silurian and lowermost devonian conodonts from...

237Bollettino della Società Paleontologica Italiana, 49 (3), 2010, 237-253. Modena, 15 dicembre 2010

ISSN 0375-7633

INTRODUCTION

In the Carnic Alps, one of the most complete Palaeozoic sedimentary successions in Europe is exposed at the Italian-Austrian border. Deposition was almost continuous from the Late Ordovician into the Permian. Silurian and lowermost Devonian sediments are irregularly distributed within the Carnic Alps, from the Monte Cocco area at the east, to Lake Wolayer at the west. In general, outcrops are quite small, mainly on the Italian side, with the exception of the Mt. Cocco and La Valute areas.

The sections presented in this paper are located just south of Lake Wolayer. The area is well known for the numerous outcrops of Upper Ordovician to Devonian sediments, which formed mainly in shallow water environments. Several other sections across the Silurian/Devonian boundary in the area have been studied: Rauchkofel Boden (Ferretti et al., 1999, and references therein), Costone Lambertenghi/Seekopf Sockel (Vai, 1963; Schönlaub, 1980), Valentin Torl (Vai, 1963; Histon et al., 1999, and references therein), Seewarte (Suttner, 2007). The famous Cellon section (Walliser, 1964), which can be considered the reference section for the Silurian, is located only a few kilometers to the east.

This paper reports on the conodont fauna from two new sections, Rifugio Lambertenghi Fontana and Rifugio Lambertenghi Fontana III, which crop out just south

of Passo Volaia (Fig. 1). Here about thirty meters of Orthoceras limestones of Pridoli and earliest Lochkovian age are exposed, which are characterized by extremely shallow-water sediments across the Silurian Devonian boundary.

THE SILURIAN AND LOWER DEVONIANIN THE CARNIC ALPS

Silurian and Lower Devonian deposits are irregularly distributed within the Carnic Alps, and range from shallow water bioclastic limestones to nautiloid-bearing limestones, interbedded shales and limestones to black graptolitic shales and cherts. The overall thickness does not exceed 60 m. The Silurian transgression started at the base of the Llandovery, and, owing to the disconformity separating the Ordovician and the Silurian, a varying of sediments is locally missing, which corresponds to several conodont zones of Llandovery to Ludlow age (Histon & Schönlaub, 1999).

The Silurian and lowermost Devonian of the Carnic Alps is subdivided into four lithofacies associations representing different depths of deposition and hydrodynamic conditions (Wenzel, 1997). The Wolayer-facies is characterised by proximal shelf sediments and the Bischofalm-facies by deep water deposits; the Plöcken-

Silurian and lowermost Devonian conodonts from the Passo Volaia area (Carnic Alps, Italy)

Carlo Corradini & Maria G. Corriga

Carlo Corradini, Dipartimento di Scienze della Terra, Università di Cagliari, via Trentino 51, I-09127 Cagliari; [email protected] G. Corriga, Dipartimento di Scienze della Terra, Università di Cagliari, via Trentino 51, I-09127 Cagliari; [email protected]

KEY WORDS - Silurian/Devonian boundary, Conodonts, Biostratigraphy, Taxonomy, Carnic Alps.

ABSTRACT - Two sections (Rifugio Lambertenghi Fontana - RLF - and Rifugio Lambertenghi Fontana III - RLF III) of the Orthoceras limestones that crop out just South of Passo Volaia in the Carnic Alps yielded a rich and diverse conodont fauna. Twenty-six taxa belonging to eleven genera (Belodella, Coryssognathus, Dapsilodus, Dvorakia, Icriodus, Oulodus, Ozarkodina, Panderodus, Pseudooneotodus, Wurmiella and Zieglerodina) were discriminated. Wurmiella alternata n. sp. is described, and Belodella coarctata, Dvorakia amsdeni and Zieglerodina zellmeri are reported for the first time from the Carnic Alps. The fauna allows recognition of five late Silurian-earliest Lochkovian conodont zones (snajdri, crispa, eosteinhornensis s.l., detortus and woschmidti). The Silurian/Devonian boundary is interpreted to occur in the upper part of the RLF III section.

RIASSUNTO - [Conodonti del Siluriano e Devoniano basale nell’area di Passo Volaia (Alpi Carniche, Italia)] - Nelle Alpi Carniche affiora una delle più complete sequenze paleozoiche pre-erciniche d’Italia, costituita da successioni sedimentarie debolmente metamorfiche di età compresa tra l’Ordoviciano Sup. e il Carbonifero. Le rocce del Siluriano e del Devoniano basale affiorano in modo discontinuo e, soprattutto nel versante italiano, gli affioramenti non sono molto estesi.

Immediatamente a sud del Passo Volaia, situato nella parte occidentale delle Alpi Carniche, affiorano una quarantina di metri di calcari a Orthoceras depositatesi in un mare poco profondo. L’associazione faunistica è dominata da crinoidi, brachiopodi, cefalopodi, con associati più rari bivalvi e trilobiti. Qui sono state misurate e campionate due sezioni a conodonti, denominate rispettivamente “Rifugio Lambertenghi Fontana (RLF)” e “Rifugio Lambertenghi Fontana III (RLF III)”. La ricca fauna a conodonti raccolta (circa quattromila elementi) comprende ventisei taxa appartenenti a undici generi (Belodella, Coryssognathus, Dapsilodus, Dvorakia, Icriodus, Oulodus, Ozarkodina, Panderodus, Pseudooneotodus, Wurmiella e Zieglerodina), che hanno consentito di riconoscere le ultime quattro biozone del Siluriano (snajdri, crispa, eosteinhornensis s.l. e detortus) e la prima del Devoniano (woschmidti). Il limite Siluriano/Devoniano è localizzato nella parte alta della sezione RLF III. Tre specie (Belodella coarctata Barrick & Klapper, Dvorakia amsdeni Barrick & Klapper e Zieglerodina zellmeri Carls et al.) sono segnalate per la prima volta nelle Alpi Carniche; inoltre, viene descritta la nuova specie Wurmiella alternata n. sp.

238 Bollettino della Società Paleontologica Italiana, 49 (3), 2010

facies and the Findenig-facies represent intermediate facies associations.

The pattern of depositional lithofacies suggests an overall transgressive regime from the Llandovery through the Ludlow. Uniform limestone sedimentation during the Pridoli indicates that more stable conditions were developed at that time (Schönlaub, 1997).

For a more detailed description of the Silurian of the Carnic Alps refer to Histon & Schönlaub (1999) and Schönlaub & Histon (2000).

GEOLOGICAL SETTING

The region around Passo Volaia is one of the better studied area of the Carnic Alps because of the variety of facies represented in Upper Ordovician to Upper Devonian strata, which were deposited either in relatively shallow or deep water environments, for the quality of the outcrop exposures, and the abundant fossils.

