Report on the 7th International Meeting of the IUGS Lower Cretaceous Ammonite Working Group, the Kilian Group (Warsaw, Poland, 21st August 2022): State of the art on the current Standard Ammonite Zonation of the Western Tethyan Mediterranean Province

Report on the 7th International Meeting of the IUGS Lower Cretaceous Ammonite Working Group, the Kilian Group (Warsaw, Poland, 21st August 2022): State of the art on the current Standard Ammonite Zonation of the Western Tethyan Mediterranean Province Ottilia Szives a , * , 1 , Josep A. Moreno-Bedmar b , 1 , Beatriz Aguirre-Urreta c , 2 , Miguel Company d , 2 , Camille Frau e , 2 , Mikel L opez-Horgue f , 2 , Antoine Pictet g , 2 , Izabela Ploch h , 2 , Christian Salazar i , 2 , Ricardo Barrag an b , 3 , Jean-Louis Latil j , 3 , Jens Lehmann k , 3 , Emmanuel Robert l , 3 ,St  ephane Reboulet l , 3 a Department of Palaeontology and Geology, Hungarian Natural History Museum, 1431 Budapest, Pf. 137, Hungary b Instituto de Geología, Universidad Nacional Autonoma de M exico, Ciudad Universitaria, Coyoac an, 04510 Ciudad de M exico, Mexico c Instituto de Estudios Andinos “Don Pablo Groeber”(UBA-CONICET), Departamento de Ciencias Geol ogicas, Universidad de Buenos Aires, C1428EGA, Buenos Aires, Argentina d Departamento de Estratigrafía y Paleontología, Facultad de Ciencias, Universidad de Granada, Campus de Fuentenueva s/n, 18002 Granada, Spain e Groupement d'Int er^ et Pal eontologique, Science et Exposition, 60 bd Georges Richard, 83000 Toulon, France f Geologia Saila, Euskal Herriko Unibertsitatea/University of the Basque Country UPV/EHU, Sarriena z/g, 48940 Leioa (Biscay), Basque Country, Spain g Mus eum cantonal des sciences naturelles, D epartement de g eologie, Quartier UNIL-Chamberonne, B^ atiment Anthropole, 1015 Lausanne, Switzerland h Zakład Geologii Regionalnej, Pa nstwowy Instytut Geologiczny ePa nstwowy Instytut Badawczy, ul. Rakowiecka 4, 00-975 Warszawa, Poland i Escuela de Geología, Facultad de Ciencias, Universidad Mayor, Manuel Montt 367, 750094 Providencia, Chile j Le Maupas, 05300 Lazer, France k Fachbereich Geowissenschaften, Universit€ at Bremen, Klagenfurter Strasse 4, 28359 Bremen, Germany l Universit e Lyon, UCBL, ENSL, UJM, CNRS, LGL-TPE, F-69622 Villeurbanne, France article info Article history: Received 1 June 2023 Received in revised form 28 August 2023 Accepted in revised form 20 September 2023 Available online 29 September 2023 Keywords: Lower Cretaceous Ammonites Mediterranean standard zonation Berriasian Aptian Albian abstract The 7th meeting of the IUGS Lower Cretaceous Ammonite Working Group the ‘Kilian Group (KG)’was held in Warsaw, Poland, on 21st August 2022. Need of major changes for the Jurassic/Cretaceous transition, namely to the uppermost Tithonian and lower Berriasian, and for the upper Aptian and Albian schemes is a long-known issue, which are finally conceptualized and hereby introduced into the Standard Mediterranean Ammonite Zonation (SMAZ, Western Tethys). Besides, refinements were added to the Valanginian and Hauterivian stages, discussion on some zonal indices and units are also provided. The KG highlights again the exclusive use of interval zones and subzones. Most important changes of the uppermost TithonianeBerriasian stages are the followings: i) use of two folded Berriasian is agreed, to be in better accordance with ammonite turnovers and microfossil framework; ii) uppermost Tithonian Lopeziceras chaperi, top-uppermost Tithonian to lowermost Berriasian Praedalmasiceras progenitor and lower Berriasian Pseudosubplanites grandis Zones are accepted to be introduced into the SMAZ, these three zones to cover the former ‘Berriasella’jacobi Zone auctorum which is formally abandoned; iii) lower Berriasian Delphinella delphinensis Subzone is accepted as a reliable marker level of the upper Praedalmasiceras progenitor Zone; iv) Strambergella jacobi Zone is established and discussed. Tirnovella occitanica Zone and Tirnovella subalpina Subzone are discussed. Modifications on the Valanginian zonation are the followings: i) Neocomites premolicus Subzone is re-defined, ii) Neolissoceras (Vergoliceras) salinarium Subzone is introduced; iii) Neocomites neocomiensiformis Zone is divided into two subzones, the lower N. neocomiensiformis and the upper *Corresponding author. E-mail address: [email protected] (O. Szives). 1 Reporters. 2 Participants at the meeting with scientific contribution. 3 Absents at the meeting but provided written scientific contribution. As chair of the group, the report was elaborated with the contribution of S. Reboulet. Contents lists available at ScienceDirect Cretaceous Research journal homepage: www.elsevier.com/locate/CretRes https://doi.org/10.1016/j.cretres.2023.105716 0195-6671/©2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Cretaceous Research 153 (2024) 105716 Busnardoites campylotoxus Subzones. Modifications on the Hauterivian stage are the followings: i) all horizons are deleted; ii) Olcostephanus (Olcostephanus)variegatus Subzone is introduced; iii) Balearites angulicostatus Subzone is introduced; iv) all subzonal index-species of the B. balearis Zone are assigned to genus Balearites;v) Pseudothurmannia mortilleti is considered as a senior synonym of P. catulloi, therefore its nominal subzone also changed its name to mortilleti. No change in the Barremian scheme, however the base of Toxancyloceras vandenheckii Subzone and Zone is defined by the first appearance of the genus Toxancyloceras. Most important changes of the upper Aptian zonation are the followings: i) Nolaniceras nolani and 'Hypacanthoplites jacobi' zones are retained from the SMAZ; ii) re-introduction of Diadochoceras nodosocostatum Zone is