Upper Ordovician conodonts from the Prague Basin (Bohemia)

LATE ORDOVICIAN CONODONTS

FROM THE PRAGUE BASIN

,

BOHEMIA

ANNALISA FERRETTI

Ferretti,A.1998.Late Ordovician conodontsfrom the Prague Basin,Bohemia.In:H. Sza-niawski(ed.),Proceedings of the SixthEuropean Conodont Symposium (ECOS VI). -Palaeonto logiaPolonica58, 123-1 39.

A conodon tfaunaisreported for thefirst timefrom the Late Ordovician ofBohemia.Two different levelsof the Kraluv DvurFormation,both well known for their brachiopod and trilobiteassociati ons,producedpoorand fragmentary conodont material,which neverthe-lesscan be interpreted asAshgillin age.The materialmost closelyresemblesthefauna of

southern Europe ,but there are also similarities to the Anglo-Balticconodont associ ations. Aspecial conodont extraction technique, suitable for argillaceous-calcareo us mixed s edi-ments,isdescribed.

Key wor ds :Conodonta,Ordovician, Bohemia.

Annalisa Ferretti[ferretti @unimo.itj , Departm ent of Earth Sciences, Via Universita 4, 41100 Modena,Italy.

124 ANNALISA FERREITI

INTRODUCTION

In the Ordovician, the Prague Basin (Barrandian) was a small linear depression situated in a marginal part of the Gondwana continent (HAV LlCEK 1981;STORCH and MERGL 1989). It is thought to have been composed of separate blocks and/or microplates (STORCH 1990).Up to 2500 m thick, shale-dominated sequences, with sporadic sandstone intercalations, were deposited in the basin as a response to both tectonic movements (HAVLic EK 1980) and eustatic sea-level changes(CHLUpAc and KUKAL1988).

The Upper Ordovician formations (Kraluv Dviir Formation and Kosov Formation) and the continuous sedimentary record across the OrdovicianlSilurian boundary crop out in numerous sections (Fig. 1).

Brachiopods and trilobites are common.Gastropods,ostracodes, cystoids, rare graptolites, bivalves and conulariids have alsobeen reported.Two horizonsin the lower part of the KosovFormation have recently been interpreted as glaciomarine diamictites (BRENCHLEY and STORCH 1989; BRENCHLEY et al. 1991).

Black Silurian graptolitic shales overlie the Ordovician strata.

The peculiar nature of the Ordovician fauna, mostly reflectingshallow water conditions,ascompared to coeval occurrences elsewhere,led SPJELDNAES(1961) and HAVLlCEK(1974, 1982) to include Bohemia in the cold-water "Mediterranean Province".This province,corresponding to the "Selenopeltis Province" of WHITTINGTON and HUGHES (1972), was periodically influenced by warm-water episodes (HAVLlCEK

1989). The Perunica microcontinent, a separate unit between Gondwana and Baltica, was recently pro-posed by HAVLicEKand FATKA(1992) to stress once more the unique character of the fauna from the Prague Basin. Difficultiesin correlating the Prague Basin formationsto the British Standard Scale,caused by graptolite paucity and differences in benthic assemblages, were partially overcome with the creation of new chronostratigraphic units for the upper part of the Ordovician. HAVLic EK and MAREK (1973) introduced the "Kralodvor" and "Koso v" Series as time equivalents of the Kraluv Dvur and Kosov

Formations respectively. FATKA et al. (1995) recently reinterpreted them in terms of"stages" that corre-spond approximately to the Ashgill Series. Nevertheless, difficulties in referring to the standard strati-graphic scale still remain .

Lower Ordovician conodont faunas were already described by SPINAR et al.(1965), DZIK (1984) and ZUSKovA(1993).Even though the material investigated here is poorly preserved and the total number of recovered specimens is small,this conodont collection is the first ever reported from the Late Ordovician of the Prague Basin and it comes from an unusual type of lithology. The conodont fauna described here is housed in the paleontological collections at the Department of Earth Sciences of the University of Modena (Italy) under repository numbers IPUM 24964-25020.

Acknowledgements.- My sincere thanks go to Petr STORCH (Geological Institute - Academy of Sciences of Prague) for providing the material and the always precise answers to my questions and for the critical reading of the manuscript. Enrico SERPAGLI (Univers ity of Modena) is acknowledged for constructivecomments and assistance during all stages of this study and for improving the text. Chris-topher R.BARNES (University of Victoria) provided important suggestio ns and critically read the

manu-script. Jerzy DZIK expertly revised the final version of this paper. Claudio GENTlLlNI (University of Modena) produced the S.E.M.photographs and isdeeply thanked.

This research was funded by C.N.R. and M.U.R.S.T.grants (resp. E. SERPAGLI).