The Silurian and lowermost Devonian sequence is represented here by shallow water sediments of the “Wolayer facies” (Wenzel, 1997). The sequence starts with about 15 m of middle Wenlock to Ludlow highly fossiliferous neritic Orthoceras limestones (neritic equivalent of the Kok Formation; Schönlaub, 1997), which disconformably overlie the Upper Ordovician crinoidal Wolayer Limestone. Nautiloid cephalopods, bivalves, brachiopods and trilobites are abundant; in some levels microstromatolites are evident in the lower part of the unit (Histon & Schönlaub, 1999), as well as ooidal ironstones (Ferretti, 2005).

The overlying Cardiola Formation (Ludlow) is represented by a very thin level of dark limestone rich in cephalopods and bivalves. The overlying sequence comprises up to 30 m of fine grey micritic limestone (Alticola limestone Auct. + Megaerella limestone Auct.) with abundant bioclasts and nautiloids and a fossiliferous content similar to the neritic Kok Formation (Histon & Schönlaub, 1999). In the Rauchkofel Boden section (Schönlaub, 1970; Ferretti et al., 1999 and references herein) the base of the Devonian is marked by a Scyphocrinites bed at the top of the unit.

The lowermost Devonian is represented by more of 100 m of very shallow water sediments of the “neritic Rauchkofel Formation Auct.” (grey crinoidal limestone, rich of bioclasts) or deeper water well bedded dark grey limestones of the “Pelagic Rauchkofel Formation”.

STUDIED SECTIONS

Two sections were measured and sampled for conodonts a few tens of meters south of Passo Volaia and the state boundary (Fig. 2). They have been designated the Rifugio Lambertenghi Fontana (RLF) and Rifugio Lambertenghi Fontana III (RLF III) sections, respectively. Although the two sections are very close each other, in the field it is difficult to correlate them precisely because of the topography of the area, the dip of the strata and effects of trench construction from the First World War. Based on field correlations, they do not overlap for a few tens of centimetres, with top of the RLF section slightly older than the bas of the RLF III section. Conodont data confirm this correlation.

Fig. 3 - Panoramic view of the Rifugio Lambertenghi Fontana Section, with location of samples. Samples from 7 to 10 have been collected in a World War I cave, where beds are well exposed and precisely correlated with beds outside.

Fig. 1 - Location map of the studied area (asterisk) within the Carnic Alps.

Fig. 2 - Aereal view (Immagine TerraItaly™ - © Blom CGR) of the Passo Volaia area with location of the studied sections.

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Fig. 4 - Stratigraphic log of the Rifugio Lambertenghi Fontana section, with occurrence of main conodont taxa and conodont abundance.

The Rifugio Lambertenghi Fontana (RLF) sectionThe Rifugio Lambertenghi Fontana section is located

on along the path to Rifugio Lambertenghi Romanin, at

coordinates N 46°26’22.6” E 12°52’07.8”, more or less where a fountain is placed (Figs. 2-3). About 18 m of Orthoceras limestone are here exposed (Fig. 4).

C. Corradini, M.G. Corriga - Silurian and Lower Devonian conodonts from the Carnic Alps


The section starts with about three meters of highly fossiliferous reddish limestones, where fossil remains are mainly represented by crinoids, brachiopods, cephalopods and bivalves, often fragmented and packed together at the centimeter scale. A covered interval corresponding to a World War I trench is present in the lower part of the section.

The central part of the section comprises grey micritic limestone rich in orthoceratid nautiloids; concentrations of small crinoidal debris are observable in some levels, as well as a few brachiopod casts. The fossiliferous content strongly decreases above sample RLF 6 and only a few poorly preserved cephalopods occur in the upper part of the section, where the colour of the rock frequently grades to red due to weathering. A mineralized horizon, bearing hematite and limonite, occurs just above sample RLF 9.Sixteen conodont samples were collected from the Rifugio Lambertenghi Fontana section.

The Rifugio Lambertenghi Fontana III (RLF III) sectionThe Rifugio Lambertenghi Fontana III section is

located along the path from Rifugio Lambertenghi Romanin to Mt. Capolago, at coordinates N 46°26’22.7”, E 12°52’05.4” (Figs. 2, 5). More than 15 meters of limestone crop out in a World War I trench, immediately west of the path. The section is subdivided into two parts, 5 and 10.5 m thick respectively, separated by a covered interval about 10 m thick (Figs. 5a, 6).

The lower part of the section, up to sample RLF III 3A, is represented by grey micritic limestone, with a sparse crinoid remnants and scattered rare brachiopods.

The upper part is much more fossiliferous, and the fossil content increases toward the top of the section. However, the state of preservation of the fauna is poor. Crinoids are always abundant and brachiopods often present, in places concentrated in centimeter-thick shelly levels. The fauna includes bivalves, nautiloid cephalopods, rare trilobites and solitary corals. In the uppermost part of the section, above sample RLF III 2, bedding planes are difficult to observe, due to heavy weathering and fracturing of the rocks.

Twenty-eight conodont samples were collected from the Rifugio Lambertenghi Fontana III section, with greater detail in the upper part of the section, across the S/D boundary (Fig. 5b-6).

CONODONT DATA

A total of forty-four samples from the two sections were processed with conventional formic acid technique. More than ninety kilograms of limestone yielded about 3900 conodont elements (Tabs. 1-2). The state of preservation is generally quite good, even if a few elements are broken. Conodont colour is dark brown, corresponding to a Colour Alteration Index (CAI) of 4.

The abundance is variable, from almost 200 elements/kg to barren samples. In the lower part of the RLF section (snajdri and crispa zones), the average is around 30 elements/kg and rises in the upper part up to 192 elements/kg in sample RLF 9 (Fig. 4). Frequencies are high also in the lower part of the RLF III section (Fig. 6), up to sample RLF III 2B, with an average of 60 elements/kg.

It suddenly decreases to values of around 25, with a last peak of 73 elements/kg in sample RLF III 1N. Above this level, abundance is very low with only a few elements/kg up to the top of the section; samples RLF III 1R and RLF III 0 were barren.

Twenty-six taxa belonging to eleven genera (Belodel-la, Coryssognathus, Dapsilodus, Dvorakia, Icriodus, Oulodus, Ozarkodina, Panderodus, Pseudooneotodus, Wurmiella and Zieglerodina) were identified. Among them Belodella coarctata Barrick & Klapper, Dvorakia amsdeni Barrick & Klapper and Zieglerodina zellmeri Carls et al. are reported for the first time from the Carnic Alps, and Wurmiella alternata n. sp. is described.

Elements of ozarkodinids are abundant throughout the sections, representing about two-thirds of the whole fauna. Coniforms (mainly Dapsilodus and Panderodus) and Belodella are constantly present and especially abundant in some samples of the snajdri Zone (i.e. RLF 3, RLF 5).

