Earth Science Frontiers ›› 2020, Vol. 27 ›› Issue (4): 110-123.DOI: 10.13745/j.esf.sf.2020.4.24

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Numerical taxonomy of Miocene Trapa L. fossil fruits from eastern Zhejiang, China

XIAO Liang1,4,5(), WANG Xing1, LI Xuemei2, LI Xiangchuan1,5, JIA Hui3, SUN Nan1, LIANG Jiaqi1, WANG Qin1, LI Jiangxiao1, YONG Yuanyuan1   

  1. 1. School of Earth Science and Resources, Chang'an University, Xi'an 710054, China
    2. Research Institute of Petroleum Exploration and Development, PetroChina Changqing Oilfield Company, Xi'an 710018, China
    3. School of Earth Sciences and Engineering, Xi'an Shiyou University, Xi'an 710065, China
    4. State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China
    5. Shaanxi Key Laboratory of Early Life and Environments, Northwest University, Xi'an 710069, China
  • Received:2019-05-22 Revised:2020-04-11 Online:2020-07-25 Published:2020-07-25

Abstract:

Abundant Trapa L. fruit fossils are found in the late Miocene Shengxian Formation in Tiantai, eastern Zhejiang. The fossils are well preserved with rich three-dimensional characteristics. However, the identification and taxonomy of Trapa L. have been controversial because of its large taxonomic variations yet subtle differences in the fossil's three-dimensional features. Since the characteristics of Trapa L. fossils are distinct and easy to measure and record, we used numerical statistics methods to classify Trapa L. fossils. The main methods include cluster and principal component analyses. The purpose of this research is to identify the Trapa fossil fruits and find the guiding characters for their identification and classification. First, we performed numerical analysis on living Trapa fruits and obtained good taxonomical result. Next, we analyzed Trapa fossil fruits. We believe the analyses can classify Trapa fossils and at the same time eliminate redundant characteristics used for identification. Finally, we obtained some discrimination characteristics, including fruit body shape, with or without head, valgus head, fruit top shape, upper or lower horn growth direction, length of lower horns, and number of degenerate tuberculate lower horns. Based on these characteristics, the fossil fruits can be effectively divided into two taxa.

Key words: Miocene Shengxian Formation, Trapa L., fossil fruits, cluster analysis, principal component analysis

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