Notes on the systematics, morphology and biostratigraphy of fossil holoplanktonic Mollusca, 12. On the identity of Hyalea perovalis Von Koenen, 1882 (Mollusca, Gastropoda, Euthecosomata) from the Early Miocene of the North Sea Basin

6 Pages·2002·1 MB·English

by  Janssen, Arie W

BASTERIA, 66:143-148,2002
Notesonthesystematics, morphology andbiostratigraphy offossil holoplanktonic
Mollusca, 12. On theidentity ofHyalea perovalis VonKoenen, 1882
(Mollusca, Gastropoda, Euthecosomata)
fromthe EarlyMioceneoftheNorthSeaBasin
Arie+W.Janssen
National Museum ofNaturalHistory (PalaeontologyDepartment),PO.Box9517, NL 2300RALeiden,
TheNetherlands;current address: 12,Triq tal'Hamrija,XewkijaVCT 110,Gozo, Malta;ariewe@waldo-
net.net.mt.
& KarlGurs
Landesamt fiir Natur und Umwelt Schleswig-Holstein, HamburgerChaussee 25,D-24.220Flintbek,
Germany;[email protected].
New specimens ofthe extremely rare cavoliniid pteropod ‘Hyaleaperovalis’ Von Koenen,
1882,arerecorded and illustrated fromaboulder ofHolsteiner Gestein (EarlyMiocene)col-
lected atNehmten,Schleswig-Holstein(Germany).Hyaleaperovalisis here considered tobe
ajuniorsynonym ofDiacrolinia aquensis(Grateloup, 1827),which isknown from the Early
BurdigalianoftheAquitaineBasin,France.The occurrenceofthis speciesinthe ‘Holsteiner
Gestein’ substantiatesprevious correlationsofthe LateVierlandian oftheregionalNorth Sea
Basin stageswiththeEarlyBurdigalianoftheinternationalchronostratigraphicscheme.
Key words: Gastropoda, Euthecosomata,Cavoliniidae,Diacrolinia,Miocene,Burdigalian,
North SeaBasin,AquitaineBasin,lectotype designation.
INTRODUCTION
InnorthernGermany sedimentationofmarine Miocene starts with the LowerMica
Clay (ofEarly Vierlandianage in the local chronostratigraphy). This clay hardly yields
any fossils,apartfrommicrofossils suchas Foraminifera.On topofthisclay thesediment
suddenly changes to finesand,whichin theeastern part ofthe basin containsamollus-
can faunain which the most important pteropod species is Vaginella depressa Daudin,
1800.They generated atthestorm-wave-base in anopenseaandareoverlainby deltaic
deposits called'Untere Braunkohlensande'.
Theage ofthis 'LowerMica Finesand'is indicatedas LateVierlandian.Thesesands
undoubtedly are the source level ofthe so-called 'Holsteiner Gestein' erratics, found
reworkedin fluvioglacial deposits. Thebouldersusually aresmall-sizedpieces ofreddish
sideritic sandstoneoflocalorigin, frequently replete witha diverse arrayof commonly
well-preserved benthic molluscs, as wellas various holoplanktonic species.
The boundary between mica clay and fine sands, however, is diachronous, which
meansthatmoreto theWestitbecomes youngerand ultimatelyisof Hemmoorianage.
1 ForNo. 11inthisseriesseebasteria65: 147-149, 2001
144 BASTERIA, Vol. 66,No.4-6, 2002
Fig. 1.Slab ofHolsteiner Gestein from Nehmten(Germany, Schleswig-Holstein), showingbenthic mollus-
canremains andtwo specimensofthepteropod ‘HyaleaperovalisVon Koenen,1882’ (arrows).The left hand
specimenis illustratedin fig.3,the righthand oneinfig.4.Scalebar 1cm.
Boreholesamples anderratics (so-called 'Vaginellen-Kalksandstein') fromthis levelcon
tainmanyspecimens ofthepteropod Vaginella austriacaKittl, 1886.
The assemblage ofthe HolsteinerGestein, which containsbenthic molluscs such as
Leionucula laevigata (Sowerby, 1818), Yoldia glaberrima (Miinster, 1835), Yoldiellapygmaea
(Munster, 1835),Spisula sp.,Haustator goettentrupensis (Cossmann, 1899),Euspira helicina
(Brocchi, 1814),Sassiaenodis(Beyrich, 1856),.Nassarius schlotheimi(Beyrich, 1854),Mitrella
attenuata (Beyrich, 1854) and Fusiturris duchastelii(Nyst, 1845), as well as the pteropod
Vaginella depressa Daudin, 1800, is unequivocally dated as Early Miocene, or 'Late
Vierlandian'inthe localchronostratigraphic scheme.
