Flower inclusions of Canarium (Burseraceae) from Miocene Zhangpu amber (China)

The Miocene amber from Zhangpu (Fujian Province, southeastern China) has recently displayed a significant palaeobiodiversity with numerous inclusions of insects, fungi, angiosperms as well as a few gastropods and feathers. In this paper, we investigate for the first time flower inclusions from the Zhangpu amber, using synchrotron-radiation-based X-ray micro-computed tomography (SRlCT). Our results show that both flowers are morphologically bisexual but functionally male, whorled, and trimerous. The perianth is differentiated into a synsepalous calyx and a polypetalous corolla. The obdiplostemonous androecium comprises six connate stamens forming a staminal tube around a fleshy nectary disk and an aborted syncarpous gynoecium with a superior ovary. Both flowers also share a subtending bract, a pair of bracteoles and secretory ducts. We recognize two new fossil species of Canarium, C. wangboi n. sp. and C. leenhoutsii n. sp., distinguished from one another by the shape, length and extent of fusion of the calyx, the shape and length of the corolla, the fusion and length of the staminal tube and the shape of the nectary disk. The genus, which belongs to the Burseraceae family, is nowadays distributed pantropically in the warm regions of Africa, Asia and Northeast Oceania. This study represents the first fossil record of Canarium flowers and gives new insights into the diversity of the Zhangpu amber forest. Moreover, it supports the palaeoenvironmental interpretation of the sedimentary plant fossils deriving from the amber bearing layer, indicating a warm and humid climate in Zhangpu during the Mid-Miocene Climatic Optimum.(c) 2023 Elsevier B.V. and Nanjing Institute of Geology and Palaeontology, CAS. All rights reserved.