Taxonomy and phylogeny of Eosemionotus Stolley, 1920 (Neopterygii: Ginglymodi) from the Middle Triassic of Europe

Abstract

Over 80 years the actinopterygian genus Eosemionotus was known from a single species, E. vogeli, from the German Muschelkalk (Anisian). A second species was published in 2004, E. ceresiensis, from the upper Besano Formation (lowermost Ladinian) of Monte San Giorgio, Switzerland. New excellently preserved specimens recovered from the Cassina and Sceltrich beds (Meride Limestone; Ladinian) in this latter area, triggered a new study. Consequently, three new species are established: E. diskosomus, E. sceltrichensis, and E. minutus, including differential diagnoses for the five species, which differ in body proportions, relative position of the fins, the morphology of several skull bones, squamation pattern, and some meristic characters (e.g., number of premaxillary teeth, and branchiostegal rays). The cladistic analysis retrieved Eosemionotus as the oldest Macrosemiidae within the order Semionotiformes (Ginglymodi). The monophyly of the genus and its sister-group relationships with the other macrosemiids are among the best supported nodes with high Bremer, jackknife and bootstrap values, and numerous synapomorphies. The pattern of phylogenetic relationships between the five species of Eosemionotus indicates that the Muschelkalk species E. vogeli originated through dispersal from the Tethys into the Germanic Basin, most probably across the Silesian-Moravian or the East Carpathian gates before the late Anisian. This very speciose genus, so far almost restricted to the Middle Triassic, has also been reported from localities in Eastern Switzerland, the Netherlands, Spain, Slovenia, and China. Pending the taxonomic and phylogenetic study of these other material of Eosemionotus, the origin of the genus in the Western or Eastern Tethys remains enigmatic.

Osteology and phylogeny ofRobustichthys luopingensis, the largest holostean fish in the Middle Triassic

“…This hypothesis, more clearly expressed by Patterson (1973), was later widely accepted by many authors (Rosen et al, 1981; Grande & Bemis, 1998; Liem et al, 2001). It was not until the last decade that morphological and molecular data reached a consensus on the sister group relationship between Halecomorphi and Ginglymodi and, consequently, the Holostei concept was resurrected (Hurley et al, 2007; Grande, 2010; Nakatani et al, 2011; Xu & Wu, 2012; Near et al, 2012; Broughton et al, 2013; Cavin, Deesri & Suteethorn, 2013; Giles et al, 2017; Sun et al, 2017; López-Arbarello & Sferco, 2018; López-Arbarello et al, 2016, 2019; Xu, Ma & Ren, 2018a; Xu, Ma & Zhao, 2018b; Xu et al, 2019).…”

Osteichthyan Fishes from the uppermost Norian (Triassic) of the Fuchsberg near Seinstedt, Lower Saxony (Germany)

“…Previously, the fishes were interpreted as semionotiform-like or possibly Semionotus, mainly based on the supposedly "spiny" median ridge scales in the predorsal region of the trunk, but as explained above, these are artifacts of preservation, not real dorsal median processes of the median predorsal scales (Figures 1B and 2A). However, when this new and more detailed morphological description of the fishes is compared with semionotiforms (e.g., in [32][33][34][35][36][37][38]), we do not find support for this taxonomic assignment. The combination of characteristics (especially cranial configuration and features) of the studied specimens does not place them close to any semionotiform taxon.…”

Phylogenetic Classification of Living and Fossil Ray-Finned Fishes (Actinopterygii)

“…Extinct panlepisosteiform lineages include †Araripelepidotes, †Cuneatus, †Fuyuanichthys, †Lepidotes, †Macrosemius, †Masillosteus, †Nhanulepisosteus, †Obaichthyidae, †Pliodetes, †Semionotus, †Thaiichthys, and †Ticinolepis (L. Grande and Bemis 1998;Wenz 1999;L. Grande 2010;López-Arbarello 2012;Cavin et al 2013;Xu, Zhao, et al 2014;Xu and Shen 2015;López-Arbarello et al 2016;Brito et al 2017). Details of the ages and locations of fossil holosteans are presented in Appendix 1.…”