Tetrapod evolution Flashcards
Tetrapodmorpha (infraclass, extinct)
- 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 !!!
Elpistostegids (tetrapodamorph fish, not official order)
- Lungs and gills
- paired fins
- no dorsal/anal fins
- dorsal eyes
- frontal bones more like tetrapods
- labyrinthodont dentition
- fish? maybe
Tiktaalik roseae (genus) <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
Stegocephali (not offical order)
- ~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
Acanthostega -> Ichthyostega
- no caudal fin
- less digits
- nostrals
- ribs
- limb bones bigger
Tulerpeton (species)
- 6 fingers and toes
- more robust limbs and girdles
- true neck (head disconnected from girdle)
- no gills
How does a land animal evolve in water?
Shallow water! All terestrial characteristics help you survive in shallow waters
Why transition to land?
Open niches
* less predation
* more food
* nursery - lay eggs in water (ex: small pond)
Challenges: gravity
robust muscles and bone
Challenges: drastic temperature changes
migrations/tropics
Challenges: water loss
glands, thicker skin, swim
Challenges: sensing the environment
update sensory organs
Challenges: obtaining oxygen
well developed lungs, osmosis
Challenges: reproduction without water
amniotic egg - in water
Challenges: feeding
Teeth
