art by ticklemecthulhu
In my world of arthropod-like creatures (in that most of the creatures have an exoskeleton rather than an endoskeleton), I wished for a group of my aliens to convergely evolve into pterosaur-like creatures, resulting in a previous question about this, though then I was more focused on whether it was possible.
Overall, the goal is for an animal with a roughly pterosaur-like appearance, including wings made of a limb with an elongated finger-like extension and a flexible living membrane made of muscle, blood vessels and support fibers which allow for changes in the membranous surface. The creature has bird-like circulatory and respiratory systems. The image above somewhat illustrates what I originally thought would be necessary: the presence of a "groove" alongside exoskeleton plates allowing for the passage of blood vessels meant to keep the membrane alive as well as to allow for a connection point for the membrane itself.
My doubt however came while I researched for how this should look like by looking at the joints of arthropods, when I came into contact with the strange world of fly mouthparts (particularly hoverflies), where I found out some of them have mouthparts seemingly covered up by a flexible, living membrane that apparently attached directly to the rigid parts, which left me puzzled about how my approach at wings should look like. Warning: Nightmare Fuel.
So summing up: what should an arthropod-like creature's exoskeleton look like from an anatomical perspective to accommodate for a living membrane? Given what we know about arthropods on earth, would this "soft" line along the animal's body and limbs be truly necessary for the attachment of the membrane and passage of nutrients or would it be possible to attach it directly to the hardened parts with only certain openings near the joints being enough for the passage of nutrients? I haven't been able to find further details on any similar kind of membrane in arthropods other than this case, and even then I couldn't find much about it.
Their overall body shape and wing membrane attachment is similar to that of an azhdarchid pterosaur