Pre-Mammalian Phylogeny and Diversification

What time frame is Synapsida from

Permian (300 mya)

Synapsida characteristics

• Canine teeth

• Jaw muscles move to outer brain

Extra Synapsids

• Pelycosauria (late Carboniferous)

• Therapsida (top carnivores in Permian to Triassic)

Dimotrodon

early Permian creature with fin on back for thermoregulation

Late Permian Pangaea

super continent, when most/all land mass was connected

Therapsid Characteristics

• Feet shortened

• Upright limb posture

• Deep hip joint

• Ear opening (due to squamosal)

• Simplicity of lower jaw (formation of Dentary)

• Glandular skin

Amonodonts/Dicynodonts

Late Permian and Triassic herbivores with beaks and tusks

Next-wave Dinocephalians herbivore

Amonodonts/Dicynodonts

Next-wave Dinocephalians carnivore

Theriodonts/Gorgonopsians

Theriodonts/Gorgonopsians

late Permian hunters

Therocephalians

early Triassic dicynodont hunters

How to survive low O2 levels (150 mya)

• low metabolism, small size, hibernating

• high metabolism, extract O2 more efficiently

• High metabolism, faster deep breaths, but small

Cynodontia Characteristics

• multicusped teeth

• Upper jaw bones meet to form secondary plate

• zygomatic arch

• reduced ribs for locomotion

• semi-erect limb

• skin/muscles to direct sound waves to ear

• hairs to sense nocturnal env.

• neocortex

• olecranon process

Morganucodon characteristics

• Squamosal-dentary jaw joint

• Molars

• Diphyodonty

• long hip

• Angular, Quadrate, Articulate bones moved to ear

Diphyodonty

when baby teeth are replaced

Olecranon Process

four-wheel drive with triceps (muscle attachment)

Multicusped teeth

complex grinding occlusion