44 



FISHKRY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



within the limits of our Gulf, but is included here 

 on the chance that a stray specimen may be 



taken, either on the outer coast of Cape Cod, 

 on Nantucket Shoals, or on Georges Bank. 



THE HAMMER-HEADED SHARKS. FAMILY SPHYRNIDAE 



The peculiar hammer-shaped head, with eyes 

 far apart, sufficiently characterizes the Gulf of 

 Maine sharks of this family, which resembles the 

 requiem sharks (p. 36) otherwise. Five species 

 are known in the western Atlantic, all of them 

 tropical-subtropical in nature. Two of these have 

 been reported from our Gulf, but only as strays. 



Shovelhead Sphyrna tiburo (Linnaeus) 1758 



Bonnet head shark 



Bigelow and Schroeder, 1948, p. 420. 



Garman, 1913, pi. 1, figs. 4-6 (as Cestracion tiburo). 



Description. — The peculiar shovel-shaped head 

 of this shark is enough to distinguish it readdy 

 from any other shark known from the Gulf of 

 Maine, except for the hammerhead, from which it 

 is readdy distinguished by the fact that its head 

 is considerably narrower, is more rounded in front, 

 and is not deeply indented opposite each nostril; 

 that the posterior margin of its anal fin is only 

 weakly concave, and that the outermost four or 

 five of its lower teeth next each outer corner of its 

 mouth are low and rounded, not blade-like. The 

 eyes of the shovel-head shark, like those of the 



hammerhead, stand at either edge of the expanded 

 head; the first dorsal fin originates a little behind 

 the "armpit" of the pectoral, is somewhat higher 

 than the pectorals are long, and is higher than 

 long; the very small second dorsal fin originates a 

 little behind the origin of the anal fin; the upper 

 lobe of the tad is notably long (about one-third as 

 long as the body of the fish) and deeply notched 

 near the tip, the lower lobe is about one-third as 

 long as the upper lobe. The anal fin is larger than 

 the second dorsal fin, its posterior margin is only 

 slightly concave ; the pectorals are broadly triangu- 

 lar, their anterior margins about as long as the 

 distance from the level of their own points of 

 origin to the front of the mouth. 



Color. — Gray or grayish brown above, and a 

 paler shade of the same below; some are marked 

 with a few small dark, roundish spots along the 

 sides. 



Size. — This shark is much smaller than the 

 hammerhead, rarely exceeding 5 feet in length; it 

 is said to reach 6 feet. 



General range. — Tropical-warm temperate At- 

 lantic; from southern Brazd to North Carolina, 

 in the west, and as a stray to southern New 

 England and Massachusetts Bay; tropical West 

 Africa in the east; also from southern California 



Figure 15. — Shovel head (Sphyrna tiburo), female, about 14% inches long, from Rio de Janeiro. A, under side of head; 

 B, first to seventh upper teeth and first to sixth lower teeth counted from center of jaw, about 3.6 times natural size. 

 From Bigelow and Schroeder. Drawings by E. N. Fischer. 



