65Bollettino della Società Paleontologica Italiana, 49 (1), 2010, 65-74. Modena, 15 maggio 2010

ISSN 0375-7633

INTRODUCTION

In recent years there has been an increase insystematic studies of Silurian nautiloid cephalopods froma variety of geographical settings and the observedtemporal and spatial data from these faunas may now beconsidered a reliable tool for paleobiogeographicreconstruction and tracing of migrational pathways ofpelagic organisms. Concentrated efforts have been madeto improve the knowledge of the distribution andtaxonomy of Silurian nautiloid cephalopod faunas andmany existing collections have been revised using up todate taxonomic criteria as well as collection of newmaterial from horizons with precise biostratigraphic data.In Europe the main work has been done in the British Isles(Evans, 1994; Evans & Holland, 1995; Holland, 1998,1999, 2000a, 2000b, 2000c, 2002, 2003, 2004, 2007;Holland & Stridsberg, 2004), Sweden (Stridsberg, 1985),

Prague Basin (Marek, 1971; Kolebaba, 1975, 1977,1999, 2002; Turek, 1975; Marek & Turek, 1986; Manda,1996, 2008; Gnoli, 1997; Stridsberg & Turek, 1997;Manda & Kriz, 2006, 2007; Manda & Turek, 2009a,2009b, 2009c), South West Sardinia (Gnoli & Serpagli,1977, 1991; Serpagli & Gnoli, 1977; Gnoli, 1990; Gnoli& Serventi, 2006, 2009 and references therein), Spain(Bogolepova, 1998b), France (Ristedt, 1968; Serventi &Feist, 2009) and the Carnic Alps (Ristedt, 1968; Histon,1997, 1998, 1999a, 1999b, 2002; Bogolepova, 1998a;Gnoli & Histon, 1998; Gnoli et al., 2000; Serventi &Gnoli, 2001; Serventi et al., 2006, 2010; Gnoli &Serventi, 2008). Tentative correlations are now possiblebetween Avalonia (British faunas) and North Gondwana(Carnic Alps, Sardinia, France and Spain) and Bohemiaand Baltica, although problems still exist in recognitionof faunas at both generic and specific level due to poorpreservation and lack of precise taxonomic diagnoses.

A preliminary study of the upper Silurian nautiloid cephalopodsfrom the Eggenfeld section (Graz Paleozoic, Austria)

Kathleen HISTON, Bernhard HUBMANN & Fritz MESSNER

K. Histon, Dipartimento di Scienze della Terra, Università degli Studi di Modena e Reggio Emilia, Largo S. Eufemia 19, 41121 Modena (Italy);hiscat@interfree.it, catherine.histon@unimore.it

B. Hubmann, Institute for Earth Sciences (Geology & Palaeontology), University of Graz, Heinrichstrasse 26, A-8010 Graz (Austria);bernhard.hubmann@uni-graz.at

F. Messner, Auenbruggergasse 8, A-8073 Feldkirchen bei Graz (Austria); friedrich.messner@buehnen-graz.com

KEY WORDS - Nautiloid cephalopods, upper Silurian, Austria, paleobiogeography, biostratigraphy.

ABSTRACT - The preliminary results of a systematic investigation of the nautiloid faunas from the upper Silurian (Pridoli) Eggenfeldsection of the Graz Paleozoic are presented. A faunal list of the seven genera recognized to date, representing the families Oonoceratidae andLechritrochoceratidae and subfamilies Michelinoceratinae, Kionoceratinae, Leurocycloceratinae is given and selected taxa illustrated. Thesegenera document faunal exchange between the Graz Paleozoic, central Bohemia, the Carnic Alps, Sardinia, France (Montagne Noire), Spain(the Ossa Morena Zone) and Morocco during the late Silurian. The study adds a further contribution to the ongoing systematic description bydiverse research groups of Silurian nautiloid cephalopods from the North Gondwana sector within a well defined biostratigraphic frameworkin order to elaborate their use as a tool for biostratigraphic correlation and paleobiogeographic reconstructions.

RIASSUNTO - [Studio preliminare dei cefalopodi nautiloidi del Siluriano superiore (Pridoli) della sezione di Eggenfeld (Paleozoico di Graz,Austria)] - Sono presentati i risultati preliminari di uno studio sistematico delle faune a nautiloidi del Siluriano superiore (Pridoli) provenientidalla sezione di Eggenfeld nel Paleozoico di Graz. Il Paleozoico di Graz si trova nell’Austria orientale, ha un estensione geografica di circa1250 km2 ed è suddiviso in tre gruppi di falde sulla base delle litologie, della posizione tettonica e della sovrapposizione metamorfica dellesuccessioni: un gruppo basale, uno intermedio e uno superiore. Le faune a nautiloidi provengono dal gruppo di falde superiore - “Rannach-Hochlantsch Nappe” - di età compresa tra il Siluriano superiore e il Carbonifero Superiore. Le sequenze stratigrafiche indicano una varietà diambienti di deposizione da un margine continentale passivo con vulcanismo intra-placca a sedimenti tipici di scogliere e piattaforme marinedurante il Siluriano e Devoniano. La sezione di Eggenfeld fa parte dell’Eggenfeld Member della Kötschberg Fm. (Ludfordiano-Lochkoviano).I livelli K1, K2 and K3 sono dolomie grigio scure o dolomie localmente ricche di fossili. Le faune a conodonti indicano un’età compresa trala biozona a P. siluricus (Ludlow superiore) e la biozona a I. woschmidti (Lochkoviano).

Nonostante la fauna a nautiloidi presente sia risultata piuttosto ricca, questo lavoro rappresenta il primo studio sistematico effettuato nelPaleozoico di Graz. Viene presentato un primo elenco di sette generi appartenenti alle famiglie Oonoceratidae e Lechritrochoceratidae e allesottofamiglie Michelinoceratinae, Kionoceratinae, Leurocycloceratinae. Vengono figurate sette specie, lasciate in nomenclatura aperta,appartenenti ai generi Michelinoceras Foreste, 1932, Merocycloceras Ristedt, 1968, Plagiostomoceras Teichert & Glenister, 1952, ParakionocerasFoerste, 1928, Orthocycloceras Barskov, 1972, Oonoceras Hyatt, 1884, e Lechritrochoceras Foreste, 1926.

