Personalized Dinosaur 3rd Birthday Long Sleeve T-Shirt. A dinosaur apatosaurus (or brontosaurus to the grandparents) stands tall over the 3 for the second birthday. Happy third birthday to the three year old! Pre-shrunk 100% cotton 6.1 ounce long sleeve t-shirt. Double-needle stitched neckline and sleeves. Quarter turned. Shoulder-to-shoulder taping. Adult: S, M, L, XL, 2XL, 3XL