The rhino's single horn is present in both males and females, but not on newborn young. The black horn is pure keratin , like human fingernails, and starts to show after about six years. In most adults, the horn reaches a length of about 25 cm.
This was a little side project over the past few months. I made this rhino in ZBrush in October 2017, 3d printed it on @3dhubs in March, and finally got around to doing epoxy, primer, airbrush and detail layers in June. 🦏 🎨