La segnalazione di questi generi nel Paleozoico di Graz, presenti anche in Boemia centrale, Alpi Carniche, Sardegna, Francia (MontagnaNera), Spagna (Ossa Morena) e Marocco (Tafilalt, Anti-Atlas) documenta l’interscambio faunistico dei nautiloidi durante il tardo Siluriano.

Lo studio fornisce inoltre dati importanti per le descrizioni tassonomiche in fase di elaborazione da parte di diversi gruppi di ricerca sullefaune a nautiloidi raccolte in biozone (a conodonti e graptoliti) ben stabilite del Siluriano per tutta la fascia settentrionale del Nord Gondwana,con lo scopo di evidenziare la loro distribuzione paleobiogeografica e di scoprire la possibilità di applicare i dati ricavati, sia per le ricostruzionipaleobiogeografiche sia per le correlazioni biostratigrafiche.

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Detailed study of Silurian-Devonian nautiloid faunas fromMorocco (Kröger, 2008) presented together with precisestratigraphic and lithofacies data for the collectionlocalities has highlighted further that correlation isfeasible between the Peri-Gondwana Terranes and thatnautiloid cephalopods are reliable paleobiogeographicindicators.

This is the first detailed systematic study of thenautiloid fauna from the upper Silurian sections of theGraz Paleozoic area to be carried out even thoughnautiloids are to be found in abundance there (Ebner,1976a; Hiden, 1995). It is hoped that the results of thesystematic investigation in progress will be of importancefor placing the nautiloid faunas from the Graz Silurianwithin a global scenario both with regard to theimplications from the faunal assemblage present forpaleobiographical reconstruction and patterns of faunalexchange along the North Gondwana margin but also withregard to their paleoecological and paleoenvironmentalsettings which in some ways are similar to those in someareas of the Prague Basin (Manda & Kriz, 2006).

GEOLOGICAL SETTING

The Graz Paleozoic located in eastern Austria (Fig.1) extends over approximately 1250 km2 and is isolatedfrom other low metamorphic Paleozoic occurrences bytectonic borders to the north, east and west as well as byits younger overlays in the south (Fig. 2). Thenorthwestern and western parts of the Graz Paleozoic arebordered by polycrystalline units of the AustroalpineCrystalline Zone, whereas in the south, Paleozoicsuccessions are transgressively overlain by Neogenesediments of the “Styrian Basin”. The southwestern partsare unconformably covered by Upper Cretaceoussediments of the Kainach Gosau.

The Graz Paleozoic is divided into a basal, anintermediate and an upper nappe group (Fritz & Neubauer,1990) based on lithological similarities, the tectonicposition as well as the metamorphic superimposition ofsuccessions.

- The Basal Nappe System (“Schöckl-Hochschlag Nappe”;upper Silurian to Middle Devonian) was deformed underupper greenschist facies conditions. Volcaniclasticsdominate the late Silurian to Early Devonian interval,and carbonates the Middle Devonian time span.

- The Intermediate Nappe System (“Laufnitzdorf Nappeand Kalkschiefer Nappes”; lower Silurian to UpperDevonian) contains pelagic limestones, shales,volcaniclastics as well as siliciclastics.

- The Upper Nappe System (“Rannach-HochlantschNappe”; upper Silurian to Upper Carboniferous) ischaracterised by Lower to Middle Devonianvolcaniclastic rocks, Lower to Middle Devoniansiliciclastics and fossil-rich carbonates of near-shoreenvironment followed by the pelagic sequences of lateGivetian to Bashkirian age with shallow marinesediments at the top.

The stratigraphic sequence indicates a sedimentationarea changing from a passive continental margin withintraplate volcanism to shelf and platform geometriesduring Silurian to Devonian time (Fritz et al., 1992).During Pragian to Givetian time deposition changed fromnear-shore facies to open platform environments, duringthe Frasnian the carbonate platform was drowned andlimestones were deposited. The “Variscan event” isindicated by mixed conodont faunas, stratigraphic gapsand karstification (Ebner, 1976b).

STRATIGRAPHY AND ENVIRONMENTALARCHITECTURE OF THE RANNACH NAPPE

(UPPER NAPPE GROUP)

Volcaniclastics characterise the basal parts of allnappe groups of the Graz Paleozoic. The sequence of the

Fig. 1 - Location map of the Graz Paleozoic and other remnants ofPaleozoic strata in Austria (Greywacke Zone, South Burgenland,Gurktal Nappe, Nötsch, the Carnic Alps, the Karawanken Mountains).The Periadriatic Line separates the Carnic Alps and the KarawankenMountains (Southern Alps) from the Eastern Alps.

Fig. 2 - Simplified sketch of the Graz Paleozoic. Shaded patchescorrespond with outcropping area of the Rannach Nappe (UpperNappe Group). Eggenfeld locality marked with arrow.

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Rannach Nappe starts with predominantly alkalinesubordinately acidic metavolcanites (tuffs, lavas) of theKehr Fm. (Fig. 3). A single finding of the graptoliteBohemograptus bohemicus tenuis (Boucek, 1936)within a tuffitic layer at the very top of the formationindicates an age not younger than Ludfordian(Neocucullograptus kozlowskii graptolite Biozone). Thefollowing Kötschberg Fm. comprises predominantlydolostones, argillaceous shales and silty shales of Ludlowto Lochkovian age (Ebner, 1976a; Hiden, 1995).Following the basal sequences dominated byvolcaniclastics to fine-grained clastics sedimentationchanges to platy crinoidal limestones intercalated withsandy marls and sand/siltstones of the Pragian ageParmasegg Fm. (Fritz, 1991). During Emsian times theperitidal Flösserkogel Fm. with monotonous light greylate diagenetic dolostones, reddish-purple to greenvolcaniclastics, pure quartz sandstones, marly dolomitesand biolaminated dolomites of varying colours wasformed (Fenninger & Holzer, 1978).

A sea level rise resulted in the deposition of highlyfossiliferous dark marly bioclastic limestones with reefalstructures (coral-stromatoporoid-carpets), the EifelianPlabutsch Fm. (Hubmann, 1993, 2003). This phase isterminated by a repetition of tidal flat deposits similar tothe Flösserkogel Fm. and obviously caused by an eustaticsea level fall.

