devonian fishes (ancient) forests (first trees)...
TRANSCRIPT
The 4 F’s of the
DEVONIAN
Fishes (ancient)
Fingers (tetrapod digits)
Forests (first trees)
Finished (extinctions)
495 mya
66 mya
120 mya
201 mya
252 mya
300 mya
365 mya
443 mya
Present Day
adapted from http://jan.ucc.nau.edu/rcb7/globaltext2.html
Jawless Fishes
• Hagfishes, lampreys
• Ostracoderms
– Heavily armored,
jawless, filter-feeding
Placoderms • Heavily armored
• Jawed Mouth
Gill slits Cranium
Skeletal rods
Chondrichthyes
• Cartilaginous fish: Sharks, rays
Mississippian sharks with crinoids
“True” Bony Fish
• Internal skeleton, fins, jaws
– good swimmers
Phylum Chordata Vertebrata
Cl Osteichthyes living ceolacanth
• Phylum Animalia
– Phylum chordata
• Subphylum vertebrata
– Superclass Tetrapoda
» Class Amphibia
» Class Reptilia (Sauropsida)
» (Class Aves)
» Class Mammalia
Class Amphibia
• Devonian to recent
• Frogs, toads, salamanders
• Characteristics
– Tetrapods
– Water needed for reproduction
– Ectothermic
– Gills and lungs
Why come out on land??
Dry period – need to find another water hole?
Why come out on land??
Predators – live in shallow water or on land to avoid large marine predators
Lungfish
• Heavy fins on underside
– can crawl
• Auxiliary lung
– can breath
• In Devonian, fossils are found in lakes and ponds
https://en.wikipedia.org/wiki/Tiktaalik
Hypothesized Sweet-Spot
https://en.wikipedia.org/wiki/Tiktaalik
365 mya
Tiktaalik
• Devonian
• Is a fish, not a tetrapod
• Fins present
– Bone structure similar to limbs
(digits)
• Skull transitions in the
direction of Amphibians and
Reptiles
Acanthostega • Late Devonian, Spitzbergen
• Found in lake and pond deposits
• True tetrapod, not a fish
• Large tail and rear limbs suggest lived in water
• If lived in water then evolution of tetrapods took place in water – Limbs were developed for life in
water
https://en.wikipedia.org/wiki/Tiktaalik
https://en.wikipedia.org/wiki/Tiktaalik