From Epidexipteryx membrane to follicle collar

 Very interesting:

https://scienceblogs.com/tetrapodzoology/2008/10/23/epidexipteryx-at-last

Also worth noting is that the pennaceous feathers of birds begin growth as a tubular structure: from a broad 'follicle collar' that extends around the base, the rachis extends upwards, the barbs emerging both from it and from the edges of the collar. Might the membranous bases of the 'non-ETFs' of Epidexipteryx be homologous with the follicle collar? This is all very speculative, but these are interesting questions that need to be examined.

Indeed, the feather follicle originated even further back, in pterosaurs as pycnofibers.