A Middle Triassic stem-neopterygian fish from China sheds new light on the peltopleuriform phylogeny and internal fertilization


Internal fertilization and viviparity are easily observed and well studied in living neopterygian fishes (14 teleostean families), but they are difficult to identify in extinct taxa due to the limitation of the fossil record. The Peltopleuriformes from the Middle to Late Triassic of Europe and South China are a stem group of Neopterygii that may have first evolved internal fertilization and viviparity in this clade because they show a highly modified anal fin in presumed males resembling the intromittent organ in living viviparous teleosts. Until recently, Peltopleurus lissocephalus and P. rugosus from the Ladinian/Anisian boundary (~242 Ma) of Monte San Giorgio area in Switzerland and Italy represent the oldest record of Peltopleuriformes, and the phylogenetic interrelationships of this group remain controversial. Here, we report the discovery of a new peltopleuriform, Peltopleurus nitidus sp. nov., based on eleven well-preserved specimens from the early Middle Triassic (Pelsonian, Anisian, ~244 Ma) of Luoping, eastern Yunnan, China. The discovery documents the oldest convincing peltopleuriform, extending the geological range of this clade by proximately two million years. Results of the phylogenetic analysis recover P. nitidus at the base of Peltopleuridae, and provide robust support for the sister-group relationships of Peltopleuridae with Thoracopteridae within the Peltopleuriformes. The male anal fin of P. nitidus shows a primitive condition unknown in other peltopleuriforms. Comparative studies of the male anal fin in P. nitidus and other peltopleuriforms shed new light on the internal fertilization in this group.


体内受精和胎生容易在现生新鳍鱼类(真骨鱼类14个科)中观察,但由于化石保存的局限性,这些特征很难在绝灭的物种中识别。生活在欧洲和华南中、晚三叠世的肋鳞鱼目可能是新鳍鱼类中最早进化出体内受精和胎生的原始代表,因为保存较好的肋鳞鱼目鱼类的雄性个体具有与现生胎生真骨鱼雄性交配器相似的特化臀鳍。直到最近,产于瑞士和意大利圣乔治山地区安尼期和拉丁期界线附近的Peltopleurus lissocephalusP. rugosus代表了肋鳞鱼目鱼类最早的化石记录,而肋鳞鱼目内部的系统发育关系仍然不清楚。本文根据采集于云南省东部罗平县中三叠世安尼期地层(距今约2.44亿年前)的十一件保存完好的鱼化石,报道一种新的肋鳞鱼目物种,将它命名为光泽肋鳞鱼(Peltopleurus nitidus sp. nov.)。光泽肋鳞鱼是肋鳞鱼目最古老的代表,它的发现将该目的地质延限向前推进了约两百万年。分支分析的结果将光泽肋鳞鱼置于肋鳞鱼科的基部,并有力地支持了肋鳞鱼目内部肋鳞鱼科和胸鳍鱼科的姐妹群关系。光泽肋鳞鱼的臀鳍具有明显的性双型,它代表了其它肋鳞鱼目鱼类不具有的一种原始状态。将雄性光泽肋鳞鱼的臀鳍和其它雄性肋鳞鱼目鱼类的臀鳍进行比较,研究结果进一步揭示了肋鳞鱼目体内受精的生殖方式。

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We thank M.M. Chang, M. Zhu, F. Jin, and F.X. Wu for constructive suggestions and discussions, J.A. Finarelli for stylistic improvement, H. Furrer for access to comparative fossil material in the Paläontologisches Institut und Museum, Uiversität Zürich (Zürich), and S.X. Hu, T.L. Liu, J.X. Weng, and Q.T. Chen for helps in field trips in Yunnan Province. The research was supported by the National Natural Science Foundation of China (41672001 and 41272002), State Key Laboratory of Palaeobiology and Stratigraphy (Nanjing Institute of Geology and Palaeontology, CAS) (143114). Field collection of fossil specimens was also supported by a grant from the Chinese Academy of Sciences.

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Correspondence to Guang-Hui Xu.

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Xu, GH., Ma, XY. A Middle Triassic stem-neopterygian fish from China sheds new light on the peltopleuriform phylogeny and internal fertilization. Sci. Bull. 61, 1766–1774 (2016). https://doi.org/10.1007/s11434-016-1189-5

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  • Sexual dimorphism
  • Viviparity
  • Peltopleuridae
  • Thoracopteridae
  • Triassic