DOI: 10.5061/dryad.9cnp5hqxs
title: Rethinking thecodonty: The influence of two centuries of comparative dental anatomy on our understanding of tooth evolution

description: "Thecodont" refers to teeth implanted in sockets within the jaw,
 a condition traditionally associated with living mammals and crocodylians,
 which also coincidentally have teeth attached by ligaments to the socket
 walls (gomphosis). For over a century, the bony periodontium of many other
 amniotes has been described as a single tissue, "bone of attachment”,
 causing confusion over dental tissue homology. Conventional definitions of
 “thecodonty” exclude species with fused teeth (“ankylothecodonts”),
 implying a fundamental difference between mammals, crocodylians, and most
 other vertebrates. However, the stereotypically “thecodont” attachment
 tissues have been discovered in all major amniote clades, showing that
 gomphosis and ankylosis likely stem from heterochronic changes in the
 timing and extent of cementum and alveolar bone mineralization. This
 challenges (1) previous hypotheses regarding the evolution of the amniote
 periodontium, (2) the “bone of attachment” paradigm, and (3) the
 significance of “thecodonty”. We suggest a new nomenclatural approach that
 incorporates recent histological and evolutionary research and divides
 thecodonty into anatomical categories to clarify their origin and
 evolution. We propose the terms anisothecodont and isothecodont to denote,
 respectively, asymmetric and symmetric implantation of teeth in their
 sockets. Regardless of the geometry of the connection, we propose using
 ankylosis and gomphosis to denote the mode of tooth attachment.
description: # Rethinking thecodonty: The influence of two centuries of comparative
 dental anatomy on our understanding of tooth evolution Dataset DOI:
 [10.5061/dryad.9cnp5hqxs](10.5061/dryad.9cnp5hqxs) ## Description of the
 data and file structure This dataset contains the raw histological images
 (and one raw CT scan image) associated with the article *Rethinking
 Thecodonty: The influence of two centuries of comparative dental anatomy
 on our understanding of tooth evolution* published in *Biology Letters*.
 Each image is labeled according to the corresponding figure in the
 published article. For detailed information, please refer to the figure
 captions within the paper. ### Files and variables #### File:
 Fig_1B_-_Diadectid_-_TMM_43628-3_-_early_amniote.jpg
 **Description:** Tooth attachment tissues - Dental Histology #### File:
 Fig_1C_-_Human_-_Slide_43-99_Berkovitz_teaching_collection_-_King_s_College_London.jpg **Description:** Tooth attachment tissues - Dental Histology #### File: Fig_1D_-_Crocodylus_sp_-_Teaching_slide-King_s_College_London_-_Crocodylia.jpg **Description:** Tooth attachment tissues - Dental Histology #### File: Fig_2C1_-_Eucoelophysis_baldwini_-_GR_1072_-_Silesauridae.jpg **Description:** Tooth attachment tissues - Dental Histology #### File: Fig_2C2_-_Eucoelophysis_baldwini_-_GR_1072_-_Silesauridae.jpg **Description:** Tooth attachment tissues - Dental Histology #### File: Fig_2D_-_Coelophysis_bauri_-_CM_87671_-_Theropoda.jpg **Description:** Tooth attachment tissues - Dental Histology #### File: Fig_2E_-_Diadectid_-TMM_43628-3_-_early_amniote.jpg **Description:** Tooth attachment tissues - Dental Histology #### File: Fig_2F_-_Human_-_Slide_43-99_Berkovitz_teaching_collection_-_King_s_College_London.jpg **Description:** Tooth attachment tissues - Dental Histology #### File: Fig_2G_-_Captorhinus_-ROM_66861_-_early_amniote.jpg **Description:** Tooth attachment tissues - Dental Histology #### File: Suppl_Fig_A_-_Sacisaurus_agudoensis_-_MCN-PV_10095_-_Silesauridae.jpg **Description:** Tooth implantation, CT-SCAN. #### File: Suppl_Fig_B1_-_Sacisaurus_agudoensis_-_MCN-PV_10095_-_Silesauridae.jpg **Description:** Tooth attachment tissues - Dental Histology #### File: Suppl_Fig_B2_-_Sacisaurus_agudoensis_-_MCN-PV_10095_-_Silesauridae_-_XPOL.jpg **Description:** Tooth attachment tissues - Dental Histology #### Suppl_Fig_C_-_Caiman_sp__-_CMNAR_25747-4_-_Crocodylia.jpg **Description:** Tooth attachment tissues - Dental Histology #### File: Suppl_Fig_D_-_Caiman_sp__-_CMNAR_25747-4_-_Crocodylia.jpg **Description:** Tooth attachment tissues - Dental Histology ## Human subjects data All human subjects data included in this dataset have been fully de-identified in accordance with applicable ethical and legal guidelines. All personally identifiable information (PII) has been removed or anonymized. No information remains that could be used to identify individual participants.