Conodonts across the Permian-Triassic boundary in ...

Cour. Forsch.-Inst. Scnckcnberg I 245 I 281-313 I

7 Figs, 4 Pls

I FrankfUJ1 a. M., 30. 12.2003

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Conodonts across the Permian-Triassic boundary in the Southern Alps With 7 figs, 4 pls Maria Cristina PFRRI & Enzo FARABEGOLI

Abstract The Tesero and Hulla sections (Dolomites, Italy) currently considered 01' pivotal importance l'or thc l'ermian-Triassic (P-T) boundary in the western Tethys were characterised hy a medium to high rate of shallow-marine sedimentation (5-]() cm k.y.-'). The thin, uppermost carbonate facies ofthe Permian Bellerophon Fmn (here named the "Bulla Member") is bounded regionally by unconformable surfaces. The upper unconforrnity coincides with the base of the Werfen Fmn historically identificd with the P-T boundary. In the Bulla scction, it slightIy antedates (by 1.3 m) the P-T boundary-defined hy conodonts, specifically the firs! appearance of Hìndeodus parvus. The Bulla Mbr yielded Hì. typicalis and Hi. praeparvus, extending their ranges above the P-T boundary into the Wcrfcn Fmn The conodont associations l'rom the lower part ofthe Werfen Fmn consist mainly ofhindcodids and isarciccllids showing graduai morphological change up-scction. The thickness and swcll1l1g ofthe basai cavity anù of th.e attachment area of the denticlcs-giving the conodont a swollen appearance-has been considercd laxonomically significant for ùefining rorms to be grouped in Isareìee/la. Four ncw specics are describcd: Ifindeodus pìsai. Isareicella lobala. Is. m(lala and Is. peculiaris. Seven conodont biozoncs have been discriminated, three are defined for the first time: Lower and Upper praeparvlIs. parvlIs. loba!a. slaeseheì, ìsareica and aeqllabì/is zones. A possible lincagc between the genera Hindeodus and [mreicclla is suggested. JJi. praeparvus has been considered the anccstor of Hi. parvus, the last represcntativc offlindcodus in the Southern Alps. Ili. praeparvIIs is also ancestral to Isarcicella prìsea tÌ'om which the subsequent Isarcìcefla lineage evolved, namely Is. prìsca to Is. turgida, Is. lobata, lI'. s!aeschei and Is. isarciea. The carbonate-terrigenous deposits around the P-T boundary oceur in thin (dm-m thick) depositional cycles, recording superimposed high frequency, fourth- (l 00 k.y. period) and fifth- (\ 0-25 k.y.) order cycles driven by short-terrn sea-Ievel fluctuations. The main mass-extinction event occurred dunng the rapid sea-Ievel fall followed by sea-Ievel rise at the contact of the Belferophon and Werfen Fmns. The lowstand exhumed the top of the Bellerophon Fmn shallow-watcr carbonates resulting in moderate weathering and erosion ofbcdrock. Many remanié Perrnian fossils occur in the basai Werfen Fmn transgrcssive trae!. The high conodont diversity in the lower Tesero \llbr accords with rapid adaptative radiation following c1imatic change. On the basis ofour resu\ts, we propose thallhe Bulla section---(;haracterised by relatively abundant conodonts prccisely located in readily discriminahle high- depositional cycles-is the mosl rcliahle parastratotype scction for the P-T boundary in the western Palaeotethys.

K e y w o r d s: conodonts, Permian-Triassic boundary, Southern Alps, Italy.

Introduction Since the nineteenth century, the Perrnian-Triassic boundary (P- T boundary) in the Southem Alps (Italy, Austria) has been equated with the lithostratigraphic boundary between the Bellerophol1 Fmn (below) and Werfen Fmn (above) (RICHTHOFEN 1860, LEPSIUS 1878, MOJSISOVICS 1879, MERL;\ 1930, LEOI\\RI)I I935, PIA) 937, BOSELLINI 1964, ASSERFTO et al. 1973), two units cropping out extensively (fig. l) over an area of about 40,000 sq. km. VENZO

(1957) and subsequently PASINI (1985) found that the oldest layers ofthe Werfen Fmn produced foraminifers, fusulinids and calcareous algae ofPerrnian aspect. Attribution ofthe lowermost Werfen Fmn to the Pcrrnian, supported by additional palaeontologic data (NERI & P\SI'i1 1985, BROGLIO LORIGA et al. 1986, POSENATO 1988), became genera\1y accepted during the last decade when more than 20 detailed contributions to litho- and hiostratigraphy, sedimentology and depositional architecturc around the P T boundary have been proposed for correlation between the Southem

Authors' addresses: Dipartimento di Scienze della Terra e Geologico-Ambientali, University of Bologna, Italy. Fax: 0039 051 2094522. >perri@;geomi.n.unibo.itfà[email protected]
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Hindeodus typicalis (SWEET) - KO/L'R: 65, pl. l, figs 1,3,4. Hindeodlls tvpicalis (S\\FFT) - YI'\ ci al.: pl. 2. 8. figs 5, 13. Hindeodus typicalis (SWEEr) - OkCII\RD & KRYSTYN: 357, pl. 6, figs 18-19,25-26.

