A quadruped is a four-legged animal.
In his "Ode to Spot," Data noted that Spot was an "endothermic quadruped, carnivorous by nature." (TNG: "Schisms")
The Lan'Tuana sector is inhabited by quadrupeds. (VOY: "Bliss")
Doctor Phlox professed to Jonathan Archer that he had underestimated Archer's attachment to his "subservient quadruped". (ENT: "A Night in Sickbay")