The dentition of extant holocephalans (chimaeroids; Chondrichthyes) differs from other chondrichthyans (sharks, rays), in that teeth are absent. Instead, holocephalans bear dental plates composed entirely of dentine, notably a hypermineralized form made of whitlockin, restricted to pre-formed spaces within trabecular dentine. Whitlockin is deposited without a fibrous matrix and develops into a variety of morphologies, becoming increasingly mineralized, and more wear-resistant than the supporting dentine. This creates surface morphologies important in differentiating extant and fossil species. These morphologies include separate rods and ovoids, and compact tritoral pads with a distinctive pattern of vascular canals. This ability to make dentine is retained in the evolution of the Holocephali, but with a new mineralogy, and into these specific patterns. Successive growth stages of the dentine-retaining plates demonstrate developmental continuity between these morphologies, the earliest being the rod-shaped whitlockin. As these lingual rods grow, vascular grooves form, as dentine surrounds associated blood vessels; these are eventually aligned spatially to form the morphology of the tritoral pad. Later, along the lateral margin of the dental plate, rods are replaced by a series of ovoids. We propose that the different shapes of these whitlockin entities are developmentally linked, transformed from pre-formed cellular, vascularised spaces of trabecular dentine through to their adult morphologies. This indicates patterning of whitlockin within the dental plate and of the surrounding dentine, with the ability of the latter to change substantially to accommodate these developmental changes.