BIOSTRATIGRAPHY

The biozonation schemes followed in this paper are those proposed by Corradini & Serpagli (1999) and updated by Corriga & Corradini (2009) for the Silurian, and by Carls & Weddige (1996) for the Lower Devonian. The conodont faunas allow recognition of five conodont zones in the Rifugio Lambertenghi Fontana and Rifugio Lambertenghi Fontana III sections: snajdri, crispa, eosteinhornensis s.l. and detortus zones in the Silurian and the woschmidti Zone in the Devonian.

The snajdri Interval ZoneAccording to Corradini & Serpagli (1999), the lower

and upper boundary of this interval are defined by the

Fig 5 - a: Panoramic view of the Rifugio Lambertenghi Fontana III Section, with approximate location of selected samples; b: detailed view across the Silurian/Devonian Boundary.

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LO (Last Occurrence) of Pe. latialata and the FO (First Occurrence) of Oz. crispa, respectively. Therefore, it is possible to attribute the lower part of the RLF section to the snajdri interval Zone. Dapsilodus obliquicostatus is

dominant in sample RLF 1, whereas Belodella is very abundant in sample RLF 3: similar abundances of these taxa in the snajdri Zone occur also in Cellon and Monte Cocco II sections (Corriga & Corradini, 2009).

Fig. 6 - Stratigraphic log of the Rifugio Lambertenghi Fontana III section, with occurrence of main conodont taxa and conodont abundance.



The crispa ZoneOz. crispa occurs in sample RLF 6 only. However, the

occurrence of Oz. eosteinhornensis s.l. in sample RLF 5 allows reference of this level to the crispa Zone. In fact, the latter species has its first occurrence within this zone (Corradini & Serpagli, 1999), or even at the base of the zone together with Oz. crispa, like in Bohemia (Muslovska Quarry and Kolednik Quarry; Chlupac et al., 1980).

The eosteinhornensis s.l. Interval ZoneThe eosteinhornensis s.l. Interval Zone is distinguished

in the upper part of the RLF section, from sample 6A to 10, because the lower boundary is defined by the LO of Oz. crispa, and the upper boundary by the FO of Oulodus el. detortus. Wurmiella alternata n. sp. appears slightly above the base of the zone. Elements of Wurmiella excavata dominate at all the levels of this interval.

The detortus ZoneThe detortus Zone can be recognized in the upper

part of the RLF section and in the most of the RLF III

section, from the base to around sample RLF III 1K. The lower boundary is defined by the FO of Oulodus elegans detortus, whereas the upper boundary is difficult to locate precisely because of the very low conodont abundance in the upper part of the RLF III section. For notes on the Silurian/Devonian boundary position (and of the upper boundary of this zone) see the next chapter.

Wurmiella alternata occurs in the lower part of the zone, up to sample RLF III 3B; Oz. eosteinhonensis s.s. is limited to sample RLF 4, where Oz. snajdri has its only occurrence at an unusually high stratigraphic level. Elements of Wurmiella excavata dominate, except in samples from RLF III 2C to 2X, where Panderodus unicostatus is very abundant, as does Belodella anomalis in sample RLF III 2B.

The woschmidti ZoneThe base of the zone is marked by the FO of Icriodus

woschmidti or Icr. hesperius. In the RLF III section Icr. hesperius occurs only in the uppermost part, in sample RLF III 1. However, the lower boundary of the zone can

RLF 1 2 3 4 5 6 6A 6B 7 7A 8 8A 9 10 11 12 total

Belodella anomalis

S0 5 2 1 1 9S1 2 2S2 1 1S3 1 1 2

T 1 1

Belodella coarctata S0 2 4 1 7T 1 1

Belodella resimaS1 1 1 22 23 2 1 2 2 54S2 1 1 3 5

T 1 3 4Dapsilodus obliquicostatus 52 2 8 5 7 10 1 2 4 1 5 2 1 1 101

Dvorakia amsdeni S1 1 1 2S2 1 1

Dvorakia sp. 1 1

Oulodus elegans elegans

P1 1 4 5M 1 1

S0 1 1 2S1 3 1 4S2 1 2 2 2 7

Oulodus elegans detortus M 1 1

Oulodus sp. S1 1 1S2 1 1

Ozarkodina confluens P1 1 2 1 1 5P2 1 1 2

Ozarkodina crispa P1 3 3P2 1 1

Ozarkodina eosteinhornensis s.l.

P1 1 3 5 4 11 5 29P2 2 1 2 1 1 1 8S0 1 1S1 1 1S2 1 2 1 4

Panderodus recurvatus 2 1 3 2 2 8 2 2 3 7 4 3 39Panderodus unicostatus 5 1 1 2 10 3 2 2 2 18 5 51

Wurmiella alternata

P1 2 1 14 1 18P2 1 1 1 13 2 18M 1 2 1 4

S0 1 4 5S1 1 3 1 5S2 1 2 1 4

Wurmiella excavata

P1 3 6 10 19 12 4 61 4 67 187 19 148 33 38 40 651P2 6 7 2 3 17 4 9 21 6 52 7 5 139M 2 1 1 7 1 1 4 3 5 14 2 37 15 3 4 100

S0 1 1 3 1 1 11 3 3 8 3 31 17 2 4 89S1 1 1 8 1 2 6 3 8 41 9 63 36 5 2 186S2 1 3 10 4 12 4 8 15 17 28 33 17 132 3 2 4 293

Zieglerodina zellmeri P1 1 1 2P2 1 1

Zieglerodina sp. P1 3 3P2 1 1

Indetermined ozarkodinids P1 1 1 3 1 1 1 8P2 1 1 1 3

Indetermined ramiforms 1 1 1 3Fragments 1 3 3 8 8 4 8 48 40 30 74 43 45 48 37 24 424Total 67 24 66 37 119 53 33 180 88 174 421 111 589 172 90 90 2314kg. rock 2,15 2,20 2,06 2,76 2,48 2,80 2,70 2,44 2,21 3,19 2,99 2,63 3,05 2,45 2,93 2,82 41,86conodonts/kg 31,2 10,9 32,0 13,4 48,0 18,9 12,2 73,8 39,8 54,5 140,8 42,2 193,1 70,2 30,7 31,9 55,3

Tab. 1 - Distribution of conodonts in the Rifugio Lambertenghi Fontana section.

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be placed around sample RLF III 1K, just above the first occurrence of Zieglerodina remscheidensis (see below for comments). As already pointed out, conodonts are quite rare in this part of the section.

