Vertebrate Zoology - V. M. Konstantinov 2011

Chordates
Terrestrial, or Tetrapod, Vertebrates

The superclass Tetrapoda (terrestrial or four-limbed vertebrates) comprises vertebrate animals that are adapted to a terrestrial existence to varying degrees: amphibians, reptiles, birds, and mammals. Some members of these classes have secondarily evolved to become partially or fully aquatic.

Unlike fish, they rely on pulmonary Respiration, with air entering the Lungs through through-pass nostrils. The absence of lungs (as seen in lungless salamanders, for instance) is clearly a secondary evolutionary trait. Their paired limbs are pentadactyl, structured as multi-jointed levers. This design allows not only the entire limb to move relative to the body, but also enables individual limb segments to articulate independently of one another. Limblessness is likewise a secondary adaptation (found in snakes and certain lizards). The tetrapod Circulatory system features two distinct circuits of Blood Circulation.

The superclass includes four classes: Amphibia (amphibians), Reptilia (reptiles), Aves (birds), and Mammalia (mammals).



Last update: 13/08/2026

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