given. For the AptianeAlbian transition interval, introduction of ‘Hypacanthoplites’ elegans Zone is accepted, where the Aptian/Albian boundary lies within. Most important zonal changes of the Albian stage are: i) the Leymeriella-based succession is abandoned from the SMAZ and replaced by the cosmopolitan Douvilleiceras-based succession; ii) Douvilleiceras leightonense Zone is introduced; iii) middle Albian Hoplites dentatus, Euhoplites loricatus, Euhoplites lautus Zones and Hoplites spathi Subzone are retained from the SMAZ and restricted to the Boreal ammonite scheme; iv) Lyelliceras lyelli Subzone arisen to zonal rank defining the basal middle Albian; v) Oxytropidoceras (Oxytropidoceras) roissyanum Zone is introduced; vi) upper Albian zonation based on the phyletic lineage of Mortoniceratids is kept, however generic names of the indices are modified to Pervinquieria; vii) Pervinquieria pricei Zone is divided into three subzones of Hysteroceras varicosum, H. binum and H. choffati from the oldest to youngest; viii) Pervinquieria inflata Zone is divided into two subzones of Hysteroceras bucklandi and Cantabrigites spp. The KG tributes to our recently deceased ammonitologist colleagues in the Supplement, a discussion on the future work is provided. The next Kilian Group meeting will be held in Hannover, prior to the first day of the 12th International Symposium on the Cretaceous System. ©2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). 1. Introduction The 7th meeting of the IUGS Lower Cretaceous Ammonite Working Group (the Kilian Group, KG) took place on Sunday 21st August 2022 at the Warsaw University (Poland), the day before the 11th International Symposium on the Cretaceous System (22e27 August 2022). The meeting is moderated and reported by Szives and Moreno-Bedmar (authors with 1 ). The workshop was attended by 9 members from 7 countries (authors, with 2 ). Some colleagues who could not attend, submitted contributions that were taken into account during the discussions (see “written scientific contribution”) and their names are added here (authors, with 3 ). In this present report, major changes are introduced in the standard zonation for the Jurassic/Cretaceous transition, namely to uppermost Tithonian and lower Berriasian, and also for upper Aptian and Albian schemes. Besides, some refinements were added to the lower Valanginian, Hauterivian and upper Barremian substages. The end of the meeting was devoted to the tribute to our recently deceased ammonite colleagues, and a discussion on the future work. 2. The Standard Lower Cretaceous Ammonite zonation of the Mediterranean Province The Standard Mediterranean Ammonite Zonation (SMAZ) is applied to the Mediterranean Province of the MediterraneaneCaucasian Subrealm of the Tethyan Realm sensu Westermann (2000) followed by Lehmann et al. (2015). However, ‘standard’implies an absolute principle of universality at least for this subrealm. In our opinion this term needs to be kept for three reasons: 1) to avoid confusion between local zonations that can be different even between geographically close sections; 2) to keep correlation as clear as possible to other realms and subrealms for non-ammonitologists as well, and 3) to reflect the standard scientific level of the input data as based only on peer reviewed, already published (or at least accepted) papers. References to important unpublished data are also mentioned, although not incorporated into the SMAZ until their publication. In different palaeogeographic units its accuracy is limited due to endemic faunas and the non-isochronous appearance of certain ammonite groups as pointed in Reboulet et al. (2018). The Warsaw meeting mainly dealt with the zonation of the Berriasian, Aptian and Albian as inadequate zonation of these stages was the most chronic problem of the SMAZ since decades (Hoedemaeker et al., 1990). As the stratigraphic position of the former ‘Berriasella’jacobi Zone proven to be stretched from the uppermost Tithonian to lower Berriasian (Frau et al., 2016a), in this report a discussion and proposals on the uppermost Tithonian are also included. A brief state of the art was outlined by Szives, Frau and Moreno-Bedmar and new zonal schemes including the topmost Tithonian were also presented based on biostratigraphic results published since the last meeting at Vienna (Austria; 2017). For Valanginian, Hauterivian and Barremian stages, some modifications on the zonation have been proposed by Company, Reboulet and Frau. After each talk, the KG discussed the possibility of introduction or deletion of some biostratigraphic units. Three general remarks on the standard zonation are also added as: a) even though mostly Interval Zones are in use in the current SMAZ (see Reboulet et al., 2011;Szives et al., 2023 for summary), keeping the development of the ammonite zonation in focus, it is necessary to indicate the type of zones in the definition of new (sub-)zones; b) for their definition, it would be preferable to use the term FAD (First Appearance Datum) rather than FO (First Occurrence). The FAD refers to the phyletic appearance meaning we have a good knowledge or understanding of the group and on its phyletic lineage. The FO only refers to sections where the lowest occurrence of the species recorded and restricted to a section. In broader view it means a conceptual approach (¼definition of the zone) versus a fact-based approach (its identification in a section); c) due to the confusion between „horizon”and „biohorizon”(a surface versus a short interval), the KG preferred to abandon this term (Reboulet et al., 2018). Moreover, to define the base (and the top) of a (sub-) O. Szives, J.A. Moreno-Bedmar, B. Aguirre-Urreta