Meded. Tert. Kwart. Geol. 171-180 2 1987 Werkgr. 24(1-2) pp. figs Leiden, June Evolution and stratigraphical distribution of Oligocene and Miocene Scaphopoda in the North Sea Basin — a preliminary report by Ronald Janssen Forschungsinstitut Senckenberg, Frankfurt am Main F.R.G. Janssen, Ronald. Evolution and stratigraphical distribution of Oligocene and Miocene Scaphopoda in the North Sea Basin — a preliminary report. — Meded. Werkgr. Tert. Kwart. Geol., 24(1-2): 171-180, 2 figs. Leiden, June 1987. As a result of a taxonomical revision of Oligocene and Miocene scapho- pods ofthe North Sea Basin observations on stratigraphical distribution well of as as on evolutionary lineages species are presented. There are from the the two important lineages reaching Latdorfian, resp. Rupelian, to the Vierlandian (Fissidentalium novaki-lineage and Antalis Miocene geminata-lineage) and one (Reinbekian to Syltian) lineage (based on Fissidentalium “badense” auct.). Assemblages of scaphopod species characterize different facies in the Rupelian, but stratigraphical units in the Hemmoorian. Most previous assumptions as to identity of species and their development in the North Sea Basin appeared to be incorrect. Dr R. Janssen, Forschungsinstitut Senckenberg, Senckenberganlage 25, D-6000 Frankfurt am Main, Federal Republic of Germany. Contents: 172 Samenvatting, p. Zusammenfassung, p. 172 172 Introduction, p. of in the North Sea Basin, 174 Evolutionary development scaphopods p. Stratigraphical distribution of Oligocene species, p. 175 Stratigraphical distribution of Miocene species, p. 177 Some 179 general considerations, p. 179 Notes, p. 180 Acknowledgements, p. 180 References, p. 172 Samenvatting miocene in Noordzee- Evolutie en stratigrafische verspreiding van oligocene en Scaphopoda het bekken—een voorlopig rapport. Door middel van een kritische taxonomische herziening van de oligocene en miocene Scapho- het Noordzeebekken werd de toe te poda van mogelijkheid geschapen Scaphopoda passen voor een stratigrafische ouderdomsbepaling. Zowel evolutiereeksen als kenmerkende soortenassociaties kunnen nu voor stratigrafische doeleinden worden gebruikt. Van belang zijn vooral drie ontwikke- nl. Fissidentalium novaki - novaki - lingsreeksen, (Von Koenen) n. subsp. polypleurum Seifert (Latdorf tot Antalis - Goldfuss — - Vierland), n. sp. geminata geminata n. subsp. n. sp. (Rupel tot Vierland) en Fissidentalium - Zimmermann “badense” - n. sp. floratum (= auct.) floratum n. subsp. (Reinbek tot Sylt). vooral verschillende niveau’s Karakteristieke soortengezelschappen zijn kenmerkend voor van Hemmoor-ouderdom. Ook in het komen soortcombinaties die hier echter Rupelien typische voor, andere meer tot bepaalde facies beperkt zijn. Soortenuitwisselingen met Tertiairbekkens hebben alleen tijdens het Hemmoor bestaan met het Burdigalien van de Aquitaine. Directe betrekkingen tot het Mioceen in niet van het Paratethys-gebied zijn, tegenstelling tot bestaande opvattingen, aantoon- Het is dat alle door in 1959 aanzien de baar. gebleken Seifert gemaakte veronderstellingen ten van evolutie der in het soortdeterminaties soorten Noordzeebekken gebaseerd zijn op onjuiste en derhalve niet houdbaar. Zusammenfassung Durch eine kritische taxonomische Revision der Scaphopoden des Oligozäns und Miozäns im Nord- der seebecken wurde die Grundlage geschaffen für die Verwendung von Scaphopoden bei stratigra- phischen Altersbestimmung. Es lassen sich nunmehr sowohl evolutive Reihen als auch charakteristi- sche für die Von Artenvergesellschaftungen Stratigraphie nutzen. Bedeutung sind vor allem drei Ent- Fissidentalium - - wicklungslinien: novaki (von Koenen) novaki n. subsp. polypleurum Seifert (Latdorf- ium bis Antalis - - - Vierlandium), n. sp. geminata Goldfuss geminata n. subsp. n. sp. (Rupelium bis und Fissidentalium - Zimmermann “badense” - Vierlandium) n. sp. floratum (‘ auct.) floratum n. subsp. (Reinbekium bis Syltium). Charakteristische Artenassoziationen kennzeichnen vor allem verschiedene Niveaus innerhalb der Hemmoor-Stufe. Auch in der Rupelstufe gibt es spezielle Artengesellschaften, die hier allerdings mehr anderen auf bestimmte Faziesbereiche beschränkt sind. Beziehungen zu Tertiärbecken bestehen während des Hemmooriums der nur zum Burdigal Aquitaine. Direkte Beziehungen zum Miozän der Paratethys lassen sich entgegen bisherigen Annahmen mit Scaphopoden nicht nachweisen. Es hat sich gezeigt, daß alle von Seifert 1959 vorgestellten Hypothesen über die evolutive Entwicklung der Arten im Nordseebecken auf falschen Artbestimmungen beruhen und somit nicht haltbar sind. Introduction Molluscs have always played an important role in Tertiary research. Especially gastropods and bivalves have attention for of attracted purposes stratigraphy. Contrary to that, however, the 