Primate TeethEvolution and Development

BIO207Ch. P.E. Zollikofer & M.S. Ponce de León

University of Zurich2013

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

Conodontsprimitive “teeth”

Pre-Cambrian – Triassic570-240 mln. years Goudemand et al 2011, PNAS

How did conodont teeth work?

Goudemand et al 2011, PNAS

Tooth structureEnamel

Cementum

DentineCrown

Cervix

Root

Enamell

Cementum

DentinerownCr

ervixCe

Root

Mammalian dentition and dental surfacesO

cclusal

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

Modified from Ungar 2010

Sheepshead fish

Varanus exanthematicus

Tuatara

Trend in dental evolution

Evolution

homodont heterodont

Dental formulae

Courtesy of C.P.E. Zollikofer & M.S.Ponce de León

Tritubercular TheoryCope (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

Ungar 2010

Pa Me

Pr

TrigonTalon

Pad Med

Prd

Trigonid Talonid

End

Hyd Hyld

Dual origin of tribosphenic teeth

Luo et. al. 2001

PlacentalsMarsupialsArchaic TheriansMultituberculates

MonotremesMammaliaforms

Steropodon(fossil monotreme)

Australia

Ausktribosphenos(Australia)

Ambondro(Madagascar)

Southern tribosphenic mammals

Northern tribosphenic mammals

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 SharpeNature Reviews Genetics 5, 499-508 (July 2004)

Tooth formation

Jernvall & Thesleff & 2012

Thesleff & Tummer 2009

Tooth formation

Dental development: genetics and morphogenesis

Enamel KnotProliferating areasMineralized areas

After Jernvall & Salazar-Ciudad 2007

first cusp

second cusp

third cusp

Gene network

differentiationproliferation

Reiterative signaling

Jernvall & Salazar-Ciudad 2007

Reiterative signaling

Early carnivores Late herbivores

Evolution

Jernvall & Salazar-Ciudad 2007

Dental developmentGene network

2 types of diffusible signaling molecules

activator inhibitor

Affect growth of the tooth germ inversely

Represses:proliferation of epithelial cells

Cellular differentiation (EK differentiation)

Activates:

Activates:proliferation of the mesenchymal cells

Cellular differentiation(EK differentiation)

Represses:

Salazar-Ciudad & Jernvall 2002

Dental developmentGene network

model

Salazar-Ciudad & Jernvall 2002

inhibitor

Mesenchymalproliferation

Epithelialproliferation

EK d

iffer

entia

tion

activator

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 cellsMesenchymalcells

EK formation

Cusp formation

Pattern formation

Morphogenesis

Courtesy of C.P.E. Zollikofer

Morphogenetic Field Theory

• Each tooth group has its own morphogenetic field.

After Butler 1939

Incisivisation

CaninizationMolarization

Gradient Field Theory• The tooth differentiation within one

morphogenetic field, predicted by the gradient of concentration of substance

After Lumsden,1979

Molarizing

Potential primordiaPrimordia

Field generator

Field strength

Odontogenic homeobox code model

After Sharpe (ed. Teaford, Smith, Ferguson) 2000

IM M

Shape, size and position of teeth

• 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

Ante

rior Posterior

Shape, size and position of teeth

• The last teeth to form, will be the first to be lost.

Modified from Lucas 2004

Deciduous molarsPermanent molars

Premolars

Last teeth to form

Premolars

Deciduous molarsPermanent molars

X

X

Tooth loss

Transition to tooth loss

The inhibitory cascade

Kavanagh et al 2007

Characteristics of mammalian dentition

Mammalian dentition

• Diversity

Carn

ivor

es

RodentsH

erbi

vore

s

Evans et. al 2007

Mammalian dentition

• Diversity

Jernvall & Salazar-Ciudad 2007

Carnivorans

Rodents

Individual Ungulates; Human; Multituberculate; Bat Arrowhead indicates the Hypocone

Mammalian dentition

• Heterodonty

• Thecodonty

Mammalian dentition

bone

bone

toothtooth

root

• Succession

PermanentDeciduous

Mammalian dentition

Mastication mammalian innovation

• Palate

• Occlusion

• Strong masticatory muscles

Mid-section of a human skullLucas 2004

Primate tooth structure

Modern hominoid tooth structure

Upper LowerBuccal/ CHEEK

Lingual/ TONGUE

Mes

ial

Distal

Trigon

Talon

Paracone Metacone

Protocone HypoconeTr

igon

id

MetaconidEntoconid

Talonid

Hypoconulid

HypoconidProtoconid

Oblique crest

Evolution of mammalian dentition

Trigon

Talon

Paracone Metacone

Protocone Hypocone

Hypoconid

Trigonid

Talonid

Paraconid Metaconid

Protoconid

Hypoconulid

Entoconid

CHEEK

TONGUE

Mes

ial

Distal

Upper Lower

Tooth interaction

CHEEK

TONGUE

Tooth interaction

CHEEK

TONGUE

Evolution of mammalian dentitionUpper Lower

TONGUEPALATE

CHEECKCHEECK

Evolution of mammalian dentition: Hominoids

Upp

erLow

er

Crista obliquaY pattern

TONGUEPALATE

CHEECKCHEECK

Dryopithecus pattern

• Contact between metaconid and hypoconid

http://www.wadsworth.com/anthropology_d/templates/stripped_features/primate_evolution/

MeHy

Evolution of mammalian dentition: Cercopithecoids

Bilophodonty

Upp

erLow

er

TONGUEPALATE

CHEECKCHEECK

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