†Pycnodontiformes (Actinopterygii) as prey: Their ecological niche and role in the food web

Pycnodontiformes are a well-known family of Actinopterygii that lived from the Triassic to the Eocene. While there are many convergences with modern-day reef-dwelling teleosts, there are also many unanswered questions about their ecological niche and role in the food web, e.g., because Mesozoic reefs were fundamentally different from present-day coral reefs. This article documents pycnodontiform fossils in their role as prey. Palaeontological evidence for predation consists of the remains of a predator’s meal outside the body in the form of coprolites and regurgitalites; the remains of bones and teeth of pycnodontiforms found as stomach and gut content (cololites and gastrolites) of predators; traces of predation in the form of bite injuries to the fins and to the proximal parts of bodies of the pycnodontiforms, and pycnodontiform body fossils partially eaten by scavengers. Since fish, specialised for a reef environment rarely have the chance to enter the fossil record, taphonomic factors are decisive to inform our view of Pycnodontiformes in their role as prey. Evidence is more complete for more generalist forms such as Gyrodus from the Solnhofen Archipelago, which seems to have ventured regularly into the deeper Plattenkalk basins, where they are the most common Pycno donti-formes. Evidence is sparser for the highly manoeuvrable reef specialists among Pycnodontiformes, which are allochthonous to the Plattenkalk basins.