🐠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