Ashlands tierMaterial
Bonemaw Scale
It looks just like bone. Best not to question the anatomy of this creature too much...
The Bonemaw Scale is in the game files, but nothing drops it. A 
Bonemaw yields 
Bonemaw Teeth, 
Bonemaw Meat and sometimes its trophy, never scales.
Spawn command
With devcommands enabled, this drops Bonemaw Scale at your feet. The ID is case sensitive; the last number is the amount.
Item ID: BonemawSerpentScale · see the spawn command or all console commands and IDs