During the Givetian renewed transgression resultedin sequences with sharp (bio)facial contrasts between

patch-reefs and monotonous mudstones (KollerkogelFm., Tyrnaueralm Fm., and Zachenspitz Fm.). During theuppermost Givetian to lower Frasnian the sedimentationof shallow platform carbonates was replaced by micriticcephalopod limestones (Steinberg Fm.). Thissedimentation continued up to the Bashkirian(Sanzenkogel Fm., Forstkogel Group) with someinterruptions caused by uplifting during the Variscancollision (Ebner, 1976b, 1978). Finally the sequence isterminated by shallow marine shales and limestones withbirdseye structures (Hahngraben Fm.) (Hubmann &Messner, 2007).

THE EGGENFELD SECTION

The Eggenfeld section belongs to the EggenfeldMember (Flügel, 2000) of the Kötschberg Fm.(Ludfordian - Lochkovian). The Silurian succession ofthe section (Fig. 4) at Eggenberg (hill north of the villageof Eggenfeld) consists of greenish, massive diabase (V)at the base, which is followed by approximately a 2 m

Fig. 3 - Stratigraphic column of the Rannach Nappe. 1) Kehr Fm.,Kötschberg Fm.; 2) Parmasegg Fm.; 3) Flösserkogel Fm., BamederFm.; 4) Plabutsch Fm.; 5) Kollerkogel Fm.; 6) Steinberg Fm.; 7)Sanzenkogel Fm.; 8) Höchkogel Fm.; 9) Hahngraben Fm.

Fig. 4 - Stratigraphy of the Eggenfeld Section. The haematite layer(R) separates rocks of the Kehr Fm. (below) from the KötschbergFm. (above). V: diabase and tuffs; K: carbonates; S: tuffaceousschists; D: dolomite.

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thickness of violet and greenish-grey unlayered tuffs, aswell as thin bedded ash tuffs (Ebner, 1976a). Someconcretionary horizons with haematite occur. Amoderately well preserved specimen of Bohemograptusbohemicus tenuis was recorded (Hiden, 1995) from oneof the ash tuff horizons. Above the volcaniclastic horizonwhich marks the boundary between the Kehr Fm. and theoverlying Kötschberg Fm. (Eggenfeld Member) a layerof haematite (R) is developed at the contact between thediabase and dolomite. This haematite level passes into a1 m thick succession of bedded dark grey dolostoneswhich is overlain by fossil free tuffaceous schists andclaystones (S

1). Carbonate rocks K1, K2 and K3 of the

section are dark grey, bedded dolomites and/or dolomiticlimestones that are locally rich in fossils. They can bedifferentiated on the basis of their microfacies into:bioclastic dolosparites to biodolosparites,biodolosparites and biomicrites (microsparites). Thebioclastic content (mainly crinoids, orthocerids,brachiopods, rare solitary rugose corals) is subject tostrong fluctuations, however, generally amounts are upto 15%. The fossil content of the biodolosparites likewisereaches 15% but comprises exclusively crinoidalremains. Biomicrites contain up to 20% shell fragments,brachiopods, crinoids, trilobites and subordinateorthoconic nautiloids. The brachiopods are mostlypreserved with both valves. The occurrence of

macrofossils varies throughout the carbonate horizons(Ebner, 1976a):

K1 - crinoids, orthocerids (Kionoceras cf. bronni,Cyrtocycloceras cf. urbanum, Oonoceras? sp.), smallsized undeterminable brachiopods, Cardiolinka sp.,gastropods, Favosites sp.

K2 - crinoids, orthocerids, Septatrypa subsecreta,Syringaxon frame.

K3 - crinoids, orthocerids, Septatrypa subsecreta,frequent loboliths of Scyphocrinites (Ø about 10 cm)occur. Brachiopods appear as pavements (Hubmann &Suttner, 2007).

Preservation of conodonts is excellent within thedolomites (see Ebner, 1976a) and these indicate a rangefrom the P. siluricus conodont Zone (upper Ludlow) tothe I. woschmidti conodont Zone (Lochkovian).

NAUTILOID FAUNAS

The collection of nautiloid fauna being studied ishoused at the University of Graz under the accessionnumber series E.I-001-399. The material which to dateincludes over 400 specimens, was collected from the K

2horizon at the Eggenfeld section locality and is beingprepared and photographed at the University of Graz. Thespecimens have to date been divided into 16 distinct taxa

EXPLANATION OF PLATE 1

Fig. 1 - Plagiostomoceras sp. Coll. n. E.I–329, external view of the specimen, showing fine, transverse ornament, Pridoli, level K2,Eggenfeld section (Graz Paleozoic), scale bar 1cm.

Figs. 2, 9 - Lechritrochoceras sp.2 - Coll. n. E.I–109, external view of the specimen, showing transverse ornament, prominent annulations and deep hyponomic

sinus, Pridoli, level K2, Eggenfeld section (Graz Paleozoic), scale bar 1 cm.9 - Coll. n. E.I–077, external view of the specimen, showing fine, transverse and longitudinal ornament and oblique annulations,

Pridoli, level K2, Eggenfeld section (Graz Paleozoic), scale bar 1 cm.

Figs. 3, 10 - Parakionoceras sp.3 - Coll. n. E.I–311, external view of the specimen, showing longitudinal ornament, Pridoli, level K2, Eggenfeld section (Graz

Paleozoic), scale bar 1 cm.10 -Coll. n. E.I–122, external view of the specimen, showing longitudinal ornament, Pridoli, level K2, Eggenfeld section (Graz

Paleozoic), scale bar 1 cm.

Fig. 4 - Merocycloceras sp. Coll. n. E.I–001, external view of the specimen, showing slightly raised, transverse ornament, Pridoli, levelK2, Eggenfeld section (Graz Paleozoic), scale bar 1 cm.

Figs. 5-7 - Michelinoceras sp.5 - Coll. n. E.I–020, external view of the specimen, showing slender longiconic form, Pridoli, level K2, Eggenfeld section (Graz

Paleozoic), scale bar 1 cm.6 - Coll. n. E.I–001, external view of the specimen, showing slender longiconic form and fine, transverse ornament, Pridoli,

level K2, Eggenfeld section (Graz Paleozoic), scale bar 1 cm.7 - Coll. n. E.I–074, internal view of the specimen, showing cameral chambers and central siphuncle, Pridoli, level K2, Eggenfeld

section (Graz Paleozoic), scale bar 1 cm.

