From GameWatcher: “Frontier Developments celebrated its 25th anniversary in Jurassic World Evolution by issuing a challenge to the park management title’s community. Collectively, its members were tasked with releasing 25000 Stegosauruses into parks and it was recently revealed that they did, indeed,succeed.”
Source: N4G PC Jurassic World Evolution Update 1.6.2 Patch Notes – Vivid Variant Stegosaurus Unlocked