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A Bollettino della Società Paleontologica Italiana, 57 (2), 2018, 81-101. Modena

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Metapolygnathus parvus Kozur, 1972 (Conodonta): a potential primary marker for the Norian GSSP (Upper Triassic)

Michele Mazza, Alda Nicora & Manuel Rigo

M. Mazza, Università degli Studi di Milano, Dipartimento di Scienze della Terra “A. Desio”, Via L. Mangiagalli 34, I-20133 Milano, Italy; [email protected] A. Nicora, Università degli Studi di Milano, Dipartimento di Scienze della Terra “A. Desio”, Via L. Mangiagalli 34, I-20133 Milano, Italy; [email protected] M. Rigo, Università degli Studi di Padova, Dipartimento di Geoscienze, Via G. Gradenigo 6, I-35131 Padova, Italy; IGG-CNR, Via G. Gradenigo 6, I-35131 Padova, Italy; [email protected]

KEY WORDS - Conodonts, Global Boundary Stratotype Section and Point, Carnian-Norian, Late Triassic, Pizzo Mondello, Black Bear Ridge.

ABSTRACT - The base of the Norian Stage (Carnian/Norian boundary, Upper Triassic) is still awaiting a formal designation by the International Commission on Stratigraphy. At present, two stratigraphic sections, Pizzo Mondello (Sicily, Italy) and Black Bear Ridge (British Columbia, Canada), have been proposed as GSSP (Global Stratotype Section and Point) candidates for the base of the Norian, but a bio- or physical primary marker event has not been yet selected by the Working Groups. We show here that conodonts represent the best choice to define the Carnian/Norian boundary. In the Upper Triassic, in fact, conodonts have been studied in great detail in the last 15 years providing a very high resolution biostratigraphic tool. We illustrate here the phylogenetic lineage Metapolygnathus praecommunisti - Metapolygnathus dylani - Metapolygnathus parvus, demonstrating that this lineage is present in both the GSSP candidate sections. Thus, we propose the First Occurrence (FO) of Metapolygnathus parvus (the last representative of its lineage) as a potential primary marker to define the base of the Norian Stage. Metapolygnathus parvus is in fact the most reliable and useful biomarker, because this species is morphologically simple and easy to recognise and its First Appearance Datum (FAD) is globally recognisable within its phylogenetic lineage. The FO of M. parvus also coincides with an important global conodont faunal turnover (known as T2), that corresponds to the disappearance of the typically Carnian conodont genus Carnepigondolella and the rise of the genus Metapolygnathus. In addition, the FO 13 of M. parvus occurs very close to a brief positive δ Ccarb shift, documented in the two GSSP candidate sections and in the uppermost part of the magnetozone PM4n (ca. at 3.20 m below the top) at Pizzo Mondello.

RIASSUNTO - [Metapolygnathus parvus Kozur, 1972 (Conodonta): un potenziale bioevento principale per la definizione del GSSP del Norico (Triassico Superiore)] - La base del Norico (limite Carnico/Norico, Triassico Superiore) deve ancora essere formalmente designata dalla Commissione Internazionale di Stratigrafia. Attualmente, due sezioni stratigrafiche sono state proposte come possibili candidate per il GSSP (Global Stratotype Section and Point) del Norico: Pizzo Mondello (Sicilia, Italia) e Black Bear Ridge (Columbia Britannica, Canada). In questo lavoro si vuole mostrare come un bioevento basato su conodonti possa essere la scelta più appropriata per definire il limite Carnico/Norico. Nel Triassico Superiore, infatti, i conodonti sono stati studiati in grande dettaglio durante gli ultimi 15 anni e offrono ormai uno strumento biostratigrafico ad altissima risoluzione. In questo lavoro gli Autori illustrano la linea filogenetica rappresentata da Metapolygnathus praecommunisti - Metapolygnathus dylani - Metapolygnathus parvus e dimostrano come questa sia presente in entrambe le sezioni candidate a GSSP. Per questo motivo, si intende qui proporre la Prima Comparsa (FO = First Occurrence) di M. parvus, l’ultimo rappresentante della sua linea filetica, come evento principale per la definizione della base del Norico.Metapolygnathus parvus rappresenta infatti il biomarker ideale e più affidabile, perché questa specie è morfologicamente semplice e quindi facile da riconoscere e il suo First Appearance Datum (FAD) è riconoscibile globalmente all’interno della sua intera linea filogenetica. Il FO di M. parvus corrisponde inoltre ad un importante cambiamento globale nelle faune a conodonti, conosciuto come Turnover 2 (T2), che è caratterizzato dalla scomparsa del genere tipicamente Carnico Carnepigondolella e dalla proliferazione in massa del genere 13 Metapolygnathus. Infine, il FO diM. parvus si trova vicino ad uno shift positivo del δ Ccarb documentato in entrambe le successioni stratigrafiche candidate per la base del Norico ed al tetto della magnetozona PM4n (circa 3,20 m dal tetto) nella sezione di Pizzo Mondello.

INTRODUCTION defining thus the base of the Triassic System. The FAD of M. posthernsteini (Kozur & Mock, 1974) has been Conodonts are the primary fossil group for detailed proposed as primary biomarker for the Rhaetian Stage biostratigraphy for large part of the Palaeozoic Era and (Krystyn, 2010; Gradstein et al., 2012; Bertinelli et for the definition of many Palaeozoic GSSPs (e.g., see al., 2016; Rigo et al., 2016). Conodonts have been also tabs 20.3, 22.3, 23.4 and 24.3 in Gradstein et al., 2012; suggested to recognise the base of the Anisian, with the Rigo et al., 2018). However, in the Triassic, conodonts lowest occurrence of Chiosella timorensis (Nogami, 1968) seem to be overlooked when compared with other fossil (Orchard & Tozer, 1997; Gradinaru et al., 2007; Orchard, groups (i.e., ammonoids and bivalves), or even considered 2010) and the base of the Olenekian with the lowest unreliable for a refined biostratigraphy (Lucas, 2016). occurrence of Neospathodus waageni Sweet, 1970 sensu Actually, also for the Triassic System conodonts provide lato (Krystyn et al., 2007; Orchard, 2007; Ogg, 2012), fundamental biostratigraphic tools to define several stages. even if the validity of these two conodont bioevents is For instance, they are used to mark the Induan GSSP under debate. with the First Appearance Datum (FAD) of Hindeodus In recent years, researchers have reached an incredible parvus (Kozur & Pjatakova, 1975) (Yin et al., 2001), level of detail in the biostratigraphy and phylogenesis of

ISSN 0375-7633 doi:10.4435/BSPI.2018.06 82 Bollettino della Società Paleontologica Italiana, 57 (2), 2018

