Contents

22 November 2019
Vol 366, Issue 6468

About The Cover

Cover image expansion

COVER Onthophagus sagittarius dung beetle with prominent horns on its head and thorax. The thoracic horn, an evolutionary novelty whose origin has been a long-standing mystery, is derived from the same serially reiterated tissues that gave rise to wings in the more posterior thoracic segments. By textbook definition, evolutionary novelty requires the absence of homology, yet thoracic horns, considered a classic example of this phenomenon, appear to have originated by relying deeply on their homology to wings. See pages 946 and 1004.
. Photo: Alexander Wild