I am working on a world where giant tortoise-like animals wiped out the majority of the planet's ecosystem. The planet has on large continent near the equator that once was covered in lush rainforests. However, an animal evolved to take full advantage of this lush environment. These creatures formally named Magnus Clydeus (Courtesy of fellow Worldbuilding user @StephenG). These animal's bodies were so efficient that their waste was unusable for any decomposers currently on that planet. This lead to Magnus Clydeus eating the entirity of the rainforsts save for any places which they could not traverse such as bowl craters. This resulted in the continent becoming a massive dustbowl dessert. Without their constant supply of food, Magnus Clydeus went extinct. These animals had no natural predators past their juvinille stage, giving them free reign. However, oce these animals die, they simply drop to the ground, leaving behind massive cadavers. Could stable ecosystems arise within the sheltered sanctuary that the shells of these rotting giants provide?.
The shells and overall skeleton would be sturdy enough to persist for thousands of years after death. Once the body is decomposed enough, the shell would be hollow and jam packed full of nutrient rich remains. This would be converted into soil by later decomposers which would allow for plant life to thrive.