Bite marks on an ichthyodectiform fish from Australia : possible evidence of trophic interaction in an Early Cretaceous marine ecosystem

A well-preserved fish skull from late Albian deposits of the Allaru Mudstone near Richmond in Queensland displays a conspicuous V-shaped pattern of indentations, punctures and depression fractures consistent with a vertebrate bite trace. This is the first direct evidence of trophic interaction between vertebrates within an Early Cretaceous marine ecosystem from Australia. The specimen is taxonomically referable to the largebodied (ca 1m snout–tail length) ichthyodectiform Cooyoo australis, but the size and spacing of the tooth marks is incompatible with attack by a conspecific individual. The lack of osseous growths concordant with healing also suggests that the bite occurred shortly before or after the animal’s death. Comparison with the dentitions of other coeval vertebrates indicates compatible tooth arrangements in longirostrine amniote predators such as polycotylid plesiosaurians, ornithocheiroid pterosaurs and especially the ichthyosaurian Platypterygius. The implications of this as a potential predator–prey association are that Early Cretaceous actinopterygians occupied middle-level trophic niches and were in turn consumed by higher-level amniote carnivores, similar to many extant marine vertebrate communities of today