Multicuspid tooth morphology in a gigantic Palaeocene pycnodont fish: evolutionary and palaeoecological significance

Romain Vullo (1) , Nathalie Bardet (2) , Emmanuel Gheerbrant (2) , Nour-Eddine Eddine Jalil (2)

1 GR - Géosciences Rennes
2 CR2P - Centre de Recherche en Paléontologie - Paris

A pycnodont premaxilla bearing a large incisiform tooth with an unusual crown morphology is described from the Palaeocene (Thanetian) phosphate deposits of Morocco. This peculiar tooth shows a broad, fan-shaped multicuspid crown with nine cusps, well adapted for benthic macroalgal scraping. This morph, assigned to a new species of Pycnodus (P. multicuspidatus sp. nov.), emphasizes the phenotypic plasticity of the group and documents an additional trophic specialization among Palaeogene pycnodontiform fishes. In the post-K/Pg boundary marine ecosystem of the Ouled Abdoun Basin, P. multicuspidatus sp. nov. may have opportunistically replaced Maastrichtian fish taxa with a similar front dentition and feeding behaviour, such as the putative specialized pycnodontiforms Stephanodus and Hadrodus.

Mots clés: Actinopterygii; pycnodontiformes; dentition; trophic specialization; Palaeogene; Morocco; Actinopterygii

Domaines: Systématique, phylogénie et taxonomie; Paléontologie; Zoologie des vertébrés; Evolution [q-bio.PE]

Romain Vullo, Nathalie Bardet, Emmanuel Gheerbrant, Nour-Eddine Eddine Jalil. Multicuspid tooth morphology in a gigantic Palaeocene pycnodont fish: evolutionary and palaeoecological significance. Geological Magazine, 2019, 156, pp.1618 - 1622. ⟨10.1017/s0016756819000736⟩. ⟨hal-03916865⟩