Fig. 1 - Late Triassic palaeogeography showing key basins presented in the text. 1) Pizzo Mondello, Sicani Basin, Italy; 2) Gianni Grieco section, Lagonegro Basin, Italy; 3) Bölücektasi Tepe, Erenkolu Mezarlik, Turkey; 4) Csővár Borehole, Hungary; 5) Silická Brezová, Slovakia; 6) Black Bear Ridge, Bristish Columbia, Canada. Map modified from http://www.scotese.com. the Upper Triassic conodonts, mainly due to the necessity Being the two sections from different latitudes and of defining stage boundaries, such the Carnian/Norian basins (Fig. 1), the conodont faunas reveal specific (Nicora et al., 2007; Orchard, 2007, 2010, 2014; Balini differences related to endemism and these have caused, et al., 2010a; Rigo et al., 2018) and Norian/Rhaetian during the years, divergences among specialists concerning boundaries (Giordano et al., 2010; Bertinelli et al., 2016; their taxonomy and systematics. In spite of the differences, Rigo et al., 2016). We demonstrate here that a conodont the occurrence of a Metapolygnathus Hayashi (1968) bioevent is the most preferable marker to define the base species, such as the First Occurence (FO) of M. parvus of the Norian Stage, illustrating the great detail reached Kozur, 1972 or M. echinatus (Hayashi, 1968), has been in the knowledge of the conodont biostratigraphy across suggested since 2007 as a possible marker for the base the Carnian/Norian boundary in both the GSSP candidate of the Norian Stage (Nicora et al., 2007; Orchard, 2007). sections of the Norian Stage: Pizzo Mondello (Nicora et It is now possible to recognise in both sections common al., 2007; Balini et al., 2010a, 2015; Mazza et al., 2010, species and important phylogenetic lineages among 2011, 2012a, b; Mazza & Martínez-Pérez, 2015) and the cosmopolitan forms, thus allowing identification of Black Bear Ridge (Orchard et al., 2001; McRoberts, 2007; comparable conodont bioevents and turnovers (Mazza et Orchard, 2007, 2014; Balini et al., 2015). In the Black Bear al., 2010; Orchard, 2014; Rigo et al., 2018). In particular, Ridge section (BBR), located in northern British Columbia it is possible to recognise in both Tethyan and open (Canada), conodonts have been studied by Orchard for Panthalassic provinces the entire lineage of M. parvus, over 35 years, while in the Pizzo Mondello section (PM), descendent of M. dylani Orchard, 2014 (Orchard, 2014). western Sicily (Italy), conodonts have been investigated For this reason, we suggest here that the FO of the for over 15 years by Italian teams. In both these two conodont M. parvus should be considered a potential candidate sections, the rich conodont record is supported primary marker to define the base of the Norian Stage. by the bivalve Halobia Bronn, 1830 (McRoberts, 2007, 2011; Levera et al., 2012) and ammonoid biostratigraphy (Nicora et al., 2007; Balini et al., 2010a, 2012; Orchard, THE CONODONT FAUNAS AND 2014), along with radiolarian associations (Nicora et al., MAIN BIOEVENTS OF PIZZO MONDELLO 2007; Carter & Orchard, 2013), even though ammonoids AND BLACK BEAR RIDGE occur sporadically in both sections. Besides the detailed biostratigraphic investigations, PM and BBR have been Correlations between the Pizzo Mondello and studied for stable isotopes (Muttoni et al., 2004; Williford Black Bear Ridge conodont records have always been et al., 2007; Mazza et al., 2010; Rigo et al., 2012; Onoue et quite problematic. This was primarily because of the al., 2015; Trotter et al., 2015), while magnetostratigraphy differing palaeoecological environments in which the is documented only at PM (e.g., Muttoni et al., 2001, 2004, two successions were deposited. Pizzo Mondello was 2014), because at BBR the original geomagnetic signal sedimented in a pelagic environment in the western has been overprinted by regional heating (Muttoni et al., branch of the Neotethys (open gulf on the eastern side 2001; Zonneveld et al., 2010). of Pangea) (Fig. 1), at a position of ca. 22° (15°-29°) M. Mazza et alii - Metapolygnathus parvus as a marker for the base of the Norian 83 north latitude (Muttoni et al., 2004). The sequence Apart these few systematic issues, it is instead that represents the Carnian-Norian interval consists of possible to find many common species, evolutionary cherty limestones belonging to the Scillato Formation morphological trends, and comparable conodont bioevents (Muttoni et al., 2001, 2004; Nicora et al., 2007). between Tethys and North America. In 2010, Mazza et Black Bear Ridge, instead, was deposited at a higher al. recognised three major faunal turnovers in the Pizzo palaeolatitude (above 45°N from www.scotese.com), and Mondello Carnian/Norian conodont record that have been the sequence is composed by the Ludington and Pardonet later extended also in other parts of the Tethys (Mazza & formations, which represent a deep water slope and Krystyn, 2015), and that have been updated hereafter (Fig. basin setting at the western edge of Pangea (Zonneveld 2). These events are: et al., 2010; Orchard, 2014) (Fig. 1). These different palaeogeographic contexts are the origin of endemic T1: placed at sample FNP88a (Fig. 2), close to the taxa in the two sections (according also to Orchard, top of the Carnepigondolella orchardi Zone (Rigo 2014), making correlations problematic. In addition, the et al., 2018). In this turnover almost all the species different taxonomic approaches, based on contrasting belonging to the genera Carnepigondolella, Hayashiella interpretations given to the conodont morphological Kiliҫ et al., 2015, and Paragondolella Mosher, 1968 characters used for their classifications by the various disappear and are replaced by the first species of the specialists, have produced apparent taxonomical genus Epigondolella Mosher, 1968, which will become dissimilarities that have been greatly solved during dominant in the Norian. more recent years (Mazza et al., 2012b; Orchard, 2014; Rigo et al., 2018). For instance, Orchard (2014), in his T2: placed between samples FNP117b and NA35 taxonomic approach, assigned several species previously at PM section (this datum is updated from Mazza et al. belonging to genera Carnepigondolella Kozur, 2003, [2010] after a further detailed sampling), it approximates Metapolygnathus Hayashi, 1968, and Paragondolella the base of the Metapolygnathus parvus Zone (Fig. 2) Mosher, 1968 to the new genus Quadralella Orchard, (Rigo et al., 2018). It shows the mass occurrence of the 2013, and some carnepigondellids to the new genus genus Metapolygnathus, with rich faunas dominated by Primatella Orchard, 2013. Particularly problematic is M. communisti Hayashi, 1968 and M. parvus (Tab. 1), the genus Quadralella, which gathers together species and coincides with the definitive extinction of the last from three other genera that have different morphological rare representatives of the genus Carnepigondolella (i.e., features and ages, thus lacking well defined diagnostic C. pseudodiebeli [Kozur, 1972], C. orchardi [Kozur, characters and/or a clear type species, creating a very 2003] and C. pseudoechinata [Kozur, 1990]) and the first morphologically variable and long ranging genus epigondolellids (i.e., Epigondolella heinzi Mazza, Cau spanning from the base of the Carnian to the base of the & Rigo, 2012a and Epigondolella miettoi Mazza, Cau & Norian (Chen et al., 2015). Another problem related to Rigo, 2012a). At this turnover, the genus Metapolygnathus Quadralella is its nomenclature. Quadralella lobata is is absolutely dominant over Epigondolella, as shown by suggested as the type species of the genus Quadralella the thicker range lines in Fig. 2. in Orchard (2013) and its descendent Q. postlobata was described in Orchard (2014). In 2015, Chen et al. T3: placed in correspondence of sample FNP135.1 illustrated the stratigraphic range of Q. lobata and Q. at PM (updated from Mazza et al., 2010 after a postlobata, which are both Tuvalian 3 (late Carnian) in further detailed sampling), it approximates the base age. Chen et al. (2015) also illustrated the distribution of the ?Carnepigondolella gulloae Zone (Rigo et al., of Quadralella lobatus, which was previously described 2018) (Fig. 2) and it marks the disappearance of the as Metapolygnathus lobatus in Orchard (2007), genus Metapolygnathus, which is replaced in younger from the early Julian (early Carnian). But assigning strata by a new rich conodont population, probably this metapolygnathid to Quadralella represents a belonging to a new genus, which shows intermediate nomenclature problem and creates a case of homonymy. morphologies between the Tuvalian carnepigondolellids In fact, the lower Julian M. lobatus (Chen et al., 2015) and paragondolellids. For this reason, we refer this should become Quadralella lobata and not Quadralella population to ?Carnepigondolella. All these forms are thus lobatus, as lobatus (male) is wrongly declined from Latin resembled in the ?Carnepigondolella gulloae population because Quadralella is a female name. It is also notable in Mazza et al. (2012b) (see also Rigo et al., 2018). This to report that lobatus, which means lobate, derives from turnover also corresponds to the occurrence of abundant the Greek word λοβός (= lobos), and not from the “new epigondolellids (which will dominate the rest of the latin lobat” as stated in Orchard (2013, p. 456). Thus, the Lacian), together with some representatives of the genus Julian Quadralella (ex Metapolygnathus) lobatus should Norigondolella Kozur, 1989 (see figs 2-3 in Mazza et al., be named Quadralella lobata. So, in Chen et al. (2015) 2010, and fig. 6.4 in Rigo et al., 2018). two different Quadralella lobata have been described: one is early Julian (i.e., ex Metapolygnahtus lobatus, Turnover T1 is partially an endemic event of the Orchard et al., 2007) and one is latest Tuvalian in age Tethys, because the genus Epigondolella seems to (i.e., Quadralella lobata Orchard, 2013), and they are occur later in the Norian in North America than in the not related phylogenetically (as highlighted in Chen et Tethys, where it first appears instead in the latermost al., 2015, text and fig. 3), but still have the same name Carnian. Turnovers T2 and T3 can instead be recognised and different stratigraphic ranges and, thus, these two also at BBR, and they thus represent key bioevents for species should be considered homonyms. Quadralella is comparisons between the conodont records of the two therefore a problematic genus that should be dismissed. Norian GSSP candidates (Fig. 2). 84 Bollettino della Società Paleontologica Italiana, 57 (2), 2018

Fig. 2 (color online) - Correlation of turnovers T1, T2 and T3 between Pizzo Mondello (Sicily, Italy) and Black Bear Ridge (northern British Columbia, Canada). The thickness of the range lines represents the relative abundances of the conodont genera. Sections are not at the same scale. Data for Black Bear Ridge are interpreted from Orchard (2014).

