BASTERIA, 66:143-148, 2002 Notes the on systematics, morphology and biostratigraphy of fossil holoplanktonic Mollusca, 12. On the identity ofHyalea perovalis Von Koenen, 1882 (Mollusca, Gastropoda, Euthecosomata) from the Early Miocene of the North Sea Basin Arie+W. Janssen National Museum of Natural History (Palaeontology Department), PO. Box 9517, NL 2300 RA Leiden, The Netherlands; current address: 12, Triq tal'Hamrija, Xewkija VCT 110, Gozo, Malta; ariewe@waldo- net.net.mt. & Karl Gurs Landesamt fiir Natur und Umwelt Schleswig-Holstein, Hamburger Chaussee 25, D-24.220 Flintbek, Germany; [email protected]. New specimens of the extremely rare cavoliniid pteropod ‘Hyalea perovalis’ Von Koenen, 1882, are recorded and illustrated from a boulder ofHolsteiner Gestein (Early Miocene) col- lected at Nehmten, Schleswig-Holstein (Germany). Hyalea perovalis is here considered to be of Diacrolinia which is known from the a juniorsynonym aquensis (Grateloup, 1827), Early Burdigalian of the Aquitaine Basin, France. The occurrence ofthis species in the ‘Holsteiner Gestein’ substantiates previous correlations ofthe Late Vierlandian ofthe regional North Sea Basin stages with the Early Burdigalian of the international chronostratigraphic scheme. Key words: Gastropoda, Euthecosomata, Cavoliniidae, Diacrolinia, Miocene, Burdigalian, North Sea Basin, Aquitaine Basin, lectotype designation. INTRODUCTION In northern Germany sedimentationof marine Miocene starts with the Lower Mica in Clay (of Early Vierlandian age the local chronostratigraphy). This clay hardly yields fossils, from microfossils such Foraminifera. On of this the sediment any apart as top clay fine which in the of the basin contains mollus- suddenly changes to sand, eastern part a fauna which the can in most important pteropod species is Vaginella depressa Daudin, 1800. at the storm-wave-base in and overlain deltaic They generated an open sea are by deposits called 'Untere Braunkohlensande'. The age of this 'Lower Mica Finesand' is indicated as Late Vierlandian. These sands the level of the so-called 'Holsteiner Gestein' undoubtedly are source erratics, found reworked in The boulders small-sized of reddish fluvioglacial deposits. usually are pieces sideritic sandstone of local origin, frequently replete with a diverse array of commonly well-preserved benthic molluscs, as well as various holoplanktonic species. The boundary between mica clay and fine sands, however, is diachronous, which that to the West it becomes and is of Hemmoorian means more younger ultimately age. 1 For No. 11 in this series see basteria 65: 147-149, 2001 144 BASTERIA, Vol. 66, No. 4-6, 2002 Fig. 1. Slab of Holsteiner Gestein from Nehmten (Germany, Schleswig-Holstein), showing benthic mollus- remains two of the Von 1882’ The left hand can and specimens pteropod ‘Hyalea perovalis Koenen, (arrows). is in in 4. 1 specimen illustrated fig. 3, the right hand one fig. Scale bar cm. Borehole samples and erratics (so-called 'Vaginellen-Kalksandstein') from this level con Kittl, tain many specimens of the pteropod Vaginella austriaca 1886. The assemblage of the Holsteiner Gestein, which contains benthic molluscs such as Yoldia Yoldiella Leionucula laevigata (Sowerby, 1818), glaberrima (Miinster, 1835), pygmaea Haustator helicina (Munster, 1835), Spisula sp., goettentrupensis (Cossmann, 1899), Euspira (Brocchi, 1814), Sassia enodis (Beyrich, 1856),.Nassarius schlotheimi(Beyrich, 1854), Mitrella attenuata (Beyrich, 1854) and Fusiturris duchastelii (Nyst, 1845), as well as the pteropod dated 'Late Vaginella depressa Daudin, 1800, is unequivocally as Early Miocene, or Vierlandian'in the local chronostratigraphic scheme. A. In his well-known paper on North German Miocenemolluscan faunas von Koenen (1882) included descriptions of several pteropod species from reworked boulders of introduced 'Holsteiner Gestein'. One of the pteropod taxa as a new species was named Hyalea perovalis by Von Koenen (1882), and is usually indicated by subsequent authors as Cavolinia perovalis. Von Koenen had three specimens available, all from Stolpe (Germany, of which illustrated 1882: 7 15a- Schleswig-Holstein), one was (Von Koenen, 354, pi. fig. Janssen & Giirs: Hyalea perovalis ofthe MioceneNorth Sea Basin 145 ofa small This has remained c) by means drawing. an enigmatic species ever since, as the type material is missing. The first author, at various occasions, has attempted to trace Von Koenen's specimens in public collections at Hamburg, Berlin and Gottingen, but without be considered lost. The any success. They must species is extremely rare. As far as we know, not a single specimen has been collected ever since the original description, despite detailedinspection of numerous slabs of Holsteiner Gestein from various