Description: The Pa element is characterised by a low cusp and denticles ofthe bIade decreasing slight1y in height towards the postcrior end. Denticles present are free only at their apices. The pit is located in the first third of the lachrymiform narro w basaI cavity. R e m a r k s: In the studied material, Hindeodlls typicalis is rare even though present from the upperrnost levels of the Bellerophon Frnn up to the lower part of the Werfen Fmn--the Tesero and Mazzin Mbrs. Forrns c10ser to the holotype have been found aeross thc lithostratigraphic boundary ofthe two tòrmations. Occurrence - Uppermost levels of the Bellerophon Fmn Col di Rioda section, sample CR3; Casera Federata section, sample CFI5. Werfen Fmn, Tesero Mbr. Bulla section, sample BUIO; Strigno section, sarnple STIB. Mazzin ~br. Casera Federata section, sample CFI6; Tesero section, sample TS 19. R a n g e: Lower praeparvlIs-parvlIs zones: uppermost Permian-Lower Triassic, lower Scythian.

Genus Isarcicella KOZUR 1975 Type species: Spathognathodus isarcicus HUCKRIEDE 1958 Revised diagnosis: Multielernent apparatus with scaphate element in Pa position characterized by swelling/ thickening of the basai cavity bordered by flange-like brims. Nodes or denticles may or may not be present on one or both sides ofthe cup. Remarks: According to PERRI'S opinion the genus lsarcicella defined by KOZUR (1975) for Pa clernents showing a very wide and inftated cup bearing lateral nodes or denticles has to be extended also to elements with weakly to highly asymmetrical and swollen cup but without lateral nodes. Forms occurring stratigraphically lower displaying weak asymmetry and swelling of the basaI cavity and without lateral nodes have been included. The species changxingensis, peculiaris. prisca and tllrgida will, accordingly, be assigned to Isarcicella. Species such as /ohata and inflata showing an asymmetrical. swollen and thickened cup and appearing very c10se to 1.1'. staeschei and Is. isarcica, but without lateral nodes or denticles, are here placed in lsarcicella. Taxonomically signifìcant characters offònns referred to are: 1) asymmetrical weakly to highly inflated cup bordered by flange-like brirns; 2) pit tending to be centraI; 3) cusp wide, higher than the other dentici es - the latter tend to become rounded in section and discrete

Cour. Forsch.-Inst. Senckenberg, 245, 2003 in species stratigraphically higher; 4) posterior end mainly abrupt but sometimes denticulate. l~arcicella should have a multielement apparatus cIose to that of Hindeodus even though different. In samples where many Pa elements of Isarcicella are present there are few ramiforms which could be referred to the Isarcicella apparatus. Unfortunately these are broken and numerically much fewer compared with Pa elements so it was impossible to be sure ofthe constitution ofthe apparatus.

Range: Upperpraeparvus Zone: uppermost Permian.

Isarcicella inflata n. sp. (pl. 4, figs 10-11, 15-19) 1981 1991 1991

Range: Upper praeparvus-isarcica zones: uppermost Permian-Lower Triassic, lower Scythian.

Isarcicella changxingensis (WANG 1995) (pl. I, figs 17-19) 1995 1995 1999

Hindeodus changxingensis WANG: 149, pl. 2, figs 14-18 Hindeodusjulfensis (SWEET) - WANG: pl. 23 fig. 1 Hindeodus changxingensis WANG - NICORA & PERRI: pl. 3, fig. 4.

