Here is a first draft list of changes that would have taken place from
Rhamphorhynchidae (pterosaur) to Scansoriopterygidae (basal paraves):
First finger lost
Large 4th finger reduced
Finger distal phalanges lost
Patagium greatly reduced
Pycnofibres developed into wing flight feathers
Uropatagium replaced with flight feathers
Distal syncarpal becomes semilunate carpal and fuses to metacarpals
The pteroid bone and lateral carpal are lost
Acetabulum is not completely closed
Second toe becomes hyper-extended
5th toe is lost?
Clavicles no longer incorporated into the sternum
Humerus saddle-shaped head becomes bulbous
External mandibular fenestra appeared
Posterior teeth reduced
First toe is turned backwards?
If anyone would care to suggest a change or addition, please do. Just provide reference link(s) and copy and paste the material that you think supports your suggestion.
The discovery of Yi qi would change the transition steps*.
The major changes would be:
The large 4th finger is first reduced to just the metacarpal (Yi) and then that is also lost (in other scansoriopteryids).
The remaining digits would be digits 1, 2 and 3. (The first digit would not be lost, the 4th digit would be lost).
* if the interpretation of the Yi characteristics by Xu et al is correct.