What type of fish went extinct during the Cretaceous period?

During the Cretaceous period, several types of fish went extinct, including many species of bony fish (Osteichthyes) and cartilaginous fish (Chondrichthyes). Notably, the group of fish known as the "Hybodus," which were early relatives of modern sharks, faced significant declines. The mass extinction event at the end of the Cretaceous led to the loss of approximately 75% of all species, including many marine fish. This extinction paved the way for the diversification of modern fish species in subsequent eras.