What happened at the end of the mesozoic era, but did not happen at the end
of the paleozoic era?

The end of Mesozoic era resulted in the end of dinosaurs. Due to falling of material in the Gulf of Mexico.  

Explanation:

The life of Mesozoic era is from 252 million years to 66 million years. this was the age of major dinosaurs, reptiles’ birds etc. The Paleozoic era was of organism which dominated the ocean and sea area. After the end of Mesozoic era it was very difficult to regain life again on the earth.

It took several years for the life to be exist again on earth after the meteor catastrophe. There were a lot of life that got disturbed and extinct during that phase. It happened due to the natural phenomenon, that is falling of meteor on the earth surface. It impacted the earth a lot.

the answer is: metamorphic rocks often show the presence of fossils, also a

hope i

-lavira: )