Here we use synchrotron tomography to characterise dental vasculature in the oldest known tooth-bearing sharks, Leonodus carlsi Mader, 1986 and Celtiberina maderi Wang, 1993. Three dimensional reconstruction of the vascular system and microstructure of both taxa revealed a complex and dense network of canals, including horizontal, ascending and secondary bifurcated canals, as well as histological features consistent with an osteodont histotype. However, L. carlsi and C. maderi also exhibit significant morphological differences, showing Leonodus a typical diplodont tooth morphology with a linguo-labially elongated base, that contrast with Celtiberina’s teeth that show a single conical cusp curved lingually with a week developed flat base mesio-distally extended, perhaps reflecting distant relationship. These data are compatible with a pre-Devonian diversification of the two main tooth types traditionally recognised in Palaeozoic sharks (i.e., ‘cladodont’ vs ‘diplodont’). Finally, our data demonstrate that existing dental classification schemes based on styles of vascularisation are over-simplified, especially when Palaeozoic taxa are considered.
How Amira-Avizo Software is used
Both specimens were scanned using 2x and 4x objec tives, with exposure times of 300 ms at lated and analysed using the computed tomography software package AVIZO Lite v.9, allowing us to volumetrically characterise the three dimensional structure and arrangement of the dental vasculature, along with the hard tissue histology.