How many years after the Jurassic dinosaur Stegosaurus was officially extinct, did the Cretaceous dinosaur Tyr?
Lol, this is not an easy question to answer. It just got much harder, since the stratigraphic/temporal range of Stegosaurus was recently extended from the Jurassic to the early Cretaceous. This happened because the Chinese stegosaur Wuerhosaurus was “sunk” into Stegosaurus, on the basis of similarities. Unfortunately, there is anything but a clear idea as to when Stegosaurus became “officially” extinct, lol. (We didn’t even have a clear idea in the past because there is no fossilferous strata conformably overlying the Morrison to tell us if Stegosaurus really died out at the end of Morrison or latest Jurassic time.) To make matters worse, the exact age of the Lianmuqin formation, which yielded Wuerhosaurus/Stegosaurus, is not known with any degree of precision. At present one can only guess when Stegosaurus died out–although I assume this occurred at roughly the midpoint of early Cretaceous time c 135-125 Ma. Now as for when Tyrannosaurus appeared, that’s a little easier to figure out
