A unique Cretaceous–Paleogene lineage of piranha-jawed pycnodont fishes

Abstract

The extinct group of the Pycnodontiformes is one of the most characteristic components of the Mesozoic and early Cenozoic fish faunas. These ray-finned fishes, which underwent an explosive morphological diversification during the Late Cretaceous, are generally regarded as typical shell-crushers. Here we report unusual cutting-type dentitions from the Paleogene of Morocco which are assigned to a new genus of highly specialized pycnodont fish. This peculiar taxon represents the last member of a new, previously undetected 40-million-year lineage (Serrasalmimidae fam. nov., including two other new genera and Polygyrodus White, 1927) ranging back to the early Late Cretaceous and leading to exclusively carnivorous predatory forms, unique and unexpected among pycnodonts. Our discovery indicates that latest Cretaceous–earliest Paleogene pycnodonts occupied more diverse trophic niches than previously thought, taking advantage of the apparition of new prey types in the changing marine ecosystems of this time interval. The evolutionary sequence of trophic specialization characterizing this new group of pycnodontiforms is strikingly similar to that observed within serrasalmid characiforms, from seed- and fruit-eating pacus to flesh-eating piranhas.

Large-bodied sabre-toothed anchovies reveal unanticipated ecological diversity in early Palaeogene teleosts

“…These new Palaeogene radiations were joined by a handful of late-surviving examples of predatory marine neopterygian lineages that arose in the Mesozoic, all of which (e.g. †serrasalmimid pycnodontiforms [62], †vidalamine amiids [63] and possibly †pachyrhizodontids [64]) appear to have gone extinct by the end of the Eocene. The raptorial stem engraulids †Clupeopsis and †Monosmilus add to this diverse assortment of early Palaeogene nonacanthomorph predators in shallow-water settings (figure 4).…”

Reassessment of Cosmodus Sauvage, 1879, a poorly known genus of large pycnodont fish (Actinopterygii, Pycnodontiformes) from the Cenomanian (Upper Cretaceous) of Western Europe

“…Coelodus (e.g., Woodward, 1909;Priem, 1898;Schultz and Paunović, 1997), the poorly known pycnodontid genus Acrotemnus (= Macropycnodon) (e.g., Woodward, 1909;Shimada et al, 2010;Vullo and Courville, 2014), and the bizarre serrasalmimid genus Polygyrodus (Vullo et al, 2017). It can be assumed that this trend to gigantism in various distinct lineages (reported here for the first time within the Coccodontidae), with some forms exceeding one meter in total length, is one aspect of the explosive early Late Cretaceous diversification observed in pycnodont fishes (Marramà et al, 2016).…”

“…The order Pycnodontiformes is a widespread group of ray-finned fishes known from the Upper Triassic to the Eocene (e.g., Martín-Abad and Poyato-Ariza, 2013). Although pycnodontiform genera and species should be preferably defined and diagnosed on the basis of complete, articulated skeletons (Poyato-Ariza and Wenz, 2002), isolated vomerine and prearticular dentitions with unique features (or unique combinations of characters) are still regularly used to erect new taxa (e.g., Poyato-Ariza and Bermúdez-Rochas, 2009;Shimada et al, 2010;Stumpf et al, 2017;Vullo et al, 2017).…”

Pycnodont fishes (Actinopterygii, Pycnodontiformes) from the Upper Cretaceous (lower Turonian) Akrabou Formation of Asfla, Morocco

“…However, a few pycnodont genera show evidence of a piscivorous diet (e.g. Serrasalmimus , Eoserrasalmimus Vullo et al., 2017 ; Piranhamesodon Kölbl-Ebert et al., 2018 ) as indicated by their specialised blade-like dentition with sharp cutting edges suited for piercing and tearing flesh from other fishes. Acrorhinichthys poyatoi Taverne and Capasso (2015) from the Cretaceous of Lebanon, preserves small actinopterygian remains in the gastric tract of some specimens ( Capasso, 2019 ), presenting direct evidence for carnivory in some pycnodonts.…”