Patterns of the Evolution of Aptychi of Middle Jurassic to Early Cretaceous Boreal Ammonites

Swiss J Palaeontol DOI 10.1007/s13358-015-0110-1

Patterns of the evolution of aptychi of Middle Jurassic to Early Cretaceous Boreal ammonites

1 1 Mikhail A. Rogov • Aleksandr A. Mironenko

Received: 27 March 2015 / Accepted: 1 November 2015 Ó Akademie der Naturwissenschaften Schweiz (SCNAT) 2015

Abstract Here we are providing a review of aptychi Stephanoceratoidea and Perisphinctoidea have aptychi records in ammonites of Boreal origin or that inhabited significantly smaller than the aperture diameter. Boreal/Subboreal basins during the Bathonian–Albian with special focus on new records and the relationship between Keywords Aptychi Á Jurassic Á Cretaceous Á Ammonites Á the evolution of ammonite conch and aptychi. For the first Evolution time we figure aptychi that belong to Aulacostephanidae, Virgatitidae, Deshayesitidae, Craspeditinae and Laugeiti- nae. A strong difference between aptychi of micro- and Introduction macroconchs of co-occurring Aspidoceratidae is shown, which, along with their shell morphologies suggests niche Aptychi are organic (in some cases with calcite layers of divergence of these dimorphs. Aptychi of Aptian Sinzovia variable thickness) and usually bivalved plates, associ- (Aconeceratidae) should be tentatively ascribed to Diday- ated with ammonites and considered as parts of the lower ilamellaptychus, while their previous assignment to rhyn- jaws albeit other functions are also widely discussed chaptychi was caused by misidentification. Aptychi of (Parent et al. 2014). During the nearly 200-year history Middle Jurassic–Early Cretaceous Boreal and Subboreal of aptychi research, a great number of formal species and ammonites are characterized by a very thin calcareous non- genera have been described. However, only uncommon porous outer layer lacking distinct ribs and tubercles (only records of aptychi were mentioned from the Boreal radial striae sometimes occur), and mainly should be Middle Jurassic to Early Cretaceous (e.g. Blake 1875; assigned to Praestriaptychus. Some ammonoid groups (i.e. Weerth 1884), and aptychi of many ammonite groups Ancylocerina and Desmoceratoidea) are characterized by (especially of those with Boreal and Subboreal affinities) the presence of different aptychi types irrespective of their remain unknown until now. Significant progress in the shell shape. This fact could indicate that bivalved praes- study of Boreal aptychi has been achieved over the last triaptychi could have easily transformed into single-valved decades in which numerous aptychi (including in situ ‘‘anaptychi’’ and vice versa. Size and form of aptychi in findings in ammonoid body chambers) were described relation to those of the aperture of ammonite conchs vary and/or figured (cf. Etches and Clarke 1999; Engeser and within different lineages and at least some Keupp 2002; Rogov and Gulyaev 2003; Rogov 2004a, b; Mitta and Keupp 2004; Keupp and Mitta 2013; Miro- nenko 2014). Aptychi–ammonite conch associations sometimes are used for reconstructing ammonite evolu- & Mikhail A. Rogov tion (Trauth 1927; Engeser and Keupp 2002). However, [email protected] aptychi records are still significantly incomplete, and the Aleksandr A. Mironenko ammonite phylogenetic tree based on aptychi distribution [email protected] contradicts some aspects of phylogenies based on other 1 Geological Institute of RAS, Pyzhevski Lane 7, Moscow, features, especially the sutural development (Rogov Russia 119017 2004a, b). M. A. Rogov, A. A. Mironenko

