“reptilian” vs mammalian dentition - university …courses.biology.utah.edu/rickart/5370/pdf...

“REPTILIAN” vs MAMMALIANDENTITION

MOLARS OF MESOZOICPROTOTHERIANS

MOLARS OF MULTITUBERCULATES& MONOTREMES

MultituberculataPtilodus

MonotremataObdurodon Ornithorhynchus

EVOLUTION OF THERIAN MOLARS

Tribosphenic

THERIAN (TRIBOSPHENIC) MOLARS

(occlusal view)

(lateral view)

upper

lower

TRIBOSPHENIC MOLAR OCCLUSION

Quadrate or Bunodont(primate)

Dilambdodont(insectivore)

Variations on Tribosphenic molar

ectoloph

MOLARS – crowns & roots

Lophodont molar (murid rodents)

Selenodont molar (artiodactyls)

Loxodont molar

(elephant)

(capybara)

DENTAL FORMULACanis lupus

I C P M3 1 4 2

Upper dentition(one side only)

1 1 4 3I c p m

Lower dentition(one side only)

3 1 4 2________3 1 4 3

(x 2) = 42

DENTAL FORMULAS

Extreme dentitions

Nine-banded armadillo (Dasypus)simplification and reduction

Common dolphin (Delphinus) simplification and multiplication

EARLY MAMMAL GROUPS

ORDER SYMMETRODONTA basal therians

Kuehneotheriumlate Triassic – early JurassicEurope

Vincelestesearly Cretaceus, Argentina

HadrocodiumearlyJurassic, China

SYMMETRODONTSLoss of post-dentary bones in lower jaw

Hadrocodon (Docodont, Prototherian)

Hadrocodium (Symmetrodont, basal Therian)

SYMMETRODONTMolar structure

OLDEST MARSUPIAL?Sinodelphys -- early Cretaceous (China)

4 1 4 44 1 4 3 = 50

OLDEST EUTHERIAN ?Eomaia -- early Cretaceous (China)

5 1 5 34 1 5 3

_______ = 54

EARLY EUTHERIANUkhaatherium late Cretaceus, Mongolia

5 1 4 3_________ = 504 1 4 3

Skulls of early therians

Skulls of early therians

EARLY METATHERIANORDER: DIDELPHIMORPHIAFamily: DidephildaeAlphadon (Late Createous, N. America)

5 1 3 44 1 3 4

= 50

MARSUPIAL BIOGEOGRAPHY

To N. Americaearly diversification

(late Cretaceous)

Ameridelphiandiversification

(late Cretaceous)

AustralodelphianIsolation and diversification

(Tertiary)

Extinction on northern continents(mid Tertiary)

Reinvasion of N. America(Quaternary)

Asian origin?(early Cretaceous)

Isolation of southern continents

(late Cretaceous)

To S. America(early Cretaceous)

To Antarctica & Australia(early Tertiary)

CLADOGRAM OF RECENTMARSUPIALS

(outgroups)

Australodelphia

Ameridelphia

MARSUPIAL CLASSIFICATION

Marsupial – Placental differencesCranial & dental morphology

Didelphis Canis

5 1 3 44 1 3 4

________ 3-5 1 4-5 33-4 1 4-5 3__________= 50 = 44-54