20. Which of the following periods is known as “Age of fishes”?
(1) Devonian                                                  (2) Jurassic
(3) Cambrian                                                  (4) Carboniferous

Introduction

The story of life on Earth is marked by extraordinary evolutionary milestones, and one of the most remarkable chapters is the Devonian Period. Often referred to as the “Age of Fishes,” the Devonian witnessed an unprecedented explosion in the diversity, abundance, and complexity of fish. This era not only shaped aquatic ecosystems but also set the stage for the evolution of amphibians and the colonization of land.

Why Is the Devonian Called the “Age of Fishes”?

• The Devonian Period spanned from about 419 million to 359 million years ago and is part of the Paleozoic Era124.

• During this time, fish experienced rapid diversification and became the dominant vertebrates in the world’s oceans, lakes, and rivers356.

• The period saw the rise of several major groups of fish, including:

  • Jawless fish (agnathans)

  • Armored placoderms—some of the first jawed fish, known for their bony armor and impressive size

  • Cartilaginous fish—early sharks and rays

  • Lobe-finned fish—ancestors of the first land vertebrates

  • Ray-finned fish—which would later become the most abundant fish group today567.

Evolutionary Advancements

• Fish developed new anatomical features, such as jaws and paired fins, which allowed them to exploit new ecological niches and become effective predators15.

• The Devonian seas were filled with a variety of bizarre and formidable fish, including the giant placoderm Dunkleosteus, which could grow up to 33 feet long35.

• Many of the evolutionary innovations in fish anatomy and behavior during this period laid the groundwork for future vertebrate evolution, including the eventual emergence of amphibians and terrestrial life6.

Broader Impact on Life

• While the Devonian is most famous for its fish, it was also a time of significant change for other life forms:

  • The first forests appeared, and terrestrial plants diversified rapidly.

  • The first tetrapods (four-limbed vertebrates) began to emerge from lobe-finned fish, marking the transition from water to land6.

  • Marine ecosystems flourished with corals, brachiopods, and ammonites.

The Correct Answer

Given the options:

1. Devonian

2. Jurassic

3. Cambrian

4. Carboniferous

The correct answer is:

(1) Devonian

Conclusion

The Devonian Period is rightfully known as the “Age of Fishes” due to the incredible diversity and evolutionary advancements of fish during this era. This period set the stage for the rise of amphibians and the eventual conquest of land, making it one of the most significant chapters in the history of life on Earth