云南、贵州中三叠世一种大型的肋鳞鱼(辐鳍鱼亚纲:肋鳞鱼目)（英文）

A large peltopleurid fish(Actinopterygii: Peltopleuriformes) from the Middle Triassic of Yunnan and Guizhou, China

肋鳞鱼目是新鳍鱼类的一个干群,包括肋鳞鱼科和胸鳍鱼科,生活于欧洲和华南中、晚三叠世海洋环境。其中肋鳞鱼科鱼类通常个体较小,标准体长很少超过55 mm。根据最近发现于云南富源和贵州兴义中三叠世拉丁期(~240 Ma)海相地层的3块保存良好的鱼化石,命名了肋鳞鱼属一新种,霸王肋鳞鱼(Peltopleurus tyrannos sp.nov.)。该发现代表了中三叠世个体最大的肋鳞鱼属物种(体长达72 mm),为了解肋鳞鱼科的骨骼形态和摄食分异提供了新的信息。霸王肋鳞鱼不仅上、下颌口缘具有颇为粗壮的牙齿,在口内的颚翼骨上还生长有许多不同大小的钝牙;推测这些钝牙可能用于压碎一些带壳的无脊椎动物(如甲壳动物)和被硬鳞的小鱼,这与此前在兴义生物群中发现的东方肋鳞鱼形成鲜明的对比:东方肋鳞鱼体型很小(标准体长为26 mm)、口缘无牙、个体数量丰富,可能代表了一种集群游动、捕食细小浮游无脊椎动物的肋鳞鱼物种。新的发现表明华南中三叠世兴义生物群中的肋鳞鱼属已进化出两种不同的生态类型。

Peltopleuriformes are a stem group of neopterygian fishes from the Middle-Late Triassic marine ecosystems in Europe and South China, including the Peltopleuridae and Thoracopteridae. Among them, peltopleurids are commonly small-sized fishes with a standard length （SL） rarely exceeding 55 mm. Here, a new peltopleurid, Peltopleurus tyrannos sp. nov., is described based on three well-preserved specimens from the Middle Triassic （Ladinian） of Fuyuan, Yunnan and Xingyi, Guizhou, China. The discovery documents the largest species （SL = 72 mm） of this genus in the Middle Triassic and provides new insights into the morphologic and trophic diversifications of peltopleurids. In addition to large conical teeth on the oral margins of the jaws, the new peltopleurid bears many blunt teeth of various sizes on the oral margin of the palatopterygoid, which may be used for crushing some hard-shelled invertebrates （e.g., crustaceans） or small armored fishes. By contrast, the more commonly founded relative, P. orientalis, from the same ecosystem （Xingyi Biota） is toothless and has a much smaller body size （SL = 26 mm）, and probably represents a schooling fish that fed on small planktonic invertebrates. The new finding shows that Peltopleurus from the late Middle Triassic Xingyi Biota of South China had evolved into two different ecomorphotypes.