Bollettino della Società Paleontologica Italiana, 44 (3), 2005, 255-262. Modena, 30 novembre 2005255

New evidences of Silurian Phyllocarid from SW

Maurizio GNOLI & Paolo SERVENTI

M. Gnoli, Dipartimento del Museo di Paleobiologia e dell’Orto Botanico, Università di Modena e Reggio Emilia, Via Università 4, I- 41100 Modena, ; [email protected] P. Serventi, Dipartimento del Museo di Paleobiologia e dell’Orto Botanico, Università di Modena e Reggio Emilia, Via Università 4, I- 41100 Modena, Italy; [email protected]

KEY-WORDS - Crustacea, , Silurian, Abdominal somites, Telson, Mandibles, SW Sardinia, Italy.

ABSTRACT - Phyllocarid remains consisting of abdominal somites, caudal parts and secondarily phosphatized mandibles, from Silurian of SW Sardinia are described and illustrated. Some material described and left in open nomenclature by Gnoli & Serpagli (1984) is also reconsidered under Warneticaris cenomanensis (Tromelin, 1874). Other taxa like Ceratiocaris (Bohemicaris) bohemica (Barrande, 1872), C.? (B.) sp. ind. cf. bohemica Barrande, 1872, C. (C.?) cf. cornwallisensis damesi Chlupáè, 1963, and Warneticaris sp. ind. cf. W. cenomanensis (Tromelin, 1874) are also documented.

RIASSUNTO - [Nuovi resti di fillocaridi (Crustacea, Artropoda) nel Siluriano della Sardegna sudoccidentale] - Dopo la prima descrizione e illustrazione di resti di fillocaridi provenienti dalla Sardegna sudoccidentale al limite Siluriano/Devoniano, avvenuta nella prima metà degli anni ottanta, ne viene presentata una ulteriore. Tutti gli esemplari esaminati provengono dalla Formazione di Fluminimaggiore e mostrano un eccellente stato di conservazione in quanto si presentano in tre dimensioni. Sulla base dei dati sedimentologici è possibile dedurre un ambiente deposizionale di mare poco profondo, normalmente ossigenato e sottoposto a moto ondoso nelle sue parti più elevate mentre era anossico nelle zone più profonde. Dallo studio dei nuovi campioni, costituiti da segmenti addominali, parti caudali ed altre mandibole fosfatizzate, vengono documentati i seguenti taxa, Ceratiocaris (Bohemicaris) bohemica (Barrande, 1872), C.? (B.) sp. ind. cf. bohemica Barrande, 1872, C. (C.?) cf. cornwallisensis damesi Chlupáè, 1963, e Warneticaris sp. ind. cf. W. cenomanensis (Tromelin, 1874). A questi si aggiunge il materiale già descritto e lasciato in nomenclatura aperta da Gnoli & Serpagli (1984), qui considerato appartenere a Warneticaris cenomanensis (Tromelin, 1874).

INTRODUCTION Updated information on the lithology, palaeontology and environment of the Fluminimaggiore and Mason Porcus During the past three decades paleontological Formations in the locality Perd’e Fogu near investigations and accurate sampling of Silurian Fluminimaggiore and Argiola can be found in Serpagli sections, carried out by a team of the Dipartimento del (1998), Ferretti et al. (1998a, b), and Corradini et al. Museo di Paleobiologia e dell’Orto Botanico (Università (1998a, b). di Modena e Reggio Emilia), have supplied a rich The Sardinian localities where phyllocarid remains collection of fossils including phyllocarid remains. Some were found are summarised in Fig. 1. The Tab. 1 shows of these specimens were illustrated twenty years ago the phyllocarid remains recovered in Silurian sections by Gnoli & Serpagli (1984). However, the most or displaced blocks, with the age (biozones) and the important discovery on this topic is due to Hamman et lithology related to the reported samples. al. (1990) who demonstrated that the “phyllocarids” of the so called «phyllocarid beds of Taricco (1922)» actually belong to «an unusual trilobite-like » SOME REMARKS ON PHYLLOCARID named Tariccoia arrusensis, later regarded as a true PALEOECOLOGY AND BIOSTRATIGRAPHY trilobite of the Nectaspida Order (Hamman & Leone, 1997). The lithology of displaced blocks bearing phyllocarid The new phyllocarid remains, all collected from the remains, deduced from investigations on sedimentary Fluminimaggiore Formation, consist of three structures and associated fauna (Ferretti, 1989) fragmentary specimens with abdominal segments indicates a shallow sea shelf normally oxygenated in (preserved in three dimensions), a dozen caudal parts its upper parts and anoxic towards the bottom (Gnoli and several fragments and/or whole specimens of et al., 1980). secondarily phosphatized mandibles that commonly This shelf, reworked by wave motion, developed in occur in the acid-resistant residues of conodont a shallow basin, stirred by currents in its upper part samples. (Fluminimaggiore and Mason Porcus Formations (Gnoli Information on Lithostratigraphic units of SW et al., 1990)), where, during Pøídolí-early Devonian Sardinian Silurian-early Devonian rocks, including the time, pelagic-type sediments were formed (Gnoli, 1985). phyllocarids-bearing beds, and biostratigraphy of the Apparently, Silurian phyllocarids do not characterize key-section «Mason Porcus» can be found in Gnoli et a specific environment, being present either in the more al. (1988, 1990) and in Ferretti & Serpagli (1996). shallow marine facies (poorly washed biomicrite) or in

