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Primate Teeth
Primate Teeth Evolution and Development BIO207 Ch. P.E. Zollikofer & M.S. Ponce de León University of Zurich 2013 Ann Margvelashvili Evolution & Structure Basic consideration • Teeth are set close to the sense organs. • Lifespan of dentition can be a factor of determining the lifespan of many mammals. Leonardo Da Vinci What are teeth needed for? • Ingestion • Chewing Conodonts primitive “teeth” Pre-Cambrian – Triassic 570-240 mln. years Goudemand et al 2011, PNAS How did conodont teeth work? Goudemand et al 2011, PNAS Tooth structure Enamell Crown Cr rown Dentine Cervix Ce ervix Root Cementum Mammalian dentition and dental surfaces Occlusal Life of tooth • Growth • Calcification • Eruption • Attrition What kind of teeth exist? • Single-cusped – homodonty • Multi-cusped – heterodonty I C P M Crown differentiation in non-mammals Varanus exanthematicus Sheepshead fish Tuatara Modified from Ungar 2010 Trend in dental evolution heterodont homodont Evolution Dental formulae Courtesy of C.P.E. Zollikofer & M.S.Ponce de León Tritubercular Theory Cope (1875) & Osborn (1888) Osborn 1888 Evolution of mammalian dentition • A) spaced singe cusps • B) occlusion of early mammals • C) triangulated molars of mammals After Lucas 2004 Evolution of mammalian dentition • Tribosphenic teeth Luo 2007 Tribosphenic tooth Pa Prd Pad Me Pr Med Trigon Hyd Talon Hyld Trigonid Talonid End Ungar 2010 Dual origin of tribosphenic teeth Placentals Mammaliaforms Monotremes Archaic Therians Marsupials Multituberculates Steropodon (fossil monotreme) Australia Northern tribosphenic mammals Ausktribosphenos (Australia) Southern tribosphenic mammals Ambondro (Madagascar) Luo et. al. 2001 Evolution of mammalian dentition • Hypocone has at least 20 times evolved among mammalian lineage Hunter & Jernvall 1995 Evolution of mammalian dentition Hunter 1998 Tooth formation and morpogenesis Action and interaction of ectoderm and underlying mesenchyme Ectodermal appendages http://link.springer.com/article/10.1007%2Fs10911-006-9029-x/fulltext.html Tooth formation stages Abigail Tucker & Paul Sharpe Nature Reviews Genetics 5, 499-508 (July 2004) Tooth formation Jernvall & Thesleff & 2012 Tooth formation Thesleff & Tummer 2009 Dental development: genetics and morphogenesis Gene network proliferation differentiation first cusp second cusp third cusp Enamel Knot Proliferating areas Mineralized areas After Jernvall & Salazar-Ciudad 2007 Reiterative signaling Jernvall & Salazar-Ciudad 2007 Reiterative signaling Late herbivores Early carnivores Evolution Jernvall & Salazar-Ciudad 2007 Dental development Gene network 2 types of diffusible signaling molecules Affect growth of the tooth germ inversely activator inhibitor Activates: Represses: Cellular differentiation (EK differentiation) Represses: proliferation of epithelial cells Cellular differentiation (EK differentiation) Activates: proliferation of the mesenchymal cells Salazar-Ciudad & Jernvall 2002 EK differentiation Dental development Gene network model activator inhibitor Epithelial proliferation Mesenchymal proliferation Salazar-Ciudad & Jernvall 2002 Model data and empirical data Salazar-Ciudad & Jernvall 2002 Modeled evolution of mammalian dentition • Tribosphenic teeth Salazar-Ciudad & Jernvall 2002 Morphodynamics: simultaneous pattern formation and morphogenesis Salazar-Ciudad, Jernvall & Newman 2003 Dental development Epithelial cells Mesenchymal cells Pattern formation EK formation Morphogenesis Cusp formation Courtesy of C.P.E. Zollikofer Morphogenetic Field Theory • Each tooth group has its own morphogenetic field. Incisivisation Caninization Molarization After Butler 1939 Gradient Field Theory • The tooth differentiation within one morphogenetic field, predicted by the gradient of concentration of substance Molarizing Potential primordia Primordia Field strength Field generator After Lumsden,1979 Odontogenic homeobox code model M I M After Sharpe (ed. Teaford, Smith, Ferguson) 2000 Shape, size and position of teeth Posterior Anterior • Mammalian molars develop in anterior to posterior direction. • Relative size of the adjacent teeth allows us to predict the presence and size of additional teeth . • It is unlikely that a large M2 is followed by a very small M3 • It is unknown how molar initiation or size is regulated Kavanagh et al 2007 Shape, size and position of teeth • The last teeth to form, will be the first to be lost. Permanent molars Permanent molars Deciduous molars Deciduous molars X Last teeth to form X Tooth loss Premolars Premolars Transition to tooth loss Modified from Lucas 2004 The inhibitory cascade Kavanagh et al 2007 Characteristics of mammalian dentition Mammalian dentition Herbivores Rodents Carnivores • Diversity Evans et. al 2007 Mammalian dentition • Diversity Carnivorans Rodents Individual Ungulates; Human; Multituberculate; Bat Arrowhead indicates the Hypocone Jernvall & Salazar-Ciudad 2007 Mammalian dentition • Heterodonty Mammalian dentition • Thecodonty tooth r o o t bone tooth bone Mammalian dentition • Succession Deciduous Permanent Mastication mammalian innovation • Palate • Occlusion • Strong masticatory muscles Lucas 2004 Mid-section of a human skull Primate tooth structure Modern hominoid tooth structure Buccal/ CHEEK Lower Upper Paracone Metacone Protoconid Hypoconid Talon Trigonid Mesial Trigon Distal Oblique crest Talonid Hypoconulid Protocone Hypocone Metaconid Lingual/ TONGUE Entoconid Evolution of mammalian dentition CHEEK Upper Metacone Hypoconid Protoconid Distal Mesial Paracone Lower Talonid Trigon Trigonid Talon Hypoconulid Entoconid Protocone Hypocone Paraconid TONGUE Metaconid Tooth interaction CHEEK TONGUE Tooth interaction CHEEK TONGUE Evolution of mammalian dentition Upper Lower CHEECK CHEECK PALATE TONGUE Evolution of mammalian dentition: Hominoids CHEECK CHEECK Upper Lower Crista obliqua PALATE Y pattern TONGUE Dryopithecus pattern • Contact between metaconid and hypoconid Me Hy http://www.wadsworth.com/anthropology_d/templates/stripped_features/primate_evolution/ Evolution of mammalian dentition: Cercopithecoids CHEECK CHEECK Upper Lower Bilophodonty PALATE TONGUE Hominoids & Cercopithecoids Take-home message • Teeth are important in developmental & evolutionary studies: – Teeth are found in almost all vertebrates and provide a general paradigm for the study of epithelial organ development and evolution – Teeth preserve many different types of information and help scientists interpret the evolutionary processes and life history of species
