Most scientists agree that dinosaurs became extinct as a result of a catastrophic meteor strike 65 million years ago near the Yucatán Peninsula.

But now scientists are suggesting that another mass extinction event occurred about 200,000 years earlier: a volcanic eruption on the Deccan Plateau of India.

The eruption filled the atmosphere with aerosols — fine particles suspended in greenhouse gases that led to warming and, eventually, the extinction of much of marine life, especially shelled invertebrates on the ocean floor.

“This presents a more nuanced view of the extinction,” said Thomas S. Tobin, a paleontologist at the University of Washington and the study’s lead author. “It appears that both of these things happened in a short period of time.”