Fig. 8 Oonoceras sp. Coll. n. E.I–079, external view of the specimen, showing slender cyrtoconic form and oblique septa, Pridoli, levelK2, Eggenfeld section (Graz Paleozoic), scale bar 1 cm.

Figs. 11-12 Orthocycloceras sp.11 -Coll. n. E.I–165, external view of the specimen, showing fine, transverse ornament and transverse annulations, Pridoli, level

K2, Eggenfeld section (Graz Paleozoic), scale bar 1 cm.12 -Coll. n. E.I–165, external view of the specimen, showing fine, transverse ornament and slightly oblique annulations, Pridoli,

level K2, Eggenfeld section (Graz Paleozoic), scale bar 1 cm.

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however, this preliminary classification is based solelyon external features, mainly ornament and conch form,and requires further verification based on internal featuresafter sectioning of specimens has been completed. Thepreliminary data presented here includes a faunal list ofthe seven genera which have been ascertained to date andillustration of a selection of these specimens (Pl. 1, figs.1-12). The higher taxonomic classification system of theTreatise (Moore, 1964) has been followed where possiblewith modifications from more recent systematic workswhen appropriate.

FAUNAL LIST

Class CEPHALOPODA Cuvier, 1797Subclass NAUTILOIDEA Agassiz, 1847

Order ORTHOCERIDA Kuhn, 1940Superfamily ORTHOCERATACEAE M’Coy, 1844

Family ORTHOCERATIDAE M’Coy, 1844Subfamily MICHELINOCERATINAE Flower, 1945

Genus Michelinoceras Foerste, 1932(Pl. 1, figs. 5-7)

Genus Merocycloceras Ristedt, 1968(Pl. 1, fig. 4)

Genus Plagiostomoceras Teichert & Glenister, 1952(Pl. 1, fig. 1)

Subfamily KIONOCERATINAE Hyatt, in Zittel, 1900

Genus Parakionoceras Foerste, 1928(Pl. 1, figs. 3, 10)

Subfamily LEUROCYCLOCERATINAE Sweet, 1964

Genus Orthocycloceras Barskov, 1972(Pl. 1, figs. 11, 12)

Order ONCOCERIDA Flower, in Flower & Kummel, 1950Family OONOCERATIDAE Hyatt, 1884

Genus Oonoceras Hyatt, 1884(Pl. 1, fig. 8)

Family LECHRITROCHOCERATIDAE Flower, in Flower &Kummel, 1950

Genus Lechritrochoceras Foerste, 1926(Pl. 1, figs. 2, 9)

PALEOBIOGEOGRAPHY

The importance of nautiloid cephalopods forbiostratigraphy and paleobiogeography was highlightedby Crick (1990, 1993) who noted that Paleozoic nautiloiddistribution was controlled by water depth, distanceseparating adjacent shelf seas, and water temperature.Nautiloid cephalopods were also not subject to extensivepost-mortem drift, the latter being a reason that this group

has been considered in the past as unreliable aspaleobiogeographic markers (Westermann, 1998). Crickemphasized that much more detailed systematic work onnautiloid faunas with precise stratigraphic data was neededto facilitate their use for reliable paleobiogeographicreconstructions and as stated above the array of studiesemerging in recent years has shown this to be feasible.The Silurian Cephalopod Limestone Biofacies (Kriz,1998) is well developed in Spain, France, Sardinia, theCarnic Alps and Bohemia and has been famous since thelast century for its abundance of macrofossils,particularly of nautiloid cephalopods. Hence the name‘Orthoceras’ limestone was widely used in the literatureon these areas. A detailed multidisciplinary study of theoccurrence of the Silurian Cephalopod LimestoneBiofacies at various sections in the Carnic Alps which,focused on obtaining data concerning thepaleogeographical setting of the Carnic Alps during theSilurian (Ferretti & Histon, in press), has shown that thesehorizons with rich nautiloid faunas may be traced all alongthe northern Gondwana margin from Morocco, the OssaMorena Zone (South West Spain), Montagne Noire(France), South West Sardinia, the Carnic Alps to thePrague Basin. Kriz (1998) and Bogolepova (1998c) haveoutlined the distribution of cephalopod limestones duringthe Silurian along the North Gondwana margin, Perunicaand North Asia and Ferretti & Kriz (1995) did a detailedmicrofacies study of diverse horizons of this biofaciesin the Prague Basin identifying two distinct depositionalenvironments: one by surface currents and one within ashallower setting affected by storm action. Thecephalopod bearing limestone beds from the section beingstudied in the Graz Paleozoic also show diverseorientation of the nautiloid conchs on the bedding surfaceand taphonomic features which may be indicative of smallscale depositional cycles within this succession (Figs.5-8). Uni-directional orientation of conchs (Figs. 6-7)may indicate deposition by surface currents while theperpendicular orientation of conchs (Fig. 5) and distincttime-rich taphonomic features such as dissolution ofshell material and disarticulation of septal chambers onthe bedding surface (Fig. 8) may indicate deposition

Fig. 5 - Small block of cephalopod limestone E. I – 021, Pridoli, K2level, Eggenfeld section (Graz Paleozoic, Austria). Note well-preserved specimens on bedding surface showing two distinctperpendicular orientation directions. Scale bar 5 cm.

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within a shallower setting and periods of non-deposition.The presence of the common Circum Mediterranean

‘Orthoceras’ Limestone and ScyphocrinitesCommunities (Vai, 1999) and the Dualina nigra-Patrocardia bivalve subcommunity (Kriz, 1999) withinthe latest Pridoli of the Carnic Alps sections demonstratesthat faunal exchange was taking place during this intervalbetween the Peri Gondwana terranes and Baltica (Histon,2002). This may also be the case for the faunas of theGraz Paleozoic.

