The Spadehorn is a creature indigenous to the planet Reach. It is a herbivorous animal similar to Earth bovids, named for its pair of flat-tipped spade-like horns. When humans settled Reach, the spadehorn was domesticated.

It is the namesake of the TurboGen IWDS "Spade" truck, a vehicle widely used by rural farmers on Reach.[1]

Trivia

The Spadehorn was originally to appear in Halo: Reach as ambient wildlife. Concept sketches were created for three different varieties of the creature; the Highlands Spadehorn, Prairie Spadehorn and Angelhorn, each with different shaped horns.[2]

Sources