Spotting a passing dinosaur from his bedroom window one night, young Bobby follows it to a square surrounded by tall, dark office buildings where a host of dinos has gathered for a wild rumpus. Jobling, creative director of PBS’s “Bob the Builder,” creates big, blocky cartoons featuring simplified but recognizable dinosaurs, each a single, bright color, sporting with a pajama-clad lad until he drifts off and is tenderly borne back to bed. Emmett (Bringing Down the Moon, 2001, etc.) himself drifts between prose and verse in telling the tale, which makes for abrupt, awkward changes in rhythm. He cites Where the Wild Things Are as his inspiration, but when it comes to emotional or psychological depth, he misses the boat there too. (Picture book. 5-7)