Turnover 1 (T1) level 13 (Fig. 3) fit with the morphological features of According to Orchard (2014), the Tuvalian conodont true M. praecommunisti and, thus, they can be ascribed faunas are mostly similar both at BBR and PM, with to the original species described by Mazza et al. (2011) many common species like Hayashiella carpathica (Fig. 4; Pl. 1, figs 1-3), and do not need to be left in open (Mock, 1979), H. tuvalica (Mazza & Rigo in Mazza et nomenclature (Orchard, 2014). Hence, M. praecommunisti al., 2012b), Carnepigondolella samueli (Orchard, 1991), is typically present in the lower Tuvalian of both PM and C. pseudodiebeli, C. zoae (Orchard, 1991), C. angulata BBR sections (Figs 3-4). Another important species that Mazza, Cau & Rigo, 2012a, C. orchardi, Metapolygnathus can be found in the Tuvalian interval of both sections is dylani, and M. praecommunisti Mazza, Rigo & Nicora, M. dylani, being part of the phylogenetic lineage to M. 2011. The last species is reported to occur higher in the parvus. The same Orchard (2014), placed a specimen of Tuvalian at BBR (i.e., M. praecommunisti praecommunisti M. praecommunisti at PM in synonymy with M. dylani at level 13a; table 5 in Orchard [2014]) than at PM (level (see Systematic Palaeontology) and it is now better NA4), but the forms assigned by Orchard (2014) to M. documented also at PM (Pl. 1, figs 4-6; Pl. 2, figs 1-6). The ex gr. communisti morphotypes 1-4 from level D to reassignment of some specimens of M. praecommunisti

Tab. 1 (color online) - Range chart of the species belonging to the Metapolygnathus parvus Kozur, 1972 phylogenetic lineage at Pizzo Mondello section (western Sicily, Italy) with the number of specimens per sample. Also the relative abundances of M. communisti Hayashi, 1968 are reported to show the entity of the mass occurrence of the metapolygnathids in correspondence of Turnover 2 (thick line, in red in the color online version). Only the productive samples are reported. M. Mazza et alii - Metapolygnathus parvus as a marker for the base of the Norian 85

species

M. parvus = M. parvus M. echinatus = M. parvus M. parvus gamma

samples M. praecommunisti M. dylani M. communisti sensu Orchard (2014) beta sensu Orchard (2014) sensu Orchard (2014)

NA 43 cf. PM 31 1 FNP 138.1 1 2 1 1 FNP 135.1 1 FNP 135a 10 7 1 FNP 135 1 FNP 134 6 NA 104 23 NA 103 15 NA 40 34 NA 40a 13 8 NA 102 40 6 FNP 130 14 2 1 NA 39 64 14 1 FNP 132.1 2 PM 28a 2 NA 38 11 9 3 FNP 125 14 12 NA 37 24 2 NA 36b 24 1 NA 36 22 1 30 AM 24 9 2 PM26a cf. 5 NA 35 5 transitional 3 2 FNP 117 1 2 NA 34 1 NA 31 1 NA 28a 1 FNP 88 1 FNP 88a 1 NA 26b 1 NA 24b 2 NA 24 2 NA 22c 1 NA 22 1 PM 15b 1 FNP 59 1 NA 21 1 FNP 53a 1 FNP 53 6 FNP 52 2 FNP 51a 3 NA 19 13 4 NA 18 1 NA 17a 1 NA 17 1 NA 16 1 NA 15a 4 PM 11a 4 NA 15 7 NA 14 10 1 NA 12 2 NA 11 3 PM 6a 3 NA 9 1 NA 8 2 NA 4 1 83 9 341 67 39 1 86 Bollettino della Società Paleontologica Italiana, 57 (2), 2018

Fig. 3 - Evolution and proposed phylogenetic relationships of Metapolygnathus praecommunisti Mazza, Rigo & Nicora, 2011, M. communisti Hayashi, 1968, M. dylani Orchard, 2014, and M. parvus, Kozur, 1972 at Black Bear Ridge section, northern British Columbia, Canada. The figure is modified after Orchard (2014, fig. 13); names of figured specimens have been modified according to the present taxonomy, but original designations have been kept in brackets. Conodonts are not in scale. M. Mazza et alii - Metapolygnathus parvus as a marker for the base of the Norian 87

Fig. 4 - Evolution and phylogenetic relationships of Metapolygnathus praecommunisti Mazza, Rigo & Nicora, 2011, M. communisti Hayashi, 1968, M. dylani Orchard, 2014, and M. parvus Kozur, 1972 at Pizzo Mondello section, Sicani Mountains, western Sicily (Italy). The figure is drawn based on the model of fig. 13 of Orchard (2014) for a better comparison between the conodont ranges and evolution in the two sections. Empty circles in the M. dylani range indicate transitional forms, while empty circle in the M. communisti range refers to M. cf. communisti. Conodonts are not in scale. to M. dylani does not affect the already existing conodont dominate the late Tuvalian, the rise of the epigondolellids distributions at PM (see Mazza & Martínez-Pérez, 2015 (Mazza et al., 2010) (Fig. 2), and a peculiar morphological for the last updated range chart). evolution of some conodont platform elements. This The first faunal turnover T1 occurs in the upper evolutionary event consists in the shortening of the Tuvalian at PM (Mazza et al., 2010) but Orchard (2014, platform and the development of sharp nodes on the p. 39, fig. 5) stated that “T1 does not obviously occur at platform margins of several species such as Epigondolella BBR, it might align in a position within the samueli Zone heinzi and Carnepigondolella pseudoechinata at PM where Tethyan diversification of the Carnepigondolella (C. orchardi Zone; Rigo et al., 2018), and C. milanae stock may have occurred”. However, his proposed position Orchard, 2014, C. spenceri Orchard, 2014, and C. of T1 at BBR is incorrect. medioconstricta Orchard, 2013 at BBR. At BBR, the FO T1 is easily recognisable in both the palaeogeographic of C. spenceri marks the beginning of the C. spenceri provinces (PM and BBR), since it mainly corresponds Subzone, which is about only one-metre-thick and, in the with the disappearance of the carnepigondolellids, which overlying Acuminatella sagittale - Parapetella beattyi 88 Bollettino della Società Paleontologica Italiana, 57 (2), 2018

Subzone of Orchard (2014) there is a significant faunal linguiformis Hayashi, 1968. However, M. linguiformis turnover comparable to the PM T1 event (Fig. 2), that was established in 1968 and, thus, it is Pr. bifida that has can be probably extended to most of the Tethys (Mazza to be considered a junior synonym of M. linguiformis and & Krystyn, 2015). As reported at p. 31 of Orchard (2014), not the opposite. Thus, the M. parvus Subzone of Orchard “this ~ 5 m interval heralds a major change in the conodont (2014) coincides in conodont faunal content and samples fauna following the disappearance of Carnepigondolella, richness (i.e., high conodont ecological proliferation) with the abundant appearance of Parapetella, and the the M. parvus Zone of Rigo et al. (2018) (NA 35-FNP134), increasingly common occurrence of both Acuminatella and PM event T2 can be approximated by its base (Figs 2, 13 and Primatella”. Thus, at the base of the Acuminatella 5). Furthermore, a short positive shift of δ Ccarb recorded sagittale - Parapetella beattyi Subzone in BBR, at both PM and BBR sections independently supports the carnepigondolellids disappear exactly as in the T1 event correlation of Turnover 2 (Fig. 5). documented at PM. The absence of the epigondolellids in the BBR section during event T1 may be related to Turnover 3 (T3) the proliferation of the endemic North American genera Turnover 3 at BBR is regarded as close to the base of mentioned above, which are absent in the Tethys, allowing the Primatella asymmetrica - Norigondolella Subzone of the epigondolellids to proliferate earlier in the Tethys. the P. primitia Zone (fig. 5, Orchard, 2014). This turnover Thus, the position of event T1 can be placed at the base of corresponds in both sections with the disappearance of the the Acuminatella sagittale - Parapetella beattyi Subzone genus Metapolygnathus (Fig. 2). At PM, there is the rise at BBR (Fig. 2). of endemic species belonging to the ?Carnepigondolella gulloae population and advanced epigondolellids, Turnover 2 (T2) that are assigned to E. rigoi Noyan & Kozur, 2007, The late Tuvalian conodont faunas may be slightly E. quadrata Orchard, 1991, E. triangularis (Budurov, different in the two palaeogeographic regions due to the 1972), E. uniformis (Orchard, 1991), plus Norigondolella endemic bioevents described above, but from T2 the two trinacriae Mazza, Cau & Rigo, 2012a. In this interval provinces are easily comparable. According to Orchard at BBR the conodont faunas are dominated by species (2014, p. 38-39), event T2 probably approximates the belonging to the genera Primatella Orchard, 2013 and samueli - primitia zonal boundary at BBR, but actually Norigondolella. They are Pr. circulare Orchard, 2014, T2 was originally defined by Mazza et al. (2010) by the Pr. permica (Hayashi, 1968), Pr. subquadrata Orchard, rise of the genus Metapolygnathus along with a high 2014, Pr. rotunda Orchard, 2014, Pr. triangulare Orchard, conodont productivity in the samples. This bioevent is 2014 that we assign here to E. rigoi (fig. 68 of Orchard, misinterpreted in Orchard (2014), as it can be perfectly 2014), and Norigondolella norica Orchard, 2014. Above recognised at BBR between the top of the Ac. acuminate this last turnover, the epigondolellids become dominant - Pa. prominens Subzone and the base of the M. parvus in both sections (Fig. 2). Zone (Fig. 2). At this level, samples become abruptly much more productive (Orchard, 2014, p. 6, fig. 5) and there As described above, the conodont records of PM and is the occurrence of true M. communisti and M. parvus, BBR are largely comparable and, even though there are along with new species that are assignable to Tethyan some systematic differences, the main bioevents can be morphotypes of the M. communisti fauna (Pl. 3), such as compared from a morphological perspective (Figs 2-5). Parapetella pumilio Orchard, 2014, Pa. irwini Orchard, The two regions show fully comparable early-middle 2014, Pa. johnpauli Orchard, 2014, and Pa. willifordi Tuvalian conodont faunas (developed after the crisis Orchard, 2014 (Orchard, 2014, figs 6-7). Orchard (2014, related to the humid events known as CPE - Carnial Pluvial p. 39) confirms this trend by recognising one specimen of Episode occurred at the Julian1/Julian2 boundary (Rigo et Pa. irwini within the M. communisti population at PM (i.e., al., 2007, 2012; Rigo & Joachimski, 2010; Trotter et al., pl. 8, fig. 6 in Mazza et al., 2012b) and also Primatella 2015), but late Tuvalian faunas are merely different due to bifida Orchard, 2014, which was considered by Orchard endemism. T1 and T3 can be partially recognised because (2014) (p. 39) as a junior synonym of Metapolygnathus the corresponding intervals documented endemic faunas in

