Tag Archives: radii

Tapejara arm bones: humeri, radii & ulnae

I should have finished the head and the spine by now, but I am waiting to get better sources and images, so I decided to change my schedule and work on the long bones. This post is about the arm bones: the humerus and the radius-ulna pair.

I am using as sources the images from SMNK PAL 1137 (which unfortunately are in low resolution and black and white). For the humerus I also had four colour views from IMCF 1061. I am using the dimensions which the paleontologist Brian Andres sent me, which I increased by 25% (since this Tapejara has a 2m wingspan).

I made each bone from two halves of 2mm foam sheets. Since the shafts of the humerus, radius and ulna have a round section (in contrast to the wing bones which are somewhat flat), I drew the parts about 30% wider in that part, and left a bit extra at the ends to allow cutting and reshaping.


After cutting, I shaped the foam and glued the two halves in place.


This is a view of one of the ends.


After I did that with both humeri, I reshaped and lightly applied some fire to trim the edges.


Herre are the two humeri compared to a humerus from Tupuxuara leonardii.


In the picture above, I just filled in the bone ends with thicker foam, which allows some sculpting. After drying I then gave it some more treatment with fire.


This is the final result so far. I will further improve this after adding resin and coffee stains.


This is the humerus after resin and stains. it still needs some sanding and trimming.

2013-07-25 22.28.07

I based the ulnae and radii on SMNK PAL 1137. It seems they are the same size (if the scale is correct) and that they are almost the same width (some pterosaurs have a much narrower radius). I didn’t curve the radius like the picture. Here is a pair of ulnae before assembly.


And this is after gluing the halves together and trimming with fire. I still have to make the bone ends.


After adding the bone ends, and some trimming, I could finally try to fit them together.

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Here are some views of the finished arm bones: humeri, ulnae and radii:

2013-07-27 11.33.17 2013-07-27 11.38.06 2013-07-27 11.40.39 2013-07-27 11.42.10 2013-07-27 11.43.22

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Tupuxuara’s wing: the humerus, radius and ulna (final)

It took a couple of days to finish these bones since I had to carve many details and because the foam glue, when applied over a large surface, takes very long to dry (it’s risky to carve while it’s not completely dry). Now we only need the carpals to be able to assemble the wings.

DCF 1.0

I have no source photos of the bone ends, and it wasn’t very easy to discover their shape by just looking at the other photos. The humerus has a very complex end. I made some sketches, looked at pictures of humeri of other pterosaur species, and experimented a bit before attaching the ends. It was easy to close the shaft and the distal end of the humerus.



But it was challenging to sculpt the proximal end. After some trial and error, I had something like this to start working.


But then I still removed and added foam until I finally had a shape that matched the side views. After I finished one bone I used it as a reference, so the second humerus I made much faster.


Here are some pictures of the result showing four sides of the humerus. The pencil is 16 cm long. Both are approximately the same side. The angle the photo was taken may make one seem larger than the other in some views.





This is the distal end (the end that connects to the radio-ulna pair). It’s speculative (I invented it using the side views as a source).


And this is the proximal end, which connects to the shoulder (scapulacoracoid). It is also speculative. I might make adjustments later when connecting the bones.


Now the radio-ulna pair. I wasn’t able to trim the radio bone’s shaft to its correct width. The technique I used (see last post) was not a good one. So I tore the shafts apart, preserved the bone ends, and made new shafts by rolling thin (2 mm) foam. Here they are attached to the bone ends.


And now some photos of the final results. The bones are not yet connected. I just pinned them together for the photos.





These are the sides that fit together.


The proximal and distal views are speculative since I don’t have any photos of them. They were derived from the side views. This is the proximal end (which connects to the humerus).


And this is the distal end. (I’m not 100% sure that I am right. It may be the other way around. I’ll have to check that before assembly.)


Now we can assemble the wings. I still can’t connect the bones because the carpals (between the wing metacarpal and the radio-ulna pair) are still missing.


Here is a picture of Tupuxuara so far. I’m now working on the carpals, pelvis and leg bones.


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Tupuxuara’s wing: the humerus, radius and ulna, part 1

I started the humerus and the ulna-radio pair for each wing (click to see a larger image).

DCF 1.0

I made them hollow, using different techniques.

I printed the four views of the humerus and used them as guides to cut out four parts.


I should have cut them some 20% thinner along the middle (diaphysis), since it has a cylindrical shape. But I did not, so I couldn’t use all four strips of foam. The humerus has a prominent crest on one side so I chose the two pieces which contained it and attached their edges to the piece cut from the “rear” view. I also cut some round strips of foam to use as a guide when shaping the bone.


I glued the three sides together and let them dry. Then I squished, folded, pressed the foam to shape.


It takes some time to dry, and if you start squishing and cutting, the parts may detach. They did! I used rubber bands to keep everything in place and let it dry and started working on the ulna.


Since the bone ends (epyphisis) have an irregular format, I added a thick piece of foam there so I can carve the details out later. I still didn’t add one of those to the other side, near the crest, since I don’t have yet a clear picture of what it should look like.


While the humeri were drying I came up with another idea for the hollow long bones. Why not just roll them? There are some difficulties. The long cylindrical part of the bone (diaphysis) may change shape. It’s section may be round and wide on one end, and flat and narrow on the other (the wing metacarpal is like that). The bone may also be slightly curved. But gradual changes in section width and shape, and bending can be done very easily while gluing the cylinder. I decided to give it a try.


I cut out the whole bone from one piece of foam. Tried to squish it and curl it, but it cracked in several parts and I had to throw it away. I tried it again. This time I squished the foam well before cutting it out and it worked. I was able to curl it all the way.


You have to do all the folding before cutting the foam. It is still not that easy and if it cracks you have to start again since cracks will make it very hard to shape the bone later. When both sides were attached with glue and kept in place with rubber bands and tape, I rolled it a bit more near the centre (the glue was still not completely dry), making it narrower. I also gave it a slight bend. The result compared well with the photos. I can still improve it later in necessary and add any details, since the foam is 5mm thick and can be carved.


Now I have two humeri and two ulnae drying. Time to make the radii.


The radius is not much smaller than the ulna. It’s much flatter so I decided to not use the cylindrical technique to make it. I made a box like the picture below.


Later I will shape it by carving the edges. I used thick foam for the bone edges so they can be carved into shape later.


I also added the bone ends to the ulnae. So here is the result so far: two humeri, two ulnae and two radii.


I still don’t know how to make the other bones. I will try other techniques and maybe I will come up with an optimal one. It would be great if I could buy foam cylinders in different diameters, or if there was some kind of foam tape :).

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