Greathouse takes readers back to the Really Old West for an outsized dustup between T.Rex, “the rip-roarin’est, snip-snortin’est reptilian that ever did stomp the earth,” and young Rocky, a dino tamer able to rope even Stegosaurus with his thousand-foot, crocodile-hide lariat since he was he was “knee-high to a Pterodactyl egg.” Schroades depicts the seesaw, continent-spanning contest in suitably big scenes featuring broad, rocky landscapes, plenty of brightly patterned dinos and a grinning, moon-faced lad topped by a notched Stetson. A map that stretches from the Mississippi River to the Pacific is dotted with red T.Rex tracks showing where the battle wended, with such landmarks as the Grand Canyon and Crater Lake (both created in the tussle) marked. By the end Rocky has his new cayuse munching on a zucchini and “docile as a fresh-hatched platypus pup,” ready to ride out into cowpoke legend. Yessiree, it’s the finest dino-meets-cowboy yarn since Betty G. Birney’s Tyrannosaurus Tex, illustrated by John O’Brien (1994). (Picture book. 6-8)