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