et al. Cretaceous Research 153 (2024) 105716 2 zone, it is not necessary to introduce the term „horizon”as this standard zonal scheme is based on ammonite turnovers and not only on the FAD of index-species. All modifications on the SMAZ are shown in figures (Figs. 1e3), where numbers displayed refer to the numbered chapters in the text. Major observations and all modifications are discussed stage by stage in ascending order. Besides refining the SMAZ, the KG also envisaged three future tasks for the next meetings: i) defining the ammonite assemblage of each biostratigraphic unit; ii) collect the available 2 or 3D images of type specimens of the zonal indices; iii) start to establish the geochronological aspects of ammonite zonal units integrated into published micropaleontologic, chemoand magnetostratigraphic data. 2.1. Jurassic/Cretaceous transition Major changes were accepted (Figs. 1, 2) in the zonation of the Jurassic/Cretaceous (J/K) transition interval which affects the zonation of the uppermost Tithonian and the Berriasian as well. In the most recent zonal scheme (Gale et al., 2020) the primary marker of base of the Berriasian stage was erroneously interpreted as: “The lowest occurrence of the small, globular calpionellid species Calpionella alpina, which marks the base of the C. alpina Subzone”…. and…“The GSSP level would coincide with the appearance of small, orbicular C. alpina calpionellids (base of the Calpionella Zone)”; also on their Fig. 27.12: “Calpionellid, FAD of Calpionella alpina”. In June 2016, the Berriasian Working Group (BWG1) voted to adopt the Crassicollaria/Calpionella turnover and base of the Alpina Subzone as the primary marker for the base of the Berriasian stage (Wimbledon, 2017). It led to misunderstanding (see the example above) that Crassicollaria/Calpionella turnover is not the FAD but the acme event of Calpionella alpina, as it was clarified later in Wimbledon et al. (2020, p. 61): “marked increase [acme] in small globular Calpionella alpina … .. This event (the ‘explosion’or ‘bloom’ …. of some authors) …”is the base of the Alpina Subzone of Calpionella Zone. This event is still the recommended primary markerof the basal Berriasian voted by the BWG1, no matter if their GSSP proposal was rejected. This primary marker event does not coincide to any ammonite event, which means the Tithonian/Berriasian (T/B) boundary in terms of ammonites lies within the ehere formally abandoned e‘Berriasella’jacobi Zone auctorum Zone (Frau et al., 2016a). A new Berriasian Working Group (BWG2) was formed in 2021 but no voting was completed for selection of a new recommendation on the primary marker (which discussion is out of the scope of this paper). Szives presented their recently published (Szives and F} ozy, 2022) results on ammonites from ammonitico rosso/biancone sections and their stratigraphy across the uppermost Tithonianelower Berriasian transition from the Hungarian Transdanubian Range. Besides giving several taxonomic clarifications, they established a new uppermost Tithonianelower Berriasian zonation. Frau pointed that it is supposedly suitable for the Vocontian Basin (VB) settings, but it has to be taken into account that its applicability may not be suitable everywhere as many key areas lack integrated stratigraphy. Further discussion between Szives and Frau clarified some points debated at the meeting and their proposals were accepted as follows. Relation of proposed and previous (Reboulet et al., 2018;Gale et al., 2020) zonations of the uppermost TithonianeBerriasian interval, showing changes numbered are visualized on Fig. 1. (1*in Figs. 1,2). Former ‘Berriasella’jacobi Zone ‘Berriasella’jacobi Zone auctorum (fide Frau et al., 2016a)is abandoned. Remarks. In previous KG reports from Hoedemaeker et al. (1990) to Reboulet et al. (2018), base of the ‘B.’jacobi Zone matched with the base of Berriasian (marked with black thick horizontal line in Fig. 1) corresponding to the J/K boundary (as indicated in the right part of Fig. 1). This means that the whole ‘B.’jacobi Zone was dated as Berriasian by the former KG reports. However, on the basis of recent investigations (Frau et al., 2016a), it is accepted now (Wimbledon et al., 2020) that the base of the now abandoned ‘B.’jacobi Zone is actually within the uppermost Tithonian (Fig. 1. left column). It is also accepted here that ‘Berriasella’jacobi should be transferred to genus Strambergella (Frau et al., 2016a) and its stratigraphic position is strongly reconsidered as to be younger. Therefore, ‘B.’jacobi cannot be a marker of the basal Berriasian. Due to these reasons, Strambergella jacobi must be transferred in a different zonal sense into the upper lower Berriasian interval. Summarizing our current knowledge on the T/B boundary interval (the former ‘Berriasella’jacobi Zone), the use of any ammonite Fig. 1. Relation of hereby accepted and previous ammonite zonation (Reboulet et al., 2018) of the Berriasian stage. Note the different stratigraphic position of the base of the stage in terms of ammonite zones, and the accepted two-folded subdivision of the stage. Bold numbers refer to the numbers in the text. Zones/zones and Subzones/subzones are not in perfect scale. O. Szives, J.A. Moreno-Bedmar, B. Aguirre-Urreta et al. Cretaceous Research 153 (2024) 105716 3 Fig. 2. Standard ammonite zonation of the latest TithonianeHauterivian for the Mediterranean Province of the Western Tethyan Realm. Bold numbers refer to the numbers in the text. Zones and Subzones are not in scale. Abbreviation: T: Tithonian. O. Szives, J.A. Moreno-Bedmar, B. Aguirre-Urreta et al. Cretaceous Research 153 (2024) 105716 4 indices foreshadows two possibilities which both are