ISSN 0375-7633

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added to the good preservation of the majority of the fossils would suggest short and slight transport on a typically muddy bottom. The paleoecological analysis of the associated fauna does not help much in clarifing the paleoenvironmental setting because it is mainly represented by orthoconic nautiloids occurring only in some horizons of scattered sequences (i.e. «Argiola» ARG-BK 15). Phyllocarid life habits have been described in details (e.g. Chlupáè, 1994; Vannier et al., 1997) taking into account their adaptation to dysaerobic bottom conditions. The use of phyllocarids as stratigraphic tools is due to Chlupáè (1994) who carried out a revision and a general synthesis on the biostratigraphy of Bohemian phyllocarid. The age of phyllocarid remains in SW Fig. 1 - Location of the Sardinian fossiliferous localities in which Sardinia, has been mainly deduced by means of the phyllocarid remains have been collected. associated conodonts (Tab. 1) found in the acid- resistant residues of the blocks and/or sequence samples by several authors (Serpagli, 1971; Serpagli & the relatively deeper ones. Telson parts - sometimes Mastandrea, 1980; Olivieri & Serpagli, 1990; Olivieri with parallel orientation probably stirred up by current et al., 1981; Mastandrea, 1985; Gnoli et al., 1988; - are the most common phyllocarid fragments. On the Ferretti et al., 1998; Corradini et al., 1998; Corradini & contrary, abdominal somites are rare with only three Serpagli, 1998, 1999; Serpagli & Corradini, 1999). Also specimens recovered so far. This environmental setting other index fossils, like graptolites, have been sometime

Tab. 1 - Distribution of taxa in the samples bearing phyllocarid remains: age (biozones) and lithology. Abbreviations: BK = displaced block; ARG = «Argiola» section, MP = «Mason Porcus» (House of pigs) section, SF = Fluminimaggiore path section, GALE = «Galemmu», PF = «Perd’e Fogu» (Fire Stone). Conodont biozonation according to Corradini & Serpagli (1998-99). * After Jaeger (pers. comm., letter of July 20th, 1987).

