Small, burrowing ornithopods survive KPG extinction event

Scenario: Fast forward from the KPG extinction event around 66 million years ago to present day, imagine our world where small burrowing ornithopod dinosaurs, akin to Oryctodromeus, survived the catastrophe while evolving alongside birds and mammals. Unlike their hefty brethren, these relatively tiny and resourceful dinosaurs managed to stay alive in their underground burrows that provided a safe refuge from the catastrophic fallout that wiped most of their kin off the face of the earth. Initially, these miniature dinosaurs struggled to survive in the aftermath of the asteroid impact due to the scarcity of vegetation which was their primary food source. However, their small size, swift movement, and burrowing habits allowed them to access food sources that larger animals couldn't and their nemesis, the larger predatory dinosaurs, were extinct. Over millions of years, they evolved to have a more diverse diet, similar to modern day birds. Some species developed omnivorous feeding habits, consuming insects, small mammals, and birds. Their teeth evolved to help them with new types of food, becoming sharper and more adapted for catching and eating small animals or grinding plant materials. This dietary expansion played a substantial role in their successful survival and evolution. Their segmented societies evolved into more sophisticated social structures, much like prairie dogs today. Using their burrows not only for protection but also for communication, they evolved complex signaling systems that allowed them to warn each other of predators or environmental hazards. The Ornithopods also developed a symbiotic relationship with smaller birds; these birds would eat parasites off the dinosaurs and in return, the birds would be protected in the vast network of dinosaur burrows. Physically, the burrowing ornithopod dinosaurs developed stronger forelimbs and specialised claws for more efficient burrowing. Their hind legs adapted for short, fast sprints to escape predators and they grew feathers, not for flight but for thermal regulation and possibly display during mating rituals. These small ornithopods would have a significant influence on their ecosystems. Their burrowing activities would improve soil health and also create habitats for other small creatures. Their diverse diets would control overpopulation of certain species while their roles as prey would support a plethora of predators, contributing to an intricate and balanced web of life within their ecosystems. In this way, with the survival and evolution of burrowing ornithopod dinosaurs, our world would be a more diverse and interesting place, demonstrating the remarkable resilience and adaptability of life.