Camille Frau
email: camille_frau@hotmail.fr

William A P Wimbledon

Christina Ifrim

Luc G Bulot

Alexandre Pohl

Berriasian ammonites of

Keywords: Ammonites, Berriasian, 'Ryazanian', Russian platform, Systematics

come

Introduction

The ammonite faunas at the Jurassic-Cretaceous transition show the highest provincialism in the Mesozoic, reflecting the separation of the Tethyan and the Austral realms and the various boreal basins [START_REF] Westermann | Biochore classification and nomenclature in paleobiogeography: an attempt at order[END_REF]. Provincialism is also marked within the realms since, for example, Arctic, Boreal-Atlantic and Boreal-Pacific subrealms have been distinguished in the 'Boreal Realm' at that time (Lehmann et al., 2015 and references therein). This severe biological restriction has for generations prevented substantial progress in long-distance correlation [START_REF] Wimbledon | The Jurassic-Cretaceous boundary: an age-old correlative enigma[END_REF], and strongly influenced the use of regional stage names for these deposits (e.g., "Purbeckian", "Portlandian", "Volgian", and 'Ryazanian' for the boreal/sub-boreal regions and beyond) even after the ratification of the Tithonian and Berriasian as the global stages for the uppermost Jurassic and lowermost Cretaceous, respectively [START_REF] Sarjeant | The terminal Jurassic stage: history of a controversy in stratigraphy[END_REF][START_REF] Cope | Drawing the line: the history of the Jurassic-Cretaceous boundary[END_REF][START_REF] Cope | Stage nomenclature in the uppermost Jurassic rocks of Britain[END_REF][START_REF] Wimbledon | The Jurassic-Cretaceous boundary: an age-old correlative enigma[END_REF][START_REF] Wimbledon | Fixing a basal Berriasian and Jurassic/Cretaceous (J/K) boundaryis there perhaps some light at the end of the tunnel?[END_REF]. Although the formal selection of a GSSP (Global Boundary Stratotype Section and Point) for the Berriasian is pending, the incoming of small, globular forms of Calpionella alpina and the sharp decline in abundance of Crassicollaria calpionellid species, which together define the base of the Calpionella Zone, have been formally selected as primary boundary markers for the base of the stage (with supporting nannofossils, calcareous dinoflagellates, ammonites, and magnetostratigraphy) [START_REF] Wimbledon | Developments with fixing a Tithonian/Berriasian (J/K) boundary[END_REF][START_REF] Wimbledon | Fixing a J/K boundary: A comparative account of key Tithonian-Berriasian profiles in the departments of Drôme and Hautes-Alpes, France[END_REF]. Unfortunately, the extreme isolation of the boreal basins, which lack calpionellids and other secondary markers, prevents the direct recognition of the putative boundary there [START_REF] Wimbledon | Warsaw remarks -Berriasian progress[END_REF][START_REF] Schnabl | A review of magnetostratigraphic results from the Tithonian-Berriasian of Nordvik (Siberia) and possible biostratigraphic constraints[END_REF]. Furthermore, the correlation of ammonites in Russian Tithonian and Berriasian boreal sections with a standard Mediterranean ammonite scale (SMAS sensu [START_REF] Reboulet | Report on the 6 th International Meeting of the IUGS Lower Cretaceous Ammonite Working Group, the Kilian Group[END_REF] remains an intractable problem (e.g., [START_REF] Sazonova | Berrias Russkoi platformy (Stratigrafiya. Fauna ammonitov i autsell)[END_REF][START_REF] Sazonova | Berriasian marine faunas. Ammonites from Russian lowland[END_REF][START_REF] Sazonova | Ammonites of the Jurassic-Cretaceous Boundary Beds of Russian Platform[END_REF][START_REF] Casey | The ammonite succession at the Jurassic-Cretaceous boundary in eastern England[END_REF][START_REF] Casey | Ammonite zones in Boreal Jurassic-Cretaceous boundary strata[END_REF]Mitta, 2005Mitta, , 2017;;[START_REF] Zakharov | Let the Volgian stage stay in the Jurassic[END_REF][START_REF] Schnabl | A review of magnetostratigraphic results from the Tithonian-Berriasian of Nordvik (Siberia) and possible biostratigraphic constraints[END_REF]. This is not only due to condensation and erosional episodes in the Russian platform 'Ryazanian' deposits

In cases where descriptions are given for the newly introduced taxa, comparisons with the type species of the genera are insufficient and some of the generic identifications have been repeatedly revised (compare systematic treatement between Mitta, 2002 andMitta, 2018 for example).

Research conducted in the past several years within the Berriasian Working Group of the International Subcommission on Cretaceous Stratigraphy questions such systematics and correlation. It has been demonstrated that the provincialism of the neocomitid and himalayitid ammonites is higher than previously assumed in the literature, and that homeomorphy has led to erroneous taxonomic interpretations (see [START_REF] Bulot | New and poorly known Perisphinctoidea (Ammonitina) from the Upper Tithonian of Le Chouet (Drôme, SE France)[END_REF][START_REF] Frau | The late Tithonian Himalayitidae (Perisphinctoidea, Ammonitina) from Le Chouet (Drôme, France): systematic implications[END_REF]Frau et al., , 2016aFrau et al., , 2016bFrau et al., , 2016c;;[START_REF] Lehmann | Chapter 9. Paleobiogeography of early Cretaceous ammonites[END_REF]. In particular, a re-examination of the Russian literature leads us to challenge the occurrence of western Tethyan-derived ammonites in the 'Ryazanian' deposits, as testified by the systematic re-assessment provided in the present contribution.

Material and methods

This work is based on a re-examination of the figured Russian later Berriasian ('Ryazanian') ammonite taxa of supposed Tethyan origin from the Moscow and Ryazan regions (Fig. 1), as documented by Vasily V. Mitta and collaborators (Mitta, 2002(Mitta, , 2004(Mitta, , 2005(Mitta, , 2007a(Mitta, , 2007b(Mitta, , 2008[START_REF] Mitta | Ammonites of Tethyan origin from the Ryazanian of the Russian platform: genus Subalpinites Mazenot[END_REF](Mitta, , 2011a(Mitta, , 2011b(Mitta, , 2017(Mitta, , 2018;;[START_REF] Mitta | Subdivision of the Ryazanian Stage of Russian platform[END_REF][START_REF] Mitta | Ammonite distribution across the Jurassic-Cretaceous boundary in Central Russia[END_REF]. Apart from endemic Russian forms, most of the species identified by those authors were assigned to the Neocomitidae [START_REF] Salfeld | Kiel-und Furchenbildung auf der Schalenaussenseite der Ammonoideen in ihrer Bedeutung für die Systematik und Festlegung von Biozonen[END_REF], viz. Berriasella Uhlig, 1905 (type species: Ammonites privasensis Pictet, 1867), Euthymiceras [START_REF] Grigorieva | Lower Valanginian ammonite fauna from the Belaya River basin on the northern slope of the Caucasus Mountains (Maikop area)[END_REF] (type species: Ammonites euthymi Pictet, 1867), Subalpinites [START_REF] Mazenot | Les Palaeohoplitidae Tithoniques et Berriasiens du Sud-Est de la France[END_REF] (type species: Subalpinites fauriensis [START_REF] Mazenot | Les Palaeohoplitidae Tithoniques et Berriasiens du Sud-Est de la France[END_REF], Malbosiceras Grigorieva, 1938 (type species: Ammonites malbosi [START_REF] Pictet | Études paléontologiques sur la faune à Terebratula diphyoides de Berrias (Ardèche). Mélanges Paléontologiques[END_REF], Mazenoticeras Nikolov, 1966 (type species: Berriasella broussei [START_REF] Mazenot | Les Palaeohoplitidae Tithoniques et Berriasiens du Sud-Est de la France[END_REF], Pomeliceras [START_REF] Grigorieva | Lower Valanginian ammonite fauna from the Belaya River basin on the northern slope of the Caucasus Mountains (Maikop area)[END_REF] (type species: Ammonites breveti [START_REF] Pomel | Les Céphalopodes néocomiens[END_REF], and the Himalayitidae [START_REF] Spath | Ammonites and Aptychi. The Collection of Fossils and Rocks from Somaliland[END_REF], viz. Dalmasiceras Djanélidzé, 1922 (type species: Ammonites dalmasi [START_REF] Pictet | Études paléontologiques sur la faune à Terebratula diphyoides de Berrias (Ardèche). Mélanges Paléontologiques[END_REF]. The type species of all these genera originate from southeast France (Vocontian domain) and the historical type sections for the Berriasian Stage, except those of Pomeliceras from Ouled Mimoun, Algeria (Fig. 1).

The type material of the French species is still housed in the Grenoble, Lyon, and Genève universities, allowing their re-examination and comparison with the Mitta (2008), the branching coefficient indicates the ratio of the number of the secondary and primary ribs per half-whorl at the end of the Riasanites phragmocones.

Systematic palaeontology

Order Ammonoidea [START_REF] Zittel | Cephalopoda[END_REF]Suborder Ammonitina Hyatt, 1889 Family Riasanitidae n. fam.

Etymology: Refers to the ammonite genus Riasanites [START_REF] Spath | VII. Appendix. On ammonites from New Zealand[END_REF] Type genus: As here designed, Riasanites [START_REF] Spath | VII. Appendix. On ammonites from New Zealand[END_REF]. The type species is Riasanites rjasanensis (Nikitin, 1888); by original designation. According to Article 12.1 of the ICZN, Nikitin (1888) is the author of the species rjasanensis since the previous introduction of the nominative name by [START_REF] Lahusen | Die Fauna der jurassischen Bildungen des Rjasanschen gouvernement[END_REF] lacks description, definition, or indication for the taxon.

Content:

The Riasanitidae n. fam., as herein understood, includes the genera:

-Gechiceras Sakharov, 1982, type species: G. kistense Sakharov, 1982 -Tauricoceras Kvantaliani and[START_REF] Kvantaliani | A new Berriasian genus Tauricoceras[END_REF], type species: T. crassicostatus [START_REF] Kvantaliani | Berriasian cephalopods of the Crimea and the Caucasus[END_REF]Lysenko, 1979 (= Subriasanites Sazonova in Sazonova and[START_REF] Sazonova | Stratigraphie classification of the Lower Cretaeeous of the East-European Platform (Russian subboreal province). Byulleten' Moskovskogo Obshchestva Ispytalelei Prirody[END_REF], type species: R. rjasanensis maikopensis [START_REF] Grigorieva | Lower Valanginian ammonite fauna from the Belaya River basin on the northern slope of the Caucasus Mountains (Maikop area)[END_REF] -Riasanites Spath, 1923, type species: Riasanites rjasanensis (Nikitin, 1888) -Riasanella Mitta, 2011a, type species: R. rausingi Mitta, 2011b-Prorjasanites Sazonova, 1977, type species: P. plumatus [START_REF] Sazonova | Ammonites of the Jurassic-Cretaceous Boundary Beds of Russian Platform[END_REF] -Mittaites n. gen., type species: Mazenoticeras ceccai Mitta, 2011a (see discussion below).

Diagnosis:

The new family is defined as grouping earliest Cretaceous small-to largesized, dimorphic, moderately evolute, planulate ammonites with a compressed, subrectangular, suboval or suboctagonal whorl section marked by a flattened to slightly rounded venter. A narrow ventral furrow occurs in the juvenile whorls, but it weakens and/or disappears in the adult. Microconchs bear lappeted peristomes, whereas it is simple on macroconchs. Ornamentation generally consists of simple, bior trifurcate, rarely fasciculate sharp ribs and a variable number of intercalatories.