COMMENTS ON THE POSITION OF THE SILURIAN/DEVONIAN BOUNDARY

It is difficult to precisely locate the Silurian/Devonian Boundary in the Rifugio Lambertenghi Fontana III section, owing to the scarcity of the fauna in the upper part of the section. In fact, there is a wide biostratigraphic gap between the last occurrence of Ozarkodina confluens

(= Oz. typica sensu Murphy et al., 2004), which is limited to Silurian, and the first occurrence of Icriodus hesperius, an index taxon for the basal Devonian, which occurs only at very top of the section. However, other taxa can be of help, especially Zieglerodina remscheidensis.

Genus Zieglerodina was recently proposed by Murphy et al. (2004) to include the ozarkodinids of the “remscheidensis Group” and included several different forms previously put together in only one species (Ozarkodina remscheidensis Ziegler). In their revision Murphy et al. (2004) restricted the diagnosis of Z. remscheidensis to morphs very similar to the holotype of Ziegler (1960, pl. 13, fig. 4) and Carls et al. (2007) introduced three new species to discriminate forms from

RLF III 5 4 3D 3C 3B 3A 3 2C 2B 2Y 2X 2A 2 1N 1W 1M 1K 1L 1B 1P 1X 1A 1R 1Y 1S 1Z 1 0 total

Belodella anomalis

S0 1 3 23 3 1 2 1 1 5 10 1 2 53S1 2 2S2 5 3 8S3 13 1 1 1 16

T 1 1Belodella coarctata S0 1 4 1 6

Belodella resimaS0 1 1S1 1 1 9 4 2 3 1 2 23S2 1 1

Coryssognathus dubius S0/S1 3 3S2 1 1 2

Dvorakia amsdeni S3 4 4Dvorakia sp. 3 2 1 1 7Dapsilodus obliquicostatus 1 1 4 2 1 1 10

Icriodus hesperius P1 1 1M 1 1

Oulodus elegans elegans

P1 1 1 1 3P2 1 1 2M 1 1

S0 1 1 1 1 1 5S1 1 1 1 1 2 1 1 8S2 2 1 1 1 1 1 7

Oulodus greilingi hirpex Pa 1 1Sc 1 1

Oulodus siluricus

P1 1 1M 1 1

S0 1 1S1 1 1

Oulodus sp. S0 1 1 2S2 1 1

Ozarkodina confluens P1 1 1 1 3P2 2 2

Ozarkodina eosteinhornensis s.s. P1 1 1

Ozarkodina eosteinhornensis s.l.P1 5 1 1 1 5 1 2 1 1 18P2 1 1S2 1 1 2

Ozarkodina planilingua P1 1 1 2 1 5Ozarkodina snajdri P1 3 3Ozarkodina sp. P1 1 1 1 1 4Panderodus recurvatus 4 1 3 1 7 1 3 1 2 4 27Panderodus unicostatus 3 7 8 5 7 22 6 3 35 20 23 18 21 29 3 31 2 3 6 252Pseudooneotodus beckmanni 1 2 1 4

Wurmiella alternata

P1 4 4P2 1 6 7M 4 4

S0 1 1S1 4 4S2 5 5

Wurmiella excavata

P1 35 119 5 40 27 46 135 2 6 2 1 10 18 6 452P2 12 29 14 6 10 45 1 1 1 4 123M 3 19 1 3 1 2 32 2 3 8 4 1 79

S0 5 15 2 1 2 3 23 2 1 1 3 58S1 1 26 2 5 5 11 31 1 1 2 7 3 1 96S2 8 28 4 6 7 35 2 1 3 7 15 11 1 128

Wurmiella sp. P1 1 1 2

Zieglerodina remscheidensis

P1 1 2 3 2 3 2 3 4 2 22P2 3 1 3 4 11M 1 1

S0 1 1 2S1 1 1 2 4S2 1 1 1 3

Indetermined ramiforms 1 1 1 1 4Fragments 11 20 9 9 8 12 36 1 7 2 2 5 2 2 1 1 3 2 6 2 1 1 8 151Total 83 283 35 92 93 124 352 11 113 38 30 56 81 88 2 5 2 51 20 6 7 34 0 2 9 7 33 0 1657kg. rock 1,33 2,93 1,20 2,20 1,70 1,78 3,20 1,40 1,60 1,80 1,30 2,20 2,76 1,20 2,80 1,80 2,00 2,90 2,28 1,85 1,80 2,67 1,39 1,30 1,60 1,60 2,48 1,80 51,74conodonts/kg 62,4 96,6 29,2 41,8 54,7 69,7 110 7,9 70,6 21,1 23,1 25,5 29,3 73,3 0,7 2,8 1,0 17,6 8,8 3,2 3,9 12,7 0,0 1,5 5,6 4,4 13,3 0,0 32,0

Tab. 2 - Distribution of conodonts in the Rifugio Lambertenghi Fontana III section.



the Pridoli (Z. klonkensis, Z. ivochlupaci and Z. zellmeri). We agree on this approach and we believe that other species of Zieglerodina are still to be described from the latest Silurian. Murphy et al. (2004) and Carls et al. (2007) claim that Z. remscheidensis is limited to lowermost Devonian, on the basis of the occurrence of the species in the type locality (Ziegler, 1960), but it is present at the very top of the Pridoli either in other Carnic Alps sections (i.e. Monte Cocco II section; Corriga & Corradini, 2009) or in other palaeogeographic regions (Sardinia; Corriga et al., 2009a).

In the RLF III section, Z. remscheidensis enters in sample RLF III 1M, just above the last occurrence of Oz. confluens. Wurmiella excavata is present up to sample RLF III 1L. This species is usually abundant in the Silurian, but suddenly disappears just below the S/D boundary in the Monte Cocco II section (Corriga & Corradini, 2009), where the facies is similar to that of the Rifugio Lambertenghi Fontana III section. Therefore, on the basis of conodont occurrences, the S/D boundary can tentatively be placed around sample RLF III 1L.

This is supported also by preliminary Carbon isotope data (Corriga et al., 2009b), which suggest to locate the S/D boundary in the upper part of the prominent δ13C shift, and just before the δ13C values reach their maximum (Fig. 7). This basal Devonian “plateau”-like peak in the carbon curve is known also from the Prague Basin (Buggisch & Mann, 2004, fig. 2). The characteristic shift in δ13C starts

in the latest Pridoli and the position of the S/D boundary within the rising limb of the carbon peak is documented from different peri-Gondwana locations (Buggisch & Mann, 2004), Laurentia (Saltzman, 2002; Jacobi et al., 2009) and south Baltica (Malkowski et al., 2009).

SYSTEMATIC PALAEONTOLOGY

Systematic notes are restricted to necessary taxonomic remarks and to taxa newly documented from the Carnic Alps. For suprageneric classification, the scheme proposed by Sweet (1988) is followed. Synonymy lists are limited to main captions and previous illustrations of specimens from the Carnic Alps. The entire fauna is housed in the Earth Sciences Department, University of Cagliari (DSTC), under numbers 30000-30115. Horizon and catalogue numbers of figured specimens are given in the plate captions.

