Prilronrolo,qir 111Jn~rnial. MI/. 38. No. 5. 2004, pp. 1~Y3191.Tr~m.sl~rfc~dfr~~rn Prrlronfol~~#ichrskii Zhurnal, No. 5. 2001. I?/'. 17-24 Ori#inol R~rs.s~unTmf Copyri~lir0 2004 hy Mirr~i Engli.sh Trunsl~rfir~nCop\ri,qhr 0 2004 I)! MAlK "Nour(u/lnfrrl~eriodic(i"(R~r.ssr(r).

On the Ammoilite Succession in the - Boundary Beds of the Moscow Syneclise V. V. Mitta Paleontological Institute, Rlissian Academy of Sciences, Profsoyuztzaya ul. 123, Moscort: 11 7997 Russia e-mail: vmitta @ mail. ru Received July 10, 2003

Abstract-The succession of ammonite assemblages in the central regions of the Russian Platform from the Virgatites virgatus Zone (Middle Volgian Substage) to the Surites tzikwiniutlus Zone (Ryazanian Stage) is dis- cussed. The analysis of the data available suggests a considerable gap between the nodiger Zone, terminal in the Volgian Stage, and the Riasutlires rjasanensis Zone, basal in the Ryazanian Stage. Prcresurites nikitini sp. nov. and Pseudocruspedites bogomolovi sp. nov. from the basal beds of the Ryazanian and Praerollia olivikorum sp. nov. from the unnamed unit above the top of the Volgian are described. The three genera to which these species belong are recorded for the first time from the Russian Platform. They allow a bctter correlation of the Jurassic-Cretaceous boundary beds within the Boreal Realm.

Key \r,ords:Ammonites, Jurassic-Cretaceous boundary, Moscow Basin.

