On new Jurassic Rissooidea and Zygopleuroidea convergently similar to them (Gastropoda: Pectinibranchia)

Abstract

A new genus, Boreomica gen. nov., is established; it comprises small-sized gastropods widespread
in the Jurassic of the Russian Plate, the taxonomic position of which was ambiguously treated by previous
authors. The new genus is assigned to the family Rissoidae. The species composition and stratigraphical and
geographical distribution of the genus and its species are discussed. From the Jurassic of the Russian Plate,
Callovian Boreomica exigua (Gerasimov, 1992), the type species of the genus, and Kimmeridgian–Volgian
Boreomica undulata (Tullberg, 1881), and members of the genus without species status from the Bathonian
and Upper Oxfordian are described. Conchological polymorphism of species connected with their eurybiontic
characteristics is discussed. Based on the study of samples of the species B. exigua from different types of
facies, two subspecies are recognized, B. exigua exigua and B. exigua arenosa subsp. nov. Finds of gastropods
morphologically similar to Boreomica are discussed: Katosira? sp. from Mitta et al., 2004, “Procerithium?”
volgense Gerasimov, 1955, “Eulima” pusilla Tullberg, 1881, and “Hudlestonella” caleptra sensu Gerasimov,
1992 are considered. It is concluded that E. pusilla and H. caleptra are unknown zygopleurids, Katosira? sp.
is likely a poorly preserved Katosira, and “Procerithium?” volgense is represented by a mixture of several species
belonging to different genera: several zygopleurid species, the rissoids Boreomica undulata and Bralitzia.
Shells of P. volgense in the P.A. Gerasimov’s collection from the Craspedites nodiger Zone are described as
Laevipleura sp.

Full text

1375
ISSN 0031-0301, Paleontological Journal, 2017, Vol. 51, No. 13, pp. 1375–1394. © Pleiades Publishing, Ltd., 2017.
On New Jurassic Rissooidea and Zygopleuroidea Convergently
Similar to Them (Gastropoda: Pectinibranchia)
A. V. Guzhov
Borissiak Paleontological Institute, Russian Academy of Sciences, Moscow, 117467 Russia
e-mail: avguzhov.paleo@mail.ru
Received November 20, 2016
Abstract—A new genus, Boreomica gen. nov., is established; it comprises small-sized gastropods widespread
in the Jurassic of the Russian Plate, the taxonomic position of which was ambiguously treated by previous
authors. The new genus is assigned to the family Rissoidae. The species composition and stratigraphical and
geographical distribution of the genus and its species are discussed. From the Jurassic of the Russian Plate,
Callovian Boreomica exigua (Gerasimov, 1992), the type species of the genus, and Kimmeridgian–Volgian
Boreomica undulata (Tullberg, 1881), and members of the genus without species status from the Bathonian
and Upper Oxfordian are described. Conchological polymorphism of species connected with their eurybion-
tic characteristics is discussed. Based on the study of samples of the species B. exigua from different types of
facies, two subspecies are recognized, B. exigua exigua and B. exigua arenosa subsp. nov. Finds of gastropods
morphologically similar to Boreomica are discussed: Katosira? sp. from Mitta et al., 2004, “Procerithium?”
volgense Gerasimov, 1955, “Eulima” pusilla Tull b er g, 1881, and “Hudlestonella” caleptra sensu Gerasimov,
1992 are considered. It is concluded that E. pusilla and H. caleptra are unknown zygopleurids, Katosira? sp.
is likely a poorly preserved Katosira, and “Procer ith ium?” volgens e is represented by a mixture of several spe-
cies belonging to different genera: several zygopleurid species, the rissoids Boreomica undulata and Bralitzia.
Shells of P. vo l g en s e in the P.A. Gerasimov’s collection from the Craspedites nodiger Zone are described as
Laevipleura sp.
Keywords: Gastropoda, Procerithiidae, Rissoidae, Zygopleuridae, Boreomica, Laevipleura, Jurassic, Creta-
ceous, Europe, Russia
DOI: 10.1134/S0031030117130032
INTRODUCTION
The new genus Boreomica includes several species
occurring in the Jurassic and Cretaceous beds of
Europe and plays a significance role in assemblages
from the Middle–Upper Jurassic of the European part
of Russia. The earliest representatives were described
here by Gründel in the Lower Bathonian Oraniceras
besnosovi Zone of the Sokurskii quarry (Saratov)
under the name Laevipleura sp. (Upper Bajocian …,
2004, p. 26, pl. 9, figs. 1, 2). Callovian records were
first described by Gerasimov (1955) as Buvignieria val-
finensis (Guirand et Ogérien, 1865). Subsequently,
they were assigned to the new species Rissoina exigua
(Gerasimov, 1992). Then, this species was referred to
the genera Glosia (Guzhov, 2004, 2006) and Laevi-
pleura (Gründel and Mitta, 2013). I collected exten-
sive Kimmeridgian and Volgian material referred to a
species known from the Jurassic of the Novaya Zemlya
Archipelago under the name Eulima undulata Tull-
berg, 1881, which was later redescribed and included
in the genus Hudlestoniella (Kaim et al., 2004).
Below, the establishment of a new genus is substan-
tiated; its taxonomic position, species composition,
stratigraphical and geographical distribution, and also
convergent Zygopleuroidea occurring in the Jurassic
and Cretaceous of European Russia are discussed.
The type specimens considered in the present
paper are transferred to the Borissiak Paleontological
Institute of the Russian Academy of Sciences, Mos-
cow (PIN), collection nos. 4863 (P.A. Gerasimov’s
material) and 4814 (original material).
SYSTEMATIC PALEONTOLOGY
Family Rissoidae Gray, 1847
Genus Boreomica Guzhov, gen. nov.
Etymology. From the Latin boreas (north
wind) and arbitrary combination of letters; feminine
gender.
Type sp e c i e s. Rissoina exigua (Gerasimov,
1992); Middle Jurassic, Middle Callovian; European
Russia.
D i a g n o s i s. Shell small, turriculate beginning
from conical protoconch consisting of 3.5 whorls cov-
ered with microornamentation formed of chaotically
arranged densely spaced tubercles. Boundary between
protoconch and teleoconch manifested in changes in
ornamentation, development of ridges. Teleoconch

