Cari Meister, , illus. by Valeria Petrone. . Viking, $15.99 (32pp) ISBN 978-0-670-03555-7

"Nobody messes with a dinosaur," crows this wishful and humorous bodyguard fantasy in which a lime-green triceratops vanquishes a bully. Luther, a dinosaur disguised as a pirate, acts frightened of his human pal's werewolf costume. But when a bratty kid steals trick-or-treat bags, Luther reveals his true identity and reclaims the booty. Meister (Busy, Busy City Street ) implies that Luther isn't aggressive, just fair-minded. Petrone (Plumply, Dumply Pumpkin ) layers cool blues and lavenders over a terracotta base, and her palette takes the edge off the frightening scenes. Her big brushstrokes show Luther's formidable size and gently rounded features. This reptilian do-gooder would be welcome on any playground. Ages 3-up. (Aug.)