Inhiswell-knownpaperonNorthGerman MiocenemolluscanfaunasA. vonKoenen
(1882) included descriptions of several pteropod species from reworked boulders of
'HolsteinerGestein'. Oneof the pteropod taxa introduced as anew species was named
HyaleaperovalisbyVonKoenen(1882), andis usuallyindicatedbysubsequent authorsas
Cavoliniaperovalis.VonKoenenhadthree specimens available,allfromStolpe (Germany,
Schleswig-Holstein), oneofwhich was illustrated(Von Koenen, 1882:354, pi. 7 fig. 15a-
Janssen &Giirs:Hyalea perovalis oftheMioceneNorthSeaBasin 145
c)by means ofasmalldrawing.Thishasremainedanenigmatic species ever since,as the
type materialis missing. The firstauthor, at variousoccasions, has attempted to trace
Von Koenen's specimens in public collections at Hamburg, Berlinand Gottingen, but
withoutany success. Theymustbe consideredlost.Thespecies is extremely rare.As far
aswe know, notasingle specimen hasbeencollectedeversincetheoriginal description,
despite detailedinspection ofnumerous slabsofHolsteiner Gesteinfromvariouslocali-
tiesin Schleswig-Holstein.
Fig.2. Von Koenen’s (1882)illustration ofHyaleaperovalis, fromStolpe (Miocene, Vierlandian,Holsteiner
Gestein),hereindesignatedlectotype.
NEW MATERIAL
InApril2002thesecondauthorvisitedtheso-called'Eiszeitmuseum'atStolpe andhad
alookatthefossil samples onsalethere. Tohis greatsurprise therewas asmallpiece of
Holsteiner Gestein from a locality named Nehmten, just 12 km SE of Stolpe, that,
although not very attractive at first sight, proved to contain two specimens of Von
Koenen'sHyaleaperovalis! Ofcourse he immediately purchased the specimen (price was
€ 1.40) and subsequently sent it to the first author. Apart from benthic molluscan
remains,theslabcontainsnumerous specimens ofthepteropod Vaginella depressa, aswell
as asingle shell ofLimacina miorostralis(Kautsky, 1925). Fig. 1is an overallview ofthe
boulder.
Thelefthand specimen (arrows) in fig. 1, whichwas preserved in dorsalaspect, was
isolatedfromtheslab, with somefragments oftheventralsideleftstickingto thematrix,
but thesecouldbe gluedback again. Asmallportion ofthe lowerventralside appeared
tobe missing(fig. 3a-c). Thesecondspecimen wascarefully freedfromtheadhering sedi-
ment,torevealthe ventralsideinitsentirety,andleftin place (fig. 4).
Both specimens unfortunately lack theirprotoconch, but the centralradialribletpre-
sent atthebaseofthedorsalshellpart, aswellas the dorsally curvedlateralslits,clearly
indicatethatthey belong intherecently introducedgenusDiacrolinia(compare Janssen,
1995: 110).On thebasis of thesenewspecimens itis obviousthatVon Koenen'sillustra-
tion(here reproduced asfig. 2) representsthe species very well.
146 BASTERIA, Vol. 66,No. 4-6,2002
Fig. 3. Diacrolinia aquensis(Grateloup, 1827).First oftwospecimens froma boulderofHolsteiner Gestein,
originatingfrom Nehmten (Germany, Schleswig-Holstein). Purchased from the Eiszeitmuseum,Stolpe
(Germany);don.Karl Gürs (RGM458.705).a, dorsal;b, leftlateral;c,ventralview. Scalebar 1mm.
RELATEDSPECIESFROM THE MIOCENE OF AQUITAINE (FRANCE)
Withregard to the correct name ofthis interesting fossiltherearesome taxonomical
problems ofrelated species to be considered.Priorto VonKoenen's description in 1882
two closely related species, Diacroliniaorbignyi (Rang, 1827)(described asHyalea 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
fromthe Aquitaine Basin.Bothspecies areextremely rare, becauseoftheirfragility,and
at the timewere known from very fewspecimens only. Apaper onthe Oligocene and
Miocene holoplanktonic molluscs ofthe Aquitaine Basin is in preparation (Janssen, in
prep.). Inanticipation ofthe detaileddiscussiontherein,afewnotes willsuffice here.
