Lewis & Short

dorsŭālis, e, adj. [dorsum], of or on the back, dorsal (post-class): notae equi, App. M. 11, p. 266, 32; cf.: crustae ferarum, Amm. 22, 15; and, pinnae, Sol. 12.
Subst.: dorsualia, ium, n., a cover for the back of beasts, Trebell. Gallien. 8.