1376
PALEONTOLOGICAL JOURNAL Vol. 51 No. 13 2017
GUZHOV
composed of several whorls ranging from flattened to
convex, their profile determined by surface ornamen-
tation. Ornamentation usually represented by ridges,
less frequently, spiral undulae. Ridges covering teleo-
conch whorls up to shell tip; less frequently, disap-
pearing on later whorls. Last teleoconch whorl round,
without basal–palatal bend. Aperture oval, elevated,
angular posteriorly and rounded anteriorly. External
lip not thickened.
Species composition. Type species,
B. caleptra (Gründel, 1975) from the Upp er Ba jo-
cian–Bathonian of Germany and Poland; B. undulata
(Tullberg, 1881) from the Upper Kimmeridgian–Vol-
gian of European Russia; B. recta (Destombes, 1983)
from the Lower Albian Douvilliceras mammillatum
Zone of France; and ?B. pura (Gr ündel, 1975) from
the Bathonian of Poland.
C o m p a r i s o n. The new species differs from
other genera of the family Rissoidae in the combina-
tion of morphological characters: the protoconch is
ornamented with tubercles or strokes, the teleoconch
is mostly with a rough collabral ornamentation and
aperture rounded anteriorly and angular posteriorly,
without a thickened external lip. Boreomica resembles
Rissoininae mostly in the ornamentation and Risso-
inae, in the aperture.
Boreomica differs from Rissoina, which was previ-
ously considered to include the type species of the new
genus (Gerasimov, 1992), in the protoconch orna-
mentation composed of chaotically arranged micro-
scopic tubercles or radially diverging strokes, in the
oval aperture angular posteriorly and rounded anteri-
orly, with a thin external lip. The protoconch of Risso-
ina is usually smooth, less often, ornamented with rows
of tubercles and strokes or with a pitted surface. In
extant members of Rissoina, the aperture D-shaped,
angular anteriorly and posteriorly, usually with a
thickened external lip shaped as varices.
R e m a r k s. A shell figured by Gründel et al.
(2010, pl. 4, figs. 12, 13; from an erratic boulder with a
Bathonian fauna) seems interesting in regard to the
diagnosis of the genus. The shell apparently has a
complete aperture, with the anteriorly curved external
lip. The anterior margin of the aperture is round, with-
out a trace of a basal canal. In our material such a cur-
vature has not been recorded.
Probably, Boreomica includes the species Hud-
lestoniella pura Gründel, 1975, which is very similar in
shell structure to B. caleptra, differing from it in the
absence of a collabral ornamentation.
Boreomica exigua (Gerasimov, 1992)
Buvignieria valfinensis: Gerasimov, 1955, p. 183 (pars), pl. 40,
fig. 1.
? Fusus sp. no. 1: Yamnichenko, 1987, p. 127, pl. 16, figs. 11
and 12.
Rissoina exigua: Gerasimov, 1992, p. 67, pl. 18, figs. 1–4;
Gerasimov et al., 1996, pl. 23, fig. 2.
H o l o t y p e. PIN no. 4863/182, Russia,
Kostroma Region, Manturovskii District, right bank
of the Unzha River near the village of Usol’e; Middle
Callovian (figured by Gerasimov, 1992, pl. 18, fig. 2;
refigured here Fig. 1c).
D e s c r i p t i o n. The shell is small (3–6.6 mm
high), consists of 3.5 whorls of the protoconch and up
to six flattened whorls of the teleoconch. The proto-
conch is conical, its ornamentation is composed of
numerous tubercles, which are sometimes fused in
short strokes. The teleoconch ornamentation is com-
posed of opisthocyrt or opisthocline–opisthocyrt
ridges, varying in number from 10 to 22 p er whorl. The
ridges are present up to the shell tip or become
smoother during. The aperture is rounded teardrop-
shaped, tapering posteriorly and rounded anteriorly,
both lips are thin.
Composition. Two subspecies: B. exigua exi-
gua and B. exigua arenosa subsp. nov.
Let us consider morphological and ecological fea-
tures based on which the subspecies are established.
Ecological distinctions: B. exigua exigua only
occurs in argillaceous deposits, whereas B. exigua
arenosa comes mostly from more coarse-grained
sandy rocks, although it has also been recorded in
clays and aleuritic clays. However, the shells of the
subspecies collected by me from clays are usually con-
fined to eroded horizons and show traces of transpor-
tation. An exception is provided by shells from aleu-
ritic clays near the village of Khvadukasy, probably
buried in sediments inhabited by them.
Morphological distinctions: B. exigua arenosa is
larger (6–6.6 against 3 mm long), with a longer teleo-
conch (6 against 4.5 mm long), than in B. exigua exi-
gua (Fig. 2). The large size is attributable not only to
the longer shell, but also to the greater diameter of
contemporaneous whorls. The ornamentation and its
changes in ontogeny of B. exigua arenosa vary widely:
the number of ridges per whorl ranges from 10 to 22,
with the mean values from 12 to 18, depending on pop-
ulation; the ridges are high or weak and become
smoother towards the shell tip. B. exigua exigua is
highly stable in morphology: 11 or 12 high ridges per
whorl, absence of smoothing or weakening of collabral
ornamentation, and in general more slender shells
(20°–22° versus 20°–28° in B. exigua exigua).
Comparison. B. exigua exigua differs from the
morph of the species B. undulata from argillaceous
deposits in the wider ridges with a gentle outline. A
comparison of B. exigua arenosa and B. undulata from
coarse-grained deposits is impossible because of scar-
city of such specimens in the second species.
R e m a r k s. Describing the species, Gerasimov
(1992) indicated an erroneous locality of the holotype
(1992, p. 67): Upper Oxfordian clays from a borehole
“about 10 km west of the former village of Khimki in
Moscow.” In the description, the holotype has
no. 1659; in the plate caption, Gerasimov gave

PALEONTOLOGICAL JOURNAL Vol. 51 No. 13 2017
ON NEW JURASSIC RISSOOIDEA AND ZYGOPLEUROIDEA 1377
nos. 1855 and 1859–1861 to the original specimens,
without mentioning which numbers correspond to
particular specimens. At the same time, he designated
the shell shown in fig. 2 (Gerasimov, 1992, p. 162) as
“holotype 1659.” The holotype is attributed to
“a quarry near the village of Glinki in the Kromskoi
District of the Orel Region,” dated Middle Callovian.
Other shells (Figs. 1, 3, 4) are attributed to the core of
a borehole drilled in the Uglichskii District of the
Yaroslavl Region. The shell shown in pl. 18, fig. 3 and
refigured later (Gerasimov et al., 1996, pl. 23, fig. 2),
with indication that it comes from the Middle Callo-
vian of a quarry near the village of Glinki.
When working with the negatives of the type speci-
mens and Gerasimov’s collection, I revealed confu-
sion of localities and collection numbers. The negative
of the type specimen shown in pl. 18, fig. 4 (Gerasi-
mov, 1992) is labeled “Uglichskii District of the Yaro-
slavl Region, borehole. 501,” whereas in the collec-
tion, it is found in a tube under nos. 1865 and 46 and
labeled “from the right bank of the Unzha River near
the village of Usol’e.” In both cases, the specimen is
dated Middle Callovian. In the same tube, there is the
specimen shown in pl. 18, fig. 2. In its negative, the
same locality as in the label is specified. The specimen
shown in pl. 18, fig. 3 is found in a tube under no. 47
and label that reads “right bank of the Unzha River
near the town of Makar’ev <…> J3cl2.” Its negative is
not labeled. The type specimen shown in pl. 18, fig. 1
has not been found. In its negative, the point of sam-
pling is borehole 501 in the Uglichskii District. For
clearness, these data are given in Table 1.
This species was first described by Gerasimov as
Buvignieria valfinensis (Guirand et Ogérien). The
specimen figured (Gerasimov, 1955, pl. 40, fig. 1) is
attributed to the Lower Oxfordian of the Unzha River
Fig. 1. Refigured originals from P.A. Gerasimov’s negatives and paratypes from the collection of W.H. Hudleston. The originals
were figured in the following publications (square brackets contain the name of species in the reference cited): (a) Hudleston,
1892, pl. 19, fig. 5 [as Pseudomelania burtonensis]; (c–j) Gerasimov, 1992: (c) pl. 18, fig. 2 [Rissoina exigua]; (d) pl. 18, fig. 3 [Ris-
soina exigua]; (e) pl. 18, fig. 1 [R. exigua]; (f) pl. 18, fig. 4 [R. exigua]; (h) pl. 18, fig. 39 [Hudlestonella caleptra]; (i) pl. 24, fig. 15
[Procerithium (Plicacerithium) volgense]; (k) pl. 24, fig. 14 [Pr. (Pl.) volgense]; (l) pl. 14, fig. 15 [Pr. (Pl.) volgense]. (a, b) Hudleston-
iella burtonensis (Hudleston, 1892), Great Britain, Dorset, coast near the village of Burton Bradstock; Upper Bajocian, Garanti-
ana garantiana Zone: (a) lectotype SM J6880 (6.5-mm-high shell); (b) paratype (6.5-mm-high shell); (c, d) Boreomica exigua
exigua (Gerasimov): (c) holotype PIN, no. 4863/182 (3.5-mm-high shell), village of Usol’e; Middle Callovian; (d) specimen
PIN, no. 4863/183 (3.2-mm-high shell), town of Makar’ev; Middle Callovian; (e) Boreomica exigua (Gerasimov), lost paratype
(shell height not known), ?Yaroslavl Region, Uglichskii District, from a borehole; Middle Callovian; (f) Boreomica exigua arenosa
subsp. nov., specimen PIN, no. 4863/184 (3.2-mm-high shell), village of Usol’e; Middle Callovian; (g–i) Laevipleura sp.:
(g, h) Zigopleuridae gen. ind., lost specimens, Belgorod Region, Shebekinskii District, borehole near Shebekino; Lower Batho-
nian; (i–k) Zygopleuridae gen. ind., Moscow, Suvorovskii Park; Upper Volgian Substage, Kachpurites fulgens Zone: (i) ?Laevi-
pleura sp., specimen PIN, no. 4863/85 (3.7-mm-high fragment); (j) ?Bralitzia sp., specimen PIN, no. 4863/79 (2.8-mm-high
fragment); (k) ?Zygopleura sp., specimen PIN, no. 4863/84 (8.2-mm-high fragment); (l) ?Boreomica undulata (Tul lberg , 1881 ),
lost specimen, Yaroslavl Region, Rybinskii District, right bank of the Volga River near the village of Gorodok; Upper Volgian
Substage, Virgatites virgatus Zone.
(a) (b) (c) (d)
(e) (f)
(g)
(h) (i) (j) (k) (l)

