The Arsartis, Arsarticaedes agilis, is an unusual, solitary, mountain-dwelling dromaeosaur that moves quadrupedally. It measures 8-12 feet long. Bizarre theropods, the racy Arsartis is the principal hunter of the mountain Bifurcatops herds. In a reversal of evolutionary trends, Arsartis has returned to a four-legged gait like with many non-dinosaurian dinosauromorphs for greater stability as it hurls itself along the treacherous terrain of the crumbling uplands in pursuit of prey. A solitary killer, it will use cover to get as close to prey as possible before initiating a chase, and then run it down with superior speed and maneuverability. Kills are made catlike, pinning the prey animal down with its foreclaws while delivering a lethal bite.