Heritage Cases

Much like bone histology, the life history of an organism is recorded through the deposition of dental enamel and studying the nature of dental growth marks can provide valuable insights into the growth patterns and ecology of vertebrates4,5,6. Previous work on Diictodon dentition has focused on growth lines, analysis of stable isotopes, relation of tusks to sexual dimorphism, and the nature of the dentition as either tusks or teeth7,8,9,10. To date there has been no investigation of dental histology through ontogeny for Diictodon, as the only previous assessment of growth marks was concerned with variation across different stratigraphic zones9. In their respective assessment of three samples of Diictodon dentition, Whitney et al. (2021) proposed that the observation of three different dental character states could be indicative of ontogenetic stages but cannot conclusively rule out intraspecific or interspecific variation. Further histological exploration through an ontogenetic series could refine these deductions and advance our understanding of the nature of Diictodon dentition, as well as provide valuable information regarding their growth patterns through ontogeny. To facilitate the sampling of dental material through an ontogenetic series of Diictodon material we have identified small, middle-range, and large tusked specimens from the collection as candidates for longitudinal sectioning of the tusk profile. Acknowledging that tusks are a diagnostic characteristic, and important for morphological and taxonomic studies, we have selected specimens in which the associated crania are poorly preserved, broken or deformed. We have also selected specimens in which two tusks are present so that the specimen will still have an identifiable tusk associated with it. Please see below for a list of the selected specimens and figures depicting the tusk that will be sectioned. We propose to section all the identified tusks longitudinally, so that we can analyse the full tusk profile and establish daily secretion rates and growth increments, as well as carefully examining the morphology of the tusk. The remaining hemisphere of the tusk will be left intact.