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146 ral nervous system, a radula with different numbers of teeth per row, as well as – uniquely among molluscs – a reproductive system with gonads emptying into the pericard and secundary gametoducts; for detailed accounts on anatomical characters in aplacophoran molluscs see the general treatments e.g. by Simroth (1893b), Thiele (1913c, 1925), Hoffmann (1929), Fischer-Piette & Franc (1960), Hyman (1967), Salvini-Plawen (1967, 1971, 1972, 1985), Scheltema et al. (1994) and Scheltema (1998). Although aplacophoran molluscs are a small group of animals ranging from 1 mm to 30 cm, and are only rarely preserved even in major museum collections, they actually represent a phylogenetically highly important group, with constituent taxa possessing morphological characters considered essential for the reconstruction of the evolution of Mollusca; see e.g. recent reviews and discussions in Salvini-Plawen (1967, 1972, 1985, 2003a), Scheltema (1978, 1993, 1996), Ivanov (1996), Salvini-Plawen & Steiner (1996) and Haszprunar (2000). However, the curious and unique mixture of plesiomorphic and derived features of aplacophorans have contributed to long-standing disputes as to the phylogenetic relationships not only to other mollusc groups but also among these shell-less taxa that apparently modified many of their anatomical characteristics in dramatical ways. Ongoing controversies include the question of the validity of the Aculifera or Amphineura concepts (the latter going back to Ihering (1876)), that both propose Aplacophora Ihering, 1876 and Polyplacophora Gray, 1821 as adelphotaxa, or the question whether Aplacophora are monophyletic. While molecular phylogeny point to a diphyletic origin, it was unable to propose probable sister group relationships to other molluscan groups (for reasons given below). Most currently used text books in zoology (e.g. Götting 1985, 1996; Brusca & Brusca 2003) and some monographic malacological accounts (e.g. Scheltema 1996, 1998, 2001) thus continue to perceive Aplacophora and Aculifera as monophyletic taxa. This conservative view is largely ignoring available evidence for an alternative systematization according to cladistic analyses that suggest the latter two taxa being paraphyletic assemblages (i.e. grades) only, both representing basal, independent off-shoots of Mollusca (Salvini-Plawen & Steiner 1996; Haszprunar 2000). The unresolved phylogenetic issues currently compromise our understanding of molluscan origin and # 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Glaubrecht, M. et al., Aplacophoran Mollusca in the Natural History Museum Berlin early evolution; for a recent discussion in a broader molluscan framework see e.g. Salvini- Plawen & Steiner (1996), Salvini-Plawen (1990) and Lindberg & Ponder (1996). The systematics within aplacophoran molluscs is also partly unresolved. According to traditional knowledge the aplacophoran molluscs comprise two higher level taxa (subclasses or proper classes) with strongly distinct anatomical habitus and habits. In most classifications these taxa are separated as Solenogastres Gegenbaur, 1878 (sensu nomine Simroth, 1893) and Caudofoveata Boettger, 1956. The naming and separation of both groups – that were first discovered in Scandinavian waters in 1844 (Chaetoderma nitidulum Lovén, 1845) and 1875 (Neomenia carinata Tullberg), respectively – refers to the presence of a small foot within a ventral groove in Solenogastres (thus “Furchenfüßer” or “Bauchfurcher” in German) or its absence in Caudofoveata (“Schildfüßer”). Solenogastres lack a cuticular oral shield and posterior ctenidia, live mostly cnidarivore and even epizoic on animal colonies (such as Octocorallia and Hydrozoa) or benthic and are hermaphrodtites. In contrast, a cuticular oral or pedal shield and paired ctenidia are present in the Caudofoveata which live benthic and burrowing in marine soft sediments where they move by hydrostatic action; the latter are micro-omnivore to micro-carnivore (feeding on debris, foraminiferans and other small organisms) and are of separate sex. Unfortunately, our knowledge of the biology of aplacophorans is still fragmentary. While only about 120 species of Caudofoveata are known so far, about 240 species of Solenogastres have been named, with new ones currently under description. This relation in species number is also more or less reflected by the extant historical material in the ZMB where Solenogastres largely dominate (see below). Undoubtedly, the latter taxon is not only specious but also more diverse in respect to habitats used, which can be benthic, epizoic, and meiofaunal or even burrowing. In recent years several new additions come from various regions of the world, as is evident from the descriptions of new taxa of different Solenogastres from Norway (Handl & Salvini- Plawen 2001, 2002), from the Mediterranean Sea (Salvini-Plawen 2003b) from the Western Indian Ocean (Todt & Salvini-Plawen 2003), from the southern hemisphere (Salvini-Plawen & Paar- Gausch 2004) and from various other regions (Salvini-Plawen 2004), as well as Caudofoveata
