How to Identify Hammerhead Shark

To identify Hammerhead Shark (Sphyrnidae), look at these key features.

Physical Characteristics

Body shape

torpedo

Coloration

Dorsal surface typically dark olive-green to brownish-grey, fading to white or off-white on the ventral side. This countershading provides camouflage in open water.

Scale type

placoid

Mouth position

inferior

Distinctive features

Cephalofoil (hammer-shaped head), Eyes and nostrils positioned at the ends of the cephalofoil, Large, sickle-shaped first dorsal fin, Asymmetrical caudal fin with a prominent upper lobe

Dorsal fin

Two dorsal fins; the first is large, erect, and sickle-shaped, originating over or slightly behind the pectoral fin axil. The second dorsal fin is much smaller.

Tail fin

Heterocercal (asymmetrical) caudal fin with a well-developed upper lobe and a smaller, but distinct, lower lobe.

Pectoral fin

Moderately large and falcate (sickle-shaped).

Distinctive fins

The cephalofoil itself is the most distinctive 'fin-like' structure, though it is a head modification.

Identification Tips

1. 1

   Cephalofoil Shape

   The shape and width of the 'hammer' are key. For example, the Great Hammerhead (Sphyrna mokarran) has a very broad, almost straight-edged cephalofoil, while the Scalloped Hammerhead (Sphyrna lewini) has a distinctly scalloped or indented front margin.

2. 2

   First Dorsal Fin

   The size and shape of the first dorsal fin are important. The Great Hammerhead has a very tall, falcate first dorsal fin. The Smooth Hammerhead (Sphyrna zygaena) has a less tall, more rounded first dorsal fin.

3. 3

   Body Size

   Overall size can help differentiate. Great Hammerheads are the largest, reaching over 6 meters, while Bonnethead Sharks (Sphyrna tiburo) are much smaller, typically under 1.5 meters.

4. 4

   Nostril Position

   The position of the nostrils relative to the eyes and the midline of the cephalofoil can be a subtle but important distinguishing feature for some species.

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