ISSN 00310301, Paleontological Journal, 2011, Vol. 45, No. 6, pp. 609–619. © Pleiades Publishing, Ltd., 2011. Original Russian Text © V.V. Mitta, 2011, published in Paleontologicheskii Zhurnal, 2011, No. 6, pp. 17–25.
Ammonites of the Genus Cadoceras (Cardioceratidae) from the Uppermost Bathonian–Lowermost Callovian of the Northern Caucasus (Ingushetia) V. V. Mitta Borissiak Paleontological Institute, Russian Academy of Sciences, Profsoyuznaya 123, Moscow, 117997 Russia email:
[email protected] Received March 5, 2011
Abstract—Based on the study of the ammonite collection assembled by A.S. Sakharov from the Middle Jurassic Armkhi Formation of the Gerchyoch Mountain Pass (northern Ingushetia) and on literature sources, the species composition and stratigraphic position of northern Caucasian Cadoceras are discussed. Early Callovian C. tchegemicum Lominadze, C. tschernyschewi Sokolov, and C. suevicum Callomon et Dietl are identified; the name C. loginovae Lominadze, 2004 is synonymized under C. stupachenkoi Mitta, 1998. The Late Bathonian species are identified as C. sakharovi sp. nov. and C. aff. perrarum Voronetz. The presence of Upper Bathonian sediments is substantiated for the northern Caucasus; the theory of the inversion of the Kepplerites beds is shows to be erroneous. Keywords: ammonites, Cadoceras, Bathonian Stage, Callovian Stage, northern Caucasus. DOI: 10.1134/S0031030111060116
Sakharov and Minin, 1970; Lominadze and Sakharov, 1984; and others.). In the Russian Platform, these Lower Callovian strata are in a different succession; here, from bottom to top, the following zones are rec ognized: Cadoceras elatmae, Kepplerites gowerianus, Sigaloceras calloviense. A variety of hypotheses were proposed to explain the inversion, primarily the hypothesis of the erosion and subsequent redeposi tions. This problem was included in the studies of the Jurassic of the northern Caucasus (Obyasnitelnaya zapiska …, 1973; Yura Kavkaza, 1992). Note that, in the above papers, the very existence of the marine Upper Bathonian deposits in the northern Caucasus was questioned or denied. The section of the Middle Jurassic in Mountainous Ingushetia on the Gerchyoch Mountain Pass is appar ently most important for the solution of this problem (Fig. 1). This is the locality of most of the ammonoids
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INTRODUCTION Ammonites of the genus Cadoceras Fischer, 1882 (subfamily Cadoceratinae, family Cardioceratidae) are widespread in the Upper Bathonian–Lower Call ovian of boreal and subboreal regions and together with the ammonite genus Kepplerites Neumayr et Uhlig, 1892 (subfamily Gowericeratinae of the family Kosmoceratidae) are an orthostratigraphic group for this interval across a large area of the globe. Therefore, the occurrences of Cadoceras in the northern Tethys, in the northern Caucasus have always caused interest because of the opportunity for the direct Boreal– Tethyan correlations. However, most commonly these were isolated specimens from various localities that could not provide an adequate information on the spe cies’ taxonomy or their precise stratigraphic position. Over ten years ago, A.S. Sakharov, a specialist in the Jurassic and Cretaceous biostratigraphy of the north ern Caucasus gave me a small collection of Middle Jurassic ammonites from Ingushetia, and handwrit ten notes. The preliminary results of the study of these ammonites I briefly summarized previously (Mitta, 2003, 2011). However, the bulk of the material has remained unpublished. From the 1960s, there has existed a problem of so called “inversion of Kepplerites Beds” in the Jurassic stratigraphy of the northern Caucasus. Beds with Kep plerites gowerianus and Sigaloceras calloviense that are here lie below the beds with Cadoceras elatmae are recorded here in the central and eastern zones of the region in the Armkhi Formation (Sakharov, 1965;
100 km Fig. 1. Location of the Gerchyoch Mountain Pass, Moun tainous Ingushetia.