1378
PALEONTOLOGICAL JOURNAL Vol. 51 No. 13 2017
GUZHOV
near the village of Polovchinovo. In the text (Gerasi-
mov, 1955, p. 183), two shells from the Lower Oxford-
ian of the Nerskaya River near the village of Gubino
and the Unzha River near the village of Usol’e. The
specimens from Polovchinovo and Gubino have not
been found, whereas the type material of B. exigua
(holotype and paratype PIN, no. 4863/184) come
from under the village of Usol’e and are dated by Ger-
asimov as Middle Callovian. According to the label,
the material from Usol’e was collected by Gerasimov
in 1951, that is, it had already been obtained by 1955,
when the study was published. In his monograph
(Gerasimov, 1992), records of “Rissoina exigua” from
the Lower Oxfordian are not mentioned. As for me,
Boreomica from the Lower and Middle Oxfordian are
also not known. In the case of Polovchinovo and
Fig. 2. Comparison of shells of Boreomica exigua exigua and B. exigua arenosa. All shells are at the same scale, ×10. The differences
between subspecies in shell size and whorl diameter are evident. The holotype of B. exigua occupies an intermediate position
between morphs, somewhat closer to the shells referred to B. exigua exigua. B. exigua exigua, in specimen PIN, no. 4814/225, gray
contour in Figs. 4a and 4g; in specimen PIN, no. 4814/222, gray contour in Figs. 4b and 4c; in holotype PIN, no. 4863/182, gray
contour in Fig. 4e, black contour in Fig. 4g. B. exigua arenosa: in holotype of PIN, no. 4814/213, black contour in Fig. 4a; in spec-
imen PIN, no. 4814/219, black contour in Figs. 4b, 4e, and 4f, gray contour in Fig. 4d; in specimen PIN, no. 4814/216, black
contour in Figs. 4c and 4d; in specimen PIN, no. 4863/184, gray contour in Fig. 4f. Imposition: (a–c) contour of B. exigua exigua
(gray) on B. exigua arenosa (black); (d) contour of two shells of B. exigua arenosa on each other; (e) contour of the holotype on
B. exigua arenosa; (f) juvenile paratype of B. exigua on B. exigua arenosa; (g) holotype on “typical” B. exigua exigua. For clearness,
some contours are inverted.
(a) (b)
(c) (d)
(e) (f)
(g)
Table 1. Localities of the type specimens of Boreomica exigua (Gerasimov)
Specimen, no. Gerasimov, 1992 Gerasimov et al., 1996 Point of sampling
– pl. 18, fig. 1—borehole 501,
Uglichskii District
––
PIN, no. 4863/182 pl. 18, fig. 2; quarry near village
of Glinki
– Right bank of Unzha River
near village of Usol’e
PIN, no. 4863/183 pl. 18, fig. 3; borehole 501,
Uglichskii District
pl. 23, fig. 2; quarry near village
of Glinki
Right bank of Unzha River
near town of Makar’ev
PIN, no. 4863/184 pl. 18, fig. 4; borehole 501,
Uglichskii District
– Right bank of Unzha River
near village of Usol’e

