A peculiar tooth renewal in a Jurassic ray-finned fish (Lepisosteiformes: †Scheenstia sp.)

Tooth replacement in vertebrates is extremely diverse, and its study in extinct taxa gives insights into the evolution of the different dental renewal modes. Based on µ-CT scans of a left lower jaw of the extinct fish †Scheenstia (Actinopterygii – Lepisosteiformes), we describe in detail a peculiar tooth replacement mode that is, as far as we could trace back in the literature, unique among vertebrates. The formation of the replacement teeth comprises a 180° rotation of their acrodin cap that occurs intraosseously within bony crypts, and their setting up appears to be synchronous. We propose a model for the dental renewal process, and identify complementary anatomical features visible in the tomography such as the junction between the different tooth-bearing bones (prearticular-coronoid and dentary), as well as cavities corresponding to intraosseous crypts, nervous and/or vascular canals. The location of the cavities and their subsequent identification (e.g. Meckel’s cavity, mandibular ...