Material correlation with international Tithonian and Berriasian stages remains unclear. In this study, we focus on little-known aptychi from Boreal Studied specimens are stored in the Moscow State and Subboreal areas (Fig. 1). Most of the studied speci- University Museum (MSU) and Vernadsky State Geolog- mens have been collected by the authors, and some spec- ical Museum of the Russian Academy of Sciences (SGM), imens or photos of aptychi were transferred to us by both in Moscow, Russia, with exception of those specimens colleagues. Studied aptychi were discovered within the which are available as photos thanks to the help of our body chambers of ammonites or ascribed to particular colleagues; the latter specimens are kept in the University ammonite groups due to their co-occurrences. As ammo- of Oslo (PMO, Norway), Cambridge Arctic Shelf Pro- nite diversity is relatively low in many stratigraphic levels gramme (CASP, Cambridge, UK) and Museum of Jurassic of the Boreal Jurassic (in many cases 1–2 genera belonging Marine Life (K, Kimmeridge, UK). to 1–2 families), such co-occurrences could help signiﬁ- cantly even when aptychi are found separately from the conchs of the corresponding ammonite. In some cases (for Review and description of new aptychi records example, in suspected Middle Volgian virgatitid aptychi), a cross sections of ammonites versus aptychi relative length Stephanoceratoidea was also used to infer ammonite–aptychi relationships. In addition to newly collected material, we are also reviewing Cardioceratidae some recent records of aptychi in Boreal and Subboreal ammonites. Both in situ records of cardioceratid aptychi and their Systematics of higher ammonite taxa used herein is isolated occurrences are only known from the Lower based on Besnosov and Michailova (1991) with some Callovian of the European part of Russia (Mitta and Keupp additions from Kvantaliani et al. (1999) and Shevyrev 2004), while Late Callovian aptychi, which belong to (2006). As aptychi usually occurred outside the host conchs Quenstedtoceras, are also known from northern Poland and their relation to ammonoid taxa are unclear, generic (Lehmann 1972; Dzik 1986). Surprisingly, mass occur- and species names used for aptychi are separate from those rences of cardioceratids, which sometimes crowded the of ammonoid shells and treated as parataxa (Engeser and bedding planes in the Upper Oxfordian or Upper Kim- Keupp 2002). A brief description of major aptychi types is meridgian black shales are lacking cardioceratid aptychi, given by Engeser and Keupp (2002). albeit the Upper Oxfordian shales of the Kostroma region For the stages around the Jurassic/Cretaceous boundary, yielded perisphinctid aptychi. Taking reported uncalciﬁed we are using the Volgian and Ryazanian as preferred cephalopod jaws into account, which co-occur with names, because these stages could be easily used for all numerous cardioceratids described by Dzik (1986) from the Boreal regions (cf. Rogov and Zakharov 2009), while their Upper Callovian of Poland and the absence of a calcitic