INTRODUCTION and converted it into a regional stage, while theTithonian was considered to be the only valid name for the terminal For more than 100 years, international commissions Jurassic, including the entire territory of the Boreal and bodies have adopted a number of controversial Realm. It was recommended that the Jurassic-Creta- decisions on the stratigraphic nomenclature of the ceous boundary be drawn between the Middle and Upper Jurassic-Cretaceous boundary beds. The decisions substages of the Volgian Stage (Decisions.. ., 1997). adopted in 1964 (Cassis, France; Moscow, USSR) and 1996 (St. Petersburg, Russia) were particularly contra- These decisions, separated by a third of a century, dictory. completed another circle in the history of the nomen- clature of the terminal Jurassic stage (and the basal The Mediterranean Mesozoic Committee in May, stage of the Cretaceous). It is clear that the solution of 1964 in Cassis concluded that the use of the Portlandian this problem has reached a dead end, and that new data as a global stage should be discontinued, while the are required. This conclusion was clearly stated in Tithonian Stage is unacceptable since this stage is not recent publications of the working group on the Juras- geographically based and does not have a stratotype, sic-Cretaceous boundary (Zakharov et a/., 1996). which is required by the rules of stratigraphic nomen- clature. The majority of participants in the Cassis Meet- There is no doubt that the discontinuation of the use ing decided that thevolgian should be used as the name of the Volgian as a global stage was a mistake. This for the terminal Jurassic stage (Sasonov, 1964). Some- opinion is also supported by researchers from other what earlier, the British Mesozoic Committee had countries. The definition of the Jurassic-Cretaceous rejected the Portlandian as a stage of the international boundary is another problem that should logically scale. The bureau of the Jurassic Commission of the result from the substantiated correlation of these series. Interdepartmental Stratigraphic Committee of the Various fossil groups have been used in attempts to USSR (Moscow, 1964) agreed that the names Portlan- solve this problem in recent decades. In addition to dian and Tithonian could not be retained for naming the paleontological data, various methods for geochrono- terminal stage of the Jurassic, because neither met the logical dating were applied to define the relative and existing requirements. Consequently, the Volgian absolute age of the boundary. Unfortunately, none of (including three substages and nine zones) was consid- these approaches was successful. No reliable definition ered to be the only valid name for this stage (Deci- has yet been achieved. sions.. ., 1966, p. 136). The correlative potential of ammonites, an orthos- The Bureau of the Russian Interdepartmental Strati- tratigraphic fossil group, has not been fully utilized. graphic Committee (St. Petersburg, February, 1996) Kowalevsky (1 874, p. 591, estimating their value for the transferred the Volgian Stage from the category of gen- Mesozoic geochronology, referred to them as "the long eral stratigraphic units to the category of regional units hand of the geological clock." This is especially true for the middle part of the Middle Volgian Substage to the Ryazanian Stage, based on the example of the Moscow Region (as the best understood region). Observations were made from 1980 to 2002 in many natural and artificial outcrops in both Moscow and the Moscow Region (including the quarries of phosphoritic mines near the town of Voskresensk, where, according I I @ Euthymiceras to Gerasimov and Mikhailov (1966), the hypostrato- type of the Volgian Stage is located). The interval under consideration contains the following ammonite assem- blages. Middle Volgian, Virgatites virgat~isZone, Virgci- tites gerassimovi Subzone: Virgarites, Lornonossovella, and Dorsoplanites (represented by the later species of this genus, which are sometimes assigned to the subge- nus Vischniakovia Gerasimov); Virgatites virgatus Sub- zone: Virgatites, Lomonossovella, Dnrsoplanires, and Q Rld\anlte\ Serbnrinovella; Craspedites ivanovi Subzone: Virga- @ Serbannovella tites, Lornonossovella, Dorsoplanites, and Craspeclites; I and Epivirgcrrires nikitini Subzone: Epivirgarites, Lomonossovellcr, and Craspedites. Upper Volgian, jiulgens Zone: Kachpurites, Craspedites, and Carniericeras; Cras- pedites suhditus Zone: Craspedites and Carniericeras; and Craspedites nodiger Zone (subdivided into two subzones based on ammonite species): Craspeclites and Carniericeras. Ryazanian, Riasanites rjasanensis Zone: Riasnni- tes, E~~thymiceras,YSubaipinites, Transccispiire.~, Praesurites, Pseudocrcispedites, Pronjaites, and Hecro- roceras; and Sirrites rzikwinianus Zone: Surites, Fig. 1. Geological succession of ammonite assemblages at Caseycerczs, and Pronjcrites. the Jurassic-Cretaceous boundary (Moscow Region). Abbreviations: (rj(zsntzuns.) Riasunites rjasanensis and Zonal ammonite assemblages of the upper half of (tzikwinian.) Surites r:ik$vinionus. the Volgian in the remaining territory of the Russian Platform underwent small changes at the species and generic levels. For instance, in the upper reaches of the the Russian Platform, which is a type region for the Volga River, the nikitini Zone still contains the last Dor- Volgian and Ryazanian. The progress of research in this sopiarzites (species continuing from the underlying vir- field has been very slow, primarily because of the scar- gntus Zone) and newly appeared species of Lnirgeites city of well-preserved ammonites in the strongly con- (descendant of Dorsoplanites). In the middle reaches of densed Ryazanian (Berriasian) sequences of central the Volga River, Serbarinovella and Craspedites European Russia. The situation is complicated by the remain unknown from the Middle Volgian, whereas fact that many genera and species were described from Dorsopfanites is unknown from the virgatus Zone. this interval without a good taxonomic basis. The above data suggest an asynchronous disappear- New data obtained by the author in the last two ance of the Virgatitidae and Dorsoplanitidae and decades will allow better correlation of the Jurassic- appearance of the Craspeditidae. The Virgatitidae Cretaceous boundary beds in the Boreal Realm. At the became extinct at the end of the virgatus time, while the same time, they pose new questions concerning the Dorsoplanitidae disappeared in the nikitini time and the basal horizons of the Cretaceous System. first Craspeditidae appeared as early as the ivanovi Sub- zone of the virgatus Zone. Zonal boundaries within the Volgian are clearly recognized by the change in taxo- RESULTS nomic composition, although no considerable gaps Ammonite Assemblages between the zones are likely. The assemblages from the at the Jurassic-Cretaceor~s Boundary middle and upper substages clearly differ. In this case, the stepwise nature of ammonite evolution is recog- The succession of ammonite assemblages in the nized at the family level. At the same time, all taxa are Jurassic-Cretaceous boundary beds is of special inter- endemic, having originated and evolved in the Central est primarily because of the possible estimation of gaps Russian Basin. It is noteworthy that the M~ddleVolgian between these units. Figure 1 shows a succession trom zones are in fact genozones, i.e., the three zones of this

