Prehistoric Animals Break into US Parks: Book 4: Dimetrodon in The Dakota Prairie Grasslands

The call coming from the Dakota Grasslands summons the watchers when sail-back reptiles are noticed there. While doing their usual routine in this mission, they are unexpectedly attacked by those sail-back reptiles and some other animals. With these various attacks in different places, the team starts to suspect and wonder if an unknown foe is behind this. They end up in a showdown and discover who the villain really is. How will they be able to foil the plot of this new enemy?