云南中三叠世(安尼期)预言鱼目(全骨鱼类:近鲱形类)一新属种

预言鱼目是近鲱形类的一个绝灭支系,被认为是弓鳍鱼目的姐妹群.预言鱼目化石过去主要发现于欧洲的中三叠世拉丁期和晚侏罗世地层以及新大陆的早白垩世地层.近年来,在云南和贵州的中三叠世安尼期地层中分别发现了一种预言鱼目鱼类化石(强壮鱼和盘县鱼),代表了该目在中国的首次发现.根据产于云南罗平中三叠世安尼期(～244 Ma)海相地层中的6块保存良好的鱼化石,命名了预言鱼目一个新的属种,三叠复兴鱼(Subortichthys triassicus gen.et sp.nov.).三叠复兴鱼是罗平生物群中发现的第二种预言鱼目鱼类,代表了预言鱼目最古老的化石记录之一,为研究该目的起源和早期分异提供了重要信息.复兴鱼无疑可以归入近鲱形类,因为它具有近鲱形类两个共近裔性状,续骨与下颌关节以及上颌骨后缘具有凹缺.分支分析结果表明,复兴鱼位于预言鱼目的基部,因为它具有该目的重要鉴定特征,上颌骨具有感觉管,但它不具有其他预言鱼目鱼类的进步特征.特别的是,复兴鱼具有一些独特的性状,如额外肩胛骨3或4对、第三眶下骨特别宽大并与前鳃盖骨前缘相接等.复兴鱼的发现表明预言鱼目鱼类在华南地区(三叠纪时期位于古特提斯洋的东部)的早期分异至少发生在中三叠世早期(安尼期).

A new ionoscopiform fish (Holostei: Halecomorphi) from the Middle Triassic (Anisian) of Yunnan,China

Ionoscopiformes,sister to Amiiformes,are an extinct group of halecomorph fishes previously known mainly from the late Middle Triassic (Ladinian) and Late Jurassic of Europe and the Early Cretaceous of the New World.They have not been known in China until recently two ionoscopiforms (Robustichthys and Panxianichthys) were found from the early Middle Triassic (Anisian) of Yunnan and Guizhou,respectively.Here,a new ionoscopiform,Subortichthys triassicus gen.et sp.nov.,is described on the basis of six well-preserved specimens from the early Middle Triassic (Pelsonian,Anisian,～244 Ma) marine deposits exposed in Luoping,eastern Yunnan,China.The discovery documents the second ionoscopiform from the Luoping fossil beds and one of the oldest ionoscopiforms in the world,providing important information for understanding the origin and early diversification of this group.Subortichthys is an unambiguous halecomorph as it possesses two synapomorphies of this clade:a symplectic articulating with the lower jaw and a notched posterior margin of the maxilla.Within the phylogenetic framework of the Halecomorphi,results of the phylogenetic analysis place Subortichthys at the base of the Ionoscopiformes because it bears a sensory canal in the maxilla (an ionoscopiform synapomorphy),but lacks derived features of other ionoscopiforms.Notably,Subortichthys is distinguished from other members of this order with a unique combination of features,such as presence of three or four pairs of extrascapulars and a much expanded third infraorbital posteriorly contacting the preopercle.The new material reveals that the earliest diversification of ionoscopiforms was well undertaken in South China (a part of east Paleotethys Ocean then) by the early Middle Triassic (Anisian).