Description: The Paelementis characterised for having part ofthe biade straight, adenticuiate, smooth. Remarks: In the hoIotype described by WANG (1995: pl. 2, figs 16-18) only two denticIes are present posterior to the high and wide cusp in front ofthe smooth biade. WANG figured (1995: pl. 3, fig. 1) another specimen assigned to Hindeodus julfensis. According to PERRI that form is closer to the holotype of changxingensis - from which is differentiated solely by having several denticIes behind the cusp - rather than to Hindeodus julfensis. This last species is characterised by a peculiar "hump" lacking in WANG'S specimen; it therefore could be assigned to Is. changxingensis. In the Alps, NICORA & PERRI (1999: pl. 3, fig. 4) found a specimen at 1.30 m from the base ofthe Werfen Fmn in the Tesero section; it was referred to Hi. changxingensis. Behind the unfortunateIy broken cusp it dispIays five narrow denticIes followed by portio n of an adenticulate, smooth biade. The posterior third ofthe unit shows three little denticIes decreasing in height. The smooth part of the biade is shorter than in the hoIotype of the species - indicated by numerous free denticIes behind the cusp. The specimen found in the Alps has the same peculiarity - visible in WANG'S previously cited specimen (pl. 3, fig. l) - showing 3-4 denticI es folIowed by a piece of non-denticulate bIade. AlI the forms, either from China or Tta\y, have an asymmetrical very wide and inflated cupo In this paper, PERRI considers this feature as a taxonomic character for distinguishing Hindeodus from Isarcicella; representatives of the species changxingensis should be compared with primitive forms showing swelling and thickening of the basaI cavity and which have been included herein in Isarcicella. Occurrence: Werfen Fmn, Tesero Mbr. Tesero section, sample TES71.

Hindeodus parvus (KOZUR & PJATAKOVA) - MATSUDA: 91, pl. 5, fig. I. Isarcicella isarcica morphotype l (HUCKRIEDE) - PERRI: 42, pl. 4, fig. IO, pl. 5, fig. 5. Isarcicella isarcica morphotype 2 (HUCKRIEDE) - PERRI: 42, pl. 5, fig. 4.

Derivatio nominis: Pa element characterised by an enormously swollen and lobed cupo HoIotype: ICI465-8923, figured in pl. 4, figs 15-17 and in PERRI (1991) in pl. 4, figs IO a-b. Locus typicus: Bulla section about 0.5 km along the road NW ofBulla village, Province ofBolzano, Western Dolomites. Stratum typicum: Level ofsample BU27 ofthe Bulla section; Mazzin Mbr 45 m from the base of the Werfen Fmn Repository: Museum G. Capellini, Dipartimento di Scienze della Terra e Geologico-Ambientali, University ofBologna. Material: 12 specimens. Diagnosis: The Pa element is characterised by a very wide, asymmetrical, lobed, swollen and thickened cup lacking Iaterai nodes or denticIes. BIade composed of 6-8 denticIes. Cusp high. Description: The cup is extremely expanded and can be lobed on both sides and bordered by flange-like brims. The 6-8 denticles of the biade can be either distinct or quite completeIy fused with apices free. In the holotype the apices of the denticIes are partly abraded. The cusp is straight or slightly bent posteriorwards and higher than the denticIes. Remarks: Representatives of the species, often broken with regard to the Iarge dimension of the cup, occur in association with Isarcicella lobata, Is. staeschei and Is. isarcica. Forms with fused denticIes seem to be more frequent in stratigraphically higher levels. Is. inflata is differentiated from Is. lobata by the very much wider and inflated cup, and by the outer side ofthe cup being always great1y expanded. The species couId be derived from Is. lobata by extreme dilation ofthe cup and be the ancestor of Is. staeschei. MATSUDA (1981 : pl. 5, fig. l) figured a specimen assigned to Hindeodus parvus which can be incIuded in Is. inflata because of its very wide and inflated cupo 297

PERRI & FARABEGOLl: Conodonts across the Pennian - Triassic boundary in the Southem Alps

Occurrence: Werfen Fmn, Mazzin Mbr. Bulla section, sample BU27. Tesero section, samples TS23-TS25. R a n g e: lobata-isarcica zones: Lower Triassic, lower Scythian. Isarcicella isarcica (HUCKRIEDE 1958) (pl. 4, figs 1-6) 1958 1964 1970 1991 1993 1997 1999

Spathognathodus isarcica HUCKRlEDE: 162, pl. IO, fig. 7 Spathognathodus isarcicus HUCKRlEDE - STAESCHE: 288, fig. 64. Anchignathodus isarcicus (HUCKRIEDE) - SWEET: pl. I, figs 18-19. lsarcice/la isarcica morphotype 3 (HUCKRIEDE) - PERRI: 42, pl. 4, fig. l, p1.6, figs 1-3. lsarcice/la isarcica (Huckriede) - WANG & CAO: 254, pl. 55, figs 8-9. lsarcice/la isarcica (Huckriede) - WANG & WANG: 165, pl. 2, fig. I. lsarcice/la isarcica isarcica (HUCKRIEDE) - NICORA & PERRI: pl. 3, fig. 16.