Enlarged, crest-or node-like bulges can develop on the peri-umbilical, lateral and peri-ventral margins. When known, suture lines develop long and more or less symmetrical ventral and first lateral lobes while other ones are small.

Remarks:

The lower Berriasian ammonite assemblages of the Mediterranean-Caucasian Subrealm are rather uniform and dominated by the Neocomitidae Berriasella, Pseudosubplanites, Malbosiceras, Delphinella, Strambergella, Pseudoneocomites, and the Himalayitidae Chapericeras, Kilianites, and Praedalmasiceras [START_REF] Lehmann | Chapter 9. Paleobiogeography of early Cretaceous ammonites[END_REF]Frau et al., 2016aFrau et al., , 2016bFrau et al., , 2016c)). This assemblage has no equivalent in the Boreal subprovinces at that time due to paleogeographic restriction [START_REF] Lehmann | Chapter 9. Paleobiogeography of early Cretaceous ammonites[END_REF]. During the middle Berriasian, the paleobiogeographic affinities between the western and eastern Mediterranean-Caucasian ammonite assemblages break out and new endemic ammonite genera develop throughout the Caucasian and Transcaspian areas (Crimea, Caucasus, and Mangyshlak), including Gechiceras, Tauricoceras, and Riasanites (e.g., [START_REF] Luppov | from the Mangyshlak Peninsula; (A-C) holotype[END_REF][START_REF] Kvantaliani | Berriasian cephalopods of the Crimea and the Caucasus[END_REF][START_REF] Kalacheva | Ammonites[END_REF][START_REF] Arkadiev | Berriasian of Crimean Mountains[END_REF]. In the current state of knowledge, the affinities of this fauna are even stronger with those from the eastern European part of the Boreal Atlantic Subrealm (Polish Lowland and Russian Platform) as exemplified by the dispersion of Riasanites (Mitta, 2008;[START_REF] Mitta | Comparative study of the Berriasian ammonites of Poland and Central Russia (Preliminary data)[END_REF].

According to [START_REF] Kvantaliani | Berriasian cephalopods of the Crimea and the Caucasus[END_REF], the genera Gechiceras, Tauricoceras, and Riasanites form a direct lineage rooted in the Neocomitidae sensu lato through the Neocosmoceras and Euthymiceras relatives from the Trans-Caucasian areas (see Kvantaliani, 1999, fig. 22). Unfortunately, the affinities between those forms and the typical Neocosmoceras and Euthymiceras relatives from the western Mediterranan-Caucasian Subrealm have never been substantiated in the literature. As such, the link between the Neocomitidae and the Gechiceras-Tauricoceras-Riasanites lineage is still to be resolved. Mitta (2008) documented the variability of the Riasanites relatives thanks to abundant collection from the 'Ryazanian' deposits of the Russian Platform. Mitta (2011b, p. 17) assigned Riasanitesa senior synonym of Tauricoceras according to the authorto the Himalayitidae because of a supposed phyletic link with Transcaspiites Luppov in Bogdanova et al., 1985 (type species: Protacanthodiscus transcaspius Luppov, Bodylevsky and[START_REF] Luppov | Klass Cephalopoda. Golovonogie (Class Cephalopoda)[END_REF]. Transcaspiites share great affinities with the Himalayitidae Protacanthodiscus Spath, 1923 in the juvenile whorls, namely an inflated planulate shell and a weak ventral band [START_REF] Frau | The late Tithonian Himalayitidae (Perisphinctoidea, Ammonitina) from Le Chouet (Drôme, France): systematic implications[END_REF].

But Transcaspiites develops prominent tubercles on the upper flank that enlarge as growth increases and give a sub-coronate section to the whorl (see [START_REF] Bogdanova | The genus Transcaspiites Luppov, gen. nov., and its systematic position[END_REF]. Such himalayitid features are not observed in the Gechiceras, Tauricoceras and Riasanites relatives. As such, the link between those forms and the Himalayitidae is doubtful. [START_REF] Bulot | New and poorly known Perisphinctoidea (Ammonitina) from the Upper Tithonian of Le Chouet (Drôme, SE France)[END_REF] [START_REF] Bulot | New and poorly known Perisphinctoidea (Ammonitina) from the Upper Tithonian of Le Chouet (Drôme, SE France)[END_REF]. However, P. elsae is a latest Tithonian endemic ammonite from southern France known from a very restricted number of specimens (Bulot et al., 2014, text-fig. 6;Frau et al., 2016b, text-fig. 6H). Riasanites differs from P. elsae in having a subtrapezoidal whorl section converging towards the venter, a narrow ventral groove, umbilical nodes and a ventral chevron in the adult [START_REF] Bulot | New and poorly known Perisphinctoidea (Ammonitina) from the Upper Tithonian of Le Chouet (Drôme, SE France)[END_REF]. As a result, the affinities between Riasanites and Pratumidiscus are unlikely.

Considering their morphological and ornamental affinities, we here follow the views of [START_REF] Kvantaliani | Berriasian cephalopods of the Crimea and the Caucasus[END_REF] that the genera Gechiceras, Tauricoceras, and Riasanites form a direct lineage. Pending the study of the Trans-Caucasian neocomitid-like forms here referred to as "Neocosmoceras" and "Euthymiceras", we propose to separate this lineage by the introduction of the new family Riasanitidae n. fam. Its origin among the neocomitid rootstock cannot be upheld and needs further investigation.

Genus Riasanites [START_REF] Spath | VII. Appendix. On ammonites from New Zealand[END_REF] Type species: Riasanites rjasanensis (Nikitin, 1888).

Emended diagnosis:

Riasanites innermost whorls have moderately evolute, planulate shell with a deep umbilicus, depressed, subrectangular to subtrapezoidal whorl section with a flattened venter marked by a slight ventral band (R. rjsanensis morphotype) or a deep furrow (R. swistowianus morphotype). The species then develops four ornamental stages (Fig. 2A-C): (i) a juvenile stage marked by approximated, straight to slightly convex, robust ribs; (ii) a neocomitid-like sub-adult stage that bears spaced, prorsiradiate to slightly sinuous, broad, mainly bifurcate and simple primary ribs with variable intercalatories. Ribs are enlarged into discrete or distinct bullae on the periumbilical margin and they bifurcate above mid-flank. Ribs are interrupted on the venter forming a narrow, shallow groove or they cross it forming a slight chevron at later growth stages; (iii) an adult stage marked by distant, rectiradiate to slightly projected, irregular bifurcate and simple primary ribs and, generally, one sinuous intercalatory. Lateral parts of the ribs or their points of furcation are enlarged as crestlike bulges; (iv) a terminal stage characterized by spaced, simple, annular primary ribs and rare intercalatories. Suture lines bear long and more or less symmetrical ventral and 1 st lateral lobes while the other ones are small. Riasanites is dimorphic and includes small-sized, microconchs (mean diameter ~38 mm) with scaphitoid outer whorls and potentially with lappets and larger macroconchs (mean diameter ~60 mm) with simple peristome (compare Fig. 2B,C).

Remarks:

In the Fossilium Catalogus, [START_REF] Klein | Lower Cretaceous ammonites I. Perisphinctaceae 1. Himalayitidae, Olcostephanidae, Holcodiscidae, Neocomitidae, Oosterellidae[END_REF] listed six species into the genus Riasanites including the type species R. rjasanensis (Nikitin, 1888) and the subspecies R. rjasanensis caucasicus [START_REF] Khimchiashvili | Tithonian and Berriasian Ammonites of the Caucasus[END_REF], as well as R.

bogoslowskii [START_REF] Luppov | Berriasian of Mangyshlak[END_REF], R. decorus Sazonova, 1977, R. densicostatus [START_REF] Khimchiashvili | Tithonian and Berriasian Ammonites of the Caucasus[END_REF], R. subrjasanensis (Nikitin, 1888), and R swistowianus (Nikitin, 1888). The subspecies R. rjasanensis maikopensis [START_REF] Grigorieva | Lower Valanginian ammonite fauna from the Belaya River basin on the northern slope of the Caucasus Mountains (Maikop area)[END_REF] was considered valid by [START_REF] Klein | Lower Cretaceous ammonites I. Perisphinctaceae 1. Himalayitidae, Olcostephanidae, Holcodiscidae, Neocomitidae, Oosterellidae[END_REF] and the author kept separate the genus Subriasanites. In his study on the Riasanites-type population from the Russian Platform, Mitta (2008) subsequently retained only four species into Riasanites including R. rjasanensis (and its junior synonyms R. subrjasanensis, Prorjasanites plumatus [START_REF] Sazonova | Ammonites of the Jurassic-Cretaceous Boundary Beds of Russian Platform[END_REF], P. vnigni Sazonova, 1977), R. swistowianus (and its junior synonym R. decorus), R. Maikopensis, and R. crassicostatus [START_REF] Kvantaliani | A new Berriasian genus Tauricoceras[END_REF]. The authors thus retained the genera Subriasanites, Prorjasanites, and Tauricoceras as junior synonyms of Riasanites.

According to Mitta (2011a), the separation of R. rjasanensis to R. swistowianus is based on their general morphology. R. rjasanensis develops involute shell (U/D ~0.39 and Ww/Wh ~0.76) with distinct subrectangular whorl section and slight ventral band while R. swistowianus develops more evolute shells (U/D ~0.46 and Ww/Wh ~0.86) with a subtrapezoidal whorl section and deep furrow (at least during the juvenile stage). Regarding the ornamentation, both species expose the four stages of the genus Riasanites defined above. R. swistowianus can be distinguished from R. rjasanensis by the reduced length of the sub-adult stage and extension of both the adult and terminal ones (compare Fig. 2A,B). Based on the available values, the branching coefficient found in the sub-adult and/or adult stages overlap and range from 1.1 to 2.4 (Mitta, 2011a). The branching coefficient cannot be, therefore, used as a reliable specific character. The morphometrics provided by Mitta (2011b) for 7 specimens assigned to R. rjasanensis (including the lectotype) and for 7 specimens assigned to R swistowianus show close covariation of involution and whorl proportions (Fig. 3).

They range from virgacone to extreme ophiocone morphotypes (0.33 ≤ U/D ≤ 0.50; 0.20 ≤ Ww/D ≤ 0.32). Such variabilities conform to robust versus slender poles of the Westermann's laws of shell covariation of a single species (compare Fig. 2D,E and Fig. 2F,G). Considering that the two taxa are concomitant in the 'Ryazanian' deposits, we here consider that R. rjasanensis and R. swistowianus form a single palaeospecies. R. rjasanensis is thereafter retained as the senior name by pagination priority in the work of Nikitin (1888) and its wide use in the literature. Note finally, that the available morphometrics of the Russian species R. subrjasanensis and R. decorus also fit well with the variability of R. rjasanensis (Table 1). Following [START_REF] Sey | Problems of the Boreal-Tethyan and inter-Boreal correlation of the Jurassic Cretaceous boundary sediments[END_REF] and Mitta (2008), these taxa are synonymised with the type species.

By contrast, the morphometrics of the northern Caucasus species R. maikopensis, R. rjasanensis caucasicus, and R. densicostatus differ from the Riasanites-type population by their larger size (78 mm ≤ D ≤ 145 mm), ophiocone to dactilicone morphotypes (0.41 ≤ U/D ≤ 0.52; 0.23 ≤ Ww/D ≤ 0.25) (see Table 1), and the presence of a stronger and simplier bifurcate ribbing through most of the ontogeny (see for example Grigorieva, 1938, pl. 1, fig. 1;Khimchiashvili, 1976, pl. 15, figs. 1, 2;pl. 17, fig. 1). Those taxa co-occur in the northern Caucasus with smaller forms referred to diverse Riasanites species (e.g., [START_REF] Khimchiashvili | Tithonian and Berriasian Ammonites of the Caucasus[END_REF][START_REF] Kalacheva | Ammonites[END_REF] and considered as the microconch counterpart of R. maikopensis (Mitta, 2008).

