Kellner estimated the wingspan of
Caupedactylus at , making it the largest known tapejarine. The skull is about forty-six centimetres long. Some unique traits,
autapomorphies, were established. The snout sports a crest on the
premaxilla extending both to the front and to the rear of the skull. The point of the snout curves downwards combined with a slightly concave lower edge of the upper jaw. The paired points of the snout are not separated. The ascending branch of the jugal bone, connecting to the lacrimal bone, is strongly reclining at an angle of 115 degrees. In the rear of the palate a reduced split-shaped
fenestra postpalatina is present. The quadratum reclines 150 degrees relative to the lower edge of the skull. The basisphenoid of the lower braincase lacks appending processes. The basisphenoid does not reach the space between the pteroids. The rear half of the lower edge of the symphysis of the lower jaws is thick, forming a slightly convex surface. The skull is crowned by a large rounded crest that continues to behind, descending over the parietals. The crest is very thin, about half a millimetre at the upper part. The jaws are toothless. The profile of the symphysis of the lower jaws closely fits the edge of the upper jaws: when closing the beak, no gap would have remained. The symphysis has a low keel at the underside. The palate is well-preserved and seems to show that the traditional interpretation of its bones is the correct one, contra the more modern view that what have usually been seen as the fronts of the palatine bones would really be the internal wings of the
maxillae. ==Classification==