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Ward's World + MGH Sphenisciformes

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Sphenisciformes Article by: Walter J. Bock, Department of Biological Sciences, Columbia University, New York, New York. Access to this content is available to Ward's World readers for free from McGraw Hill's AccessScience, an award-winning, digital STEM resource containing exclusive articles written by expert scientists and engineers; biographies of well-known scientific figures; science news, videos, and animations; and much, much more. Instructors can use AccessScience to guide students on their research project journeys, to help students understand scientific concepts, to support distance learning efforts, in flipped classroom approaches, and in countless other ways. Ward's World and AccessScience have partnered to offer educators a no-obligation, free trial subscription to AccessScience. Request your free trial today to discover how valuable AccessScience can be for you and your students! Get your free trial now. A small monotypic order of flightless, marine swimming birds, comprising the penguins, found predominantly in the colder southern oceans. Penguins (Fig. 1) constitute the order Sphenisciformes in the class Aves. Depending on the classification scheme, there are about 17 to 19 species of penguins. These aquatic, flightless birds most likely evolved from members of the order Procellariiformes, perhaps from a diving petrel-like ancestor. Classification schemes that hypothesize a link between penguins and loons (order Gaviiformes) have no factual support. At one time, members of the present Sphenisciformes had been placed in a separate superorder, Impennes, but such a desig- nation suggested too great a divergence of the penguins from their ancestral group of tube-nosed swimmers. Some taxonomists have enlarged the Ciconiiformes to include the Sphenisciformes, as in the Sibley-Ahlquist taxonomy [a radical new approach to taxono- my, based on deoxyribonucleic acid (DNA) hybridization studies]. Characteristics Penguins are medium-sized to large birds. They are completely flightless, with their wings having been modified into stiff flattened flippers. They stand upright on legs that are placed far posterior and that terminate in four toes; the anterior three toes are webbed. Penguins swim and dive well, using only their wings for propulsion: their feet are used only for steering during swimming. Terrestrial locomotion is by walking, hopping, or sliding on the belly while pushing with the wings. The plumage consists of dense scalelike feathers that are black dorsally and white ventrally. A distinctive pattern or crest, often yellow, oc- curs on the head (Fig. 1). + ward ' s science Content • Characteristics • Habitat • Fossil record Fig. 1: Aptenodytes patagonicus, the king penguin. (Credit: Gerald and Buff Corsi; copyright © California Academy of Sciences) Key Concepts • The sole members of the taxonomical order Sphenisciformes are penguins, which chiefly inhabit the colder southern oceans. • Penguins are medium-sized to large birds, but are flightless. Their wings have been modified into stiff flattened flippers, enabling them to swim. • Socially, penguins are gregarious and breed in large colonies along coastal areas. • Male and female penguins form strong pair bonds and share in the incubation and care of the young. • Fossils of penguins have been found in Antarctica, Australia, and South Africa, approximating the range of present-day species.

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