Step 15: Use the line on the far left side as a guide to draw the second front leg the same way. Lightly sketch the shape of the leg around the guide line. When you get the trunk-like shape right, darken the lines. At the bottom draw the Diplodocus's toes using short lines and give the inner toe a long claw. The top part of the leg will be hidden behind the body, so don't worry about drawing it.
Step 16: Use the long, angled, vertical line on the left as a guide to draw the first hind leg. Lightly sketch the shape of the leg around the guide and only darken the lines when you get the shape right. The shape of the hind leg should be a lot thicker at the top than the front leg. It should also be slightly longer. Bend the shape near the middle and add some short lines to emphasize the joint. Draw some curved lines at the top for the loose skin and the toes at the bottom using short, sloping lines. The toes on the Diplodocus's hind legs don't have the extra long claw, so don't draw it here.
Step 17: Use the line on the far right side as a guide to draw the dinosaur's second hind leg. Draw the shape of the leg around the guide. The top part will be behind the body, so don't draw it. Use short lines to draw the toes at the bottom and the folds of skin at the joints.
Step 18: Use the long line on the left as a guide to draw the neck. Just like with the legs, draw the shape of the neck around the initial guide line. Continue drawing the line next to the jaw toward the right to create the bottom part of the neck. Draw a few curved lines next to the dinosaur's body for the folds of loose skin. Draw the top part of the neck the same way. The neck should be thin near the head and gradually get thicker toward the body. Always sketch lightly at first so that it's easy to erase if you make a mistake. Add a bit of loose skin under the Diplodocus's head using a curved line.
Step 19: Continue drawing the line for the top of the neck across the initial shapes in the middle to create the Diplodocus's body. Continue drawing this line horizontally on the right side instead of dipping it down along the initial guides. Darken the lower edge of the guides in the middle to create the bottom of the body. Don't overlap the shapes of the legs.