STRATIGRAPHIC FRAMEWORK

The Kraluv Dviir Formation is representedby 25-200 m of clayey shalesor claystones with silt admixture (HAVLicEK1981;STORCHand MERGL 1989).An"Iron Ore Horizon" with silicate or carbonate ooids is locally

present at the base of the formation (HAVLlCEKand FATKA1992). TheDedzetinamacrostomoidesbrachiopod community, similar to the Foliomena Community, occurs in the middle part of the formation and reflects deep water conditions(benthic assemblage4 to 5;HAVLlCEK 1982) (Fig. 2). Above and below, the Rafano-glossa Community is reported. It corresponds to benthic assemblage 6 (HAVLicEK1982; BRENCHLEYand STORCH 1989).The younger of these occurrencesis in carbonate nodules among clayey shales (level Al of STORCHand MERGL 1989). This level includes a poor but well preserved deep-shelf fauna of trilobites, minute bivalves,gastropods,nautiloids and rare brachiopods of the Rafanoglossa leiskowiensisCommunity. Shales

LATE ORDOVICIAN CONODONTS FROM THE PRAGUE BASIN, BOHEMIA 125

PRAHA

H:~:dpost-Paleozoic platform sediments _ Kraluv Dvur Formation

____ fault or overthrust -& sampled sites

5km

Fig. 1

Location map and extensionof the Kraluv Dvur Formationin the Prague Basin(modified afterSTORCHandMERGL1989).

immediately above provided graptolitesindicative of the ScalarigraptusangustusHorizon of the D.anceps Zone (STaRcH1989). About 3 m below the top of the Kraluv Dvur Formation, a thin (max.10 cm) calcareous layer with abundant sessile organisms is present (B I level of STORCHand MERGL 1989 or "Pernfk Bed" of BRENCHLEY and STORCH 1989).The ratio between carbonate and clay content is variable (55% at Libomysl, 45% at Levin; STaRCH and MERGL 1989). This level contains a rich fauna of trilobitesand small isolated brachiopods of the ProboscisambonCommunity (benthic assemblage5 to 6;STORCHand MERGL1989). The fauna again resembles theFoliomena Community (HAVLICEK 1982;HAVLICEKand MERGL 1982; COCKSand RONG 1988; BRENCHLEY and STORCH 1989; STORCH and MERGL 1989) and indicates deep, cold-water environments (COCKSand RONG1988).Ostracodes, gastropods,blastoids and cystoidsare also present. This high-diversity community disappears abruptly and isreplaced by a low diversityMucronaspis fauna (benthic assemblage 5 to 4;STaRCH and MERGL 1989), including alsoostracodes,bivalves,brachiopods,conulariids and a monospecificgraptolite assemblage.The graptolite,identified as Glyptograptuscf. ojsuensis is indi-cative of the upper part of the D. anceps Zone and/or the Paraorthograptus pacificus Subzone (STORCH 1990). This Mucronaspis level is reported from silty mudstones and shales that start few centimeters immediately above the Pernfk Bed and extend upwards (levels B2 and C of STaRCHand MERGL 1989). No guide graptolitesto prove the Rawtheyan age of the upper Kralodvor have been found so far,and this age is suggested mainly on the basis of changes in the benthic assemblage composition (STORCH 1989). The early Hirnantian glacio-eustatic regression is,in fact,reflected in other areas elsewhere by the sudden appearance of shallow marine sandy facies and the spreading of the monotonous Hirnantia and Mucronaspis faunas (STORCH 1990).The RawtheyanlHirnantian boundary is therefore placed within the few meters of shales that separate' the Pemik Bed from the firstglacio-marine episode at the base of the overlying Kosov Formation (STaRCH 1990). This unit,40-150 m thick, has at its base two diamictitic levels, separated by 1-2 m of shales. The levels provided facetted pebbles and dropstones(beautifully illustrated from the Levin Section; STORCH 1990:p.228) interpreted asdeposits of seasonal ice (BRENCHLEY and STORCH 1989). Three meters above the first glacio-marine evidence,thin beddedsandstones recording the peak of the firstphase of the Hirnantian regression occur. A trueHirnantia fauna, represented by theH. sagittiferaCommunity,is present in the uppermost part of the Kosov Formation (MAREK 1963; MAREK and HAVLICEK 1967;STORCH 1986; FATKAet al. 1995).The fauna is associated with the index graptolite Glyptograptus bohemicus (STaRCH 1986).About 10-20 cm above, the Silurian starts with black graptolitic shales assigned to theAkidograptus ascensus Zone(= lower part ofParakidograptus acuminatusZone; STORCH 1990).

126 ANNALISA FERRETII

MA TERIAL AND METHODS

Two different levels of the Kraluv Dviir Formation were investigated (Fig. 2). Six samples were collected from the calcareous nodules (level AI;STORCHand MERGL 1989) intercalating to shales belong-ing to the lowermost part of and/or just underlybelong-ing the angustus Horizon from the middle part of the Kraluv Dvur Formation at Levin. Nine samples (2 from Lybornysl, 7 from Levin) were collected from the Pernfk Bed (= level B 1;STORCH and MERGL 1989),about 10 m above the previous samples.

Normal acid treatment was mostly ineffective,especially for the samples collected from the Pernfk Bed.A technique generally reserved in our laboratory for disaggregating slightly indurated sediments with high clay content was partially applied. Samples were slightly crushed (if big pieces were present) and placed in small quantity in plastic beakers. They were then covered with the detergent "NeoDesogen", a perfumed yellowish solution of 10%alkyldimethylbenzylammonium chloride (produced by Ciba Geigy S.p.A.-Origgio, Varese, Italy) used in the medical field as a fungicide and bactericide. Samples were soaked for several days and occasionally stirred with a plastic stick. The disintegration was very slow with a mild effervescenceobservable with naked eye.When the reaction was complete, the samples were transferred to larger plastic buckets and treated with a solution of acetic or formic acid to remove the calcareous fraction. The resulting residue was wet-sieved. The insoluble sample was completely dried at room temperature. Sometimes, the drying was accelerated by mild heating. Only when perfectly dessi-cated, was the material returned again to fresh NeoDesogen and a new cycle was started. The entire process of disintegration could take as much as several weeks.The abundant residues were finally concentrated in heavy liquid using sodium polytungstate.

