The prevailing opinion among palaeontologists is that birds are direct descendants of theropod dinosaurs from the Jurassic period. The counter-view is that birds are actually descended from other prehistoric reptiles. If the dinosaur lineage theory is correct, then storks – and indeed all birds – could be classified as a dinosaur subgroup. But this is a bit like saying whales are ungulates (hoofed land animals), as they are ungulate descendants. Storks likely evolved long legs as a means of walking through tall grass and shallow water, searching for fish, frogs and other prey. Palaeontologists believe a flying dinosaur ancestor – the giraffe-sized pterosaur – may have hunted the same way.
Answered by Tom Harris.