The oldest species of Peltoperleidus (Louwoichthyiformes, Neopterygii) from the Middle Triassic (Anisian) of China, with phylogenetic and biogeographic implications

Abstract

The previously alleged ‘perleidid’ genus Peltoperleidus is a stem-neopterygian fish taxon with two or three horizontal rows of notably deepened flank scales. Until recently, members of this genus were known only from the Ladinian (late Middle Triassic) or near the Anisian/Ladinian boundary (~242 Ma) in southern Switzerland and northern Italy. Here, I report the discovery of a new species of the genus, Peltoperleidus asiaticus sp. nov., based on three well-preserved specimens from the Anisian (early Middle Triassic, ~244 Ma) of Luoping, eastern Yunnan, China. The discovery extends the geological range of Peltoperleidus by approximately two million years and documents the first record of the genus in Asia. Similar to its relatives (represented by P. macrodontus) from Europe, P. asiaticus sp. nov. is likely a small-sized durophagous predator with dentition combining grasping and crushing morphologies. Results of a cladistic analysis unite four species of Peltoperleidus as a monophyletic group within the Louwoichthyiformes, and suggest that the presence of two horizontal rows of notably deepened scales was independently evolved in Peltoperleidus and another stem-neopterygian taxon Altisolepis. P. asiaticus sp. nov. is nested at the base of Peltoperleidus, and a new family Peltoperleididae is proposed for the genus, contrasting the previous placement of Peltoperleidus in the poorly defined, paraphyletic ‘Perleididae’. Comparative studies of the basal peltoperleidid from China with its younger relatives from Europe provide new insights into the evolutionary origin and paleogeographic distribution of this clade.

Figure 15 from: Arratia G (2022) The outstanding suction-feeder Marcopoloichthys furreri new species (Actinopterygii) from the Middle Triassic Tethys Realm of Europe and its implications for early evolution of neopterygian fishes. Fossil Record 25(2): 231-261. https://doi.org/10.3897/fr.25.85621

“…Later, Grande (2010), based on fossil and living lepisosteiforms, demonstrated the validity of the taxon Holostei, which has been confirmed in subsequent phylogenetic hypotheses based on morphological (e.g., Arratia 2013;López-Arbarello and Sferco 2018;Xu 2020aXu , 2020bGouiric-Cavalli and Arratia 2022) and molecular evidence (e.g., Near et al 2013;Betancur-R. et al 2013;Betancur-R. et al 2017). What seems resolved for extant neopterygians has been not so clear for fossil neopterygians with a large and varied record, and whose knowledge has improved during the last years due to new findings, especially in the Triassic of Eurasia (e.g., Xu et al 2013;Xu and Ma 2016;Xu 2020aXu , 2020bXu , 2021.…”

“…Although the phylogenetic relationships seem to be resolved for many neopterygian clades, and numerous stemand crown-group neopterygians are now recognized in recent phylogenetic hypotheses (e.g., López-Arbarello and Sferco 2018; Xu et al 2015;Xu and Ma 2016;Xu 2020aXu , 2020bXu , 2021, the phylogenetic analysis of thoracopteroids by Shen and Arratia (2022), who used the matrix of Xu (2020a), proved to be devastating (see their fig. 3, node 2; Fig.…”

“…For instance, Redfieldiiformes (Triassic to Early Jurassic age) have been controversial since the establishment of the family Catopteridae (= Redfieldiidae Berg, 1940) by Woodward in 1890. Discussions on redfieldiiform relationships or phylogenetic analyses including them can be found in Stensiö (1921), Brough (1931Brough ( , 1936, Schaeffer (1955Schaeffer ( , 1967Schaeffer ( , 1984, Hutchinson (1973Hutchinson ( , 1978, Gardiner and Schaeffer (1989), and more recently in Xu (2021). Redfieldiiformes and Platysiagiformes have been referred as subholosteans, a clade that has not had recognition in fish classification (e.g., Nelson et al 2016;Arratia 2021).…”

Supplementary material 3 from: Arratia G (2022) The outstanding suction-feeder Marcopoloichthys furreri new species (Actinopterygii) from the Middle Triassic Tethys Realm of Europe and its implications for early evolution of neopterygian fishes. Fossil Record 25(2): 231-261. https://doi.org/10.3897/fr.25.85621

“…Redfieldiiformes and Platysiagiformes have been referred as subholosteans, a clade that has not had recognition in fish classification (e.g., Nelson et al 2016;Arratia 2021). Redfieldiiformes (= family Redfieldiidae) and Platysiagiformes have recently been interpreted as primitive neopterygians by Xu (2020aXu ( , 2021Fig. 15 herein), but as crown actinopterygians, Palaeoniscimorpha, by Schultze et al (2022).…”