J Syst Evol

• Research Articles •    

Fossil fruits of Illigera (Hernandiaceae) from the Eocene of central Tibetan Plateau

Teng-Xiang Wang1,2, Cédric Del Rio1,3, Steven R. Manchester4, Jia Liu1,3, Fei-Xiang Wu5, Wei-Yu-Dong Deng1,2, Tao Su1,3*, and Zhe-Kun Zhou1,3,6*   

  1. 1CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla 666303, Yunnan, China
    2University of Chinese Academy of Sciences, Beijing 100049, China
    3Center of Plant Ecology, Core Botanical Gardens, Chinese Academy of Sciences, Mengla 666303, China
    4Florida Museum of Natural History, University of Florida, Gainesville, FL 32611-7800, USA
    5Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China
    6Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650204, China
  • Received:2020-05-08 Accepted:2020-08-30

Abstract: Illigera (Hernandiaceae) is a liana genus distributed mainly in the tropical Asia and Africa. Previous fossil records suggested that Illigera was restricted in western North America during the Eocene. Recent paleobotanical investigation has unveiled a Paleogene flora that is totally different from today’s vegetation in central Tibet. This provides novel insights into the paleoenvironmental change during the evolution of Tibetan Plateau (TP). Here, we investigated 10 fruit impressions of Illigera from the early middle Eocene Niubao Formation in the Bangor Basin, central TP. The fossil winged fruits are characterized by their eroded fruit wings, well-preserved fusiform locular areas with a median ridge bisecting the fruit, and short veins fanning radially outward. These features allow us to assign these fossils to Illigera eocenica, a species originally discovered in the Eocene of western North America. This is the second fossil occurrence of Illigera worldwide, and the first in Asia. Our finding suggests a warm and humid climate in the central TP during the early middle Eocene, and a close floristic link between Asia and North America during the Paleogene. We also propose a Northern Hemisphere origin and a Paleogene dispersal event from Northern Hemisphere to Africa for Illigera.

Key words: Illigera, Eocene, Niubao Formation, Tibetan Plateau, Hernandiaceae, winged fruit, biogeography