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Fig. 2. The Bathonian–Callovian boundary section on the Gerchyoch Mountain Pass (after A.S. Sakharov, modi fied). Designations: (1) siltstone, (2) shaly clay, (3) lime stone, (4) silt clay, (5) oolites, (6) nodules.
from Sakharov’s collection, which mainly comprised various Cadoceras species. This part of the succession is briefly described below. The full description was published by Sakharov (1964). Information on this section has also been published (Matskevich and Sakharov, 1963; Sakharov and Minin, 1970). SECTION DESCRIPTION Near the path across the Gerchyoch Mountain 1
Pass, according to Sakharov from bottom to top lie (Fig. 2): (1) Clay dark gray, shaly, indistinctly thinly lami nated, fissured, with rare nodules of siderite and Mac rocephalites spp. Thickness 15 m. (2) Limestone brownish gray, bioclastic, with numerous oolites and carbonaceous plant remains, with interbeds of clayey siltstone in the upper part. Thickness 11.5 m. (3) Siltstone greenish gray, clayey, calcareous, with numerous, according to Sakharov, “Kepplerites gower ianus Sow., K. radiatus Lom. et Sakh., K. gowerianus dorsetensis Tint., Sigaloceras calloviensis Sow.”, and Macrocephalites spp. Thickness 0.3–0.4 m. (4) Clay dark gray, shaly, noncalcareous, with numerous nodules of marl and siderite. Nodules con tained a few Cadomites sp. and Macrocephalites sp., and numerous cadoceratins: Cadoceras tschegemicum 1 In
the papers published by A.S. Sakharov, there are significant discrepancies in the description of this section, dating, and fossil lists. Therefore, from here onwards, reference has been made to handwritten notes from the 1990s, edited by me.
Lominadze, C. suevicum Callomon et al., C. tscherny schewi Sokolov, C. sakharovi sp. nov., C. aff. perrarum Voronetz. Thickness 15 m. Bed 1 contains Macrocephalites spp. (these were assigned by Sakharov to various genera and species of the subfamily Macrocephalitinae); the first members of this genus were widespread in the Lower Callovian and also known from the Upper Bathonian, e.g., in southern Germany (Dietl, 1981; Schairer, 1990). I date Beds 1 and 2 as Upper Bathonian based on their position in the section (see below); according to Sakharov, this is the Lower Callovian Macrocephalites macrocephalus Zone. Sakharov dated Bed 3 as the Lower Callovian Kep plerites gowerianus Zone. The monograph on cosmocer atids of the Caucasus (Lominadze and Sakharov, 1985) from the Gerchyoch Mountain Pass contained descrip tions of Kepplerites from this interval dated as “Middle Callovian, with redeposited Early Callovian fauna.” These fossils are identified as Kepplerites (Kepplerites) keppleri (Oppel) (Lominadze and Sakharov, pl. 1, fig. 2; pl. 2, fig. 1; pl. 6, fig. 1), K. (K.) radiatus Lominadze et Sakharov (pl. 3, fig. 1), K. (Gowericeras) gowerianus dorsetensis Tintant (pl. 2, fig. 3). In addition, there are illustrations of “Sigaloceras calloviense (Sowerby)” (pl. 5, fig. 1) and “Kosmoceras pollucinum Teisseyre” (pl. 16, fig. 3). Judging from the photographs, all the ammonites listed belong to Kepplerites sensu stricto. The absence of prominent ribs in the bifurcation point in the macroconchs of North Caucasian specimens certainly indicates that they belong to Late Bathonian representatives of the genus, geochronologically older that the Early Callovian K. keppleri. Very similar Kep plerites are described from the Upper Bathonian of Bavaria (Schairer, 1990) and Middle Molga Region (Mitta, 2004; and others). Consequently, Bed 3 should be dated as the Upper Bathonian. Apparently, it is an equivalent of the upper part of the Paracadoceras keuppi Zone of the Russian Platform compatible with the Cadoceras calyx Zone of the Boreal scale (Mitta, 2005a; 2005b). Note that a thin (0.2–0.6, less com monly up to 1 m) bed of siltstone with accumulations of ammonites (or its equivalents) can be traces across a large territory of the northern Caucasus and is a marker horizon. This indicates a wide distribution of the Late Bathonian marine basin in this area. Bed 4 was dated by Sakharov as the Middle Callov ian (Upper Bathonian–Lower Callovian in my inter pretation). Detailed locality data are most frequently missing. Apparently most ammonites were collected loose. Based on the matrix (strong, dark gray, almost black limestone (siderites in Sakharov’s interpreta tion)), the shells of Cadoceras tschernyschewi (lecto type: Sokolov, 1912, pl. 1, fig. 2; Mitta, 2000, pl. 20, fig. 1) are easy to recognize. This species is distin guished from the ancestral C. elatmae (Nikitin, 1878) (neotype: Nikitin, 1881, pl. 11, fig. 21; Mitta, 2000, pl. 16, fig. 1), with which it was often identified by spe PALEONTOLOGICAL JOURNAL
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Fig. 3. Cadoceras tschegemicum Lominadze, specimen PIN, no. 5337/8: (a) lateral and (b) ventral views; Mountainous Ingushe tia, Armkhi River Basin, section near the village of Beina; Armkhi Formation, Lower Callovian; collected by A.S. Sakharov.