These microconchs similarly expose a strong and simple ribbing through the ontogeny while they develop a rounded whorl section, steep umbilical wall and flattened venter, at least on part of the phragmocone, lacking a clear ventral band or furrow. As such, the morphological and ornamental features of R. maikopensis and its supposed microconchs better conform to those found in the Tauricoceras relatives (compare with [START_REF] Kvantaliani | Berriasian cephalopods of the Crimea and the Caucasus[END_REF][START_REF] Kvantaliani | A new Berriasian genus Tauricoceras[END_REF][START_REF] Kvantaliani | Berriasian cephalopods of the Crimea and the Caucasus[END_REF]. Considering the differences in the juvenile morphology (i.e., rounded whorl section, lack of distinct ventral interruption) and restricted palaeogeographic distribution, we thus retain Tauricoceras as a valid and distinct genus to which we transfer the species R. maikopensis, R. rjasanensis caucasicus, and R. densicostatus. As such, the genus Subriasanites is here synonymized with Tauricoceras. Note that R. rjasanensis caucasicus, and R. densicostatus merely correspond to potential synonyms of T. maikopensis but the lack of inner whorls in their type material prevents further confirmation. Mitta (2008) suggested that the two Prorjasanites species P. plumatus [START_REF] Sazonova | Ammonites of the Jurassic-Cretaceous Boundary Beds of Russian Platform[END_REF]P. vnigni Sazonova, 1977, whose type material corresponds to incomplete phragmocones, illustrate the densely ribbed juvenile stage found in R. rjasanensis. This view is unlikely since none Riasanites specimens develop such dense ribbing in the inner whorls. At same size, the branching coefficient is markedly lower in Prorjasanites (estimation at ~0.45). As such, we keep separate the genera Riasanites and Prorjsanites (see further details below).

Finally, the species R. bogoslowskii [START_REF] Luppov | Berriasian of Mangyshlak[END_REF] was based on the hand drawn of a whorl fragment (holotype) from Russia illustrated by Bogoslovsky (1897, pl. 6, fig. 6a, b) and a poorly preserved fragment (paratype) from the Mangyshlak illustrated by Luppov (Luppov et al., 1988, pl. 13, fig. 7). The Bogoslovsky's hand-drawned specimen is characterized by a compressed, subrectangular whorl section which bears dense primary ribs thickened on the periumbilical margin as nodes and bifurcated on the flank. These features better conform to those found in the juveniles of Karasyazites Mitta, 2018 (see below). The Luppov's specimen is a whorl fragment of a Riasanitidae that lack diagnostic features. As such, we therein consider R. bogoslowskii as invalid with respect to the ICZN Code.

Content:

As herein understood, Riasanites should be restricted to the two following species:

-R. rjasanensis (Nikitin, 1888), including its junior synonyms R. subrjasanensis (Nikitin, 1888), R. swistowianus (Nikitin, 1888), and R. decorus [START_REF] Sazonova | Ammonites of the Jurassic-Cretaceous Boundary Beds of Russian Platform[END_REF] -R. transitionis (Mitta, 2018) (see discussion below).

Riasanites rjasanensis (Nikitin, 1888) (Fig. 2A-G)

1883 Ammonites rjasanensis -Wenetzky in Lahusen, p. 69. 1988 Riasanites cf. swistowianus (Nikitin) -Luppov in Luppov et al., p. 133, pl. 13, fig. 5a, b. ? 1988 Riasanites subrjasanensis (Nikitin) -Luppov in Luppov et al., p. 132, pl. 13, figs. 6, 8. non 1988 Riasanites aff. rjasanensis (Nikitin) -Luppov in Luppov et al.,p. 131,pl. 17 1999 Riasanites rjasanensis (Nikitin) - Kvantaliani, p. 148, pl. 40, figs. 1a, b, 2a, b;pl. 41, figs. 1a, b, 2a, b, 3a, b. 1999 Riasanites subrjasanensis (Nikitin) - Kvantaliani, p. 150, pl. 41, figs. 4a, b, 5a, b;pl. 42, figs. 1a, b, 2a, b;pl. 43, figs. 1a, b, 2a, b. 1999 Riasanites swistowianus (Nikitin) - Kvantaliani,p. 151,pl. 43,figs. non 2000 Riasanites subrjasanensis (Nikitin) - Kalacheva and Sey, p. 97, pl. 12, fig. 5a, b (= Sey and Kalacheva, 1999, pl. 3, fig. 3a, b);pl. 13, figs. 2a, b, 3a, b (= Sey and Kalacheva, 1999, pl. 3, fig. 2a, b);pl. 14, fig. 1 (= Sey and Kalacheva, 1999, pl. 1, fig. 3), 3a, b (= T. maikopensis).

non 2000 Riasanites swistowianus (Nikitin) - Kalacheva and Sey, p. 98, pl. 14, fig. 4 (= Sey and Kalacheva, 1999, pl. 3, fig. 4).

2007a Riasanites rjasanensis (Nikitin) - Mitta, pl. 2, fig. 1;pl. 3, figs. 3, 4. 2008 Riasanites rjasanensis (Nikitin) - Mitta, p. 256, text-fig. 1, pl. 5, figs. 1a, b, 2a, b (= Mitta, 2007a, pl. 2, fig. 1), 3, 4a, b, 6a, b, 7, 8, 9a, b. 2011 Riasanites rjasanensis (Nikitin) - Mitta and Sha,pl. 3,fig.

Type and studied material:

The lectotype designated by [START_REF] Kalacheva | Ammonites[END_REF] is specimen VSEGEI 1/81 (Nikitin's collection) from the Oka River, Ryazan region; hand-drawned by Nikitin (1888, pl. 1, fig. 1). The biometric study in Fig. 3 is based on the measured specimens from Mitta (2008) and those from [START_REF] Kvantaliani | Berriasian cephalopods of the Crimea and the Caucasus[END_REF] for R. subrjasanensis and [START_REF] Sazonova | Ammonites of the Jurassic-Cretaceous Boundary Beds of Russian Platform[END_REF] for R. decorus (see also Table 1)

Diagnosis: See above.
Remarks: Riasanites transitionis (Mitta, 2018) was originally assigned to the genus Transcaspiites. The species is close to R. rjasanensis from which it only differs by more inflated juvenile whorls with denser ribbing, thickened nodes on the adult whorl, and compressed whorl section in the adult microconchs (Mitta, 2018, p. 251).

Occurrence: In the Russian Platform, R. rjasanensis flourishes during the Riasanites rjasanensis and Surites spasskensis zones as defined by Mitta (2017). Beside Russia, the species also occurs in the Caucasus (e.g., [START_REF] Kvantaliani | Berriasian cephalopods of the Crimea and the Caucasus[END_REF], Mangyshlak [START_REF] Luppov | Berriasian of Mangyshlak[END_REF], Polish Lowland (e.g., Marek, 1967;[START_REF] Mitta | Comparative study of the Berriasian ammonites of Poland and Central Russia (Preliminary data)[END_REF], and doubtfully in the Middle Volga [START_REF] Rogov | The Jurassic-Cretaceous Boundary in the Middle Volga Region[END_REF]. The record of R. cf. swistowianus from Štramberk (Vašíček and Skupien, 2016, fig. 7B,C) should be ruled out since the corresponding specimen conforms well to small-sized (?microconch) individuals of T. crassicostatum (compare with Kvantaliani, 1999, pl. 35, fig. 2a, b for example). Finally, the reports of Riasanites from Mexico (Hoplites cfr. rjasanensis? in [START_REF] Burckhardt | La faune jurassique de Mazapil avec un appendice sur les fossiles du crétacique inférieur[END_REF] and Yemen (R. rjasanensis in [START_REF] Howarth | Ammonite and nautiloids from the Jurassic and Lower Cretaceous of Wadi Hajar, southern Yemen[END_REF] are based on misinterpretation of doubtful perisphinctoid specimens, while those from Argentina (Riasanites rjasanensoides Krantz in [START_REF] Krantz | La fauna del Titono superior y medio de la Cordillera Argentina en la parte meridional de la provincia de Mendoza[END_REF] have been re-assigned to Corongoceras (see [START_REF] Parent | The Tithonian-Berriasian ammonite fauna and stratigraphy of Arroyo Cieneguita, Neuquén-Mendoza Basin, Argentina[END_REF].

Genus Riasanella Mitta, 2011b

Type species: R. rausingi Mitta, 2011b; by original designation.

Diagnosis: See diagnosis of the type species, below.

Remarks: Mitta (2011b) introduced the genus Riasanellabased on R. riasanitoides, R. plana, R. rausingi, and R. olorizi the type speciesfor small-sized, neocomitid-like ammonites from the Russian platform. Their material originates from a thin, phosphatized sandstone horizon cropping out in quarry no. 12-2 of the Lopatinskii Phosphorite Mine, Moscow region. According to Mitta (2011b), R. olorizi differs from R. rausingi and R. plana by a larger size (average value of 60 mm for R. olorizi compared to 40 mm for the two other species), a lesser number of simple and intercalated ribs at a same diameter, and distinctly developed umbilical and lateral nodes in the adult. The predominance of intercalated and simple ribs on the phragmocone and the weakness or lack of crest-like bulges would also distinguish R. plana from R. rausingi and R. riasanitoides (Mitta, 2011b). Mitta (2011b) recognized the lineage R. olorizi → R. rausingi → R. plana but the condensation of their type horizon strongly suggests that this distinction is unlikely.

Differences in ribbing are not conclusive for specific identification, because Riasanella relatives display complex ribbing composed of slightly convex, simple, bi-, trifurcate and fasciculate ribs and irregular intercalatories (Fig. 2H-K). The thickening of the lateral crest-like bulges in the adult shows little variability among the population and cannot be used as a reliable diagnostic character. Finally, the morphometrics provided by Mitta (2011b) for the 29 known Riasanella type specimens most probably reflect intraspecific variability within a single palaeobiological taxon, rather than four distinct species. This is reflected by the covariation of involution and whorl proportions of the four Riasanella relatives (Fig. 4). The four species are here tentatively synonymised with the type species R.

rausingi.

Furthermore, [START_REF] Mitta | Ammonites of Tethyan origin from the Ryazanian of the Russian platform: genus Subalpinites Mazenot[END_REF]Mitta ( , 2011b) ) recognized the lineage Riasanella riasanitoides → Riasanites swistowianus → Riasanites rjasanensis morph α → Riasanites rjasanensis morph β. However, except for reports of doubtful relatives (i.e., Riasanites sp., ?Riasanites sp.) in underlying and overlying beds, all the Riasanites species co-occur in a restricted condensed horizon of 20 to 120 cm in thickness (Mitta, 2017, fig. 2). Contrary to Mitta (2008, pp. 252-253), the phyletic relationships between and among the Riasanella-Riasanites plexus remain uncertain, since Riasanites can only be distinguished by the reduced length of its adult stage, and a more depressed whorl section in the juvenile and involute coiling (Fig. 2H-K).