A similar technique had been described by ZINGULA (1968) with Quaternary "0" compound,but his process involved boiling while this method is at room temperature.

K

o

s

o

V K R

A

L

U

V

<1Mucronaspis Community

c::o:::.

18<'.',:1 diamictites

f2I5J

calcareous nodules

~ shales

Ivv v3

Pernik Bed

D V

U

R

RaJanoglossa Community~

*

Dedzetina Community ~ Fig.2

Stratigraphic column of the Late Ordovician exposed at Levin (modified afterBRENCHLEYandSTORCH 1989);

*

denotes sampled level.

LATE ORDOVICIA NCONODONTS FROM THEPRAGUEBASIN.BOHEMIA 127

Thefossilfaun arecoveredin theacidresidue,associ ated with conodonts,isdominated bywell preserved silicifie d ostracodes (the first such finding from the Ordovician of Bohemia), often complete with the two valves still connected and with their spines preserved. They are now under study by Miroslav Kmrrx (Ge olog ica l Institute- Academ yof Scien ces,Prague).Othercommon elementsare juvenilegastropodswith numerouspyritized molds, sponges andsponge spiculae (sometime s pyritized ),trilobitefragments, brachio-pods,chitinozoans,bivalves,bryozo ans and the phosphatic sclerites of the problematic paleoscolecid Mila-culum.Pyrite isalso common insomesamples(e.g.,BO 5)with bothcrystalsand framboidspresent. Among

the two studied lev els,the faun acoming from the Pemik Bed appearsmore abundant and diverse.

The conodont colle ct ion was isolated from 15 samples with a total wei ght of approx imately 22 kg.

Over 400conodo nt elementswere recover ed. Conodont abundanceis extre me ly var iable within the same le vel ,but it iscertainl y much higher in the Pernik Bed.The absolute abundance rangesfrom as little as

1.4 elements to as much as ISelements per kilogr am in the calcar eou s nodul es and from aslittleas 8.7 elements to as much as 70.3 elements pe r kilogr am in the Pernik Bed.The fauna consists of only very sma ll individualsand conseque ntly the 63x micro scope enlarge me nt hasbeen nec essary for picking the

residue .Most of the elementsare poorly preserved and fragmentary , which makes specific determination

difficult. The conodont Color Alteration Index (C AI) value is 3, indicating heating temper atures in the range of 110-220°(EpsTE INet al. 1977).

THE CONODONT ASSEMBLAGE

The Bohemi an materi al under study includes 13 multielement spec ies representing 1I genera, 8 of

which are left in ope n nomenclature. The list and abund ance of the spec ies are give n in Table I.The fragmentary preser vation of the material and the incompleteness of man y apparatuses make premature

any detailed interpretation on the faun a abund ance . Neverthele ss, when considering the fauna as a whole,

elements of Scabbardella altipes (HENN INGSMOEN, 1948) (30,%) and Sagi ttod ontina cf.robusta KNOPFER,

1967 (22%) predominate .In contrast, spec ies such as lcriodell a sp.and Birksfeldia 'l sp.are repre sented

by very few specimens.

The faun a from the Pernik Bed is more diver se than that from the calca reous nodul es. It marks the appearance ofrelatively abunda ntelements of Sagittodon tina cf.robusta aswell as other species such as

Plectodinaaff. tenuis(BRANSON et MEHL, 1933 ) and lstorinus erect us KNOPFER ,1967,mostlyrepresented

by sing le eleme nts.Furthermore, the M eleme ntof Amo rp hogna thus aff. lindstroem i (SERPAG LI , 1967) is

here rep ort ed .

BIOSTRATIGRAPHY

All Pa element s ofAmo rp hognath usfro m boththecalca reous nodules and the PernfkBedare broken, preventing spec ific determination . A sing le M element ofA. aff. lindstro emiwas reco vered in the Pernik

assem blage.Nocomple te diagnosisof the appara tus struc ture of this speci es hasever been give n and the Boh emi an materi al is too scarce to attempt one. Furthermore, it cannot be definitely excluded that this co llectio n might conta in also A. ordov icic us (B RANSON et MEH L, 1933).For all P and S eleme nts of the

genusAmo rphagnathus the open nomencl ature is preferred.

A. lindstroemi hasbeen reported in the upper Keisley Limeston e (most likely Rawth eyan in age ) from the north of England(O RC HARD 1980 ) and in the Ashgill of the Itali anCarnic Alps (SERPAGLI 1967).A. aff. lindstroemi ,found among theBohemianfaun a,doesnot appear to havedevel opedthe typical featuresofA. lindstroemi completely and could therefore represe ntan early evolutionary stag e of thislineage." Holodon-tiform" elements similar to the M eleme nt of A. aff. lindstroemi were found at the base of an Ashgilli an section (Shoalshook Formation at Whitland) in Wale s(BAR NESand FERRETTI in preparation) .

