Tupuxuara’s very long fourth fingers

Tupuxuara belongs to the sub-order Pterodactyloidea, therefore you can call it a pterodactyl, which means wing (ptero) finger (dactylus). In this post I will describe the making of the four phalanges of Tupuxuara’s very long fourth finger.

Click to enlarge

The arm bones and fourth metacarpal are thick and have a quasi-cylindrical shaft, but the wing phalanges are very thin, have a flattened shaft and seem very fragile.

I experimented making a hollow shaft for the first phalanx with 2mm foam, but I felt it would be too fragile. I could fill it with scraps of melted foam which would give it strength (like in real bones) but I didn’t find a practical way to get the foam uniformly all the way through. So I abandoned the hollow bone technique for these four bones and decided to make them with strips of 5mm foam.

But the strips wouldn’t be enough. The solid bone is even more fragile. So I decided to reinforce them with plastic. I even considered making the small ones completely out of plastic (like I did Anhanguera’s teeth), but it’s easier to shape and fix mistakes on foam than on solid hard plastic. Starting with the fourth phalanx, I stretched a piece of round plastic hanger over a candle to reduce its diameter, and used it as a bone skeleton.

f4_reinforce

You can see how I do this on the posts on pterosaur teeth.

I used two parts 2mm thinner in diameter than the actual bone which you can see in the picture below. This bone is also a bit flat but I wasn’t able to make the plastic structure flat. It had to be compensated with the foam cover.

f4_reinf_2

I cut a strip of 5mm foam, made a slit inside it like this.

f4_slit

I tested fitting the plastic inside it, stretched the foam a bit, and made another one. These are the two phalanges #4 before assembly.

f4_both_assemble

I glued them together using hot glue, trimmed, sanded, finished with some fire. This is the result.

f4_foamed

It is still too thick (specially on the sides). I don’t know if I will be able to make it as flat as it should be. I might have to use a sanding machine since the plastic is very hard. Of course, it’s much heavier than it would be if hollow, but it won’t crack.

In phalanx #2 I added a flat piece of foam (also from a plastic hanger, but a of different kind). I used the candle to shape it according to the curvatures of the bone.

f3_reinforce

I repeated what I did with phalanx #4. Cut a slit and placed the plastic in the foam.

f3_assemble

After pasting, trimming, sanding and burning, here are the two last phalanges of Tupuxuara’s wings.

f3_foamed

Now phalanx #2. Same technique. There is more foam this time so I will have some space to shape the bone better (the shafts of phalanges #3 and #4 were practically exposing the plastic).

f2_assemble

Here are phalanges #2 after trimming, pressing, sanding and burning.

f2_foamed

And the wing so far, after the foam work.

f2_all_foamed

Phalanx #4 is the longest bone of the wing. It’s larger end (proximal) articulates with the wing metacarpal, which I haven’t made yet. This one could be hollow, but it would be too much trouble, so I decided continue using the same technique.

The plastic hanger I used has a structure with “H” shaped sections. I cut them in half lengthwise (making “T” shaped sections). I used that “T” strip as the bone skeleton for phalanx #4. The bone is practically straight (the curves are on the foam edges) so I didn’t have to curve the plastic. I sandwiched the plastic with two 5 mm thick foam strips.

f1_assemble

But the bone is not that flat. The proximal end has some bumps and prominences. They rise about 3mm on one side and some 7mm on the other I added an extra layer of 5mm foam on each side to carve them out, then I twisted the ends a bit to shape them according to the pictures.

Here is the final result. Four views of the four phalanges of the wing.

This is the view from behind (considering the position in the wing).

back

And this is the front view.

front

Dorsal (top) view.

dorsal

Ventral (bottom) view.

ventral

I might be wrong about which side is ventral or dorsal. I still don’t have all the information I need to assemble the pterosaur. If I am wrong, I will update this. Some bones are still too thick and the ends probably need some adjustments.

This is a view of the proximal end of the first phalanx (the end that connects to the wing metacarpal).

proximal_f1

And here are some pictures of the bone ends (proximal ends).

proximal_all

Now I can assemble the wings. I still need to finish the metacarpals, carpals, radio-ulna and humerus to connect this to the body. Here they are compared to a small keyboard (the keyboard is 35 cm long).

all_wing

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1 Comment

Filed under Pterosaur #5: Tupuxuara

One response to “Tupuxuara’s very long fourth fingers

  1. Pingback: Making of a Tupuxuara | The Imaginary Pterosaur

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