Pending more material, we suggest keeping separate the two genera. 2011b Riasanella plana - Mitta,p. 17,pl. 2,figs. 1a,b,2,3a,b,5,6,7a,b,9,10,11a,b. 2011b Riasanella rausingi -Mitta, p. 17 Type and studied material: The holotype designated by Mitta (2011b, pl. 2, fig. 4a, b) is specimen PIN 3990/264; here re-illustrated on Fig. 2H,I). It originates from the lower part of the Riasanites rjasanensis Zone as defined by Mitta (2017) from the quarry no. 12-2, Lopatinskii Phosphorite Mine, Moscow region. The biometric study conducted in Fig. 4 is based on the 29 type specimens measured by Mitta (2011b) (see also Table 1).

Emended diagnosis:

Small-sized, dimorphic, planulate ammonite with evolute to moderately involute coiling, subrectangular whorl section in the juvenile becoming subtrapezoidal to suboval in the adult. Umbilical wall is low, with rounded or gently sloping margin. Ornamentation encompasses, fully or partly, the four stages typical of Riasanites defined above. Suture line remains unknown.

Remarks: Specimens PIN 3990/369 and PIN 3990/371 were tentatively assigned to Malbosiceras sp. by Mitta (2011a, text-fig. d,e). Both specimens lack inner whorls but their last preserved whorls show close affinities with Riasanella relatives.

These specimens are tentatively referred to as Riasanella sp.

Occurrence: The species R. rausingi is restricted to the Rjasanites rjasanensis Zone of the Russian Platform -Moscow and (?) Ryazan regionaccording to Mitta (2008). The report of a single specimen assigned to R. cf. rausingi from the early Berriasian of Štramberk (Czech Republic) is doubtful since based on a poorly preserved perisphinctoid fragment that lacks any valuable diagnostic features (see [START_REF] Vašíček | Tithonian-early Berriasian perisphinctoid ammonites from the Štramberk Limestone at Kotouč Quarry near Štramberk, Outer Western Carpathians (Czech Republic)[END_REF], fig. 7A).

Genus Prorjasanites [START_REF] Sazonova | Ammonites of the Jurassic-Cretaceous Boundary Beds of Russian Platform[END_REF] Type species: Prorjasanites plumatus [START_REF] Sazonova | Ammonites of the Jurassic-Cretaceous Boundary Beds of Russian Platform[END_REF]; by original designation.

Diagnosis: see Sazonova (1977, p. 88).

Remarks: Mitta (2008) synonymised Prorjasanites with Riasanites considering that the Prorjasanites taxa P. plumatus and P. vnigni illustrate densely ribbed juveniles of Riasanites rjasanensis. As discussed above, the juveniles of R. rjasanensis never develop such dense ribbing (> 30 ventral ribs on the last preserved whorls at D ~30 mm) as those observed on Prorjasanites (compare with Mitta, 2008, pl. 5, figs. 5, 7 and pl. 6, figs. 1, 2 for example). As such, we prefer keeping separate the two genera.

The type material of P. plumatus and P. vnigni correspond to small-sized phragmocones (Fig. 5A-E). Their adult whorls thus remain unknown. Nevertheless, Mitta (2007a, pl. 3, figs. 6a, b, 7a, b) figured two Russian platform individuals (PIN 3990/260 and PIN 3990/261) whose inner whorls match well those of Prorjsanites (see Fig. 5F-H). The Mitta's specimen figured on Fig. 5F-G was selected as holotype of the species Berriasella rulevae Mitta, 2007a. This species has been subsequently transferred into Riasanites by Mitta (2011b) without explanation. The holotypes of B. rulevae and P. plumatus both originate from the Surites spasskensis Zone of the Spassk district [START_REF] Sazonova | Ammonites of the Jurassic-Cretaceous Boundary Beds of Russian Platform[END_REF]Mitta, 2007a). Their strong affinities and identical stratigraphical origin support a co-specificity between the two species. Pending more material, B. rulevae is thereafter transferred into Prorjsanites.

Content:

The genus Prorjasanites, as herein understood, includes P. plumatus, P. vnigni, and P. rulevae.

Prorjasanites rulevae (Mitta, 2007a) (Fig. 5) 2007a Berriasella rulevae - Mitta,p. 201,pl. 3,figs. 6a,b,7a,b. 2011b Riasanites aff. maikopensis Grigorieva -Mitta, fig. 3a,b.

2018 Riasanites aff. maikopensis Grigorieva -Mitta, pl. 5, fig. 6 (= ventral view of Mitta, 2011b, fig. 3a, b).

Type and studied material: The holotype designated by Mitta (2007a, pl. 3, fig. 6a,b) is specimen PIN 3990/260 from the Surites spasskensis Zone of the Oka River, downstream of the Nikitino village, Spassk district, Ryazan region; here re-illustrated in Fig. 5F,G. Other studied specimen includes PIN 3990/402 of same origin (Mitta, 2011b(Mitta, , 2018)). It is re-illustrated on Fig. 5H.

Diagnosis: Medium-sized, planulate ammonite with a subrectangular whorl section in the juvenile, which changes into a suboval whorl section, with flattened venter, slightly convex flanks and moderately low umbilical wall in the adult. Juvenile ornamentation composed of sharp, slightly flexuous to falcoid primary ribs and irregular intercalatories. Ribs are simple, bi-or trifurcate at mid-flank and they thicken towards the umbilicus. On the peri-ventral margin, branches of the ribs are slightly elevated, and there is a weak ventral furrow. In later growth stages, ribbing becomes more spaced and composed of irregular simple, bifurcate, rarely trifurcate, primary ribs with one or two intercalatories on the upper flank. Ribs tend to cross a rounded venter without weakening.

Remarks: Specimen PIN 3990/402 was tentatively assigned to Riasanites aff. maikopensis by Mitta (2011b, fig. 3a, b). This specimen can be distinguished from this species by its medium-sized, planulate shell with a suboval whorl section, slightly convex flanks, rounded venter and moderately low umbilical wall in the adult. The ornamentation comprises two stages marked by (i) dense, slightly flexuous to falcoid, mostly simple and bifurcate ribs and simple intercalatories; (ii) spaced and irregular simple and bifurcate ribs with generally one intercalatory in the upper flank. Ribs cross the venter without weakening on the last preserved whorl. By its morphological and ornamental features, specimen PIN 3990/402 is identical to P. rulevae.

Occurrence: Prorjasanites relatives are endemic to the Russian Platform and restricted to the lower part of the Surites spasskensis Zone as defined by Mitta (2017).

Genus Mittaites n. gen.

Etymology: Named in honour of the Russian ammonitologist Vasily V. Mitta for his contribution to the systematics of the 'Ryazanian'-type ammonites.

Type species: As designed herein, Mazenoticeras ceccai Mitta, 2011a.

Type locality: Lopatinskii Phosphorite Mine, Moscow region.

Diagnosis: Mittaites n. gen. groups dimorphic, medium-to large-sized, riasanitid planulate ammonites.

In the microconchs, the ornamentation shows three ornamental stages: (i) rigid, simple ribs in the juvenile which are more or less thickened on the upper flank; (ii) ribs spaced, prorsiradiate, simple and bifurcate, rarely trifurcate with, commonly, one single intercalatory in the subadult. Point of furcation of bifurcate ribs occur in the upper flank and thickens as growth increases; (iii) ribbing is markedly thickened and irregular in the adult. Ribbing is mainly composed of bifurcate or trifurcate ribs that form two sur-elevated, rounded node-or spine-like tubercles on the flanks and thickenings on the peri-ventral margin. The number of intercalatories is variable. The whorl section is compressed, sub-hexagonal during this stage, with a flattened to rounded venter with a narrow furrow. The last tends to disappear near the aperture.

Rare bifurcations of the primary ribs are observed from the umbilical nodes in M.

ceccai, but they bifurcate also at mid flank.

The macroconchs show the three ornamental stages described above, and they develop a terminal stage characterised by markedly spaced, elevated, mostly simple rib folds with smooth interspaces. The maximum rib thickness is reached on the venter.

Remarks: Mitta (2011a) introduced two new species assigned to the western Mediterranean-Caucasian neocomitid genus Mazenoticeras, namely M. robustum (holotype re-illustrated in Fig. 6A,B) and M. ceccai (Fig. 6C-E). Both species are characteristically medium-to large-sized, planulate, dimorphic shell with moderately evolute coiling. The whorl section is suboval, compressed (M. robustum) to depressed (M. ceccai) throughout ontogeny. The rounded umbilical wall becomes slightly steeper as at later growth stages. In juveniles, flanks and venter are flattened. By comparison, the type species Mazenoticeras broussei [START_REF] Mazenot | Les Palaeohoplitidae Tithoniques et Berriasiens du Sud-Est de la France[END_REF] differs distinctly from the Russian relatives by its less evolute coiling and its rectangular, higher-than-wide whorl section throughout ontogeny. M. broussei is also characterized by a flattened venter with a smooth band, except approaching the aperture. Its ornamentation changes little during ontogeny since it is characterised by gracile, bituberculate primary ribs that bi-or trifurcate on the mid-flank with a variable number of intercalatories. Pending comprehensive revision, the Russian forms cannot be included into Mazenoticeras given their low degree of similarity with the latter. The introduction of Mittaites n. gen., based on Mazenoticeras ceccai Mitta, 2011a, is here proposed to separate the Russian platform taxa.

Content: Mittaites n. gen. includes M. ceccai, M. robustum, and Hoplites micheicus Bogoslovsky, 1897 (see discussion below).

Mittaites ceccai (Mitta, 2011a) (Fig. 6C-E ) 2002 Euthymiceras euthymi (Pictet) - Mitta, pl. 3, fig. 4. 2005 Malbosiceras aff. boisseti Nikolov -Mitta, pl. 2, fig. 1a-c. 2006 Mazenoticeras cf. urukhense Kalacheva and Sey -Mitta, text-fig. 2. 2007a Mazenoticeras cf. urukhense Kalacheva and Sey -Mitta, pl. 2, fig. 4. 2011a Mazenoticeras ceccai -Mitta, p. 152, text-fig. 2, pl. 5, figs. 5a, b, 6a, b, 7;pl. 6, figs. 1a-c, 2a, b, 3a, b. Type and studied material: The holotype designated by Mitta (2011a, pl. 6, fig. 1ac) is specimen PIN 3990/386 from the Lopatinskii Phosphorite Mine, Moscow region; here re-illustrated in Fig. 6C-E. Other specimens include those figured by Mitta (2002Mitta ( , 2005Mitta ( , 2006Mitta ( , 2007aMitta ( , 2011a) ) (see synonymy list above).

Diagnosis: See Mitta (2011a, p. 152) and genus diagnosis above.

Remarks:

The large-sized body chamber PIN 3990/265, lacking inner whorls, was assigned to the species Mazenoticeras cf. urukhense by Mitta (2007a, pl. 2, fig. 4). Superficially, its morphological and ornamental features match those of the type series of M. urukhense, such as the largest examples from northern Caucasus illustrated by Kalacheva and Sey (2000, pl. 9, fig. 4 and pl. 10, fig. 2). Unfortunately, the lack of inner whorls prevents further comparison, as well as any discussion about the supposed coevality of M. urukhense and the genus Mazenoticeras. As herein understood, the specimen better compares with the body chamber of M. ceccai (compare with its holotype PIN 3990/386).

Two specimens (VNIGNI CR-2564 and CR-2565) were first assigned to Euthymiceras euthymi by Mitta (2002, pl. 3, fig. 4a, b) and Mitta (2002, pl. 3, fig. 5a, b). Both specimens were subsequently re-assigned to Mazenoticeras ceccai by Mitta (2011a, p. 147), a view followed here (see synonymy list above).

