Chordate Zoology - textbook - Y. V. Tsaryk - 2013

Chapter 4. DIVISION GNATHOSTOMATA, or ECTOBRANCHIATA. SUPERCLASS PISCES

4.1. CLASS CARTILAGINOUS FISHES CHONDRICHTHYES

4.1.4. Systematics

4.1.4.1. Subclass Elasmobranchii

Modern elasmobranchs originated about 150 million years ago.

This subclass is divided into two superorders: sharks, or selachians, and rays, or batoids. Together, they comprise 13 orders (Fig. 4.16).

Elasmobranchs never have gill covers. The gills open via 5-7 slits on each side of the body. The gill lamellae are plate-shaped and attached to the arches along their entire length (hence the name elasmobranchs).

Elasmobranchs are highly diverse in shape and size. Some have a torpedo-shaped body, while others are flattened. The length of some catsharks does not exceed 15-30 cm, whereas the whale shark can reach 15-20 m in length and weigh several tons.

Members of the shark superorder have an elongated body. The body of pelagic species resembles a torpedo and possesses high hydrodynamic properties. The gill slits are located on the sides of the HEAD. The fins are well developed.

The lifestyle of sharks is diverse. All of them feed on animal food, and most are true predators. Only the whale, basking, and recently studied deep-sea sharks are planktivorous; the number of sharks feeding on benthos is also small.

Attacks on humans by tiger, white, sand, hammerhead, and other sharks (29 species in total) have been documented. The complete list of potentially dangerous sharks includes more than 50 species.

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Fig. 4.16. Representatives of sharks:

A - porbeagle Lamna nasus; B - basking shark Cetorhinus maximus;

C - Japanese sawshark Pristiophorus japonicus; D - angelshark Squatina squatina



Last update: 19/08/2026

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