Fig. 1 Map showing aptychi-bearing sites, specimens from which are Gorodischi, Ulianovsk, 10 Kashpir, Marievka, 11 Shirokij buerak, 12 figured or discussed. 1 Kuhn Island, 2 Janusfjellet Mt, Vasstak Elva, Kelevudagh Mt, 13 Veselovskaya 5 well, 14 Nordvik, 15 Cape Cape Festningen, 3 Sorkappland, 4 Kimmeridge Bay, 5 Eganovo, Hajryuzova Rybaki, 6 Ivanovskoe, Glebovo, 7 Mikhalenino, 8 Hvadukassy, 9 Patterns of the evolution of aptychi of Middle Jurassic to Early Cretaceous Boreal ammonites layer in the Early Callovian ones, cardioceratid aptychi conch (Keupp and Mitta 2013, Fig. 13e). Similar aptychi could have been fully organic and their absence might be were also found within the body chamber of the Late primarily taphonomic in the Upper Jurassic. The shape of Bathonian Homoeoplanulites from NE Iran (Seyed-Emami cardioceratid aptychi allows them to be described as and Schairer 2011, Fig. 3B). A poorly preserved Praes- Praestriaptychus Trauth, 1927. triaptychus was also discovered associated with Elatmites (Grossouvriinae, Keupp and Mitta 2013, Fig. 21). Upper Kosmoceratidae Oxfordian clays and black shales, intensively studied in the Kostroma region of European Russia during the last decade Numerous occurrences of kosmoceratid aptychi have (Glowniak et al. 2010; Tesakova et al. 2012), are also become known since recently. Schweigert (2000) described known as a source of the suspected perisphinctid aptychi. an in situ record of Kosmogranulaptychus Rogov, 2004a Praestriaptychus was usually found in black shales as (originally referred by Schweigert to Granulaptychus isolated plates (Fig. 3f), but in situ findings are also known. Trauth, 1927) within the body chamber of Late Callovian The in situ occurrence of relatively small-sized Praestri- Kosmoceras. A few years later, the suggested kosmoceratid aptychus within the body chamber of Dichotomosphinctes aptychi, which were assigned to this family by co-occur- from the Upper Oxfordian Serratum Zone of Mikhalenino rence of conchs with corresponding aptychi, were descri- (Kostroma region, Fig. 2n) is the most interesting among bed from the Upper Bathonian (Mitta 2009) and Middle these records. Ataxioceratid ammonites were mainly typi- Callovian (Rogov 2004a, b) of the Russian Platform. cal for Sub-mediterranean areas, except their short-lived Finally, Keupp and Mitta (2013) described and illustrated Subboreal offshoot, separated as the subfamily Gravesiinae both isolated and well-preserved in situ aptychi of Early by Zeiss (in Fischer and Zeiss 1987). Aptychi were Callovian kosmoceratids. It should be noted that generic recorded in Early Volgian Gravesia gigas from Northern classification of kosmoceratid aptychi still remains unclear, France (Boulogne-sur-Mer, see Hahn 1963, pl. 13, Fig. 1), as in some cases, they are represented by internal moulds and isolated aptychi co-occurred with Gravesia gravesiana without any traces of a calcitic layer, thus they could be in Swabia (Scherzinger et al. 2006). These aptychi should assigned either to Kosmogranulaptychus or to Praestriap- be referred to as Praestriaptychus. tychus. However, at least some Early Callovian kosmoceratids bear praestriaptychi (Keupp and Mitta 2013, Aulacostephanidae Figs. 13–14), which can be distinguished from kosmogranulaptychi by a smooth outer calcitic layer. It stands to Aptychi of aulacostephanid ammonites were not known reason that the early kosmoceratids which bore praestri- previously (Ziegler 1962). During the field work in aptychi could have transformed into kosmogranulaptychi Sorkappland (Svalbard), our colleagues from the Polar with outer surfaces covered by granules (Keupp and Mitta Marine Geological Expedition (Lomonosov, Russia) col- 2013). Additional records of kosmoceratid aptychi, which lected some Kimmeridgian ammonites. In one of the are assigned to this ammonite family due to their occur- specimens ascribed to as Rasenia cymodoce (d’Orb.) [M], rence in concretions crowded with Kepplerites, were found there is a relatively large-sized imprint of Praestriaptychus, recently by the authors in the Upper Bathonian of Mor- characterized by well-visible wide ribs on the opposite side dovia. It should be noted that aptychi, which were recov- of the slab (Fig. 2i). Our suggestion that these aptychi are ered from the body chambers of Lower Callovian belonging to Rasenia cymodoce is based on both its size kosmoceratid macroconchs (Keupp and Mitta 2013, and shape, while other ammonites, known from the Lower Figs. 12, 15) are characterized by a significantly smaller Kimmeridgian cymodoce horizon of Svalbard are charac- size compared to the corresponding ammonite conchs. terized by a much smaller conch size compared to those of Rasenia (Rogov 2014a). Perisphinctoidea Dorsoplanitidae Perisphinctidae and Ataxioceratidae First reports on the aptychi which belong to dorsoplanitid During the last decade, findings of aptychi, which belong to ammonites were published by Blake (1875) who mentioned the Proplanulitinae, were discovered in the Lower Callo- an ‘‘Aptychus’’ from his Bed 38 of the Kimmeridge Clay of vian of European Russia (Rogov and Gulyaev 2003; Keupp the Kimmeridge area in Dorset (Lower Volgian Elegans and Mitta 2013). In situ records of praestriaptychi are only Zone, see Cope 1967) as well as a co-occurrence of Ap- known from microconchs of these ammonites (Rogov and tychus biplex (nomen dubium) with a conch of Ammonites Gulyaev 2003, Fig. 2), while large-sized aptychi, assigned biplex auct. non Sow. (species used for most Late Kim- to perisphinctid macroconchs were found apart from their meridgian [sensu anglico = Early Volgian and earliest M. A. Rogov, A. A. Mironenko Patterns of the evolution of aptychi of Middle Jurassic to Early Cretaceous Boreal ammonites b Fig. 2 Selected Upper Jurassic–Lower Cretaceous aptychi. Speci- Craspeditinae were found in the Middle–Upper Volgian of mens