The visual bug occurs when using the so called "Skeleton" Polymorph.
The ingame description is:
This guise causes the user to take on the appearance of a living skeleton

Since I believe (based on ingame enemies and target dummies) to know how an argonian and/or khajiiti skeleton would look like.

i was rather confused when seeing my argonian beeing transformed into this:
Since i have the one from the Dark Brotherhood too i tried but weirdly enough this polymorph works as intended:
Probably just a bug which should be tackled next patch.

ty