Step 1: Join spine halves with cross and add hips to complete the pelvis and spine.
Step 2: Add shoulders and front legs. Add rear legs to hips. Head and tail spikes can go on last if you wish.
Step 3: Before adding the plates, this is what the stegosaurus model will look like. Note the arrangement of plate slots on the ribs.
Step 4: Exploded view of ribs and plates. [Exploding dinosaurs. LOL!]
Step 5: This is what the Tinysaur stegosaurus looks like when fully assembled.