Hamarodu s europae us (SERPAG LI,1967) see ms toappear in the Rawtheyan in GreatBritain (ORC HA RD 1980;SWEETand BERGSTROM 1984 )as wellas in many southern European areas of northern Gondwana (FERRETTI 1992). Nevertheless ,this spec ies isalreadyrep orted from the AmorphognathussuperbusZone

128 ANNALI5A FERREITI Table I

Detailed compositionof the Bohemian conodont fauna;

*

denotes overestimated material, as mainly composed by fragments;cdenotes samples from Libornysl (all the others are from Levin).

Calcareous nodules Pernik Bed

no I

ao

2

ao

3 B04

ao

5 PI 5

r

52' 53 54 KI K2 K3 P2 PB I total Amorphognathussp. Pa* I 2 4 8 10 8 1 7 10 6 57 Pb 2 I 4 1 I I 10 Sa 2 2 2 6 Sb 1 I I 1 4 Se 1 I 2

A.aff.lindstroemi

M I I Birksfeldia?sp. Pb I I Dapsilodus mutatus I I I 3 Hamaroduseurop ae us Pb I I 2 M 1 2 2 2 7 Sb I I Se 1 I I I I 1 6

Hamarodu scf.europaeus

M I I 2

Icriodellasp.

Pa I I

Pb I I

Istorinus erectus I I

Nordiodusitalicu s

M I I

Plectodina aff.tenuis

Pa I I Pb I I Protopanderodus sp. 1 1 Sagittodontinacf.robusta Pa 4 4 31 10 5 1 6 10 12 83 Sa 3 3 Sb 3 I 4 Scabbardella altipes * 3 I 11 2 13 6 34 8 5 3 16 13 10 125 "carniodiform"element 2 1 3 5 I I I 14

Gen.etsp.indet. I 1

Indet. fragments 4 3 I 1 5 5 19 10 5 2 9 8 4 76

I 415 Weight 1.3 0.7 0.7 1.6 1.2 1.3 1.7 1.5 1.65 1.35 1.6 0.8 1.45 1.7 3.3 21.85

(ranging then into the followingA. ordovicicus Zone) in the Scandinavian-Baltic-Polish region (STOUGE and RASMUSSEN 1996) and from the Hamarodus europaeus Zone of south-central China, dated as Carado-cian by AN (1987).

Sagittodontina robusta, represented possibly only in the Pernfk assemblage, has been so far reported from the Early Ashgill of Europe and north Africa (BERGSTROM and MASSA 1992).

The mutual occurrence of Sagittodontina cf. robusta and Istorinus erectus would indicate an Early Ashgill age for the investigated fauna,but it is also possible that the Bohemian material might extend the range of these species into younger time-intervals.

LATE ORDOV ICIANCONODONTS FROM THE PRAGU EBASIN,BOH EMIA

PALEOBIOGEOGRAPHY

129

Several studies have emphas ized thepeculiarnature oftheLateOrdovicianBohemian fauna and tried to locatethe PragueBasin paleogeographi cally.HAVLlCEKand FATKA(1992)recentl ypositionedthe basin as a separa te microcontinent,called Perun ica,ina temperate region bounded bytheNorth Gondwanaregion to

the south and theAnglo-Balticregiontothe north. The PragueBasin was dom inatedbyMediterranean-type faunasand had marine connectionswith Baltica already in the EarlyOrdovician (DZIK 1984).Thisb iogeo-graphic pattern reappeared in Kralodvor and Kosov timesreflectin gboth anarro win g of the Tornquistand the Rheic seas as well as climatic amelioration (HAVLlCEK and FATKA1992). Within the high-diversified

deep- water Proboscisamb on Community of the Pernfk Bed, some trilobit es sugg est the invasion of new, warmer water elements comingfrom the Anglo-Scandic Province (STORCHand MERGL 1989).

Evenifconodont absen cein theunderlyin gOrdovician sedime nts prevent s anycompar iso n withcoeva l

conodo nt associations fro m other region s, the Bohemian conodo nt faun a reported here still has strong Mediterran ean affinity, bearin g typi cal compo ne nts of the Mediterran ean Province conodont faun a suc h

asSagittodontinacf. robustaandlstorinu s erectus .Furtherm ore , S.robustaappears restrictedtohi

gh-lati-tude areaswhichoccupied asub-po lar position in the LateOrdovician (SWEET 1988).Nevertheless,genera

likeBirksfeldiaandPlectodin a,commonin GreatBritain and in theCarnicAlps,and presentin the studied

collection with scarce elem ent s, indicatethe existen ce of aconnec tionwith these regions.

SYSTEMATIC PALEONTOLOGY

The poor preser vati on of the fauna prevent s a detailed morphological and taxonomic discu ssion ,

therefore onlyessentia l comment s are give n here.Synonym yislimitedto firs t morphospecie sdescription ,

first appara tus reconstruction and mostrecent reports . Orders and fam ilies are mostl yfrom SWEET (198 8) .

Orde

r

Belodellida

SWEET,

1

988?

Family

Ansellidae

FAHRJEUS

e

t

HUNTER,

19

85?

Genu sHamarodusVIIRA, 197 4

Typespecies:DistomoduseuropaeusSERPAGLI , 1967.