Description: The Pa element is characterised by a wide and inflated cup bearing on both sides one or a series of nodes or denticles.

Derivatio nominis: In the Pa element the high asymmetrical inner side of the cup develops so as to form a laterallobe. Holotype: IC 1787-200961, figured in pl. 3, figs 21-23. Paratypes: ICI777-200965 figured in pl. 2, figs 13; ICI785-200967, ICI786-200963, ICI788-200966, IC1789-200962 figured in pl. 3, figs 15-20,24-29; IC176299175 figured in pl. 4, figs 12-14. Locus typicus: Tesero section close to Tesero Village, Province ofTrento, western Dolomites. Stratum typicum: Level ofsample TS23 in the Tesero section, 22.5 m from the base of the Werfen Fmn in the Mazzin Mbr. Repository: Museum G. Capellini, Dipartimento di Scienze della Terra e Geologico-Ambientali, University ofBologna. Material: 61 specimens.

Remarks: Like Isarcicella lobata and Is. staeschei, this species shows very wide intraspecific variability (PERRI 1991). It occurs in the Southern Alps after the entry of Is. staescheì - in the Bulla section sample BU27 at 45 m from the base ofthe Werfen Fmn, and in the Tesero section sample TS26 at 26 m. Occurrence: Werfen Fmn, Mazzin Mbr. Bulla section, sample BU27-BU27 A. Tesero section, sample TS26; San Pellegrino Pass section, sample SP2. Range: isarcica Zone: Lower Triassic, lower Scythian.

Isarcicella lobata n.sp. (pl. 2, figs 1-3; pl. 3, figs 15-29; pl. 4, figs 12-14) 1964 1981 1991 1991 1993 1995

1995 1996

1998

1999 1999

298

Spathognathodus isarcicus HUCKRIEDE - STAESCHE: text-fig. 61. Hindeodus parvus (KOZUR & PJATAKOVA) - MATSUDA: 91, pl. 5, fig. 3. Hindeodus parvus (KOZUR & PJATAKOVA) - SCHONLAUB: pl. l, fig. 3. lsarcice/la isarcica morphotype I (HUCKRIEDE) - PERRI: pl. 4, fig. 8. lsarcice/la turgida (KozuR, MOSTLER & RAHIMI-YAZD) - GULLO & KOZUR: fig. 2/2-3. lsarcice/la? turgida (KozUR, MOSTLER& RAHrMr-YAZD) - KOZUR: pl. 2, fig. 8. Hindeodus parvus (KOZUR & PJATAKOV A) -lsarcice/la Transition ? - METCALFE: pl. I, figs 12- 13. lsarcicella? turgida (KozuR, MOSTLER & RAHIMI-YAZD) - KOZUR: pl. 5, figs 7-8. Hindeodus parvus morphotype 2 (KOZUR & PJATAKOVA) trans. form lo lsarcice/la isarcica staeschei DAI & ZHANG - FARABEGOL! & PERRI: pl. 4.3.1, fig. 13. Hindeodus parvus erectus KOZUR - NICORA & PERRI: pl. 3, fig. 7. Hindeodus parvus parvus (KOZUR & PJATAKOVA) - NlcORA & PERRI: pl. 3, fig. 14.

D i a g n o s i s : The Pa element is characterised by an asymmetrical to highly asymmetrical swollen and thickened cup with a lateral bulge forming a lobe. The cup has no lateral nodes or denticI es. The cusp is higher than the succeeding denticles. Description: The blade bears 4-7 denticles rounded in section and discrete, and shows the attachment area ofthe denticles to be swollen. The wide cusp is twice as high as the denticles. The posterior end ofthe unit can be either adenticulate, abruptly ending, or denticulate with Iittle denticIes decreasing in height towards the posterior tipo The cup is always asymmetrical and swollen; it has a Iaterai buige forming an inflated Iobe on the inner side. The Iobe can be variousIy expressed because of high variability in the width of the cup. The outer side of the cup is usually more reduced than the inner side and may show undulations. Stratigraphically higher specimens can develop a secondary lobe on the outer side. The cup is always without laterai nodes or denticles. The pit tends to be centrally located. Remarks: Two morphotypes can be distinguished, morphotype 1 (pl. 3, figs 21-23) and morphotype 2 (pl. 3, figs 15-17), on whether or not the posterior end is abrupt or denticuiate. In laterai view the denticuiation is very close to that of other species such as Hìndeodus parvus, Isarcicella turgida and some elements ofIs. staeschei and Is. Isarcica. In specimens with the cup highIy expanded, the appearance is very cIo se to that of Is. staeschei and Is. Isarcica from which they are distinguished only by lack oflaterai nodes or denti cles. Is. lobata includes forms regarded as morphotype 1 ofthe apparatus of Is. isarcica by STAESCHE

