Preophidion arcuatus was a cusk-eel relative known from sagittal otoliths. Ophidiids are mainly demersal fishes, many living over soft seabeds and feeding on small fishes and invertebrates. A similar bottom-associated ecology is a reasonable inference for the Eocene animal, although the London Clay fossils preserve only the ear stones.

The otolith has a characteristic curved sulcus in which the posterior cauda bends downward. That feature records a distinctive inner-ear morphology and helps demonstrate the abundance and variety of ophidiiform fishes in warm early Eocene shelf environments.