Unfortunately Dinosaurs became extinct at the end of the Cretaceous Period, around 65 million years ago. The cause of the mass extinction that wiped these creatures out, & marks the end of the Cretaceous and the beginning of the Paleogene period, remains a scientific mystery!
Scientists tend to be locked on to one of two hypotheses that may explain the catastrophic natural disaster that created this extinction, either an extreme asteroid or comet impacting with the Earth, or a massive bout of super volcano eruptions! Either scenario would have caused mass destruction to our planet, creating devastating havoc such as choking ash clouds & debris filling the skies, greenhouse gases locking in the atmosphere causing the temperature to soar to unbelievable highs, and much much more! The world would have drastically changed for the worst, resulting in chaos for all that roamed the land! However, this disaster that's believed to have wiped out the dinosaurs remarkably didn't destroy everything! Most mammals, turtles, crocodiles, salamanders, and frogs somehow survived, as did birds, snails, bivalves, starfish, and sea urchins. Even hardy plants were able to escape death from the extreme climate changes!
Fortunately for us though the extinct creatures are not a lost memory of what once was, as the discovery of their fossilised remains, such as bone, teeth & eggshell, can tell us so much information about an incredibly important part of history & help piece together the start of our very own existence!!