Tag Archives: phalanx

Tapejara’s hands and feet

It was challenging to make such small bones. The metacarpals were the thinnest ones and the phalanges of the feet the smallest. I obviously didn’t make them hollow since they are thinner than my 2mm thick sheet of foam, but I did try to. I made hollow fingers, but later reduced their width by pressing and by using fire. That made them stronger (although the result was a bit thicker than I expected). Since they are small and very fragile, I can’t pin them together (I would need some micropins for that), so I already covered them with epoxi resin. Here are the pictures.

This is a metatarsi from one of the feet, before treating with fire and resin.

Metatarsal

Here I try to fit the bones in place to make adjustments. The images from SMNK PAL 1137 are very bad but I used it to get the proportions of the metatarsi and the first toe phalanx and toenail. I initially then used as sources individual photos of Tapejara foot bones, but they are usually in unprepared blocks and not always entirely visible, and sometimes damaged. So my measurements didn’t match. I also looked at several well-preserved photos of different species (like SMNK PAL 3830) but then adapted a generic layout from Wellnhofer’s handbook for Pteranodon, scaled for Tapejara. It seems that the smalled phalanges are a bit smaller in Tapejara, and I tried to make them a bit smaller. Here are the bones of the feet after attempting an assembly.

assembly

And these are the hand fingers (I made the phalanges hollow).

finger assembly

I pinned the fingers to the wing metacarpal to try it out.

hand testing 2

hand testing

Then I pinned all these little bones on a surface to apply the epoxi resin.

resin 4

I feel like leaving it this way ūüôā A Tapejara bone graveyard under an unknown Azhdarchoid skull.

resin 6

Here are all the shiny parts after the resin dried.

shiny

These are the toe bones. Each square measures 5mm (remember this Tapejara was scaled up 25%).

toe set

And the bones in place (I will make more adjustments when I connect the bones together with silicone rubber).

toe assembly

Get these rocks and assemble a pair of hands?

finger set 2

finger and metacarpal 2

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Tapejara wings

The wing is a giant finger, and fingers are connected to the radio/ulna pair by several small bones called carpals and metacarpals. I’ll leave the carpals for another opportunity and concentrate on the metacarpal and four phalanges of the wing.

The wing metacarpal is a big bone, about the size of the radius and ulna and even wider on one end. The wider end articulates with the radio-ulna pair through the carpal bones, and the other is a hinge for the first phalange of the wing – the longest bone in the Tapejara body.

I used SMNK PAL 1137 as a source, but had to rely on Tupuxuara for some details. They are similar. I got the length dimensions from Brian Andres’s database (scaled 25%). I used the same process I employed on the other long bones. Cut two halves, shape, glue together, fix with fire, add ends in thicker foam and reshape.

IMG_5371 IMG_5376 IMG_5381 2013-07-24 18.00.09

After the metacarpal comes the long first phalanx. This one I could rely on a picture I have from IMCF 1061 (which was perfect, since the quality of the pictures in SMNK PAL 1137 is very bad).

This bone has a flattened shaft, so it has greater resistance to anteroposterior forces than to dorsoventral ones.

IMG_5350

You can see I added a thin strip of plastic to the middle of the bone. Does that increase resistance?¬†I measured it. A strip of 2mm foam 20 cm long ¬†and 7mm wide attached on one end (1cm for attachment) can support 7 grams on the other end before folding (forcing the weak narrower side). Treating it with fire made it resist more, but it cracked with 9 grams. The phalanx has two of these strips, and is a bit hollow (I glue them on the edges, slightly curved). I made a prototype which supported 20 grams before cracking. Adding the strip won’t keep it from bending, but will avoid a destructive bend in one place or cracking. I expect that resistance to increase when I add the acrylic resin, and even more after the epoxy resin coating. Anyway, the maximum of weight the phalange will have to bear (considering only support on the proximal end) is 7 grams (considering the other three phalanges already coated with resin and epoxy and connected with silicone rubber). They currently weigh less than 5 grams (no epoxy coating yet) and they still have some water from the acrylic resin to evaporate.

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Here are the finished bones of the first phalanx compared to an unfinished humerus and the neurocranium.

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Some closeups and other angles.

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Testing the articulation with the metacarpal.

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The articulation with the radius-ulna pair is still not possible because there are yet no carpals.

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Next step: the other three phalanges. In fact I already had them all cut out and the haves attached before I did metacarpals and radius-ulna pairs. All these unfinished bones fit nicely on top my computer.

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So I tested the wings before I made these bones.

IMG_5396

And here is the final result. I used IMCF 1061 as sources for phalanges 2 and 3, and Tupuxuara for the last phalanx. I also used measurements from Brian Andres (scaled 25% as usual, since this is a larger specimen).

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Here is a detail of the last phalanx and articulation.

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And the full wing (I still hadn’t finished the humerus).

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Now we can place the bones on a surface and imagine the full skeleton.

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Pterosaur claws

I have several photos of individual finger bones from yet undescribed species which might be Tupuxuara. I also have pictures of the fingers of Tapejara wellnhoferi. But I only have photos of the bones of Tapejara from one angle, in black and white and in low resolution, so I can’t really see if they are flattened out, or curved in some direction. I assume they are straight comparing to the other photos I have (unfortunately I can’t post any of those pictures here, since they are all unpublished research). I compared different drawings of pterosaur hands and they seem quite similar. The number of phalanges is the same in all pterosaurs. Including the nails, the pattern for fingers 1-4 (where 4 is the wing)¬†is 2-3-4-4. The sizes, the widths and the shape (curved, straight, flattened) of the phalanges differ across different species. As to the proportions, I found no great differences between some drawings of Tupuxuara hands (from which I have no sources), Tapejara and Pteranodon. So I used¬†this drawing by Wellnhofer, scaled it to mach the size of my Tupuxuara skeleton, and used it as a guide to carve the fingers.

Here are the fingers and metacarpals after carving.

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These are the finger bones and nails before assembly. I already pinned the metacarpals together.

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I have to turn the metacarpals a bit, but this is how the fingers will be assembled.

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Here are Tupuxuara’s claws after assembly. I am using pins to test, but I will later keep the fingers and metacarpals together using some cartilage (silicone rubber). If I use pins all the time it will weaken the foam.

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Now I placed the metacarpals back on the skeleton with the claws in place.

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Here are some other angles showing the left hand.

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This is the right hand.

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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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Tupuxuara: planning the wings

Tupuxuara’s wingspan is about 4.5 metres wide. The wing connects to the scapulocoracoid through the humerus, which is the arm bone. Then come the radio-ulna pair (forearm), carpal bones (wrist), metacarpals (hand) and fingers. There is one large finger which is the wing. It’s metacarpal and phalanges are more than two thirds of the length of the wing.

This is a diagram of the right wing showing the sources that I have (Iwaki museum) in brown. The parts that are missing are shown in white. I will have to invent them. Click to see a larger image.

DCF 1.0

Most of my sources are four photographs of each bone, showing four sides. I have no photos of the bones viewed from the tips. I will have to do my best to discover their shape from the pictures I have. I will certainly miss details (concavities, for example) unless I can infer them from shadows.

I will start with the humerus but will make all the bones at the same time (it’s faster that way and I can let the glue dry better before carving and shaping).

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