Receptaculitids are extinct high-level fossils that provide a window into the history of life. After the discovery and analysis of a deposit of phosphatized receptaculitids on the Baltic Sea island of Öland, the authors conclude that receptaculitids possess an attribute not found in any other group of organisms, living or fossil.

Inhalt
I. Introduction.- Enigma of Problematic Fossil Taxa.- Terminology.- II. The Biography of an Idea.- Early Work.- Reports in English.- Rauff's Analytical School.- Baltic Receptaculitids.- III. Geology.- Stratigraphic and Geographic Distribution.- Mineralogy.- Preservation.- IV. Morphological Characteristics of Fisherites orbis.- General Characteristics.- External Characteristics.- Internal Characteristics.- V. Morphology of a Merom.- Membrane.- Head.- Shaft.- Foot.- VI. Quaestio disputata: Morphological Reductionism.- Comparative Morphological Characteristics.- Axiomorph.- Skeleton.- Animals.- Plants.- VII. Summary and Beyond.- Receptaculitid Is But A Name.- Learning What They Are, Are Not, and Should Be.- Addendum. Horns of Dilemma: Phosphatization.- References.- Authors Index.- Taxonomic Index.