unconvenient at the moment as both are inconsistent to the present primary marker event of the basal Berriasian: i) in the case of using Lopeziceras chaperi and P. progenitor as zonal indices, present T/B boundary should be situated within the Praedalmasiceras progenitor Zone; ii) in the case of using Praedalmasiceras spiticeroides and any Delphinella of the delphinense group as zonal indices, present T/B boundary is situated within the P. spiticeroides Zone. In the latter case three more handicaps have to be considered: i) if using P. spiticeroides as a zonal marker, the index lacks in the upper part of the zone (Le Chouet, VB, Frau et al., 2016a) or not present at all (Les Combes, VB, Frau et al., 2016a); ii) P. spiticeroides is a rare faunal element; iii) Delphinella seem to be facies dependant as they are rare or not present at all in the widespread tethyan ammonitico rosso facies. Considering that the BWG2 may be voting another primary marker in the near future, we see no problem about the present T/B boundary is lying within an ammonite zone. As a most recent addition (April 2023), BWG2 voted placing the J/K boundary in the upper Tithonian and at the moment the majority of the group do not favour the acme event of C. alpina to be the primary marker. (2*in Figs. 1,2). Lopeziceras chaperi Zone of the uppermost Tithonian Definition. This interval zone is defined between the FAD of its index, L. chaperi and the FAD of Praedalmasiceras progenitor, the index of the overlying zone. Taxonomic content of the zone was summarized by Frau et al. (2016b) and Szives and F} ozy (2022). Here we propose the extension of Lopeziceras chaperi Zone to the Mediterranean Province. P. spiticeroides and E. cularense being considered as typical faunal elements of L. chaperi Zone, therefore there is no need to separate E. cularense Subzone as it was proposed previously by Szives and F} ozy (2022). Remarks. The use of „Ammonites”Chaperi as a possible index fossil goes back to Kilian (1907, p. 18), Mazenot (1939),Nikolov (1967) and Sapunov (1977), but their zonal divisions were placed into various stratigraphic levels based on different interpretations of this obscure species. Finally, the modern taxonomic revision of L. chaperi was given by Frau et al. (2016b). On the basis of his work, Szives and F} ozy (2022) proposed its use as an index of the topmost Tithonian with a formal establishment of L. chaperi Zone. In contrast, according to Frau, priority should be given to P. spiticeroides since its FAD and concomitant acme marks the evolution and predominance of Dalmasiceratinae over Himalayitinae at the base of the abandoned ‘B.’jacobi Zone discussed above. We all agree this is the main ammonoid evolutionary step observed at that time, with a widespread record through the Tethyan Realm. However, the phylogeny of Praedalmasiceras is still not revised and discussed by Frau et al. (2016b), but their data suggest that P. spiticeroides can be considered as descendant of P. progenitor. Stratigraphic importance of this point needs to be clarified and has to be discussed at the next meeting. According to Frau et al. (2016b),P. spiticeroides eboth microand macroconchs eis present in France, Tunisia, Spain, Bulgaria, Hungary and doubtfully in Morocco; while L. chaperi eboth microand macroconchs eis reported from Spain, France, Bulgaria, Hungary, and Romania. P. spiticeroides is likely present in the southern Mediterranean margin, however it is less frequent than L. chaperi. As for L. chaperi, no specimens from the southern Tethyan margin have been found yet, however Szives and F} ozy (2022, point 5.1.7) have arisen some doubts on ammonite taxonomy of some latest Tithonian genera which may widen the paleogeographic distribution of Lopeziceras towards the southern Tethyan margin. Due to our understanding, both L. chaperi and P. spiticeroides cooccur with Elenaella cularense in the top Crassicollaria intermedia calpionellid Subzone, well below the Calpionella alpina acme (Tavera et al., 1994;Frau et al., 2016b;Szives and F} ozy, 2022), and hence within the uppermost Tithonian. As a taxonomic revision of genus Lopeziceras and its allied genera, together with a proposal of L. chaperi as a zonal marker have been already published (Szives and F} ozy, 2022), its priority over P. spiticeroides is considered to be established. 2.2. Berriasian 2.2.1. Lower Berriasian (3*in Fig. 1,2). Here we propose to apply the two-folded Berriasian (Figs. 1,2) and abandon the term “middle”Berriasian as ammonite and microfossil zonations have to be fit as possible to achieve a better correlated integrated framework. It is also proposed that Tirnovella occitanica Zone including Tirnovella subalpina,Berriasella privasensis and Dalmasiceras dalmasi Subzones are incorporated into the lower Berriasian. From ammonite point of view, middle Berriasian is poor in ammonites which are not well investigated yet. Base of the upper Berriasian in ammonite terms remains unchanged and placed at the base of the Fauriella boissieri Zone (Fig.1). Proposal on the two-folded subdivision of Berriasian will be presented to the BWG2. (4*in Figs. 1,2). Praedalmasiceras progenitor Zone Definition. This interval zone was established by Szives and F} ozy (2022) and is defined between the FAD of its index, P. progenitor and the FAD of Pseudosubplanites grandis, the index of the overlying zone. Here we propose the extension of P. progenitor Interval Zone to the Mediterranean Province. Taxonomic content of the zone was summarized by Frau et al. (2016b) and Szives and F} ozy (2022). Remarks. FAD of P. progenitor is clearly above the FAD of P. spiticeroides, FAD of E. cularense and L. chaperi are also above the base of the