Paleo

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Chapter 4 “Reptile”

Mammalian Origins

Early mammal

Carnivore

Amniota

Herbivore
Feldhamer Table 4.1 Savage and Long 1986

Fig. 3.2, Vaughn, Fig. 4.1,Feldhamer

Mammalian Origins
Overview Synapsids Pelycosaurs and Therapsids First Mammals Mesozoic Era appear Cenozoic Era radiate

Major groups of Synapsida

Dimetrodon

Feldhamer Fig. 4.2Savage and Long 1986

Skull, jaw musculature, and teeth
Pelycosaur

Pelycosaur

Cynodontia -- Advanced, predaceous therapsids
Scymnognathus Cynognathus

Therapsid

Early Cynodont

DerivedTherapsid/Mammal Late Cynodont

Primitive

Fig. 3.2, Vaughn

Fig 4.3 & 4, Feldhamer

Thrinaxodon

1

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Skeletal transition
Pelycosaur Fig. 4.15Extinction of Cynodonts
Possibly competition from dinosaurs Early Cynodonts were dog-size, last surviving were squirrel sized Mammals that survived while Cynodonts went extinct (contemporary) weremouse-sized.

Cynodont

Thrinaxodon

Fig. 3.5, Vaughn

Modern Mammal
Fig. 4.16c, Early Cynodont

Early mammals
200 - 250 million years ago Derived characters: Dentary/squamosal jaw articulationDiphyodont dentition Mammary glands Secondary palate Viviparity (loss of eggshell) When?

Feldhamer 4.11

Changes in land masses
180 MYA MidJurassic

200 MYA Early Jurassic

135 MYA EarlyCretaceous
Feldhamer 4.5, 4.9

65 MYA Early Cenozoic

Skull and teeth of mammals

2

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Teeth and Dentition of Mammals

Teeth
One of the major keys to success ofmammals Teeth of mammals are extremely variable with different diets -more than other taxa

Heterodont teeth with different functions Differentiated on the basis of function, resulting in increasedefficiency acquiring and digesting food. Teeth occur in 3 bones of skull: premaxilla, maxilla, dentary

Feldhamer et al.

Additional Notes on Tooth Structure Not all teeth have enamel over entire...