Upper Triassic semionotids from western Gondwana

半拟鱼是最重要的鱼类之一，尽管人们对其了解较少。它们代表了这一类群最早也是最重要的一个分支，这一类群还包括硬骨鱼和大多数近代硬骨鱼。因此，了解硬骨鱼的基本系统发育关系和进化对理解硬骨鱼的进化和生物多样性至关重要。由于硬鱼动物起源于晚三叠世，所以像半形类这样的基底新鱼动物的早期历史特别有趣。半形虫的早期化石记录很大程度上偏向于北半球，对冈瓦纳这一群体的起源和第一次辐射知之甚少。阿根廷大陆上三叠统Cacheuta组（Norian）在Gondwana三叠纪发现了为数不多的三叠纪组记录之一，也是南美洲唯一的三叠纪关节半足类化石。因此，这条名为Semionotus vallejensis的鱼为我们提供了一个独特的机会，可以深入了解冈瓦纳西部半形动物的早期历史。该项目的目的是开展实地调查活动，以收集更多的山谷塞米诺图斯（Semionotus vallejensis）的资料，迄今为止，只有一个保存不完整的标本。利用这些新材料，将对该分类单元进行详细的研究，包括分类修订和系统发育关系分析。

Semionotids are among the most important, though less understood basal neopterygian fishes. They represent one of the first and most important radiations of this group, which also includes the teleosts and thus most of the Recent bony fishes. Therefore, knowledge of basal neopterygian phylogenetic relationships and evolution is essential to understand teleost evolution and biodiversity. Since teleosts originated in the late Triassic, the early history of basal neopterygians like the semionotiformes is of special interest. The early fossil record of the semionotiforms is largely biased to the Northern Hemisphere and very little is known about the origin and first radiation of this group in Gondwana. The continental Upper Triassic Cacheuta Formation (Norian) in Argentina has yielded one of the very few records of the group in the Triassic of Gondwana and the only Triassic articulated semionotid remains in South America. This fish, Semionotus vallejensis, thus represents a unique opportunity to have an insight into the early history of semionotiforms in Western Gondwana. The aim of this project is to carry out a fieldwork campaign to collect more material of Semionotus vallejensis, so far represented by a single incompletely preserved specimen. With the new material, the taxon will be studied in detailed, including a taxonomic revision and analysis of its phylogenetic relationships.