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

A 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.

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

“…C. Gill and Mooi 2002;Springer and Johnson 2004). Phylogenetic analysis of morphological characters resolves the Late Cretaceous †Ctenothrissiformes and Acanthomorpha as sister lineages (Davesne et al 2016;Cantalice et al 2021), a result consistent with a pre-cladistic study (Patterson 1964). Studies by M. Gaudant (1978bGaudant ( , 1979 hypothesized that †Ctenothrissiformes are stem lineage ctenosquamates.…”

“…Acanthomorpha currently includes more than 19,895 living species (Fricke et al 2023), classified in the subclades Lampriformes, Paracanthopterygii, and Acanthopterygii. Fossil lineages include the pan-lampriforms †Aipichthys, †Aipichthyoides, †Nardovelifer, and †Zoqueichthys (Patterson 1964; Alvarado-Ortega and Than-Marchese 2012; Murray and Wilson 2014;Davesne et al 2016;Delbarre et al 2016;Cantalice et al 2021); the panparacanthopterygian †Pycnosteroides (Patterson 1964(Patterson , 1993Davesne et al 2016;Cantalice et al 2021); and the pan-acanthopterygian †Choichix (Cantalice et al 2021). Details of the ages and locations of the fossil taxa are given in Appendix 1.…”

“…Morphological apomorphies for Acanthomorpha include (1) anterior facets on the first vertebral centrum that articulate with the exoccipital condyles (Rosen 1985;G. D. Johnson and Patterson 1993;Wiley and Johnson 2010), (2) maxillo-rostroid ligament originates from inner portion of maxillary median process and inserts onto rostral cartilage (Stiassny 1986;Olney et al 1993;Wiley and Johnson 2010), (3) spina occipitalis extends ventrally, forming dorsal margin of the foramen magnum (Stiassny 1986;Olney et al 1993), (4) anterior extension of lateral ethmoid located close to, or sutured with, lateral process projecting from ventral stalk of vomer (Stiassny 1986;Olney et al 1993;Davesne et al 2016;Cantalice et al 2021), (5) upper limb of posttemporal bound to epioccipital with a reduced posttemporal-epioccipital ligament (Stiassny 1986;Olney et al 1993), ( 6 Synonyms. Acanthomorphata (Wiley and Johnson 2010:127, 146-147;Betancur-R et al 2017:20) is an ambiguous synonym of Acanthomorpha.…”

“…Bayesian relaxed molecular clock analyses of Acanthomorpha result in an average posterior crown age estimate of 144.8 million years ago, with the credible interval ranging between 136.9 and 152.3 million years ago (Ghezelayagh et al 2022) of lampriforms in Taeniosomi (Regan 1907b). A series of morphological phylogenetic analyses that included multiple species of Lampriformes were aimed at investigating the relationships of several pan-lampriform fossil taxa (Davesne et al 2014(Davesne et al , 2016Delbarre et al 2016;Cantalice et al 2021).…”

Belemnite phylogeny and decline during the mid-Cretaceous

“…The earliest teleost fishes are known from the Middle-Late Triassic boundary (Arratia, 2014). Teleost fishes diversified during the mid-Cretaceous owing in part to the origin of the hyperdiverse spiny-rayed teleosts or Acanthomorpha in the Cenomanian (e.g., Patterson, 1993;Davesne et al, 2014;Cantalice et al, 2021). Acanthomorphs are characterized by sharp spines in their fins as well as highly protrusible mouths.…”