Hamarodus europaeus (SERPAGLl, 1967 ) (PI. 1: 11-17 )

1955.Microcoelodus'lsp.;RHODES:p. 133,pI. 10:15,19,22. 1955. CordyloduselongatusRHODES;RHODES:p.135,pI.7:5-6. 1959.Oistodussp.n.;LINDST ROM:p.440, pI. 3:13.

1959.Cordylodussp.n.;LINDST ROM:p.438,pI.3:34-36.

1964 .?Neoprioniodus brevirameussp. n.:WAU .lSER:p.47,pis 4:5,29 :5-10. 1964.?Rollndya primasp.n.;WALUSE R:p.71, pis4:6,31:I,2.

1966.Oistodu sbreviconusBRANSONetMEHL;HAMAR:p.63,pI. I:19,text-fig.4(11). 1966.N.genusandsp.n.;HAMAR:p.77, pI.3:8-10,text-fig. 5 (5a,b).

1967.Distomodus europaeussp.n.;SERPAGI.I :p.64,pI. 14:1-6. 1967."Oistodus "nigersp.n.:SERPAGLI :p.79,pI.20:1-7.

1967.Oistodus abundansBRANSONetMEHL;KNOPFER:p.34,pI.5:4. 1976.Hamarodus europaeus(SERPAGLI);DZIK:p.435,text-fig.36 (a-g).

1994.Hamarodusbrevirameus(WALI.IS ER) ;DZIK:p. Ill,pI.24:14-1 9,text-fig. 31a. 1997.Hamarodus europaeus(SERPAGI.I);FERR ETTIandBARNES:p.22,pI.3: 1-14.

Remarks. - Hamarodus europae usismoderately abunda nt in thefaun a.Pbelements badl ypreser ved andencrus ted, but one (PI. 1: 11)shows termin aldenticulati on oftheanteri or and upper keels.Mele ments

always brok en and present only in thePernfkBed .Seleme nts commo n in many samples. Occurrence.- Upper Middle and LateOrdo vici an of Euro pe and China.

130 ANNALlSA FERRETII

Hamarodu scf. europ ae us (SERPAGLI, 1967) (PI. 2: 13a ,b)

Description. - M ele me nt whose basal margin of the only complete face is in later al view (PI. 2: 13b ) conve x in itsbasal and median part andconcave on ly in the posteri or part.

Remarks.- SERPAGLI (1967 :pl.20:4a-d )figured some specime ns which hadthese featuresonlyon

one face ,while the othe rside of the eleme nt had a basal margin that was also conca ve basall y.

These eleme ntsare probabl y a variantofthe M ele me nts ofHamarodu s europaeus.

F

amil y

Dapsilodontidae

SW EET ,

19

88

Genu sDap sil od us COOPER, 197 6

Type species:Distacodu s obliquicostatus BRA NSO NetMEHL, 1933.

Dap silodus mutatus (BRANSONet MEHL, 1933) (P I.2: 15)

1933.Belodus?mutatussp.n.;BRANSONetMEHL: p.126, pI.10:17.

1959.Acodusinomatussp.n.;ETHINGToN:p.268, pI.39: 11.

1959.Distacodus procerussp. n.;ETHINGTON:p.275, pI.39:8.

1967.AcoduscurvatusBRANSO NandBRAN SON; SERPAGLI:p.41,pI.6:3a-c.

1967.Acodus mutatu s(BRANSONetMEHL );SERPAGLI:p.41,pI. 6:la, b,6 a,b.

1967.Acontiodusprocerus(ETHINGTO N) ;SERPAGLI: p.46,pI. 9:6-11.

1980.Dap silodusmutatus(BRANSONetMEHL);ORCHARD:p.20,pI. 5:6,15,16, 21.

1994.Daps ilodusmutatus(BRANSONetMEHL);DZIK:p.64,pis 11: 24-26,31-35, 14:8,9,text-fig.6d.

1997.Dapsilodusmutatus(BRANSONetMEHL );FERRETTIandBAR NES:p.23,pI.3:15-19.

Material. - The Boh em ian collec tion incl udes rare spec ime ns of this species, one found In the calc areou s nodul es and two in the Pernfk Bed .

Occurrence.- Middle-Late Ordo vici an of Europ e and North Amer ica.

Order

Prioniodontida

DZIK,

1976

Famil

y

Balognathidae

HASS,

1959

Genu sAmo rphognathus BRANSONet MEHL, 193 3

Typespecies:Amorphognathusordovicica BRA NSONetMEHL, 1933.

Amorphog na thus aff. lindstroemi (SERPAGLI, 1967 ) (P I. I: 10a-c)

aff. 1967.Goniodo ntuslindstroemisp.n.;SERI'AGLI :p.41,pI.16:1--4. aff.1980.Amorphognathuslindstroemi(SERPAGLI) ;ORCHA RD:p. 16,pI.4:28.

Description.- Aspec ies ofA1110rphogn ath us inwhic h the"holodontiforrn" M eleme nt bea rs a sma ll denticle on the oute r-late ra l flan ge ofthe cus p. The oraledge ofposteri orprocess exte ndsas a sha rpcarina

along the po sterior face ofthe denticle.Cusp bicon vex in oral view.