Crassicollaria colomi calpionellid Subzone (Frau et al., 2016b), but clearly below the C. alpina acme event, the base of the Calpionella alpina Subzone (Wimbledon et al., 2020). By accepting the BWG1 decision on the primary marker (see the discussion above at 2.1 chapter), the current T/B boundary lies within the P. progenitor Zone that was erroneously interpreted previously by Szives and F} ozy (2022,fig. 7). According to Frau, it is debatable whether the use of P. progenitor as index species efirst proposed by Frau et al. (2016b) eof the basal Berriasian is reliable as its occurrence is discontinuous or spotty in many key localities. In contrast Szives pointed this may change in the future due to further clarification of some allied genera discussed in Szives and F} ozy (2022). (5*in Figs. 1,2).Delphinella delphinense Subzone Definition. This interval Subzone is established here, and covers the upper part of P. progenitor Zone, between the FAD of D. delphinense and FAD of Pseudosubplanites grandis, the index of its nominal, overlying Zone. Remarks. Frau would favour the use of FAD of Delphinella of the delphinense group as a zonal index (Frau et al., 2016a)over P. progenitor, however its FAD remains controversial as discussed below. FO of Delphinella of the delphinense group is near the base of C. alpina Subzone in the Les Combes section in the VB (Frau et al., 2016a), while FO of the D. delphinense group is within the middle Calpionella ferasini calpionellid Subzone at Le Chouet section O. Szives, J.A. Moreno-Bedmar, B. Aguirre-Urreta et al. Cretaceous Research 153 (2024) 105716 5 Fig. 3. Standard ammonite zonation of the BarremianeAlbian stages of the Mediterranean Province of the Western Tethyan Realm. Bold numbers refer to the numbers in the text. Zones and Subzones are not in scale. Abbreviation: C: Cenomanian. O. Szives, J.A. Moreno-Bedmar, B. Aguirre-Urreta et al. Cretaceous Research 153 (2024) 105716 6 (Frau et al., 2016a). Although both Szives and Frau agreed that spread of Delphinella marks a widespread event through the Western Tethyan realm, Delphinella is virtually lacking or very rare in ammonitico rosso succession of eastern Spain (Tavera, 1985) and Hungary (Szives and F} ozy, 2022), and occurs probably in younger levels in Bulgaria as detailed below. In 2013, on the KG meeting in Ankara (Reboulet et al., 2014), Ivanov and Idakieva proposed to insert Delphinella obtusenodosa Zone into the standard scheme as the basal zone of the Berriasian based on their data from Berende and Kopanitsa sections (Bulgaria). Later, after incorporating the data from ammonites, calcareous nannofossils and calpionellids, it is documented that the level with the first Delphinella (Delphinella obtusenodosa, which is of the D. delphinensis group fide Frau et al., 2016b) corresponds to the base of nannofossil NK-1 Zone and calpionellid Calpionella remaniella [C. ferasini] Subzone”(Idakieva pers. comm., 2022). Their data are just briefly published (Stoykova et al., 2018) and point that the base of Delphinella biostratigraphical unit needs to be correlated to the data of Frau from the VB before putting it into the SMAZ. Moreover, all the ammonite material determined from Bulgaria needs a taxonomic reconsideration following Bulot et al. (2014a),Frau et al. (2015, 2016a,b,c) and Szives and F} ozy (2022). As the exact stratigraphic position of Delphinella delphinense interval remains controversial, it is proposed euntil its stratigraphic position is clarified eto use this very distinctive level as a subzone. (6*in Figs. 1,2). Pseudosubplanites grandis Zone Definition. This interval zone was established by Le H egarat (1973), its emended definition as an interval zone is given here between the FAD of its index, P. grandis and the FAD of Strambergella jacobi, the index of the overlying zone. Taxonomic content of P. grandis Zone was given by Le H egarat (1973), recently summarized by Szives and F} ozy (2022). Remarks. Use of this zone is agreed by both Szives and Frau, directly overlying P. progenitor Zone and the Delphinella-bearing beds. According to Szives, the zonal name should be P. grandis based on two observations: i) Frau suspects a taxonomic priority of Pseudosubplanites lorioli (Zittel, 1868) as a senior synonym of P. grandis (Mazenot,1939) that is not yet published; ii) FAD of P. lorioli appears within the Delphinella bed (Frau et al., 2016a) so the supposed synonymy affects the stratigraphic extension of the zone that needs to be clarified. (7*in Figs. 1,2). Strambergella jacobi Zone Definition. This interval zone is established here and defined between the FAD of its index, S. jacobi and the FAD of Tirnovella occitanica, the index of the overlying Zone. Taxonomic content of this zone is given by Frau et al. (2016a,b,c). Remarks. In the light of a recent revision (Frau et al., 2016a,b), Frau suggested to distinguish a Strambergella (pro Berriasella)jacobi unit above the Pseudosubplanites-bearing beds that is widely recorded in SE France, southern Spain, Italy, Bulgaria, central Tunisia, Crimea, and doubtfully in Georgia. As the taxonomic content, the widespread paleogeographic distribution of its index and the distinctive nature of this zone is agreed between Frau and Szives, here the zonal rank of this unit is supported in spite of the following uncertainties: i) upward extension of S. jacobi unit remains to be unclarified since the strong affinities between Strambergella and basal Tirnovella, as relation between Tirnovella subalpina and T. occitanica are not yet clarified; ii) taxonomic matters between S. jacobi and T. subalpina are also not clarified as specimens of both species fide Le H egarat (1973) co-occur in SE France key