Mitt. Mus. Nat.kd. Berl., Zool. Reihe 81 (2005) 2 / http://museum-zool.wiley-vch.de 147 (Prochaetodermatidae) of the Atlantic Ocean and Mediterranean Sea (Scheltema & Ivanov 2000) or the Indian and Pacific Oceans (Ivanov & Scheltema 2002, 2004). Apart from the monograph of antarctic-subantarctic Solenogastres with 75 new species (Salvini-Plawen 1978) another striking example for the recent increase in knowledge is the Australian region, where apparently a rich and diverse fauna exists in the southeast of the continent with at least 32 species in 14 or more genera, some still awaiting description (see Scheltema 2001). Prior to this recent survey only two species were recorded by Thiele (1897), viz. Notomenia clavigera and “Proneomenia” (¼ Epimenia) australis of which the types are extant in the ZMB collection (see below). Irrespective of their rare representation in most collections, aplacophorans form a numerically small but consistent deep-sea faunal element; some taxa are apparently common and sometimes form an abundant part of the shelf, bathyal, abyssal and hadal oceanic benthic macrofauna from depths of c. 200 m to 9000 m (see Belyaev 1966). Since representatives of both aplacophoran taxa are found in deeper water on the continental shelf and in the deep-sea down to the abyssal zone and even at hydrothermal vents, they are generally not only less accessible than other molluscs; since they are often small, with many being less than five millimeters (but also reach exceptionally 300 mm), they certainly represent a neglected part of the Mollusca; for a review of the biology of aplacophorans see, for example, Salvini-Plawen (1971, 1985) and Scheltema (2001). Not only recent discoveries of new taxa have spurred aplacophoran research, but also renewed interest in the phylogeny of metazoans in general and mollusca in particular. Clearly, their systematics with respect to the new findings is still in flux and continuously has to be adapted. However, in view of the fact that traditional classifications did apparently neither reflect the phylogenetic affinities among nor within the two major groups Solenogastres and Caudofoveata, the actual systematics in general appears to be in accordance with computerized cladistic analysis (Salvini-Plawen 2003a). Nevertheless, this situation all the more strengthens the importance of historical museum material. The recent interest in aplacophoran classification often necessitates the re-examination of this archival material in particular of the many taxa of Solenogastres named by one of the former leading malacologists, Johannes Thiele. This re-examination of ZMB material resulted, for example, in the recent transfer and re-description as type species of a new genus, as in the case of Thieleherpia thulensis (Thiele 1900) by Salvini-Plawen (2004: 86), and in the erection of a new family Notomediidae, based on the reexamination of the type species of the respective genus Notomenia clavigera Thiele, 1897 (see Salvini-Plawen 2004: 89). The revision of earlier descriptions in light of new material, collections and taxa described will eventually allow more accurate systematics at the generic and family level as shown, for example, recently in the Clavibelonia (cf. Salvini-Plawen 2004). Again, this underscores the importance of historical collections such as Thiele’s type material of aplacophorans. Therefore, the objective in the present paper is twofold. The Museum of Natural History of Berlin (formerly Zoological Museum Berlin, ZMB) houses rich type material of aplacophorans, particularly Solenogastres, which are evidently of basic importance for any systematic evaluation of these molluscs. This material stems to a substantial degree from the systematic work of the former curator of the Berlin Malacological Collection, Johannes Thiele (1860–1935), who was certainly one of the preeminent malacologists of the twentieth century. Following positions as assistant in the invertebrate section of the Dresden Museum für Tierkunde (1891– 1895), Strassburg’s Zoological Institute (1895– 1896) and Göttingen’s Zoological Institute (1896–1898), Thiele took a position as a lecturer at the Zoological Institute in Berlin in spring 1898, before starting as a scientific collaborator or helper at the Zoological Museum in Berlin in spring 1899, where he became Research Assistant in 1900, then curator of the Crustacea Section in 1903, before he finally took charge of the Mollusk Section in 1905, after the death of Eduard von Martens (1831–1904). Thiele worked there also after his official retirement (in 1925) until his death in 1935. For a brief biography, including a bibliography, see e.g. Bieler & Boss (1989). The Solenogastres were among the molluscan groups Thiele paid particular attention to, culminating in his revision of this taxon in Das Tierreich (Thiele 1913c). Among the total of 291 genus-level taxa in the phylum Mollusca introduced by Thiele, there are 11 aplacophoran names (see Boss & Bieler 1991), to which at least 24 new Solenogastres species names by Thiele can be added according to the material # 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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