The Sark was a riding animal native to Qo'noS, roughly analogous to a Terran horse.
Simulations of this animal were on file as holograms in the USS Enterprise-D holodeck. In 2365, Jean-Luc Picard rejected it in favor of a horse. (TNG: "Pen Pals")
The Klingon term for Sark is Sargh (ʂɑrɣ), and a horse would be called a "Terran Sark" (tera' Sargh).