Com. Forsch.-Inst. Senckenberg, 245, 2003

(1964), SWEEl (1977) and PFRRI (1991 ). Thc three morphotypes are discriminated by bearing on the cup l) no nodes or denticles, 2) one or a series of nodes or dentic1es on one side, 3) one or a series of nodes or denti cles on both sides. They were considered to be elements of a unique apparatus because of occurring consistently in association. Recent research such as on the Bulla and Tesero sections, brought out that the three forms enter at different stratigraphical levels. This implies branching into three discrete species. Specimens previously assigned to Ili. parl'lIS and 1.1'. tllrgida are here included in Is. lobata. As discussed under the remarks on those species, forms like that figured by GULLO & KOZUR (1993: fig. 2.3-3) and KOZUR (1995: pl. 2, fig. 8 and 1996, pl. 5, figs 7-8) - which have a much too asymmetrical and swollen cup to be referred to Is. tllrgida - have been assigned to Is. lobata. In PERRI'S opinion the GULLO & KOZtJR specimcn shows features not fitting with the originai diagnosis and characteristics of Is. turgida. Similarly, forms like that figured by MATSUrlA (1981: pl. 5, fig. 3) as Hi. parvus have to be included in Is. lobata. They were placed in Hi. parl'US because of the denticulation and cusp being c10se to Hi. parvus. though the basaI cavity was too widc and swollen to be Hi. parvus. Both morphotypes of Hi. parvus display an approximately symmetrical basaI cavity and no swelling. According to PERRI, forms with a swollen and asymmetrical cup recalling 1.1'. staeschei and 1.1'. isarcica ne ed to bc recognized as discretc species. The entry of Is. lobata moreover is stratigraphically higher than the entry of Is. turgida. Is. lobata oecurs in the Bulla section from sample BU23 at 30 m from thc base of the Werfcn Fmn up to 8U27 A at 46 m, and in the Tesero section from TS23 at 22.5 m to TS26 at 26 m. In both sections Is. lohata enters some metres below the first appearance of 1s. staeschei and co-occurs with Is. staeschei and the higher 1s. isarcica. The first oceurrence of Is. lohata has biostratigraphic significance and is uscd to define the base of a new biozone betwecn the parvus and staeschei zones.

Paratype: TCI775-989162 figurcd in p!. 1, figs 26-28. Loeus typicus: Bulla section at about 0.5 km along the road NW of the Bulla village, Province of Bolzano, Western Dolomites. Stratum typicum: Level ofsample BUIO ofthe Bulla section at 20 cm from the base ofthe Werfen Fmn in the Tesero Mbr. Repository: Museum G. Capellini, Dipartimento di Scienze della Terra e Geologico-Ambientali, University ofRologna. Material: 2 spccimens. Diagnosis: The Pa element is characterised by 5-6 very wide and discrete dcnticles with the profile of the apices extremely rounded. The wide and squat cusp, corresponding to about 1/3 ofthe unit length, is higher than the dentic1es. Some Iittle denticles or "germinai denticles" ean be present anterior to the cusp. The wide spoon-shaped basai cavity is slightly swollen. Description: Very robust, large formo Tn latera l view the profile of the denticles is straight with abruptly ending posterior tip in the juvenilc speeimen, whereas it is rounded prescnting dentielcs deereasing in height up to the posterior end in the adult element, the holotype. The very wide and straight eusp is twiee the height ofthe denticles. Cusp and dcnticles show striae. Thc widc spoon-shaped basai cavity is slightly asymmetrical, displaying a wcak swelling\thickening. The pit is located in the anteriorthird of the basai cavity.

Isarcicella peculiaris n. sp. (p!. l, figs 26-31)

Remarks: Even though only two specimens have been [ound, these have been assigned to a new species because ofthe extremcly pcculiar shape. The swelling ofthe basai cavity is close to that of Isarcicella prisca and Is. turgida. Is. peculiaris is dift'erentiated from Is. prisca by having a wider and squatter cusp occupying L~ of the length (p!. l, figs 26, 29) whereas in Is. prisco the cusp occupies only V. or the length. In the new species therc is no evidence ofthe largest denticles being located in the second half of the bIade; this is characteristie of Is. prisca. No conodont cJose to these forms has becn previously described and figured. The element assigned to Hindeodus cf. parvus parvus, figured and described by K07UR (1996: pl. 3, fig. Il), is a specimen with unusually broad, distally rounded denticles; it was obtained from a fioat bloek in Sicily (sample KS3). Tt resembles the new species only with respect to its denticJes.

