Pterosaur feathers

 https://biblio.ugent.be/publication/8752596/file/8752597.pdf (2022)

Remarkably well-preserved soft tissues in Mesozoic fossils have yielded substantial insights into the evolution of feathers(1). New evidence of branched feathers in pterosaurs suggests that feathers originated in the avemetatarsalian ancestor of pterosaurs and dinosaurs in the Early Triassic(2), but the homology of these pterosaur structures with feathers is controversial(3,4). Reports of pterosaur feathers with homogeneous ovoid melanosome geometries(2,5) suggest that they exhibited limited variation in colour, supporting hypotheses that early feathers functioned primarily in thermoregulation(6). Here we report the presence of diverse melanosome geometries in the skin and simple and branched feathers of a tapejarid pterosaur from the Early Cretaceous found in Brazil. The melanosomes form distinct populations in different feather types and the skin, a feature previously known only in theropod dinosaurs, including birds. These tissue-specific melanosome geometries in pterosaurs indicate that manipulation of feather colour-and thus functions of feathers in visual communication-has deep evolutionary origins. These features show that genetic regulation of melanosome chemistry and shape(7-9) was active early in feather evolution.  

Extended Data Table 1 is also very helpful showing stage IIIa feathers and morphotype 5 feathers in the tapejarid pterosaur Tupandactylus cf. imperator:

https://media.springernature.com/lw849/springer-static/esm/art%3A10.1038%2Fs41586-022-04622-3/MediaObjects/41586_2022_4622_Tab1_ESM.jpg

For reference:

http://prumlab.yale.edu/sites/default/files/prum_n_brush_2002.pdf

Developmental Model of the Origin and Diversification of Feathers 

A predicted transition series of feather follicles based on the hypothesized series of evolutionary novelties in feather developmental mechanisms (Figure 4) from Prum (1999). Stage I—Origin of an undifferentiated tubular collar yields the first feather, a hollow cylinder. Stage II—Origin of a collar with differentiated barb ridges results in a mature feather with a tuft of unbranched barbs and a basal calamus emerging from a superficial sheath. Stage IIIa—Origin of helical displacement of barb ridges and the new barb locus results in a pinnate feather with an indeterminate number of unbranched barbs fused to a central rachis. Stage IIIb—Origin of peripheral barbule plates within barb ridges yields a feather with numerous branched barbs attached to a basal calamus. Stages IIIaIIIb—Origin of a feather with both a rachis and barbs with barbules creates a bipinnate, open pennaceous structure.  

https://www.researchgate.net/publication/272171464_The_origin_and_early_evolution_of_feathers_insights_from_recent_paleontological_and_neontological_data
Xu and Guo

Morphotype 5 is only known in Epidexipteryx. It consists of parallel barbs arising from the edge of a membrane structure (Zhang et al., 2008b). 

Video from Maria McNamara:

 https://www.youtube.com/watch?v=Bmm3IyyjcS0

Difference between feather (with no barbules) and down:

https://www.youtube.com/watch?v=5rcwajqH0Dc&t=1s