Ancient armored fish, known as placoderms, developed two different ways to crush their prey around 385 million years ago, according to a study led by researchers from Flinders University. These early jawed fish, which appeared over 400 million years ago, lived in the rich marine environments of what is now Australia. Using advanced computer simulations and three-dimensional analysis of their jaws, the researchers reconstructed how eight placoderm species fed in the ancient oceans, revealing unique feeding strategies. Smaller placoderm species used broad, flat plates to crush their prey, while larger ones evolved sharp, weapon-like teeth to pierce and break apart heavily armored or shelled animals. Surprisingly, both the smallest and largest species had exceptionally strong jaws, even though they used completely different tools for feeding. The smallest had simple, flat crushing plates, while the largest had complex, elevated dental structures. The study suggests that the size of the prey influenced how placoderms evolved their feeding methods. Smaller prey could be swallowed whole and crushed using flat plates, but larger prey needed to be broken into smaller pieces first. This required more advanced dental features capable of piercing armor before crushing it. The largest species had teeth arranged along a raised bony crest, resembling the heads of medieval weapons like war hammers and poleaxes. The research highlights that early jawed vertebrates, such as placoderms, did not evolve a single method for eating hard objects. Instead, a variety of jaw structures emerged, allowing these fish to exploit different types of prey in the ancient reef ecosystem. Flinders University emeritus professor John Long, a co-author of the study, has spent 40 years studying fossils at a site in Western Australia. The Gogo Formation, a key location for this research, has been the focus of long-term studies involving local Indigenous communities, the Gooniyandi and Gogo people.