EXPLANATION OF PLATE 1 Conodonts belonging to the phylogenetic lineage Metapolygnathus praecommunisti Mazza, Rigo & Nicora, 2011 - M. dylani Orchard, 2014, from the Pizzo Mondello section (Sicily, Italy). Fig. 1 - Metapolygnathus praecommunisti transitional to M. dylani; sample NA14. Micro-Unimi no. 2020. Fig. 2 - Metapolygnathus praecommunisti; sample NA19 (from Mazza et al., 2011). Micro-Unimi no. 2045. Fig. 3 - Metapolygnathus praecommunisti transitional to M. dylani; sample NA19. Micro-Unimi no. 2032. Fig. 4 - Metapolygnathus cf. dylani; sample NA19. Micro-Unimi no. 2031. Figs 5-6 - Metapolygnathus dylani. 5 - First Occurrence (FO); sample NA19 (from Mazza et al., 2011). Micro-Unimi no. 2044. 6 - Adult specimen, typical morphology; sample FNP53. Micro-Unimi no. 2046. For each specimen, all the three views are provided: a) upper view; b) lateral view; c) lower view. Scale bar corresponds to 200 µm, all the specimens are at the same scale. M. Mazza et alii - Metapolygnathus parvus as a marker for the base of the Norian Pl.89 1 90 Bollettino della Società Paleontologica Italiana, 57 (2), 2018 both regions. T2 is instead fully recognisable and can be 2014 Metapolygnathus ex gr. communisti (Hayashi) morph. 4 correlatable between both sections, being coincident with Orchard, p. 68, Fig. 46: 10-12. an important ecological faunal event, that is characterised 2014 Metapolygnathus ex gr. communisti (Hayashi) morph. 5 by the proliferation of the genus Metapolygnathus, or taxa Orchard, p. 68, Fig. 46: 16-18. morphologically comparable, and the demise of all the 2014 Quadralella praecommunisti praecommunisti (Mazza, Rigo & Nicora) - Orchard, p. 120, Fig. 85: 16-36. typical Carnian taxa. Material - See Tab. 1. SYSTEMATIC PALAEONTOLOGY Locus typicus and Stratum typicum - Pizzo Mondello In this section, we present and discuss the Systematic section (Monti Sicani, Western Sicily, Italy), bed NA12 Palaeontology of Metapolygnathus species, i.e., M. inside the Scillato Formation (i.e., cherty limestones). praecommunisti, M. dylani, M. parvus, and M. echinatus, that are of key importance to the Carnian/Norian boundary Description - “The platform is relatively short (2/3 definition. of the element), slender, with sub-parallel margins and a rounded posterior end. The anterior trough margin is wide and free blade of only 1-2 denticles. The platform margins Phylum Chordata Bateson, 1886 are thick and they bear three tiny nodes on the inner Subphylum Vertebrata Linneus, 1758 side and 2-3 nodes on the outer side at the geniculation Class Conodonta Eichenberg, 1930 point. Both the margins and the nodes are covered by an Order Ozarkodinida Dzik, 1976 intense microcrenulation. The cusp is undistinguished in Family Gondolelloidea Lindström, 1970 size and it is followed by a posterior carina composed of 2-3 nodes. In terminal or sub-terminal position, a larger Genus Metapolygnathus Hayashi, 1968 carinal node is always present. The pit is centrally located Type species Metapolygnathus communisti Hayashi, 1968 or slightly backwardly shifted with respect to the middle of the platform. An evident prolongation of the keel behind Metapolygnathus praecommunisti the pit is always present. The keel termination may be Mazza, Rigo & Nicora, 2011 pointed, squared or rounded and it is often deformed, (Pl. 1, figs 1-3) presenting a typical asymmetric shape. The basal cavity is narrow. Laterally, the element is slightly arched. The 1991 Metapolygnathus communisti Hayashi - Orchard, Pl. 2, blade is anteriorly high and it descends gradually in a figs 18-20. low and long carina that reaches the posterior end of the 2007 Metapolygnathus communisti Hayashi - Moix et al., Pl. platform. A low step occurs at the geniculation point” 1, figs 11-12. (Mazza et al., 2012b, p. 117). 2007b Metapolygnathus n. sp. Y Orchard, Pl. 2, figs 37-39. 2007 Metapolygnathus communisti Hayashi - Rigo et al., Fig. 5/4. Discussion - The intraspecific variability of M. 2010 Metapolygnathus praecommunisti n. sp. Mazza, Furin, praecommunisti within the morphocline between P. Spötl & Rigo, Pl. 1, fig. 6. noah (Hayashi, 1968) and M. communisti is quite high * 2011 Metapolygnathus praecommunisti Mazza, Rigo & Nicora, (Mazza et al., 2011). Further investigations of the Tuvalian p. 124, Figs 2/C-G, I-J (only), 3/B-H (only). interval of Pizzo Mondello confirmed that some specimens 2014 Metapolygnathus ex gr. communisti (Hayashi) morph. 1 Orchard, p. 66, Fig. 46: 1-3. previously referred to M. praecommunisti fit actually in 2014 Metapolygnathus ex gr. communisti (Hayashi) morph. 2 Orchard’s definition of M. dylani (Pl. 1, figs 5-6; Pl. 2, Orchard, p. 66, 68, Fig. 46: 4-6. figs 1-6). Nevertheless, the revision of all the forms of 2014 Metapolygnathus ex gr. communisti (Hayashi) morph. 3 M. praecommunisti at PM does not affect the present Orchard, p. 68, Fig. 46: 7-9. conodont distribution in the section.

EXPLANATION OF PLATE 2 Advanced specimens of Metapolygnathus dylani Orchard, 2014 and First Occurrence (FO) of Metapolygnathus parvus Kozur, 1972 from the Pizzo Mondello section (Sicily, Italy). Figs 1-5 - Metapolygnathus dylani. 1 - Adult specimen with incipient nodes at the geniculation point; sample FNP88a. Micro-Unimi no. 2033. 2 - Juvenile specimen; sample NA28a. Micro-Unimi no. 2034. 3 - Adult specimen, evolved form; sample NA31. Micro-Unimi no. 2025. 4 - Late juvenile specimen, transitional to Metapolygnathus parvus; sample FNP117. Micro-Unimi no. 2026. 5 - Late juvenile specimen, transitional to Metapolygnathus parvus; sample NA35. Micro-Unimi no. 2047. Fig. 6 - Transitional form Metapolygnathus dylani - M. parvus; sample PM26a. Micro-Unimi no. 2050. Fig. 7 - Metapolygnathus parvus (FO), early adult specimen; sample NA35. Micro-Unimi no. 2048. For each specimen, all the three views are provided: a) upper view; b) lateral view; c) lower view. Scale bar corresponds to 200 µm, all the specimens are at the same scale. M. Mazza et alii - Metapolygnathus parvus as a marker for the base of the Norian Pl.91 2 92 Bollettino della Società Paleontologica Italiana, 57 (2), 2018