sections. A new, yet unpublished hypothesis of Frau is that S. jacobi macroconchs are identical to the type of T. subalpina, but inner whorls of the type are covered by matrix which prevents confirmation of the presence of a berriasellid stage in its inner whorls, as it is the main difference between genera Strambergella and Tirnovella. According to Frau, T. occitanica is distinct to early Strambergella by the peramorphic predominance of the fasciculate stage through most, if not all of its ontogenesis. Based on field data from the sections Frau published (Frau et al., 2016a,b,c), he would favour that S. jacobi Zone reaches the top of the T. subalpina ‘Zone’of Le H egarat which needs to be re-discussed in the next meeting after publishing the data. Discussion. Reintroduction of an abandoned biozonal unit in a different meaning is not advised by the Stratigraphic Guide (https://stratigraphy.org/guide/bio), as “A fossil name once used for a zone is not available for use in a different zonal sense by a later author”. Considering this case related to the Strambergella jacobi Subzone, another paragraph had been pointed out by Frau: “Named biostratigraphic units will automatically change scope to accord with changes in the scope of taxa defining or characterizing them”. Without doubt to be a distinctive marker level, Szives and Frau agreed to use Strambergella jacobi Zone in accordance with the changes in its taxonomic and stratigraphic terms executed by Frau et al. (2016a). Reboulet disapproved this idea as its different zonal sense may cause confusion, more particularly for nonammonitologists who use the SMAZ. (8*in Figs. 1,2). Tirnovella occitanica Zone Definition. No change. Remarks. According to Frau, the use of T. occitanica Zone foreshadows several problems: i) its base has to be established since it has been introduced as an assemblage zone by Le H egarat (1973) and the assemblage taxa marking the base of T. occitanica Zone needs a modern taxonomic revision. Moreover, according to the aim of the KG, this zone has to be defined as an Interval Zone. The taxonomic meaning of the index species fide Le H egarat is no more adequate, therefore without revision his assemblage zone cannot be used here as a standard zone; ii) the lower part of the T. occitanica Zone (T. subalpina Subzone) is characterised by a drastic drop in ammonites, both in abundance and diversity (Le H egarat 1973); iii) it seems that the index species is not present at the base of the zone it defines which might not be a problem in case of an Interval Zone but still it is in the original meaning of Le H egarat (1973). This is proved at Berrias where the index occurs well above the level with T. subalpina sensu Le H egarat, iv) there is no taxonomic work undertaken on the relationships between T. occitanica and T. subalpina and their link to ‘true’upper Berriasian Tirnovella is not proved yet; v) accordingly, the use of T. occitanica Zone is far for being clear and consistent from place to place in SE France. Only Dr^ ome sections have magneticecalpionellid calibration of the T. subalpina Subzone of Le H egarat, but this proves to be floating within M17r magnetozone, with no consistent ammonite marker due to drastic drop in fossil assemblages. Some members share the idea of Frau as Tirnovella occitanica Zone should be limited to Berriasella privasensis and Dalmasiceras dalmasi Subzones. These units have not been defined precisely by Le H egarat (1973) so it requires further work and to be discussed later. (9*in Figs. 1,2). Tirnovella subalpina Subzone Definition. No change. Remarks. Following Bulot (1995), Company suggested to change the generic name of Subthurmannia occitanica and Subthurmannia O. Szives, J.A. Moreno-Bedmar, B. Aguirre-Urreta et al. Cretaceous Research 153 (2024) 105716 7 subalpina into Tirnovella occitanica and Tirnovella subalpina, respectively. Indeed, since Le H egarat (1973), these two species are currently attributed by most of authors to the genus Tirnovella (for instance, see synonymies in Klein 2005). Moreover, from Hoedemaeker et al. (1990) to Hoedemaeker et al. (2000), species occitanica and subalpina were included in the genus Tirnovella. However, in the report of the Lyon meeting (Hoedemaeker et al., 2003), both species suddenly appear with the generic name of Subthurmannia, without any explanation in the text; this nomenclature corresponds to Hoedemaeker's take (see synonymies in Klein, 2005). The genus Subthurmannia was created by Spath (1939) to refer to several species defined by himself in Pakistan. The affinities of this group with the Mediterranean species are difficult to elucidate. Frau also emphasized that one should remember that most of the T. subalpina Subzone is devoid of diagnostic fauna in the VB which marks a deep change with the overlying late Berriasian assemblage. Here the inclusion of T. subalpina Subzone at Tirnovella occitanica Zone is maintained and both to be incorporated into the lower Berriasian. 2.2.2. Upper Berriasian No change in the upper Berriasian ammonite zonal or subzonal scales as base of the upper Berriasian is kept at the base of the F. boissieri Zone. 2.3. Valanginian Company presented his joint work with Reboulet and made some proposals and suggestions that were accepted as follows. (10*in Fig. 2). Neocomites premolicus Subzone Definition. The Subzone was currently considered as a total range subzone (Reboulet et al., 2018;Kenjo et al., 2021). Due to the introductionoftheN.(V.)salinariumSubzone,theN.premolicusSubzoneis re-defined here as an interval subzone defined between the FAD of theindexspecieswhichhasbeenwellrecognizedinsouth-eastSpain (CompanyandTavera2015),south-eastFrance(Kenjoetal.,2021)and Morocco(Ettachfini2004;Rebouletet al.,2022)andthe FADof N.