anciently preceded by the

The mist clung to the cliffs like a burial shroud, obscuring the layers of sediment that stretched down into darkness. Dr. Rivera traced her gloved finger along a thin black band in the rock face - the iridium layer, anciently preceded by the presumed far more extensive mass extinction. Even after decades of research, this boundary still sent chills through her.

Above that dark line lay scattered fossils of early mammals, tentative pioneers in a devastated world. Below, the rock told stories of lost dynasties - the last of the non-avian dinosaurs, the marine reptiles, the ammonites, all erased in a cosmic instant. But this wasn’t the greatest die-off she’d studied. That honor belonged to the Permian extinction, nearly two hundred million years earlier, when over ninety percent of species vanished.

The beam of her headlamp caught something embedded in the rock - a fragment of bone, perhaps, or a tooth. But as she leaned in closer, the ground beneath her feet shifted almost imperceptibly, and a deep rumble echoed through the canyon. Nature, it seemed, wasn’t finished writing its stories of extinction.