Phylum Chordata Bateson, 1886Class Cavidonti Sweet, 1988

Order Belodellida Sweet, 1988Family Belodellidae Khodalevich & Chernikh, 1973

Genus Belodella Ethington, 1959

Type species - Belodus devonicus (Stauffer, 1940)

Belodella coarctata Barrick & Klapper, 1992(Pl. 1, fig. 6)

1992 Belodella coarctata n. sp. BarriCk & klapper, p. 42-43, Pl. 2, figs. 3-4, 8-9, 12-14 (cum syn.).

Remarks - The specimens referred to this species fits perfectly the original diagnosis. This is the first report of B. coarctata from the Carnic Alps.

Stratigraphic distribution - The species is documented from the Ludlow (Jeppsson, 1989) to the Pridoli (Barrick & Klapper, 1992). In Klonk it is very abundant just below the S/D boundary (Jeppsson, 1989). One of our specimens comes from the very base of Devonian.

Studied material - 13 S0 and 1 T elements from samples RLF 2, 5, 8, 9 and RLF III 2C, 1L, 1S.

Genus Dvorakia Klapper & Barrick 1983

Type species - Dvorakia chattertoni Klapper & Barrick 1983

Dvorakia amsdeni Barrick & Klapper, 1992(Pl. 1 fig. 12-13)

1992 Dvorakia amsdeni n. sp. BarriCk & klapper, p. 43-44, Pl. 2, figs. 11, 15-19.

Remarks - The specimens referred to this species fit the original description by Barrick & Klapper (1992) from

Fig. 7 - Detail of the stratigraphic log of the RLF III section around the Silurian/Devonian boundary, with Carbon isotope data (after Corriga et al., 2009b) and occurrence of conodont taxa useful to locate the Silurian/Devonian boundary.

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the south-central U.S.A. The lack of ornamentation on the surfaces, the broad keel and the inner anterolateral costa distinguish D. amsdeni from the other species of the genus. This is the first report of D. amsdeni from the Carnic Alps.

Stratigraphic distribution - The species is documented in the Pridoli (Barrick & Klapper, 1992).

Studied material - 2 S1, 1 S2 and 4 S3 elements from samples RLF 9, 12 and RLF III 2B.

Class Conodonti Branson, 1938Order ozarkodinida Dzik, 1976

Family Spathognathodontodae Hass, 1959

Genus Ozarkodina Branson & Mehl, 1933

Type species - Ozarkodina confluens Branson & Mehl, 1933

Remarks - The Genus Ozarkodina was recently subdivided in several new genera by Murphy et al. (2004) and Carls et al. (2005). We agree that in the previous meaning Ozarkodina included several different groups that may represent separate genera, but in our opinion not everything fits well in their scheme. Wurmiella was proposed to include taxa related to “excavata Group”, while Zieglerodina is the new generic name for the “remscheidensis Group”. These subdivisions seem to be valid and the names are accepted, apart from some possible nomenclature problems highlighted by Donoghue et al. (2008). For notes on the “eosteinhornensis Group” see the remarks on genus Zieglerodina. Murphy et al. (2004) and Carls et al. (2005) restricted the diagnosis of Ozarkodina, based on Oz. confluens Branson & Mehl (= Oz. typica sensu Murphy et al., 2004), including some Silurian taxa, but left several other species without a generic assignment. We do not accept this restricted diagnosis, at least until a comprehensive revision of the ozarkodinids has been completed, in order not to expand the taxonomic uncertainty generated by their partial revision. We recognize that Ozarkodina remains a polyphyletic genus, but we believe that stability in nomenclature should be maintained until a revision will be concluded.

Ozarkodina crispa (Walliser, 1964)(Pl. 3, fig. 20-21)

1964 Spathognathodus crispus WalliSer, p. 74-75, Pl. 9, fig. 3; Pl. 21, figs. 7-13.

1989 Ozarkodina crispa (Walliser) - WalliSer & Wang, p. 114-119, Pl. 1, figs. 1-16; text-fig. 1.

2003 Ozarkodina crispa (Walliser) - Corradini et al., pl. 1, figs. 6-7.

2009 Ozarkodina crispa (Walliser) - Corriga & Corradini, p. 114-119, figs. 4 G-H.

2010 Ozarkodina crispa (Walliser) - Wang & aldridge, p. 88, Pl. 22, figs. 9-10, 13-14 (only).

2010 Ozarkodina crispa (Walliser) - Corradini et al., fig. 3g.

Description - For the Pa element, see Walliser & Wang (1989). Pb element ozarkodiniform very stout,

with an evident shoulder in both side of the process. The cusp is high, prominent, strong, posteriorly inclined and with a triangular outline. The anterior process is short and decreases in height towards the distal end; it bears three well spaced triangular denticles of equal size. The posterior process bears five triangular discrete denticles; the last three slightly larger than the others. The basal cavity is deep and wide under the cusp, where is laterally limited by a prominent rim, and progressively tapers up to the distal end of processes.

Remarks - The apparatus of Oz. crispa is still unknown, and was tentatively reconstructed by Helfrich (1975) as “Group X”, and by Wang & Aldridge (2010). Both these reconstructions were done on the basis of joint occurrence of elements in some samples, but it looks that the various specimens figured as representative of the same element in the apparatus are different and, therefore, may belong to different taxa. The P2 element here described is from a sample (RLF 6) where, beside P1 elements of Oz. crispa, the only other ozarkodinids are W. excavata and Oz. confluens.

Walliser & Wang (1989) distinguished four morpho-types of the Pa element, based on the occurrence and morphology of a furrow at the oral margin. The Pa elements from RLF section belongs to β morphotype.

Stratigraphic distribution - The species is the marker of the crispa Zone and is limited to this interval (Corradini & Serpagli, 1999).

Studied material - 3 P1, 1 P2, from sample RLF III 6.

Genus Wurmiella Murphy, Valenzuela-Rios & Carls, 2004

Type species - Ozarkodina excavata tuma Murphy & Matti, 1983

Remarks - Genus Wurmiella was recently proposed by Murphy et al. (2004) to include the ozarkodinids of the “excavata Group”.

Wurmiella alternata n. sp.(Pl. 2, figs. 1-8)

1986 Ozarkodina excavata excavata (Branson & Mehl) - MaWSon, pl. 4, figs. 3, 5-7, 12, 16, 19, 21-22 (only).

1994 Ozarkodina excavata excavata (Branson & Mehl) - MaWSon & talent, figs. 13 E, G-H (only).

2004 Ozarkodina excavata (Branson & Mehl) - Farrell, pl. 9, figs. 3.

2007 Ozarkodina excavata ssp. Suttner, p. 37, pl. 12, fig. 2.2007 Unassigned specimen Suttner, pl. 12, fig. 4.

Holotype - DSTC 30000/1-6 figured in Pl. 2, figs. 1-6.