One specimen (PIN 3900/246) was assigned to Malbosiceras aff. boisseti by Mitta (2005, pl. 2, fig. 1a-c). In agreement with the subsequent revision by Mitta (2011a, p. 147), it is here re-assigned to M. ceccai.

Two further specimens (PIN 3990/387 and PIN 3990/392) were tentatively assigned to Mazenoticeras sp. by Mitta (2011a, text-figs. 3g, h, 4a-d). Both seemingly belong to M. robustum, since they closely match the specimen PIN 3990/383 (Mitta, 2011b, pl. 5, fig. 3a, b).

A specimen (AVS 1236) was identified as Pomeliceras sp. by Mitta (2011a, fig. 3a, b). However, it shows robust diagnostic juvenile features of M. robustum such as those observed in specimen PIN 3990/375 (Mitta, 2011b, text-fig. 3c, d); viz. a depressed, inflated shell with deep umbilicus, rounded venter with ventral weakening, and inflated upper lateral spines with a bundle of branches. Both specimens can be interpreted as to robust form of M. robustum with respect to its holotype.

Note finally that the specimen PIN 3900/248 identified as Malbosiceras nikolovi by Mitta (2005, pl. 2, fig. 4a-c) is here re-assigned to R. transitionis.

Occurrence: Representatives of Mittaites n. gen. are endemic to the Russian Platform and restricted to the lower part of the Riasanites rjasanensis Zone as defined by Mitta (2017). According to Mitta (2011a), M. robustum is stratigraphically older than M. ceccai. The latter was to be distinguished by its more inflated juvenile morphology and less coarse ribbing.

Mittaites micheicus [START_REF] Bogoslovsky | The Ryazan horizon: Its fauna, stratigraphical relations and probable age[END_REF] (Fig. 7A-C) 1897 Hoplites micheicus -Bogoslovsky, p. 94, pl. 6, fig. 1a-c Jeletzky, 1964, pl. 2, fig. 11a-c).

2007a Transcaspiites transfigurabilis (Bogoslovsky) - Mitta, pl. 3, figs. 1a-d, 2. 2008 Transcaspiites transfigurabilis (Bogoslovsky) - Mitta and Bogomolov, textfig. 1.2. 2018Transcaspiites tscheffkini -Mitta, p. 249, pl. 4, figs. 1 (= Mitta and Bogomolov, 2008, text-fig. 1.2), 2 (= Mitta, 2007a, pl. 3, fig. 1c, d).

Type and studied material: The holotype by monotypy is specimen VSEGEI 63-62/623 from the Pozhva River, downstream of the village of Mikhei, Sapozhok district. Photographs of the holotype are illustrated for the first time in Fig. 7A-C.

Other specimens include specimens figured by Mitta (2007a) and Mitta and Bogomolov (2018) which were assigned to Transcaspiites tscheffkini.

Emended diagnosis:

Small to medium size, planulate ammonite with an evolute coiling with a deep umbilicus. Whorl section is inflated and subhexgonal in the juvenile and becomes suboval, but markedly depressed, in the adult with a distinctly rounded umbilical wall. Venter is slightly flattened in the adult. Ornamentation encompasses the three ontogenetic stages of the microconch relatives. Stage (ii) is shorter than in the type species and marked by inflated ribs with massive tubercles at the point of furcation. Rib branches define a distinct ventral furrow. Stage (iii) comprises most of the last whorl, which is dominated by straight to prorsiradiate bifurcate ribs with elevated, extended tubercles on the flank. The number of intercalatories is variable. The rib section is sub-hexagonal with flattened to rounded venter without ventral weakening of the ribs.

Remarks: Mitta (2007a, pl. 3, figs. 1a-d, 2) and Mitta and Bogomolov (2008, textfig. 1.2) reported three closely allied specimens from the Oka River (PIN 3990/255, 3990/416, and 3990/256) identified as Transcaspiites transfigurabilis. The first two specimens have been subsequently re-interpreted as Transcaspiites tscheffkini Mitta, 2018. In our opinion, none of these specimens share the morphology and ornament that characterise the genus Transcaspiites. Indeed, the holotype of the type species T. transfigurabilis (re-illustrated by Luppov et al., 1949, pl. 64, fig. 3a,b) is a body chamber fragment that differs from Mitta's specimens in having a compressed, subhexagonal whorl section with a flattened venter bordered by enlarged bulges on the peri-ventral margin. The inner whorls of the holotype of T. transfigurabilis are lacking and prevent further comparison.

The early whorls of T. tscheffkini (Fig. 7D,E) share superficial affinities with those of the holotype of T. transcaspius (here re-illustrated on Fig. 7H-J), such as the depressed, inflated shell with deep umbilicus, ventral band, rounded venter with ventral weakening of the ribs, inflated upper lateral spines with bundle of branches. However, T. tscheffkini differs in having a depressed, subrounded whorl section in the adult that only bears uni-tuberculate bifurcate ribs and irregular intercalatories (Fig. 7F,G). Thus, T. tscheffkini does not truly compare to Transcaspiites.

Re-examination of the Bogoslovsky (1897)'s material from the Oka River suggests that T. tscheffkini is closely allied to the holotype of Hoplites micheicus Bogoslovsky, 1897 (see Fig. 7A-C), as illustrated in the emended diagnosis given above. To the difference of Luppov in Luppov et al. (1988, p. 128) Finally, Mitta (2018, figs. 3a-d, 4) assigned three incomplete specimens (PIN 3990/423, PIN 3990/424, and PIN 3990/442) from the Russian platform to Transcaspiites transfigurabilis. We are also reluctant to refer these specimens to Transcaspiites to which they only share a sub-hexagonal whorl section with a flattened venter in the adult. The Russian forms are far closer to 'Euthymiceras' from North Caucaus and Crimea, such as 'E.' euthymi as understood by [START_REF] Kvantaliani | Berriasian cephalopods of the Crimea and the Caucasus[END_REF], [START_REF] Kalacheva | Ammonites[END_REF] and [START_REF] Arkadiev | Representatives of the Neocosmoceras (Neocomitidae, Ammonoidea) genus from the Berriasian of the Crimean Mountains and their stratigraphic significance[END_REF]. Pending the systematic revision of the genus Euthymiceras, the occurrence of Transcaspiites in the Russian Platform should be ruled out.

Occurrence:

The precise stratigraphical origin of M. micheicus remains unknown.

However, its potential subjective synonym T. tscheffkini occurs in the lower part of the Surites spasskensis Zone as defined by Mitta (2017) in the Oka River section, downstream of the village of Nikitino, Ryazan district.

Family ?Neocomitidae [START_REF] Salfeld | Kiel-und Furchenbildung auf der Schalenaussenseite der Ammonoideen in ihrer Bedeutung für die Systematik und Festlegung von Biozonen[END_REF] Genus Karasyazites Mitta, 2018 Type species: Subalpinites bajarunasi [START_REF] Luppov | Berriasian of Mangyshlak[END_REF]; by original designation.

Emended diagnosis:

Small to medium-sized, neocomitid-like, dimorphic ammonite.

Microconchs characterized by moderately involute shell with a compressed, subrectangular to suboval whorl section marked by convex flanks, flattened venter and a moderately deep umbilicus, at least on the juvenile and sub-adult whorls.

Rounded in the juvenile, the umbilical wall becomes markedly steeper on the adult whorl. Ornamentation composed of dense, prorsiradiate to slightly flexuous, simple and bifurcate, rarely fasciculate ribs and rare intercalatories. Primary ribs thicken on the peri-umbilical margin as nodes, from which two ribs can branch. Ribs weaken on the venter and generally form a narrow ventral band that disappears at later growth stages.

Macroconchs are larger (D ≤ 140 mm) Inner whorls of which match those of the microconchs. They develop an adult stage marked by more evolute coiling with a compressed, subrectangular whorl section. Flanks are still convex, but the venter is subrounded. Umbilical wall is high, slightly oblique to rounded. Ornamentation changes to distant, prorsiradiate, uni-or bituberculate primary ribs that bi-or trifurcate on the upper flank, with a variable number of intercalatories. On body chamber, point of furcation can thicken and form slight tubercles. In the largest specimens, macroconchs develop a terminal stage marked by irregular, sparsely spaced attenuated ribs with enlarged peri-ventral clavi near the aperture. Specimen PIN 3990/418 (re-illustrated in Fig. 8F,G) is a large-sized incomplete individual while specimen AC 1112 is considered as its microconch counterpart.

Remarks

Specimen PIN 3990/418 conforms well to the holotype of K. bajarunasi but its affinities with AC 1112 are questionable. From our point of view, specimen AC 1112 better compares to Riasanites transitionis (compare with specimens figured by Mitta, 2018, pl. 5).

There is close affinity between specimen PIN 3990/418 and the Russian taxa referred to the genus Subalpinites; namely S. krischtafowitschi, S. Faurieformis, and S. gruendeli (see Mitta, 2002[START_REF] Mitta | Ammonites of Tethyan origin from the Ryazanian of the Russian platform: genus Subalpinites Mazenot[END_REF]. These species form a homogenous dimorphic group whose macroconchs are closely allied to K. bajarunasi (compare holotype VNIGNI CR-2562 of S. krischtafowitschi or paratype PIN 3990/329 of S. faurieformis for example -Fig. 8H-I). Unfortunately, Mitta (2018) only briefly discussed the relationships between K. bajarunasi and the genus Subalpinites, based on S. fauriensis. In our opinion, the Russian forms only exhibit superficial similarities with that genus. The type species S. fauriensis can be distinguished by its compressed, subrectangular whorl section with flattened venter, and its markedly steep umbilical wall that is found in all ontogenetic stages. This species also differs in showing an early appearance of a complex, uni-or bituberculate ornamental stage and in never developing the adult stage of the Russian forms. The largest specimens of S. fauriensis show dense or spaced, simple ribs that can branch from discrete or robust peri-umbilical bullae (see Le Hégarat, 1973, pl. 53, fig. 9;Nikolov, 1982, pl. 70, fig. 6a, b). As a result, the supposed affinities between the Trans-Caucasian and Mediterranean forms likely result from a basic case of homeomorphy. We, therefore, propose to gather the 'Subalpinites' relatives from the Russian Platform in the genus

Karasyazites.

Content: Subalpinites krischtafowitschi, S. faurieformis, and S. gruendeli are close to K. bajarunasi and they are herein transferred to Karasyazites. The Russian species Subalpinites remaneiformis [START_REF] Mitta | Ammonites of Tethyan origin from the Ryazanian of the Russian platform: genus Subalpinites Mazenot[END_REF] is provisionally kept in Karasyazites since its adult stage develop a peculiar ribbing that never occurs in Karasyazites (see Fig. 9A).

Note that Mitta (2005Mitta ( , 2007a) ) Frau et al. (2016a). The Russian forms merely belong to ?Karasyazites remaneiformis (compare with its paratype AVS 1002 re-illustrated in Fig. 9B,C).

Karasyazites bajarunasi [START_REF] Luppov | Berriasian of Mangyshlak[END_REF] (Fig. 8A-E ) 1988 Subalpinites bajarunasi -Luppov in Luppov et al.,p. 118,pl. 14,fig. 7;pl. 15,fig. Type and studied material: As designated by [START_REF] Luppov | Berriasian of Mangyshlak[END_REF], the holotype is specimen VSEGEI 11104/9 from the vicinity of Karasyaz Well, Mangyshlak. It was illustrated by Luppov in Luppov et al. (1988, pl. 15, fig. 1а, b) and re-illustrated herein in Fig. 8A,B. Other material includes the specimens figured by Mitta (2007aMitta ( , 2018) ) (see synonymy list above).

