A new Cenomanian acanthomorph fish from the El Chango quarry (Chiapas, south‐eastern Mexico) and its implications for the early diversification and evolutionary trends of acanthopterygians

Abstract

AbstractA new Cenomanian spiny‐rayed fish from El Chango quarry, Chiapas, south‐eastern Mexico is described and included, together with †Zoqueichthys carolinae and †Pepemkay maya, in the most recent phylogenetic analysis of acanthomorph fishes encompassing both extant and extinct taxa. The topologies recovered from the parsimony phylogenetic analysis using both multistate (or composite), and contingent (or reductive), coding are compared, along with a Bayesian estimation. All the analyses corroborate the placement of †Z. carolinae in the Lampripterygii, while both †Choichix alvaradoi gen. et sp. nov. and †P. maya are considered to be incertae sedis members of the Acanthopterygii. Although no apomorphic character states for †C. alvaradoi were found, the unique combination of features supports the description of a new genus and species for the Upper Cretaceous of Mexico. The species herein described is the earliest diverging acanthopterygian lineage. The most outstanding character found is the absence of a true pelvic fin spine, which, together with its placement in the phylogenetic analysis, suggests the independent acquisition of the pelvic fin spine in both paracanthopterygians and acanthopterygians from a segmented first soft ray. This extinct taxon therefore plays an important part in our understanding of both fish diversity through time and the early steps in the diversification of acanthopterygians.