cialists working on the northern Caucasus, by the more inflated whorls and short umbilical ribs on the body chamber (Pl. 4, fig. 2). Sakharov’s collection contains five specimens of this species from Gerchy och; one label reads that the specimen was found near the top of Bed 4. Most likely, these are the uppermost (youngest) Cadoceras of this section, which agrees well with the species composition of other ammonites. In the Russian Platform, C. tschernyschewi characterizes the top of the Cadoceras elatmae Subzone of the Cadoceras elatmae Zone. Other ammonites are mostly represented by molds of yellowish brown more clayey rock (marl according to Sakharov); it is likely that these all come from the lower part of Bed 4 (judging from the taxonomic com position and occasional locality data). C. suevicum Callomon et Dietl, 1989 (holotype: Quenstedt, 1887, pl. 79, fig. 3; Schlegelmilch, 1985, pl. 41, fig. 12) was described from the lower zone of the Callovian of Germany. I previously questioned the species assignment of this form (Mitta, 2000); these comparatively smallsized ammonites are occasion ally found in the Russian Platform in the faunal hori zons elatmae and tschernyschewi, and differ from the index species of these two horizons mostly by the smaller size and more rapidly smoothening ornamen tation (including the umbilical ribs). However, after having reexamined the Bavarian and Schwabian ammonites housed in the Stuttgart Natural History PALEONTOLOGICAL JOURNAL
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Museum, I have to accept that these differences are sufficient for recognition of a separate species. C. suevicum is represented in Sakharov’s collection by two specimens, one of which (Pl. 4, fig. 1), according to the label, comes from the level of 2 m above the base of Bed 4. C. tschegemicum (holotype: Lominadze, 2004, pl. 1, fig. 5) was described from the Lower Callovian of the northern Caucasus, and the type series mostly comes from a section on the Gerchyoch Mountain Pass. This species is easily distinguished by its rela tively small size, weakly convex whorls with relatively high whorl cross section, and long primary ribs (Fig. 3). Sakharov’s collection contains only two spec imens of this species, one of which comes from the basin of the Armkhi River near the village of Beina, and the second is from the right bank of the Chegem River. Some workers (Kiselev and Rogov, 2007a, 2007b) considered C. tschegemicum to be a junior sub jective synonym of C. breve Blake (holotype: Blake, 1905, pl. 5, fig. 1), described from the Callovian of Dorset. The North Caucasian species is readily distin guished from the English species by more inflated whorls and long primary ribs, which reach the mid flank from the beginning of the body chamber (Fig. 3). Judging from the photographs kindly provided by K. Page (Plymouth), the whorls of C. breve are moder ately wide; primary ribs are short, branching in the first third of the flanks (at the beginning of the body cham ber; while the remaining twothirds of the body cham
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Table 1. Stratigraphy of the Bathonian–Callovian boundary beds in the Russian Platform and supposed succession of ammonite taxa in the northern Caucasus Sub stage
Russian Platform
Northern Caucasus
Zone, subzone, faunal horizon
Ammonites
Upper Bathonian
Cadoceras elatmae
Lower Callovian
Cadochamoussetia subpatruus
Chamoussetia stuckenbergi Cadochamoussetia subpatruus Cadochamoussetia surensis Cadoceras stupachenkoi
Cadoceras elatmae