Most early authors consideredDiacroliniaorbignyi and D. aquensis synonyms. Itwas
Peyrot (1932: 20) who expressed doubtsabout the conspecificity, although he only had
materialofD. aquensis beforehim,relyingontheoriginal publications otherwise.
A study ofadditional materialofboth species clearly shows that Peyrot was right.
Indeed, the differencesare quite substantial:in Diacroliniaorbignyi the dorsalshell part
has, nexttothe centralradialrib, two weakersuchribs oneach side.In D.aquensis only
the much weakerradialriblet is present inthe basal part ofthe dorsal side. Another
important characteristicis foundin the dorsal apertural margin, whichinD. orbignyi is
reinforced by a completely closed tubular backfolding ofthe margin, very similar to
those foundin species ofDiacria, whereasinDiacroliniaaquensis thedorsal edge isrein-
forcedby asimple fold,parallelto the margin
Sofar, Diacroliniaorbignyiisknownexclusively fromtheMoulinde Cabanesoutcropat
St. Paul-les-Dax, which, although not mentionedby name (just 'St. Paul-de-Dax' was
given) presumably isalsoitstypelocality. D.aquensis was describedfromanotheroutcrop
(Mandillot), alsoin St.Paul-les-Dax, buthasnowalsobeencollectedfromafewlocalities
situated more northerly in the Aquitaine Basin (Saucats: Moulin de l'Eglise, Peloua,
Giraudeau,Coquillere, Pont Porquey; Leognan: MoulinDaney) (part ofthese localities
Janssen &Gtirs: Hyalea perovalis oftheMioceneNorthSeaBasin 147
after Peyrot, 1932). Dr Bruno Cahuzac (Talence, France) kindly inform us that the
Cabaneslocality is slightly olderthanMandillot,both being ofEarly Burdigalian age,as
indicatedby theMiogypsina-assemblages (Cahuzac, 1984).
VanderSpoel (1967: 85) erroneously applied theepithet orbignyi (ms Rang) (Souleyet,
1852)to aformoftheRecentDiacria quadridentata (Blainville, 1821). Lateron(1973: 21)
hecorrectedhisinterpretation oftheepithet orbignyi, statingthathe hadmisinterpreted
Souleyet (1852). Inthis paper he provided anillustrationof the holotype of Cavolinia
orbignyi, atthattimehousedin theMuseumnationald'Histoirenaturelle(Paris,France).
Thisclearly showsthepresenceofradialornamentonthedorsalshellpart, as wellasthe
thickeneddorsal apertural margin. Unfortunately, however,the holotype seems tohave
disappeared from the Paris collections since.The same, by the way, holds true for D.
aquensis, the type of which used to be housed in the collections of the Faculte des
Sciences, Bordeaux(France).
Fig. 4.Diacrolinia aquensis(Grateloup, 1827).Second oftwospecimensinaboulderofHolsteinerGestein,
originatingfrom Nehmten (Germany, Schleswig-Holstein). Purchased from the Eiszeitmuseum,Stolpe
(Germany); don. Karl Gürs (Colln Landesamt für Natur und Umwelt Schleswig-Holstein, Flintbek,
Germany).Ventral view.Scale bar1mm.
CONCLUSIONS
In conclusionweidentify thetwo specimens of HyaleaperovalisVonKoenen, 1882,as
Diacroliniaaquensis (Grateloup, 1827),considering H. perovalis ajunior synonym.
Van der Spoel (1973: 23) synonymised H. perovalis with ‘Cavolinia’orbignyi (Rang,
1827), whichis wrong.
In the absence ofall syntypes, and because of the confusion with Diacroliniaorbignyi,
wethinkalectotype is necessary here.As Von Koenen'sillustrationwas foundto repre-
sent the species correctly weherewith,in accordancewith art. 74.4ICZN, designate the
specimen illustratedby VonKoenen(1882: pi. 7 fig. 15)lectotype ofHyaleaperovalis.
Theoccurrence ofDiacroliniaaquensis intheNorthSea Basin"HolsteinerGestein"cor-
roboratesprevious correlationofthe LateVierlandian(regional NorthSeaBasinstages)
withthe Early Burdigalian as statedbyJanssen (2001: 49, fig. 1).
ACKNOWLEDGEMENTS
We thank Dr. Bruno Cahuzac (Laboratoire de Recherches et Applications
Geologiques, Universite Bordeaux-I, Talence, France) for stratigraphical information
148 BASTERIA, Vol. 66,No. 4-6,2002
and foraccess to collections in his care. Dr. John W. M. Jagt (Venlo, the Netherlands)
improved the English.
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