PALEONTOLOGICAL JOURNAL Vol. 38 No. 5 2004 ON THE AMMONITE SUCCESSION IN THE JURASSIC-CRETACEOUS BOUNDARY BEDS 485 substage are characterized by different taxa of the the River Unzha, near the village of Ogarkovo; phos- genus group, while only some species, e.g., Lomonoss- phoritic bed at the base of the Ryazanian Stage (col- ovella lomonossovi (Vischniakoff), continue from one lected by Gerasimov in 1934). zone to another. In contrast, Upper Volgian zones are D e s c r i p t i o n. The phragmocone is medium- mainly characterized by taxa of the species group sized, with inflated and depressed whorls. The flanks (except for the lower zone typified by the genus Kachpu- are weakly convex, descending to the rounded venter. rites in addition to Craspedites and Garniericeras).This The maximum whorl width is near the umbilicus. The certainly indicates different absolute durations of the whorls embrace the preceding whorls for three-quarters Middle and Upper Volgian. Evidently, the Upper Volgian was half as short as the Middle Volgian. of their height. The umbilicus is shallow and moder- ately wide at all stages. The umbilical shoulder is The ammonite assemblage from the rjascirwnsis rounded. The body chamber length and the shape of the Zone, lowermost in the Ryazanian, is very different aperture are unknown. The ornamentation consists of from those of the overlying tzikwinianus Zone, and, relatively thin. evenly convex ribs. The subradial pri- especially, from the preceding rzodiger Zone of the Vol- mary ribs appear on the umbilical shoulder and dichot- gian. A short-termed invasion from the marginal omize (more rarely trichotomize) at midflanks or Tethyan basin to the Central Russian (Volgian) Basin slightly closer to the venter. The secondary ribs are sig- led to the arrival of the family Neocomitidae sensu lato, moidally curved approaching the venter and cross the which did not have local ancestors. Apparently, the gap venter with a weak bend orad. between the rjosarlerlsis and tzikwinianus zones is smaller, which is evident from the presence of the com- Dimensions in mm and ratios: mon genus Prorljaites and the evolutionary lineage Praesurites - Surites. In the more northern and east- em regions of the Russian Platform, both zones of the Ryazanian Stage are characterized almost exclusively by taxa of boreal origin, except indications of Riasani- PIN, no. 39901235 74 29 3 1 22 0.39 0.42 0.30 tes, which are very rarely supported by collections. Holoty pe Even taking into account the preliminary exclusion GGM, no. 1385 61 25 28 18 0.41 0.46 0.29 of clearly subjective synonyms, the number of generic 60 25 27 16 0.42 0.45 0.27 names for the rjasatlensis Zone is more than double the PIN, no. 39001236 49 19 21 13 0.39 0.43 0.27 usual number of genera for the underlying and overly- ing zones. This shows the complex composition of the GGM, no. 1386 43 18 18 1 1 0.42 0.42 0.26 zone and its condensed nature, which is supported by PIN. no. 39901237 34 14 14 10 0.41 0.41 0.29 its lithology. The rarity of finds of well-preserved ammonites in the thin bed of the Rjasanensis Zone, Va r i a b i I i t y. There are two varieties that are not together with their occurrences in different localities strongly distinct. The first (including the holotype and and collections made over a considerable length of paratype figured by Gerasimov) has the higher and time, in most cases do not allow their positive referral weakly convex whorls. These ammonites more fre- to finer stratigraphic units. Nevertheless, the ammo- quently have tripartite ribs, while older individuals may nites described below extend our knowledge on the bio- have intercalating ribs, and the ventral curvature of the geography of so-called boreal ammonites, allow the ribs is better pronounced. The representatives of the sec- refinement of their phylogeny, and offer some new ond (apparently earlier) variety have more depressed stratigraphic and correlative interpretations. whorls and mainly bipartite ribs (PI. 2, figs. 1-4). Material described is housed at the Vemadsky State C o m p a r i s o n. This species is distinguished from Geological Museum of the Russian Academy of Sci- the type species P. elegans Mesezhnikov et Alekseev, ences (GGM), collection nos. 1385 and 1386 (collected 1983 by the lower and more inflated whorls and less by P.A. Gerasimov), and the Paleontological Institute densely spaced ribs. of the Russian Academy of Sciences (PIN), collection R e m a r k s. Gerasimov figured two specimens of nos. 3990 and 486 I. this species, which he erroneously thought to be from the tzikwinianus Zone, and designated the holotype in SYSTEMATIC PALEONTOLOGY the explanations to the plates, although he did not describe the species. The present description validates Family Craspeditidae Spath, 1924 the species and brings it into accord with the Intema- Genus Praesltrites Mesezhnikov et Alekseev, 1983 tional Code of Zoological Nomenclature. Apparently, Praesurites nikitini Gerasin~ovet Mitta sp. nov. this species evolved from the Late Volgian Cra.\pedites, Plate 2, figs. 1-4 and was ancestral to Surites Sasonov, 195 1 via S. ~insh- S~lritc,.rnikitini: Gerasirnov. 1969, pl. 30, 6gs. 1 and 2 (nornen ensis (Nikitin, 1885, pl. 5, fig. 23) and S. spasskerlsis nudurn). (Nikitin, 1888, pl. 1, figs. 9, lo). H o l o t y p e. GGM, no. 1385; figured by Gerasi- 0 c c u r re n c e. Ryazanian Stage, rjasanmsis mov (1969, pl. 30, fig. I); Kostroma Region, bank of Zone of the Moscow Syneclise.

PALEONTOLOGICAL JOURNAL Vol. 38 No. 5 2004 PALEONTOLOGICAL JOURNAL Vol. 38 No. 5 2004 ON THE AMMONITE SUCCESSION IN THE JURASSIC-CRETACEOUS BOUNDARY BEDS 487