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used. The Sardinian conodont biozones are those can be seen in Fig. 2g, there are 9 longitudinal ridges defined by Corradini & Serpagli, (1998, 1999). that run along its whole length: one on the dorsal side, two orders of dorso-lateral, and two dorso-ventral between which there are slightly concave depressed SYSTEMATIC DESCRIPTIONS areas. Between the dorso-lateral ridges, several sub- elliptic alveoli are present for bristle insertion. The alveoli All the material studied is housed in Paleontological diameters are about 0.8 and 0.7 mm, the distance Collection of the Dipartimento del Museo di between them is quite regular and they are placed about Paleobiologia e dell’Orto Botanico under the Cat. nos. 2.2 mm apart. In the studied material the bristles are IPUM 19801, 19836, 24236-24246. never preserved. The furca rami are also polygonal- rounded in cross-section, depressed and bearing 10 Order PHYLLOCARIDA Packard, 1879 longitudinal ridges in their proximal part, whereas Suborder CERATIOCARINA Clarke, 1900 distally the ridges become rounded so they probably Family CERATIOCARIDIDAE Salter, 1860 terminate with a fairly sub-elliptic or lens-shaped cross- Ceratiocaris Mc Coy, 1849 section. Another specimen (IPUM 24242) from the same displaced block (ARG-BK 15) bears three strongly Type-species - Ceratiocaris solenoides Mc Coy, damaged fragments of caudal parts: two of telson and 1849; Miller, 1889 by subsequent designation. a ramus of furca not preserved in anatomical position. These caudal parts are 59, 27 and 9 mm long Subgenus Ceratiocaris (Bohemicaris) Chlupáè, 1994 respectively and show the same features belonging to the same species as above. A further caudal fragment, Type-species - Ceratiocaris bohemica Barrande, 38 mm long in the counterpart, showing the same 1872, by original designation, Chlupáè, 1994, p. 14. morphology as above reported, is that from level 2b of the Mason Porcus section (IPUM 24244). Ceratiocaris (Bohemicaris) bohemica (Barrande, 1872) Remarks - The ornamentation of the fifth abdominal (Figs. 2a-i) somite previously described and, in particular, the presence of the very small depressions (Fig. 2b’) could 1984 Ceratiocaris cf. bohemica Barrande, 1872 - GNOLI & represent slits of probable sensory terminations below SERPAGLI, p. 258, figs. 1, 15. the exoskeleton for possibly sensing environmental 1994 Ceratiocaris (Bohemicaris) bohemica CHLUPÁÈ, pp. 5, variations (physical and/or biological). Their actual 14; Pl. 1, figs. 1-6. function remains unknown. These morphological Ceratiocaris (Bohemicaris) bohemica è 1994 Chlupá - peculiarities were never previously reported with the RACHEBOEUF, pp. 289-291, text-figs. 3B, 5. exception of Vannier et al. (1997), who figured Material - Two specimens with fifth, sixth and something similar feature (Vannier et al., 1997, fig. 9B) seventh abdominal somites with poorly preserved from the right pleural fold of the Devonian caudal part (IPUM 24236 and unfigured 24246) plus archaeostracan phyllocarid Rhinocaris columbina various fragments of telsonal part with furcal rami Clarke in Hall & Clarke 1888. (IPUM 24242, 24243, and unfigured 24244).

Description - All the abdominal somites preserved Ceratiocaris? (Bohemicaris) sp. ind. cf. bohemica were compacted; furthermore the fifth one preserves (Barrande, 1872) only its terminal part, but unlike the sixth and seventh (Figs. 3a-b) ones that are apparently smooth, it bears an ornamentation consisting of longitudinal ribs that run Material - Sixth, seventh abdominal segment roughly parallel to the axis of the segment and are distally exoskeletal parts and telson head (IPUM 24241). anatomised (see Barrande, 1872, pl. 19, fig. 2 and Abdominal somites are shifted over each other rather present paper, Fig. 2a). In a small area of this than squeezed and probably not anatomically jointed to ornamentation it is possible to distinguish very thin, a telson head for a total length of 53 mm in a little small (0.27 to 0.12 mm in length) very characteristic, displaced block (probably coming from level 5 of the slit-like or long comma-like depressions (Fig. 2b’) Mason Porcus section). slightly oblique to the ribs. Their length varies from corresponding to about 1/3 to 1/2 of the distance Description - The specimen IPUM 24241 shows between ribs, that is 0.3 mm. The probable function of the sixth and seventh abdominal somites displaced from these depressions is discussed in the following remarks. the anatomical position probably due to compaction of The abdominal somites are 15, 26 and 34 mm long the muddy sediment. However, these preserve a peculiar respectively. Caudal parts are very fragmented. ornamentation consisting of sub-parallel ribs oblique One specimen (IPUM 24243) consists of a fragment to the axis of the somites (about 45 degrees). This can of telson and two fragments of the furcal rami arranged be identified as the proximal part of the last abdominal sub-parallel to each other in the sediment. The telson somite where the ribs form a concentric botroidal shows a sub-polygonal cross section in its middle part pattern of ornamentation as shown in Fig. 3b. The where it corresponds to 5.5 mm in lateral width; as telson head, which is the largest one among all

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specimens so far found in Sardinia (12.5 mm in width), Remarks - This poorly preserved material does not bears as ornamentation fine oblique ridges disappearing allow more detailed taxonomic studies. This sample posteriorly. represents the third abdominal segment exoskeletal part ever recovered from Sardinia.