Unfortunately there are few age comparable faunasdescribed for considering exchange of the nautiloidfaunas between the North Gondwana terranes during thePridoli as systematic revision, particularly of theBohemian fauna, is still lacking. As outlined above manyauthors have shown links between the Sardinian (Gnoli& Serpagli, 1977, 1991; Serpagli & Gnoli, 1977; Gnoli,1990; Gnoli & Serventi, 2006, 2009 and referencestherein) and Bohemian (Marek, 1971; Kolebaba, 1975,1977, 1999, 2002; Turek, 1975; Marek & Turek, 1986;Manda, 1996, 2008; Gnoli, 1997; Stridsberg & Turek,1997; Manda & Kriz, 2006, 2007; Manda & Turek, 2009a,2009b, 2009c) Silurian nautiloid faunas within a broadstratigraphic framework while close relationshipsbetween the nautiloids of the Carnic Alps (Ristedt, 1968;Histon, 1997, 1998, 1999a, 1999b, 2002; Bogolepova,1998a; Gnoli & Histon, 1998; Gnoli et al., 2000; Serventi& Gnoli, 2001; Serventi et al., 2006, 2010; Gnoli &Serventi, 2008) and both the latter areas has also beensuggested. Histon (2002) contributed additional data tosupport the idea of faunal exchange between the CarnicAlps, in particular with Bohemia and Baltica during thelate Silurian. The conclusion of the study was that themore shallow water, facies restricted, nautiloid speciesdescribed were common to both areas possibly reflectingthe closeness of the Carnic Alps to Bohemia where theseforms are common in the Ludlow and/or Pridoli series(Marek & Turek, 1986; Manda & Turek, 2009c; Storchpers. comm.) while the more pelagic faunas in commonreflected the exchange between the various NorthGondwana terranes, Baltica and the Urals due to currents.

Fig. 6 - Small block of cephalopod limestone E. I – 001, Pridoli, K2level, Eggenfeld section (Graz Paleozoic, Austria). Note well-preserved specimens on bedding surface showing uniform orientationdirections but opposed apex direction. Small orthoconic shells areclustered near the large shell on the right. Scale bar 5 cm.

Fig. 7 - Small polished block of cephalopod limestone E. I – 061,Pridoli, K2 level, Eggenfeld section (Graz Paleozoic, Austria). Notewell-preserved specimens on bedding surface showing uniformorientation directions and telescoped specimens. Scale bar 5 cm.

Fig. 8 - Small block of cephalopod limestone E. II – 014, Pridoli, K2level, Eggenfeld section (Graz Paleozoic, Austria). Note preservationof specimens on bedding surface showing uniform orientationdirections and particular taphonomic features: disarticulation of septalchambers, lack of outer shell, some specimens are represented byonly the internal siphonal and cameral deposits. Scale bar 5 cm.

The preliminary results of the present study furthersupport this hypothesis as genera common to both theCarnic Alps, Sardinia, Spain (Ossa Morena Zone), France(Montagne Noire), Morocco (Tafilalt, Anti-Atlas) andBohemia (Prague Basin) are found at the Eggenfeldlocality of the Graz Paleozoic (Table 1). These in partrepresent the more pelagic component of the fauna andprobably are the result of surface current transport.However, some more benthonic elements may also reflectthe closeness of these terranes during this time slice.Further study of the faunas and precise classification atspecies level should shed more light on this aspect.

DISCUSSION

It is hoped that the results of the systematicinvestigation:

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(1) will increase and add to the existing documentationof the Silurian nautiloid fauna on a global scale and thusmake a further contribution towards the palaeobio-geographic knowledge of the position of this fragmentof the North Gondwana terranes at a precise stratigraphicinterval, the latest Pridoli;

(2) will add more data to support the idea of faunalexchange between North Gondwana terranes such asMorocco, the Ossa Morena Zone, Montagne Noire,Sardinia, the Carnic Alps, central Bohemia and Balticaand the documentation of distinct nautiloid communitieswithin precise stratigraphic intervals;

(3) will be of great importance for placing the nautiloidfaunas from the Graz Silurian successions within a globalscenario. The results of the study of the systematics andpaleobiogeography of the fossil nautiloids will provideimportant information on regional paleogeography andpossible migrational pathways for pelagic organisms. Thiswill yield further insights into the positioning ofpaleocontinents and seaways and mechanisms ofpaleooceanography during the Silurian.

ACKNOWLEDGEMENTS

This study is being funded by a grant from the Dr. Heinrich-Jörg Stiftung Karl Franzens Universität Graz. The authors are gratefulto both referees and to the editors for their comments which havegreatly improved the manuscript.

REFERENCES

Agassiz L. (1847). An introduction to the study of Natural history,in a series of lectures delivered in the hall of the College ofPhysicians and Surgeons. 58 pp. New York.

Barskov I. (1972). Late Ordovician and Silurian Cephalopod molluscsof Kasakhstan and Middle Asia. Akademia Nauk SSSR, 107 pp.Moscow.

Bogolepova O.K. (1998a). Silurian cephalopods: New data from theCarnic Alps of Austria. In Gutiérrez-Marco J.C. & Rabano I.(eds.), Proceedings 6th International Graptolite Conference &1998 Field Meeting, IUGS Subcommission on SilurianStratigraphy. Temas Geologico-Mineros ITGE, 23: 60-62.

Bogolepova O.K. (1998b). A brief account on the Upper Siluriancephalopods from the Valle syncline, province of Seville (OssaMorena Zone, southern Spain). In Gutiérrez-Marco J.C. &Rabano I. (eds.), Proceedings 6th International Graptolite

Conference & 1998 Field Meeting, IUGS Subcommission onSilurian Stratigraphy. Temas Geologico-Mineros ITGE, 23: 63-66.

Bogolepova O.K. (1998c). Silurian Cephalopod Beds from NorthAsia. In Landing E. & Johnson M.E. (eds.), Silurian CyclesLinkages of dynamic stratigraphy with atmospheric, oceanicand tectonic changes. James Hall centennial volume. New YorkState Museum Bulletin 491: 199-207.

Boucek B. (1936). Graptolitova fauna ceskeho spodniho ludlowu.Rozpravy ceske Akademie ved a umeni, Trida 2, 46: 1-26.

Crick R.E. (1990). Cambro-Devonian biogeography of nautiloidcephalopods. In McKerrow W.S. & Scotese C.R. (eds.),Palaeozoic Palaeontology and Biogeography, Geological SocietyMemoir, 12: 147-161.

Crick R.E. (1993). Biogeography of Early and Middle Paleozoicnautiloid cephalopods: Evidence for barriers to dispersal andevolution. Geobios, Mémoire Spécial, 15: 91-105.

Cuvier G. (1797). Tableau élémentaire de l’histoire naturelle desanimaux. xvi and 710 pp. Paris.