M a t e r i a I. Ten specimens from the rja.sanet~si.s C o m p a r i s o n. This species is very similar to the Zone of the Lopatinskii Phosphorite Mine; four phrag- type species P. atzglic.~is(Schulgina, 1972) in the shell mocones from phosphoritic nodules in the basal part of shape and ornamentation of juvenile whorls. It is distin- the Ryazanian Stage; outcrop on the right bank of the guished from the latter by the shorter primary ribs (pli- Unzha River, near the village of Ogarkovo. cations) in adult whorls. It is distinguished from P. cra;\peditoicles (Girmounsky, 19 14) (PI. 3, fig. I ) by the more compressed shell, more strongly developed Genus Pseudocraspedites Casey, constrictions, and by the more densely spaced and thin- Mesezhnikov et Schulgina, 1977 ner ribs at intermediate stages. Pseserrdocraspediles bogomolovi Mitta, sp. nov. R e m a r k s. P. craspeditoicles was described by Platc 3, figs. 2-7 Girmounsky (1914, pl. 5, figs. 1-3, lectotype, desig- E t y m o I o g y. In honor ofYu.1. Bogomolov, expert nated here, housed at the GGM, no. VI- 12411 ) under the on Lower Cretaceous ammonites (Bogomolov, 1989; etc.) generic name Polyptychites; found in the basal bed of the Neocomian in the Unzha River Basin (near the vil- H o l o t y p e. PIN, no. 4861154; Moscow Region, lage of Ogarkovo). It has never been described since. Lopatinskii Phosphorite Mine; Ryazanian Stage, rjasatz- Apparently, P. craspeditoides, which also is rarely ensis Zone (collected by Gerasimov and Mitta in 1984). found in the lower horizons of the Ryazanian Stage in D e s c r i p t i o n. The shell is medium-sized, with the Moscow Region and very closely related to Cras- medium-wide whorls embracing the preceding whorls pedires, was ancestral to the new species. P. craspetli- for two-thirds of the height. The cross section is oval, roides apparently evolved from the Late Volgian species widest in the lower third of the flanks. The flanks are Craspedites rriptych~is(lectotype figured by Nikitin, convex, converging to the rounded venter. The umbili- 1885, pl. 6, fig. 25, designated by Gerasimov, 1969). cus is moderately wide and shallow. The umbilical wall gently slopes at early stages, becoming steeper in The early whorls of P. bogomolovi are similar to adults. The umbilical shoulder is rounded. The body those of many taxa described from various localities in chamber length and apertural shape are unknown. Well- northern Siberia, Polar Ural Mountains, and England developed constrictions are usually observed at inter- under different species and generic names. These are mediate stages. The ornamentation of juveniles consists Cmspeclites? arcticus (Schulgina, 1969, pl. 33, fig., 4), of densely spaced, thin ribs of even height. In the lower Craspeclites (Tnimyrocen~s)tnimyrensis (Schulg~na, third of the flanks, primary ribs give rise to two or three 1 969, pl. 34, fig. I b), Craspedites originalis (Schulg- secondary ribs, some of which lose connection with the ina, 1969, pl. 36. figs. 2, 4), S~rhcraspeditesturbincre primary ribs. With age, primary ribs become more (Mesezhnikov et nl., 1983, pl. 6, fig. 9), S~ihcre1spedite.s prominent and are later modified into umbonal ribs (pli- sp. (Casey, 1973, pl. 4, fig. 6), and S~ibcraspedites(Vol- cations), which are smoother in the lower third of the giclisc~is)lcrrnpl~ighi (Casey, 1973, pl. 4, fig. 9). which flanks before reaching the midflanks. The secondary indicate close similarity of these ammonites. Morpho- ribs become thinner and are only slightly noticeable on logical features of the new species and its stratigraphic the mold. Their number may increase to four or five in range suggest that it was ancestral to the genus Pere- a bunch. grinocerc~sSasonova, 197 1. Dimensions in mm and ratios: The authors of the genus Pseudocra.spedites sug- gested to include several species previously described E under different names: by Schulgina (1 972) as Subcrcls- Specimen 0 pedites (Subcraspeditrs) utzglicus, S. (S.) plicomphal~i~s, 7. &$5333-.3 S. (S.) sshprcssul~~sand S. (S.)pressul~~s (all from Sibe- Holotype 4861154 61 21 21 19 0.39 0.34 0.31 ria); by Jeletzky (1964) as Tollia (Subcraspedites) aff. .suprcrsubdit~is,and 7: (S.)spas.sketzsis from Arctic Can- 19901241 ") l6 0.35 0.28 ada. Of these ammonoids, only the first species can be 4861152 40 l6 l2 0.40 0.33 0.30 considered to have been erected correctly, in accor- 39901243 37 IS 12 11 0.41 0.32 0.30 dance with the rules of the International Code of Zoo- 39901242 33 13 11 10 0.39 0.33 0.30 logical Nomenclature.

I Explanstion of Plate 2 All sizes are natural Figs. 1-4. Prc~esuri~rst~ikitini sp. nov., specimens: (1) PIN, no. 39901735, (2) PIN. no. 39901236. (3) PIN. 39901237, and (4) PIN. 39901245; Lopatinskii Phosphorite Mine; Ryazanian Stage, Kicrsar~itesrjasanensis Zone; collected by V. Mitta. in 1983-86. Figs. 5-8. Prcletollia olivikorrrrn sp. nov.: (5) GGM, unnumbered paratype, Kirov Region, Nyrnlich: collected by A.A. Chetyrkina; (6) paratype PIN. no. 39901239; (7) holotype PIN, no. 39901238. and (8) specimen PIN, no. 39901238a; Kostroma Region. hank of the Unzha River, hetween the villages of Ogarkovo and Efimovo; phosphoritic bed at the top of the Volgian: collected hy V. Mitta. 0. Nagel. and V. Pirkl in 2000.

