Blackwell Publishing
Precambrian Paleozoic Mesozoic Cainozoic
Triassic 248 MYRBP Jurassic 213 MYRBP Cretaceous 144 MYRBP

The 160 million year reign of the dinosaurs ended in a mass extinction at the end of the Cretaceous. There are several possible explanations for this:

• extraterrestrial catastrophe - there is evidence that a huge meteorite struck the earth, causing a sudden drop in temperature because of dust in the air.

• "racial senescence" - the dinosaur group had accumulated genetic and historical constraints preventing effective adaptation to environmental .

• vulcanism - widespread vulcanic activity may have flooded the land with lava, causing many extinctions.

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