The tag alias #71224 membranous_mane -> membranous_frill is pending approval.

Reason: A membranous frill is like a mane except it is membranous and it is called a frill instead of a mane. I suggest an alias for discoverability.

To be honest, I usually just tag a combination of head_frill, dorsal_frill, tail_frill for a mane like that.
Membranous_frill does not describe the location of the frill, only the material it is made of.