Derivatio nominis: Referring to the extremelypeculiar shapc of thc Pa elemcnt of the species.

Occurrence: Werfen Fmn, Tesero Mbr. Bulla section, sample BUIO.

Ho I otype: ICI776-989157, figured in pl. 1, figs 29-31.

Range: Upper praeparvus Zone: upperrnost Permian.

Occurrence: Werfen Fmn, Mazzin Mbr. Bulla section, samples 8U23-BU27 A; Tesero section, samples TS23-TS26; San Pellegrino Pass section, sample SP2; Agordo-Frassené section, sample AF II. Range: lobata-isarcica zones: Lower Triassic, lower Scythian.

299

PERRI & FARABEGOLl: Conodonts across the Pennian - Triassic boundary in the Southem Alps

Isarcicella prisca KOZUR 1995 (pl. l, figs 20-25; p1. 2, figs 16-21) 1991 1995 1996 1998 1998

Hindeodus typicalis (SWEET) - PERRI: 40, pl. 3, figs l, 3, 4. Isarcicella? prisca KOZUR: 73, pl. 2, fig. l. Isarcicella? prisca KOZUR - KOZUR: lO l, pl. 4, fig. 9. Isarcicella? prisca morphotype l KOZUR - FARAREGOLI & PERRI: pl. 4.3.1, fig. 6. Isarcicella? prisca morphotype 2 KOZUR - FARABEGOLI & PERRI: pl. 4.3.1, fig. 7.

D e s c r i p t i o n: The Pa element has largest dentici es in the second half of the biade, a broad cusp, the inner side of the basai cavity distinctly thickened, and the rather broad outer si de less thickened. Remarks: KOZUR (1995) chose the specimen figured by PERRI (1991: pl. 3, fig. l, sample BUl O) as holotype ofthe species. Denticulation ofthe species is extremely close to that of HL praeparvus from which it can be distinguished by the sweIling and thickening ofthe basaI cavity, mainly on its inner side. Several specimens have been found in the studied material.1s. prisca has been utilised here to divide the praeparvus Zone into Lower and Upper praeparvus zones. The first occurrence ofIs. prisca is stratigraphicaIly higher than that of HL praeparvus and defines the base ofthe U. praeparvus Zone. In the Bulla section both Hi. praeparvus and 1s. prisca are present in sample BU9, the first productive sample, about 20 cm above the base ofthe Werfen Fmn In the Tesero section Is. prisca first occurs in sample TS9 whereas Hi. praeparvus is found lower in the sequence at sample TES62, 30 cm from the base of the Werfen Fmn (Fig. 4). In sections from the western Carnic Alps, beds ofthe Bellerophon Fmn producing Ri. praeparvus yielded no Is. prisca. The species can be divided into two morphotypes. Morphotype l includes all forms with the posterior tip ending abruptly, and morphotype 2 with tiny denticles occurring to the posteri or end. Occurrence: Werfen Fmn, Tesero Mbr. Bulla section, samples BU9-BUI2C; Tesero section, samples TS9, TESIOI. R a n g e: U pper praeparvus-parvus zones: uppermost Permian-Lower Triassic, lowermost Scythian.

Isarcicella staeschei DAI & ZHANG 1989 (pl. 3, figs 1-14; pl. 4, figs 7-9) 1964 1975 1981 1989

1991

300

Spathognathodus isarcicus HUCKRIEDE - STAESCIIE: 288, figs 62-63. lsarcicella isarcicus (HUCKRIEDE) - KozuR, MOSTLER & RAHIMIYAZD: 6, figs 4-5,8. lsarcicella isarcica (HUCKRIEDE) - MATSUDA: 93, pl. 5, figs 47. lsarcicella staeschei DAI & ZHANG: 430, pl. 45, figs 16-17, pl. 46, figs4-7, 11-13, 18-19, pl. 53, figs 13-14. Isarcicella isarcica morphotype 2 (HUCKRIEDE) - PERRI: 42, pl.

1993 1995 1997 1998 1998

1999

4, figs 2-6, pl. 5, figs 1-3, pl. 6, figs 4-5. Isarcicella isarcica (HUCKRIEOE) - TIAN: pl. I, figs 22-24. Isarcicella isarcica staeschei DAI & ZHANG - KOZUR: pl.6, fig. 18. Isarcicella staeschei DAI & ZHANG WANG & WANG: pl. 2, figs 2-5. Isarcicella isarcica staeschei DAI & ZHANG - FARABEGOLI & PERRI: pl. 4.3.1, figs 14-15. Isarcicella staeschei DAI & ZHANG - ORCHARO & KRYSTYN: pl. 6, figs 4-8, 10-12. lsarcicella isarcica staeschei DAI & ZHANG - NIl'ORA & PERRI: pl. 3, fig. 15.

