Tag Archives: pubis

Tapejara: pelvic girdle

I already had made the pelvic bones, but the sternum complex was missing. I didn’t find any realiable source with a perfect sternum, so I used as a source the same azhdarchoid sternum that I used in Tupuxuara, and adjusted it so it would fit the Tapejara pelvis (from SMNK PAL 1137). They are 5 sacral vertebrae, and two dorsal ones with lateral processes fused to the preacetabular processes of the ilium.

I cut it out in one piece from a sheet of 2mm foam, and added the stacked vertebral bodies sculpted out of thicker (yellow) foam. Here are two views of the sacrum after treating with fire.

sacrum 2 sacrum 1

Four views of the finished sacrum.

lateral ventral posterior anterior

Next step: assemble the pectoral girdle. I now have all the parts.


I wish I had smaller pins.

testing dorsal dorsal w pelvis testing lateral anterior with pelvis posterior with pelvis

I placed a rubber tube through the vertebrae acting as a spinal cord. It will be used to attach the pelvic girdle to the dorsal spine and to attach the tail on the other side.

ventral w pelvis

I now can test all the connections. Here is the Tapejara dressed in its pelvic girdle.pelvis and sacrum

A dorsal view.

dorsal assembly

And a ventral one. It’s almost finished. I’m already prototyping the pre-pubis and gastralia, but before I assemble the rest I will cover what I have so far with epoxi resin (I can’t use pins anymore).

ventral assembly lateral assembly

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Tapejara pelvis and legs

I’m still don’t have all the information for the pelvis, but I decided to start doing it anyway. My only source are the images of SMNK PAL 1137 from the article by Eck et al, which are in black and white, low resolution and have at most two views of each bone. I will have to use what I know about other pterosaurs to make it three-dimensional.

I started cutting out the parts in scale (the scale is another big problem – I based my choice on information from paleontologists since the scales in the article are not reliable).

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Then I  folded and tried to shape each bone trying to guess the depth of its three-dimensionality from the shadows. I also used as references all I learned about pterosaur pelves so far, but I never made one from the individual bones before.

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This is a prototype. The pelvic bones are actually a set of four bones on each side forming the pterosaur’s hips. It’s supposed to look something like this. The long one on the left is the ilium (the long part of the ilium is actually called the preacetabular process). On the right, above is the postacetabular process. The depression near the right side of the ilium, which forms a circular shape if you consider the other two bones below is the acetabulum. That’s where the femur will articulate. At the lower left is the pubis and at lower right, the ischium. The point where the ilium, pubis and ischium fuse together is the acetabulum.

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Here I added some more detail, did some fire shaping and coffee-staining. It’s still a prototype for testing (I might change it or throw it away after I use it). You can see better now the three-dimensional aspect of the ilium, showing the acetabular depression, and the medial side of the postacetabular process.

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The process I used to make the femora and tibiae is the same I used for the other long bones (humeri, ulnae, etc) so I won’t detail them here. This is a picture of the strips of foam I used to make the bones of the legs. One of the femora is already with its halves glued in place.

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The tibia is actually a set of four bones called the tibiotarsus. It contains the tibia itself, the fibula (a very thin bone fused to one of the sides of the tibia, starting at the proximal end and not reaching the distal end), the calcaneum and astragalus which are actually part of the feet (they are the proximal tarsi which function as hinges for the feet). The picture below shows the tibia-fibula and the calcaneum-astragalus parts.

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Now we can try assembling the whole set, so see how it looks. In the upper part of the image below is an unassembled pelvis, a femur and a tibiotarsus, and at the bottom an assembled pelvis with an articulated femur and tibiotarsus.

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Here I tried to fit them in place with my fingers.

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But it’s easier with pins. The image below shows a tibiotarsus, femur, and an assembled pelvis.

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There is still a lot of work to do on the pelvis, and I should return to it next week when I will try to connect them to the sacrum, and finish the pelvic girdle.

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Tupuxuara: the pelvis, sacrum and dorsal vertebrae

The specimen I have been using as a source (IMNH 1052, Iwaki Museum, Tokyo) has no pelvis, sacrum or any other dorsal vertebrae. I already made all the bones from that source. The sources I used for this pelvis were kindly sent to me by Mark Witton, and belong to a related species (possibly a Tupuxuara).

My sources were four views and a diagram from where I calculated the size of the pelvis relative to the other bones. The right view was the best, so I used it to sketch the pelvis bones. I sketched the sacrum from the dorsal view. There was also a posterior view, which I used later.


I cut the parts slightly larger so they could be molded.


First, I assembled the sacrum gluing the two halves together (by the spinal crest).


Then some trimming, and let it dry.


I was in a hurry to see what the pterosaur would look like with a pelvis, so I pinned the parts together and let the sacrum dry hanging on its “spinal chord”.


Then I added some foam to the other side, to shape the sacrum, and compared it to a diagram I made from the sources.


While that was drying, I worked on the sacral and dorsal vertebrae, carving a spine from thick foam. Here I lined up the sixth thoracic vertebra (the last one from the notarium), three free lumbar (dorsal) vertebrae, and seven fused vertebrae.



I tested it before attaching the parts.


I had no source for the three lumbar vertebrae, so I invented them based on the others.


Here are the vertebrae lined up.


And here is the first one that articulates with the pelvis in place.


As a spinal chord I am using plastic tubes of different widths. I insert the thin ones into the wide ones. There is a spinal chord for the cervicals, for the notarium and for the pelvis. The tail vertebra will be mounted on a thin rigid plastic spinal chord, which will be inserted in the thinner tube (the white one in the picture below).


Time to attach the pelvis. First one side.


Then the other. I always twist and fold the foam before attaching.


Some parts need more work. Here I am trying to shape the pubis while keeping the ischium in place.


The two halves are not enough to provide all the three-dimensional details I need for the pelvis, so I made some “masks” with 5 mm foam which will allow some shaping.


I also added some foam at the sides of the ilium to shape a small iliac crest (extending from each side of the sacrum). From the pictures I don’t know the exact shape of the ilium (I have no frontal view, and it’s partially damaged), so I looked at some other pterosaurs and chose something which matched the picture. This is the pelvis seen from the inside after most of the foam shaping.


Another view.


And here’s a dorsal view.


Now the resin coating, coffee staining, and we’re done. Here are three views of the pelvis. This is the left side.


This is a dorsal view.


And this is a ventral view.


The pelvis is a complex set of bones. I don’t know if I achieved in making an accurate one. I did my best with only three views. I’m not really sure if I should have closed the ischium. If I get more data in the future I will fix any mistakes.

Here you can see it in other angles.






Now finally I can attach the legs. Here are two pictures of the pelvis in place with the femora attached.


from behind

This is what it looks like when you are underneath a pterosaur skeleton.


It saw us and it’s coming this way!

almost done

What’s next? I don’t know. As you can see from the pictures above, some bones are connected with rubber bands: I still didn’t make any carpals. I will have to invent carpals, fingers, toes, and tails. I have none of them. They are small and simple bones, so there is a good chance that I might finish this skeleton tomorrow.

I already have some sources but I am still interested in any new ones. If I have more information I will be able to make a more accurate model. I am interested in pictures or drawings of feet, tails or hands of a Tupuxuara, Thalassodromidae, or even a related species. If you have any, send me an email!

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