Range - From the base of the Metapolygnathus M. praecommunisti sensu Mazza et al. (2012a, b). In fact, praecommunisti Zone to the first half of theM. communisti as stated before, some specimens of M. ex gr. communisti Zone, lower-upper Tuvalian (sensu Rigo et al., 2018; of Orchard (2014), ancestor of M. dylani, in particular Fig. 5). morphotypes 1-3 (Fig. 3), can be considered as true M. praecommunisti (Rigo et al., 2018). Orchard (2014, p. 68) identified M. dylani also at Pizzo Mondello, stating that: Metapolygnathus dylani Orchard, 2014 “A single specimen illustrated by Mazza et al. (2012b) (Pl. 1, figs 4-6; Pl. 2, figs 1-5) has similar platform dimensions to one example of this species (M. dylani, Authors’ note) (fig. 47.10-12 = Pl. 1, 2011 Metapolygnathus praecommunisti sp. nov. Mazza, Rigo fig. 5, this paper) although the former has a pit in a more & Nicora, Fig. 2H (only). anterior position. The specimens, regarded as “advanced * 2014 Metapolygnathus dylani sp. nov. Orchard, p. 68, Fig. forms” of “M.” praecommunisti by Mazza et al. (2011), 47:1-21. have a shorter platform than is typical of that species and are included here”. Metapolygnathus dylani has a Material - See Tab. 1. certain intraspecific variability asM. praecommunisti, as noted also by Orchard (2014, p. 68): “These elements (M. Locus typicus and Stratum typicum - Black Bear Ridge dylani, authors’ note) exhibit variation in pit position and (northern British Columbia, Canada); bed 14b, within the in their platform lateral profile: one specimen (fig. 47.19- Pardonet Formation. 21) has a down-sloped anterior lateral margin, similar to morphotype 1 of Metapolygnathus ex gr. communisti (M. Description - The description of this species coincides praecommunisti sensu Mazza et al., 2011; Authors’ note)”. with the original one given by Orchard (2014). The The morphological affinities betweenM. praecommunisti conodont has a relatively short platform covering about and M. dylani confirm the strict relationship between the half of the entire element. The posterior margin is straight two species, and their variability testifies their nature as to oblique and has variably rounded posterior corners. morphoclines, leaving no doubt about the presence of M. The anterior margins generally lack ornamentation, rarely dylani in both Tethys and North America. In both PM and bearing incipient nodes. The blade is about half of the BBR sections, M. dylani occurs several meters below the element length, and the carina is composed of three-five first appearance of M. parvus (Figs 3-4), and the direct nodes that terminate in a large node. The pit is centrally evolution of M. parvus from M. dylani is clear. located with respect to the platform, while the keel shows a posterior prolongation, with a squared-off termination. Range - From the middle Neogondolella cavitata Zone to the lower part of the Metapolygnathus parvus Discussion - Orchard (2014) considered Zone, upper Tuvalian-lower Lacian (sensu Rigo et al., Metapolygnathus dylani as the precursor of M. parvus: 2018; Fig. 5). “Metapolygnathus dylani sp. nov. is interpreted to have evolved from M. ex gr. communisti through reduction of the anterior platform and the relative lengthening of Metapolygnathus parvus Kozur, 1972 the free blade. A continuation of this trend is thought (Pl. 2, fig. 7; Pl. 4, figs 1-8) to have led to M. parvus, which has a substantially reduced platform that is less than half of the total element * 1972 Metapolygnathus parvus n. sp. Kozur, p. 8, Pl. 6, figs 2-5. length and an anterior pit” (Orchard, 2014, p. 10). This 1980 Metapolygnathus communisti Hayashi - Krystyn, Pl. 12, figs 10-12. phylogenetic relationship is illustrated also in his fig. 13 2007 Metapolygnathus communisti parvus Kozur - Noyan & (as reported here in Fig. 3). Thus, M. dylani developed Kozur, p. 171, Fig. 7.1. from a long platform precursor belonging to the M. ex gr. 2007 Metapolygnathus echinatus Kozur - Orchard, Pl. 2, figs communisti (sensu Orchard, 2014) by platform shortening 19-21. and forwarded shifting of the pit (or has the anterior 2012b Metapolygnathus parvus Kozur - Mazza, Rigo & Gullo, platform margin shifted backward), or alternatively via p. 117, Pl. 8, figs 9-10.

EXPLANATION OF PLATE 3 Metapolygnathus communisti Hayashi, 1968 along its range in the M. parvus Zone, from the Pizzo Mondello section (Sicily, Italy). Figs 1-6 - Metapolygnathus communisti. 1 - First Occurrence (FO); sample FNP117. Micro-Unimi no. 2027. 2 - Primitive specimen; sample AM24. Micro-Unimi no. 2035. 3 - Adult specimen; sample FNP125. Micro-Unimi no. 2036. 4 - Adult specimen; sample FNP125. Micro-Unimi no. 2037. 5 - Adult advanced specimen; sample PM29 (from Mazza et al., 2011). Micro-Unimi no. 2024. 6 - Adult advanced specimen; sample PM29. Micro-Unimi no. 2021. For each specimen, all the three views are provided: a) upper view; b) lateral view; c) lower view. Scale bar corresponds to 200 µm, all the specimens are at the same scale. M. Mazza et alii - Metapolygnathus parvus as a marker for the base of the Norian Pl.93 3 94 Bollettino della Società Paleontologica Italiana, 57 (2), 2018

2014 Metapolygnathus ex gr. parvus alpha morphotype M. multinodosus Noyan & Kozur, 2007, M. linguiformis, Orchard, p. 69, Fig. 48: 1-25. and M. angustus Kozur, 1972. Metapolygnathus parvus 2015 Metapolygnathus communisti morph. C Mazza & was thus defined as a subspecies of M. communisti and Martínez-Pérez, Pl. 6, figs 16-26. re-illustrated (fig. 7.1) and re-described (p. 171) as a M. communisti with a shorter platform, more forward Material - See Tab. 1. shifted pit and no nodes on the platform margins (Noyan & Kozur, 2007). Locus typicus and Stratum typicum - Silická Brezová M. parvus was considered in Noyan & Kozur (Slovakian Karst), Czech Republic; Tuvalian (Klamathites (2007) as a probable descendant of M. communisti. This macrolobatus Zone). No section or sample information phylogenetic relationship was described also in Mazza given. et al. (2011, 2012a), where M. parvus was placed as the terminal taxon of the phylogenetic lineage Paragondolella Description - Small and morphologically simple noah - Metapolygnathus praecommunisti - M. communisti conodont, characterised by a very reduced (less than half - M. parvus (Mazza et al., 2011, fig. 4). element) and ovoid or sub-rectangular platform covering Recently, Orchard (2014) considered instead M. less than half of the element length, a long free blade and parvus the descendant of the newly established species the absence of nodes or denticles on the platform margins, Metapolygnathus dylani Orchard, 2014: “Metapolygnathus which are covered only by a fine microreticulation. dylani sp. nov. is interpreted to have evolved from M. ex gr. The cusp is central and undistinguished from the other communisti through reduction of the anterior platform and posterior carinal nodes. The position of the pit is frontal, the relative lengthening of the free blade. A continuation of strongly shifted towards the platform anterior margins, this trend is thought to have led to M. parvus, which has a and surrounded by a posteriorly prolonged loop with a substantially reduced platform that is less than half of the pointed or bifurcated termination. The element is mostly total element length and an anterior pit” (Orchard, 2014, straight in profile, with a high blade gradually descending p. 10). This phylogenetic relationship is illustrated also in towards the cusp. Fig. 13 of Orchard (2014) (as in Fig. 3 of this paper) and we agree with this new interpretation, reported in Fig. 4. Discussion - The conodont Metapolygnathus parvus Metapolygnathus parvus can be recognised in both was established by Kozur in 1972 from the section of North America and Tethys, as stated also by Orchard Silická Brezová (Slovakia), but the illustrated holotype (2014, p. 68-71), who identified also three morphotypes belonged to a juvenile specimen (as noted by Krystyn, with three different stratigraphic distributions, named 1980) and not to an adult individual of M. parvus. After alpha, beta and gamma (Fig. 3). Comparisons between the more than 20 years, the critics about M. parvus were Tethyan type and the North American population easily considered by Noyan & Kozur (2007), admitting that the prove that the Tethyan representative of M. parvus (Pl. 2, holotype was established from a rich fauna consisting fig. 7; Pl. 4, figs 1-8) corresponds to M. parvus alpha of exclusively of juvenile forms of this species, but stating Orchard (2014, fig. 48: 1-25) (Rigo et al., 2018), which that adult faunas were also abundant (Noyan & Kozur, is the first morphotype occurring in stratigraphic order at 2007, p. 171). Noyan & Kozur (2007) presented a detailed BBR (Fig. 3). In both sections, the FO of M. parvus occurs analysis of the Metapolygnathus communisti group, based above its precursor M. dylani (Rigo et al., 2018) (Figs 3-4). on new material from the Stefanion section (Argolis, Metapolygnathus parvus morphotype beta corresponds Greece), a pelagic succession belonging to the northern instead to Metapolygnathus echinatus Hayashi, 1968 shelf of the Pindos-Huğlu Ocean, in northern Tethys. The (Pl. 5) (i.e., it is a synonymous of M. echinatus). This is authors described in fact four species and two subspecies confirmed also by Orchard (2014, fig. 48.35-37 and 41-43), belonging to the communisti group: M. communisti who names M. parvus beta based on the same elements communisti Noyan & Kozur, 2007, M. communisti parvus, that he used to classify as M. echinatus in Orchard (2007)

EXPLANATION OF PLATE 4 Specimens representing the evolution of Metapolygnathus parvus Kozur, 1972 along its range at Pizzo Mondello (Sicily, Italy). Figs 1-8 - Metapolygnathus parvus. 1-2 - Adult specimens; sample FNP125. Micro-Unimi no. 2028 and Micro-Unimi no. 2052 respectively. 3 - Adult specimen; sample NA38 (from Mazza et al., 2012b). Micro-Unimi no. 2029. 4 - Early adult specimen; size is starting to reduce (from Mazza & Martinez-Perez, 2015); sample NA39. Micro-Unimi no. 2006. 5-6 - Adult specimens of reduced size; sample FNP135a. Micro-Unimi no. 2038 and Micro-Unimi no. 2039 respectively. 7 - Adult specimen of reduced size; sample FNP138.1. Micro-Unimi no. 2040. 8 - Last Occurrence (LO); sample PM31. Micro-Unimi no. 2042. Fig. 9 - M. parvus morphotype gamma (sensu Orchard, 2014); sample FNP138.1. Micro-Unimi no. 2041. For each specimen, all the three views are provided: a) upper view; b) lateral view; c) lower view. Scale bar corresponds to 200 µm, all the specimens are at the same scale. M. Mazza et alii - Metapolygnathus parvus as a marker for the base of the Norian Pl.95 4 96 Bollettino della Società Paleontologica Italiana, 57 (2), 2018

