dorsal (dor'-sal). (a) Pertaining to, or situated near or on, the back (not the hind end) or upper surface of an animal or of one of its parts; e.g. toward the brachial valve from the pedicle valve of a brachiopod, or pertaining to the hinge region of the shell of a bivalve mollusk, the side of the uniserial stipe opposite the thecal apertures of a graptoloid, or the spiral side of a trochoid foraminifer. (b) Referring to the direction or side of an echinoderm away from the mouth, normally downward and outward, e.g. toward the point of attachment of the column with blastoid theca or to the part of the crinoid or cystoid calyx located toward the column; aboral. (c) In vertebrates, toward the part of the animal that bears the spinal cord (rather than toward the belly). Ant: ventral.