Paratypes - Figured specimens DSTC 30001 and DSTC 30002; not figured specimens DSTC 30003/1-3, 30004/1-3, 30005/1-4, 30006/1-30, 30007/1-5, 30008, 30009, 30010/1-24.



Locus Typicus - Rifugio Lambertenghi Fontana section, just south of Passo Volaia and Rifugio Lambertenghi Romanin, Carnic Alps, Italy.

Stratum Typicum - Bed of sample RLF 9.

Derivatio nominis - From Latin alternatus, because of the characteristic denticulation pattern.

Diagnosis - A species of Wurmiella with some adjacent denticles of different size in all elements of the apparatus.

Description – Apparatus composed by six elements: P1, P2, M, S0, S1, S2.

P1 element spathognathodiform, straight and thin with upper and lower margins more or less parallel. The subtriangular cusp is only slightly larger than the denticles; denticles are closely spaced and of different size on both processes, with smaller denticles intercalated within larger ones. Usually the posterior process bears 4 or 5 denticles and the anterior process bears 8 or 9 denticles. The small basal cavity is located slightly posterior.

P2 element ozarkodiniform with an angle of about 120° between the processes. The cusp is large, high,

subtriangular, laterally compressed and posteriorly reclined, with a well developed keel on its anterior margin. The strong anterior process bears up to ten closely spaced denticles of different size. The posterior process is longer and thinner and bears up to nineteen small and closely spaced denticles. The basal cavity is larger under the cusp and becomes thinner below the processes.

M element neoprioniodiform. The cusp is high, robust laterally compressed. The posterior process is bent downward and bears small, normally alternated, denticles. A single denticle could be present anterior of the cusp. The basal cavity is wider beneath the cusp on the inner side an continues as a groove towards the posterior margin.

S0 element trichonodelliform with an angle of about 160° between the symmetrical lateral processes. Processes bear small closely spaced denticles. The cusp is high and strong. The basal cavity is narrow under and anterior of the cusp and continues as a groove below the processes.

S1 element plectospathodiform, with two asymmetrical processes. The posterior process has an undulating lower margin and bears several denticles alternating in size; denticles close to the cusp are smaller than the others. The anterior process is shorter and bears up to ten closely spaced equal denticles. The cusp is high, strongly reclined

EXPLANATION OF PLATE 1

Figs. 1-3, 5 - Belodella anomalis Cooper, 1974. 1 - DSTC 30028; lateral view of S0 element; sample RLF III 2B, detortus Zone; 2 - DSTC 30029; lateral view of S3 element; sample RLF III 2B, detortus Zone; 3 - DSTC 30030; lateral view of S2 element; sample RLF III 2B, detortus Zone; 5 - DSTC 30032; lateral view of S0 element; sample RLF III 3A, detortus Zone.

Fig. 4 - Belodella resima (Philip, 1956). DSTC 30031; lateral view of S1 element; sample RLF III 2B, detortus Zone.

Fig. 6 - Belodella coarctata Barrick & Klapper, 1992. DSTC 30033; lateral view of S0 element; sample RLF III 1L, woschmidti Zone.

Fig. 7 - Dapsilodus obliquicostatus (Branson & Mehl, 1933). DSTC 30034; lateral view; sample RLF 1, woschmidti Zone.

Figs. 8-11 - Coryssognathus dubius (Rhodes, 1953). 8 - DSTC 30035; lateral view of S2 element; sample RLF III 2B, detortus Zone; 9 - DSTC 30036; lateral view of S0/S1 element ; sample RLF III 2B, detortus Zone; 10 - DSTC 30037; lateral view of S0/S1 element; sample RLF III 2B, detortus Zone; 11 - DSTC 30038; lateral view of S0/S1 element; sample RLF III 2B, detortus Zone.

Figs. 12-14 - Dvorakia amsdeni Barrick & Klapper, 1992. 12 - DSTC 30039; lateral view of S3 element; sample RLF III 2B, detortus Zone; 13 - DSTC 30040; lateral view of S2 element; sample RLF 9, eosteinhornensis s.l. Zone; 14 - DSTC 30041; lateral view of element S1; sample RLF 10, eosteinhornensis s.l. Zone.

Figs. 15-18 - Panderodus recurvatus (Branson & Mehl, 1933). 15 - DSTC 30043; lateral view;sample RLF 2B, detortus Zone; 16 - DSTC 30044; lateral view; sample RLF 2Y, detortus Zone; 17 - DSTC 30042; lateral view; sample RLF 2X, detortus Zone; 18 - DSTC 30045; lateral view; sample RLF 7, eosteinhornensis s.l. Zone.

Figs. 19-20 - Panderodus unicostatus (Branson & Mehl, 1933). 19 - DSTC 30046; lateral view; sample RLF 9, eosteinhornensis s.l. Zone; 20 - DSTC 30047; lateral view; sample RLF 7, eosteinhornensis s.l. Zone.

Fig. 21 - Pseudooneotodus beckmanni (Bischoff & Sannemann, 1958). DSTC 30048; lateral view; sample RLF III 2B, detortus Zone.

Fig. 22 - Icriodus hesperius? Klapper & Murphy, 1975. DSTC 30049; upper view of a broken P1 element; sample RLF III 1, woschmidti Zone.

Fig. 23 - Icriodus hesperius Klapper & Murphy, 1975. DSTC 30050; lateral view of M element; sample RLF III 1, woschmidti Zone.

247Pl. 1C. Corradini, M.G. Corriga - Silurian and Lower Devonian conodonts from the Carnic Alps


and laterally compressed. The small basal cavity slightly rises on the inner side of the cusp and tapers as a groove under the processes.

S2 element hindeodelliform. The posterior process it long and slightly arched with discrete and alternate denticles. The anterior process is shorter and strongly bowed inward. The prominent cusp is inclined slightly posteriorly. The basal cavity is narrow and extends as a groove up to the posterior end.

Remarks - The most characteristic and easiest to recognize element of W. alternata n. sp. is the P2 element, for the obvious denticulation on the anterior process, where large and robust denticles alternate with small and thin ones (Pl. 2, figs. 2, 7-8).

The general morphology of elements of W. alternata n. sp. is similar to that of W. excavata, from which it differs only by the peculiar alternating denticulation. This supports the attribution of W. alternata n. sp. to this genus, even if according to the diagnosis of Wurmiella (Murphy et al., 2004, p. 8), representatives of the genus have “processes without strong size variation of adjacent denticles”.

