Inspired by another Instructable, i was pretty sure i could do something similar but more in my price range. There was a pretty steep learning curve but i think it turned out great.

Materials needed:
toy dinosaur skeleton model
projector (I made mine and i'll show you how i did it)
cardboard
foam board
duct tape
paint stir sticks
framed back pack
yard stick
some nuts and bolts
drill
2 ping pong balls
hot glue gun
craft sticks
spray paint
LED "tea lights"
box knife
pencil

Step 1: Scale Up the Model

Once you've picked out your dinosaur model (found mine about to be tossed in the trash but I've seen them at craft stores or online), you'll need to make it bigger.

Put the disassembled pieces of dinosaur skeleton on a projector and project it onto a wall to the desired size. I wanted mine to be able to fit through a regular doorway so i started with the widest piece, a rib. I didn't have a projector so i used the LED light on my phone and built the cardboard contraption seen above. It barely held together and the projection was blurry but it DID allow me to scale all the pieces the same.

Trace the shapes onto cardboard or foam board using a pencil (sharpie bleeds through paint). I had stashed some cardboard back for this project but it had gotten pretty battered and i eventually had to trash it for crisp new cardboard. i got large packing boxes at lowes for $1.60 each. Foam board is even stronger but at $1 a sheet it was more than i was willing to spend for EVERY bone and chose to only use it for structural areas. But if you can afford it i recommend using it.

Areas that i recommend using foam board over cardboard: hip bones, thigh, and neck. Although there are plenty of places i used scrap foam to reinforce the cardboard.

cut them out with a box cutter. Mark the slits where the cardboard connects but dont cut them yet.

Step 2: Assemble the Costume

I started with the front of the dinosaur since it doesn't have any moving parts. It quickly became obvious where i would need extra support and duct taped some foam board to the cardboard (1). Because of the Z shape in the arms, the beat up cardboard i tried to use was too weak and i eventually had to make the arms from foam board (2).

Cut the connection slit for one piece, check alignment and cut the slit for the second piece and slide together. Use craft sticks and duct tape wherever a piece needs extra support

Step 3: Attaching It to the Frame

I started by cutting a large "slit" on the underside of the tail piece to fit over the bar of the backpack. I then built foam board stabilizers on each side. To keep it from sliding off i wrapped duct tape with strips of cardboard around the bar.

Now that i had something to attach the front to, i realized it needed extra support. I picked up a yard stick from Lowes for .69¢ and bolted it to the front spine so that it swings freely. This way i can use it as a sort of kick stand when I'm not wearing the costume, and holds up the front when I am. During a fitting, i later decided to extend this even more with another yard stick bolted to the end for another eight inches of length.

The two halves had a tendancy to pull apart and i solved this by sandwiching the front and back spine sections between two paint stir sticks, drilling a hole and bolting it together. The bolts can still come off so the two halfs can be separated for transport.

Step 4: Getting the Legs to Move

Pictured are the legs and hips of my toy model. To get the legs to move i omitted the lower bone and connected the thigh to the other upright bone with a bolt and locking nut (the kind with the rubber gasket inside). I also did this at the knee and ankle.

The lower legs of the costume are strapped to my leg with zip ties. I have to hold the knee up a little while it walks for a smooth movement but it works. It took several laps up and down my driveway to find a foot size that didnt feel like i was wearing flippers.

Step 5: Paint

Disassemble the costume and lay the pieces out for paint.

You can find a cheap can of spray paint for $1.50 but there wasnt much pigment and very little actual paint. Ace brand spray paint went MUCH further with more pigment and a better nozzle. Spend the extra $2. i used about five cans.

Dont forget to protect any exposed styrofoam because the spray paint will eat through it. I also covered the backpack with a trashbag to protect it from overspray.

Step 6: Reassemble and Glue

Get your hot glue gun ready, you'll need a lot of glue. I started with the ribs, glueing all four corners of the connected pieces. Then all the tail bones, leg cross sections, any part u dont want to come apart. I also glued the arms to all the ribs they touched since they seemed to snag on everything. I crushed all the fingers on one hand during a test run and had to reinforce them with popsicle sticks.

I left the skull and legs removable for easy transport. It only takes about two minutes to assemble and strap on the entire costume.

Step 7: Glowing Eyes

This part is optional and opinions varied at my house. Some felt the costume didnt need them but i liked the added touch. Buy some cheap LED tea lights and some ping pong balls. Cut a small hole in a ping pong ball and push it on top of the "flame" of the tea light. For the pupil i just stuck a black sticker on it. Hot glue the side of the tea light (so you can still reach the power switch) and glue to the inside of the skull so only the ping pong ball shows.

Step 8: Wear It!

grab some black clothes and maybe a black mask (I used black facepaint from last year) and wear your costume out. You may need a handler (someone to keep you from bumping into things) if you're going to be in tight spaces.

After wearing the costume two nights i wish i'd made the legs a little sturdier but the whole costume held together and i got great reactions to it!