Pycnodus bowerbanki was a pycnodont, one of the deep-bodied ray-finned fishes specialised for crushing hard food. The species is known from a lower-jaw splenial tooth plate carrying several rows of broad crushing teeth. This dentition is direct evidence for durophagy, most plausibly feeding on molluscs, crustaceans or other hard-shelled benthic organisms.

Pycnodonts had a long evolutionary history before the Eocene, and P. bowerbanki represents one of the later members of that successful feeding guild. The London Clay fossil is fragmentary but biologically informative: the proportions and arrangement of its tooth rows reveal how force was distributed across the crushing surface.