figured at c, i, m, o. q–s are coated with ammonium chloride. a– the Veselovskaya 5 well (Western Siberia, Fig. 2l) and the n, q, s–u Praestriaptychus spp., a K952b, Kimmeridge Bay, Middle Volgian, Pallasiodes Zone; b K477, Kimmeridge Bay, Lower Nordvik section (Northern Siberia, Fig. 2h). Isolated Volgian, Pectinatus Zone; c PMO225.170, Janusfjellet Mt, Upper Praestriaptychus (Fig. 2q) from the Middle Volgian Niki- Volgian, Okensis Zone, Originalis Subzone (refigured from Hrynie- tini Zone of the Yaroslavl region should be also assigned to wicz et al. 2015, Fig. 9D); d, f, g Marievka, Upper Volgian: d MSU Dorsoplanitidae, as other ammonites are unknown from 121/41, Catenulatum Zone, catenulatum horizon, bed M15, f MSU 121/35, Fulgens Zone, involutum horizon, bed M14, g MSU 121/42, these strata. The latter record possibly belongs to either Fulgens Zone, tenuicostatum horizon (?), beds 10–12; e MSU 121/12, Epivirgatites, Laugeites or Lomonossovella. This aptychus, Kashpur, Upper Volgian, Fulgens Zone, bed 23, subfulgens horizon: as well as a specimen from the body chamber of Dorso- h MSU 121/43, Nordvik, Middle–Upper Volgian boundary beds: planites from Svalbard shows not only concentric ribs, but i MSU 121/44, Sorkappland, Lower Kimmeridgian, Cymodoce Zone, cymodoce horizon, section 4, bed 5; j, k Kuhn Island, Middle also thin radial striae (they are visible near the transition Volgian, Groenlandicus Zone, lambecki horizon, j CASP K16185, from the lateral to frontal margin), which became common k CASP K16154; l MSU 121/20, Veselovskaya 5 well. Middle–Upper in some Cretaceous praestriaptychi. Volgian boundary beds: m SGM 1355/89, in situ record within the body chamber of Dorsoplanites sp., Vasstak Elva, Middle Volgian; n specimen in private collection of A. Stupachenko, in situ record Virgatitidae within the body chamber of Dichotomoceras sp., Mikhalenino, Upper Oxfordian, Serratum Zone; q MSU 121/27, Glebovo, Middle Volgian, Virgatitids are short-lived (latest Kimmeridgian–Middle Nikitini Zone; s SGM 1355/57, in situ record withion the body Volgian) Subboreal ammonites with a narrow geographic chamber of Laugeites lambecki (Ilov.), Festningen, Middle Volgian, Groenlandicus Zone, lambecki horizon, bed 131; t MSU 121/19, distribution (one endemic species is described from Kelevudagh Mt, Lower Hauterivian, bed 177; u SGM VH17/39, Subpolar Urals, while other taxa are restricted to the Gorodischi, Upper Kimmeridgian, Autissiodorensis Zone, Subbore- European part of Russia and Poland). Several relatively alis Subzone, subborealis horizon, bed 9/24; o, p Laevilamellaptychus narrow praestriaptychi were found together with an early sp., Rybaki, Upper Oxfordian, Serratum Zone, o MSU 121/1, imprint of the inner surface, p MSU 121/2; r imprint of the inner surface of member of this family, the Late Kimmeridgian Sarma- Laevaptychus sp., MSU2549, Hvadukassy, Upper Kimmeridgian, tisphinctes (Fig. 2u), however, some uncertainties con- Mutabilis Zone cerning the aptychi assignment remain as they were found close to—but outside of the body chambers of ammonites. It should be noted, however, that such praestriaptychi were Middle Volgian] British ammonites prior to 1913, cf. Cope also found in the Autissiodorensis Zone of the Peri-Caspian 1967, p. 5) found in bituminous shales near Fulletby depression, where ammonite assemblages consist of Sar- (Lincolnshire). These historical records were not figured or matisphinctes and lamellaptychi-bearing oppeliids. Middle described, but their assignment to dorsoplanitid ammonites Volgian praestriaptychi (P. volgensis Rogov), which are is based on the absence of other ammonite groups within characterized by even more narrow valves, were primarily the discussed strata. Typical praestriaptychi, which belong assigned to either Pavlovia or Zaraiskites (Rogov 2004a). to Pavlovia were figured by Oates (1974, pl. 10, Fig. 3) They were collected outside of ammonites, but their from the Hartwell Clay of Buckinghamshire and additional comparison with true aptychi of Pavlovia and other dor- records were made by Etches (Etches and Clarke 1999; soplanitids gave ground to the assumption that they should refigured herein, Fig. 2a) while aptychi of older dorso- be ascribed to Zaraiskites. Very similar narrow-valved planitids (Pectinatitinae: Pectinatites or Paravirgatites) praestriaptychi, which probably belong to virgatitid were discovered by Etches at Dorset (Etches and Clarke ammonites, were also found in the uppermost part of the 1999; refigured herein, Fig. 2b). In both these cases, the Lower Volgian (Fig. 3h). aptychi assignment to the conchs of particular ammonite genera was based on their co-occurrences with ammonites. Craspeditidae Few in situ aptychi of later dorsoplanitids were found in Svalbard. The Praestriaptychus, which was found in the Craspeditid aptychi have been discovered only recently in body chamber of Dorsoplanites sp., shows thin radial striae the Upper Volgian of the Middle Volga region (Rogov (Fig. 2m), whereas more typical Praestriaptychus was and Mikhailova 2006). Intensive studies of the Upper found in the body chamber of Laugeites lambecki (Ilov.) Volgian succession in the Moscow region lead to from the latest Middle Volgian (Fig. 2s). The aptychi, very numerous records of aptychi (Praestriaptychus fulgens similar to those from the body chamber of Svalbard Lau- Mironenko) and upper jaws in Kachpurites (Mironenko geites, were also found together with L. parvus Donovan of 2014). Additional occurrences of aptychi, which belong to the same age in the Kuhn Island (East Greenland) by the Garniericeratinae are also known, providing possibilities CASP expedition (Fig. 2j, k). Very similar isolated aptychi, to compare evolutionary changes of shell versus aptychi which could be assigned either to Laugeitinae or to shape. This subfamily consists of the two genera M. A. Rogov, A. A. Mironenko

