evolution of amphibians 🐸

• Amphibians were the first land dwelling animals - called tetrapods. They evolved from lobe finned fish in the late Devonian/early Cambrian. 
• Lobe finned fish have similar bones in their fins to hands - allowing mobility on land. They had no strengthening girdle to connect their fin bones to their body. This meant they could not support their body. These fins evolved into amphibian limbs. 
• Some lobe finned fish could breathe on land - from a modification of their swim bladders. They could move between water sources. 
• Coelacanths are a lobe finned fish. They have not changed in millions of years and have limb like fins. They have declined in number since the Triassic. 
• Ichthyostega and tiktaalik were the first amphibians. They had similar limb positions to lobe finned fish, they had no claws and nails and had similar jaw bones and teeth. Early amphibians still had tails and scales, they were also streamlined meaning they spent time underwater. 
• Early amphibians had a girdle to connect their skeletons, the skeletons were stronger and they formed eyelids to maintain eye moisture. 
• Ichthyostega and tiktaalik used their limbs for motion and their tails for balance. They still returned to water to lay eggs and their young were aquatic.