Cadoceras tschernyschewi Cadoceras elatmae Cadoceras falsum
Kepplerites keppleri
Kepplerites keppleri Cadoceras bodylevskyi
Cadoceras apertum
Cadoceras apertum
Paracadoceras keuppi
Kepplerites vardekfoeftensis Kepplerites svalbardensis Paracadoceras keuppi Paracadoceras nageli
ber are weathered, and the ornament is poorly visible). It would be unreasonable to make a well identified spe cies a junior synonym of another species, known from one occurrence (for the last 100 years of intense study ing the Callovian deposits of England, no other remains of C. breve have been found) from a different geographical province, and considering the above dif ferences, such a synonymy would not be justified. The poorly preserved material from the middle reaches of the Volga River assigned by Kiselev and Rogov (2007a, 2007b) to C. breve does not allow positive identifica tion to species. Thus, the three above species of Cadoceras charac terize different intervals of the lowermost zone of the Callovian, which corresponds to the keppleri and elat mae subzones of the elatmae Zone of the Russian Plat form (Table 1). The presence in the northern Caucasus of the basal part of the subpatruus Subzone of this zone is confirmed by the occurrences of “C. loginovae” Lominadze (holotype: Lominadze, 2004, pl. 2, fig. 2) in this region; the species that, based on the shell shape and ribbing, should certainly be considered as a junior subjective synonym of C. stupachenkoi Mitta (holo type: Mitta and Satrodubtseva, 1998, pl. 3, fig. 1).
Cadoceras stupachenkoi Cadoceras tschernyschewi, Cadoceras suevicum
Cadoceras tschegemicum Cadoceras sakharovi, Cadoceras aff. perrarum Kepplerites spp. Macrocephalites spp.
Gulyaev (2005) incorrectly identified the latter species as C. tschernyschewi; however, C. stupachenkoi is readily distinguished by the narrower umbilicus of the adult shell, while the living chamber completely embraces the preceding whorl. The two remaining species from Sakharov’s collec tion are represented by specimens with well defined ribs throughout the whorl. Prominent ventral ribs on the body chamber is a characteristic feature of the ear liest (Bathonian) cadoceratins, inherited from arcto cephalins (the genus Arctocephalites is a supposed ancestor of Cadoceras) and virtually unknown in Call ovian species. Moreover, cadoceratins in the upper zone of the Boreal Bathonian (Cadoceras apertum) show smoothening of ventral ribbing on the body chamber. In later species, this character is progres sively shifted to the earlier whorls and, in the Middle Callovian, shells of the descendants of Cadoceras (genus Rondiceras) at D over 30 mm usually have smooth inner whorls possessing only striate ornamen tation. One of Late Bathonian Cadoceras from the Ger chyoch Mountain Pass, represented by a sufficient number of specimens for positive identification,
Explanation of Plate 4 All sizes are ×0.95. Asterisk (*) marks the beginning of the body chamber. Fig. 1. Cadoceras suevicum Callomon et Dietl, PIN, no. 5337/7, specimen with the anterior third of the body chamber separated: (1a) lateral and (1b) apertural views, (1c) inner whorls, lateral view, and (1d) ventral view. Fig. 2. Cadoceras tschernyschewi Sokolov, PIN, no. 5337/6, specimen with a complete body chamber and preserved aperture: (2a) lateral and (2b) ventral views. Mountainous Ingushetia, Gerchyoch Mountain Pass; Armkhi Formation; collected by A.S. Sakharov. PALEONTOLOGICAL JOURNAL
