1Heat oven to 350°F (325°F for dark or nonstick pan). Make and bake cake as directed on box for 13x9-inch pan. Cool 10 minutes; remove from pan to cooling rack. Cool completely, about 1 hour. Refrigerate or freeze cake 30 to 60 minutes or until firm.
2Cut cake as shown in diagram. Arrange pieces on tray to form dinosaur as shown in diagram. In small bowl, tint frosting with green food color. Attach pieces with small amount of frosting.
3Frost cake with thin layer of frosting to seal in crumbs. Refrigerate or freeze 30 to 60 minutes to set frosting. Spread remaining frosting evenly over cake. Let frosting set a few minutes. Carefully cover with paper towel and gently pat to give frosting a textured appearance; remove towel. Outline scales, legs, mouth, nose and eye with black gel. Decorate with green gel and jelly bean eye. Store loosely covered.