When did dinosaurs first appear?
The dinosaurs didn't suddenly "appear" on the earth. Animals evolved over millions of years to the point where they took the forms we are familiar with now as dinosaurs. The fossil record is clear in this. Smaller, less sophisticated creatures gave way to larger and more complex critters. Some 230 million years ago is the general time that paleontologists consider the dinosaur first appeared. Things rolled along until about 65 million years ago when the lights went out for the dinosaurs.
A link to the Wikipedia article on the dinosaur is provided.
Sharks appeared long before the dinosaurs. Their oldest fossils date back to somewhere between 450 and 420 million years ago, before there were land animals and when few plants had even colonized land. The first dinosaurs didn't appear until 230 million years ago. The sharks also outlasted the non-avian dinosaurs during the K-T extinction 65.5 million years ago, and they will probably continue to swim in the oceans for hundreds of millions of years to…
Fossilised remains of "turtles" have been found dating back to the Cretaceous period in Earth's history (this period ended around 65 million years ago).... However Dinosaurs have been on the planet for a MUCH greater length of time, it is debated slightly when the first dinosaurs appear but it is alleged to be over 200 million years ago. Therefore dinosaurs would have become before turtles
Life started out with very simple organisms, and dinosaurs were very complex, so naturally they came long after the first life. Here's a way to appreciate the timing: If the whole existence of the Earth so far were represented as a single year, beginning January 1st, some life would be present before spring, but dinosaurs wouldn't appear until Christmas.