This publication is devoted to an academic description of the pneumopteria, a species which is considered extinct as a result of human action. Pneumopteria are also referred to as aerial creatures, cloud whales or cloud sponges, and occasionally, in scientific language, as pneumospongia. Often, in older treatises, they have been termed celestial leviathans. These gigantic, cloud-like creatures, which seem to float in the air without movement or stimulation, can reach several hundred metres in size. They were frequently observed and described, especially in historical times.With his fictional research on actual or imaginary persons, situations, and objects, Roland Boden provides the first thorough introduction to the nature, appearance, and behaviour of pneumopteria. He elaborates on aspects of the history of the exploration, specification, and classification of the species. In his treatise, Boden presents photographs, reproductions, prints, reconstructive drawings, and computer-generated images, combining numerous real scientific and historical facts with completely fictitious elements to create a parallel reality that cleverly questions contemporary perceptual processes.Text in English and German.