Fig. 3 VEGA/Tescan SEM (a–c, f, i) and microscopic (d, e, g, h, j, d (MSU 121/3) e (MSU 121/4)—Ulianovsk, j, k in situ record within k) photographs of Upper Jurassic and Lower Cretaceous aptychi. the body chamber of Sinzovia; f–i Praestriaptychus sp., f MSU6070, Only j is coated with ammonium chloride. a–c Laevilamellaptychus Mikhalenino, Upper Oxfordian, Alternoides Zone, bed 8; g MSU sp., Rybaki, Upper Oxfordian, Serratum Zone, a specimen in private 121/5, Ulianovsk, Lower Aptian, Volgensis Zone; h Gorodishi. collection; b, c MSU 121/2, details of inner structure of aptychus; d, MSUAP137, Lower Volgian, Puschi Zone, bed 1/6; i MSU 121/6, e, j, k Didayilamellaptychus (?) sp. Lower Aptian, Volgensis Zone, Kelevudagh Mt, Lower Hauterivian, bed 177

Kachpurites and Garniericeras, which show quick ana- Aspidoceratidae s.l. genetic evolutionary changes from nearly evolute well- sculptured early Kachpurites to keeled oxyconic Gar- Although aspidoceratids are not truly Boreal ammonites niericeras (Rogov 2013, 2014b). Evolutionary changes in and they are typical for Tethyan areas, they sometimes the shape of praestriaptychi, associated with these invaded Boreal seas, in some cases reaching the Pechora ammonites (Fig. 2d–g), generally coincide with this trend, region and Subpolar Urals. Two subfamilies, included in but aptychi evolution seems more gradual (Fig. 4). Some the Aspidoceratidae (Aspidoceratinae and Peltoceratinae) praestriaptychi, collected from the lower part of the Upper are characterized by significant differences in their inner Volgian from European Russia could belong to Cras- whorls (including presence of ‘parabolic nodes’ in aspi- pedites (Craspeditinae), but to date only one record of doceratins) suggesting that the Aspidoceratidae, as con- Praestriaptychus (Hryniewicz et al. 2015, Fig. 9D, refig- ventionally recognized, is polyphyletic and two ured herein, Fig. 2c) from the upper part of the Upper subfamilies evolved from different groups of pseu- Volgian Okensis Zone should be ascribed to this genus. doperisphinctins (Page 2008). Aptychi of Late Jurassic Surprisingly, the intensive search for aptychi in the peltoceratins are unknown, but their Callovian ancestors ammonite-rich sites of the earliest Cretaceous age (Binatisphinctes) are associated with Praestriaptychus (Ryazanian and Valanginian) did not provide any addi- anglicus (Page 1991; Rogov 2004a, b). The single known tional occurrences of craspeditid aptychi, although several record of an aptychus within the body chamber of Pel- ammonoid upper jaws were discovered in the Ryazanian toceras (Frerichs 2004, Fig. 1) is preserved as an imprint of Northern Siberia (they will be described elsewhere). of the inner surface and its identification as Patterns of the evolution of aptychi of Middle Jurassic to Early Cretaceous Boreal ammonites

Zone the Late Oxfordian aspidoceratid Mirosphinctes [m] (Figs. 2o, p, 3a). Surprisingly these aptychi differ from those of associated macroconchs Euaspidoceras not only by size and shape, but also by their structure. Lae- 7 vaptychi associated with macroconchs are characterized a by a clearly visible porous structure, whereas aptychi of microconchs have a relatively homogenous calcitic layer (Fig. 3b, c) and could be classified within the paragenus Laevilamellaptychus. Published data on laevilamellaptychi microstructure (Farinacci et al. 1976, pl. 7–8) indicates 6 the presence of a tubular structure in this taxon, which was not found in our specimens. It should be noted that 5 the shape of laevilamellaptychi, which co-occurred with b Mirosphinctes is identical to those known as an imprint of the inner surface in the body chamber of Epipeltoceras 4 (cf. Enay 1962, pl. IV, Fig. 3). In contrast to Laevapty- 3 c chus, which are only associated with aspidoceratin macroconchs, Laevilamellaptychus are known in associa- 2 d Kachpurites Garniericeras tion with clearly separated ammonoid clades, such as Stephanocerina (Aspidoceratidae) and Haplocerina 1 (Haploceratidae, see Trauth 1934). It is worth noting that e the laevaptychi, which were found inside the body FULGENS CATENULATUM UPPER VOLGIAN (pars) UPPER chambers of two Late Oxfordian Euaspidoceras are significantly smaller than the apertures of these ammonites (in both recorded shells the height of aptychi is approx- Fig. 4 Changes of shell cross-section and aptychi outline within the lineage of the Late Volgian Garniericeratinae. Biohorizons are imately 80 % of the height of the aperture), whereas in marked by numerals (1 evolutum, 2 tenuicostatum, 3 cheremkhensis, brevidomic microconchs Mirosphinctes the size of aptychi 4 subfulgens, 5 involutum, 6 internicarinatum, 7 catenulatum). is nearly equal to the size of the aperture (Fig. 2o). Outline of praestriaptychi is given without scale: a aptychus of Garniericeras catenulatum (Fisch.), MSU, Ivanovskoe; b aptychus of Kachpurites involutum Rogov, in litt., MSU6503, Marievka; c apty- Simbirskitidae chus of Kachpurites subfulgens (Nik.), MSU 121/12, Kashpir; d, e aptychus of Kachpurites tenuicostatum Rogov, in litt., d MSU Aptychi of simbirskitid ammonites have been known since 121/42, Marievka; e MSU 116/5, Eganovo = Mironenko (2014, pl.II, the end of the nineteenth century when Weerth (1884) Fig. 5) depicted Aptychus inverselobati (Weerth 1884, pl. VII, Fig. 2), recovered from the body chamber of ‘‘Ol- Praestriaptychus is only preliminary. Aspidoceratins costephanus inverselobatus Neum. et Uhl.’’, presently developed very thick aptychi (Laevaptychus Trauth 1927), considered to belong to the simbirskitid genus Speeton- which clearly differ from aptychi of other ammonoid iceras (Rawson 1971). This aptychus was included by groups by their remarkable porous outer surface (Rogov Trauth (1937) in the paragenus Praestriaptychus. Addi- 2004a, b), albeit the imprints of their inner surface could tional records of simbirskitid aptychi were reported be compared with those of praestriaptychi (Fig. 2r). These recently. Engeser and Keupp (2002, Fig. 7) and Frerichs aptychi are known from nearly all levels of the Subboreal (2004, Figs. 10–12) have described Late Hauterivian Sim- Callovian and Upper Jurassic, which are characterized by birskites from Northern Germany with Praestriaptychus in aspidoceratins, i.e. from the Upper Callovian, Upper their body chambers, while some years later Baraboshkin Oxfordian, Lower and Upper Kimmeridgian and upper- and Shumilkin (2010) described aptychi of Simbirskites most Lower Volgian (Rogov 2004a, b). However, aptychi from the coeval strata of the Volga area, ascribed to the of microconchiate aspidoceratins were poorly known and new species Praestriaptychus simbirskense (Synaptychus their taxonomy remains controversial. Ziegler (1974) after Baraboshkin and Shumilkin 2010, Fig. 2). New in situ ascribed aptychi of Sutneria apora (Opp.) as Laevil- aptychi were found in the body chamber of Speetoniceras amellaptychus Trauth, 1930, while Schweigert (1998) (Fig. 5). This aptychus could be determined as Praestri- suggested that aptychi of Sutneria should be considered as aptychus inverselobatus (Weerth). It should be noted that small-sized Laevaptychus. Here, we are presenting a first the length of this aptychus slightly exceed the measured report of aptychi found in situ within the body chamber of whorl height of the ammonite (54.1 and 50.5 mm, M. A. Rogov, A. A. Mironenko

