Accessory Antler Growing From the Left Zygomatic Bone of a Male Rusa Deer (Rusa timorensis).

This paper reports a case of accessory antler growth from the left zygomatic bone of a rusa stag (estimated age 7 years) shot in New Caledonia in January 2026. At the time of death, the individual was carrying orthotopic velvet antlers of about 13.5 cm length. The extra antler had grown from the lower rim of the left orbita and was covered by typical velvet. It was attached to the zygomatic bone via a bony socket that was covered by normal scalp skin and considered to represent a pedicle. The ectopic pedicle-and-antler structure (length 5.4 cm) became detached during maceration, suggesting that the connection between pedicle base and zygomatic bone had been cartilaginous rather than osseous. According to an observation of the stag's head shortly after death, a small exostosis was also present above the right eye. The distal portion of this exostosis appeared to be covered by velvet and thus may have represented a second accessory antler. However, since this region of the skull was destroyed by the shot in the head, it could not be examined after maceration. The case presented here is only the second instance of antler formation from the zygomatic bone reported in the scientific literature. Accessory antler growth was presumably caused by a trauma to the periosteum. The findings of the present study and other reports suggest that all membrane bones of the deer skull have the potential to produce accessory antlers upon strong unphysiological stimulation of their periosteum.