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.
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.
This is what it looks like when you are underneath a pterosaur skeleton.
It saw us and it’s coming this way!
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!