Fig. 5 Praestriaptychus inverselobatus (Weerth), MSU 121/40, Upper Hauterivian, Versicolor Zone, Ulianovsk

Fig. 6 Aptychi co-occurring with Sinzovia sasonovae Wright (left photograph made in ﬁeld, right the same specimen photographed in laboratory with well-visible inner organic black layer), MSU 121/45, Lower Aptian, Volgensis Zone, Shirokij Buerak, member 3 respectively), while the width of both valves are *1cm of the symphysis (‘‘intermediate type’’, showing transition narrower compared to whorl breadth. from anaptychus-type to the aptychus-type, see Tanabe et al. 2015) and possibly it originated not from a true Desmoceratoidea Anaptychus, but from bivalved aptychi. This hypothesis is supported by a recently described aptychus associated with Desmoceratidae the desmoceratid ammonite Grantziceras from the Lower Albian of Kamtchatka (Cape Hajryuzova, see Palechek Aptychi of Late Cretaceous desmoceratid ammonites are et al. 2005). This aptychus is represented by two clearly relatively well known (Tanabe 1983) and they consist of a isolated valves and possibly could be ascribed to as single valve (anaptychus), which, however, shows remains Praestriaptychus, while its original assignment to Patterns of the evolution of aptychi of Middle Jurassic to Early Cretaceous Boreal ammonites