173 have less The for that be scaphopods been more or neglected. reason seems to that scaphopod species usually look quite uniform in shell-form and sculpture, so that species discriminationoften is very dif- tubes which ficult. Moreover, scaphopod are frequently broken, renders species identification even more difficult. It is true that scaphopods of the North Sea Basin have been dealt with in several faunal Koenen Anderson monographs, e.g. Nyst (1845), von (1882, 1892), Speyer (1870), Kautsky (1925), R. A.W. but Seifert deals (1964), Janssen (1978), Janssen (1984), only one paper, (1959), exclusively with scaphopods of the North Sea Basin. In this paper only the species of the Late Oligocene and Miocene were taken into consideration and the taxonomical and nomenclatural results were mainly ideas older Koenen and the based on the of authors such as von (1882) Kautsky (1925). Nevertheless, revision of Seifert still is the only systematic base which has been followed by all later authors. For the first time, Seifert tried to elaborate specific differences by means of statistical methods. the distribution of the known him and their Resting upon stratigraphical species as to according to he scheme of the of that in the morphological similarity proposed a evolutionary development group North Sea Basin. These hypotheses on the evolution of species have been referred to by other authors with from other Goddeeris dealing scaphopods basins, e.g. Caprotti (1979). Later on, (1976, 1978) Miocene but this work continued. So there is started a critical re-evaluation of some species, was not Basin no modern critical and comprehensive revision of Tertiary scaphopods of the North Sea and ad- jacent areas. When well fossil in the ofthe curating Recent as as scaphopod material collections Senckenberg- Museum I realized that number of (Frankfurt am Main) a hitherto generally accepted species iden- tifications (e.g. of Miocene species from Northern Germany with Recent species like D. entalis Linne or with those originally described from the Miocene of the Vienna Basin, like D. badense Homes or mutabile Homes) can no longer be maintained. This led me to start a comprehensive revision of all Oligocene and Miocene scaphopods of the North Sea Basin and adjacent basins (Mayence Basin, Paris the examination of Basin). Especially microsculptural patterns with a Scanning Electron facilitated refined discrimination and of of Microscope (SEM) a species recognition complexes very but is all the and similar, different species. One important result that previous hypotheses on identity evolutionary relationships of species were found to be totally untenable. and The work is based mainly on material from classical outcrops on an evaluation of samples from the borehole Broekhuizenvorst (see van Rooijen et al., 1984). It was possible to establish some well-founded evolutionary lineages which can be used in stratigraphy, as well as some well-defined in in of the species assemblages. However, some details, particularly transitional zones lineages, observations need closer control materialfrom may some stratigraphical by densely sampled borings. Insofar it be that amendmentswill be with may possible some turn out to necessary, especially regard to the exact stratigraphical range of the species. But nevertheless the results presented here allow the of in be it members of in use scaphopods stratigraphy, as evolutionary lineages or form of defined in much better than it has been species assemblages, a way possible up to now. The taxonomical-nomenclatural revision of the scaphopods of the North Sea Basin will be in the future in the "Archiv fur Molluskenkunde". the published near In present paper only the results and concerning stratigraphical, geographical facies-connected distribution, as well as the evolution of the shall be If more important species presented. new species are involved they will be mentioned in avoid the introduction of nomina nuda. As far open nomenclature, just to as necessary for understanding, remarks on some species are given as annotations at the end of this paper. 174 EVOLUTIONARY DEVELOPMENTOF SCAPHOPODS IN THE NORTH SEA BASIN Seifert (1959) listed five species for the Middle and Late Oligocene and ten species for the Miocene. The form which from ribbed species according to Seifert a single evolutionary lineage leads the Rupelian Dentalium kickxii Nyst, via the Late Oligocene D. geminatum Goldfuss, to the Miocene D. badense Homes. From this main stem the line of D. polypleurum Seifert - D. bouei Deshayes splits off the offshoots should Koenen and during Late Oligocene. Miocene be the species D. dollfusi von D. novemcostatum mutabile Homes. Among the unsculptured species the Miocene D. vitreum Gmelin is from the D. Lamarck.