PALEONTOLOGICAL JOURNAL Vol. 38 No. 5 2004 488 MITTA

Plate 3

PALEONTOLOGICAL JOURNAL Vol. 38 No. 5 2004 ON THE AMMONITE SUCCESSION IN THE JURASSIC-CRETACEOUS BOUNDARY BEDS 489

M at e r i a I. Eleven specimens from the r-jrlsanetlsis able fragments of large whorls (PI. 2, fig. 8) show only Zone, Lopatinskii Phosphorite Mine. a venter and, partly, ventrolateral areas. Therefore, it is difficult to predict whether or not the adult whorls of the new species have inflated primary ribs. Genus Praetollia Spath, 1952 rn Praelollia olivikorum Mitta, sp. nov. Re a r k s. The holotype was found in a phospho- ritic bed at the top of the Volgian Stage. Further excava- Plate 2. figs. 5-8 tion of the same bed produced another three fragments E t y m o logy. After the names of my friends of larger whorls of a phragmocone that apparently also Oliver Nagel and Viktor Pirkl, who found the holotype belonged to the holotype. The paratype (PI. 2. fig. 6) of this species during our joint excursion in 2000. was found not in sitrr among Upper Volgian ammonites H o l o t y p e. PIN, no. 39901238; Kostroma Region, (mainly Craspedites), washed out from the phosphor- bank of the Unzha River, between the villages of itic bed. It is noteworthy that, among several thousand Ogarkovo and Efimovo; phosphoritic bed at the top of ammonites from this locality which the author studied the Volgian Stage. in a number of collections (including his own and those D e s c r i p t i o n. The phragmocone is medium- of museums and private collectors), this species was sized, with moderately wide whorls, ellipsoidal in cross never found. section. 'The flanks are almost flat. The venter is A box containing Berriasian-Valanginian ammo- rounded. The umbilicus is moderately narrow. The nites labeled as the collection of A.A. Chetyrkina from umbilical wall is steep. The umbilical shoulder is the Nyrmichskoe phosphorite deposit in the Kirov rounded. The body chamber and apertural shape are Region (housed among old collections in GGM) con- unknown. The ornamentation consists of thin but prom- tained one more phosphoritic mold of an ammonite inent ribs dichotomizing and trichotomizing at the mid- belonging to the species under description (PI. 2, fig. 5). flanks. The ribbing coefficient is close to 3. Intercalat- ing ribs appear when one of the secondary ribs loses The Greenland ammonites figured by Spath (1952) connection with a primary rib. Primary ribs become in their first description are completely or partly slightly thicker with age and widen as they approach crushed. Therefore, a more thorough comparison is dif- the bifurcation point. ficult. However, the character of rib bifurcation in the new species and the shape of the umbilicus are similar Dimensions in mm and ratios: to those of typical Prcretolli~~,which is sufficient to assign it to this genus. The composition and taxonomic position of the genus Praetollin are debated. The above mentioned Holotypc 3990/?38 75 34 25 18 0.45 0.33 0.24 ammonite described by Jeletzky does not belong to the 44 20 16 10 0.45 0.36 0.23 species Pseuclocra.~pedites angliciis (Schulgina) or 3990/239 31 14 12 7 0450.190.21 even to the genus (or subgenus) Pseuclocraspedites. The inflated primary ribs repeatedly appeared in the C o m p a r i s o n. The new species is distinguished ontogeny of various Craspeditidae genera (and their from the type species I? maytici (holotype figured by ancestral family Dorsoplanitidae) and are more useful Spath, 1952, pl. 3, fig. 2) by the larger proportion of tri- as a character at the species level. partite ribs. This species is similar to P contiqcla (see Ammonites from the Neocomian of Canada that Spath, 1952, pl. 3, fig. I, the type specimen originally were described as Praerollia untiquu (holotype figured established by Spath as a variety of I? maynci). Judging by Jeletzky, 1973, p. 75, pl. 5, fig. I) are similar in orna- from illustrations, the new species is distinguished by mentation to Slrrites sensu lato. Casey (1 973) assigned having fewer intercalating ribs. them to the genus Borealites sensu stricto. Most proba- Jeletzky (1984, pl. 7, fig. 10) figured an ammonite bly, these ammonites suggest the Late Berriasian, from Arctic Canada. which has juvenile whorls and because morphologically similar ammonites were ornamentation very similar to the new species, under found from the tzikwinianus Zone of the Russian Plat- the name "Praetollia (Pseudocraspedites) anglicrrs. " form. In fact, Jeletzky himself later synonymized his Small differences in our specimens are observed only in species with Borealites fedorovi Klimova, 1969 the more strongly flattened flanks. Unfortunately, avail- (Jeletzky, 1984).

