Final answer:
The mass extinction that caused the disappearance of most dinosaur species occurred approximately 65 million years ago due to the impact of a large asteroid in the Yucatán Peninsula.
Step-by-step explanation:
The mass extinction event that caused the disappearance of most dinosaur species (except birds) occurred approximately 65 million years ago.
The main cause of this extinction was the impact of a large asteroid in the present-day Yucatán Peninsula, which resulted in a subsequent release of energy and global climate changes caused by dust ejected into the atmosphere.