Complex sentence: The hummingbirds, swifts and crested swifts share other anatomical similarities with one another as well as similarities (notably as to the skull) with their probable closest living relatives, the owlet-nightjars (Mayr, 2002).
Split into simpler sentences: The hummingbirds, swifts and crested swifts share other anatomical similarities with one another. They also have similarities (notably as to the skull) with their probable closest living relatives, the owlet-nightjars (Mayr, 2002).