J Syst Evol ›› 2019, Vol. 57 ›› Issue (2): 153-168.DOI: 10.1111/jse.12450

• Research Articles • Previous Articles     Next Articles

An early Oligocene fossil acorn, associated leaves and pollen of the ring‐cupped oaks (Quercus subg. Cyclobalanopsis) from Maoming Basin, South China

Xiao-Yan Liu1,2, Sheng-Lan Xu1, Meng Han1, and Jian-Hua Jin1,2*   

  1. 1State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resources, and School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China
    2Key Laboratory of Economic Stratigraphy and Palaeogeography, Chinese Academy of Sciences (Nanjing Institute of Geology and Palaeontology), Nanjing 210008, China
  • Received:2018-01-28 Accepted:2018-06-21 Online:2018-07-03 Published:2019-03-01

Abstract: The ring‐cupped oaks (Quercus subg. Cyclobalanopsis) characterized by united and concentric ring‐cupped acorns, are mainly distributed in broad‐leaved evergreen forests in tropical and subtropical regions of East and Southeast Asia. Their geological history has been traced from the middle Eocene to Pleistocene. Most reports of the subgenus have been on the basis of leaves, whereas the acorns or cupules, more valuable evidence for the inter‐ and intrageneric classifications, have been relatively poorly documented. Here, we describe a new species, Quercus shangcunensis sp. nov., based on a ring‐cupped fossil acorn and pollen on the acorn, as well as Quercus sp. associated leaves, recovered from the early Oligocene Shangcun Formation of Maoming Basin, Guangdong Province, South China. The morphological and anatomical structures of these fossils confirm their attribution to the subg. Cyclobalanopsis. Quercus shangcunensis sp. nov. represents the world's first Oligocene fossil acorn and the earliest fossil acorn in China for the subgenus, indicating that the subg. Cyclobalanopsis arrived in the low latitude area of South China at least by the early Oligocene. Our fossil provides evidence that the subgenus was present in one of its modern distribution centers in the Oligocene, suggesting that the modern distribution patterns of the subg. Cyclobalanopsis most likely originated during or prior to the Oligocene.

Key words: Cyclobalanopsis, Early Oligocene, Fagaceae, fossil acorn, Shangcun Formation, South China