"Daikyouryu Jidai" is a science fiction anime series that explores themes of time travel, prehistoric life, and human resilience. The story centers on a group of individuals who are transported back in time to the Cretaceous period, where they must navigate a world dominated by dinosaurs and other ancient creatures. The narrative begins with a mysterious phenomenon that causes a sudden temporal displacement, stranding the characters in a hostile and unfamiliar environment.

The main characters include a diverse ensemble of scientists, adventurers, and ordinary people, each bringing unique skills and perspectives to their struggle for survival. Among them is a paleontologist whose expertise proves invaluable in understanding the prehistoric ecosystem, a resourceful engineer who devises tools and shelters, and a young student whose curiosity and adaptability become crucial in their journey. As they band together, the group faces numerous challenges, including predatory dinosaurs, natural disasters, and the psychological toll of their isolation.

The plot unfolds as the characters attempt to uncover the cause of their time displacement and find a way to return to their own era. Along the way, they encounter remnants of an ancient civilization, suggesting that humans may have existed in this time period long before recorded history. This discovery raises questions about the nature of time and humanity's place in the universe. The series balances action-packed sequences with moments of introspection, as the characters grapple with their fears, relationships, and the moral dilemmas of altering the past.

Throughout the series, the group's survival depends on their ability to adapt and cooperate, highlighting themes of teamwork and ingenuity. The narrative also delves into the ethical implications of scientific exploration and the consequences of human interference with natural history. As the story progresses, the characters uncover clues that hint at a larger, interconnected mystery involving time travel and the origins of life on Earth. The series concludes with a mix of resolution and open-ended questions, leaving room for interpretation and further exploration of its rich, prehistoric world.