locali- ties in Schleswig-Holstein. Fig. 2. Von Koenen’s (1882) illustration of Hyalea perovalis, from Stolpe (Miocene, Vierlandian, Holsteiner Gestein), herein designatedlectotype. NEW MATERIAL In April 2002 the second author visited the so-called 'Eiszeitmuseum' at Stolpe and had a look at the fossil sale there. To his there small of samples on great surprise was a piece Holsteiner Gestein from named a locality Nehmten, just 12 km SE of Stolpe, that, contain although not very attractive at first sight, proved to two specimens of Von Koenen's Of he Hyalea perovalis! course immediately purchased the specimen (price was € 1.40) and subsequently sent it to the first author. Apart from benthic molluscan the slab contains ofthe remains, numerous specimens pteropod Vaginella depressa, as well shell of as a single Limacina miorostralis (Kautsky, 1925). Fig. 1 is an overall view of the boulder. The left hand in which in dorsal specimen (arrows) fig. 1, was preserved aspect, was isolatedfrom the with slab, some fragments of the ventral side left sticking to the matrix, but these could be glued back again. A small portion of the lower ventral side appeared be The second to missing (fig. 3a-c). specimen was carefully freed from the adhering sedi- ment, to reveal the ventral side in its entirety, and left in place (fig. 4). Both lack their but specimens unfortunately protoconch, the central radial riblet pre- the base sent at of the dorsal shell part, as well as the dorsally curved lateral slits, clearly indicate that the they belong in recently introduced genus Diacrolinia (compare Janssen, On the basis 1995: 110). of these new specimens it is obvious that Von Koenen's illustra- tion the (here reproduced as fig. 2) represents species very well. 146 BASTERIA, Vol. 66, No. 4-6, 2002 3. Diacrolinia from boulder Fig. aquensis (Grateloup, 1827). First of two specimens a of Holsteiner Gestein, originating from Nehmten (Germany, Schleswig-Holstein). Purchased from the Eiszeitmuseum, Stolpe 1 (Germany); don. Karl Gürs (RGM 458.705). a, dorsal;b, left lateral; c, ventral view. Scale bar mm. RELATED SPECIES FROM THE MIOCENE OF AQUITAINE (FRANCE) With regard to the correct name of this interesting fossil there are some taxonomical problems ofrelated species to be considered. Prior to Von Koenen's description in 1882 related two closely species, Diacroliniaorbignyi (Rang, 1827) (described as Hyalea Orbignii by Rang [1827: 383], emended by d'Orbigny [1836: 99, footnote 2]) and D. aquensis (Grateloup, 1827) (described as Hyalaea Aquensis by Grateloup [1827: 4]) were described from the Aquitaine Basin. Both species are extremely rare, because oftheir fragility, and the known from few A at time were very specimens only. paper on the Oligocene and Miocene holoplanktonic molluscs of the Aquitaine Basin is in preparation (Janssen, in prep.). In anticipation of the detailed discussion therein, a few notes will suffice here. Most authors considered Diacrolinia and D. It early orbignyi aquensis synonyms. was Peyrot (1932: 20) who expressed doubts about the conspecificity, although he only had material of D. before the otherwise. aquensis him, relying on original publications A study of additional material of both species clearly shows that Peyrot was right. the differences substantial: Diacrolinia the dorsal shell Indeed, are quite in orbignyi part has, next to the central radial rib, two weaker such ribs on each side. In D. aquensis only the much weaker radial riblet the basal of the dorsal side. Another is present in part important characteristic is found in the dorsal apertural margin, which in D. orbignyi is reinforced closed tubular of the similar by a completely backfolding margin, very to those found in species of Diacria, whereas in Diacrolinia aquensis the dorsal edge is rein- forced a fold, to the by simple parallel margin So Diacrolinia known from the Cabanes far, orbignyi is exclusively Moulin de outcrop at St. mentioned 'St. Paul-de-Dax' Paul-les-Dax, which, although not by name (just was given) presumably is also its type locality. D. aquensis was describedfrom another outcrop (Mandillot), also in St. Paul-les-Dax, but has now also been collected from a few localities situated more northerly in the Aquitaine Basin (Saucats: Moulin de l'Eglise, Peloua, Giraudeau, Coquillere, Pont Porquey; Leognan: Moulin Daney) (part of these localities Janssen & Gtirs: Hyalea perovalis ofthe MioceneNorth Sea Basin 147 after Dr Bruno Cahuzac Peyrot, 1932). (Talence, France) kindly inform us that the Cabanes is older than Mandillot, both of locality slightly being Early Burdigalian age, as indicatedby the Miogypsina- assemblages (Cahuzac, 1984). Van der Spoel (1967: 85) erroneously applied the epithet orbignyi (ms Rang) (Souleyet, form of 1852) to a