First fossil record of Canarium (Burseraceae) from the middle Miocene of Fujian, southeastern China and its paleoecological implications

Abstract

The pili nut genus Canarium is an important element in tropical rainforests and seasonal rainforests of the northern and southern hemispheres. The genus contains some economically important species widely cultivated as food crops worldwide. Fossil evidence suggests that Canarium had occurred in Africa, Asia, Europe and North America during the Paleogene, with the earliest fossil record from the early Eocene of eastern North America and southern England. Here we describe the three-dimensionally preserved fruits of Canarium from the middle Miocene Zhangpu flora in Fujian, southeastern China as a new species, Canarium haominiae n. sp. The internal structures and anatomical details of the fossil fruits were investigated using X-ray micro-computed tomography and scanning electron microscope. Endocarps of C. haominiae formed by three connate pyrenes are ovoid to spindle-shaped in lateral view and rounded triangular in cross section, with acute to obtuse base and slightly acuminate to acute apex. Each pyrene is unilocular and dehiscent by an operculate germination valve. The germination valve is ovate and opens from the top of the pyrene to approximate two thirds of its length towards the base. The occurrence of C. haominiae confirms that the middle Miocene Zhangpu flora represents a megathermal seasonal rainforest, and also indicates that Canarium might have been an important component in the tropical seasonal rainforest since the middle Miocene.