Fig. 2 - Ceratiocaris (Bohemicaris) bohemica (Barrande, 1872). a) Upper view of the whole specimen (No. 24236). Scale bar = 20 mm; b) fifth segment showing sub-parallel wrinkled pattern of ornamentation of the same specimen. Scale bar = 10 mm; b’) particular enlarged to show the very small slit-like structures between the ribs forming ornamentation of the same specimen. Scale bar = 5 mm (see text for interpretation); c) upper view of the sixth abdominal somite of the same specimen. Scale bar = 5 mm; d) upper view of the seventh abdominal somite of the same specimen. Scale bar = 20 mm; e) poorly preserved caudal part of the same specimen. Scale bar = 20 mm; f) upper view a couple of telsons (T) and a furcal ramous (Fr) of No. 24242 specimen. Scale bar = 10 mm; g, h) telson and furcal rami of another specimen (No. 24243) showing their polygonal cross-sections (pentagonal the telson, more complex and rounded the (h) furcal rami). Scale bar = 15 mm; i) the same specimen in perspective view (note the alveoli for bristle insertion). Scale bar = 5 mm; Note: the left furcal ramus cross-section of Fig. 3h is figured reflecting the right one horizontally because specimen No. 24243 is not so well preserved.

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Remarks - Since the surface of the lower part of the telson, just after the telson head between the two ventro-lateral ridges, is moderately concave, (Fig. 4d), we prefer to leave this form in open nomenclature. This species is reported here for the first time from Sardinia.

Genus Warneticaris Racheboeuf, 1994

Type species - Ceratiocaris cenomanense Tromelin, 1874 by subsequent designation, Racheboeuf, 1994.

Warneticaris cenomanensis (Tromelin, 1874) (Figs. 5a-c)

1874 Ceratiocaris cenomanense TROMELIN in Gullier & Tromelin, p. 590. 1876 Ceratiocaris cenomanensis Tromelin - TROMELIN & LEBESCONTE, p. 651. 1886 Ceratiocaris cenomanensis Tromelin - GUILLIER, p. 54. 1935 Ceratiocaris cenomanense Tromelin - PÉNEAU, p. 551. Fig. 3 - Ceratiocaris? (Bohemicaris) sp. ind. cf. bohemica 1984 Ceratiocaris sp., GNOLI & SERPAGLI, p. 260, figs. 2a-d. (Barrande, 1872) (No. 24241). 1994 Warneticaris cenomanensis (Tromelin) - RACHEBOEUF, pp. a) Lateral view of the whole specimen, scale bar = 10 mm; 287-289; Pl. III, figs. 1-11; Pl. IV, figs. 1-2; text-figs. 3D, b) close-up of the same specimen to show ornamentation of the 4. seventh somite, scale bar = 5 mm. Material - Left side of the last (seventh) abdominal somite and proximal part of telson (IPUM 19836) for a total length of 31 mm (already published by Gnoli & Serpagli (1984) and left in open nomenclature as Subgenus Ceratiocaris (Ceriatocaris) McCoy, 1849 Ceratiocaris sp.).

Type-species - Ceriatocaris solenoides McCoy, 1849.

Ceratiocaris (Ceriatocaris?) cf. cornwallisensis damesi Chlupáè, 1963 (Figs. 4a-d)

1886 Ceratiocaris damesi NOVÁK, p. 676 (nomen nudum). 1963 Ceratiocaris cornwallisensis damesi CHLUPÁè, pp. 104- 108; Pl. 12, figs. 9-10; Pl. 14, figs. 3-5; Pl. 15, figs. 1-4; text-figs. 3-5.

Material - Telson (IPUM 24237) with 45 mm long broken tip (reaching 53 mm in the counterpart) from level 5 of the «Mason Porcus» section.