PALEONTOLOGICAL JOURNAL Vol. 51 No. 13 2017
ON NEW JURASSIC RISSOOIDEA AND ZYGOPLEUROIDEA 1379
Usol’e, the initial dating of shells was probably in
error. The specimen from Gubino was probably rede-
scribed later as “Buvignieria ? nerskajensis Gerasimov,
1992” (Gerasimov, 1992, p. 69) and, subsequently,
redetermined as a juvenile fragment of Novoselkella
(Guzhov, 2017).
O c c u r r e n c e. Lower and Middle Callovian of
the Russian Plate.
M a t e r i a l. P.A. Gerasimov’s collection: Middle
Callovian1 (village of Elat’ma, one specimen; village
of Byakovo, one specimen; town of Makar’ev, four
specimens; village of Usol’e, three specimens; bore-
hole, Puchezhskii District, one specimen; village of
Fokino, three specimens2; village of Kulikovka, one
1 specimen; borehole, Uglichskii District, four spec-
imens).
Boreomica exigua exigua (Gerasimov, 1992)
Plate 1, figs. 11–14, Plate 2, fig. 1
Rissoina exigua: Gerasimov, 1992, p. 67, pl. 18, figs. 2 and 3;
Gerasimov et al., 1996, pl. 23, fig. 2.
Glosia exigua: Guzhov, 2006, pp. 35–36, figs. 2b and 3a;
Objects …, 2012, pl. 34, fig. 10.
H o l o t y p e. The same as in the species.
1A part of the material of B. exigua dated by P.A. Gerasimov as
the Middle Callovian may come from the Lower Callovian.
2Judging from the preservation, one shell comes from the Kos-
moceras jason Zone, Kosmoceras medea Subzone.
D e s c r i p t i o n (Figs. 1c, 1d). The shell is small,
up to 3 mm high (shells transitional to B. exigua
arenosa are up to 3.6 mm high), consists of 3.5 whorls
in the protoconch and up to 4.5 flattened whorls in the
teleoconch. The protoconch is conical, its ornamenta-
tion is composed of numerous tubercles which are
occasionally fused into short strokes. The teleoconch
ornamentation consists of high opisthocyrt ridges well
developed up to the shell tip, 11–12 per whorl. The
aperture is oval, pointed posteriorly and rounded
anteriorly; both lips are thin.
C o m p a r i s o n. For differences from B. exigua
arenosa, see description of the species.
R e m a r k s. The material comes from clays and
aleuritic clays.
O c c u r r e n c e. Lower and Middle Callovian of
the Russian Plate.
M a t e r i a l. Lower Callovian, Proplanulites koe-
nigi Zone, Kepplerites curtilobus Subzone: Mikhai-
lovskii mine (four specimens). Middle Callovian, Kos-
moceras jason Zone, Kosmoceras jason Subzone: village
of Konyushino (1327 specimens); above Kosmoceras
medea Subzone: village of Fokino (ten specimens).
Boreomica exigua arenosa Guzhov, subsp. nov.
Plate 1, figs. 2–10
Rissoina exigua: Gerasimov, 1992, p. 67, pl. 18, fig. 4.
Glosia exigua: Guzhov, 2004, p. 542, text-fig. 13.
Glosia sp. 1: Guzhov, 2006, pp. 35–36, text-fig. 2a.
Fig. 3. Stratigraphical and geographical positions of records of Boreomica: (1) Bajocian; (2) Bathonian; (3) Callovian; (4) Oxford-
ian; (5) Kimmeridgian; (6) Volgian; (7) Albian. Records in the Oxfordian of the Novaya Zemlya Archipelago and Volgian Stage
of the Timan Region, questionable.
750 km
1
2
3
4
5
6
7

1380
PALEONTOLOGICAL JOURNAL Vol. 51 No. 13 2017
GUZHOV
Laevipleura exigua: Gründel and Mitta, 2013, p. 116, pl. 5,
figs.10–15.
E t y m o l o g y. From the Latin arenosus (sandy).
H o l o t y p e. PIN no. 4814/213, Russia, Kostroma
Region, Manturovskii District, gully on the right bank
of the Unzha River near the village of Znamenka;
Lower Callovian, Sigaloceras calloviense Zone, Sigalo-
ceras calloviense Subzone (Pl. 1, fig. 9).
D e s c r i p t i o n (Fig. 1f). The shell is small (up to
6.6 mm high), consists of 3.5 whorls of the protoconch
and up to six flattened whorls of the teleoconch. The
teleoconch ornamentation is composed of opisthocyrt
or opisthocline–opisthocyrt ridges. The number,
thickness, and prominence of ridges vary widely in dif-
ferent specimens. They vary in number from ten to 22,
usually from 12 to 16 per whorl. The ridges can be
Fig. 4. Localities of Boreomica: (1) Mikhailovskii mine (Kursk Region, Zheleznogorskii District, western wall of the Mikhai-
lovskii mine); (2) village of Fokino (Bryansk Region, Dyat’kovskii District, clay quarry near the village of Fokino); (3) village of
Byakovo (Tula Region, Venevskii District, quarries west of the village of Byakovo); (4) village of Elat’ma (Ryazan Region, Kasi-
movskii District, right bank of the Oka River near the village of Elat’ma); (5) quarry no. 7-2bis EFR (Moscow Region,
Voskresenskii District, quarry no. 7-2bis of the Egor’evskii phosphoritic mine near the village of Ostashovo); (6) quarry no. 9
EFR (the same region, west of the village of Fosforitnyi); (7) village of Eganovo (Moscow Region, Ramenskii District, quarry
near the village of Eganovo); (8) village of Mil’kovo (Moscow Region, Lyuberetskii District, right bank of the Moskva River near
the village of Mil’kovo); (9) Brateevo (Moscow, Brateevo District, right bank of the Moskva River); (10) Suvorovskii Park (Mos-
cow, Kuntsevo District, gully in the Suvorovskii Park, right bank of the Moskva River); (11) borehole in the Uglichskii District
of the Yaroslavl Region; (12) village of Konyushino (Yaroslavl Region, Rybinskii District, outcrops on the Ioda and Cheremukha
rivers near the village of Konyushino); (13) village of Chermenino (Kostroma Region, Kologrivskii District, right bank of the
Unzha River upstream from the village of Chermenino); (14) village of Ileshevo (the same place, right bank of the Unzha River
near the village of Ileshevo); (15) village of Burdovo (the same place, right bank of the Unzha River near the village of Burdovo);
(16) village of Znamenka (Kostroma Region, Manturovskii District, gullies on the right bank upstream from the village of Zna-
menka); (17) town of Manturovo (the same place, right bank of the Unzha River vicinity of the town of Manturovo, downstream
from the railway bridge); (18) village of Ivkino (the same place, gully on the right bank of the Unzha River near the village of
Iv kin o); (19) (th e sam e pl ace , ri ght ban k of the Unz ha R iver nea r th e vi lla ge o f Us ol’ e); (20 ) town of M aka r’e v (Ko st roma Reg ion,
Makar’evskii District, right bank of the Unzha River in the vicinity of Makar’ev); (21) borehole in the Puchezhskii District of the
Ivanovo Region; (22) village of Khvadukasy (Republic of Chuvashia, Krasnochetaiskii District, gully in the village of Khvadu-
kasy); (23) village of Kulikovka (Nizhny Novgorod Region, Pil’nenskii District, Medyana River near the village of Kulikovka);
(24) village of Murzitsy (Nizhny Novgorod Region, Sechenovskii District, quarry near the village of Murzitsy); (25) village of
Gorodishchi (Ulyanovsk Region, Ulyanovsk District, right bank of the Volga River near the village of Gorodishchi); (26) Saratov
(quarry near the Sokurskii Highway).
Novgorod
Unzha River
Kostroma
Volga River
Volga River
Vyatka River
Nizhny Novgorod
Moscow
Oka River
Ryazan
Ulyanovsk
Saransk
Desna River
Bryansk
Zheleznogorsk
Don River
Kursk Voronezh Saratov
Seim River
1
2
3
4
5, 6
7
8
9
10
11
12
13
14, 15
16, 17
18, 19
20
21
22
23
24
25
26
V
e
t
l
u
g
a
R
i
v
e
r
S
u
r
a
R
i
v
e
r

