Nautiluses are key to understanding the evolution of cephalopods, as they are their only outer-shelled modern representatives. Their chitinous beaks possess a calcified tip on the upper beak called a rhyncholite. These rhyncholites are found abundantly in the fossil record from Middle Triassic onwards and are described as being morphologically stable. Because of their feeding function, they likely carry information related to their diet and environment. Yet, the morphological variability of these fossils was poorly investigated. Here, we characterized the morphology of rhyncholites through time, together with morphologically similar fossils from the Jurassic and Cretaceous, the rhynchoteuthis. We digitized 254 specimens using X-ray microtomography (µCT) and performed a shape analysis using 3D geometric morphometrics. The morphological continuum observed between rhyncholites and rhynchoteuthis leads us to consider them as close relatives of nautilids, if not part of this group. The highest rhyncholites morphological disparity is observed after their apparition in Triassic. Triassic rhyncholites are morphologically closer to modern ones, probably sharing their opportunistic carnivorous diet and able to feed on hard items. This ability might have been advantageous during the Marine Mesozoic Revolution. During this arms race period, competition might have favoured the emergence of new forms like rhynchoteuthis, and the exploration of new niches as seen in Cretaceous morphologies indicating a possible diet shift toward softer prey items. Altogether, rhyncholites and rhynchoteuthis testify of a nautilids evolutionary history richer than what can be deduced from the shells only and carry important information that could improve reconstructions of past food-webs.