Based on the recently found fossil, we can find them on the Mesozoic Era. Dinosaurs surround the planet for about 165 million years. In the Earth’s
history, this era is called the Mesozoic Era.
----->The recent fossil which was discovered in Japan was the Unique
Mosasaur fossil last December 8, 2015, not long after the discovery of
the Dinosaur relatives and first dinosaurs (Dec. 7, 2015) by the University of
Utah.
Most possibly, these creatures existed during the Mesozoic
Era.