Revisão de Ionoscopiformes (Actinopterygii: Neopterygii) e certos táxons fósseis basais de Halecomorphi: morfologia, taxonomia e relações filogenéticas

Abstract

Ionoscopiformes is an actinopterigian fossil fish order with wide temporal and geographic distribution, known from the Middle Triassic to the Upper Cretaceous, in Europe, Africa, Asia, and North and South America. Ionoscopiformes is composed of two families, Ophiopsidae and Ionoscopidae, which present various species, some of them with a poorly known anatomy. Although Ionoscopiformres is considered a monophyletic group, the species of Ophiopsidae and Ionoscopidae differ on various characters, including the type of scales and the pattern of ornamentation on the dermic bones. Ionoscopiformes is placed into the clade Halecomorphi, which is represented by three orders (Amiiformes, Parasemionontiformes, and Ionoscopiformes) and several incertae sedis taxa (e.g., Heterolepidotus, Osteorachis, and Neorhombolepis). Halecomorphi is considered to be closer to Ginglymodi than to Teleostei, forming with the former the clade Holostei. Some of these incertae sedis taxa were previously related to Ionoscopiformes, especially to the family Ophiopsidae. Several questions concearning the composition of Ophiopsidae and related taxa have been recently reported in literature, such as, the position of the genera Placidichthys, Heterolepidotus, and Furo. The genus Heterolepidotus was previously suggested as Ophiopsidae and as a taxon with a basal position to this family, but also as belonging to the family Caturidae. Placidichthys was recently proposed as a Macrosemiiformes and Furo muensteri as an Ophiopsidae. Given the need for greater knowledge on the species of Ionoscopiformes and related incertae sedis taxa, the present work presents a anatomical review of these taxa and phylogenetic hiposteses on the position of them within Neopterygii. Considering the anatomical and phylogenetic review, herein are proposed several taxonomical sugestions. The genera Ionoscopus, Ophiopsis, and Heterolepidotus were redefined and its nominal species were diagnosed. Were suggested as valid: four species of the genus Ionoscopus (I. pietraroiea, I. desori, I. cyprinoides, and I. elongatus), six of Ophiopsis (O. procera, O. breviceps, O. dorsalis, O. lepersonnei, O. montsechensis, and O. lepturus), and only two of Heterolepidotus (H. rhombifer and H. serrulatus). Were also suggested some cases of synonymy, reversals, nomen nudum, and nomen dubium. The phylogenetic hypotheses presented here did not recoreved Ionoscopiformes as a monophyletic clade. However, the families Ionoscopidae and Ophiopsidae were confirmed as Halecomorphi and it was also suggested a closer relationship between Ionocopidae and Amiiformes, while Ophiopsidae appears to be more closely related to Furo and Heterolepidotus. The internal relationships of both Ionoscopidae and Ophiopsidae were not resolved, however Placidichthys was recovered within the family Ophiopsidae. The non monophyletism of Ionoscopiformes and the absence of resolution concearning the taxa closely related to Ophiopsidae, reinforce the need of reviewing other Halecomorphy taxa, such as Caturidae, and also the necessity of searching for new characters, such as those from histology, in order to improve the data matrix to achieve better supported phylogenetc analyses of these clades.