Aegialornisis a genus of prehistoric apodiform bird. It formed a distinct family Aegialornithidae and was in some ways intermediate between modern swifts and owlet-nightjars, lacking the more extreme adaptations to an aerial lifestyle that swifts show today, but already having sickle-shaped wings like them. They do not appear to be a direct ancestor of modern swifts, however, but rather a group that retained an overall basal morphology. Altogether, they were not too dissimilar to modern treeswifts.