Large predatory actinopterygian fishes from the Late Jurassic of Poland studied with X-ray microtomography

`A rich collection of exceptionally preserved Upper Jurassic fossil fish remains obtained during the excavations in the Owadow-Brzezinki Quarry in Poland includes many jaw bones and teeth belonging to the members of actinopterygian fishes. X-ray microtomography (mu-CT), a non-destructive technique, is used to elucidate morphological and palaeohistological details of large, predatory actinopterygian dentary bones. Three-dimensional "virtual fossils" allows for taxonomical verification of two jaw bones. Palaeohistological studies confirmed the presence of many types of skeletal tissues (acrodin, osteodentine and orthodentine) in the actinopterygian dentary teeth. The very large and elongate mandibles of Caturus giganteus (Halecomorphi) and Orthocormus teyleri (Pachycormiformes) indicate that the members of those taxa are among the largest predatory fish of the Late Jurassic (Tithonian) lagoonal ecosystems in the Owadow-Brzezinki Quarry region. The comparative morphology shows that the studied mandibles are similar to the dentary bones of the extant Sphyraena barracuda and other long-jawed aquatic vertebrates. Late Jurassic actinopterygians share the feeding mode and hunting techniques with recent stalking predators. These similarities result from a very similar living environment of the Late Jurassic and modern actinopterygians.