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belongs to a new species, C. sakharovi sp. nov. (described below). One specimen represented by a fragment identified to species was found in one nodule with the previously figured Cadomites sp. (Mitta, 2011, pl. 1, fig. 1), identified by Sakharov as Kepplerites aff. curtilobus Buckman. The genus Cadomites Munier Chalmas, 1892 (subfamily Cadomitinae of the family Stephanoceratidae) is known from the Middle Bajo cian and relatively widely distributed in the Bathonian of the Peritethys, although some species represented by a few specimens are also identified from the lower most Callovian of the subboreal regions (Dietl and Herold, 1986). One ammonite, represented by a single specimen from Sakharov’s collection (Fig. 4), clearly belongs to a different species. This species shows significantly less inflated whorls, more strongly rounded in cross sec tion and wider umbilicus resembling the Late Batho nian Cadoceras, identified by Meledina (1999, pl. 2, figs. 6–8) from Kotelnyi Island as C. perrarum Vor onetz. The latter species was described (holotype: Vor onetz, 1962, pl. 15, fig. 1) based on an incomplete specimen from the Lena River (Chekurovskii Cape), as an Early Callovian taxon. Meledina’s studies allow its age to be emended as corresponding to the Cadoceras barnstoni Zone, which is an upper zone of the Bathonian of the Canadian zonation (Poulton, 1987). The incompleteness of the data on this species and the insufficient material on Caucasian representa tives suggest that this taxon should be identified as C. aff. perrarum. These two taxa, C. sakharovi and C. aff. perrarum, based on the presence of a welldeveloped ventral ornament on the body chamber, should certainly be assigned to the Late Bathonian group of the genus, and most likely come from the upper zone of the Bathonian Stage. Based on the rare indications of stratigraphic occurrence that can be found on the labels, it can be assumed that the ammonites identified by myself as C. tschernyschewi, come from the upper and possibly the middle parts of Bed 4. Other species apparently come from the lower portion of this bed, in the prox imity of the Bathonian–Callovian boundary. A more precise identification of this boundary in the section of the Gerchyoch Mountain Pass is only possible after reexamination of the section. Accordingly, the bed should be dated based on cadoceratins to the upper zone of the Bathonian–lower zone of the Callovian. The boundary between the stages lies within the bed (and the formation). The supposed succession of
ammonites in the section of the Gerchyoch Pass and its correspondence to the zonation of Central Russia are shown in Table 1. Thus, the following conclusions are drawn: There is no inversion in the succession of biostrata of the Armkhi Formation in the northern Caucasus. A normal stratigraphic succession is clearly observed. The ammonites found there suggest a Late Bathonian age of Bed 3 and the lower part of Bed 4; the middle– upper portion of clays of the latter bed is Lower Call ovian. Thus, the presence of the marine Bathonian rocks is confirmed for the northern Caucasus. The taxonomic composition of cardioceratids and cos moceratids of the northern Caucasus at the Batho nian–Callovian boundary, which is very similar to that of Central Russia and subboreal regions of Western Europe, suggests a connection between the Central Russian, West European, and northern Caucasian basins at that time. SYSTEMATIC PALEONTOLOGY Family Cardioceratidae Siemiradzki, 1891 Subfamily Cadoceratinae Hyatt, 1900 Genus Cadoceras Fischer, 1882 Cadoceras sakharovi Mitta, sp. nov. Plate 5, fig. 1
Cadoceras sp. nov.: Mitta, 2011, pl. 1, fig. 2.
