What are they hunting in a sound of thunder that is so dangerous?

In Ray Bradbury's short story "A Sound of Thunder," the characters are hunting a Tyrannosaurus rex, a massive and dangerous dinosaur. The peril lies not only in the sheer size and ferocity of the creature but also in the consequences of their actions in the past, as even the smallest change can drastically alter the future. This theme highlights the interconnectedness of time and the potential ramifications of human interference with nature. The hunt serves as a cautionary tale about the risks of technological advancement and the fragility of ecosystems.