Variation in venous drainage of the pectoral fins of batoids (subclass elasmobranchii: Superorder batoidea).

A contrast radiographic study of pectoral fin venous drainage in rays shows it to be morphologically conservative across the batoids studied. In all species examined, ventral propterygial and mesopterygial veins drain the anterior and posterior lobes of the fin, respectively. Variation in the central connections of these vessels enables the identification of four major patterns of drainage. A fifth pattern consists of additional veins that drain the central region of the fin between the zones drained by the pro- and mesopterygial veins. There is a significant, positive association between the numbers of brachial veins present and the dimensions (in numbers of radial cartilages) of the central, basal region of the fin. There is also an association between the types of patterns present and the dimensions of the propterygial and metapterygial basal cartilages.