Diagnosis: See Mitta (2018, p. 251).

Remarks:

The early whorls/juveniles of Karasyazites relatives display a neocomitid pattern exemplified by a compressed, subrectangular planulate shell, ventral furrow, regular bifurcate or fasciculate ribbing with umbilical bullae (see for example specimen PIN 3990/332 or PIN 3990/329 of K. faurieformis). The closest affinities of Karasyazites relatives are found with the Trans-Caucasian 'Dalmasiceras' of the group of 'D.' abkhasica [START_REF] Khimchiashvili | Tithonian and Berriasian Ammonites of the Caucasus[END_REF](including D. belbekense Bogdanova and Arkadiev, 1999, D. miriani Kvantaliani, 1999, D. subtoucasi Bogdanova and Arkadiev, 1999, and D. tauricum Bogdanova and Arkadiev, 1999). Both forms cooccur in Crimea [START_REF] Arkadiev | Berriasian of Crimean Mountains[END_REF], northern Caucasus [START_REF] Kalacheva | Ammonites[END_REF] and Mangyslak [START_REF] Luppov | Berriasian of Mangyshlak[END_REF]. In our view, this species group deserves a full generic status since they only superficially match the type species D. dalmasi.

Pending such systematic revision, we provisionally refer Karasyazites to the Neocomitidae.

One specimen (PIN 3990/26) was assigned by Mitta (2007a, pl. 2, fig. 6a, b) to Malbosiceras cf. macphersoni. It corresponds to a medium-sized, chambered fragment with morphological (depressed suboval whorl section) and ornamental (periumbilical bullae, ventral weakening) features better match those observed in K.

faurieformis. It should be noted that the species macphersoni was considered as a subjective synonym of Ammonites chaperi Pictet, 1867; the type species of the genus Lopeziceras Frau et al., 2016a, but the genus should be considered as a junior subjective synonym of Chapericeras Hoedemaeker in Hoedemaeker et al., 2016, due to its later date of acceptance for publication.

Occurrence:

The taxon was originally reported from the Neocosmoceras and Septaliphoria semenovi Zone of the Mangyshlak [START_REF] Luppov | Berriasian of Mangyshlak[END_REF] and from the lower part of the Surites spasskensis Zone in the Russian Platform (Mitta, 2017).

Significance of the fauna

Most ammonite determinations introduced by Mitta and collaborators do not stand up well when comparisons and verification are attempted with the Mediterranean Neocomitidae and Himalayitidae. Our re-examination casts doubt on the occurrence of ammonites of western Tethyan-origin/affinity on the Russian Platform. A comparative account revising Mitta's taxonomy is given in Table 2. Our re-interpretation suggests that endemicity in that basin was higher than previously suggested, and this reinforces the view of that strong provincialism characterised it during the earliest Cretaceous [START_REF] Lehmann | Chapter 9. Paleobiogeography of early Cretaceous ammonites[END_REF].

Considering that no ammonite species enables correlation between the Tethyan and Boreal basins, magnetostratigraphy appears to be the most reliable tool to establish long-distance correlation [START_REF] Schnabl | A review of magnetostratigraphic results from the Tithonian-Berriasian of Nordvik (Siberia) and possible biostratigraphic constraints[END_REF]. It is now admitted that the putative base of the Berriasian approximately falls in the Craspedites taimyrensis Zone that marks the middle part of the upper 'Volgian' in the Arctic [START_REF] Schnabl | A review of magnetostratigraphic results from the Tithonian-Berriasian of Nordvik (Siberia) and possible biostratigraphic constraints[END_REF][START_REF] Rogov | The Nordvik section-Boreal auxiliary section for the base of the Berriasian and candidate section for the SSSP of the Ryazanian Stage[END_REF] (see also Fig. 10). According to these authors, the C. On the Russian platform, the upper 'Volgian' includes the Kachpurites fulgens, Garniericeras catenulatum, and Craspedites nodiger zones, which have been tentatively correlated to the M20n.1n to the mid-M18r (Rogov, 2014) (Fig. 10).

Above, the palaeomagnetic calibration of the 'Ryazanian' ammonite zones -Hectoroceras kochi, Riasanites rjasanensis, Surites spasskensis, and Surites tzikwinianus zones (Mitta, 2017) remains unknown. As the 'Ryazanian' sedimentation is considered continuous although strongly condensed, a highest lower Berriasian to upper Berriasian can be provisionally assigned to the Hectoroceras kochi and Riasanites rjasanensis zones (Fig. 10). The lack of constraining microfossil and palaeomagnetic evidence in Russia prevents any precise correlation between such boreal basins and oceanic Tethys. As a result, and pending new investigation, current correlations of the 'Ryazanian' type deposits with the Mediterranean sections should be cited with caution.

Conclusions

Our systematic re-assessment suggests an overlooked diversity in ammonite assemblages from the Russian Platform during the Berriasian, here reflected by the introduction of the Riasanitidae n. fam. Although its origin remains unclear, the Specimen PIN 3390/290 of Riasanites swistowianus (Nikitin, 1888) (Mitta, 2011b, pl. 6, fig. 8a, b). (C) Specimen PIN 3390/286 of Riasanites swistowianus (Nikitin, 1888) (Mitta, 2011b, pl. 6, fig. 5). (D, E) Specimen PIN 3990/275 of Riasanites rjasanensis (Nikitin, 1888) (Mitta, 2011b, pl. 5, fig. 4a, b). (F, G) Specimen PIN 3390/291 of Riasanites swistowianus (Nikitin, 1888) (Mitta, 2011b, pl. 6, fig. 10a, b). (H, I) Specimen PIN 3990/264 of Riasanella rausingi Mitta, 2011b(Mitta, 2011b, pl. 2, fig. 4a, b), holotype. (J, K) Specimen PIN 3990/352 of Riasanella rausingi Mitta, 2011b(Mitta, 2011b, pl. 2, fig. 6a, b), paratype. Scale bar is 10 mm. [START_REF] Sazonova | Ammonites of the Jurassic-Cretaceous Boundary Beds of Russian Platform[END_REF](Sazonova, 1977, pl. 19, fig. 3), holotype. (C-E) Specimen VSEGEI 124/10223 of P. vnigni [START_REF] Sazonova | Ammonites of the Jurassic-Cretaceous Boundary Beds of Russian Platform[END_REF](Sazonova, 1977, pl. 20, fig. 4a, b), holotype. (F, G) Specimen PIN 3990/260 of P. rulevae (Mitta, 2007a) (Mitta, 2007a, pl. 3, fig. 6a, b), holotype. (H) Specimen PIN 3990/402 of P. rulevae (Mitta, 2007a) (previously assigned to Riasanites aff. maikopensis [START_REF] Grigorieva | Lower Valanginian ammonite fauna from the Belaya River basin on the northern slope of the Caucasus Mountains (Maikop area)[END_REF] in Mitta, 2011b, text-fig. 3a, b). Mitta, 2011a(PIN 3990/373, Mitta, 2011a, pl. 5, fig. 4). (C-E) The holotype of M. ceccai (Mitta, 2011a) (PIN 3990/386, Mitta, 2011a, pl. 6, fig. 1a-c). Mitta, 2018 (pl. 4, fig. 2a, b) re-assigned to M. micheicus (Bogoslovsky).

Table 1. Measurements of Riasanites and Riasanella relatives used in the text (after [START_REF] Grigorieva | Lower Valanginian ammonite fauna from the Belaya River basin on the northern slope of the Caucasus Mountains (Maikop area)[END_REF][START_REF] Khimchiashvili | Tithonian and Berriasian Ammonites of the Caucasus[END_REF][START_REF] Sazonova | Ammonites of the Jurassic-Cretaceous Boundary Beds of Russian Platform[END_REF]Mitta, 2008Mitta, , 2011aMitta, , 2018)).

Acronyms indicate D = diameter, Ww = whorl breadth, Wh = whorl height, U = umbilical diameter, U/D = ratio of umbilical dimension as a percentage of the adult diameter, and Ww/Wh = ratio of whorl breath as a percentage of the whorl height; and Bcoeff = branching coefficient as defined by Mitta (2008).

Table 2. Comparative systematic treatment of the ammonite taxa of supposed Tethyan affinity from the the type 'Ryazanian' between Mitta (2002Mitta ( , 2005Mitta ( , 2007aMitta ( , 2008[START_REF] Mitta | Ammonites of Tethyan origin from the Ryazanian of the Russian platform: genus Subalpinites Mazenot[END_REF]Mitta ( , 2011aMitta ( , 2011bMitta ( , 2017Mitta ( , 2018)), [START_REF] Mitta | Subdivision of the Ryazanian Stage of Russian platform[END_REF], [START_REF] Mitta | Ammonite distribution across the Jurassic-Cretaceous boundary in Central Russia[END_REF], and this work.

'

  Ryazanian' ammonites. Repository abbreviations mentioned in the text indicate the Faculté des Sciences de Lyon of the Claude Bernard-Lyon I University (FSL), the Dolomieu Institute of the Grenoble-Alpes University (UJF-ID), the Muséum National d'Histoire Naturelle of Paris (MNHN), and the Muséum d'Histoire Naturelle de Genève (MHNG). The ammonites from the type 'Ryazanian' have been re-examined based on illustrations and shared photographs. Unless otherwise mentioned, the revised specimens are deposited in the Palaeontological Institute of the Russian Academy of Sciences (PIN), the Central Scientific Geological Museum (CNIGR Museum, Saint Petersburg), and the All-Russia Geological Oil Research Institute (VNIGNI). Some specimens labelled AVS are housed in the private collection of Andrey Stupachenko (Mitta, 2011a, 2011b). The reader can refer to the papers listed above for further details on the sampling localities and stratigraphic occurrences of the specimens. Other repository abbreviations mentioned in the text indicate the A.P. Karpinsky Russian Geological Research Institute of Saint Petersburg (VSEGEI) and the Museum of the Department of Geology and Paleontology (MDGP) from the I. Javakhishvili Tbilisi State University. The following abbreviations indicate standard measurements used in the text: D = diameter, Ww = whorl breadth, Wh = whorl height, U = umbilical diameter. The ratios U/D, Wh/D and Ww/D (umbilical dimension, whorl height and whorl breath as a percentage of the adult diameter), and Ww/Wh (whorl breath as a percentage of the whorl height), are discussed in systematic descriptions. According to

  fig.7a, b (= ?Tauricoceras maikopensis).1989 Riasanites rjasanensis (Nikitin) -Marek et al., p. 85, pl. 41, fig. 2 (= Marek, 1967, pl. 2, fig. 1).1996 Riasanites rjasanensis (Lahusen) -Wright et al., p. 50, fig. 37.3a, b (= Nikitin, 1888, pl. 1, fig. 1). non 1998 Riasanites rjasanensis p. 93, pl. 21, fig. 6a, b (= Perisphinctoidea gen. et sp. indet.).

  3a-е (= Nikitin, 1888, pl. 1, fig. 5), 4a, b. non 1999 Riasanites rjasanensis (Nikitin) -Sey and Kalacheva, pl. 1, figs. 1, 2a, b; pl. 3, fig. 1 (= Tauricoceras maikopensis). non 1999 Riasanites subrjasanensis (Nikitin) -Sey and Kalacheva, pl. 1, fig. 3; pl. 3, figs. 2a, b, 3a, b (= Tauricoceras maikopensis). non 1999 Riasanites swistowianus (Nikitin) -Sey and Kalacheva, pl. 3, fig. 4 (= Tauricoceras sp. juv.).non 2000 Riasanites rjasanensis (Nikitin) -Kalacheva and Sey, p. 96, pl. 12, figs. 2a, b, 3, 4a, b (= Sey and Kalacheva, 1999, pl. 3, fig. 1); pl. 13, fig. 1a, b; pl. 22, fig. 2 (= Tauricoceras maikopensis).