Ebner F. (1976a). Das Silur/Devon-Vorkommen von Eggenfeld -ein Beitrag zur Biostratigraphie des Grazer Paläozoikums.Mitteilungen der Gesellschaft der Geologie undBergbaustudenten, 37: 275-305.

Ebner F. (1976b). Die Schichtfolge an der Wende Unterkarbon/Oberkarbon in der Rannach-Fazies des Grazer Paläozoikums.Verhandlungen der Geologischen Bundesanstalt, 1976: 65-93.

Ebner F. (1978). Stratigraphie des Karbon der Rannachfazies imPaläozoikum von Graz. Mitteilungen der ÖsterreichischenGeologischen Gesellschaft, 69: 163-196.

Evans D.H. (1994). Irish Silurian Cephalopods. Irish Journal ofEarth Sciences, 13: 113-48.

Evans D.H. (2002). Some additional Ordovician and Siluriancephalopods from Ireland. In Wyse Jackson P.N., Parkes M.A.& Wood R. (eds.), Studies in Palaeozoic Palaeontology andbiostratigraphy in honour of Charles Hepworth Holland. SpecialPapers in Palaeontology, 67: 77-96.

Evans D.H. & Holland C.H. (1995). The nautiloid cephalopod orderEndocerida in the Silurian. Paläontologische Zeitschrift, 69 (3/4): 343-352.

Fenninger A. & Holzer H.L. (1978). Die Genese der Dolomit-sandstein-Folge des Grazer Paläozoikums. Mitteilungen derÖsterreichischen Geologischen Gesellschaft, 69 (1976): 109-162.

Ferretti A. & Histon K. (In press). A global study of the SilurianCephalopod limestone biofacies, Carnic Alps, Austria.Abhandlungen der Geologischen Bundesanstalt.

Ferretti A. & Kriz J. (1995). Cephalopod limestone biofacies in theSilurian of the Prague Basin, Bohemia. Palaios, 10: 240-253.

Flower R.H. (1945). Classification of Devonian Nautiloids. AmericanMidland naturalist, 33 (3): 675-724.

Flower R.H. & Kummel B. (1950). Classification of the Nautiloidea.Journal of Paleontology, 24 (5): 604-516.

Flügel H.W. (2000). Die lithostratigraphische Gliederung desPaläozoikums von Graz (Österreich). In Flügel H.W. &

Tab. 1 - Comparison of upper Silurian nautiloid cephalopod genera from the Graz Paleozoic area with upper Silurian faunas from Morocco(Tafilalt, Anti-Atlas), Spain (Ossa Morena Zone), France (Montagne Noire), Sardinia, the Carnic Alps and Bohemia.

06 Hi t t l P65 09/06/10 13 3972

73

Hubmann B. (eds.), Das Paläozoikum von Graz: Stratigraphieund Bibliographie. Österreichische Akademie der Wissenschaften,Schriftenreihe der Erdwissenschaftlichen Kommissionen, 13: 7-59.

Foerste A.F. (1926). Actinosiphonate, trochoceroid and othercephalopods. Denison University Bulletin, Journal of thescientific laboratories, 21: 285-384.

Foerste A.F. (1928). Cephalopoda. In Twenhofel W.H. (ed.), Geologyof Anticosti Island. Memoirs. Geological Survey of Canada,154: 257-321.

Foerste A.F. (1932). Black River and other cephalopods fromMinnesota, Wisconsin, Michigan, and Ontario, and other areas.Denison University Bulletin, Journal of the scientificlaboratories, 27 (1): 47-136.

Fritz H. (1991). Stratigraphie, Fazies und Tektonik im nordwestlichenGrazer Paläozoikum (Ostalpen). Jahrbuch der GeologischenBundesanstalt, 134 (2): 227-255.

Fritz H., Ebner F. & Neubauer F. (1992). The Graz Thrust-Complex(Paleozoic of Graz). In Neubauer F. (ed.), The Eastern CentralAlps of Austria, ALCAPA-Field Guide, IGP/KFU Graz: 83-92.

Fritz H. & Neubauer F. (1990). ‘Grazer Paläozoikum’. ExkursionFührer, TSK III, 3. Symposium Tektonik – Strukturgeologie –Kristallingeologie, 24 pp. Graz.

Gnoli M. (1990). New evidence of faunal links between Sardiniaand Bohemia in Silurian time on the basis of nautiloids. Bollettinodella Società Paleontologica Italiana, 29 (3): 289-307.

Gnoli M. (1997). A further contribution towards the taxonomicrevision of Silurian nautiloid cephalopods erected and/or reportedby J. Barrande in the last century in the Barrandian (centralBohemia). Acta Universitatis Carolinae, Geologica, 41 (1): 15-45.

Gnoli M. (2002) Northern Gondwanan Siluro-Devonianpalaeogeography assessed by cephalopods. PalaeontologiaElectronica, 5 (2): 1-19.

Gnoli M. & Histon, K. (1998). Silurian Nautiloids from the CarnicAlps: a preliminary investigation. Bollettino della SocietàPaleontologica Italiana, 36 (3): 311-330.

Gnoli M., Histon K. & Serventi P. (2000). Revision of the SilurianCephalopods from the Carnic Alps: The Gortani and Vinassa deRegny collection, 1909. Bollettino della Società PaleontologicaItaliana, 39 (1): 3-12.

Gnoli M. & Serpagli E. (1977). Silurian cephalopods of the Meneghinicollection (1857) - with reproduction of the original plate.Bollettino della Società Paleontologica Italiana, 16 (2): 137–142.

Gnoli M. & Serpagli E. (1991). Nautiloid assemblages from middle-late Silurian of southwestern Sardinia: a proposal. Bollettinodella Società Paleontologica Italiana, 30: 187-195.

Gnoli M. & Serventi P. (2006). A further oncocerid nautiloid fromthe upper Silurian of southwest Sardinia. GeoAlp, 3: 3-8.

Gnoli M. & Serventi P. (2008). A new cephalopod from the earlySilurian of the Carnic Alps (Italian side). Rivista Italiana diPaleontologia e Stratigrafia, 114 (2): 171-178.

Gnoli M. & Serventi P. (2009). Silurian nautiloid Cephalopods fromSardinia: the state of the art. In Corradini C., Ferretti A. & StorchP. (eds.), The Silurian of Sardinia. Rendiconti della SocietàPaleontologica Italiana, 3 (1): 109-118.

