Historical clue formulations

• Spiral-horned antelope — 2018-02-03
• African antelope with curvy horns — 2016-05-24
• Spiral-horned grazer — 2015-09-13
• Beast hunted by Hemingway in "Green Hills of Africa" — 2013-08-31
• Striped antelope — 2003-12-16
• Antelope with twisty horns — 2003-03-01