Franz Hilgendorf's dissertation '︁Beiträge zur Kenntnis des Süßwasserkalks von Steinheim' from 1863: Transcription and description of the first Darwinian interpretation of transmutation

Franz Martin Hilgendorf (1839–1904), assistant and later curator at the Natural History Museum in Berlin, is mainly known for his palaeontological studies about Miocene planorbids of the Steinheim Basin, Southern Germany, a topic on which he already wrote his dissertation in 1863. After having been introduced to the geology and in particular stratigraphy of Steinheim in summer 1862 by his teacher Friedrich August Quenstedt, who later did not follow his interpretations, though, Hilgendorf traveled to Steinheim repeatedly. Based on these studies he published between 1866 to 1901 several papers on transformation series, or Formenreihen, of the freshwater gastropod “Planorbis multiformis ” (today assigned with several species to the genus Gyraulus), which reflect a scientific controversy that lasted for another century. Following earlier hints as to its existence, we re-discovered Hilgendorf’s original, handwritten dissertation of 42 pages in the archives of the Berlin Natural History Museum (Historische Arbeitsstelle), together with a rich literary bequest that has not been studied yet. Discussing some of its implications, we here present for the first time a complete transcription of Hilgendorf’s German text that had never been published before, showing that he at that very early stage explicitly contextualized his Steinheim findings with Darwin’s new theory of evolution, i.e. phylogenetical relationships of descendants through time. In addition, we report on and depict Hilgendorf’s curious arrangements on five cardboards, comprising the shells of planorbids as transformation series with transition of taxa, plus one card revealing his first phylogenetic tree that is found among his collection of material from Steinheim in the Palaeontological Collection of the Berlin Natural History Museum. With these Steinheim snails Hilgendorf not only described one of the first evolutionary transformations illustrating both ana- and cladogenesis, but created the first phylogenetic reconstruction on the basis of existing fossil evidence.