What other animals became extinct?

 

                  The extinction of the dinosaurs was not an isolated event. At the same time most marine reptiles and pterosaurs also died out. Also, tiny plankton whose shells form chalk deposits became extinct, as well as ammonites and the remaining species of trilobites. It is very difficult to imagine the causes of this extinction. For example, why did turtles survive, while marine reptiles, well adapted to their environment, such as ichthyosaurs, died out?