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REPTILIAN vs MAMMALIAN

DENTITION

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MOLARS OF MESOZOIC

PROTOTHERIANS

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MOLARS OF MULTITUBERCULATES

& MONOTREMES

MultituberculataPtilodus

Monotremata

Obdurodon Ornithorhynchus

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EVOLUTION OF THERIAN MOLARS

Tribosphenic

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THERIAN (TRIBOSPHENIC) MOLARS

(occlusal view)

(lateral view)

upper

lower

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TRIBOSPHENIC MOLAR OCCLUSION

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Quadrate or Bunodont

(primate)

Dilambdodo

(insectivore

Variations on Tribosphenic molar

ectoloph

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MOLARS crowns & roots

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Lophodont molar (murid rodents)

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Selenodont molar (artiodactyls)

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Loxodont molar

(elephant)

(capybara)

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DENTAL FORMULA

Canis lupus

I C P M3 1 4 2

Upper dentition

(one side only)

1 1 4 3

I c p mLower dentition

(one side only)

3 1 4 2________

3 1 4 3(x 2) = 42

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DENTAL FORMULAS

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Extreme dentitions

Nine-banded armadillo (Dasypus)

simpli fication and reduction

Common dolphin (Delphinus)

simpli fication and multipl ication

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EARLY MAMMAL GROUPS

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ORDER SYMMETRODONTA

basal therians

Kuehneotheriumlate Triassic early Jurassic

Europe

Vincelestes

early Cretaceus, Argentina

HadrocodiumearlyJurassic, China

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SYMMETRODONTSLoss of post-dentary bones in lower jaw

Hadrocodon (Docodont, Prototherian)

Hadrocodium (Symmetrodont, basal Therian)

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SYMMETRODONT

Molar structure

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OLDEST MARSUPIAL?

Sinodelphys -- early Cretaceous (China)

4 1 4 4

4 1 4 3= 50

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OLDEST EUTHERIAN ?

Eomaia -- early Cretaceous (China)

5 1 5 34 1 5 3

_______ = 54

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EARLY EUTHERIAN

Ukhaatherium late Cretaceus, Mongol

5 1 4 3_________ = 504 1 4 3

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Skulls of early therians

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Skulls of early therians

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EARLY METATHERIAN

ORDER: DIDELPHIMORPHIA

Family: DidephildaeAlphadon (Late Createous, N. America)

5 1 3 4

4 1 3 4 = 50

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MARSUPIAL BIOGEOGRAPHY

To N. America

early diversification

(late Cretaceous)

Ameridelphian

diversification

(late Cretaceous)

Australodelphian

Isolation and

diversification(Tertiary)

Extinct ion on northern continents

(mid Tertiary)

Reinvasion of N. America

(Quaternary)

Asian origin?

(early Cretaceou

Isolation of

southern continents

(late Cretaceous)

To S. America

(early Cretaceous)

To Antarctica & Australia

(early Tertiary)

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CLADOGRAM OF RECENT

MARSUPIALS

(outgroups)

Australodelphia

Ameridelphia

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MARSUPIAL CLASSIFICATION

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Marsupial Placental differences

Cranial & dental morphology

Didelphis Canis

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5 1 3 4

4 1 3 4________ 3-5 1 4-5 3

3-4 1 4-5 3__________= 50 = 44-54