Synaptychus Basse, 1953 (S.? hairyusovi Baraboshkin in Keupp 2002). However, such interpretation contradicts Palechek et al. 2005, pl. 1, Fig. 4) seems to be incorrect. known records of aptychi within or close to the body chambers of aconeceratids (Thomson 1972, Fig. 3; Ric- Hoplitoidea cardi et al. 1987, pl.11, Fig. 13; Lehmann 1995), as these aptychi show outlines and sculptures typical for lamellap- Hoplitidae tychi. Unfortunately, aconeceratid aptychi recorded from the Early Aptian concretions (Fig. 3d, e) of the Volga area Engeser and Keupp (2002) wrote that hoplitids are char- generally lack a calcitic layer due to taphonomic loss and acterized by praestriaptychi, but in support of this view the their classification is unclear. Aptychi recorded from black authors cited Trauth (1927, 1930), who used the generic shales are commonly preserved with remains of a calcitic name Hoplites for all Early Cretaceous tuberculated forms, layer (Fig. 3j, k), but also cannot be precisely determined now included in Berriasellidae, Himalayitidae, Neocomi- due to their small size. However, by analogy with lamel- tidae, Hoplitidae, Deshayesitidae and Parahoplitidae. laptychi of Antarctic aconeceratids, which are character- Among the aptychi mentioned by Trauth, there are some ized by a backward rib direction near the symphysis Early Cretaceous praestriaptychi characterized by the (Thomson 1972, Figs. 2–3) and taking into account new presence of radial striae (P. columbi: Trauth 1937, pl. 11, records (Fig. 6), these aptychi could be tentatively referred Fig. 2; P. subtriangularis: Trauth 1937, pl. 11, Figs. 3–4), to as Didayilamellaptychus Turculet, 1994. It should be but they are Neocomian in age and associated with berri- noted, however, that rib curvature in aptychi of Sinzovia is asellid and neocomitid ammonites. Similar Berriasian rather close to the earliest members of this genus (Meˇchova´ aptychi were recently described in association with berri- et al. 2010, Fig. 11A–C) or to some Thorolamellaptychus asellid ammonites from the Western Bermuda Rise (Renz (Meˇchova´ et al. 2010, Fig. 10E), and the systematic posi- 1979, pl. 1, Figs. 1, 9–10). The only record of an aptychus tion of these aptychi remains unclear. Additional records of in association with Albian hoplitids was mentioned by aptychi in the body chamber of Sinzovia supports the latter Baraboshkin (in Palechek et al. 2005, p. 89) who compared interpretation that calcification of the apex could be par- desmoceratid aptychi with those from the Middle Albian of tially caused by taphonomic processes as well as by the Moscow region. As aptychus-bearing beds of this area remains of well-calcified embryonic aptychi (Mironenko are characterized exclusively by hoplitid ammonites and Rogov 2015). It should be noted that one of the figured (Baraboshkin and Mikhailova 1987), the mentioned apty- aconeceratid aptychi has healed injuries (Fig. 3d), which chus very likely belongs to hoplitids, but its true taxonomy strongly resemble abnormalities documented in jaws of remains unclear. modern Nautilus (Kruta and Landman 2008). The same kind of healed injuries is also known in some Late Creta- Haploceratoidea ceous Scaphites (Landman et al. 2010, Fig. 13E).

Aconeceratidae Ancyloceratoidea

Aptychi, which belong to pre-Barremian Haploceratoidea Crioceratitidae are so well known, numerous and diverse in pelagic car- bonate deposits of the Tethys that the succession of these Aptychi of crioceratids were recently figured and briefly aptychi (generally called lamellaptychi, which now are described in Hauterivian Aegocrioceras and Crioceratites subdivided into a few separate genera, see Meˇchova´ et al. from Northern Germany by Engeser and Keupp (2002, 2010) are used for zonal subdivision and correlation. In Figs. 5–6) and Frerichs (2004, Figs. 6–9). All these aptychi contrast to ‘‘Neocomian’’ deposits, the Barremian is mainly are characterized by prominent radial ribs and were ascri- lacking in lamellaptychi: only few records are known from bed by Engeser and Keupp (2002) to anaptychi. It should the Upper Barremian of the Eastern Carpathians (Gra¨f and be noted, however, that these aptychi differ from typical Turculet¸ 1988) and their relation with certain ammonoid anaptychi by the presence of remains of the symphysis and groups remains unclear. Although aptychi belonging to should be further considered as a separate genus as well as Aptian aconeceratids are relatively well known, some aptychi of Late Cretaceous desmoceratids (see above). uncertainties concerning their systematic position remain. However, this is not the only type of aptychi known in Aptychi of Sinzovia from the Early Aptian of the Volga crioceratitids. In the Lower Hauterivian of Kelevudagh Mt area, studied in thin sections, showed some calcification of (Azerbaijan), early crioceratitids (Criosarasinella and their apical part (Doguzhaeva and Mutvei 1990), which led Crioceratites) were associated with Praestriaptychus to ascribing these aptychi to rhynchaptychi (Engeser and (Figs. 2t, 3j). M. A. Rogov, A. A. Mironenko