(pl. 2, figs 10-12, 22-24). Metapolygnathus parvus margins bear from one to three tiny nodes. The cusp is morphotype gamma is instead a species characterised by undistinguished in size, it is separated by the rest of the a blade only and a weak brim surrounding the cusp, with blade and it is followed by another accessorial node in no true platform (Pl. 4, fig. 9). This element, such as M. the middle of the posterior platform. The pit is forwardly parvus and M. echinatus, also occurs at PM in the same shifted in the anterior half of the platform. The basal stratigraphic order as at BBR (Figs 3-5), and given its lack cavity is narrow. The keel is prolonged behind the pit of platform, its small size and its first occurrence above and its termination may be squared or pointed. Laterally, the other two species, morphotype gamma seemingly the element is straight, with a high blade composed by represents the terminal taxon of the M. parvus lineage, few and poorly fused denticles (8-10). The parapets are which becomes extinct with this form. However, we high, especially at the geniculation point, where they are have to report that this form should be assigned to a new upturned in a sort of cusp, generating an abrupt step” species and probably even to a new genus, because its (Mazza et al., 2012b, p. 114). features do not match those of M. parvus nor those of genus Metaploygnathus, given its lack of platform, which Discussion - Metapolygnathus echinatus is is a very diagnostic character in conodont classification. characterised by a rectangular platform bearing one or two Nevertheless, to avoid further systematic issues in the weak nodes on the geniculation point. Metapolygnathus comparison between PM and BBR conodont faunas, we parvus morphotype beta (Orchard, 2014) thus corresponds still refer to this form as M. parvus gamma. to M. echinatus Hayashi, 1968 (Pl. 5), as confirmed also by Orchard (2014, figs 48: 35-37 and 41-43), who names Range - Metapolygnathus parvus Zone, lower Lacian M. parvus beta based on the same elements that he used (Lower Norian) (sensu Rigo et al., 2018; Fig. 5). to classify M. echinatus in Orchard (2007, pl. 2, figs 10- 12, 22-24).

Metapolygnathus echinatus (Hayashi, 1968) Range - Metapolygnathus parvus Zone, lower Lacian (Pl. 5, figs 1-6) (Lower Norian) (sensu Rigo et al., 2018; Fig. 5).

* 1968 Gladigondolella abneptis var. echinatus var. nov. Hayashi, p. 68, Pl. 2, fig.1. FIRST OCCURRENCE (FO) OF METAPOLYGNATHUS 2007 Metapolygnathus echinatus Hayashi - Nicora et al., Pl. PARVUS: POTENTIAL PRIMARY EVENT 4, fig. 4. FOR THE CARNIAN/NORIAN BOUNDARY 2007 Metapolygnathus echinatus Hayashi - Orchard, Pl. 2, figs 7-12, 22-24 (only). Since Metapolygnathus parvus is the descendant of M. 2010 Metapolygnathus echinatus Hayashi - Mazza et al., Pl. II, fig. 12. dylani, lying in the phylogenetic lineage Paragondolella 2012b “Metapolygnathus echinatus” sensu Orchard - Mazza, noah - M. praecommunisti - M. dylani - M. parvus (Figs Rigo & Gullo, p. 114, Pl. 8, figs 7-8. 3-4), it is possible to easily recognise the first phylogenetic 2014 Metapolygnathus ex gr. parvus beta morphotype Orchard, appearance (i.e., FAD) of M. parvus (Remane, 2003) p. 69, Fig. 48: 29-48 (only). documenting the transitional forms of the morphocline (Figs 3-4). This phylogenetic lineage, with the recent Material - See Tab. 1. recognition of M. dylani at Pizzo Mondello, is documented in the Tethys, allowing to identify the FO of M. parvus Locus typicus and Stratum typicum - Near Kuzu- at sample NA35. Furthermore, M. parvus is reported Machi, Tochigi Prefecture, central Japan; at the base of to occur also in other Tethyan successions, such as at the Adoyama Formation. the Bölücektasi Tepe and Erenkolu Mezarlik sections (Turkey), the Silická Brezová section (Slovakia) (Mazza Description - “The platform is sub-rectangular in & Krystyn, 2015), the Csővár borehole (Hungary) (Mazza shape, it has no anterior trough margin and is very reduced & Krystyn, 2015), the Gianni Grieco section, Lagonegro (less than half of the entire element). The platform Basin (Southern Apennines, Italy) (Rigo et al., 2012),

EXPLANATION OF PLATE 5 Metapolygnathus echinatus Hayashi, 1968 along its range in the M. parvus Zone at Pizzo Mondello (Sicily, Italy). This species corresponds to Metapolygnathus ex gr. parvus morphotype beta of Orchard (2014), who resembled M. echinatus into the M. ex gr. parvus population. Figs 1-6 - Metapolygnathus echinatus. 1 - First Occurrence (FO), early adult specimen; sample NA36. Micro-Unimi no. 2049. 2 - Late juvenile specimen from the lowest part of the M. echinatus range; sample PM27. Micro-Unimi no. 2023. 3 - Early adult specimen; sample PM28. Micro-Unimi no. 2022. 4-5 - Adult specimens; sample NA39 (from Mazza et al., 2012b). Micro-Unimi no. 2051 and Micro-Unimi no. 2030 respectively. 6 - Last Occurrence (LO), adult specimen; sample PM31. Micro-Unimi no. 2043. For each specimen, except for Micro-Unimi no. 2023, all the three views are provided: a) upper view; b) lateral view; c) lower view. Scale bar corresponds to 200 µm, all the specimens are at the same scale. M. Mazza et alii - Metapolygnathus parvus as a marker for the base of the Norian Pl.97 5 98 Bollettino della Società Paleontologica Italiana, 57 (2), 2018

