A new non-parasemionotiform order of the Halecomorphi (Neopterygii, Actinopterygii) from the Middle Triassic of Tethys

Abstract

The halecomorph fish Panxianichthys imparilis, from the Pelsonian (Anisian, Middle Triassic) of Panxian County, Guizhou Province, South China, was recently described in brief. Here we present a thorough revision of this taxon based on 22 specimens, which allows a much better understanding of its anatomy and, consequently, its phylogenetic relationships. Newly recognized anatomical features include a flat quadratojugal, a symplectic articulating with the lower jaw ventral to the quadrate articulation, five infraorbitals, up to three suborbitals, and a large tail body lobe. Panxianichthys represents the oldest known non-parasemionotiform halecomorph and has a crescent-shaped preopercle and a maxillary branch of infraorbital sensory canal, but it is excluded from the ‘Ionoscopiformes–Amiiformes’ clade mainly by the presence of a quadratojugal, a dermosphenotic hinged to the side of the skull roof with a smooth innerorbital flange bearing no sensory canal, and a symplectic articulation much more ventral than that of the quadrate. A comparison with other Triassic non-parasemionotiform halecomorphs, together with the phylogenetic analysis, supports the erection of a new halecomorph order, Panxianichthyiformes, which is the sister group to the post-Triassic ‘Ionoscopiformes–Amiiformes’ clade. In addition, Robustichthys, also from the Anisian and previously ascribed to Ionoscopiformes, is recognized here as a new stem-group Ginglymodi.

http://zoobank.org/urn:lsid:zoobank.org:pub:5594E962-985F-466D-AC52-2E9A5AC07787

Keywords:

• Panxianichthys imparilis
• Panxianichthyiformes
• Halecomorphi
• Middle Triassic
• Tethys

Acknowledgements

We especially thank Yuan Daojun (NIGP) and Xu Guanghui (IVPP) for access to the material under their care. The people of Yangjuan village assisted us during fossil excavations. Two anonymous reviewers spent a considerable amount of time and effort reviewing this manuscript and gave many constructive comments. This study was financially supported by Peking University, NSFC (grants 40920124002, 41372016, 41572008), State Key Laboratory of Palaeobiology and Stratigraphy (Nanjing Institute of Geology and Palaeontology, CAS) (Nos. 123107, 123102, 143108), Beijing Municipal Science and Technology Commission (No. Z141110000814107) and Beijing University Museum Union. The Italian participation was partly supported by MIUR-PRIN 2010-11 (E. Erba).

Supplemental material

Supplemental material for this article can be accessed at: http://dx.doi.org/10.1080/14772019.2016.1181679.

Additional information

Funding

National Natural Science Foundation of China [40920124002,41372016,41572008].