PALEONTOLOGICAL JOURNAL Vol. 51 No. 13 2017
ON NEW JURASSIC RISSOOIDEA AND ZYGOPLEUROIDEA 1381
sharp up to the shell tip, but usually become weaker
with the shell growth, sometimes completely
smoothed on the last whorl or halfwhorl of the shell.
Some specimens display microscopic spiral undula-
tion. The aperture is oval, pointed posteriorly and
rounded anteriorly; both lips are thin.
V a r i a t i o n. The assemblage from the gully near
the village of Znamenka, Sigaloceras calloviense Zone
(about 4000 specimens). Although the teleoconch
angle varies considerably, from 20° to 28° (see Pl. 1,
figs. 3, 6), this variation does not look prominent. The
collabral ornamentation is what determines the visual
diversity of forms of B. exigua arenosa. The most
widely varying characters are the density and relief of
ridges. Plate 1, figs. 2, 3, and 9 show shells, which can
be assigned to the prevailing morphological norm.
They have from 12 to 16 more or less developed higher
or lower ridges, which are retained up to the end of the
shell growth. In the shells shown in figs. 6 and 7 of
Plate 1, the ridges are smoothed towards the aperture;
in other shells (Pl. 1, figs. 4, 8), ridges are most widely
spaced (11 per whorl); in fig. 8, they are rather promi-
nent up to the shell tip, while in fig. 4, they are
abruptly and completely smoothed on the last whorl.
Plate 1, fig. 5 shows a shell with the most densely
spaced ridges (18 per whorl). In longitudinal profile,
the ridges are flattened from above, forming the out-
line of whorls, although the surface between ridges is
convex. In addition, the ridges vary somewhat in ori-
entation from opisthocyrt, with the maximum devia-
tion in the middle of the lateral face, to opisthocline–
opisthocyrt, with the maximum deviation somewhat
higher that the middle of the lateral face. In the sam-
ple, shells with opisthocyrt ridges prevail.
The assemblage collected there, from the Cadoc-
eras elatmae Zone is represented by 70 specimens.
Plate 1, fig. 10 shows a shell typical for this assem-
blage. The shells occur in clays in accumulation of sev-
eral specimens and, in burial, lack the initial whorls or
eroded. Some specimens are surrounded by a fringe of
iron oxides. All the above is evidence that the material
was reworked. The teleoconch angle of shells is usually
22°–23°, with the full range of 20°–26°. All shells have
ridges throughout the teleoconch extent; in the over-
whelming majority of specimens, the ridges are high
and distinctly outlined; only a few specimens have an
initially weakened ornamentation. The ornamentation
is rich, with 16–18 ridges per whorl. A small propor-
tion (less than 10%) have 14–15 ridges. In addition
there are more densely ribbed shells, having up to
22 ridges per whorl. The opisthocline–opisthocyrt ori-
entation of ridges prevails. The assemblage from clays of
the same zone exposed in a neighboring gully is con-
fined to allochtonous accumulations with the gastro-
pods “Pseudomelania fokinen sis” Gerasimov and Crypt-
aulax salebrosus (Yamnichenko). Shells of B. exigua
arenosa differ from the contemporaneous assemblage
in the more widely spaced ridges (14–16 per whorl)
and the greater proportion of specimens with weak-
ened or smoothed ornamentation.
Among B. exigua arenosa from fine–medium-
grained sandstone of Burdovo and Ileshevo (Proplan-
ulites koenigi Zone, 18 specimens), well-ornamented
shells with 14–15, less often, 16–17 ridges per whorl
prevail. The ridges are opisthocyrt and opisthocline–
opisthocyrt. One shell has a weak ornamentation. Shells
from aleuritic fine-grain sandstone of the town of Man-
turovo (Sigaloceras calloviense Zone, 12 specimens)
vary widely in the curvature, extent of smoothing, and
density of ridges, but differ from other samples in the
prevalence of coarse-ribbed forms with 12 ridges per
whorl (in general ranging from 10 to 17 per whorl).
Shells from aleuritic clays near the village of Khvadu-
kasy usually have 14–16 ridges per whorl.
C o m p a r i s o n. For differences from B. exigua
arenosa, see description of the species.
R e m a r k s. The material comes from aleuritic
clays, fine–medium-grained sand and sandstone,
aleuritic sand, and sandstone of the Lower Callovian,
medium–coarse-grained sandstone of the Middle
Callovian.
O c c u r r e n c e. Lower and Middle Callovian of
the Russian Plate.
M a t e r i a l. Lower Callovian, Paracadoceras elat-
mae Zone: village of Znamenka (92 specimens);
Cadochamoussetia subpatruus Zone, Cadochamousse-
tia surensis Subzone: village of Khvadukasy (28 speci-
mens); Proplanulites koenigi Zone: village of Burdovo
(two specimens); Kepplerites curtilobus Subzone: vil-
lage of Burdovo (11 specimens), village of Ileshevo
(five specimens); Sigaloceras calloviense Zone: village
of Znamenka (one specimen), town of Manturovo
(one specimen); Sigaloceras calloviense Subzone: vil-
lage of Znamenka (3875 specimens), town of Man-
turovo (12 specimens); Catasigaloceras enodatum Sub-
zone: village of Burdovo (three specimens). Middle
Callovian, Kosmoceras jason Zone, Kosmoceras medea
Subzone: village of Chermenino (one specimen).
Boreomica undulata (Tullberg, 1881)
Plate 2, figs. 2–7, Plate 3, figs. 1–4
Eulima undulata: Tul lberg, 1881, p. 10 , pl. 2, figs. 2 6 and 27.
? Procerithium? volgense: Gerasimov, 1955, p. 189, pl. 40,
figs. 13 and 14; Gerasimov, 1969, p. 49.
? Procerithium (Plicacerithium) volgense: Gerasimov, 1992,
p. 78 (pars), pl. 14, fig. 15.
Hudlestoniella undulata: Kaim et al., 2004, p. 254, text-fig. 11;
Hryniewicz et al., 2015, text-fig. 9B.
L e c t o t y p e. Museum of Natural History in
Stockholm (Naturhistoriska Riksmuseet in Stock-
holm), no. Mo1182: Russia, Novaya Zemlya Archipel-
ago, Yuzhnyi Island, Bakan Bay (=Skodde Bay);
Upper Volgian Substage, Craspedites okensis Zone.
Description. The species is polymorphic, like
the above described B. exigua, and divided into several
morphological groups dwelling in different condi-

1382
PALEONTOLOGICAL JOURNAL Vol. 51 No. 13 2017
GUZHOV
1
2
8
7
6
11a
11b 11c 13b
14
13a
12b
12a
45
10
9b
9a
3a 3b
Plate 1

