Complex sentence: The earliest dinosaur "Eoraptor" originated slightly before the Carnian stage began around 230 Ma, nevertheless, the oldest well documented dinosaurian assemblage, in the Ischigualasto Formation of Argentina, is most probably late Carnian in age.
Split into simpler sentences: The earliest dinosaur "Eoraptor" originated slightly before the Carnian stage began around 230 Ma. The oldest well documented dinosaurian assemblage, in the Ischigualasto Formation of Argentina, is most probably late Carnian in age.