Remarks.- ORCHARD (1980: p. 16) observed that the "barb-like denticle", located on the "a ntero-later al face of the cus p" and aborally direct ed , "is the only feature which may curre ntly be used to

distingui sh" A. lindst roemi fro m A. ordovicicus. The Boh em ian eleme nt differ s from that definiti on in havin g the denticle which is orient ed laterall y and not aborally. Simi lar featu res were observe d in "holodont iform" eleme nts at the base of an Ashgi llian seque nce in Wales (BARNES and FERRElTl in prep aration ), whichseem to occ urjust earlier than definiti ve M ele me nts ofA.lindstroem i.

A.aff. lindstroemi rep ort ed by ORCH ARD (1980) fro m the Late Rawtheyan Cystoid Lim eston e of the

north of Engl and has a lessde vel op ed denti cle and the oral rid ge ofposteri or process seems to run alo ng the base ofthe cus p.

A.lindstroemi eo-occ urs withA.ordovicicus in the Italian Carn ic Alps (SERPAGLI 1967 ) and in Sardinia (FER ElTI and SERPAGLI work in progress).Nodef inite criteria forrecogn izing theAmorphog nathus species

withonlyextra-vho lodo ntifo rm" eleme nts havebeen sofarprop osed. A waitingfor an unequi vocaldefinition of RHODES'materi al fro m the Keisle y Limestone,this species isnam ed after the "holodo ntiform" eleme nt.

LATEORDOVIC[AN CONODONTS FROM THEPRAGUEBASIN,BOHEMIA

Amorph ognathus sp.

(PI. 1: 1-9)

131

Remarks.- Paelem ent sarerepresentedby brokenisol ated or rarely coupled processe s;their number

in Table 1is overe stimated as representing fragment s. Small Pb elements, both in sinistra l and dextral

form, wer e found only in the PernfkBed. Selem ent sare rare and often encrus ted. GenusBirksfeldia ORCHARD, 1980

Typespecies:Birksfel dia circumplicata ORCHARD, [980.

Birksf eldia?sp.

(PI. 2:9)

Material. - One sma ll incomplete Pbelem ent, found in the Pernfk Bed, isassigned to this genus in open nomencl ature.

Genu sSagittodontina KNOPFER, 1967

Type species:Sagittodontina robustaKNU PFER, [967.

Sagittodontinacf.robusta KNOPFER, 1967 (PI.2: 1-8)

cf.1967.Sagittodontinarobustasp. n.;KNUPFER:p.38,pI.8:3a,b.4.

1982.Sagiuo dontina'lsp.;PARISetal.:pI. 2:[2, 13,pI. 4:3,5,7,8 .

cf. 1983.Sagittodontina bifur cataKNUPFER; BERGST RO M:fig.4.

cf.[990.Sagittodontina robustaKNUPFER;FUCHS :p.206,pI. 5:[- 8,pI. 7:I.

cf.1992.SagittodontinarobustaKNUPFER;BERGST ROMandMASSA:p.1338,pI. I:6- [4, 17.

cf.[997.Sagittodontinarobusta KNUPFER;FERRETT IandBARNES:p.30,pI. 4:[- 23.

Remarks.- Sagittodontinacf.robustaisthe second mo st ab unda ntspec ies of the faun a,but reported

only from the Pernfk Bed .It ismostl yrepresent ed byanteri or processes ofPaeleme nts havin gup to five largedenticles.Cusphaslater alkeeledmargin extend ingalmos tall the wayto its ape x and whichextends

distally as athin sho rtade nticula te process slightly tw isted toward sthe posteriorprocess.Specimen s are identical to tho se illustr ated by PARI Set al.(1982:pis2: 12, 13,4:3,5,7 ,8)from the Rosan Formation of France.

On the basis of new material from the Kalkb ank limestone ofThuringia documenting theAmo rphog -nathu s ordov icicus Zone , FERRETTIand BAR NES(1997) were able to revi se the appa ratus reconstruction

of this spec ies. When compared to the Thuringian collec tio n (p I.4: 2- 3) and to unpublished materials

from Spain,the corresponding Pa elements fro m those two localities appea r slightly differentin havin g an outer-latera l process wh ich is approxima te ly perp end icular to the anter ior proce ss and, some times, denticulated .

One platform-like inco mplete poste rior process (PI. 2: 6) bears two convergent rows of denticles.S

ele me ntsare rare and badl y preserved .

Occurrence.- S. robu sta is known in the Late Ordovician of German y, Spain , France , Libya and

?Bohe mia.

Family

Icriodellidae

SWEET,

1988

GenusIcriodella RHODES, 1953

Type species:Icriodella superbaRHODES, 1953.

Icriodella sp.

(PI.2: 16, 17)

Remarks.- A sing le fragment ofa Pa anterior process with an oblique ridge connecting denticles and a poorly preserved ?Pb element are tentatively assigne d to thisgenus.

132 ANNALISA FERRETII

Family

Plectodinidae

SWEET,

1988

Genus Plectodina STAUFFER, 1935 Typespecies: Prioniodus aculeatusSTAUFFER,1930.

"Plectodina" aff.tenuis(BRANSON etMEHL, 1933) (PI. 1: 19)

aft.1975.Plectodina furcatatenuis (BRANSONet MEHL);SWEETet al.:p.42,pl.2:9-11,14-17.

