What do the cretaceous and ordovician periods have in common?

The Cretaceous and Ordovician periods, both significant divisions of the geological time scale, are marked by distinct evolutionary advancements and environmental changes. They each experienced major diversification of marine life; the Ordovician is known for the explosion of marine organisms, while the Cretaceous saw the rise of dinosaurs and flowering plants. Both periods also ended with mass extinction events, which dramatically reshaped the Earth's biological landscape. Additionally, they represent key intervals in Earth's history where tectonic activities and climate changes significantly influenced the distribution of life.