A dinosaur is any species of reptile that is now extinct that existed during the Mesozoic Era, mainly in the Triassic period. They often reached very large sizes and were both carnivorous and herbivorous. The date range of their existence is approximately 160 to 230 million years ago. Generally speaking, the term has loosely been applied to ancient birds, fish, and various invertebrates that lived during that period. The word, “dinosaur,” was first coined by Dr. Richard Owen (M.D.) in approximately 1841.