E t y m o l o g y. After Aleksandr Stepanovich Sakharov. H o l o t y p e. PIN, no. 5337/3; Mountainous Ingushetia, Gerchyoch Mountain Pass; Armkhi For mation; collected by A.S. Sakharov. D e s c r i p t i o n (Fig. 5). The shell is medium sized. The early whorls (diameter up to 30 mm) are moderately wide, rounded in cross section, with the maximum width in the lower third of the flanks. With age, the whorls become more strongly inflated. At Dm = ca. 70 mm, the whorls are very strongly inflated, and the width of the cross section is more than twice its height. At the end of the body chamber, the section becomes less inflated. Its height slightly decreases and the venter becomes considerably narrower. The umbi licus is deep, moderately wide on the fragmocone, and expands to become wide on the body chamber. The body chamber is not less than threefourths of the whorl. The aperture is simple, well delineated by a constriction clearly visible on the mold. The ornamentation of the early whorls is typical for the genus. At Dm over 60 mm, thin ribs are observed,
Explanation of Plate 5 All sizes are ×0.95. Fig. 1. Cadoceras sakharovi sp. nov., holotype PIN, no. 5337/3, specimen with a complete body chamber and preserved aperture, the beginning of the body chamber was in the missing portion of the external whorl: (1a) lateral and (1b) ventral views, (1c) inner whorls, lateral view, (1d) ventral view; Mountainous Ingushetia, Gerchyoch Mountain Pass; Armkhi Formation; collected by A.S. Sakharov. PALEONTOLOGICAL JOURNAL
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Fig. 4. Cadoceras aff. perrarum Voronetz, specimen with a complete body chamber and the aperture preserved on one side, PIN, no. 5337/9: (a) lateral and (b) ventral views, (c) inner whorls, lateral view, (d) ventral view; Mountainous Ingushetia, Gerchyoch Mountain Pass; Armkhi Formation, Lower Callovian; collected by A.S. Sakharov.
which begin from the umbilical edge to become wider on the umbilical wall (the latter gently fused with the flanks), as they approach the umbilical shoulder. On the ventrolateral shoulder (coinciding with the umbil ical shoulder), the ribs are raised to form carinate
inflations. These inflations, which with age become thickened lateral nodes, give rise to two or three wide branches crossing the venter with a clear inclination forward. On the venter, the branches expand and are accompanied by threadlike growth striae. The body PALEONTOLOGICAL JOURNAL
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Fig. 5. Cadoceras sakharovi sp. nov.: (a) specimen PIN, no. 5337/2, whorl cross section with a portion of the body chamber sep arated from a specimen figured by Mitta, 2011, pl. 1, fig. 2; (b) specimen PIN, no. 5337/5, part of the phragmocone is separated, lateral view; Mountainous Ingushetia, Gerchyoch Mountain Pass; Armkhi Formation; collected by A.S. Sakharov.
chamber most clearly shows prominent umbilical inflations and branches of ribbing in the midventer. D i m e n s i o n s i n m m a n d r a t i o s: Specimen PIN, no. Holotype 5337/3
5337/4 5337/2
5337/5
Dm
WH WW UW WH/Dm WW/DmUW/Dm
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50
62
44
0.41
0.51
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72 50 29 119 115 81 67 72 49
25 18 12 37 41 36 22 26 18
53 25 11 63 62 59 51 53 37
24 16 9 45 46 28 24 26 14
0.35 0.36 0.41 0.31 0.36 0.44 0.33 0.36 0.37
0.74 0.50 0.38 0.53 0.53 0.73 0.76 0.74 0.75
0.33 0.32 0.31 0.38 0.40 0.35 0.36 0.36 0.29
Va r i a b i l i t y. The shells are relatively uniform, which allows positive identification to one species. The specimen that I figured previously (see the above synonymy list) is apparently immature, as it does not show the narrowing of the apertural zone of the body chamber. C o m p a r i s o n. The new species clearly differs from all Early Callovian members of the genus in the PALEONTOLOGICAL JOURNAL
