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Flashcards in Vertebrate of BC Part 2 Deck (484)
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91

synapsids were most abundant tetrapods when

Paleozoic

92

mammal body size

10-500kg

93

Pelycosaurs

Dimetrodon, tailback, carnivorous, herbivorous, sprawling limbs, long toes
Laurasia- warm, moist

94

Pelycosaur jaw

teeth mostly homodont except canine
first evidence of tooth differentiation

95

end of permian, mammals

most life dies, therapsids survive, diapsids take over, rise of large croc., mammals almost extinct from Jurassic, re-diversify KTB

96

Pelycosaur thermoregulation

elongated neural spines, heavily vascularized, thermoregulation, some of first modifications towards endothermy

97

homodont teeth

all the same

98

mammal lower jaw

1 bone - dentary
only bone with teeth
(3 bones including hinge)

99

mammal jaw hinge

articular (bottom) and quadrate (top)

100

Therapsids time

early Permian

101

Therapsid characteristics

very large temporal fenestra
tooth differentiation
palate development
pelvic and pectoral girdles
limbs thinner, joints more flexible
short foot, toes
limbs move for upright posture

102

almost all modern mammal teeth type

heterodont

103

Therapsid tooth differentiation

incisors
canines
post-canine

104

why arched palate?

breathe and eat

105

why short foot/toes?

running faster

106

importance of hind limb muscles in mammal development

movement of limbs without moving entire body side to side
muscles connected to iliac blade rather than lateral process

107

where therapsids diversified

Laurasia and Gondwana
cooler, less aquatic habitats

108

Therapsid size

rodent - cow

109

Dominant terrestrial tetrapods of the late Permian

Therapsids

110

Major Therapsid extinction end of Permian, 3 groups survive

dicynodonts
theriodonts
cynodonts

111

dicynodonts

herbivore, loss of molar teeth, horny sheath (like turtle), two tusks, derived jaw articulation- lateral movement for grinding

112

Theriodonts

dominant predator, coronoid process on dentary

113

coronoid process

a flattened triangular projection above the angle of the jaw where the temporalis muscle is attached-- increased jaw closing strength

114

cynodonts

dog-sized carnivore, multicast molars, enlarged coronoid process

115

evolution of iliac process

evolution of running

116

fate of 3 remaining therapsid groups

displaced by diapsids in Tri, mostly extinct by end of Triassic

117

cynodont fate

progressive reduction in size, several small groups persist through K

118

persistent cynodonts

zygomatic arch, sculpted, heavily vascularized jaw, surface glands, enlarged infraorbital foramen, innervated face, turbinate bones, possible heterothermy or fully endothermic, 7 cervical vertebrae

119

infraorbital foramen

sensory nerves to brain (for innervated face)

120

innervated face

whiskers