  4. ? 2015 Riasanites sp. -Rogov et al., pl. 7, fig. 5. ? 2015 Riasanites cf. rjasanensis (Nikitin) -Rogov et al., pl. 7, fig. 4. ? 2015 Riasanites cf. swistowianus (Nikitin) -Rogov et al., pl. 7, fig. 9. non 2016 Riasanites cf. swistowianus (Nikitin) -Vašíček and Skupien, fig. 7B, C. 2018 Riasanites rjasanensis (Nikitin) morph β -Mitta, pl. 5, fig. 5.

Content:

  Riasanella rausingi Mitta, 2011b. Riasanella rausingi Mitta, 2011b emend. herein (Fig. 2H-K) 2007a Himalayitidae gen. et sp. nov. -Mitta, pl. 2, fig. 3.2011b Riasanella olorizi p. 20,

  , pl. 2, figs. 1a, b, 2a-c, 3a, b, 4a, b (= Mitta, 2007a, pl. 2, fig. 3), 5, 6a, b, 7a, b, 8a, b, 9, 10a-c, 11a, b. 2011b Riasanella riasanitoides -Mitta, p. 20, text-fig.2a, b, c-e. non 2016 Riasanella cf. rausingi p. 22, fig. 7A (= Perisphinctoidea gen. et sp. indet.).

  . non 1964 Berriasella (Protacanthodiscus) aff. micheicus (Bogoslovsky) -Jeletzky, pl. 2, fig. 11a-c (= Perisphinctoidea gen. et sp. indet.). non 1965 Berriasella (Protacanthodiscus) aff. micheicus (Bogoslovsky) -Jeletzky, pl. 11, fig. 4A, C, D (=

  , we are reluctant to consider H. micheicus as a Transcaspiites representative. The general features of H. micheicus share more similarities with those of Mittaites n. gen. ceccai and Mittaites n. gen. robustum. It is tempting to consider H. micheicus as a derivative of M. robustum by modification of the juvenile whorl shape which affected the robustness of the tuberculation mostly during the sub-adult stage. Pending further investigation, H. micheicus is retained as a senior subjective synonym of T. tscheffkini and referred to Mittaites n. gen.

:

  The genus Karasyazites was recently introduced by Mitta (2018) based on Subalpinites bajarunasi from the Mangyshlak Peninsula. The holotype VSEGEI 11104/9a and paratype VSEGEI 11104/9b of S. bajarunasi selected in Luppov et al. (1998) are herein re-illustrated in Fig. 8A-C and Fig. 8D, E, respectively. Mitta (2018) referred two specimens (PIN 3990/418 and AC 1112) from the Russia platform to the Luppov's taxon.

  assigned three specimens to the Mediterranean Himalayitidae Dalmasiceras, namely Dalmasiceras ex gr. djanelidzei (PIN 3900/249 -Fig. 9D, E), D. crassicostatum (PIN 3900/247 -Fig. 9F, G) and D.? sp. (PIN 3990/266). None of them can be accommodated into the Dalmasiceratinae as understood by

  fig. 7; pl. 15, fig. 1. ? 2007a Malbosiceras cf. macphersoni (Kilian) -Mitta, pl. 2, fig. 6. ? 2018 Karasyazites bajarunasi (Luppov in Luppov et al.) -Mitta, p. 251, pl. 4, fig. 3a, b.

taimyrensis

  Zone and the overlying Chetaites chetae Zone, which terminates the 'Volgian', encompass the mid-M19r to upper-M18n magnetic zones. The overlying Chetaites sibiricus Zonewhich starts the 'Ryazanian'mostly correlates to the M17 to mid-M16r magnetic zones. The base of the overlying Hectoroceras kochi Zone is placed in M16r. Comparing the ammonite scale of the Arctic, the Craspedites taimyrensis Zone to lower Chetaites sibiricus Zone span the highest upper Tithonian and lower Berriasian in the Mediterranean region while the upper Chetaites sibiricus Zone to lower Hectoroceras kochi Zone span the middle Berriasian to lowest upper Berriasian (see Fig. 10).

  Gechiceras-Tauricoceras lineage may have given way to the Riasanella-Riasanites plexus which spreads throughout the European part of the Boreal Atlantic Subrealm (Polish Lowland and Russian Platform) during the Rjasanites rjasanensis Zone. The Riasanella-Riasanites plexus represents the basal rootstock from which other riasanitid genera derived, i.e., Prorjasanites, Mittaites n. gen. Only the origin of Karasyazites remains in doubt. We hope that the present contribution will stimulate renewed discussion and investigation of the systematics and phyletic relationships of ammonites from the boreal regions.

Figure captions Fig. 1 .

 captions1 Figure captions

Fig. 3 .

 3 Fig. 3. Morphological relationships between the U/D and Ww/Wh ratios (common yaxis) during ontogenesis of the Riasanites species (data fromMitta, 2011b and[START_REF] Sazonova | Ammonites of the Jurassic-Cretaceous Boundary Beds of Russian Platform[END_REF].

Fig. 4 .

 4 Fig. 4. Morphological relationships between the U/D and Ww/Wh ratios (common yaxis) during ontogenesis of the Riasanella species (data from Mitta, 2011b).

Fig. 5 .

 5 Fig. 5. Re-illustration of Prorjasanites relatives. (A, B) Specimen VSEGEI 113/10223 of P. plumatus[START_REF] Sazonova | Ammonites of the Jurassic-Cretaceous Boundary Beds of Russian Platform[END_REF] (Sazonova, 1977, pl. 19, fig. 3), holotype. (C-E)

Fig. 6 .

 6 Fig. 6. Re-illustration of Malbosiceras relatives from the type 'Ryazanian' here reassigned to Mittaites n. gen. (A, B) The holotype of M. robustum Mitta, 2011a (PIN

Fig. 7 .

 7 Fig. 7. Comparison between Mittaites micheicus, Transcaspiites tscheffkini, and Transcaspiites transcaspius. (A-C) The holotype of M. micheicus (Bogoslovsky, 1897) (VSEGEI 63-62/623) here re-assigned to Mittaites n. gen. (D-G) Specimen PIN 3990/255 (including its isolated inner whorls in (D, E)) of Transcaspiites tscheffkiniMitta, 2018 (pl. 4, fig. 2a, b) re-assigned to M. micheicus(Bogoslovsky).

  also suggested that Riasanites may have derived from the Himalayitidae through Pratumidiscus Bulot et al., 2014 (type species: Pratumidiscus elsae

Acknowledgements

We wish to express our warmest thanks to Emmanuel Robert (Claude Bernard-Lyon I University), Fabienne Giraud (Grenoble-Alpes Université), Isabelle Rouget and Philippe Loubry (UPMC/MNHN, Paris), and Christian Meister (MHN, Genève) who allowed us access to the collections in their care and Aleksey Sokolov (A.P.

Karpinsky Russian Geological

Research Institute) for sharing photographs of the Bogoslovsky's material. Yi-Chun Zhang, associate editor of Palaeoworld, Rafel Matamales-Andreu (Universitat Autònoma de Barcelona), and an anonymous reviewer greatly improved the original version of the manuscript by their insightful comments on the ammonite systematic. One of us (A.P.) has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 838373.

(H-J) The holotype of Transcaspiites transcaspius [START_REF] Luppov | Klass Cephalopoda. Golovonogie (Class Cephalopoda)[END_REF]) (VSEGEI 10/6801). [START_REF] Wimbledon | Developments with fixing a Tithonian/Berriasian (J/K) boundary[END_REF][START_REF] Wimbledon | Fixing a J/K boundary: A comparative account of key Tithonian-Berriasian profiles in the departments of Drôme and Hautes-Alpes, France[END_REF] with the following acronyms: Micrac. -Microcanthum, An. -Andreaei, Occitanic. -Occitanica, Boiss. -Boissieri; Artic ammonite zonation [START_REF] Schnabl | A review of magnetostratigraphic results from the Tithonian-Berriasian of Nordvik (Siberia) and possible biostratigraphic constraints[END_REF][START_REF] Rogov | The Nordvik section-Boreal auxiliary section for the base of the Berriasian and candidate section for the SSSP of the Ryazanian Stage[END_REF] with the following acronyms: Oken. -Okensis, Taimyren. -Taimyrensis; and the Russian platform ammonite zonation [START_REF] Rogov | Infrazonal subdivision of the Volgian Stage in its type area using ammonites and correlation of the Volgian and Tithonian Stages[END_REF]Mitta, 2017) with the following acronyms: Ful. -Fulgens, Cat. -Catenulatum. Note that the calibration of upper 'Volgian' and lower 'Ryazanian' ammonite zones by palaeomagnetostratigraphy is purely speculative.


Caroline Papeix
email: caroline.papeix@aphp.fr

Elisabeth Maillart

Sandra Vukusic

A comparative evaluation of different NeuroMyelitis Optica Spectrum Disorder sets criteria

Keywords: Neuromyelitis optica, Multiple sclerosis, criteria

Background Three different sets of criteria have been proposed for the diagnosis of neuromyelitis optica spectrum disorders (NMOSD). OBJECTIVE To compare the speci city, sensitivity and diagnostic accuracy of the three different sets of NMOSD criteria, in patients presenting with in ammatory disorders of the central nervous system suggestive of NMOSD. Methods From 236 suspected NMOSD referred for serum AQP4-IgG testing between 2012 and 2014, the three sets of NMOSD criteria (1999, 2006 NMO criteria and 2015 International Panel for NMO Diagnosis criteria) were applied and compared to the nal diagnosis.

Results Seventy-six patients ful lled at least one set of criteria and 28 patients ful lled all NMOSD set of criteria. The nal diagnosis was NMOSD in 66 cases, MS according to the MacDonald 2010 in 85 cases and another diagnosis in 85 cases. 2006 NMO criteria has the highest speci city (99%) and 2015 IPND NMOSD criteria, the highest sensitivity (97%). For the 1999, 2006 and 2015 IPND NMOSD criteria, the accuracy was respectively 82%, 87% and 97%. Conclusions Our study highlights the limitations of the rst set of criteria, that include optico-spinal form of MS. The accuracy of NMO/SD diagnostic criteria improved from 1999 to 2015. It con rms the increased performance of the last set of criteria which covers a larger spectrum of clinical presentation. This study raises some the concern to classify patients with seronegative transverse myelitis or optic neuritis, and MOG-antibody associated disease.