Fig. 5 (color online) - Schematic comparison between the two stratigraphic sections suggested as GSSP of the Norian Stage. Stratigraphic logs, bivalves and ammonoids are from Mazza et al. (2012b), Levera (2012) and Balini et al. (2012) for Pizzo Mondello. Conodont sample position and distribution of selected conodonts are modified after Mazza & Martínez-Pérez (2015). Data for Black Bear Ridge are from Orchard (2014). Biozonation for Pizzo Mondello is after Rigo et al. (2018). Conodont sample position was calibrated in the field during seven field trips (from 2005 to 2010) by the Authors on the original 13 spots of the palaeomagnetism samples of Muttoni et al. (2001, 2004). These data are the same reported in Levera (2012), Mazza et al. (2012b) and Muttoni et al. (2014). Chemostratigraphy of δ Ccarb is from Mazza et al. (2010) and Onoue et al. (2015) for Pizzo Mondello and Black Bear Ridge respectively. Turnovers T1, T2, and T3 are placed based on the original definition in Mazza et al. (2010). M. Mazza et alii - Metapolygnathus parvus as a marker for the base of the Norian 99 and the Argolis section (Greece) (Noyan & Kozur, 1. It is easily recognisable. 2007). Thus, the occurrence of the representatives of 2. It is possible to identify the FAD of M. parvus inside the entire phylogenetic lineage that leads to M. parvus the lineage M. praecommunisti - M. dylani - M. parvus in from M. communisti (Figs 3-4) is recognisable in the both candidate GSSP sections (Pizzo Mondello and Black same stratigraphic order (homotaxy) in both the North Bear Ridge). American and Tethyan provinces. Furthermore, the finding 3. M. parvus is documented to occur homotaxially of M. parvus in all the provinces of the Tethys (southern, both at Pizzo Mondello (Tethys) and Black Bear Ridge western and northern Tethys) in the same stratigraphic (Northern America). position, makes the M. parvus biovent an ideal marker 4. It is coincident with the disappearance of typical for the Norian GSSP. Carnian conodonts in both candidate sections, and with the mass occurrence of evolutionary advanced metapolygnathids, followed by the appearance of the GLOBAL CORRELATIONS richly ornate Norian epigondolellids. The FO of M. parvus thus marks a turnover between typical Carnian and Norian In both Tethyan and North American regions species. Metapolygnathus parvus occurs above the last occurrence 4. Its range is placed between Carnian strata with the of the late Carnian ammonoid genus Anatropites ammonoid Anatropites and Norian strata with Guembelites Mojsisovics, 1893. At BBR M. parvus occurs below in North America and Dimorphites in the Tethys. the first occurrence of the first Norian ammonoid genus 5. It occurs below the first occurrence of Halobia Guembelites Mojsisovics, 1896 (Balini et al., 2010a; austriaca in both provinces. 13 Orchard, 2014), while at PM below the first Norian 6. It occurs near the base of a positive δ Ccarb trend in ammonoid genus Dimorphites (Fig. 5) (Balini et al., 2012, both candidate sections. 2015). Recently, the occurrence of the bivalve Halobia 7. It occurs in an interval without lithofacies changes. austriaca Mojsisovics, 1874 has been proposed as another 8. It occurs in the uppermost part (ca. 3.20 m below possible primary marker event to define the base of the the top) of the magnetozone PM4n at Pizzo Mondello Norian Stage (Balini, 2010a; McRoberts & Krystyn, section. 2011; Balini et al., 2012; Levera, 2012). At both the proposed sections for the base of the Norian the bivalve H. austriaca occurs above the FO of M. parvus (Balini et al., ACKNOWLEDGEMENTS 2012; Levera, 2012; Orchard, 2014). However, Orchard (2014 and references therein) reported the occurrence of Funding for this research was provided by PRAT CPDA152211/15 to M. Rigo by the University of Padova and H. austriaca from the Carnian ammonoid macrolobatus by MIUR PRIN (2008BEF5Z7_001; PI M. Balini, University of Zone. Milan) to M. Mazza. The Authors warmly thank M. Hounslow, There are also two physical events that make C. Henderson and M. Balini for the improvement of the paper by Metapolygnathus parvus easily correlatable among providing reviews as well as edits. The Authors are grateful to A. different sections. At Pizzo Mondello, in fact, the FO of Ferretti for her efforts and attention in managing this submission. M. parvus is 3.20 m below the top of the magnetozone M. Mazza thanks L. Krystyn for giving access to his conodont 13 collections from the Turkish sections. PM4n, and ca.7.30 m from the base of a positive δ Ccarb shift recognised in both Pizzo Mondello and Black Bear Ridge sections (Muttoni et al., 2004, 2014; Mazza et al., 13 REFERENCES 2010; Onoue et al., 2015) (Fig. 5). This positive δ Ccarb shift is not related to any significant lithological changes Balini M., Bertinelli A., Di Stefano P., Guaiumi C., Levera M., in the two candidate sections, and it is also documented in Mazza M., Muttoni G., Nicora A., Preto N. & Rigo M. (2010a). other Tethyan successions, that are at Aghia Marina and The Late Carnian-Rhaetian succession at Pizzo Mondello Guri Zi, in Greece and Albania respectively (Muttoni et (Sicani Mountains). Albertiana, 39: 36-58. al., 2014; Onoue et al., 2015), indicating a probable global Balini M., Jenks J.F., Martin R., McRoberts C.A., Orchard M.J. & trend recorded by the seawater chemistry. This positive Silberling N.J. (2015). The Carnian/Norian boundary succession trend is also coincident with the disappearance of the at Berlin-Ichthyosaur State Park (Upper Triassic, central typical (both ornate and inornate) Carnian conodonts, Nevada, USA). Paläontologische Zeitschrift, 89: 399-433. Balini M., Krystyn L., Levera M. & Tripodo A. (2012). Late and the mass occurrence of metapolygnathids, originally Carnian-early Norian ammonoids from the GSSP candidate named Turnover T2 at Pizzo Mondello (Mazza et al., section Pizzo Mondello (Sicani Mountains, Sicily). Rivista 2010) and recognised also at Black Bear Ridge. This Italiana di Paleontologia e Stratigrafia, 118: 47-84. correspondence is probably related to a global spreading Balini M., Lucas S.J., Jenks J.F. & Spielmann J.A. (2010b). Triassic of oxygen depleted conditions (Onoue et al., 2015). ammonoid biostratigraphy: an overview. In Lucas S.G. (ed.), The Triassic Timescale. Geological Society, London, Special Publications, 334: 221-262. CONCLUSIONS Bateson W. (1886). The ancestry of the Chordata. The Quarterly journal of microscopical science, 26: 535-571. Bertinelli A., Casacci M., Concheri G., Gattolin G., Godfrey L., We propose to consider a conodont bioevent and, in Katz M.E., Maron M., Mazza M., Mietto P., Muttoni G., Rigo particular, the FO of Metapolygnathus parvus Kozur, M., Sprovieri M., Stellin F. & Zaffani M. (2016).The Norian/ 1972, as a valid and potential primary marker event to Rhaetian Boundary interval at Pignola-Abriola section (southern define the base of the Norian on the basis of the following Apennines, Italy) as a GSSP candidate for the Rhaetian stage: considerations: an update. Albertiana, 43: 5-18. 100 Bollettino della Società Paleontologica Italiana, 57 (2), 2018

Budurov K. (1972). Ancyrogondolella triangularis gen. et sp. n. Palaeogeography, Palaeoclimatology, Palaeoecology, 290: (Conodonta). Mitteilungen der Gesellschaft der Geologie- und 120-137. Bergbaustudenten in Wien, 21: 853-860. Mazza M. & Krystyn L. (2015). The revised Upper Triassic Carter E.S. & Orchard M.J. (2013). Intercalibration of conodont and conodont record of the Tethys: a new step towards a better radiolarian faunas from the Carnian-Norian boundary interval in definition of the conodont bioevents around the base of the Haida Gwaii, British Columbia, Canada. New Mexico Museum Norian stage. Berichte des Institutes für Erdwissenschaften of Natural History and Science, Bulletin, 61: 67-92. Karl-Franzens-Universität Graz, 21: 243. Chen Y., Krystyn L., Orchard M.J., Lai X.-L. & Richoz S. (2015). Mazza M. & Martínez-Pérez C. (2015). Unravelling conodont A review of the evolution, biostratigraphy, provincialism and (Conodonta) ontogenetic processes in the Late Triassic through diversity of Middle and early Late Triassic conodonts. Papers growth series reconstructions and X-ray microtomography. in Palaeontology, 2: 235-263. Bollettino della Società Paleontologica Italiana, 54: 161-186. Dzik J. (1976). Remarks on the evolution of Ordovician conodonts. Mazza M., Rigo M. & Gullo M. (2012b). Taxonomy and Acta Palaeontologica Polonica, 21: 395-455. stratigraphic record of the Upper Triassic conodonts of the Eichenberg W. (1930). Conodonten aus dem Culm des Harzes. Pizzo Mondello section (Western Sicily, Italy), GSSP candidate Paläontologische Zeitschrift, 12: 177-182. for the base of the Norian. Rivista Italiana di Paleontologia e Giordano N., Rigo M., Ciarapica G. & Bertinelli A. (2010). New Stratigrafia, 118: 85-130. biostratigraphical constraints for the Norian ⁄Rhaetian boundary: Mazza M., Rigo M. & Nicora A. (2011). A new Metapolygnathus data from Lagonegro Basin, Southern Apennines, Italy. Lethaia, platform conodont species and its implications for Upper 43: 573-586. Carnian global correlations. Acta Palaentologica Polonica, Gradinaru E., Orchard M.J., Nicora A., Gallet Y., Besse J., Krystyn 56: 121-131. L., Sobolev E.S., Atudorei N.-V. & Ivanova D. (2007). The McRoberts C.A. (2007). The halobid bivalve succession across a Global Boundary Stratotype Section and Point (GSSP) for the potential Carnian/Norian GSSP at Black Bear Ridge, Williston base of the Anisian Stage: Desli Caira Hill, North Dobrogea, Lake, northeast British Columbia, Canada. Albertiana, 36: Romania. Albertiana, 36: 54-71. 142-145. Gradstein F.M., Ogg J.G., Schmitz M. & Ogg G. (2012). The McRoberts C.A. (2011). Late Triassic Bivalvia (Chiefly Halobiidae Geologic Time Scale 2012. 1142 pp. Elsevier, Amsterdam. and Monotidae) from the Pardonet Formation, Williston Lake Hayashi S. (1968). The Permian Conodonts in Chert of the Adoyama area, northeastern British Columbia, Canada. Journal of Formation, Ashio Mountains, Central Japan. Earth Sciences, Paleontology, 85: 613-664. 22: 63-77. McRoberts C.A. & Krystyn L. (2011). The FOD of Halobia Kiliç A.M., Plasencia P., Ishida K. & Hirsch F. (2015). The Case austriaca at the Black Bear Ridge (north-eastern British of the Carnian (Triassic) Conodont Genus Metapolygnathus Columbia) as the potential base-Norian GSSP. In Haggart Hayashi. Journal of Earth Science, 26: 219-223. J.W. & Smith P.L. (eds), Canadian Paleontology Conference, Kozur H. (1972). Die Conodontengattung Metapolygnathus Proceedings, 9: 38-39. Hayashi, 1968 und ihr stratigraphischer Wert. Geologisch- Mock R. (1979). Gondolella carpathica n. sp., eine wichtige Paläontologische Mitteilungen Innsbruck, 2: 1-37. tuvalische Conodontenart. Geologisch-Paläontologische Kozur H. (1989). Significance of events in conodont evolution for the Mitteilungen Innsbruck, 9: 171-174. Permian and Triassic stratigraphy. Courier Forschungsinstitut Moix P., Kozur H.W., Stampfli G.M. & Mostler H. (2007). New Senckenberg, 117: 385-408. paleontological, biostratigraphic and paleogeographic results Kozur H. (1990). Norigondolella n. gen., eine neue obertriassische from the Triassic of the Mersin Mélange, SE Turkey. New Conodontengattung. Paläontologische Zeitschrift, 64: 125- Mexico Museum of Natural History and Science, Bulletin, 41: 132. 282-311. Kozur H. (2003). Integrated ammonoid-, conodont and Mosher L.C. (1968). Triassic conodonts from western North radiolarian zonation of the Triassic. Hallesches Jahrbuch für America and Europe and their correlation. Journal of Geowissenschaften, 25: 49-79. Paleontology, 42: 895-946. Kozur H. & Mock R. (1974). Misikella posthernsteini n. sp., Muttoni G., Kent D.V., Olsen P.E., Di Stefano P., Lowrie die jüngste Conodontenart der tethyalen Trias. Časopis pro W., Bernasconi S.M. & Hernández F.M. (2004). Tethyan mineralogii a geologii, 19: 245-250. magnetostratigraphy from Pizzo Mondello (Sicily) and Krystyn L. (1980). Stratigraphy of the Hallstatt region. Guidebook, correlation to the Late Triassic Newark astrochronological Abstracts, Second European Conodont Symposium-ECOS II. polarity time scale. Geological Society of America Bulletin, Abhandlungen der Geologischen Bundesanstalt, 35: 69-98. 116: 1043-1058. Krystyn L. (2010). Decision report on the defining event for the Muttoni G., Kent D.V. & Orchard M.J. (2001). Paleomagnetic base of the Rhaetian stage. Albertiana, 38: 11-12. reconnaissance of early Mesozoic carbonates from Williston Levera M. (2012). The Halobiids from the Norian GSSP candidate Lake, northeastern British Columbia, Canada: evidence for section of Pizzo Mondello (Western Sicily, Italy): systematics late Mesozoic remagnetization. Canadian Journal of Earth and correlations. Rivista Italiana di Paleontologia e Stratigrafia, Sciences, 38: 1157-1168. 118: 3-45. Nicora A., Balini M., Bellanca A., Bertinelli A., Bowring S.A., Di Lindström M. (1970). A suprageneric taxonomy of the conodonts. Stefano P., Dumitrica P., Guaiumi C., Gullo M., Hungerbuehler Lethaia, 3: 427-445. A., Levera M., Mazza M., McRoberts C.A., Muttoni G., Preto Linnaeus C. (1758). Systema naturae per regna tria naturae, N. & Rigo M. (2007). The Carnian/Norian boundary interval secundum classes, ordines, genera, species, cum characteribus, at Pizzo Mondello (Sicani Mountains, Sicily) and its bearing differentiis, synonymis locis. Tomus 1. 10th edition. 824 pp. for the definition of the GSSP of the Norian Stage.Albertiana , Laurentius Salvius, Holmiae. 36: 102-129. Lucas S.G. (2016). Base of the Rhaetian and a critique of Triassic Nogami Y. (1968). Trias-Conodonten von Timor, Malaysien und conodont-based chronostratigraphy. Albertiana, 43: 24-27. Japan (Paleontological Study of Portuguese Timor, 5). Memoirs Mazza M., Cau A. & Rigo M. (2012a). Application of numerical of the Faculty of Science, Kyoto University. Series of Geology cladistic analyses to the Carnian-Norian conodonts: a new and Mineralogy, 34: 115-136. approach for phylogenetic interpretations. Journal of Systematic Noyan O. & Kozur H. (2007). Revision of the late Carnian-early Palaeontology, 10: 401-422. Norian conodonts from the Stefanion section (Argolis, Greece) Mazza M., Furin S., Spötl C. & Rigo M. (2010). Generic turnovers and their paleobiogeographic implications. Neues Jahrbuch of Carnian/Norian conodonts: climatic control or competition? für Geologie und Paleontologie Abhandlungen, 245: 159-178. M. Mazza et alii - Metapolygnathus parvus as a marker for the base of the Norian 101

