Chordate Zoology - Textbook - I. V. Tsaryk - 2013

Chapter 5. SUPERCLASS TETRAPODS (TERRESTRIAL VERTEBRATES) TETRAPODA, seu QUADRIPEDA.

ANAMNIOTS (ANAMNIA) AND AMNIOTES (AMNIOTA)

5.3. CLASS BIRDS AVES

5.3.3. Taxonomy and characteristics of representatives of the main orders of the class Aves

5.3.3.1. Superorder Swimming Birds Impennes

5.3.3.1.1. Order Penguins Sphenisciformes

The superorder Impennes includes only a single order — Sphenisciformes, with 16 (17) extant species. They are distributed across the Southern Hemisphere, with the majority of species inhabiting the Subantarctic islands and Antarctica. Flightless, they are proficient swimmers and divers. Their forelimbs are modified into flippers, which serve as propulsive Organs during swimming and diving; short hindlimbs act as rudders, and the toes are webbed. On land, they stand and walk with an upright posture. Wing bones are flattened, joints have limited mobility, and the Pectoral Girdle and Sternum keel are well-developed. Feathers are densely set in the Skin and fit closely together, preventing Water and wind penetration. Significant fat deposits are present in the subcutaneous Connective Tissue, serving a thermal insulation function.

They feed at sea on small fish, crustaceans, and Mollusks. They nest in colonies that can number tens of thousands of pairs, which remain stable for several years. They lay 1-2 eggs in short burrows, rock crevices, or directly on the ground. Both partners incubate the eggs in turns. Chicks hatch altricial-like (sighted, covered in dense short down), and are fed by the parents for 3-6 months. Outside the breeding season, they roam the sea, only occasionally coming ashore to rest. Small penguin species have a mass of 1.5–3.0 kg, while the largest, the Emperor Penguin Aptenodytes forsteri, reaches up to 40 kg (Fig. 5.45, 1).