 The body is rather laterally compressed and tapers towards the tail , with two dorsal fins set far back . The first dorsal fin originates over the rear of the pelvic fins and is much larger than the second , which originates over the midpoint of the anal fin base . The bases of the pectoral and pelvic fins are about equal ; the pectoral fins are large and broad while the pelvic fins are much lower . Adult males have stubby claspers with the inner margins of the pelvic fins partially fused over them to form an " apron " . The caudal fin is short and broad , with an indistinct lower lobe and a ventral notch near the tip of the upper lobe . The very thick skin is covered by well @-@ calcified dermal denticles . Each denticle has an arrowhead @-@ shaped crown with three posterior points , mounted on a short stalk . 
