The recent fossil which was discovered in Japan was the Unique Mosasaur fossil last December 8, 2015. This was found 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. Dinosaurs surround the planet for about 165 million years. In the Earth’s history, this era is called the Mesozoic Era.