S1 and S2 elements of Wurmiella alternata n. sp. differ from the equivalent elements of Ozarkodina eosteinhornensis because are thinner. Furthermore, the S1 element differs by the undulating lower margin of the posterior process and the S2 element by its less regular denticulation pattern. The S2 element is different from that of Zieglerodina because of the more pronounced angle within the processes and the less developed alternating denticulation.

In the Walliser collection from the Cellon section (Walliser, 1964), which C.C. had the possibility to study a few years ago during a visit in Göttingen, W. alternata n. sp. occurs in all samples from 32B to 34 (lower part of the eosteinhornensis s.l. Zone) and more rarely up to sample 46 (detortus Zone).

Stratigraphic distribution - Our material comes from the eosteinhornensis s.l. i.Z. and the lower part of the detortus Zone. The range of the species in the Cellon section is the same. The P1 element figured by Farrell (2004) is from the lower Pridoli, too, whereas all the other specimens reported in the synonymy list are from the upper Lochkovian (delta Zone). Therefore, the range of the species seems to cover most of the Pridoli and the Lochkovian, even if it is not documented up to now close to the S/D boundary and in the lower Lochkovian.

Studied material - 22 P1, 25 P2, 8 M, 6 S0, 9 S1 and 9 S2 elements from samples RLF 6B, 8, 8A, 9, 10, 12 and RLF III 3C-3B.

Wurmiella excavata (Branson & Mehl, 1933)(Pl. 2, figs. 9-25)

1995 Ozarkodina excavata excavata (Branson & Mehl) - SiMpSon & talent, p.147-153, Pl.8, figs. 16-25; Pl. 9, figs. 1-24 (cum syn).

2003 Ozarkodina excavata excavata (Branson & Mehl) - Corradini et al., Pl. 1 fig. 1.

2004 Wurmiella excavata (Branson & Mehl) - Murphy et al., figs. 2.29-2.36


Figs. 1-8 - Wurmiella alternata n. sp. 1 - holotype DSTC 30000/1; lateral view of P1 element; sample RLF 9, eosteinhornensis s.l. Zone; 2 - holotype DSTC 30000/2; lateral view of P2 element; sample RLF 9, eosteinhornensis s.l. Zone; 3 - holotype DSTC 30000/3; lateral view of M element; sample RLF 9, eosteinhornensis s.l. Zone; 4 - holotype DSTC 30000/4; lateral view of S0 element; sample RLF 9, eosteinhornensis s.l. Zone; 5 - holotype DSTC 30000/5; lateral view of S1 element; sample RLF 9, eosteinhornensis s.l. Zone; 6 - holotype DSTC 30000/6; lateral view of S2 element; sample RLF 9, eosteinhornensis s.l. Zone; 7 - paratype DSTC 30001; lateral view of a broken P2 element showing the characteristic denticulation pattern on the anterior

process; sample RLF 9, eosteinhornensis s.l. Zone; 8 - paratype DSTC 30002; lateral view of a broken P2 element showing the characteristic denticulation pattern on the anterior

process; sample RLF 9, eosteinhornensis s.l. Zone.

Figs. 9-25 - Wurmiella excavata (Branson & Mehl, 1933). 9 - DSTC 30011; lateral view of P1 element resembling W. tuma; sample RLF 9, eosteinhornensis s.l. Zone; 10 - DSTC 30012; lateral view of P1 element resembling W. tuma; sample RLF III 3B, detortus Zone; 11 - DSTC 30013; lateral view of P1 element; sample RLF 6B, eosteinhornensis s.l. Zone; 12 - DSTC 30014; lateral view of P1element; sample RLF 9, eosteinhornensis s.l. Zone; 13 - DSTC 30015; lateral view of P1 element; sample RLF 9, eosteinhornensis s.l. Zone; 14 - DSTC 30016; lateral view of P1 element; sample RLF III 4, detortus Zone; 15 - DSTC 30017; lateral view of P1 element; sample RLF 9, eosteinhornensis s.l. Zone; 16 - DSTC 30018; lateral view of P2 element; sample RLF 9, eosteinhornensis s.l. Zone; 17 - DSTC 30019; lateral view of P2 element; sample RLF 9, eosteinhornensis s.l. Zone; 18 - DSTC 30020; lateral view of M element; sample RLF 9, eosteinhornensis s.l. Zone; 19 - DSTC 30021; lateral view of M element; sample RLF 9, eosteinhornensis s.l. Zone; 20 - DSTC 30022; lateral view of S0 element; sample RLF 9, eosteinhornensis s.l. Zone, 21 - DSTC 30023; lateral view of S0 element; sample RLF III 4, detortus Zone; 22 - DSTC 30024; lateral view of S1 element; sample RLF III 4, detortus Zone; 23 - DSTC 30025; lateral view of S0 element; sample RLF 9, eosteinhornensis s.l. Zone; 24 - DSTC 30026; lateral view of S2 element; sample RLF 9, eosteinhornensis s.l. Zone; 25 - DSTC 30027; lateral view of S2 element; sample RLF III 4, detortus Zone.


2007 Ozarkodina excavata excavata (Branson & Mehl) - Suttner, p. 33-36, Pl. 1, fig. 3; Pl. 12, figs. 1-7; Pl. 13, figs. 3, 5, 8-9; Pl. 14, figs. 2-11; Pl. 16, figs. 1-7, 9; Pl. 17, figs. 1-3, 5.

2009 Wurmiella excavata (Branson & Mehl) - Corriga & Corradini, fig. 4C.

2009 Wurmiella excavata (Branson & Mehl) - Corradini et al., fig. 3e.

Remarks - Wurmiella excavata is by long the more abundant taxon in many Silurian collections. This elements occur also in the studied sections, where they are dominant in Silurian samples, but disappear close to the S/D boundary. However, there are several different morphologies of the P1 element, differing by the length of the element, its general shape (straight and slightly arched forms), presence of the cusp, size and numbers of denticles. In the studied sections, several samples from the eosteinhorensis s.l. and the lower part of the detortus zones yielded some P1 elements of W. excavata very long, slightly arched towards the extremities and bearing many

denticles (Pl. 2, figs. 9-10). These specimens reminds one of W. tuma; however, the latter species, which is the type species of Genus Wurmiella, has a higher short stratigraphic range limited to middle Lochkovian (Murphy et al., 2004).

Stratigraphic distribution - The species is documented from lower Silurian to Lower Devonian.

Studied material - 1103 P1, 262 P2, 179 M, 147 S0, 282 S1 and 421 S2 elements from samples RLF 1-12 and RLF III 5-2Y, 2A-1W, 1L.

Genus Zieglerodina Murphy, Valenzuela-Rios & Carls, 2004

Type species - Spathognathodus remscheidensis Ziegler, 1960


Fig. 1 - Oulodus siluricus (Branson & Mehl, 1933). DSTC 30051; lateral view of P1 element; sample RLF III 4, detortus Zone.

