J Syst Evol ›› 2024, Vol. 62 ›› Issue (1): 164-180.DOI: 10.1111/jse.12952

• Research Articles • Previous Articles     Next Articles

Exceptionally well-preserved seed cones of a new fossil species of hemlock, Tsuga weichangensis sp. nov. (Pinaceae), from the Lower Miocene of Hebei Province, North China

Ya Li1,2,3*, Carole T. Gee4,5, Zhen-Zhen Tan6, Yan-Bin Zhu1, Tie-Mei Yi2,7*, and Cheng-Sen Li2*   

  1. 1 State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing 210008, China;
    2 State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China;
    3 MNR Key Laboratory of Stratigraphy and Palaeontology, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;
    4 Division of Paleontology, Institute of Geosciences, University of Bonn, Bonn 53115, Germany;
    5 Huntington Botanical Gardens, San Marino, CA 91108, USA;
    6 College of Agro-Grassland Science, Nanjing Agricultural University, Nanjing 210095, China;
    7 Beijing Institute of Science and Technology Information, Beijing Academy of Science and Technology, Beijing 100044, China
    *Authors for correspondence. Ya Li. E-mail: yali@nigpas.ac.cn; Tie-Mei Yi. E-mail: yitm@bjstinfo.ac.cn; Cheng-Sen Li. E-mail: lics@ibcas.ac.cn
  • Received:2022-11-20 Online:2023-02-27 Published:2024-01-01

Abstract: Tsuga (hemlock) is a small genus of 10 extant species in the Pinaceae, with a disjunct distribution in East Asia and eastern and western North America. Reliable species-level identification of Tsuga fossils depends on the discovery of seed cones with intact bracts, but such cones are rare in the fossil record. Here we describe a new fossil species of hemlock as T. weichangensis sp. nov. based on exquisitely preserved seed cones with nearly complete bracts from the Lower Miocene of Weichang, Hebei Province, North China. This fossil species displays a mosaic of characters between Tsuga and Nothotsuga. The well-developed and slightly exserted bract scales of T. weichangensis are reminiscent of Nothotsuga, but other characters, such as nonleaved peduncles and tongue-shaped bract scales, in addition to monosaccate pollen found at the same fossil locality, suggest an affinity closer to Tsuga. Cladistic analysis based on 15 morphological characters and a molecular backbone constraint supports the assignment of these fossil cones to Tsuga rather than Nothotsuga, and places the fossil species of T. weichangensis in an unresolved polytomy within the genus Tsuga. The occurrence of Tsuga seed cone fossils indicate the paleoclimate in the Miocene of Weichang was warmer and more humid than today's climate, which is consistent with the paleoclimate reconstructed by paleopalynology.

Key words: Hannuoba Formation, micro-CT, Nothotsuga, phylogenetic analysis