25.2 origin of mammals

Question 1

who did mammals evolve from

Answer 1

tetrapods callers synapsids

Question 2

synapsid (300 mya)

Answer 2

multiple bone jaw

• articulate quadrate hinge jaw
• pointy teeth
• temporal fenestra opening behind the eye socket

Question 3

therapsids (280 mya)

Answer 3

large dentary bones (jaw)

• specialized teeth (long canines)
• long faces
• articulate quadrate hinge jaw

Question 4

early cynodonts (260 mya)

Answer 4

• huge dentary
• cusps teeth
• articulate quadrate hinge jaw

Question 5

later cynodonts (220 mya)

Answer 5

complex cusps teeth

• two jaw hinges
• -articulate quadrate hinge jaw with new hinge

Question 6

very late cynodont (195 mya)

Answer 6

• lost the articulate quadrate hinge jaw
• leaving just the second hinge
• the articulate quadrate hinge moved to the ear and became the hammer an anvil