In the interests of science, I must use this space to rectify some popular misunderstandings about Archen, which unfortunately have moved from monster movies about prehistoric life into popular consciousness by way of poor paleontological education.
Contrary to popular belief, Archen were not twenty feet tall. Although they were relatively smart pokemon for their era, and like their descendents can claim eyesight on par with humanity's, this does not translate to being able to open locked doors, even when given a key (nor, indeed, were they strong enough to batter down fortresses.) These pokemon are indeed flying type, but they could only "climb" stairs with their wings. And as the continued safety of every scientist involved in the various fossil research projects has proven, despite the imaginations of many writers and film producers fearful of unleashing monstrous extinct pokemon on the world, Archen pose no threat whatsoever to individual humans, let alone Man as a species. And this is equally true of their evolved form of Archeops, who show no more hostility to mankind than its many modern avian descendants.
The villainous role taken by Archen in fiction has little to do with any dangers these pokemon pose to modern ecosystems, and a great deal to do with human anxieties over reviving extinct pokemon. Archen were second after Omanyte among the resurrected fossil pokemon, and although it is a stretch to turn these birds into villains, an Omanyte would struggle to terrify anyone at any exaggerated size. These tales date from a very early era in pokemon paleontology, and incorporate misconceptions which have been debunked as well as dramatic license – for instance, Archen are indeed juveniles, but they evolve into Archeops instead of expanding dramatically in size – and should be treated as science fiction, not biological fact.