Thesaurus Has a Secret by Anya Glazer
From Katherine Tegen Books:
A Kids' Indie Next List pick! From author-illustrator Anya Glazer comes a humorous picture book for dinosaur fans and word lovers of all ages.
Thesaurus is an ordinary dinosaur. A very ordinary dinosaur . . . who just happens to love words. And the other dinos know that’s just who he is. But behind his verbose and fancy language, Thesaurus has also been keeping something absolutely, very, extremely top secret.
But as his lies begin to stack up, someone begins to notice. And if the other dinos discover what Thesaurus is hiding, they won’t think he’s such a normal dinosaur after all.