Final answer:
The decline of edge drilling in predatory snails is linked to massive environmental shifts following extinction events, including glaciation, warming, and changes to marine ecosystems that disrupted the food chain.
Step-by-step explanation:
The most likely reason for the dramatic decline of edge drilling in predatory snails after the mass extinction event approximately 2 million years ago is attributed to significant environmental changes.
These events, such as glaciation followed by warming, led to drastic climate changes which affected sea levels and temperatures, thereby impacting the marine food web and ecosystems. In particular, the Ordovician-Silurian extinction event, caused by cooling and then warming phases, resulted in the extinction of 85 percent of marine species.
Mass extinctions, including the end-Permian extinction, have historically been associated with factors like volcanic activity, meteorite impacts, and other colossal events that led to long-term ecological shifts such as reduction in available prey, habitat loss, and altered food chains, strongly affecting marine predators like snails that relied on specific prey or conditions.