Description - The well preserved telson (Figs. 4a- d) shows two rows of alveoli for the insertion of bristles in the dorso-lateral ridge. Eleven symmetrical alveoli are preserved on both sides, showing an elliptical shape; they are regularly spaced 2.33 mm apart (Fig. 4c), the axes of which are 0.66 mm and 0.4 mm. In cross- section, towards the lower part after the ridges bearing alveoli there are two concave areas, followed by two ventro-lateral ridges ending with a ventral platform. The latter protects ventrally the articulation of the furca (Fig. 4b). The telson head is hemispherical in shape and bears Fig. 4 - Ceratiocaris (Ceratiocaris?) cf. cornwallisensis damesi an ornamentation consisting of fine radiating lirae. In Chlupaè, 1963 (No. 24237). its central part the cross-section is sub-pentagonal in a) Dorsal view of the telson; outline and from each corner originates five longitudinal b) lateral view of the telson showing the ventral recumbent rounded ridges, which reduce to four towards its apical protection to the articulation for the furcal rami movement; part (as reported by Chlupáè, 1963, p. 106, text-fig. 4; c) close-up of dorso-lateral view for bristle insertion; and Rolfe, 1963, p. 487, text-fig. 1; see also Fig. 4d in d) schematic proximal, distal, and terminal telson cross-sections. this paper). All scale bars = 10 mm.

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of this section had already been described by Gnoli et al. (1988). According to P. Racheboeuf (letter of February 25th, 2004), the specimen described by Gnoli & Serpagli (1984), «… could probably belong to a new genus because of the shape of the telson, with a sub half- rounded head in cross-section, becoming triangular posteriorly, and also because the morphology of the furca do not fit in with Ceratiocaris». Chlupáè (1985, personal comm.) suggested that the Sardinia Ceratiocaris sp. could be close to grata and perhaps classified as C. cf. grata. In addition, Racheboeuf (1994, p. 287) assigned the Bohemian Ceratiocaris grata Chlupáè, 1984, to his new genus Warneticaris suggesting that grata is the most closely allied to cenomanensis. On the basis of the aforementioned remarks and after careful restudy of the 1984 specimen (previously left in open nomenclature), we prefer to assign this form to Warneticaris cenomanensis (Tromelin, 1874).

Warneticaris sp. ind. cf. cenomanensis (Tromelin, 1874) (Figs. 6a-e)

Material - A triangular telson and furca, 73 mm long in cross-section (IPUM 24238), from level 5 of the Mason Porcus section. Fig. 5 - Warneticaris cenomanensis (Tromelin, 1874) (No. 19836). a) Dorsal view of the whole specimen. Scale bar = 10 mm; b) enlargement of the last pleonite showing ornamentation by triangular scales and the telson head of the same specimen in dorso-lateral view with ornamentation represented by oblique fine V-shaped short striae. Scale bar = 5 mm; c) left lateral view of the telson of the same specimen showing oblique lateral ridge and the left row of alveoli for bristle insertion. Scale bar = 7.5 mm.

Description - The last abdominal segment bears a characteristic ornamentation mainly consisting of triangular, apparently imbricate scales (see comparable features in Vannier et al., 1997, pp. 100-101, fig. 10) like for the Palaeozoic archaeostracan phyllocarids. The telson is triangular in cross-section and bears bilaterally rows of sub-elliptic alveoli, just above the dorso-lateral oblique ridges (about 0.2 mm wide, 0.6 mm long, and distant 2.2 mm from each other) for bristles insertion. Its ventral part shows longitudinal furrows, proximally semicircular to rounded-triangular distally. The telson head is sculptured by sub-triangular pattern of oblique short lines. Posteriorly to its head, which is semi- Fig. 6 - Warneticaris sp. ind. cf. cenomanensis (Tromelin, 1874) circular in cross-section, the telson bears ventro-lateral (No. 24238). apertures for the insertion and articulation of furcal Figs. a-c, scale bar = 15 mm. rami which are flattened, shorter than the telson and a) Dorsal view of the telson; lanceolate in shape. Unfortunately, only the left furcal a’) schematic middle telson sub-triangular cross sections; ramus is preserved in the specimen studied here. b) the same telson in lateral view; c) the same in ventral view; d) furcal rami of the same telson in upper view. Scale bar = 25 Remarks - As for the abdominal segments (see mm; introductory part) - these exoskeletal parts are rather e) close up of the left ventral ridge counterpart showing the row rare, since only three have been so far recovered from of very little alveoli close to each other for fine bristle insertion. the «Mason Porcus» section. The lithology and fauna Scale bar = 25 mm.

