Many small mammals have scaly skin on their tails and sometimes limbs. The examples can be found among rodents (rats, degu, scaly-tailed squirrels), insectivores (shrews, desmans), oppossums, musky rat kangaroo. There are much more prominent examples like pangolin scales but I would like to concentrate on as simple things as possible.
I would like to know the answers or at least what is known on the following quiestions.
- Are scales of these different mammals actually something similar or is it just an illusion?
- Does the scaly pattern at least in some cases represent some primitive characteristic of a common mammalian ancestor?
- In case of positive answer on the previous question is there any connection to the scales of the diapsid reptiles? As I understand the latter are built from $\beta$-keratin absent in mammals but perhaps there are still similarities or even a common origin.
For now my search on this topic resulted in some contradictory claims without any solid references. I would update in case I find anything that seems relevant.