The latest Cretaceous fish fauna from the Mocuio Formation of Bentiaba (Namibe Basin, Angola)

The Maastrichtian was punctuated by the Mid-Maastrichtian Event (MME), as manifested by carbon isotope excursions, the disappearance of inoceramids, and notable shifts in—amongst others—the mosasaur fauna. The exact nature of the drivers underlying the MME, however, are still a matter of debate.
The well-preserved fossil fauna of the Bentiaba site in southern Angola offers a rare window into the development of Late Cretaceous (Maastrichtian) marine ecosystems of the South Atlantic. Upwelling of cold, nutrient-rich water supported a rich marine ecosystem, which hosted a wide diversity of mosasaurs, plesiosaurs, and turtles.
To evaluate to what extent the diversity of the fish fauna at Bentiaba was impacted by the MME, we sampled and identified fish material from two fish-teeth enriched horizons at the Bentiaba site. We present a description of the osteichthyes and elasmobranch assemblage, and compare the assemblage to the previously described Cretaceous record from the Namibe Basin.
The fauna includes principally Squalicorax (notably S. pristodontus), Cretolamna sp., Carcharias sp., various batoids, dermal denticles, and abundant Ginglymostomatidae teeth. In total, at least nine shark families are represented in Bentiaba: Rhombodontidae, Anacoracidae, Odontaspididae, Otodontidae, Ginglymostomatidae, Chlamydoselachidae, Sclerorrhynchidae, and possible fragments of Hexanchidae and Triakidae. Osteichthyes remains include Pycnodontiformes, cf. Melvius sp., Enchodus sp., cf. Hadrodus, bony fish jaws, fish vertebrae and associated microfossils such as coprolites, gastropods, coral fragments and small mosasaur teeth. Overall, the sampled layers are significantly richer and more diverse than previously reported from the Bentiaba area. Ginglymostomatidae teeth are present in large numbers. Squalicorax pristodontus is particularly common in the tetrapod-rich Bench-19 layer, which is probably linked to their presumed scavenging ecology.
The composition of the elasmobranch assemblage shows strong resemblances with Maastrichtian faunas described from Morocco. While bony fish assemblages remain more consistent between layers, shark fauna shows notable changes, indicating plausible environmental shifts.