The geological significance of a new species of Coniopteris from the Middle Jurassic of northwestern China

ABSTRACT

The genus Coniopteris was a dominate member of most Middle Jurassic floras globally. Strata in northern Xinjiang Province are well-known for containing abundant fern and ginkgo fossils, especially Coniopteris, usually identified as the Coniopteris-Phoenicopsis flora. We report a new species named Coniopteris sandaolingensis X. C. Yuan et B. N. Sun sp. nov in this paper which was collected from the Xishanyao Formation within the Turpan-Hami Basin. This species is recognized and described based on the architecture of its fronds and reproductive organ features. The fertile pinnae in this species are also slightly contracted, which suggests that currently known specimens belong to either Coniopteris or Eboracia to some extent, while its characteristic cup-like indusia show that it belongs to Coniopteris. This species is unique, however, because the first pinnule on the basiscopic side is forked into two equal lanceolate lobes. The results of our comparisons based on fossil Dicksoniaceae lead us to conclude that both present fossil and C. bella are likely transitional species that might provide insights into exactly how Coniopteris has evolved into other genera. The fossils discussed here led us to infer that the climate during the early Middle Jurassic of Sandaoling is warm and humid.

KEYWORDS:

• Coniopteris
• middle Jurassic
• in situ spores
• evolution
• Xinjiang

Acknowledgments

We thank Prof. Sheng-Hui Deng (Research Institute of Petroleum Exploration and Development, Petro China) and Van Konijnenburg-van Cittert JHA (Laboratory of Palaeobotany and Palynology, Utrecht University, the Netherlands) for their kindness and for providing constructive discussions about the genus Coniopteris. We also thank Dr. De-Fei Yan, San-Ping Xie, Jing-Yu Wu, and Bao-Xia Du (School of Earth Science, Lanzhou University, China) for providing us with the relevant literatures and for numerous helpful suggestions about our manuscript. This work was supported by the National Natural Science Foundation of China (41172022), by Fundamental Research Funds for the Central Universities (lzujbky-2016-202), and by the Foundation of the State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (163117).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [No. 41172022];