1980.Plectodinaaff.tenuis (BRANSONet MEHL);ORCH ARD :p.23, pl. 2:6.

aft.1988.Plectodina tenuis (BRANSONet MEH L);NOWLANet al.:p.28,pl. 11:11,12,15.

Description.- A small "ozarkodiniform" Pa element in the early growth stage and a Pb fragment were recovered.The former (PI. 1: 19) has denticles that are strongly compressed laterally and are basally discrete.The basal cavity extends beneath the processes and flares almost symmetrically beneath the cusp. Anterior and posterior processes are sub-equal in length, the first being only slightly longer but bearing an equal number of denticles.

Remarks. - SimilarPaelements were reported as representing early small growth stages by ORCHARD (1980) in the Pusgillian of the north of England.The single Bohemian specimen was compared directly with early growth stages of the morphospecies "Ozarkodina alpina'' SERPAGLI, 1967 of the Carnic Alps collection. Anterior and posterior process are at about 1800

, a feature also observed in the Italian material,

even if with a certain variability. However, in the Italian material the anterior process, sometimes similar in dimension to the posterior process, always bears more denticles and, at least in adult forms,is definitely longer.

SWEET et al. (1975) distinguished within "Plectodina"fureata (HINDE, 1879) two contemporaneous but geographically separated subspecies: "P." fureata inclinata (GLENISTER, 1957) with the posterior process of"ozarkodiniform"elements "conspicuously shorter" than the anterior process and "P."fu reata tenuis(BRANsoNetMEHL, 1933) with the two processes being of "essentially the same length". In addition, the "trichonodelliforrn'' elements have respectively long, denticulated posterior processes or short ones lacking denticles or rarely bearing more than one or two small denticles. A third stock could have been represented by "P. "alpina (SERPAGLI, 1967), tentatively revised by SWEETand BERGSTROM(1984), whose "ozarkodiniforrn"element has an anterior process definitely longer than the posterior one and "trichono-delliform" element with short and adenticulate posterior process. Only further studies and additional collecting will clarify the relation between these species. Note that Early Silurian species included by SWEET (1988) in "Plectodina", i.e., "P." hassi (POLLOCKet al., 1970),and "P." oldhamensis(REXROAD,

1967), appear to have "ozarkodiniform" elements with an anterior process longer than the posterior one and "trichonodelliform" elements lacking a true posterior process (MCCRACKEN and BARNEs 1981).

Occurrence.- Middle-Late Ordovician of North America and Europe (Great Britain and Bohemia).

Order

Protopanderodontida

SWEET,

1988

Family

Protopanderodontidae

LINDSTROM,

1970

GenusProtopanderodus LINDSTROM, 1971 Type species:Acontiodusrectus L1NDSTROM,1955.

Protopanderodussp.

(PI. 2:20)

Remarks.- A single incomplete specimen having a pair of costae, with the anterior more pronounced, on a lateral face which i slightly concave anteriorly and then subplanar, and an acostate convex face. Anterior keel well developed and deflected at its base towards the inner side.

Genus Seabbardella ORCHARD, 1980 Type species:Drepanodusaltipes HENNINGSMOEN,1948.

Seabbardellaaltipes (HENNINGSMOEN, 1948)

(PI. 2: 10-12)

LATE ORDOVICIAN CONODONTS FROM THE PRAGUE BASIN, BOHEMIA 133

1980.Scabbardella altipes (HENNINGSMOEN);ORCHARD: p.25, pI. 5: 2-5, 7, 8, 12, 14, 18, 20, 23, 24, 28, 30, 33, 35, text-fig.4C.

1994.Scabbardella altipes (HENNINGSMOEN);DZIK:p.64,pI. 11:36-39,text-fig.6e. 1997.Scabbardella altipes(HENNINGSMOEN) ;FERRElTlandBARNES:p.34, pI. 1:17-22.

Remarks.- Scabbardella altipes is the dominant species in the Bohemian collection and is common in both the calcareous nodules and the Pemik Bed.

Occurrence.- Late Ordovician of Europe, Libya and North America.

Order unknown

Family unknown

Genuslstorinus KNUPFER, 1967

Typespecies: lstorinus erectusKNOPFER, 1967.

lstorinus erectus KNUPFER, 1967 (Pi. 2: 14)

1967.lstorinuserectus sp.n.;KNOPFER:p.31, pI. I: 4-6. 1967.lstorinuspostdentatus sp.n.;KNOPFER:p. 31,pI.1:10.

1967.lstorinusrecurvus sp.n.;KNOPFER: p.32,pI. 1: 7-9. 1967.Drepanodus disymmetricus sp.n.;KNOPFER:p.26, pI. 2:1-3.

1967.Drepanodus humilis sp.n.;KNOPFER:p.27,pI. 2:4-6.

1992.lstorinuserectusKNOPFER;BERGSTROMandMASSA:p.1338,pI. I:15, 16.

1997.lstorinuserectusKNOPFER;FERRElTl andBARNES:p. 34,pI. 5:13-20.

Remarks.- FERRETTI and BARNES (1997) found complete specimens of lstorinus erectus in the German Kalkbank limestone and recognized three main morphotypes. A single small element, with sharp anterior and posterior margins and bearing a denticle on one side of cusp occurs in the Pemik Bed.

Occurrence. - Late Ordovician of Germany,France, Spain, Libya and Bohemia. Genus Nordiodus SERPAGLI, 1967

Typespecies:NordiodusitalicusSERPAGLI, 1967.

