Up until this point over 700 dinosaur species have been found around the world and named but paleontologists believe that there are still many species of dinosaur to be discovered (although we will never be able to discover all of them since there are only a limited amount of bones from that period that are still intact). Dinosaurs can be separated into two main groups, Saurischians or the “lizard hipped dinosaurs” and the Ornithischians, the “bird hipped dinosaurs.” Ironically the birds are actually descendants of the Saurischians, specifically the Theropod subgroup, many at the time were bipedal meat eaters, the same as Tyrannosaurus and velociraptor. Some of the well know dinosaurs are: the pasauropod, the long necked plant eaters, the tyrannosaurus rex, and the pterodactyl.
When?
Dinosaurs first started appearing at around 201 million years ago In the Triassic period. At the end of the Triassic period, about 213 million years ago, there was a minor extinction that opened up many niches for the dinosaurs to expand into. Next came the Jurassic period which started at around 213 million years ago and ended at around 146 million years ago. Finally came the Cretaceous period which ended around 65 million years ago with a sharp decline in diversity on earth, a major extinction. This was accompanied by a temperature drop and a layer of clay. It is unknown how long it took for the dinosaurs to die out, it could have taken anywhere from a few years to a few thousand years.
How?
The most common theory is that the extinction was caused by a meteor impact, specifically one that struck the gulf of mexico, causing a crater that can be found there to this day. This would have caused shockwaves resulting in tidal waves, increased volcanic activity and earthquakes. It would have also caused a dust cloud that covered the earth, blocking out sunlight and causing the cooling. The lack of sunlight would stop plants from growing, causing the food shortages. However there are many other theories for why the extinction happened. One of these is volcanic activity, which would have similar dust cloud effects to the meteorite theory. This era was also a time of tectonic plate movement which supports this theory. Another theory is tidal changes, possibly due to the changing climate and the shifting plates, this theory would take much longer than the others.
Dinosaurs first started appearing at around 201 million years ago In the Triassic period. At the end of the Triassic period, about 213 million years ago, there was a minor extinction that opened up many niches for the dinosaurs to expand into. Next came the Jurassic period which started at around 213 million years ago and ended at around 146 million years ago. Finally came the Cretaceous period which ended around 65 million years ago with a sharp decline in diversity on earth, a major extinction. This was accompanied by a temperature drop and a layer of clay. It is unknown how long it took for the dinosaurs to die out, it could have taken anywhere from a few years to a few thousand years.
How?
The most common theory is that the extinction was caused by a meteor impact, specifically one that struck the gulf of mexico, causing a crater that can be found there to this day. This would have caused shockwaves resulting in tidal waves, increased volcanic activity and earthquakes. It would have also caused a dust cloud that covered the earth, blocking out sunlight and causing the cooling. The lack of sunlight would stop plants from growing, causing the food shortages. However there are many other theories for why the extinction happened. One of these is volcanic activity, which would have similar dust cloud effects to the meteorite theory. This era was also a time of tectonic plate movement which supports this theory. Another theory is tidal changes, possibly due to the changing climate and the shifting plates, this theory would take much longer than the others.