PALEONTOLOGICAL JOURNAL Vol. 51 No. 13 2017
ON NEW JURASSIC RISSOOIDEA AND ZYGOPLEUROIDEA 1383
Explanation of Plate 1
Scale bar, 100 μm. For other figures, shell size is given.
Fig. 1. Boreomica sp. 1, s pecim en PIN, n o. 4814/211 (2 .4-mm -high shel l), Sara tov; L ower Bath onia n, Oraniceras besnosovi Zone.
Figs. 2–10. B. exigua arenosa subsp. nov., village of Znamenka; Lower Callovian: (2–9) Sigaloceras calloviense Zone, Sigaloceras
calloviense Subzone: (2) specimen PIN, no. 4814/212 (5-mm-high shell); (3) holotype PIN, no. 4814/213 (4.9-mm-high shell);
(4) specimen PIN, no. 4814/214 (4.2-mm-high shell); (5) specimen PIN, no. 4814/215 (5.5-mm-high shell); (6) specimen PIN,
no. 4814/216 (5.6-mm-high shell); (7) specimen PIN, no. 4814/217 (5.7-mm-high shell); (8) specimen PIN, no. 4814/218
(4.4-mm-high shell); (9) specimen PIN, no. 4814/219 (4.4-mm-high shell); (10) Paracadoceras elatmae Zone: specimen PIN,
no. 4814/220 (4.2-mm-high shell).
Figs. 11–14. B. exigua exigua (Gerasimov, 1992), Ioda River, village of Konyushino; Middle Callovian, Kosmoceras jason Zone,
Kosmoceras jason Subzone: (11) specimen PIN, no. 4814/221: (11a) shell, apertural view (2.6 mm high), (11b) protoconch,
(11c) microornamentation of the protoconch; (12) specimen PIN, no. 4814/222 (2.7-mm-high shell); (13) specimen PIN,
no. 4814/223: (13a) protoconch, (13b) microornamentation of the protoconch; (14) specimen PIN, no. 4814/224, protoconch,
top view.
tions. The original material comes from clays and dis-
plays the following features:
The shell is small (up to 3.2 mm high), consists of
3.5 whorls of the protoconch and up to five slightly
convex whorls of the teleoconch. The protoconch is
conical, divided into embryonic and larval stages (pro-
toconchs I and II). Protoconch I occupies half whorl,
covered with chaotic cellular ornamentation. The
ornamentation of protoconch II is usually initially
formed of fan-shaped strokes and, then, it is replaced
by small chaotically arranged tubercles, which are
retained only below on the last halfwhorl. Some proto-
conchs have only the second type of ornamentation.
The teleoconch angle is 20°–24°; the ornamentation
is composed of high sharp opisthocyrt ridges usually
well developed up to the end of the shell growth, 12–14
(rarely up to 16) per whorl. Sometimes, ridges are
smoothed on the last whorl. The aperture is oval,
pointed posteriorly and rounded anteriorly; both lips
are thin.
The type material of the species belongs to a differ-
ent morph. The lectotype comes from peloid lime-
stones. It is 4.5 whorls long and 5.4 mm high, as fol-
lows from the scale piece accompanying the shell
(Kaim et al., 2004, text-fig. 11B). This specimen lacks
a protoconch and the completeness of the teleoconch
is uncertain (on the substrate, its aperture is turned
inside). The ornamentation consists of 12 opisthocyrt
ridges, which are well developed up to the shell tip.
In sandstone of the Craspedites nodiger Zone, a sin-
gle imprint has been found, which belongs to the same
morph as the lectotype. This is a 6.7-mm-high teleo-
conch fragment consisting of four whorls covered with
slightly opisthocyrt ridges, 16 per whorl.
V a r i a t i o n. The shells display spiral microorna-
mentation (Kaim et al., 2004, fig. 11C6), which is
probably stochastically arranged (as in B. exigua exi-
gua, see Pl. 2, fig. 4) and lacks taxonomic or diagnostic
significance. A few shells (from the village of Ivkino)
have relatively dense collabral ornamentation, up to
16–20 ridges. A considerable increase in ridge density
is usually restricted to one whorl, which is probably a
deviation. In the sample from the village of Ivkino,
shells with smoothed ridges are very rare, whereas in
the village of Gorodishchi, they are much more fre-
quent. In the material from the village of Murzitsy,
shells with 14 ridges per whorl prevail, varying in this
character from 12 to 16. Shells with smoothed orna-
mentation have not been recorded.
C o m p a r i s o n. See in description of B. exigua.
Remarks. Tullberg (1881, pl. 2, fig. 27) figured
one more specimen, which probably does not belong
to our species, since it begins from the structure
resembling a transaxial heterostrophic protoconch.
The description provided by Tullberg contradicts the
figures and the identified original specimen (empha-
sized by italics), i.e., “Much larger than the preceding
species: with nine whorls at a length of 15 mm. The
whorls are more convex, all with distinct rounded lon-
gitudinal ribs and stronger projecting spiral bands. The
aperture is more rounded.” It seems that we deal with
a description of a different species. At the same time,
the author believes that identification of the figure
from work of Tullberg (1881, pl. 2, fig. 26) with the
shell figured by Kaim et al. (2004, text-fig. 11B) is
rather reliable. Unfortunately, Kaim did not provide
comment on the recognition of the holotype and other
type specimens used by Tullberg for the establishment
of the species or on the contradictions between the
type and original description. The designation of spec-
imen Mo1882 as the holotype is in error, since from
the original paper, it is evident that the type series con-
sisted of more than one specimen. Therefore, the sta-
tus of the original is corrected here for the lectotype.
The shells presumably assigned to this species and
described by Gerasimov as Procerithium volgense are
discussed below in a special chapter.
Lithologic confinement: clays, peloid limestones,
medium-grained sandstones.
O c c u r r e n c e. Upper Kimmeridgian–Volgian
Stage of the Russian Plate and Novaya Zemlya Archi-
pelago.
M a t e r i a l. Upper Kimmeridgian, Aulacostepha-
nus autissiodorensis Zone, Sarmatisphinctes subborealis
Subzone; village of Murzitsy (769 specimens); Middle
Volgian Substage, Dorsoplanites panderi Zone: village
of Gorodishchi (86 specimens), village of Ivkino