Introduction

Since 1999, three different sets of diagnostic criteria have been proposed, mainly to distinguish NMO from multiple sclerosis (MS) and other CNS in ammatory disorders. Initially, NMO diagnosis was based essentially on a probabilistic combination of clinical signs, brain or spinal cord MRI and CSF analysis. [START_REF] Wingerchuk | The clinical course of neuromyelitis optica (Devic's syndrome)[END_REF] The identi cation of aquaporin-4 immunoglobulin G antibody (AQP4-IgG) [START_REF] Lennon | A serum autoantibody marker of neuromyelitis optica: distinction from multiple sclerosis[END_REF] led to redesign diagnostic criteria in 2006. [START_REF] Wingerchuk | Revised diagnostic criteria for neuromyelitis optica[END_REF] In 2015, the International Panel for NMO Diagnosis (IPND) revised the diagnostic criteria for NMO/SD [START_REF] Wingerchuk | International consensus diagnostic criteria for neuromyelitis optica spectrum disorders[END_REF] , taking into account the broadening clinical spectrum. This new set of criteria allowed an earlier diagnosis by the inclusion of positive AQP4-IgG (AQP4-IgG +) clinically limited forms, and patients with lesions outside the optic nerve and the spinal cord. Analysis of the impact of IPND criteria showed a dramatic increase of the diagnostic yield, in comparison to 2006 [START_REF] Hamid | The impact of 2015 neuromyelitis optica spectrum disorders criteria on diagnostic rates[END_REF][6][START_REF] Hyun | Evaluation of the 2015 diagnostic criteria for neuromyelitis optica spectrum disorder[END_REF] , concerning both in AQP4-IgG + and seronegative patients. No direct comparison between the 3 sets of criteria has been performed to date, and studies evaluating the impact of the 2015 IPND criteria, were not designed to assess speci city. Here we compared the diagnostic accuracy and speci city of the 3 sets of NMOSD criteria.

Methods

Study objective:

The main objective of this observational retrospective study was to compare the diagnostic value of 3 different sets of NMOSD criteria, as indexed by speci city, sensitivity, and accuracy in patients with clinical symptoms suggestive of NMOSD.

Study Population

We evaluated the data of 756 patients (from Lyon, Paris, Strasbourg) referred to the Lyon lab for serum AQP4-IgG testing because of central nervous system in ammatory disorders suspected of being NMOSD (called NMO until 2007) by the treating clinician, between 2012 and 2014. Medical records were available for 520 patients. Incomplete les were excluded from the analysis. Finally, we evaluate 236 les for which all the clinical, imaging and biological information necessary to evaluate the 3 sets of NMOSD criteria were available. For each patients, the presence of the following core clinical characteristics was determined: optic neuritis, myelitis, area postrema syndrome, brainstem syndrome, diencephalic and encephalic syndrome. Brain, spinal cord and orbital MRI were reviewed when available, as well as cerebrospinal uid (CSF) analyses. All samples were tested for AQP4-IgG using the same technique based on live cell-based assay. When available, MOG-IgG serostatus was collected. 8 Data collection:

Clinical, imaging and biological data were collected center by center in 2017 and reviewed by 3 neurologists, expert in NMOSD, from the three participating referral centers. The treating neurologist was de ned as the neurologist of the center evaluated and the two evaluating neurologists were de ned as external neurologist at the evaluated center.

Blind to the diagnosis proposed by the treating neurologist, the two evaluating neurologists applied retrospectively the 1999, 2006 NMO criteria and 2015 IPND NMOSD criteria [START_REF] Wingerchuk | The clinical course of neuromyelitis optica (Devic's syndrome)[END_REF][START_REF] Wingerchuk | Revised diagnostic criteria for neuromyelitis optica[END_REF][START_REF] Wingerchuk | International consensus diagnostic criteria for neuromyelitis optica spectrum disorders[END_REF] . The nal diagnosis was based in 2017, on the conclusion of the treating neurologist.

Statistical analysis:

Statistical analyses were performed with R software (3.6.0 version). The performance of NMOSD criteria with regard to clinical diagnosis was expressed as sensitivity, speci city, positive predictive value, negative predictive value and accuracy.

Ethical concern

According to the French legislation regarding observational studies, patients were informed of the study, but did not have to provide a formal and written informed consent to have their anonymized data collected. Data con dentiality and safety were ensured in keeping with the recommendations of the French Commission Nationale Informatique et Libertés, which also provided approval.

Results

The clinical, imaging, CSF characteristics and AQP4-IgG sero-status of the 236 les analyzed are detailed in Table 1. The nal diagnosis was NMOSD in 66 cases, MS in 85 cases. Another diagnosis was made for the 85 other cases (Table 2).

Among the 236 les analyzed, 76 patients ful lled at least one set of NMOSD criteria: 37, 38 and 70 respectively for the 1999, 2006 and 2015 NMOSD criteria. Forty-seven patients ful lled only one set of criteria: 7, 10 and 30 respectively for the 1999, 2006 and 2015 NMOSD criteria. Twenty-eight patients ful lled all NMOSD criteria (Fig. 1).

Comparison between 1999 and 2006 NMOSD criteria

Twenty-eight patients ful lled both the 1999 and 2006 NMOSD criteria. Nineteen ful lled at least one of 1999 or 2006 NMOSD criteria.

Ten patients ful lled the 2006 but not the 1999 NMOSD criteria. They had clinical signs outside of the optic nerve or spinal cord (6 in area postrema, 5 in brainstem, 1 located in diencephalon). Brain MRI showed "MS like" lesions (n = 3) "ADEM like" (n = 1), brainstem abnormalities (n = 1) and area postrema abnormalities (n = 2). Eight patients were tested positive for AQP4-IgG. The diagnosis of NMOSD was made in all of these 10 cases (Table 3).

Nine patients ful lled 1999 but not the 2006 NMOSD criteria. All patients ful lling the 1999 criteria but not the 2006 criteria met the major criteria (optic neuritis and acute myelitis and no evidence of clinical disease outside of optic neuritis and spinal cord). As supportive criteria of 1999 NMO/SD criteria, seven had a normal brain MRI, one had a longitudinal extensive transverse myelitis on spinal cord MRI and con uent bilateral subcortical and deep white matter lesions and one had severe and bilateral optic neuritis. None was tested positive for AQP4-IgG. The nal diagnosis selected was NMO (n = 4), Epstein Barr Virus transverse myelitis and optic neuritis (n = 1) and optico-spinal MS (n = 4). Among these 4 patients with a nal diagnosis of NMO, 2 ful lled also 2015 IPND criteria. The 2 patients with NMO and ful lling only 1999 criteria were tested negative for AQP4-IgG. They had bilateral optic neuritis with visual acuity worse than 20/200 (= 2 minor supportive 1999 criteria) and short myelitis without other symptoms. ). Four cases had also a brainstem (n = 3) or area postrema (n = 4) syndrome. All limited forms were tested positive for AQP4-IgG. Five of the seven patients with negative AQP4-IgG had at least clinical and radiological area postrema and /or brainstem syndrome. In one case the MRI lesion extended from cervical cord to area postrema (Fig. 2A, patient 52) and in one other case tumefactive brain lesion was observed in addition to brainstem lesion. (Fig. 2B and 2C patient 48). Among these 30 patients, ve (16.6%) had a nal diagnosis other than NMOSD. One had extended brain lesion and LETM with a nal diagnosis of endovascular lymphoma (Fig. 3). Two patients were considered as MS ful lling MacDonald 2010 criteria. One patient tested positive for AQP4 with extensive myelitis had a glioma of the spinal cord. Another patient tested positive for AQP4-IgG with optic neuritis was diagnosed as paraneoplastic syndrome. The remaining 25 patients had a nal diagnosis of NMOSD, 22 of who were positive for AQP4-IgG.

Final diagnosis

Among the 66 cases of NMO/SD, 38 were positive for AQP4-IgG and 3 for MOG-IgG (17/28 AQP4-IgG negative patients tested). The clinical, and AQP4-IgG sero-status characteristics of NMOSD patients are detailed in Fig. 4.

Among the 85 cases with a nal diagnosis of MS, 7 patients ful lled at least 1 NMOSD criteria, including onepatient ful lling the three sets of criteria. One patient with progressive MS was tested positive for AQP4-IgG.

Among the 85 cases without NMO/SD or MS diagnosis (Table 2), 6 patients with isolated myelitis were tested positive for MOG-IgG. Finally, and 34 patients still remained without diagnosis at the date of the evaluation: 16 had isolated or recurrent idiopathic optic neuritis, 15 isolated or recurrent idiopathic transverse myelitis, 1 isolated encephalitis and 2 multiple symptoms.

Value of the three different sets of NMOSD criteria

The speci city of the criteria was highest ( 99%) in 2006 NMO criteria. The speci city was similar in the rst and the last set of criteria (96% in 1999, and in 2015 IPND criteria). The sensitivity was highest ( 97%) in 2015 IPND NMOSD criteria and the accuracy signi cantly increased from the rst to the last NMOSD criteria (from 82-97%) (Table 3).

Discussion

The accuracy of the NMO sets criteria increases with the successive version of criteria with a signi cant improvement of the sensitivity from 1999 to 2015 IPND criteria while the speci city remains similar.

The results of this study emphasize the limitation of the 1999 NMO criteria. The 1999 set of criteria allowed the inclusion of optico-spinal form of MS, having therefore a low speci city. The integration of serological status for AQP4 IgG 2 in the revised 2006 criteria led to improve drastically the speci city of the NMO set criteria. 2006 criteria, allowing cases with extra optico-spinal presentation to be included, also improved the sensitivity and enlarged the spectrum of the disease.

Our study con rms the increase of diagnostic yields of 2015 IPND criteria in comparison to 2006, due to inclusion of positive AQP4-IgG patients with a limited form of the disease. The 2015 IPND criteria also

  Brain MRI ful lled Mac Donald 2010 criteria for one. Comparison between 2006 and 2015 NMOSD criteria 38 patients ful lled the 2006 and 2015 NMOSD criteria. All patients meeting the 2006 criteria also met the 2015 criteria. 30 patients met the 2015 IPND criteria but not the 2006 or 1999 NMOSD criteria. Twenty-three had a limited form of NMOSD with only optic neuritis (ON) (n = 4) or longitudinal extensive transverse myelitis (LETM) (n = 19

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Acknowledgements : Not applicable

Funding

No funding statement to declare for this work.

Availability of supporting data

Because of national con dentiality requirements, only anonymized data, not pseudonymized data, can be shared. While anonymization techniques might result in the impoverishment of data ( article 29 of Directive 95/46 /EC, Opinion 04/2014 on Anonymization Techniques -0829/14/EN WP 216) data used for this study were only pseudonymized.

result in inclusion of patients, with either positive or negative AQP4 status, presenting with non opticospinal syndrome (brain, brainstem or diencephalic lesions) in both.

The study also raises some concerns about 2015 IPND criteria with a lower speci city in comparison to 2006. Indeed, some patients ful lling 2015 IPND criteria and not 2006 NMOSD criteria had an alternative NMO/SD diagnosis. This issue concerns mainly patients with brain lesion and negative AQP4-IgG status.

Moreover, if 2015 IPND criteria are more accurate than 1999 criteria to distinguish NMOSD from MS there is still matter of concern in the patients with MS like lesions. The appearance of "MS like" brain lesions during the evolution of the disease is particularly worrying in the limited form.

Despite the fact that IPND 2015 allowed an early diagnosis, some patients with NMO related disorder, with either isolated or recurrent TM and ON but tested negative for AQP4-IgG are still not classi ed. As found in our study, some of these patients are tested positive for MOG-IgG, highlighting the current need to establish a clear de nition of MOGAD (MOG -Auto Antibody disease) and its link with NMOSD.

Declarations Ethical Approval and Consent to participate

According to the French legislation observational studies, patients were informed of the study, but did not have to provide a formal and written informed consent to have their anonymized data collected. Data con dentiality and safety were ensured in keeping with the recommendations of the French Commission Nationale Informatique et Libertés, which also provided approval.

Consent for publication : Not

Competing interest

The authors declare that they have no competing interests . No disclosure relevant to the manuscript.

Author's contributions CP, NC, RM designed and conceptualized the study, have a major role in the acquisition of data and analyzed the data and drafted the manuscript for intellectual content. YB Analyzed data; revised the manuscript for intellectual content. All authors listed have revised the manuscript for intellectual contribution to the work. All authors read and approved the nal draft for publication.