Hiden H.R. (1995). Zur Fossilführung des Basalanteils der hohenDeckengruppe des Grazer Paläozoikums (Österreich).Mitteilungen der Abteilung für Geologie und PaläontologieLandesmuseum Joanneum, 54: 77-91.

Histon K. (1997). Cephalopod Limestones. Cellon Section. InSchönlaub H.P. (ed.), IGCP - 421 Inaugural Meeting Vienna,Guidebook. Berichte der Geologische Bundesanstalt, 40: 92-99.

Histon K. (1998). Die Nautiloideen-Fauna aus dem Silur derKarnischen Alpen. Geologisch-paläontologische MitteilungenInnsbruck, 23: 105-115.

Histon K. (1999a). Revision of Silurian Nautiloid cephalopods fromthe Carnic Alps (Austria) - The Heritsch (1929) Collection inthe Geological Survey of Austria. In Lobitzer H. & Grecula P.(eds.), Geologie ohne Grenzen - Festschrift 150 JahreGeologische Bundesanstalt. Abhandlungen der GeologischenBundesanstalt, 56: 229-258.

Histon K., ed. (1999b). V International Symposium Cephalopods –Present and Past. Carnic Alps Excursion Guidebook. Berichteder Geolologischen Bundesanstalt, 47, 84pp.Wien.

K. Histon et al. - Silurian nautiloid cephalopods from the Graz Paleozoic

Histon K. (2002). A nautiloid assemblage from the Upper Silurian(Pridoli) of the Carnic Alps, Austria. In Wyse Jackson P.N.,Parkes M.A. & Wood R. (eds.), Studies in PalaeozoicPalaeontology and biostratigraphy in honour of Charles HepworthHolland. Special Papers in Palaeontology, 67: 115-133.

Holland C.H. (1998). The nautiloid Cephalopod Order Actinoceridain the British Silurian. Palaeontology, 41 (1): 183-192.

Holland C.H. (1999). The nautiloid Cephalopod Order Ascocerida inthe British Silurian. Palaeontology, 42 (4): 683-689.

Holland C.H. (2000a). Harrisoceras and Temperoceras closely relatedcephalopod genera from the British Silurian. Bollettino dellaSocietà Paleontologica Italiana, 39 (2): 117-122.

Holland C.H. (2000b). Silurian Cephalopods from the Pentland Hills.Scottish Journal of Geology, 36 (2): 177-186.

Holland C.H. (2000c). Rare cephalopods from the Pridoli of Englandand Wales. Geological Journal, 35: 25-31.

Holland C.H. (2002). Cephalopods from a borehole in the typeWenlock area. Proceedings of the Geologists’ Association, 113(3): 207-215.

Holland C.H. (2003). Some observations on bactritid cephalopods.Bulletin of Geosciences, 78 (4): 369-372.

Holland C.H. (2004). The curious case of ‘Orthoceras primaevum‘from the Silurian of Wales. Proceedings of the Geologists’Association, 115(3): 235-238.

Holland C.H. (2007). Cyrtoconic nautiloid cephalopods from theBritish Silurian. Proceedings of the Geologists’ Association, 118(4): 365-373.

Holland C.H. & Stridsberg S. (2004). Specific representation of theSilurian cephalopod genus Phragmoceras in Gotland and Britain.Geologiska Föreningens i Stockholm Förhandlingar, 126 (3):301-310.

Hubmann B. (1993). Ablagerungsraum, Mikrofazies undPaläoökologie der Barrandeikalk-Formation (Eifelium) des GrazerPaläozoikums. Jahrbuch der Geologischen Bundesanstalt, 136(2): 393-461.

Hubmann B. (2003). Plabutsch-Formation: nomen novum proBarrandeikalk (Mitteldevon, Grazer Paläozoikum). In Piller W.E.(ed.), Stratigraphia Austriaca. Österreichische Akademie derWissenschaften, Schriftenreihe der ErdwissenschaftlichenKommissionen, 16: 269-292.

Hubmann B. & Messner F. (2007). Stein im Bild: Die fazielleEntwicklung der Rannachdecke (Grazer Paläozoikum). Jahrbuchder Geologischen Bundesanstalt, 147 (1+2): 277-299.

Hubmann B. & Suttner T.J. (2007). Siluro-Devonian Alpine reefsand pavements. In Alvaro J.J., Aretz M., Boulvain F., MunneckeA., Vachard D. & Vennin E. (eds.), Palaeozoic Reefs andBioaccumulations: Climatic and Evolutionary Controls.Geological Society of London, Special Publication, 275: 95-107.

Hyatt A. (1883-1884). Genera of fossil Cephalopods. Proceedingsof the Boston society of Natural History, 22: 253-338.

Hyatt A. (1900). Cephalopoda. In Zittel K. von, Textbook ofPalaeontology, 1: 502-592. Macmillan & Co. Ltd. London, NewYork.

Kolebaba I. (1975). Caliceras n. gen. and ontogeny of C. capillosum(Barrande) (Nautiloidea, Michelinoceratida). Casopis proMineralogii a Geologii, 20: 377-391.

Kolebaba I. (1977). New information on longitudinally sculpturedorthoceroids. Casopis pro Mineralogii a Geologii, 22: 125-138.

Kolebaba I. (1999). Sipho-cameral structures in some Siluriancephalopods from the Barrandian area (Bohemia). Acta MuseiNationalis Pragae. Series B: Historia Naturalis, 55 (1-2): 1-15.

Kolebaba I. (2002). A contribution to the theory of the cameral mantlein some Silurian Nautiloidea; Mollusca, Cephalopoda. Bulletinof the Czech Geological Survey, 77 (3): 183-186.

Kriz J. (1998). Recurrent Silurian – lowest Devonian cephalopodlimestones of Gondwanan Europe and Perunica. In Landing E.& Johnson M.E. (eds.), Silurian Cycles Linkages of dynamicstratigraphy with atmospheric, oceanic and tectonic changes.James Hall centennial volume. New York State Museum Bulletin,491: 183-198.

