Linked from
The 7 pages that link to Horns, each with the reason it gives.
CaprinaeRelated: Most caprine species have horns, though their shape and presence vary.
AntelopeRelated: Bovid antelope horns grow from permanent cores and are usually unbranched.
MuskoxRelated: Muskox horns have broad bases and curved tips used in defense and competition.
SerowRelated: Serows bear short, backward-curving horns rather than antlers.