The Evolution of the Australian Animal fauna after the KPG extinction event.

In the alternate timeline, the KPG extinction event that marked the end of the Cretaceous era was averted from Australia. This was due to a geological anomaly that created a natural barrier against the impact's dust cloud, sparing the continent and preserving its numerous wildlife inhabitants. Over the next 66 million years, these prehistoric animals would continue to evolve concurrently with the species we know. The rich and diverse ecosystem of Australia provided ample opportunities for the evolution of these now-extinct species into something altogether new. Non-avian dinosaurs, long thought to have been extinct, took on new forms in this Australia. Dinosaurs like Australovenator, a mid-sized theropod, evolved to fill the ecological niches similar to that of the apex predators. Over millions of years of evolution, these theropods could evolve features for better hot climate adaptability and speed, becoming the ultimate predators of this new Australian landscape. Muttaburrasaurus, a large herbivorous dinosaur, being the main grazing dinosaurs, may have evolved similarly to how elephants have, becoming somewhat smaller but still serving the same purpose ecologically. Even the Minmi, an armored dinosaur native to Australia, could have taken different paths. They may have evolved a more spiky, aggressive form to defend against the new breed of predators or retained their slow, armored physiology diversifying into distinct subsets akin to tortoises and turtles. Early Cretaceous pterosaurs, which were on decline in other parts of the world, flourished here with Australia's isolation fostering winged giants akin to Quetzalcoatlus or Hatzegopteryx. Marsupials co-evolved with these adapted dinosaurs, with some of the larger predatory marsupials like the Thylacoleo (Marsupial Lion) becoming more specialized in hunting smaller dinosaur species that evolved from Minmi and other herbivorous dinosaurs. Kangaroos and wallabies would have to become faster and more agile to evade these new breed of predatory theropods. Australia's diverse bird population would have evolved alongside these dinosaur descendants. Many existing bird species, like the Emu, developed longer legs and heightened agility to avoid predators. Thus, the Emu of this timeline may resemble a roadrunner or secretary bird more than the modern-world Emu. The reptile population would likewise adapt. Goannas and other large lizards could emerge larger and more diverse, possibly even taking to an arboreal lifestyle to avoid the ground-based chaos. Meanwhile, the continent's snake population could evolve to resemble the Titanoboa, as these massive predators would be the perfect opponents for dinosaur hatchlings and marsupial cubs. At the heart of it, all the species we know today would still exist but possibly with striking differences. The evolution of species is ultimately guided by the paths of survival they choose, shaped by the ecosystem around them. In our alternate Australia, these paths are shared with dinosaurs, a fascinating test of strength, adaptability, and resilience.