What appeared at the beginning of cretaceous period?

At the beginning of the Cretaceous period, around 145 million years ago, there was a significant diversification of dinosaurs, with many new species emerging. This period also saw the rise of flowering plants (angiOSperms), which began to dominate terrestrial ecosystems. Additionally, marine life flourished, with the appearance of various mollusks, including belemnites and ammonites, and the presence of large marine reptiles. Overall, the Cretaceous marked a time of substantial evolutionary advancements and ecological changes.