Ancyloceratidae ammonoid skeleton such as the aptychi. Evolution of the Jurassic and Cretaceous ammonoids is relatively well- Ancyloceratid ammonites are characterized by the same known presently; conclusions about phylogenies, as a rule, types of aptychi, which are known from crioceratitids. are based on a set of morphological (conch and suture Praestriaptychi were mentioned by Wright et al. (1996)as form, their changes during ontogeny), stratigraphical (ob- belonging to Ancyloceras and praestriaptychi were found servations on the step by step evolution within lineages) in the body chamber of Proaustraliceras. However, closely and biogeographical (based on biogeographic affinities of related ancyloceratids, such as Australiceras whitehousei, taxonomic units) evidences (Besnosov and Michailova are known to bear striated ‘‘anaptychi’’ resembling those of 1991; Page 2008). Our review of aptychi records in crioceratitids (Doguzhaeva and Mikhailova 2002, Fig. 1). ammonoids, which inhabited Boreal or Subboreal seas In addition to these two types of aptychi, the Early Bar- during the Middle Jurassic–Early Cretaceous, highlights remian ancyloceratid ammonite Karsteniceras has bivalve some aspects of aptychi evolution (Fig. 7): aptychi with prominent concentric ribs, which were pri- 1. Some aptychi types are restricted to certain ammonoid marily referred to the ‘‘Lamellaptychus-type’’ (Lukeneder groups (i.e. laevaptychi, which belong to Aspidocer- and Tanabe 2002). However, concentric ribs at the outer atinae), while other aptychi occurred within different surface of these aptychi are of a different type than those of lineages (praestriaptychi). In general, Boreal and true lamellaptychi: they are not tile-like, but rather look Subboreal ammonoids were characterized by bivalved like thick growth lines (Lukeneder and Tanabe 2002, aptychi with a poorly developed calcitic layer and an Figs. 5–6). Therefore, these aptychi should be assigned to a absence of prominent sculpture elements new type, intermediate between lamellaptychi and (praestriaptychi). praestriaptychi. 2. Ammonoids, which belong to the suborder Ancylo- cerina and the superfamily Desmoceratoidea show a Deshayesitoidea presence of two different types of aptychi through their evolution. This could indicate either a presence of Deshayesitidae independent lineages within these groups, which developed the same aptychi type over a long period Deshayesitids represent a group of ammonoids with irrespective to changes of shell form or easy transition monomorphic shells, which originated from heteromorph from one type of aptychi (praestriaptychi) to another heteroceratids (Mikhailova and Baraboshkin 2009). Apty- (‘‘anaptychi’’ which originated from praestriaptychi chi recorded from the body chamber of juvenile De- and are characterized by remains of the symphysis shayesites from the Early Aptian of the Middle Volga area between both parts of the valve) and vice versa. were described and figured by Doguzhaeva et al. (1995, Fig. 1). The shape of this aptychus along with additional records of isolated aptychi, possibly belonging to De- shayesites (Fig. 3g), permits its assignment to Conclusions Praestriaptychus. Aptychi occurrences in ammonites of Boreal origin or from Boreal/Subboreal basins during the Bathonian to Albian Ammonite shell evolution versus aptychi evolution: are reviewed. The bulk of the studied ammonoid groups a Boreal view have poorly sculptured Praestriaptychus, characterized by a thin calcareous layer. In the course of research on ammonoid aptychi, two gen- Aptychi of aconeceratid ammonites belong to the same eral approaches on their significance for reconstruction of type of aptychi as the ancestral haploceratid ammonites ammonoid phylogeny developed. Some scholars consid- (lamellaptychi sensu lato), while their previous assignment ered aptychi as a key for ammonoid evolution (Trauth to rhynchaptychi was caused by misidentification. 1927; Engeser and Keupp 2002), while others suggest an Differences between aptychi, which belong to micro- independent development of the similar aptychi within conchs and macroconchs of the same ammonite group, different lineages (Nagao 1932; Rogov 2004a, b). Taking were recognized for the first time. Aptychi of correspond- into account documented examples of convergent evolu- ing microconchs and macroconchs of the Aspidoceratinae tion of ammonoid shells within different lineages (Bayer should be referred to as different genera of aptychi (i.e. and McGhee 1984; Monnet et al. 2011; Rogov 2014a, b), Laevilamellaptychus and Laevaptychus). However, while one could come to the conclusion that the same evolu- laevaptychi are only known in aspidoceratins, laevilamel- tionary mode was also possible for other parts of the laptychi also occurred in some haploceratids Patterns of the evolution of aptychi of Middle Jurassic to Early Cretaceous Boreal ammonites

Suborder Age Haplocerina Stephanocerina Ancylocerina Epoch Period 100.5

Albian Hoplitoidea Deshayesitoidea Parahoplitoidea Ancyloceratoidea Parahoplitidae Aconeceratidae Haploceratoidea 126.3 Deshayesitidae

Barremian Ancyloceratidae

130.8 Heteroceratidae

Hauterivian

133.9 Simbirskitidae Desmoceratoidea Olcostephanoidea Crioceratitidae

Valanginian

139.4 Polyptychitidae

Berriasian Perisphinctoidea Ryaz. Neocomitidae s.l. (incl. Berriasellidae, Himalayitidae) 145.0 Craspeditidae Olcostephanidae

Tithonian Volgian Stephanoceratoidea 152.1 Virgatitidae Dorsoplanitidae Legend Kimmeridgian - lamellaptychi

157.3 Ataxioceratidae - praestriaptychi Late Early Perisphinctidae Aspidoceratidae - granulaptychi

JURASSIC CRETACEOUS Oxfordian Haploceratidae Aulacostephanidae Oppeliidae - anaptychi

163.5 - laevilamellaptychi - laevaptychi Callovian 166.1 Aptychi recorded outside Middle Boreal regions are marked

Bathonian Kosmoceratidae (pars) Cardioceratidae by grey pattern

Fig. 7 Aptychi distribution among the selected Middle Jurassic–Early Cretaceous ammonite lineages. Ammonoid suborders and evolution of lineages are given after Besnosov and Michailova (1991), Page (2008) and Shevyrev (2006); spelling of suborder is given after Shevyrev (2006)

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