Scientists found many different types of fossils in a rock layer, which was dated at 251–299 million years old using an index fossil. In layers directly above that point, scientists found a large decrease in the number of fossils, particularly of marine and insect fossils. When did the extinction event occur?

i think it is due maybe a lack of food for animals on land.

Explanation:

It did not affect the water animals because they had food underwater. i don't know when it happened but just google your question.

the roman republic began to expand when rome fought the punic wars and defeated carthage. the punic wars refer to the series of 3 wars fought among rome and carthage, before it ended in carthage's defeat.