Fig. 2 - Oulodus elegans detortus (Walliser, 1964). DSTC 30052; lateral view of M element; sample RLF 11, detortus Zone.

Fig. 3 - Ozarkodina snajdri (Walliser, 1964). DSTC 30053; upper view of P1 element; sample RLF III 4, detortus Zone.

Fig. 4 - Ozarkodina sp. DSTC 30054; lower lateral (a) and lateral (b) views of P1 element; sample RLF III 2A, detortus Zone.

Figs. 5-6, 18 - Oulodus elegans elegans (Walliser, 1964). 5 - DSTC 30055; lateral view of S1 element; sample RLF III 2A, detortus Zone; 6 - DSTC 30056; lateral view of S2 element; sample RLF III 4, detortus Zone; 18 - DSTC 30068; oblique-lateral view of S0 element; sample RLF III 2, detortus Zone.

Figs. 7-8 - Ozarkodina eosteinhornensis s.l. (Walliser, 1964). 7 - DSTC 30057 upper view of P1 element; sample RLF III 2X, detortus Zone; 8 - DSTC 30058 lateral view of P1 element; sample RLF III 1B, woschmidti Zone.

Fig. 9 - Ozarkodina eosteinhornensis s.s. (Walliser, 1964). DSTC 30059 upper view of P1 element; sample RLF III 4, detortus Zone.

Figs. 10-13 - Zieglerodina remscheidensis (Ziegler, 1960). 10 - DSTC 30060 lateral view of P1 element; sample RLF III 1A, woschmidti Zone; 11 - DSTC 30061 lateral view of P1 element; sample RLF III 1A, woschmidti Zone; 12 - DSTC 30062 lateral view of P1 element; sample RLF III 1Z, woschmidti Zone; 13 - DSTC 30063; lateral view of P1 element; sample RLF III 1X, woschmidti Zone.

Figs. 14-16 - Ozarkodina planilingua Murphy & Valenzuela-Rios, 1999. 14 - DSTC 30064; upper (a) and lower lateral (b) views of P1 element; sample RLF III 1X, woschmidti Zone; 15 - DSTC 30065; upper view of P1 element; sample RLF III 1, woschmidti Zone; 16 - DSTC 30066; upper view of P1 element; sample RLF III 1A, woschmidti Zone.

Fig. 17 - Oulodus sp. DSTC 30067; lateral view of an anomalous S1 element bearing a branched anterior process; sample RLF III 1A, woschmidti Zone.

Fig. 19 - Zieglerodina zellmeri Carls et al., 2007. DSTC 30069; lateral view of P1 element; sample RLF 8, eosteinhornensis s.l. Zone.

Figs. 20-21 - Ozarkodina crispa (Walliser, 1964). 20 - DSTC 30071; upper view of P1 element; sample RLF 6, crispa Zone; 21 - DSTC 30070; lateral view of P2 element; sample RLF 6, crispa Zone.

Figs. 22-23 - Ozarkodina confluens (Branson & Mehl, 1933). 22 - DSTC 30072; lateral view of P2 element; sample RLF 8, eosteinhornensis s.l. Zone; 23 - DSTC 30073; lateral view of P1 element; sample RLF 8, eosteinhornensis s.l. Zone.

Upper scale bar valid for figures 1-16; lower scale bar for figures 17-23.


Remarks - Genus Zieglerodina was recently proposed by Murphy et al. (2004) to include the ozarkodinids of the “remscheidensis Group”. Taxa of the “eosteinhornensis Group” have a very similar morphology of all the apparatus elements, but the authors consider them belonging to a different genus (not yet established according to the IZNC rules) because of differences in the P1 element. The opportunity to establish two different genera very similar each other, or to place the two groups together in the same genus should be carefully evaluated and is not the topic of this paper.

Zieglerodina zellmeri Carls et al., 2007(Pl. 3 fig. 19)

2007 Zieglerodina zellmeri n. sp. CarlS et al., p. 162-163, fig. 6A-G, 6J-N, 8M-P (cum syn.).

Remarks - The specimens from the RLF section are very similar to the holotype. This is the first report of Z. zellmeri from the Carnic Alps.

Stratigraphic distribution - The taxon is known from the lower part of the Pridoli (Carls et al., 2007). The occurrence in the RLF section confirms the range.

Studied material - 2 P1 and 1 P2 elements from samples RLF 7A-8A.

CONCLUSIONS

The main results of the study of the Rifugio Lambertenghi Fontana and Rifugio Lambertenghi Fontana III can summarized as follows:- the conodont association allows the discrimination of

five late Silurian-lowermost Devonian conodont zones: snajdri, crispa, eosteinhornensis s.l., detortus and woschmidti;

- the Silurian/Devonian boundary can be placed in the upper part of the Rifugio Lambertenghi Fontana III, tentatively around sample RLF III 1L;

- the new species Wurmiella alternata n. sp. is described from the lower Pridoli strata;

- a P2 element tentatively attributed to Oz. crispa has been described;

- Belodella coarcata Barrick & Klapper, Dvorakia amsdeni Barrick & Klapper and Zieglerodina zellmeri Carls et al. have been reported for the first time in the Carnic Alps.

ACKNOWLEDGEMENTS

This paper is a contribution to a research project on the Silurian of the Carnic Alps arranged between several Italian universities (Cagliari, Modena and Reggio Emilia, Pescara) and institutions (Museo Friulano di Storia Naturale). Research includes geological mapping, palaeontology, stratigraphy and depositional history of Silurian rocks, with special regard to carbonate facies, in several sectors of the Carnic Alps. The final goal of the project is to provide a reconstruction of paleoenvironmental and paleogeographical evolution of the Carnic Basin during Silurian time.

This paper benefits from the opportunity that Prof. Otto Walliser (Göttingen) gave to C.C. to study his collection from the Cellon section. Luca Simonetto (Udine) and Monica Pondrelli (Pescara) are deeply acknowledged for help in the field work and discussions on the geology of the area. The authors thank Dick Aldridge (Leicester) for information on the apparatus of Oz. crispa and for discussion on the generic attribution of W. alternata n. sp. Elisa Zedda (Cagliari) helped with the conodont samples preparation, and Claudio Gentilini (Modena) and Gabriele Cruciani (Cagliari) took SEM microphotographs. “Immagini TerraItaly™ - © Blom Compagnia Generale Riprese aeree S.p.A. - Parma (www.terraitaly.it)” allowed the reproduction of the aerial view of the Passo Volaia area. The authors thank R. Mawson (Sydney) and J.E. Barrick (Texas Tech) for the detailed and useful comments which made stronger this manuscript; the latter is acknowledged also and for correcting the English language.

This research was supported by grants “ex-60%” University of Cagliari (resp. C. Corradini).

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Manuscript received 22 April 2010Revised manuscript accepted 18 November 2010


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