The pectoral girdle consists of scapula, coracoid, sternum, dorsal vertebrae and ribs that grow from the vertebrae and from the sternum. I’m still having trouble figuring out how to assemble the scapula and coracoid. I read some articles and I haven’t discovered yet what most paleontologists think is the best layout. They seem to disagree in many aspects. Without twisting the bones quite a bit or setting the scapula to articulate with the first two dorsals I can’t obtain a low position. At best, the glenoid will stay somewhere in the middle of the chest. For now, I just pinned the proximal end of the scapula to the third dorsa, and the distal end of the coracoid to the sternum, so I could work on the rest of the pectoral girdle. But the correct way to connect scapula and coracoid is still an issue I haven’t resolved. Any help is welcome.
The ribs. I found some random ribs in fossils, but I preferred to use Wellnhofer’s reconstruction of Pteranodon as a reference to start with. I scaled them for Tapejara and made these sketches.
I cut out the two first pairs.
I made them hollow of course. This is a first prototype attached to the first dorsal vertebra.
I quickly made some (generic) sternal ribs and connected their ends to the sternum and larger ribs to test the shape of the rib cage.
Time to make more ribs.
The sternal ribs are thin but they have some lateral very thin bone pieces projecting laterally. It looks like some kind of ossified cartilage. How many ribs should be connected to the sternum? Some say seven lateral pairs, many reconstructions show four or five. The azhdarchoid MN-6588-V seems to have seven, and probably two more pairs behind. I chose five.
Now the challenging attempt to assemble the pectoral girdle.
Somehow I fitted the scapula and coracoid in a way that revealed a glenoid and didn’t seem weird. The proximal end of the scapula is pinned to the third dorsal vertebra. If I project it a bit more laterally, it can move back more, but the sternum-coracoid articulation will also change.
So now it looks like this.