The Isle of the dinosaurs

In this alternative scenario, the Cretaceous Island, as it now comes to be known, became the final refuge for a myriad of extraordinarily diverse dinosaur species and other prehistoric creatures. The Island is a vast, twice the size of New Zealand, with forests, swamps, and open fields sprawling under a mix of tropical and temperate climates. The brutal impact of the KPG mass extinction event never reached this hidden sanctuary, leaving its biome undisturbed for these giant inhabitants. In the forest and swamps, the tyrannosaurs - now more arboreal and sporting dazzling colorations for camouflage - stalk the land, hunting the herbivorous dinosaurs such as hadrosaurs and thescelosaurids which have also adapted to be more alert and quick-footed. The dromaeosaurs, on the other hand, have broadened their evolutionary range, with some species adopting semi-aquatic traits and hunting in the swamps while others have evolved into top tree-dwelling predators. The therizinosaurs, with their long claws and imposing stature, stand as gentle giants, living off the island's abundant vegetation while defending themselves from potential threats. Some oviraptorosaurs have evolved into creatures more akin to flightless birds, racing through the open fields to forage and nest, escaping the predatory eyes in the forest. Ornithomimosaurs have also taken advantage of the open fields, evolving into even swifter runners, dodging predators and catching small insects and lizards. Ceratopsians, ankylosaurs, and pachycephalosaurs have maintained their defensive evolution. With no large mammalian predators to challenge them, they've become some of the Cretaceous Island's toughest inhabitants with advanced defensive adaptations, some resembling walking fortresses with their richly decorated and armored bodies. The skies of the island are filled with a cacophony of pterosaurs, which have evolved to fulfill many of the roles occupied by birds on the mainland. Some have evolved to be large, soaring predators or scavengers while others have become smaller, insect-eating species. The small cretaceous crocodiles and champsosaurs thrive in the island’s waterways, with some even evolving to tax the open oceans. In the lower strata of the ecosystem, polyglyphanodontian lizards have evolved into an array of forms, from small insectivores to larger herbivorous species, even adding more diversity to the existing ecosystem. The arrival of humans in the late Pleistocene or early Holocene marked a new era. With knowledge and understanding, they had developed a co-existing relationship with the island's prehistoric inhabitants, establishing their tribes and settlements without disturbing the thriving Cenozoic ecosystem. With the ability of the human settlers to instigate controlled burns for agriculture, some dinosaur species have even evolved to take advantage of these fire-based ecosystems, reminiscent of Australia’s fire-adapted fauna. This balance of power between man and beast continues, making the Cretaceous island a living testament to a bygone era.