1384
PALEONTOLOGICAL JOURNAL Vol. 51 No. 13 2017
GUZHOV
(526 specimens); Virgatites virgatus Zone, Virgatites
virgatus Subzone: Moscow, Kuntsevo District (one
specimen); Craspedites nodiger Zone, Craspedites
mosquensis Subzone: Moscow, Brateevo District (one
specimen).
Boreomica sp. 1
Plate 1, fig. 1
Laevipleura sp.: Mitta et al., 2004, p. 26, pl. 9, figs. 1 and 2.
D e s c r i p t i o n. The shell is small (up to 3.5 mm
high), has at least four slightly convex whorls of the
teleoconch, which are covered with slightly opistho-
cyrt collabral ridges. The ridges are high and rather
sharp; ontogenetic smoothing has not been recog-
nized. Gründel indicated in the diagnosis that there
were 18 ridges per whorl, although this characteristic
only concerns original GGM-1210-42 (Mitta et al.,
2004, pl. 9, fig. 1). The second original, GGM-1240-
43 (Mitta et al., 2004, pl. 9, fig. 2), has about 12 or
13 ridges per whorl. When examining the doublet
specimens to the paper, it turned out that most of the
shells have 16 ridges per whorl. Thus, the original diag-
nosis does not correspond to available material. The
original description is accompanied by figures of the
most complete and well-preserved shells, while
remaining material is fragmentary and usually strong
eroded. The protoconch and aperture are not known.
R e m a r k s. Lithologic confinement: calcareous
clays (eroded horizons).
O c c u r r e n c e. Lower Bathonian of the Russian
Plate.
M a t e r i a l. Lower Bathonian, Oraniceas bes-
nosovi Zone: Saratov (18 specimens).
Boreomica sp. 2
Plate 3, figs. 6 and 7
D e s c r i p t i o n. Several juvenile shells of differ-
ent preservation, consisting of 3.5 whorls of the proto-
conch and up to two collabrally ornamented whorls of
the teleoconch. The ornamentation is composed of
16 or 17 ridges, which are as sharp as those of Upper
Kimmeridgian B. undulata.
O c c u r r en c e. Upper Oxfordian of the Russian
Plate.
M a t e r i a l. Upper Oxfordian, Amoeboceras serra-
tum Zone, Amoeboceras serratum Subzone: EFR,
quarry 7-2 bis (5 specimens).
Family Zygopleuridae Wenz, 1938
Genus Laevipleura Gründel et Nützel, 1998
Laevipleura sp.
Plate 3, figs. 8–11
Description. The shell is relatively small, slen-
der, its most complete fragment is 9 mm high and con-
sists of eight whorls of the teleoconch. The whorls are
flattened, covered with densely spaced orthocline or
opisthocline ridges, which are 16–18 per whorl. On
early whorls of the teleoconch, the basal–palatal bend
between the lateral side and base is well pronounced.
The shell base lacks a ornamentation. The aperture is
not preserve.
Lithologic confinement: aleuritic clays, medium-
grained sandstones (quartz and glauconitic quartz).
O c c u r r e n c e. Middle and Upper Volgian sub-
stages of the Russian Plate.
M a t e r i a l. Middle Volgian Substage, Virgatites
virgatus Zone, Virgatites virgatus Subzone: Moscow,
Kuntsevo District (two specimens); Craspedites nodi-
ger Zone, Craspedites mosquensis Subzone: village of
Mil’kovo (one specimen).
Two specimens in Gerasimov’s collection come
from the Upper Volgian Substage, Craspedites nodiger
Zone, Craspedites mosquensis Subzone of the Brateevo
District of Moscow.
OTHER GENERA SUGGESTED
FOR THE SPECIES INCLUDED
BY THE AUTHOR IN THE GENUS BOREOMICA
Modern researchers proposed several treatments of
the taxonomic position of species referred by the
author to Boreomica: Glosia Cossmann, 1912
(Destombes, 1983; Guzhov, 2004, 2006), Hudleston-
iella Cossmann, 1909 (Gründel, 1975, 1999; Kaim
et al., 2004; Hryniewicz et al., 2015), Laevipleura
Gründel et Nützel, 1998 (Upper Bajocian …, 2004;
Gründel and Mitta, 2013), and Rissoina d’Orbigny,
1840 (Gerasimov, 1992) (brief comparisons with it
accompany the description of Boreomica). The mor-
Explanation of Plate 2
Scale bar, 100 μm. For other figures, shell size is given.
Fig. 1. B. exigua exigua (Gerasimov, 1992), specimen PIN, no. 4814/225 (3-mm-high shell), Ioda River, village of Konyushino;
Middle Callovian, Kosmoceras jason Zone, Kosmoceras jason Subzone.
Figs. 2–7. Boreomica undulata (Tullberg, 1881): (2–6) village of Ivkino; Middle Volgian Substage, Dorsoplanites panderi Zone:
(2) specimen PIN, no. 4814/226 (2.9-mm-high shell); (3) specimen PIN, no. 4814/227 (3-mm-high shell); (4) specimen PIN,
no. 4814/228 (3.1-mm-high shell); (5) specimen PIN, no. 4814/229: (5a) shell, apertural view (2.6-mm-high), (5b) protoconch,
(5c) microornamentation of the protoconch; (6) specimen PIN, no. 4814/230: (6a) shell (2.7-mm-high), (6b) protoconch,
(6c) microornamentation of the protoconch (arrow points to the beginning of protoconch II); (7) specimen PIN, no. 4814/231,
village of Murzitsy; Upper Kimmeridgian, Aulacostephanus autissiodorensis Zone, Sarmatisphinctes subborealis Subzone:
(7a, 7b) 3.3-mm-high shell, (7c) protoconch, (7d) rudimentary spiral undulation on the teleoconch.

PALEONTOLOGICAL JOURNAL Vol. 51 No. 13 2017
ON NEW JURASSIC RISSOOIDEA AND ZYGOPLEUROIDEA 1385
12a 2b 3a 3b 5a
5c
5b
4b
6b
6a
6c
7d
7c
7b7a
4a
Plate 2

1386
PALEONTOLOGICAL JOURNAL Vol. 51 No. 13 2017
GUZHOV
1
2a
4a
4b3b
3a
2b 2c 67
11
10
9
8
5
Plate 3

PALEONTOLOGICAL JOURNAL Vol. 51 No. 13 2017
ON NEW JURASSIC RISSOOIDEA AND ZYGOPLEUROIDEA 1387
Explanation of Plate 3
Scale bar, 100 μm. For other figures, shell size is given.
Figs. 1–5. Boreomica undulata (Tullberg, 1881): (1–4) village of Murzitsy; Upper Kimmeridgian, Aulacostephanus autissiodoren-
sis Zone, Sarmatisphinctes subborealis Subzone: (1) specimen PIN, no. 4814/231, boundary (arrow) between embryonic and lar-
val stages of the protoconch; (2) specimen PIN, no. 4814/232: (2a, 2b) 3-mm-high shell, (2c) protoconch; (3) specimen PIN,
no. 4814/233: (3a) protoconch, top view, (3b) embryonic stage, boundary with larval shell is uncertain because of lifetime dam-
ages of embryo; (4) specimen PIN, no. 4814/234: (4a) protoconch, top view, (4b) embryonic stage, boundary with the larval shell
(arrow); (5) specimen PIN, no. 4814/235 (silicone cast, 6.8-mm-high shell), Moscow, Brateevo District, Upper Volgian Sub-
stage, Craspedites nodiger Zone, Craspedites mosquensis Subzone.
Figs. 6 and 7. Boreomica sp. 2, quarry 7-2bis EFR; Upper Oxfordian, Amoeboceras serratum Zone, Amoeboceras serratum Subzone:
(6) specimen PIN, no. 4814/236 (1.7-mm-high shell); (7) specimen from K.M. Shapovalov’s collection (Moscow) (1.6-mm-high
shell).
Figs. 8–11. Laevipleura sp.: (8–10) Upper Volgian Substage, Craspedites nodiger Zone, Craspedites mosquensis Subzone: (8) spec-
imen PIN, no. 4863/86 (silicone cast, 8.5-mm-high shell), Moscow, Brateevo District; (9) specimen PIN, no. 4863/87 (silicone
cast, 5-mm-high shell), Moscow, Brateevo District; (10) specimen PIN, no. 4814/237 (silicone cast, 3.5-mm-high shell), village
of Mil’kovo; (11) specimen PIN, no. 4814/238 (2-mm-high shell), Middle Volgian Substage, Virgatites virgatus Zone, Virgatites
virgatus Subzone.
phology of these genera is considered below in detail
for comparison with characters of Boreomica.
Laevipleura. Melania blainvillei Münster, 1844
from the Upper Pliensbachian of Germany was desig-
nated as the type species (Gründel and Nützel, 1998).
In the diagnosis of the genus, it is indicated that the
teleoconch is the same as in Zygopleura Koken, 1892
and the protoconch is conical, consisting of several
whorls, which can be covered with microscopic tuber-
cles and a suprasutural (i.e., positioned at the lower
border of the whorl above the suture) spiral rib. Let us
turn to available figures of shells of L. blainvillei. In all
cases (Nützel and Kießling, 1997; Gründel and Nüt-
zel, 1998; Nützel, 1998; Gründel, 2007; Nützel and
Gründel, 2015), figures show eroded protoconchs,
which preclude revelation of the presence or absence
of microornamentation. The teleoconchs consist of
many convex whorls, the early of which are covered
with a collabral ornamentation, while succeeding
whorls are smooth. In general, the species is charac-
terized by high turriculate shells; their early part
(except for the protoconch) is formed of collabrally
ornamented whorls. Apparently, the authors made a
conclusion about the protoconch ornamentation
based on the figures of Mesostrombus cf. venustus
(Phillips, 1829) provided by Schröder (1995, p. 37,
pl. 6, figs. 18–20, pl. 15, fig. 3), which is only repre-
sented by protoconchs of excellent preservation. Since
these protoconchs come from the same stratigraphic
level as material that was used for the establishment of
the genus Laevipleura, i.e., Upper Pliensbachian
Amaltheenton clays, but from different regions of
Germany (Schröder’s material comes from Ham-
bühren in Lower Saxony, while the specimens of Nüt-
zel come from Bamburgh and Kalchreuth in Bavaria),
the authors assumption that the protoconchs belong to
L. blainvillei. It is also important that L. blainvillei has
a rounded angular bend, which is well pronounced at
the stage of ornamented teleoconch (Nützel, 1998,
pl. 19, fig. R; Nützel and Gründel, 2015, pl. 9, fig. F)
due to abrupt disappearance of ridges, which disap-
pear in later smooth whorls (Nützel and Kießling,
1997, pl. 34, fig. 6; Nützel, 1998, pl. 19, fig. T; Nützel
and Gründel, 2015, pl. 8, figs. L–N, pl. 9, figs. A–D).
At the end of the ornamented part and at the smooth
stages of the shell, spiral undulation is recognized.
Laevipleura has a protoconch without macroorna-
mentation and its teleoconch has well-developed col-
labral ornamentation, which is lost subsequently. This
character is shared by Laevipleura and Boreomica.
However, a number of features clearly distinguish Lae-
vipleura from Boreomica: the teleoconch has a much
greater number of whorls; early whorls have an angular
transition between the lateral side and base, which
then becomes rounded angular. Boreomica is distin-
guished by the relatively small number of whorls in the
teleoconch and always smooth rounded transition
between the lateral side and base.
Glosia. Cossmann (1921) figured the type species
Glosia potamidula (Upper Oxfordian of France), along
with the establishment of the genus, and did not
accompanied it with description. He assigned the fol-
lowing species to this genus: Rissoa vermiformis Coss-
mann, 1885 (Bathonian of France), Glosia cerithialis
Cossmann, 1921 (Sequanian of France), Rissoa pellati
Loriol, 1874 (Sequanian of France), Cingula pupina
Cossmann, 1916 (Barremian of France), and Chem-
nitzia turritelliformis J. Müller, 1851 s ensu Holzapfel,
1888 (Maastrichtian of Germany). In the diagnosis, it is
indicated that the shell is small turriculate, with a rather
long whorl, smooth protoconch, and 8–10 whorls in
the teleoconch covered with obliquely inclined col-
labral ribs and thin dense spiral undulae. In addition,
it is marked that the shell of the type species, which
was the basis for the diagnosis of the genus, vary widely
in ornamentation and outline. The species included in
the genus considerably differ from each other, fre-
quently being beyond the generic diagnosis. The fig-
ures of G. potamidula provided by Cossmann (1921,
pl. 2, figs. 79–82, pl. 3, fig. 7) are of poor quality.
Specimens of G. potamidula shown in figs. 7, 79, and
80 actually have obliquely inclined ridges, and the
largest shells are up to 5 mm high, judging from the
scale bar provided.

