🐠Terrestrial Fossils 🐟
Coelacanth
Rediscovered in 1938
Off the Comoros Islands
150-300m depth
Was believed to be extinct
More than 65 mill yrs ago
Their close relatives became the first vertebrates to venture on land
Share the oceans with trilobites and primitive molluscs
Almost to modern coelacanths
Limb like ventral fin and pectoral fin
Made it possible for fish to crawl out the sea
Closets living relatives to the ancestor of all amphibians, reptiles, birds, mammals
Reached its peak 200 mill years ago
could be the lungfish
Todays numbers are low
Lobe finned fish 🐡
Amphibians
First land dwelling creatures with four legs 🍗
Evolved from lobe finned fish
Tetrapod's
Ventured into terrestrial environments 🥀
Late Devonian to early Carboniferous
Then evolved into reptiles, birds, mammals
Lungfish
Can breathe in and out of water
Robust fleshy fins
Evolved functional lungs
Modified swim bladders
Allowed them to breathe out of water
Could start the transition to land
Could move from one source of water to another
Could exploit new niches
Central bones inside
How do we know?
More mobility and support
especially on land
Disadvantage
no strengthening girdle
Area of weakness
between limb and rest of the skeleton
Fins would later evolve into limbs
Allowing permanent life on land
Live specimens found today
Fossils found in Devonian strata
Coelacanths
Thought to be extinct
''living fossils''
Virtually unchanged for 400ma
Marine fish that don't have lungs
🐟Similarities between lobe-finned fish and early amphibians🐸
Four fins of lobe finned fish and early amphibians were skeletally similar
Limbs were in the same positions on their bodies
Both lacked claws and nails
Skull morphology, the jaw bones, and teeth are similar
Amphibians skull became slender,
temporal and opercula bones becoming smaller
Jaw bones becoming fused together
Teeth of bother were very complex
Early Amphibians still had a tail fin
Suggests they spent a long time in water
Body shape/movement resembled lobe finned fish
Early amphibians had small bony scales on skin
Trait of fish
Adaptations to life on land 🌄
Unique features allowed them to adapt
Development of skeleton girdle
Connecting limb bones to skeleton bones
Allows better movement
More robust skeleton
Strengthening the vertebral column and rib bones
Extra support on land
Eyelids formed to keep eyes moist
No longer always submerged in water
Double circulatory system
Three chambered heart to pump mixed blood
More efficient gas exchange
More active cells with oxygen
Helps remove waste more efficiently
A tongue formed within its mouth
Used to catch prey
Sensory role
Ears to detect soundwaves
Could listen for prey or predators
Had to:
Remain close to water
Use their skin for gas exchange
Had to keep their skin moist for transfer of oxygen and carbon dioxide
Lay eggs in water as they would dry out
Young hatch into aquatic larvae with gills
Only protected by jelly and not a shell
Undergo metamorphism to develop into a terrestrial adult
Amniotic eggs
Lead to dinosaurs, birds and mammals