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Ontogenetic development of the holocephalan dentition

Among the cartilaginous fishes (Chondrichthyes), the Holocephali are unique in that teeth are absent both in ontogeny and adult regenerative growth. Instead, the holocephalan dentition of statodont non-shedding dental plates is composed of dentine, trabecular in arrangement, forming spaces into which a novel hypermineralized dentine (whitlockin) is deposited. These tissue features form a variety of specific morphologies as the defining characters of dental plates in the three families of extant holocephalans. We demonstrate how this morphology changes through ontogenetic development with continuity between morphologies, through successive growth stages of the statodont dentition represented by the dental plate. For example, rod-shaped whitlockin appears early, later transformed into the tritoral pad, including a regular arrangement of vascular canals and whitlockin forming with increasing mineralization (95-98%). While the tritoral pads develop lingually, stacks of individual ovoids of whitlockin replace the rods in the more labial parts of the plate, again shaped by the forming trabecular dentine. The ability to make dentine to new, distinctive patterns is retained in the evolution of the Holocephali, despite the lack of teeth forming in development of the dentition. We propose that developmentally, odontogenic stem cells, retained through evolution, control the trabecular dentine formation within the dental plate, and transition to form whitlockin, throughout life-time growth. Our model of cellular activity proposes a tight membrane of odontoblasts, having transformed to whitloblasts, that can control active influx of minerals to the rapidly mineralizing dentine, forming whitlockin. After the reduced whitoblast cells transition back to odontoblasts, they continue to monitor the levels of minerals (calcium, phosphate, magnesium), and at a slower rate of growth in the peritubate ‘softer’ dentine. This model explains the unique features of transitions within the holocephalan dental plate morphology.

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Cite this as

Zerina Johanson (2020). Ontogenetic development of the holocephalan dentition [Data set]. Natural History Museum. https://doi.org/10.5519/nqobtcw1
Retrieved: 07:39 28 Apr 2025 (UTC) BibTeX

Additional Info

Field Value
Primary contributors
Johanson, Zerina ( 0000-0002-8444-6776)
Other contributors
Last updated 11 December 2020
Last resource update 11 December 2020 (Callorhinchus milii upper Figure 2A-G)
Created 7 December 2020
License Creative Commons Attribution