Aplacophoran Mollusca in the Natural History Museum Berlin. An annotated catalogue of Thiele's type specimens, with a brief review of “Aplacophora” classification

Abstract

Aplacophoran molluscs are a small, often neglected and still poorly known but phylogenetically important basal group, with taxa possessing morphological characters considered essential for the reconstruction of the basal Mollusca and their evolution. Currently, in most textbooks of zoology and major malacological treatise Solenogastres and Caudofoveata are viewed as constituting a monophyletic clade called Aplacophora Von Ihering, 1876, although evidence is available to the contrary, suggesting the latter to be a paraphyletic grade. Accordingly, the hitherto accepted “Aplacophora” may consist of two Recent, diphyletic taxa, viz. Solenogastres Gegenbaur, 1878 (sensu Simroth, 1893) or Neomeniomorpha Pelseneer, 1906 (also called Ventroplicida Boettger, 1955) and Caudofoveata Boettger, 1955 or Chaetodermomorpha Pelseneer, 1906. The Museum of Natural History Berlin (formerly Zoological Museum Berlin, ZMB) houses rich type material essentially of Solenogastres on which to a substantial degree the preeminent German malacologist Johannes Thiele (1860–1935), working as curator in this collection from 1905 on, has based his respective systematic accounts of that time. A review given here briefly outlines the historical development of knowledge on the systematics and phylogeny of aplacophoran molluscs allowing two conclusions: First, that evidendently Thiele struggled with the very same problems of molluscan classification as we still do more than a century of zoological systematics later; and second, that Thiele's erroneous assumption of Solenogastres being closely related to annelids rather than molluscs resulted in the deposition of aplacophoran material of the ZMB (and hence the late re-discovery of it) in the “Vermes” department, then initiating this annotated type catalogue. Here we provide information on a total of 31 aplacophoran taxa in the ZMB, including notes on type specimens and localities, their original description and current systematic placement. The majority (i.e. 25 taxa) are represented by types, essentially being named by Thiele in 23 cases. With the exception of one caudofoveate, all these aplacophoran molluscs in the ZMB are Solenogastres. Following recent classification they are assigned to 20 genera. The type material was mainly collected by German imperial expeditions, which are briefly reviewed, in particular the First German South Polar Expedition on board of the sailing vessel “Gauss”, 1901–1903, with a total of 15 new aplacophoran species, all from the very same type locality near the Antarctic Gaussberg volcano at 66°2′S, 89°38′E, collected by the expedition's biologist Ernst Vanhoffen. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)