(V.) salinarium, the index of the overlying subzone. (11*in Fig. 2). Neolissoceras (Vergoliceras) salinarium Subzone Definition. This subzone is introduced here, for the upper part of ‘Thurmanniceras’pertransiens Zone and defined by the FAD of its index species and the FAD of Neocomites neocomiensiformis, the index of the overlying zone. Remarks. Even though the N. (V.) salinarium Subzone was already integrated in the zonal scheme of south-east Spain (Company and Tavera, 2013a,b,2015) and south-east France (Kenjo 2014), Reboulet's proposal to introduce this Subzone in the standard zonation was not adopted during the last meeting (Reboulet et al., 2018), due to some questions about the FAD of the index. After discussion, Company and Reboulet now agree that the FO of N. (V.) salinarium appears to be synchronous between various sections of south-east France and south-east Spain; its relative position in the bioevent succession and in the lithostratigraphic sequence is equivalent in both geographic areas. This species also occurs in Morocco (Ettachfini, 2004), Italy, Austria, Hungary, the Czech Republic, Slovakia and Poland (see synonymy in Klein et al., 2009), and was also found in Mexico (unpublished data). (12*in Fig. 2). Neocomites neocomiensiformis Zone Definition. It is divided into a lower N. neocomiensiformis Subzone and an upper Busnardoites campylotoxus Subzone. They are defined by the FAD of their index species. Upper bounding horizon of B. campylotoxus Subzone is the FAD of Karakaschiceras inostranzewi, index of the overlying zone. Remarks. The introduction of B. campylotoxus Subzone into the standard zonation was proposed by Reboulet et al. (2022). They underlined that the index-species is easy to identify, abundant, and has a widespread palaeogeographic distribution throughout the Mediterranean area. The assemblage characteristic of this interval has been recognized in Morocco (Wippich, 2003;Ettachfini, 2004; Reboulet et al., 2022), south-east Spain (Company and Tavera, 2015), south-east France (Bulot, 1995;Reboulet, 1996) and Crimea (Baraboshkin and Mikhailova, 2000). Reboulet et al. (2022) also provided an updated discussion on the N. neocomiensiformis Zone and the B. campylotoxus Subzone, and on their equivalent units, in terms of stratigraphic interval, in local zonal schemes of Morocco, Spain and France. 2.4. Hauterivian Company and Reboulet's proposals and suggestions were accepted as follows. (13*in Fig. 2). Crioceratites loryi Zone Definition. This interval zone is defined by the FAD of its index species and the FAD of Lyticoceras nodosoplicatum, the index of the overlying zone. Remarks. Bert et al. (2021) proposed Crioceratites claveli Zone to replace Crioceratites loryi Zone in south-east France. As C. claveli has only been reported from France and Italy, the KG suggested that the potential long-distance correlation of the index species should be tested before changing the standard zonation. For the moment, as a provisional solution, the base of the C. loryi Zone is unchanged (and the A. radiatus Zone also) and we consider that the base of the C. loryi Zone (sensu the KG) is defined by the FAD of the index-species Crioceratites group claveli-loryi. The KG is waiting for the C. claveli to be recognized elsewhere in the Mediterranean Province. (14*in Fig. 2). Horizons of Breistrofferella castellanensis,Olcostephanus (Olcostephanus) variegatus,Cruasciceras cruasense and Subsaynella begudensis These units are abandoned. Remarks. The general reasons to delete horizons of the standard zonation were presented in the previous KG report in which the horizons of the Barremian stage were removed (Reboulet et al., 2018). Thus, the standard Hauterivian zonation equates the other Lower Cretaceous stages where the group had already suppressed the horizons. The former Breistrofferella castellanensis Horizon, introduced into the standard zonation by Hoedemaeker et al. (2000), was not relevant as its range overlaps almost the whole A. radiatus Zone (Reboulet, 1996 and references therein). Cruasiceras cruasense and Subsaynella begudensis have very restricted distribution (in the platforms bordering the Vocontian Basin) as reported by Reboulet et al. (2009). (15*in Fig. 2). Olcostephanus (Olcostephanus)variegatus Subzone Definition. The former Olcostephanus (Olcostephanus)variegatus Horizon is raised here to the rank of a subzone. Its base is defined by the FAD of Lyticoceras nodosoplicatum as the FO of O. (O.) variegatus is recorded few beds below the index-species of the zone (see references in Hoedemaeker et al., 2003). The top of this subzone corresponds to the last occurrence of O. (O.) variegatus. The last O. Szives, J.A. Moreno-Bedmar, B. Aguirre-Urreta et al. Cretaceous Research 153 (2024) 105716 8 specimens of this index species disappear before the end of the L. nodosoplicatum Zone; so, the top of the O. (O.) variegatus Subzone does not match with the top of the L. nodosoplicatum Zone. The top of the O. (O.) variegatus Subzone must be put slightly lower than the top of the L. nodosoplicatum Zone; see Figure 1a in Reboulet et al. (2018). Remarks. The index species has been recorded throughout the Mediterranean Province (from Morocco to Bulgaria) and also in Argentina, Colombia and Tanzania (see synonymy in Klein 2005). O. (O.) variegatus is very useful for correlations between the West Mediterranean and North-West European provinces and between the West Mediterranean Province and the Neuqu en Basin (Argentina) as reported by Reboulet et al. (2014, see level 9 in figure 4, and level 6 in figure 5, respectively). (16*in Fig. 2). Balearites angulicostatus