Table of Contents
  • Volume 57 Issue 2

    Special issue: Ecological and Biogeographic Implications of Asian Cenozoic Fossil Floras

    Cover illustration: Hypothesized fruit morphological evolution and biogeographic history of Cedrelospermum. Image from Lin-Bo Jia et al. See Jia et al., pp. 94–104 in this issue.
      
    Editoral
    Xiaoyan Liu and Steven R. Manchester
    2019, 57 (2): 91-93.
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    Research Articles
    Lin-Bo Jia, Tao Su, Yong-Jiang Huang, Fei-Xiang Wu, Tao Deng, and Zhe-Kun Zhou
    2019, 57 (2): 94-104.
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    Cedrelospermum Saporta is an extinct genus in the Ulmaceae with abundant fossil records in North America and Europe. However, so far, fossil records of this genus from Asia are sparse, which limits the interpretations of the morphological evolution and biogeographical history of the genus. Here we report well‐preserved fruits (Cedrelospermum tibeticum sp. nov.) and a leaf (Cedrelospermum sp.) of Cedrelospermum from the upper Oligocene Lunpola and Nyima basins in the Qinghai–Tibetan Plateau (QTP). This is the first fossil record of Cedrelospermum in the QTP, showing that this genus grew in this region during the late Oligocene. Cedrelospermum tibeticum fruits are double‐winged, morphologically similar to the Eocene and Oligocene double‐winged Cedrelospermum species from North America. This supports the hypothesis that Cedrelospermum migrated to Asia from North America by way of the Bering Land Bridge. Given that Cedrelospermum was a typical element of Northern Hemispheric flora in the Paleogene and Neogene, the presence of this genus indicates that the central region of the QTP was phytogeographically linked with other parts of the Northern Hemisphere during the late Oligocene. The morphological observations of C. tibeticum fruits and other double‐winged Cedrelospermum fruits suggest an evolutionary trend from obtuse to acute apex for the primary wing. Cedrelospermum tibeticum likely had warm and wet climatic requirements. This type of an environment possibly existed in the central QTP in the late Oligocene, thereby supporting the survival of C. tibeticum.
    He Xu, Tao Su, and Zhe-Kun Zhou
    2019, 57 (2): 105-113.
    Plant fossils from the Qinghai–Tibetan Plateau (QTP), China are critical to understand not only the diversification history of plants there, but also the paleoenvironmental conditions. Alnus are deciduous trees, mainly distributed in temperate and subtropical regions of Eurasia and North America, and they are well known in the fossil records throughout the Cenozoic in the Northern Hemisphere. We collected numerous well‐preserved Alnus leaf and infructescence fossils from the Lawula Formation (~34.6 Ma with 40Ar/39Ar dating) at the present elevation of 3910 m a.s.l. in the southeastern QTP. Based on detailed morphological comparisons with existing and fossil species, these fossils show closest affinity to Alnus ferdinandi‐coburgii C. K. Schneid., and we refer to these fossils as A. cf. ferdinandi‐coburgii. These specimens comprise the oldest megafossil record of Alnus in the QTP, and provide solid evidence for the distribution of Alnus there as early as the late Eocene. Extant A. ferdinandi‐coburgii is distributed in areas with mean annual temperature values between 9.7 °C and 16.9 °C, and mean annual precipitation values ranging from 896.2 mm to 1161.2 mm; therefore, fossils of A. cf. ferdinandi‐coburgii suggest a much warmer and wetter climate during the late Eocene than today in the southeastern QTP. This finding is consistent with other evidence for continued uplift of the southeastern QTP after the late Eocene that might be due to the eastward extension of the QTP.
    Atsushi Yabe, Eunkyoung Jeong, Kyungsik Kim, and Kazuhiko Uemura
    2019, 57 (2): 114-128.
    Temporal and spatial changes of ten conifer genera that are endemic to East Asia were analyzed based on fossil data from humid temperate forests in the Japanese Islands and Korean Peninsula to elucidate the phytogeographic history, and to understand differences between those genera eliminated from the Japanese Islands and those that remained extant. All these genera, except for Thujopsis, have existed in the area since the Paleogene and remained in the Japanese islands after initial separation from the continent at the early–middle Miocene. Fossil representatives of locally extinct six genera have tendencies to adapt to wider ranges of climatic conditions than their modern relatives. Metasequoia, Glyptostrobus, and Taiwania began to change their distributions since the late Miocene possibly through habitat partitioning. Keteleeria, Pseudolarix, and Cunninghamia appeared to have expanded their habitat toward warmer conditions during the mid‐Miocene Climatic Optimum and then became restricted to warmer forest vegetation by the end of Pliocene. Overall changes in their distribution can be explained by climatic effects. On the contrary, three genera endemic to Japan (Sciadopitys, Cryptomeria, and Thujopsis) followed clearly different trends from the others. Cryptomeria and Thujopsis were especially adapted to cooler‐temperate climate and they retained their habitat areas in the northern part of Japan. During the late Miocene–Pliocene, the islands connected with the Eurasian continent again, which probably acted as a corridor for warm‐adapted genera to disperse southwest. Current data suggest that ecological requirements of each genus might be essential to determine whether they could survive on the Japanese Islands.
    Svetlana Popova, Torsten Utescher, Dmitry Gromyko, Volker Mosbrugger, Louis François
    2019, 57 (2): 129-141.
    Abstract   |