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Description - The 62 mm long telson (with Corradini C., Ferretti. A. & Serpagli E. (1998b). Wenlock and incomplete tip), reaching 73 mm in the counterpart and Pøídolí conodonts from Argiola, East of . In 13 mm in width, shows the typical features of W. Serpagli E. (ed.), Sardinia Guide-book, ECOS VII. Giornale di Geologia, 60, Special Issue: 194-198, Bologna. cenomanensis. However, in lateral view the telson is Corradini C., Ferretti. A., Serpagli E. & Barca S. (1998). The not straight, but gently curved upwards distally (Fig. Ludlow-Pøídolí Section “Genna Ciuerciu” west of . In 6b). Size and ornament are also completely different in Serpagli E. (ed.), Sardinia Guide-book, ECOS VII. Giornale the two forms. di Geologia, 60, Special Issue: 112-118. The dorso-lateral ridges are not clearly preserved Ferretti A. (1989). Microbiofacies and constituent analysis of as well as the ventral platform recumbent posteriorly Upper Silurian-Lowermost Devonian limestones from Southwestern Sardinia. Bollettino della Società Paleontologica to protect the furcal rami articulation. The alveoli for Italiana, 28 (1): 87-100. bristle insertion are clearly visible only in the Ferretti A. & Serpagli E. (1996). Geological outline, community counterpart of one of the two ventral ridges that run sequence and paleoecology of the Silurian of Sardinia. Rivista symmetrically along the whole ventral part of the telson Italiana di Paleontologia Stratigrafia, 102 (3): 353-362. The alveoli are very small (about 0.15 mm of diameter), Ferretti A., Corradini C. & Serpagli E. (1998a). The Silurian and close to each other and circular in shape (Fig. 6e). Devonian sequence in SW Sardinia. In E. Serpagli (ed.), Sardinia Guide-book, ECOS VII. Giornale di Geologia, 60, Special Issue: 57-61. Remarks - The large size of the Sardinian telson Ferretti A., Corradini C. & Serpagli E. (1998b). Wenlock-Ludlow implies that it probably belonged to either an adult or a conodonts from Perd’e Fogu (Fluminimaggiore). In Serpagli gerontic specimen. E.(ed.), Sardinia Guide-book, ECOS VII. Giornale di This form is compared in its general shape to W. Geologia, 60, Special Issue: 156-167. cenomanensis, but lateral and ventral ridges are sharp Gnoli M. (1985). Paleontological content, constituent analysis and not rounded as it appears in the reconstruction of and microbiofacies of Early Devonian pelagic limestone from Fluminimaggiore area (SW Sardinia). Bollettino della Società Racheboeuf (1994, fig. 4B). Furthermore, the Paleontologica Italiana, 23 (2) [1984]: 221-238. incomplete preservation of the material studied also lead Gnoli M. & Serpagli E (1984). Evidence of phyllocarid remains us to leave this form in open nomenclature. from Silurian-Devonian boundary beds in southwestern Sardinia. Neues Jahrbuch für Geologie und Paläontologie Monatshefte, 1984, H. 5: 257-268. ACKNOWLEDGEMENTS Gnoli M., Køíž J., Leone F., Olivieri R., Serpagli E & Štorch P. (1990). Lithostratigraphic units and biostratigraphy of the Thanks are due to the late Dr. Ivo Chlupáè (Charles Silurian and early Devonian of Southwest Sardinia. Bollettino University, Prague, Czech Republic), for useful discussion and della Società Paleontologica Italiana, 29 (1): 11-23. suggestions on the first proofs of the paper. This work benefits Gnoli M., Leone F., Olivieri R. & Serpagli E. (1988). The Mason also by from the expertise of Prof. Patrick R. Racheboeuf Porcus Section as reference section for Uppermost Silurian- (Université de la Bretagne occidentale, Brest, France) and his Lowermost Devonian in SW Sardinia. Bollettino della Società profitable experience on the topic. Many thanks to Prof. E. Paleontologica Italiana, 27 (3): 323-334. Serpagli and Prof. C. Corradini for their help on updated conodont Gnoli M., Mastandrea A. & Serpagli E. (1982). Osservazioni biostratigraphy. We thank also Prof. J. 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