DOI: 10.5061/dryad.82r11rm
title: Data from: A peculiar tooth renewal in a Jurassic ray-finned fish (Lepisosteiformes: †Scheenstia sp.)

description: 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 sensory canal) help settling the function of pores visible on
 the bone surface and understanding their relation to internal anatomical
 features. Finally, this tooth replacement mode raises the question whether
 it is specific to †Scheenstia or rather related to a particular dentition
 type and thus potentially occurs in other lineages.
description: Fig. 1. Photographs of
 the study specimen in mesial and labial views. Left lower jaw of
 †Scheenstia sp. (study specimen MJSN TCH005–353). A–B, photographs of the
 specimen in mesial (A) and labial (B) views. Scale bar = 1cm.
 Fig. 1.pdf
 
 Fig. 2. Numbering
 and volume of functional vs. replacement tooth pairs Numbering and volume of
 functional vs. replacement tooth pairs (the numbering of the teeth is
 arbitrary, on the basis of their general organisation). A–B, µ–CT based 3D
 model in occlusal view. Acrodin caps of a single pair are painted in the
 same colour and have the same number. A, entire study specimen (without
 pore sediment infill). B, model with transparent bones showing replacement
 and pre-functional tooth acrodin caps only. C, histogram showing the
 relative volume of functional (black) and replacement (white) acrodin cap
 of every tooth pair. Note that the volume of the pre-functional tooth
 (lila) is significantly smaller than that of neighbouring teeth (pairs n°
 24, 25, 31). F = functional tooth; R = replacement tooth; PF =
 pre-functional tooth; * = missing counterpart (broken-off, shed or
 lost). Fig.
 2.pdf Fig. 3. Slice of the
 µ-CT scan showing the pre-functional tooth and its pedicel.
 Slice of the
 µ-CT scan parallel to the symphysial surface showing the pre-functional
 tooth. Numbering of the tooth corresponds to the annotations in Appendix
 S2. PF = pre-functional tooth; F31 = functional tooth n° 31; en =
 enameloid (acrodin); de = dentine; ped = pedicel. Fig. 3.pdf
 
 Animation video
 of the 3D model of the left lower jaw of †Scheenstia sp. spinning around
 the dorso-ventral (left) and rostro-caudal (right) axes with different
 internal features highlighted. Animation: µ–CT based 3D
 model of the left lower jaw of †Scheenstia sp. spinning around
 dorso-ventral (left) and rostro-caudal (right) axes and showing internal
 features. Video.mp4