f------pppp Explanation of Plate 3 All sizes arc natural Fig. 1. P.seudoc~rl~spedirescrcrspeditoides (Girmounsky, 19 14). specimen PIN. no. 39901244, Figs. 2-7. P,seudocmspedifes bogornolovi sp. nov.; (2) paratypc PIN, no. 19901240; (31 paratype PIN. no. 299W2.13: (4) paratypc PIN. no. 3990/241; (5) paratype PIN, no. 399N242: (6) PIN, paratype no. 4861/52; and (7) holotype PIN, no. 4861154. All specimens are from the Lopatinskii Phosphorite Mine; Ryazanian Stage. Riasunires rjrrslrnensis Zone. collected by Mitra in 1983- 1986 (figs. 1-5) and Gerasimov and Mitra in 1984 (tigs. 6.7).

PALEONTOLOGICAL JOURNAL Vol. 38 No. 5 2004 490 MITTA

Ammonites from the borehole in the North Sea, Casey et al. (1977, pl. 2, figs. 8, 9) figured speci- which J.H. Callomon identified as Praetolia (Abbink mens of Praetollia cf. corltig~laSpath from the ~ibiri- et al., fig. 6/01,6/01', 7/S), most likely belong to the CLLS Zone of northern Siberia. These specimens were genus Hectorocerris. found below the finds of Chetaites sibiricus and are 0 c c u r re n c e. The unnamed zone between the similar to the central Russian species. Later, Alekseev Volgian nocliger Zone and Ryazanian rjasanetzsis Zone (1984) recognized the lower part of the sibiric~~sZone of the Moscow Syneclise. as the Praetollia rnaynci Subzone. In addition to Prae- tollia, this subzone contains Chetaites, Prcie.s~lrites,and M ate r i a 1. Five specimens at various growth Sch~llgitzites(Casey et ell., 1988). Schulgiriites is most stages (probably belonging to two individuals) from the likely a synonym for Hectoroceras. A comparison of phosphoritic bed at the top of the Volgian Stage; Unzha the taxonomic composition of ammonites from the River, near the village of Ogarkovo, and one specimen ~ibiric~lsand kochi zones of Siberia and rja~rinensis from the Nyrmich River. Zone of the Moscow Syneclise allows a conclusion of their almost complete correspondence: in the Oka River DISCUSSION Basin and in the Ryazan-Saratov Depression, the Gas- anerlsis Zone is overlain by the beds with the first Representatives of three "high Boreal" genera are Surites (S. ex gr. spcrsskensis), which are equivalent to recorded for the first time from the Russian Platform, the beds with S. analogus in Siberia. increasing their correlative potential. The correlation of the so-called Craspeclites zones Praes~lriteselegans is recorded from the Chetaites of the Russian Platform and Siberia is not debated and sibiricus Zone of the Polar Ural Mountains. P. nikititzi is apparently correct. Thus, there is a clear gap in the typifies the rjasarlensis Zone (or, more precisely, its stratigraphic scheme of the Russian Platform, corre- lower part) of the Russian Platform. Differences sponding to the interval of Chetaites chetae-Praetollia between these species are minimal, and may be attrib- rnaynci strata in Siberia. In this context, it is remarkable uted to geography, i.e., these zones are probably (may that Chetaite~and Praetollia are found in the phospho- be partly) synchronous. ritic bed (condensation horizon) at the top of the Vol- Pse~ldocrasperfitesarlglicus is found in the middle- gian Stage in the outcrop near the village of Ogarkovo upper part of the Hectorocerrls kochi Zone (Casey et al., on the Unzha River. I have no doubt that these ammo- 1988), i.e., above the Chetaites sibiricus Zone, although nites typify a new, as yet unnamed, stratigraphic unit this also falls within the rjnsarlensis Zone (central Rus- (or units), the closest to the Jurassic-Cretaceous bound- sian equivalent of these two Siberian zones). ary in the Boreal Realm. Thus, the finds of Praesurites and Pseurlocras- Back to the history of the study of the Jurassic-Cre- perfites in the Russian Platform support the correlation taceous boundary stages, it is important to take into scheme proposed by M.S. Mesezhnikov and his col- account the problems that followed the ill-advised deci- leagues in the 1980s. sion of the Interdepartmental Stratigraphic Committee The finds of Prc~etollinand especially their strati- in 1996 (see Mitta, 2001). Correlation of the entire graphic position suggest more interesting conclusions. UpperVolgian Substage with the Berriasian, or a part of As mentioned above, the holotype of P. olivikorut?~ it, immediately causes a nomenclatural problem. In this case, the Khoroshovian Stage introduced by Traut- was found in the upper part of the phosphoritic bed at schold (1 861) and Shchurovsky (1 867) take priority the top of the Volgian Stage. It is represented by a phos- phoritic mold lacking the nacreous layer. Numerous over the Berriasian (Coquand, 1871). The Moscovian ammonites of the genera Crasperfites and (more rarely) Stage proposed by Romanovsky (1 856) (non the Car- boniferous [!] Moscovian of Nikitin [1890]) is equiva- Gartriericerris, characterizing the nodiger Zone, are found in abundance in the lower part of this bed and lent to the Middle Volgian Substage and has priority vary somewhat in preservation (these are phosphoritic over the Tithonian (Oppel, 1865). The Lower Volgian or calcite molds with a nacreous layer). The nodules of Substage is easily included into the Kimmeridgian clayey-calcareous oolitic sandstone of Ryazanian Age serlsu anglico, or is recognized as the Vetlyanian Stage occur above the phosphoritic bed and are sometimes (Sokolov, 1 90 1 ). separated from it by a layer of the glauconite sand. This is a vicious circle. The international and Praesurites ~ozshensis(Nikitin), P. nikitirii sp. nov., and national committees and commissions eradicated in Pseurlocraspeclites crnsperfitoirfes (Girmounsky) are succession the names Portlandian, Tithonian, and, now, described from this level. This bed also contained occa- Volgian. Apparently, now it is time to use all the avail- sional unpublished records of Hectoroceras cf. kochi able information for the solution of the primary ques- Spath. On the other hand, rare, but documented finds tion, i.e., the Boreal-Tethyan correlation of boundary of Clzetnites sp. recorded as "Perisphinctes aff. beds of the Jurassic and -Cretaceous. At the same time, Stschlirovskii Nik." by Nikitin (1885) and as "Cras- although this boundary is significant for resolving pedites sp. nov. =Ammonites aff. Stsch~~rovskiiNik." by important questions in geology and other fields, it Sokolov (1 929) come from a Volgian phosphoritic bed. remains only a boundary between two successive zones.

