However, we can trace the evolution of fishes within this timeline:
* Early Paleozoic Era (Cambrian Period, 541-485 million years ago): The first fish-like creatures, known as conodonts, appeared. These were small, jawless, eel-like creatures.
* Late Paleozoic Era (Silurian Period, 443-419 million years ago): Jawed fishes emerged. These early fishes had bony armor and fins.
* Late Paleozoic Era (Devonian Period, 419-359 million years ago): This period is often called the "Age of Fishes." It saw a huge diversification of fishes, including placoderms (armored fishes), acanthodians (spiny sharks), and lobe-finned fishes. This period also saw the emergence of the first tetrapods (four-legged vertebrates) which evolved from lobe-finned fishes.
* Mesozoic Era (Triassic Period, 252-201 million years ago): Ray-finned fishes began to dominate the aquatic environments. They developed a wide range of adaptations for various habitats.
* Mesozoic Era (Jurassic Period, 201-145 million years ago): Bony fishes continued to diversify. The first teleosts (modern bony fishes) appeared.
* Mesozoic Era (Cretaceous Period, 145-66 million years ago): The teleosts rapidly diversified and became the most abundant and successful group of fishes.
* Cenozoic Era (Paleogene and Neogene Periods, 66 million years ago to present): Teleosts continued to diversify and dominate marine and freshwater environments. New adaptations evolved, including specialized feeding behaviors and different body shapes.
So, while there's no dedicated "geological time scale for fishes," we can understand their evolutionary history within the existing geologic time scale.