Description: The Pa element is characterised by a very asymmetrical wide and inflated cup with a lateral lobe bearing one or a series of nodes or denticles. Remarks: The species shows high morphologic intraspecific variability (PERRI, 1991). In the Southem Alps it occurs first after the entry of 1sarcicella lobata at 43.60 m from the base of the Werfen Fmn in the Bulla section (sample BU25A) and at 24 m in the Tesero section (sample TS24). One element with a rudimentary latera1 denticle, found in the Tesero section (sample TS19) 14.30 m below the entry in abundance of Is. staeschei (sampleTS24), was previously assigned to 1s. isarcica morphotype 2 (= Is. staeschei) in PERRI (1991). Here it has been considered a transitional form towards Is. staeschei but not yet a true representative of that species because it displays no evidence of swelling of the basaI cavity. It is stressed that at the leve! of first occurrence of Is. staeschei in both the Bulla (sample BU25A) and Tesero (sample TS24) sections, forms with one denticle on one side ofthe cup have been found in association with e1ements showing a lateral series of denticles different from the first representatives of Is. staeschei - having a single lateral denticle - found in Spiti (India) and Kashmir (KOZUR 1996; WANG 1996; ORCHARD & KRYSTYN 1998). Moreover, in the Alps, Pa e1ements of Is. staeschei bearing more than one denticle on one side ofthe cup occur stratigraphically lower than Pa elements of Is. isarcica. Therefore the data from the Alps disagree with Kozur's (1996) opinion that the forms of Is. staschei bearing two or more denti cles exclusively co-occur with Is. isarcica and that only specimens with one denticle on one side ofthe cup have a different (lower) range probably representing a different taxon. Occurrence: Werfen Fmn, Mazzin Mbr. Bulla section, samples BU25A-27A; Tesero section, samples TS24-26; San Pellegrino Pass section, sample PSP2; Agordo-Frassené section, sample AF Il. Range: staeschei-isarcica zones: Lower Triassic, 10wer Scythian.

Coue Forsch.-Inst.

Isarcicella turgida (KozuR, MOSTLER & RAHIMI-YAZD 1975) (pl. 2, figs 13-15) 1975

1993 1995

1996

Anchigna/hodus lurgidus KOZUR, MOSTLER & RAHIMI-YAZD: 5. pL 7, figs 11-12. Isarcicella turgida (KOZUR, M05TLER & RAHIMI-YAlD)- GULLO & KOZUR: fig. 217-9. lsarcicella? turgida (KozuR, MOSTLER & RAHIJl.ll- YAlD)- KOZUR: 72, pl. 2, fig. 5. Isarcicella? turgida (KOZUR, MOSTLER & RAHIMI- YAlD) - KOlUR: p.IOO. pl. 4, fig. 8.

Descri ption: The Pa element has a thickened bIade and slightly asymmetrical basai cavity. The upper part of the swollen basai cavity is completely smooth, Rem arks: KOZUR (1975) defined Isarcicella turgida as a conodont with a swollen biade and a slightly asymmetrical basaI cavity. The description fits with the holotype (KOZUR 1975: pl. 7, fig. 12) in which the bIade is weakly inflated and the asymmetry ofthe basai cavity is unrecognisable. Together with the holotype, KOZUR (1975: pl. 7, fig, 11) figured another specimen with biade more swollen, but with the basai cavity always slightly asymmetrical. GULLO & KOZUR (1993: fig. 2/2-3) figured a specimen from the Sosio Valley ofSicily with a very wide asymmetrical and swollen cup, It was assigned to Is. furgida. KOZUR (1995, 1996) interpreted the species very broadly, enlarging the originaI concept to include forms like that found in Sicily which, subsequently, he took to be representative of Is. turgida. PERRI considers that form very different from the holotype of Is. turgida. In the studied material, specimens like that found in Sicily appear 13.60 m in the Bulla section and 1.5 m in the Tesero section below the first occurrence of Is. staeschei and co-occur with both Is. staeschei and Is. isarcica. According to PERRI'S point ofview, these forms - included in Is. lobata correspond to the adenticulate elements of morphotype I of the apparatus of Is. ìsarcica OfSTAESCHE (1964), SWEET (1977) and PERRI (1991) as discussed under the remarks on Is. lobala. They seem to derive from representatives of the species Is. turgida by increase in the width and asymmetry of the basaI cavity (which becomes a cup bearing a lobe). Here Is. turgida is restricted to forms dose to the originai diagnosis; more asymmetrical and inflated forms appearing stratigraphically higher have been assigned to Is. lobata. KOZUR (1995) indicated that the distinctive character for discriminating between Hi. parvus and Is. turgida is only the swelling of the biade; the denticulation is the same. Forms corresponding to the originai diagnosis of Is. turgida have been found in the Bulla section in the same level (BU13B) where Ili. parvus first occurs. These specimens in lateral view are very dose to HL parvus, but in upper view show slight asymmetry ofthe basai cavity, thickened mainly on the inner side. Occurrence: Werfen Fmn, Tesero and "\1azzin Mbrs.

