How to Identify Dogfish Sharks

To identify Dogfish Sharks (Squaliformes), look at these key features.

Physical Characteristics

Body shape

torpedo

Coloration

Typically grey, brown, or black dorsally, often lighter ventrally. Some deep-sea species are uniformly dark. Many lanternsharks (family Etmopteridae) possess photophores for bioluminescence.

Scale type

placoid

Mouth position

inferior

Distinctive features

Absence of an anal fin, Two dorsal fins, often with spines (though spines may be absent in some species), Five gill slits, Nictitating membrane absent, Spiracles present, Often possess dermal denticles that give the skin a rough texture

Dorsal fin

Two dorsal fins, typically with spines (pre-dorsal spines) that can be grooved and venomous in some species (e.g., Squalus spp.). The first dorsal fin is usually larger than the second.

Tail fin

Heterocercal caudal fin, with the upper lobe typically longer than the lower lobe.

Pectoral fin

Moderately sized, triangular to rounded pectoral fins.

Distinctive fins

Pelvic fins are present. Anal fin is entirely absent, a key diagnostic feature for the order.

Identification Tips

1. 1

   Absence of Anal Fin

   This is the most definitive characteristic. If a shark lacks an anal fin, it belongs to the order Squaliformes.

2. 2

   Dorsal Fin Spines

   Many Squaliformes species possess prominent spines anterior to their dorsal fins. The presence or absence, and the size/shape of these spines, can help differentiate families and genera.

3. 3

   Body Shape and Size

   While generally torpedo-shaped, there is variation. Dogfish sharks (Squalidae) are typically slender, while sleeper sharks (Somniosidae) can be very large and robust. Lanternsharks (Etmopteridae) are generally small.

4. 4

   Coloration and Photophores

   Observe overall color. For deep-sea species, look for bioluminescent photophores, particularly in lanternsharks.

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