Subzone Definition. The base of this subzone is defined by the FAD of its index species and top of the subzone is by the FAD of Pseudothurmannia ohmi, index of the overlying zone. Remarks. Spathiocrioceras seitzi is replaced by Balearites angulicostatus as index species of the fourth Subzone of the Balearites balearis Zone, as proposed by Lukeneder during the 6th KG meeting (Reboulet et al., 2018). This is justified according to MatamalesAndreu and Company (2019) who considered S. seitzi as junior synonym of B.angulicostatus. All subzonal index-speciesof the B. balearis Zoneareassignedthe genus Balearites sincetheyseemtoconstitutea continuous phylogenetic lineage in ascending order («balearisebinelliekrenkelieangulicostatus »,Company et al., 2003,2010). (17*in Fig. 2). Pseudothurmannia ohmi Zone Definition. No change. Remarks. The inverted commas in «Pseudothurmannia ohmi »are removed. During the 2008 Vienna meeting (Reboulet et al., 2009), it was recommended to add inverted commas to mean that P. ohmi was awaiting a redefinition. This was made by Matamales-Andreu and Company (2019) who completed a huge study on Balearites angulicostatus and Pseudothurmannia ohmi. (18*in Fig. 2). Pseudothurmannia mortilleti Subzone Definition. According to Lukeneder's proposal (in Reboulet et al., 2018), it was decided here to use Pseudothurmannia mortilleti as index species of the second subzone of the P. ohmi Zone, instead of Pseudothurmannia catulloi as this latter is considered as a junior synonym (Vermeulen et al., 2002,2019a,b;Vermeulen 2003,2005; Company et al., 2003,2005,2008,2010;Lukeneder, 2012,2017). More recently, P. catulloi and P. mortilleti Subzones were synonymized by Matamales-Andreu and Company (2019), following Company et al. (2003). 2.5. Barremian (19*in Fig. 3). Toxancyloceras vandenheckii Zone Definition. Company and Reboulet suggested only a small modification regarding the Toxancyloceras vandenheckii Subzone and Zone. Its base is now defined as an interval zone by the FAD of the genus Toxancyloceras instead of by that of the index species. Indeed, according to Bert et al. (2018),theFOofT. vandenheckii seems to be shortly preceded by the FO of another species of the same genus, Toxancyloceras canuti. To maintain the stability of the standard zonation and waiting to confirm the stratigraphic distribution of T. canutiinotherMediterraneanbasins, the groupagreedtodefinethe base of the T. vandenheckii Zone and Subzone by the FADof the genus. Remarks. This species is dedicated to Abbot Van den Hecke. Astier, when defined it, wrote as „Vanden-Heckii”. This is not a lapsus calami, because he wrote it the same way every time he cited the species. In addition, his work was published in two different media (in the Annales des Sciences Physiques et Naturelles de Lyon and as an independent publication by the author) and Astier did not proofread it. The case probably was that Astier derived the specific name of the species from the latinized version of Van den Heckee which is Vandenheckius, and its genitive is Vandenheckii. This is explained in the ICZN 31.1 article and was quite common among the authors of the mid19th century (duvalii,emericii,hugii,jeanottii etc.). This article overwrites article ICZN 32.5.1, therefore the rightful specific name is „vandenheckii”. (20*in Fig. 3).Martelites sarasini Zone Definition. No change. Remarks. Concerning the content of the M. sarasini Zone, a suggestion was made by Frau as to replace the Pseudocrioceras waagenoides Subzone by the Pseudocrioceras mazierei Subzone, see Frau and Delanoy (2022) for further explanations. This point will be discussed more extensively at the next meeting. 2.6. Aptian The two-folded Aptian is kept here. 2.6.1. Lower Aptian No change in lower Aptian ammonite scale. 2.6.2. Upper Aptian Several changes are proposed in Warsaw by Szives as recent zonal standards of the upper Aptian (Reboulet et al., 2018;Gale et al., 2020) are partly due to the proposed retention of zonal indices of ‘Nolaniceras nolani’and ‘Hypacanthoplites jacobi’Zones (Bulot et al., 2014b;Frau et al., 2016a). Changes of these indices involve the problem of basal Albian ammonite scale. It is a long-known fact that zonation of the lower Albian in terms of ammonites using the Leymeriella lineage is highly problematic (detailed in Kennedy et al., 2000). As a result, the SMAZ of these substages was highly inaccurate as it was previously pointed out since Hoedemaeker et al. (1990) through Reboulet et al. (2018) and Gale et al. (2020).In2017 on the Vienna meeting, KG members postponed changing the Aptian and Albian zonation due to lack of experts on the meeting, but explained the need for major modifications during the next meeting in 2022. In order to make a good progress during the KG meeting in Warsaw in 2022, a small group of AptianeAlbian experts eSzives, Owen, Latil, Robert, Lehmann and Moreno-Bedmar ewere previously evoked to make suggestions towards the necessary changes of the Aptian and Albian SMAZ scheme. Zonation of the upper Aptian to upper Albian is strongly modified on the basis of the detailed proposal by this group (Szives et al., 2023). Changes and suggestions were accepted as follows. (21*in Fig. 3). Parahoplites melchioris Zone Definition. No change. Remarks. Use of P. melchioris as a zonal index is debatable as detailed in Szives et al. (2023). Nothing is agreed as a replacement and this point will be a task of the next meeting. (22*in Fig. 3). Diadochoceras nodosocostatum Zone Definition. D. nodosocostatum Zone emerged to zonal rank as its index is common in the Western Tethys (Klein and Bogdanova, O. Szives, J.A. Moreno-Bedmar, B. Aguirre-Urreta et al. Cretaceous Research 153 (2024) 105716 9