Final answer:
The Cambrian period is the earliest period during which animals may have appeared, known for the Cambrian explosion where a significant number of animal phyla emerged.
Step-by-step explanation:
The earliest period during which animals may have appeared, according to geological records, is the Cambrian period. This period is known for the Cambrian explosion, a crucial event in the history of life on Earth where there was a rapid diversification and evolution of animal species. The Cambrian period predates the other periods listed - the Jurassic, Permian, and Devonian.
While there is evidence suggesting that simple animal life existed during the Pre-Cambrian times, specifically in the Ediacaran period, the Cambrian period, which lasted from 541 to 485 million years ago, clearly marks the appearance of most major animal phyla known today. Prior to the Cambrian, life forms were simpler, and it was during the Cambrian that more complex and diverse organisms began to emerge in the fossil record.