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prominent ventral ribs. This character, in association with strongly inflated whorls, resemble many previ ously described Early Bathonian species, primarily numerous high boreal taxa from Arctic Canada, East ern Greenland, and northern Siberia. The northern Caucasian species is distinguished by the strongly developed umbilical inflations and narrowing anterior portion of the body chamber in adult specimens. R e m a r k s. Specimens assigned to the new spe cies were identified by Sakharov as C. anabarense Bodylevsky, C. elatmae (Nikitin), C. elatmae ingus cheticum subsp. nov., C. sazonovi sp. nov., and C. rarum sp. nov. O c c u r r e n c e. Mountainous Ingushetia, Armkhi River Basin; Armkhi Formation, Upper Bathonian. M a t e r i a l. Four well and satisfactorily preserved specimens and one fragment from the same nodule with Cadomites sp. (all from the Gerchyoch Mountain Pass); another two specimens are labeled as “Moun tainous Ingushetia” and “northeastern Caucasus.” ACKNOWLEDGMENTS G. Dietl and G. Schweigert (Stuttgart) helped with the study of the museum collection of the Lower Call ovian Cadoceras of southern Germany. M. Görlich, a
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manager of the Sengenthal quarry in Bavaria, provided friendly assistance with excavations in this quarry in 2009 and 2010, when I was able to observe that Macro cephalites and Kepplerites are commonly found in the Upper Bathonian of southern Germany. This research was supported by the Deutsche Forschungs Gemein schaft (DFG), through H. Keupp (Berlin). The pho tographs are provided by V.T. Antonova (PIN). I dis cussed the taxonomy of cadoceratins with G. Dietl (Stuttgart), V.G. Knyazev (Yakutsk), and the late J.H. Callomon. The study was supported by the Rus sian Foundation Basic Research, project no. 1105 01122, and the Program of the Presidium of the Rus sian Academy of Sciences “Origin of the Biosphere and the Evolution of Geobiological Systems.” I am sincerely grateful to all the people and funds who par ticipated in this study. REFERENCES Blake, J.F., A Monograph of the Fauna of the Cornbrash, in Monogr. Palaeontogr. Soc., London, 1905–1907, pp. 1–106. Dietl, G., Über Macrocephalites (Ammonoidea) aus dem AspidoidesOolith und die Bathonium–Callovium Gren zschichten der Zollernalb (S.W.Deutschland), Stuttg. Beitr. Naturk. Ser. B, 1981, no. 68, pp. 1–15. Dietl, G. and Herold, G., Erstfund von Cadomites (Ammonoidea) im UnterCallovium (Mittl. Jura) von Süd westDeutschland), Stuttg. Beitr. Naturk. Ser. B, 1986, no. 120, pp. 1–9. Gulyaev, D.B., Infrazonal Stratification of the Upper Bathonian and Lower Callovian of the East Europe Plat form Based on Ammonites, in Yurskaya sistema Rossii: problemy stratigrafii i paleogeografii (Jurassic System of Rus sia: Problems of Stratigraphy and Paleogeography), Mos cow: Geol. Inst. Ross. Akad. Nauk, 2005, pp. 64–70. Kiselev, D.N. and Rogov, M.A., Sequence of Ammonites in Boundary Horizons of the Bathonian and Callovian of the Middle Volga Region, in Yurskaya sistema Rossii: problemy stratigrafii i paleogeografii (Jurassic System of Russia: Prob lems of Stratigraphy and Paleogeography), Yaroslavl: Izdvo Yarosl. Gos. Ped. Univ., 2007a, pp. 102–120. Kiselev, D.N. and Rogov, M.A., Stratigraphy of the Batho nian–Callovian Boundary Deposits in the Prosek Section (Middle Volga Region): Article 1. Ammonites and Infra zonal Biotratigraphy, Stratigr. Geol. Korrelyatsiya, 2007b, vol. 15, no. 5, pp. 42–73 [Stratigr. Geol. Correl., 2007b, vol. 15, no. 5, pp. 485–515]. Lominadze, T.A., Callovian Cadoceratids of the Caucasus, Tr. Geol. Inst. Akad. Nauk Gruz. Nov. Ser., 2004, vol. 119, pp. 347–369. Lominadze, T.A. and Sakharov, A.S., Stratigraphical Posi tion of Beds with Kepplerites gowerianus on the Northern Caucasus, in Geologiya i razvitie mestorozhdenii poleznykh iskopaemykh Gruzii (Geology and Development of Minerals of Georgia), Tbilisi: Gruz. Politekhn. Inst., 1984, pp. 27–31. Lominadze, T.A. and Sakharov, A.S., Kosmotseratidy Kavkaza (Cosmoceratids of the Caucasus), Tbilisi: Metsniereba, 1985. Matskevich, M.M. and Sakharov, A.S., On the Relation ships of the Shale and Carbonate Jurassic and Structure of
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