Nordiodus italicus SERPAGLI, 1967 (Pi. 1: 18a, b)

1967.Nordiodus italicus sp.n.;SERPAGLI:p.77,pI. 19: 7a-12c. 1967.Nordiodusproclinatus sp.n.;SERPAGLI:p.78,pI. 19:la-6c. 1967."Oistodus"rhodesisp.n.;SERPAGLI :p.81,pI. 19:13a-18d.

1984.Nordiodus italicusSERPAGLI;SWEETandBERGSTROM :p.85.

Material. - A singlesmall, poorly preserved,M element is present. Occurrence. - Late Ordovician of Spain,Camic Alps and Bohemia.

"carniodiform" element (Pi. 2: 18, 19)

Remarks. - Small denticulated bars, sometimes slightly flexed,having a cusp in a sub-median position.

As no complete specimens are present, the morphological nomenclature is preferred, but this does not exclude the possibility that they may represent elements of Eocamiodusgracilis (ORCHARD, 1980).

Gen.etsp. indet. (Pi. 2: 21)

Remarks. - Incomplete element having a prominent triangular cusp, slightly flexed posteriorly. A costa runs laterally and extends into a lateral process. Posterior and anterior processes with three thin denticles oriented towardsthe cusp. Some of these features resemble those of S.cf. robusta,but denticles are here more slender and sharp and lateral processis denticulated.

134 ANNALISA FERRElTI

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136 ANNALISA FERRETII

LATE ORDOVICIAN CONODONTS FROM THE PRAGUE BASIN,BOHEMIA

PLATE I

Amorphognathu ssp. 131

1, 2.Oralviews ofPa element sIPUM 24964and IPUM 24965, samples B04and P2, bothx 120.

3-5.Outer-lateralviewsofPbelementsIPUM 24966,IPUM 24967, and IPUM 24968; samples K3,S3, and S3; x 135, x95, andx105 respectively.

6.Lateralview of Sa elementIPUM 24969;sampleB04; x 115.

7.Lateral view of Sb elementIPUM 24970;sample S2; x 150.

8,9. Lateral viewsof Se elementsIPUM 24971 and IPUM24972; samplesPB I and KI;both x125.

Amorphognathus aff. lindstroemi (SERPAGLI, 1967) 130

10.Posterior(a), anterolateral(b),and oral (c)viewsof M element IPUM 24973;sampleS3; x 195, x 195

andx215 respectively.

Hamarodus europaeus (SERPAGLI, 1967) 129

11.Lateralview of Pb element IPUM 24974; sample B03;x65.

12-14.Lateral views of Se elementsIPUM 24975,IPUM24976, and IPUM 24977;samples S2,B05, and B04; x 125,x95,andx 135 respectively.

15.Lateral view of Sb element IPUM 24978; sample S4; x 135.

16,17.Lateralviewsof M elementsIPUM 24979 and IPUM 24980;samplesP2 and K3;both x85. Nordiodus italicus SERPAGLI, 1967

18.Lateral views(a,b)of M element IPUM 24981;sample B04; x 165.

"Plectodina" aff. tenuis(BRANSONetMEHL, 1933)

19.Lateralview of Pa element IPUM 24982;sample S4;x 195.

133

138 ANNALISAFERRETII

LATE ORDOVICIANCONODONTS FROM THE PRAGUEBASIN,BOHEMIA

PLATE 2

Sagittod ontina cf.robusta KNOPFER, 1967 131

1-6.Lateral viewsofPaelements (PUM 24983, IPUM 24984,(PUM24985, IPUM 24986,(PUM 24987,and

(PUM 24988;samples S3, S3,S4, P2, P2, and P8 I; x 135, x 150, x 135, x 175,x 140, and x 165, respectively.

7, 8.Lateral viewsof Sbelements (PUM24989 and (PUM 24990;samples S3and P2;bothx 150.

Birksfeldi a?sp. . . .

9.LateralviewofPbelement(PUM 24991, sample S3.x 165.

131

Scabbardella altipes (HENNINGSMOEN, 1948) . . . 132

10-12.Lateral views of elements (PUM24992, (PUM 24993,and (PUM 24994;samples PI, 804,and 804;

x75,x80, andx 120respectively.

Hamarodu scf.europae us(SERPAGLI, 1967)

13.Lateral views (a,b) ofMelement IPUM24995;sample 804;x85.

Istorinus erectus KNOP FER, 1967

14.Lateral view of element (PUM 24996; sampleS4; x235.

Dapsilodu s mutatu s (BRANSON etMEHL, 1933)

15.Lateral viewofelement (PUM 24997; sample 803; x 170.

lcri odell a sp. . .

16.Lateral viewof?Pbelement (PUM 24998;sample PI;x95.

17.OralviewofPa element (PUM 24999;sampleS3;x 165.

"carniodiforrn" element

18,19.Lateral views of elements (PUM 25000 and (PUM 2500 I;samples 80 I and 804; x 220and x 95

respectively.

Protopanderodu ssp. . .

20.Lateralviewof element IPUM25002;sample K I;x65.

Gen.etsp.indet. .

21. Lateral viewof element (PUM 25003;sample 804;x 130.

130 133 130 131 133 132 133