Answer:
There are dozens of theories to explain a probable
cause or causes. Throughout the Mesozoic Era,
individual dinosaur species were evolving and becoming
extinct for various reasons. The unusually massive
extinction at the end of the Cretaceous exterminated
the last of the dinosaurs, the flying reptiles, and
the large swimming reptiles, as well as many other
marine animals. There is now widespread evidence that
a meteorite impact was at least the partial cause for
this extinction. Impact craters are visible on most
planets in our solar system. A spectacular example of
this was witnessed in 1994, when Jupiter was struck by
a series of cometary fragments. Some of these impact
blasts were larger than the Earth's diameter. Other
factors such as extensive release of volcanic gases,
climatic cooling (with related changes in ocean
currents and weather patterns), sea-level change, low
reproduction rates, poison gases from a comet, or
changes in the Earth's orbit or magnetic field may
have contributed to this extinction event.