245,2003

Bulla section, samples BUI2B, BU23; Tesero section, samples TSI9, TS23. Range: parvus-lobata zones: Lower Triassic, lower Scythian.

Acknowledgements We are deeply grateful to KIRIL BUDUROV and MIKE ORC'HARD for thoroughly rcvicwing the manuscript and making fruitful suggcstions, and to JOHN TALENT t'Or editing and criticai reading of the manuscript. We thank CARLO BRAZZOROTTO who undertook the heavy liquid separations, PAOLO FERRIERI who took SEM photos of conodonts, and Dr. BENIAMINO COSTANTI\\[ who helped generate the computer drawings. The Agorolo-Frassené and Maestrin sections were sampled with ALDA NICORA and the San Pellegrino Pass section with CLAUDIO NERI. PERRI is responsible for the conodont data and discussion; FARABEGOLI is responsible forthe geological and sedimentological parts ofthe paper; condusions were written in collaboration. The research was funded by ex 60% "\1URST grant to M.C. PERRI.

References ASSERETO, R.. BOSEl.L1NI, A.. FANTINI SESTlNI, N. & SWEET, W,c. (1973): Thc Pcrmian-Triassic boundary in thc Southcrn Alps (Italy).~ In: LUGAN, A. & HILLs, L.v. (eds): The Permian and Triassic Systems and thcir MutuaI Boundary. Memoirs of Alberta Society ofPetroleum Geologists, 2: 176- I 99. BOSEl.UNI, A. (1964): Stratigrafia, petrografia e sedimentologia delle facies carbonati che al limite Penniano-Trias nelle Dolomiti Occidentali,- Memorie del Museo di Storia Naturale della Venezia Tridentina. 15: 59- 110. BRACK. P., MUNDlL, R .. OBERLl, F., MEIER, M. & RIEBER, H. (1996): Biostratigraphic and radiometric age data question the Milankovitch characteristics of the Latemar cycles (Southern Alps, Italy).- Geology, 24(4): 371-3ì5. BRANUNER, R., DO/>;OFRIO, D.A., KRAI/>;ER, K .. MOSTLER, H" NAZARow, M.A., RESCH, W, STlNGL, V. & WEISSERT, H. (1986): PermianTriassic Boundary in the Southern Alps.-In: Field Conference on Permian-Triassic Boundary, South-Alpine Segment Western Tethys, and Additional Regional Reports.- Società Geologica Italiana, Abslracts: 15- I 6. BRANDNER, R. & MOSTLER H. (1982): Der geologische Aufbau des Schlerngebietes und seìner weìteren Umgcbung.-In: MOSTLER, H. (ed.): Jahrestagung der Osterreìchìschen Geologìschen Gesellschaft. Exkursionfurher.- Seis am Schlern, Slidtirol: 1-42. BROGLIO LoRlCiA, c.. CASSINIS, G" CONTI, M.A., D'AMICO, c., DEMELIA PITTAU, P., FONTANA, D., MARloln, N., MASSARI, F.. NERI, c., NICOSIA, U.• PASTNI, M .• POSENATO, R. & VENTl:RTNI, C. (eds)(1986): Pennian and PermianTriassie boundary in the South-Alpine segment of the Western Tethys. S.G.i., IGCP 203, Excursion Guidebook, 4-12 July 1986: 1-158; Pavia. BROGLIO LORIGA. c.. NERI, c., PASI"I, M. & POSE/>;ATO, R. (1986): The Upper Bellerophon Fm. and the PT boundary in the Sass de Putia Mt. (Dolomites).- In: BROCiL!O LORlCiA. C., CASSIN1S, G., CONTI, M.A., D'AMIco, C .. DEMELIA PITTAU, p" FO/>;TANA, D., MARIOTTI, N., MASSARI, F., NERI, c., NICOSIA, U., PASINI, M., PO