Kriz J. (1999). Silurian and Lowermost Devonian Bivalves ofBohemian Type from the Carnic Alps. In Lobitzer H. & GreculaP. (eds.), Geologie ohne Grenzen - Festschrift 150 Jahre

06 Hi t t l P65 19/05/10 13 0873

74 Bollettino della Società Paleontologica Italiana, 49 (1), 2010

Geologische Bundesanstalt. Abhandlungen der GeologischeBundesanstalt, 56: 259-316.

Kröger B. (2008). Nautiloids before and during the origin ofammonoids in a Siluro-Devonian section in the Tafilalt, Anti-Atlas, Morocco. Special Papers in Palaeontology, 79, 110 pp.

Kuhn O. (1940). Palaozoologie in Tabellen. 50 pp. Fisher, Jena.Manda S. (1996). Cyrtograptus lundgreni Biozone in the

southwestern part of the Svatý Jan Volcanic Centre (Wenlock,Prague Basin, Bohemia). Bulletin of the Czech Geological Survey,71 (4): 369-374.

Manda S. (2007). New Silurian nautiloids Phragmoceras Broderip,1839, and Tubiferoceras Hedström, 1917, from the Prague Basin(Bohemia). Bulletin of Geosciences, 82 (2): 119-131.

Manda S. (2008). Palaeoecology and palaeogeographic relations ofthe Silurian phragmoceratids (Nautiloidea, Cephalopoda) of thePrague Basin (Bohemia). Bulletin of Geosciences, 83 (1): 39-62.

Manda S. & Kriz J. (2006). Environmental and biotic changes insubtropical isolated carbonate platforms during the Late SilurianKozlowskii Event, Prague Basin. GFF, 128: 161-168.

Manda S. & Kriz J. (2007). New cephalopod limestone horizon inthe Ludlow (Gorstian, lower L. scanicus Biozone) of the PragueBasin (Bohemia, Perunica). Bollettino della SocietàPaleontologica Italiana, 46 (1): 33-45.

Manda S. & Turek V. (2009a). Revision of the Pragian RutoceratoideaHyatt, 1884 (Nautiloidea, Oncocerida) from the Prague Basin.Bulletin of Geosciences, 84 (1): 127-148.

Manda S. & Turek V. (2009b). Minute Silurian oncocerid nautiloidswith unusual colour patterns. Acta Paleontologica Polonica,54 (3): 503-512.

Manda S. & Turek V. (2009c). A Silurian oncocerid with preservedcolour pattern and muscle scars (Nautiloidea). Bulletin ofGeosciences, 84 (4): 755-766.

Marek J. (1971). The genus Cyrtocycloceras Foerste, 1936(Nautiloidea) from the Silurian of Central Bohemia. Sbornikgeologickych ved, Paleontologie, 14: 107-131.

Marek J. & Turek V. (1986). Cephalopods. In Kriz J., Jaeger H.,Paris F. & Schönlaub H.P. (eds.), Pridoli – the fourth subdivisionof the Silurian. Jahrbuch der Geologischen Bundesanstalt, 129(2): 340-341.

M’Coy F. (1844). A synopsis of the characters of the CarboniferousLimestone fossils of Ireland. 274 pp., Dublin.

Moore, R.C. (1964). Treatise on Invertebrate Palaeontology, pt. KMollusca 3. Geological Society of America and University ofKansas Press. 519 pp., Kansas.

Ristedt H. (1968). Zur Revision der Orthoceratidae. Akademie derWissenschaften und Literatur, Abhandlungen der mathematisch-naturwissenschatlichen Klasse, 4: 213-297.

Ristedt H. (1981). Bactriten aus dem Obersilur Böhmens.Mitteilungen des Geologisch-Pälaontologischen Instituts derUniversität Hamburg, 51: 23–26.

Serpagli E. & Gnoli M. (1977). Upper Silurian Cephalopods fromSouthwestern Sardinia. Bollettino della Società PaleontologicaItaliana, 16 (2): 153-196.

Serventi P., Corradini C., Simonetto L. & Pondrelli M. (2006).Silurian nautiloid cephalopods of the Museo Friulano di StoriaNaturale: Family Orthoceratidae. Gortania, 28: 29-57.

Serventi P. & Feist R. (2009). Silurian nautiloid cephalopods fromthe Cabrieres area (Montagne Noire, France): a preliminary report.In Corriga M.G. & Piras S. (eds.), Time and life in the Silurian:a multidisciplinary approach. Abstracts. Rendiconti della SocietàPaleontologica Italiana, 3 (3): 341.

Serventi P. & Gnoli M. (2001). Nouvi ritrovamenti di Cefalopodinautiloidi nelle Alpi Carniche. Giornale di Geologia, 3, 62,supplemento: 9-14.

Serventi P., Gnoli M. & Simonetto (2010). Actinoceratid Cephalopodsfrom the Silurian of the Carnic Alps (Italian side). Bollettinodella Società Paleontologica Italiana, 49 (1): 75-81.

Stridsberg S. (1985). Silurian Oncocerid cephalopods from Gotland.Fossils and Strata, 18, 65 pp.

Stridsberg S. & Turek, V. (1997). A revision of the Silurian nautiloidgenus Ophioceras Barrande. Geologiska Föreningens iStockholm Förhandlingar, 19: 21-36.

Sweet W.C. (1964). Subfamily Leurocycloceratinae. In Moore R.C.,Treatise on Invertebrate Paleontology, pt. K, Geological Societyof America and University of Kansas Press, K230, Kansas.

Teichert C. & Glenister B.F. (1952). Fossil Nautiloid faunas fromAustralia. Journal of Paleontology, 26: 730-752.

Turek V. (1975). Genus Kosovoceras gen. n. in the Silurian of CentralBohemia (Nautiloidea). Sbornik geologickych ved,Paleontologie, 17: 7-44.

Vai G.B. (1999). Wenlockian to Emsian communities of the CarnicAlps (Austria and Italy). In Boucot A.J. & Lawson J.D. (eds.),Paleocommunities – a case study from the Silurian and LowerDevonian, Cambridge University Press: 282-304.

Westermann G.E.G. (1998). Life habits of nautiloids. In Savazzi E.(ed.), Functional Morphology of the Invertebrate Skeleton, Wiley& Sons: 263-298.

Zittel K., von (1900). Textbook of Palaeontology, 1: 502-592.Macmillan & Co. Ltd. London, New York.

Manuscript received 17 October 2009Revised manuscript accepted 10 February 2010

06 Hi t t l P65 19/05/10 13 0974