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Ionoscopiformes, sister to Amiiformes, are an extinct group of marine halecomorphs. In the past decades, ionoscopiforms were known from the Late Jurassic of Europe and the Early Cretaceous of the New World. Here, we introduce the fourth ionoscopiform known from China, Subortichthys triassicus Ma and Xu, 2017 from the early Middle Triassic (Pelsonian, Anisian) of Luoping, Yunnan Province. This paper summarizes information on the osteology of Robustichthys, Subortichthys and Panxianichthys based on well-preserved specimens. The new material reveals that the earliest diversification of ionoscopiforms was well underway in South China by the early Middle Triassic (Anisian).

The extinct ray-finned fish taxon Robustichthys luopingensis from Luoping, eastern Yunnan, China represents the largest holostean known in the Middle Triassic. Despite its potential significance for investigating the holostean phylogeny and reconstructing the Triassic marine ecosystems, Robustichthys has so far not been described in detail and its phylogenetic position within the Holostei was controversy. This study provides a redescription and revision of Robustichthys based upon a comparative study of eight type specimens and nine new specimens. Newly recognized information includes a toothed parasphenoid, a pair of premaxillae not pierced by the olfactory nerve, a splint-like quadratojugal, a hatchet-shaped hyomandibula, an hourglass-shaped symplectic, anterior and posterior ceratohyals, a complete series of branchiostegal rays, and sclerotic bones. A revised reconstruction of Robustichthys is presented. Results of a cladistic analysis confirmed Robustichthys as an ionoscopiform within the Halecomorphi; the previous placements of Robustichthys as a basal ginglymodian and Ionoscopidae as a basal amiiform clade are not supported. The sister group relationship between Sinamiinae (Sinamia and Ikechaoamia) and Amiinae (Amia and Cyclurus) within the Amiidae is newly recognized. This revised topology provides new insights into the evolution and historical paleoecology of halecomorph fishes.

The extinct ray-finned fish taxon Robustichthys luopingensis from Luoping, eastern Yunnan, China represents the largest holostean known in the Middle Triassic. Despite its potential significance for investigating the holostean phylogeny and reconstructing the Triassic marine ecosystems, Robustichthys has so far not been described in detail and its phylogenetic position within the Holostei was controversy. This study provides a redescription and revision of Robustichthys based upon a comparative study of eight type specimens and nine new specimens. Newly recognized information includes a toothed parasphenoid, a pair of premaxillae not pierced by the olfactory nerve, a splint-like quadratojugal, a hatchet-shaped hyomandibula, an hourglass-shaped symplectic, anterior and posterior ceratohyals, a complete series of branchiostegal rays, and sclerotic bones. A revised reconstruction of Robustichthys is presented. Results of a cladistic analysis confirmed Robustichthys as an ionoscopiform within the Halecomorphi; the previous placements of Robustichthys as a basal ginglymodian and Ionoscopidae as a basal amiiform clade are not supported. The sister group relationship between Sinamiinae (Sinamia and Ikechaoamia) and Amiinae (Amia and Cyclurus) within the Amiidae is newly recognized. This revised topology provides new insights into the evolution and historical paleoecology of halecomorph fishes. [ABSTRACT FROM AUTHOR]

The holostean fish Asialepidotus shingyiensis, from the Middle Triassic (Ladinian) of Guizhou and Yunnan, China, was previously regarded as either a semionotiform ginglymodian or an amiiform halecomorph. This study provides a revision of this taxonomically controversial taxon based on a comparative study including the holotype and 50 new specimens. Newly recognized anatomical information includes the dermal component on the sphenotic, complete series of circumorbital bones, palatal bones, quadratojugal, hyomandibula, sensory canal in the maxilla, notched posterior margin of the maxilla, median gular, and many elements on the medial surface of the lower jaw. Results of a cladistic analysis incorporating these new data place Asialepidotus as an ionoscopiform halecomorph that is more derived than Subortichthys and Panxianichthys, and consists of the sister taxon of Robustichthys and all other ionoscopiforms.

New and well-preserved fossil fish material from the Upper Cretaceous (Cenomanian) of Haqel, Lebanon, is assigned to Spathiurus dorsalis Davis, 1887. Spathiurus dorsalis and Amphilaphurus major are found to be synonymous. A complete re-description of this taxon is provided and delivers new recognized anatomical information, mainly cranial features. Spathiurus dorsalis displays diagnostic characters of ionoscopids and consequently is designated as a new member of this family. A phylogenetic analysis was performed to place this taxon within the Halecomorphi. The studied taxon was recovered as the sister genera of Ionoscopus petrarojae , both derived compared to 'Ionoscopus' cyprinoides , suggesting that the latter should be placed in a distinct genus. The validated placement of Spathiurus within the Ionoscopidae extends the stratigraphic range of this family from the Albian to the Cenomanian and becomes the first record of an ionoscopiform from the Upper Cretaceous and from the Middle East. • New fossil fish material from the Cenomanian of Haqel, Lebanon assigned to Spathiurus dorsalis. • Spathiurus dorsalis found to be an ionoscopid based on new anatomical data and phylogenetic analysis. • Stratigraphic range of Ionoscopidae extended from Albian to Cenomanian. • First record of Ionoscopiform from the Upper Cretaceous and from the Middle East. [ABSTRACT FROM AUTHOR]

The Halecomorphi are a major subdivision of the ray-finned fishes. Although living halecomorphs are represented solely by the freshwater bowfin, Amia calva, this clade has a rich fossil history, and the resolution of interrelationships among extinct members is central to the problem of understanding the origin of the Teleostei, the largest clade of extant vertebrates. The Ionoscopiformes are extinct marine halecomorphs that were inferred to have originated in the Late Jurassic of Europe, and subsequently dispersed to the Early Cretaceous of the New World. Here, we report the discovery of a new ionoscopiform, Robustichthys luopingensis gen. et sp. nov., based on eight well-preserved specimens from the Anisian (242-247 Ma), Middle Triassic marine deposits of Luoping, eastern Yunnan Province, China. The new species documents the oldest known ionoscopiform, extending the stratigraphic range of this group by approximately 90 Ma, and the geographical distribution of this group into the Middle Triassic of South China, a part of eastern Palaeotethys Ocean. These new data provide a minimum estimate for the split of Ionoscopiformes from its sister clade Amiiformes and shed new light on the origin of ionoscopiform fishes., (© 2014 The Author(s) Published by the Royal Society. All rights reserved.)