PALEONTOLOGICAL JOURNAL Vol. 18 No. 5 2004 ON THE AMMONITE SUCCESSION IN THE JURASSIC-CRETACEOUS BOUNDARY BEDS 49 1

ACKNOWLEDGMENTS 15. V. O. Kowalevsky, "Brief Account on the Boundary between the ~urassicand Cretaceous Formations and on I am greatly indebted to A.A. Shevyrev for useful a Role That May Play Russian Jurassic Strata in the Res- comments in preparation of this paper. olution of This Question," Izv. Imp. 0-va Estestvozn. The study is part of the Federal Research Program Antropol. Etnogr. 14 (protocols), 41-75 (1 874). "Coevolution of Ecosystems and Global Changes in M. S. Mesezhnikov, S. N.Alekseev, I. G. Klimova, etal., the Past." "On the Development of Some Craspeditidae at the Jurassic-Cretaceous Boundary," in Me.sozoic of the REFERENCES Soviet Arctic Region (Inst. Geol. Geofiz.. Novosibirsk, 1983), Vol. 555, pp. 103-1 25 [in Russian]. I. 0.A. Abbink, J. H. Callomon, J. B. Riding, et al., "Bio- V. V. Mitta, "AmmoniteAssemblages from the Jurassic- stratigraphy of Jurassic-Cretaceous Boundary Strata in Cretaceous Boundary Strata in the Moscow Region and the Terschelling Basin, the Netherlands," Proc. Yorkshire the Problem of the Jurassic-Cretaceous Boundary." in Geol. Soc. 53 (4), 275-302 (2001 ). Problems of Stratigraphy arid Paleogeography of the 2. S. N. Alekseev, "New Data on the Zonation of the Berri- Boreal Mesozoic (Geo, Novosibirsk, 2001), pp. 24-25 asian Stage in Northern Siberia," in Boundary Stages elf [in Russian]. the Jurassic and Cretaceous (Nauka. Moscow, 1984), pp. 81-106 [in Russianl. S. N. Nikitin, "General Geological Map of Russia: Sheet 3. R. Casey, "The Ammonite Succession at the Jurassic- 7 1 ," Tr. Geol. Kom. 2 (1 ). 1-2 18 (1 885) [MCm. Corn. Cretaceous Boundary in Eastern England," Geol. J., Gkol. 2 (I), (1885)l. No. 5 Spec. (The Boreal Lower Cretaceous), 193-266 S. N. Nikitin, "Traces of the Cretaceous in Central Rus- (I 973). sia," Tr. Geol. Kom. 5 (2), 1-205 (1888) [MCrn. Com. 4. R. Casey, M. S. Mesezhnikov, and N. I. Schulgina. "Cor- GCol. 5 (2), ( l888)I. relation of the Jurassic-Cretaceous Boundary Strata in S. N. Nikitin, " Strata of the Moscow England, Russian Platform, Polar Ural Mountains, and Region and Artesian Waters under Moscow," Tr. Geol. Siberia," Izv. Akad. Nauk SSSR, Ser. Geol., No. 7, 14-33 Kom. 5 (3, 1-138 (1890) [MCrn. Com. GCol. 5 (5). (I 977). ( 1 890)l. 5. R. Casey, M. S. Mesezhnikov, and N. I. Schulgina, A. Oppel. "Die Tithonische Etage," Z. Deutsch. Geol. "Ammonite Zones of the Jurassic-Cretaceous Boundary Gesellsch. 17. 535-558 (1865). Strata in the Boreal Realm," Izv. Akad. Nauk SSSR, Ser. G. I. Romanovsky, "Geognostic Review of Soil in Mosk- Geol., No. 10, 71-83 ( 1988). ovskii, Podolskii, and Serpukhovskoi Districts," Gorn. 6. H. Coquand. "Sur le Klippenkalk des departements du Zh. 2, 125-176 (1856). Var et des Alpes-Maritimes." Bull. Soc. GCol. Fr., S6r. 3 N. T. Sasonov, "On the Activity of the Mediterranean 28,208-234 ( 187 1 ). Mesozoic Committee in the Field of the Nomenclature 7. "Decisions of the Enlarged Session of the Bureau of the Jurassic Commission of the Interdepartmental Stmti- of the Jurassic System," Sov. Geol., No. l 1. 