Summary
Accessory (supernumerary) antlers are an infrequent phenomenon in male cervids. These bony protuberances grow mostly from permanent pedicles, which developed in response to a repeated or a severe trauma to frontal, nasal or parietal bones. They regularly undergo seasonal mineralization, casting and regrowth and may persist for many years. Three examples of accessory antlers in telemetacarpal cervids, roe deer (Capreolus capreolus), white-tailed deer (Odocoileus virginianus) and moose (Alces alces), are presented. The initiation of accessory antlerogenesis, the progress of growth and development, and the mineralization and casting of accessory antlers were mostly identical or similar to processes observed in the antlerogenesis of lateral antlers. The antlerogenic property of the competent periosteum, located within the “antler territory”, appears to play a crucial role in the development of accessory antlers. The variability in location and the progress of development of accessory antlers, which were observed in several antlerogenic cycles, is discussed in relationship to the origin of deciduous antlers in extinct ancestors of cervids.