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 Li, Carole T. Gee, Zhen-Zhen Tan, Yan-Bin Zhu, Tie-Mei Yi, Cheng-Sen Li

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Journal of Systematics and Evolution ›› 2024, Vol. 62 ›› Issue (1) : 164-180. DOI: 10.1111/jse.12952
Research Article

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

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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.

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Hannuoba Formation / micro-CT / Nothotsuga / phylogenetic analysis

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Ya Li, Carole T. Gee, Zhen-Zhen Tan, Yan-Bin Zhu, Tie-Mei Yi, Cheng-Sen Li. 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. Journal of Systematics and Evolution, 2024, 62(1): 164‒180 https://doi.org/10.1111/jse.12952

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2023 2023 Institute of Botany, Chinese Academy of Sciences.
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