: the medium size of the fruit, the relatively long upper horns, the well-developed and triangular lower horns, the well-developed tubercles between lower and upper horns, and a long and large neck bearing hairs without corona. In addition, pollen grains were uncovered from the same sediment and having typical Trapaceous characters such as medium size, tricolpate, obtuse triangular in shape in polar view, and in possession of 3 meridional crests covering the apertures. The new species of Trapa shows a close morphological similarity with the Miocene species Trapa chengsenii from the Miocene of Yunnan and with the modern species Trapa natans. The pollen grains belonging to Sporotrapoidites cf. weiheensis also closely resemble those of Trapa natans. The occurrence of Trapa suggests that depositional environment corresponds to open and shallow water with a water temperature more than 20 °C in the growing period.

Domaines: Paléontologie; Botanique

Aye Thida Aung, Cédric Del Rio, Teng‐xiang Wang, Jia Liu, Tao Su. Fossil fruits and pollen grains of Trapa from the Upper Pliocene of Sanying Formation (Yunnan, China). NECLIME Meeting, Neogene Climate Evolution in Eurasia Meeting, 2021, Online, China. ⟨hal-03736475⟩