Phylogenetic Interrelationships of Ginglymodian Fishes (Actinopterygii: Neopterygii)

The Ginglymodi is one of the most common, though poorly understood groups of neopterygians, which includes gars, macrosemiiforms, and semionotiforms. In particular, the phylogenetic relationships between the widely distributed semionotiforms, and between them and other ginglymodians have been enigmatic. Here, the phylogenetic relationships between eight of the 11 semionotiform genera, five genera of living and fossil gars and three macrosemiid genera, are analysed through cladistic analysis, based on 90 morphological characters and 37 taxa, including 7 out-group taxa. The results of the analysis show that the Ginglymodi includes two main lineages: Lepisosteiformes and dagger Semionotiformes. The genera dagger Pliodetes, dagger Araripelepidotes, dagger Lepidotes, dagger Scheenstia, and dagger Isanichthys are lepisosteiforms, and not semionotiforms, as previously thought, and these taxa extend the stratigraphic range of the lineage leading to gars back up to the Early Jurassic. A monophyletic dagger Lepidotes is restricted to the Early Jurassic species, whereas the strongly tritoral species previously referred to dagger Lepidotes are referred to dagger Scheenstia. Other species previously referred to dagger Lepidotes represent other genera or new taxa. The macrosemiids are well nested within semionotiforms, together with dagger Semionotidae, here restricted to dagger Semionotus, and a new family including dagger Callipurbeckia n. gen. minor (previously referred to dagger Lepidotes), dagger Macrosemimimus, dagger Tlayuamichin, dagger Paralepidotus, and dagger Semiolepis. Due to the numerous taxonomic changes needed according to the phylogenetic analysis, this article also includes formal taxonomic definitions and diagnoses for all generic and higher taxa, which are new or modified. The study of Mesozoic ginglymodians led to confirm Patterson's observation that these fishes show morphological affinities with both halecomorphs and teleosts. Therefore, the compilation of large data sets including the Mesozoic ginglymodians and the re-evaluation of several hypotheses of homology are essential to test the hypotheses of the Halecostomi vs. the Holostei, which is one of the major topics in the evolution of Mesozoic vertebrates and the origin of modern fish faunas.