How is the fossil record evidence for evolution? apex

Fossils show how a certain species has changed and adapted over different times. Take dinosaurs for example. Icthysaurus, a fish like ocean dwelling Dino, evolved into the common fish we know today! They gained gills to breathe on water, but the skeletons are relatively similar, though considering the fact that your typical goldfish is about 100 times smaller than Icthysaurus.