Ogg J.G. (2012). Triassic. In Gradstein F.M., Ogg J.G., Schmitz Rigo M., Mazza M., Karádi V. & Nicora A. (2018). New Upper M. & Ogg G. (eds), The Geological Time Scale 2012, Elsevier: Triassic conodont biozonation on of the Tethyan Realm. In 681-730. Tanner L.H. (ed.), The Late Triassic World: Earth in a Time of Onoue T., Zonneveld J-P., Orchard M.J., Yamashita M., Yamashita Transition, Topics in Geobiology 46, Springer: 189-235. K., Sato H. & Kusaka S. (2015). Paleoenvironmental changes Rigo M., Preto N., Roghi G., Tateo F. & Mietto P. (2007). A rise across the Carnian/Norian boundary in the Black Bear in the Carbonate Compensation Depth of western Tethys Ridge section, British Columbia, Canada. Palaeogeography, in the Carnian (Late Triassic): deepwater evidence for the Palaeoclimatology, Palaeoecology, 441: 721-733. Carnian Pluvial Event. Palaeogeography, Palaeoclimatology, Orchard M.J. (1991). Upper Triassic conodont biochronology and Palaeoecology, 246: 188-205. new index species from the Canadian Cordillera. In Orchard Rigo M., Trotter J., Preto N. & Williams I. (2012). Oxygen M.J. & McCracken A.D. (eds), Ordovician to Triassic conodont isotopic evidence for Late Triassic monsoonal upwelling in the paleontology of the Canadian Cordillera. Geological Survey of northwestern Tethys. Geology, 40: 515-518. Canada, 417: 299-335. Sweet W.C. (1970). Uppermost Permian and Lower Triassic Orchard M.J. (2007). A proposed Carnian-Norian Boundary GSSP conodonts of the Salt Range and Trans-Indus, West Pakistan. at Black Bear Ridge, northeast British Columbia, and a new In Kummel B. & Teichert C. (eds), Stratigraphic boundary conodont framework for the boundary interval. Albertiana, problems, Permian and Triassic of West Pakistan. University 36: 130-141. Press of Kansas: 207-275. Orchard M.J. (2010). Triassic conodonts and their role in stage Trotter A.J., Williams S.I., Nicora A., Mazza M. & Rigo M. (2015). boundary definitions. In Lucas S.G. (ed.), The Triassic Long-term cycles of Triassic climate change: a new δ18O record Timescale. Geological Society, Special Publication, 334: from conodont apatite. Earth and Planetary Science Letters, 139-161. 415: 165-174. Orchard M.J. (2013). Five new genera of conodonts from the Williford K.H., Orchard M.J., Zonneveld J-P., McRoberts C. & Carnian-Norian Boundary beds, northeast British Columbia, Beatty T.W. (2007). A record of stable organic carbon isotopes Canada. In Tanner L.H., Spielman J.A. & Lucas S.G. (eds), from the Carnian-Norian boundary section at Black Bear The Triassic System. New Mexico Museum of Natural History Ridge, Williston Lake, British Columbia, Canada. Albertiana, and Science, Bulletin, 61: 445-457. 63: 160-162. Orchard M.J. (2014). Conodonts from the Carnian-Norian Boundary Yin H., Zhang K., Tong J., Yang Z. & Wu S. (2001). The Global (Upper Triassic) of Black Bear Ridge, Northeastern British Stratotype Section and Point (GSSP) of the Permian-Triassic Columbia, Canada. New Mexico Museum of Natural History boundary. Episodes, 24: 102-114. and Science Bullettin, 64. 139 pp. New Mexico Museum of Zonneveld J-P., Beatty T.W., Williford K.H., Orchard M.J. & Natural History and Science, Albuquerque. McRoberts C.A. (2010). Stratigraphy and sedimentology of the Orchard M.J. & Tozer E.T. (1997). Triassic conodont biochronology, lower Black Bear Ridge section, British Columbia: candidate its intercalibration with the ammonoid standard, and a for the base-Norian GSSP. Stratigraphy, 7: 61-82. biostratigraphic summary for the Western Canada Sedimentary Basin. Bulletin of Canadian Petroleum Geology, 45: 675-692. Orchard M.J., Zonneveld J.P., Johns M.J., McRoberts C.A., Sandy M.R., Tozer E.T. & Carrelli G.G. (2001). Fossil succession and sequence stratigraphy of the Upper Triassic of Black Bear Ridge, northeast British Columbia, a GSSP prospect for the Carnian-Norian boundary. Albertiana, 25: 10-22. Remane J. (2003). Chronostratigraphic correlations: their importance for the definition of geochronologic units. Palaeogeography, Palaeoclimatology, Palaeoecology, 196: 7-18. Rigo M., Bertinelli A., Concheri G., Gattolin G., Godfrey L., Katz M., Maron M., Mietto P., Muttoni G., Sprovieri M., Stellin F. & Zaffani M. (2016). The Pignola-Abriola section (southern Apennines, Italy): a new GSSP candidate for the base of the Rhaetian Stage. Lethaia, 49: 287-306. Manuscript received 27 June 2017 Rigo M. & Joachimski M.M. (2010). Palaeoecology of Late Triassic Revised manuscript accepted 18 July 2018 conodonts: constraints from oxygen isotopes in biogenic apatite. Online publication 13 August 2018 Acta Palaeontologica Polonica, 55: 471-478. Editor Annalisa Ferretti