Tetrapod evolution

Question 1

Tetrapodmorpha (infraclass, extinct)

Answer 1

• lungs and gills
• scales lost the dentine
• skull bones modified
• unique teeth (labyrinthodont dentition, dentin weird and squigled inside)
• bones of limbs distinct
• internal nostrils !!!

Question 2

Elpistostegids (tetrapodamorph fish, not official order)

Answer 2

• Lungs and gills
• paired fins
• no dorsal/anal fins
• dorsal eyes
• frontal bones more like tetrapods
• labyrinthodont dentition
• fish? maybe

Question 3

Tiktaalik roseae (genus) <3

Answer 3

Mix of primative and derived traits
* scales
* fin rays
* lower jaw and palate
* well developed gills
But also!
* short skull
* modified inner ear
* mobile neck
* functional wrist
* shallow water environment

Question 4

Stegocephali (not offical order)

Answer 4

• ~360 MYA
• limbs!
• Limb bones more robust - walking not swimming
• girdles more flexible
• mobile neck
• polydactyly (lots of digits)
  Fish like traits
• caudal fin - still swim?
• gills
• operculum
• labyrinthodont dentition

Question 5

Acanthostega -> Ichthyostega

Answer 5

• no caudal fin
• less digits
• nostrals
• ribs
• limb bones bigger

Question 6

Tulerpeton (species)

Answer 6

• 6 fingers and toes
• more robust limbs and girdles
• true neck (head disconnected from girdle)
• no gills

Question 7

How does a land animal evolve in water?

Answer 7

Shallow water! All terestrial characteristics help you survive in shallow waters

Question 8

Why transition to land?

Answer 8

Open niches
* less predation
* more food
* nursery - lay eggs in water (ex: small pond)

Question 9

Challenges: gravity

Answer 9

robust muscles and bone

Question 10

Challenges: drastic temperature changes

Answer 10

migrations/tropics

Question 11

Challenges: water loss

Answer 11

glands, thicker skin, swim

Question 12

Challenges: sensing the environment

Answer 12

update sensory organs

Question 13

Challenges: obtaining oxygen

Answer 13

well developed lungs, osmosis

Question 14

Challenges: reproduction without water

Answer 14

amniotic egg - in water

Question 15

Challenges: feeding

Answer 15

Teeth

Question 16

Challenges: getting rid of waste

Answer 16

bladder, kidney, excrete

Question 17

Possible ancestor of Tetrapods: Temnospondylii

Answer 17

• diverse
• large akinetic skulls
• global
• ~40 MY
• Successful
  MOST LIKELY

Question 18

Possible ancestor of Tetrapods: Lepidospondylii

Answer 18

• evolutionary dead end?
• unique vertebrae
• lack labyrinthodont dentition!
• small oddly shaped
• all habitats
• successful

Question 19

Possible ancestor of Tetrapods: Reptiliomorpha

Answer 19

• stem amniotes
• deep skull, kinetic
• aquatic eggs + larvae
• successful