adrosaurid aggressive animal animal themes animals hunting artwork attack beast biped carnivore concept conflict creation creature day dinosaur enemy evolution existence extinct fierce geology grazing hadrosaurid herbivore herd howling illustration imagination mammal medium group of animals megafauna mesozoic era monster mouth open no people origin ornithischia ornithopod outdoors parasaurolophus past predator prehistoric era prey primeval primitive reptile roaming roaring sauropod scavenger science species stalking survival terror theropod threat toughness tyrannosaurus rex vertebrate wilderness wildlife