New holostean fishes (Actinopterygii: Neopterygii) from the Middle Triassic of the Monte San Giorgio (Canton Ticino, Switzerland)

Abstract

The new neopterygian genus Ticinolepis, including two new species T. longaeva and T. crassidens is described from Middle Triassic carbonate platform deposits of the Monte San Giorgio. The anatomy of this fish shows a mosaic of halecomorph and ginglymodian characters and, thus, the new taxon probably represents a basal holostean. During the latest Anisian to earliest Ladinian the two new species coexisted in the intraplatform basin represented by the uppermost Besano Formation, but only T. longaeva sp. nov. inhabited the more restricted basin represented by the Ladinian Meride Limestone (except for the Kalkschieferzone). The more widely distributed type species shows interesting patterns of intraspecific variation including ontogenetic changes and morphological variation over time. The second species presents anatomical features that strongly indicate a strictly durophagous diet. The different distribution of the species is interpreted as a result of habitat partitioning and different adaptability to palaeoenvironmental changes.

Neopterygian phylogeny: the merger assay

“…López-Arbarello et al . [ 37 ] described the genus † Ticinolepis from the Ladinian (Middle Triassic) of the Monte San Giorgio and discussed the resemblance of this fish with ginglymodians, but also with halecomorphs and teleosts. Owing to this mixture of morphological features, none of the available data matrices would have been adequate to explore the phylogenetic relationships of this genus because each of them was designed for cladistic analyses of the relationships within one or the other of the three main crown-neopterygian groups, and solving the systematic position of † Ticinolepis required the inclusion of all of them.…”

“…Within this context, the present contribution is dedicated to explore the phylogenetic relationships of the recently described Middle Triassic neopterygian genus † Ticinolepis López-Arbarello, Bürgin, Furrer and Stockar, 2016 [ 37 ]. This is one of the taxa showing a mixture of morphological features typically ascribed to Ginglymodi or Halecomorphi, together with other features observed only in teleosts [ 37 ].…”

“…Within this context, the present contribution is dedicated to explore the phylogenetic relationships of the recently described Middle Triassic neopterygian genus † Ticinolepis López-Arbarello, Bürgin, Furrer and Stockar, 2016 [ 37 ]. This is one of the taxa showing a mixture of morphological features typically ascribed to Ginglymodi or Halecomorphi, together with other features observed only in teleosts [ 37 ]. For this reason, to study the relationships of † Ticinolepis , we conducted a cladistic analysis based on the so far largest morphological dataset for fossil actinopterygians, including representatives of the three crown-neopterygian clades and merging the lists of characters from previously published systematic studies of neopterygians together with newly proposed characters.…”

Earliest known lepisosteoid extends the range of anatomically modern gars to the Late Jurassic

“…Today actinopterygians are represented by three major clades: Cladistia (bichirs and rope fish), with at least 16 species, Chondrostei (sturgeons and paddle fishes), with about 30 species, and Neopterygii, formed by the Teleostei, with about 30,000 species and the Holostei with eight species: one halecomorph (bowfin) and 7 ginglymodians (gars) 1 . Although neopterygians have a deep evolutionary history, dating back to the Palaeozoic 2 – 4 , their most important radiation occurred in the early Mesozoic 5 , 6 when they began to dominate aquatic ecosystems and when the holosteans were much diverse, presenting a taxonomic richness that exceeded that of teleosts 7 . Among the holosteans, ginglymodians represent a specialized clade, the relationships of which have recently been reassessed 8 – 10 .…”

Peculiar tooth renewal in a Jurassic ray‐finned fish (Lepisosteiformes, †Scheenstia sp.)

“…dermopalatines in Anarhichas (Bemis & Bemis ), dermopalatines and ectopterygoids in † Ticinolepis (López‐Arbarello et al . )) and paired (vomers) or unpaired bone (parasphenoid) from the base of the braincase (e.g. in osteoglossiforms; Taverne ).…”