They proposed that the causal agent was a climatic cataclysm, resulting from the impact of a bolide .
It has even been speculated that if a bolide had not seen out the dinosaurs, then they would have eventually evolved into a human-grade intelligent species.
The size and age of lunar impact structures and astronomical observations of asteroids and comets point to numerous large bolide impacts early in Earth history, but geological evidence for these impacts is rare and controversial.
The bolide probably prolonged and intensified the change, and may have weighed heavily in favor of mammals or birds and against non - avian dinosaurs.
The impact scenario is based upon the occurrence of considerable widespread evidence of a large bolide striking the Earth.
And an expert at Jodrell Bank Observatory in Cheshire believes the cause could be a bolide - a meteor between the size of a hazelnut and a tennis ball.
Ever since the proposal that the mass extinction resulted from a bolide impact, the nature of mass extinctions has been the subject of much debate.
What may have been a bolide of a white spherical type crossed the sky over Buenos Aires and was seen by dozens of people.’
That pattern suggests that an object may have struck from the northwest - a path that would have taken the blazing bolide over southeastern Australia, where aboriginal legends mention just such a fireball.
Almost everything that could have gone wrong did: A huge bolide , or asteroid, struck Earth.