145-147 graphic Committee on the Upper Stage of the Volgian ( 1964). System, Moscow, October 29, 1964," Izv. Akad. Nauk N. I. Schulgina, "Volgian Ammonites," in Reference Sec- SSSR, Ser. Geol., No. 2, 136 (1966). tion of the Upper Jurassic Strata of the Kheta River 8. "Decisions on the Revision of the Position of the Juras- Basin (Khatanga L)epre.ssion) (Nauka, Leningrad, sic-Cretaceous Boundary in the Boreal Realm and the 1969), pp. 125-162 [in Russian]. Status of the Volgian Stage," in Decisiorls ofthe Interde- N. I. Schulgina. "Ammonites from the North of Central partnzerltal Stratigraphical Committee and Its Perma- Siberia," Jurc-ls.ric-Cretaceo~ls Bourldurq. and the Berri- tlent Comnlissions (Vseross. Nauchno.-Issled. Geol. asiarl Stage irr the Boreal Belt (Nauka, Novosibirsk, [nst., St. Petersburg. 1997). Vol. 29, pp. 5-7 [in Russian]. 1972). pp. 137- 175 [in Russian]. 9. P. A. Gerasimov, The Upper Substage of the Volgiatl G. E. Shchurovsky, "Geological History of the Moscow Stage of the Centrul Region of the R~issiari Platform Basin," Izv. 0-va Lyubit. Estestvozn. 1 (2), 1-144 (Nauka, Moscow, 1969) [in Russian]. (1867). 10. P. A. Gerasimov and N. P. Mikhailov, "The Volgian Stage D. N. Sokolov, "On the Geology of the Area around the and the General Stratigraphic Scale of the Upper Series Town of lletskaya Zashchita," Izv. Orenburg. Otd. of the Jurassic System," Izv. Akad. Nauk SSSR, Ser. Russk. Geogr. 0-va, No. 16, 37-78 (1 90 1 ). Geol., No. 2, 118-138 (1966). M. I. Sokolov, "Geological Studies on the Unzha River I I. A. M. Girmounsky, "The Basin of the Lower Unzha in 1925," Izv. Assots. Nauchno-issled. Inst. 1 Mosk. Gos. River (Kozlovo-Korshunskoe)," Ezhegodn. Geol. Min- Univ. 2 (I), 5-31 (1929). eral. Ros. 16 (24), 67-77 (1914) [Ann. GCol. Mink. Russ., 16 (24). (1914)l. L. F. Spath, "Additional Observations on the Inverte- 12. J. A. Jeletzky, "Illustrations of Canadian Fossils: Lower brates (Chiefly Ammonites) of the Jurassic and Creta- Cretaceous Marine Index Fossils of the Sedimentary ceous of East Greenland: 2. Some Infra-Valanginian Basins of Western and Arctic Canada." Pap. Geol. Surv. Ammonites from Lindemam Fjord, Wollaston Forland; Can., No. 64-1 1, 1-101 (1964). with a Note on the Base of the Cretaceous," Meddel. 13. J. A. Jeletzky. "Biochronology of the Marine Boreal Lat- Gr~nland133 (4), 140( 1952). est Jurassic, Berriasian and Valanginian in Canada," H. Trautschold, "Der Moskauer Jura verglichen mit dem Geol. J., Spec. No. 5 (The Boreal Lower Cretaceous.), Westeuropaischen," Z. Deutsch. Geol. Gesellsch. 13, 4 1-80 ( 1973). 361452 (1861). 14. J. A. Jeletzky, "Jurassic-Cretaceous Boundary Beds of V. A. Zakharov, P. Bown. and P. F. Rawson, "'The Berri- Western and Arctic Canada and the Problem of the asian Stage and the Jurassic-Cretaceous Boundary," Tithonian-Berriasian Stages in the Boreal Realm." Spec. Bull. Inst. R. Sci. Nat. Belgique. Sci. Terre., No. 66, 7-10 Pap. Geol. Assoc. Can. 27, 175-255 (1984). ( 1996).

PALEONTOLOGICAL JOURNAL Vol. 38 No. 5 2004