Alexander Nützel, Pavel Parkhaev, Michael Schrödl and Ellen E. Strong in Malacologia, 2017, 61(1–2): 1–526. The authors have reverted to adopting the traditional ranks above superfamily: order, subclass, as this was preferred by many users. Context Systems of classification such as this one are primarily of value to malacologists (people who study mollusks) and other biologists. Biological classification schemes are not merely a convenience, they are an attempt to show the actual phylogeny (the evolutionary relatedness) within a group of organisms. Thus, a taxonomy such as this one can be seen as an attempt to elucidate part of the tree of life, a phylogenetic tree. The Bouchet & Rocroi 2005 system of gastropod taxonomy was laid out in a book-length paper entitled "Classification and Nomenclator of Gastropod Families", which was published in the journal Malacologia and which was written in collaboration with J. Frýda, B. Hausdorf, W. Ponder, Á. Valdés and A. Warén. This system supersedes the system of Ponder and Lindberg from 1997. Subsequent revisions by other authors have been made since the publication of this paper. The taxonomy set out by Bouchet & Rocroi is an attempt to get one step closer to representing this part of the evolutionary history of the phylum Mollusca. Bouchet & Rocroi's classification system is a hybrid of the pre-existing, more traditional Linnaean taxonomy along with some more recent far-reaching revisions which are based on molecular work and use clades as taxa, (see cladistics). In the past, the taxonomy of gastropods was largely based on the morphological characters of the taxa, such as the shell characteristics (including the protoconch) in shelled species, and the internal anatomy, including the structure of the radula and details of the reproductive system. Recent advances are based more on the molecular characteristics of the DNA and RNA. This shift in emphasis has meant that the newer taxa and their hierarchy are subject to debate, a debate that is not likely to be resolved soon. This proposed classification has tried to integrate the results of recent molecular work by using unranked clades for taxa below the traditional rank of class (class Gastropoda) but above the rank of superfamily (replacing the ranks subclass, superorder, order, and suborder), while still using the traditional Linnaean ranks for superfamilies and all taxa below the rank of superfamily (i.e., family, subfamily, tribe, genus, subgenus, and species. The clades have been given names which are