1388
PALEONTOLOGICAL JOURNAL Vol. 51 No. 13 2017
GUZHOV
The differences between Boreomica and Glosia
remain uncertain because of the absence of good
descriptions and figures of the type species. In our
opinion, G. potamidula figured by Wenz (1940, p. 754)
actually belongs to Boreomica. Wenz referred to Coss-
mann as the original source of information; however,
he did not figure anything similar. Moreover, in all
previous publications on Jurassic gastropods, such a
figure is not provided; this allows us to treat the figure
as a curiosity. Because of this figure, I previously
determined members of Boreomica as Glosia (Guzhov,
2004, 2006).
Hudlestoniella. The type species Pseudomelania
burtonensis Hudleston, 1892 was described from shal-
low-water carbonate facies, which Hudleston assigned
to the Parkinsonia parkinsoni Zone of the Upper Bajo-
cian (Hudleston, 1892, p. 246, pl. 19, fig. 5). Other
records of this species have not been found in contem-
poraneous carbonate deposits of Western Europe. The
type material (five specimens) was collected in a sec-
tion near the village of Burton Bradstock, apparently,
in Bed 1'O''P1, which contains numerous gastropods
and is characterized by abundant bivalves of the genus
Astarte, including A. obliqua Deshayes (Hudleston,
1887, pp. 31–32). Arkell (1970, pp. 232–233) referred
the beds with Astarte obliqua of the same section to the
Garantiana garantiana Zone. According to Hudleston,
the shell of this species is up to 7 mm high and consists
of nine convex whorls. The upper whorl is described as
smooth (probably worn); three succeeding whorls are
covered with collabral folds; then, there are five
smooth whorls. The teleoconch angle is 30°. At pres-
ent, figures of H. burtonensis are known in GB3D Type
Fossils (see References and Figs. 1a, 1b). It provides
photographs of two specimens from the Sedgwick
Museum of Earth Sciences, one of which, judging
from their labels, is identified as the original figured by
Hudleston and the second possibly belongs to the
same collection and locality and is probably a syntype.
It is plausible that the specimen figured by Hudleston
is the lectotype of H. burtonensis. His photograph dis-
plays a ornamentation of thin, densely spaced, almost
orthocline ridges extending throughout about three
whorls, which are followed by three smooth whorls. In
the paratype of worse preservation, ornamentation is
not preserved; however, the shell size and shape corre-
spond to the lectotype (both specimens are 6.5 mm
high).
Gründel (1975, 1999) assigned the material from
the borehole cores in the territory of Poland and Ger-
many to the type species. Shells presumably come
from aleuritic–argillaceous rocks dated from the Late
Bajocian to Late Bathonian (depending on the bore-
hole). Gründel divided the species into two subspe-
cies, H. burtonensis burtonensis and H. butronensis
caleptra Gründel, 1975. He mentioned that H. burton-
ensis burtonensis is represented by about 300 speci-
mens and the second subspecies, by 250, but he could
not formulate the differences between them. The divi-
sion into subspecies was apparently caused by strati-
graphic heterogeneity; the shells referred to H. burton-
ensis burtonensis are dated Upper Bajocian and H. bur-
tonensis caleptra is dated upper Lower Bathonian–
Upper Bathonian. At present, a more important point
is whether or not the material of Gründel is conspe-
cific to the type species of Hudlestoniella. According to
Gründel, H. burtonensis has a poorly ornamented or
smooth protoconch (all figured protoconchs show an
eroded surface); the border with the protoconch is
marked based on the appearance of collabral orna-
mentation. It is present throughout succeeding 2.5–
3 whorls, but becomes gradually smoother on the last
of them (although it does not disappear in all speci-
mens: see Gründel et al., 2010). Then, there are 1–
1.5 smooth whorls. Thus, the shells from works of
Gründel and Hudleston coincide in the ontogenetic
character of ornamentation; in addition, they did not
indicate the presence of a thickening of the external
lip. However, there are essential differences; according
to Hudleston, collabrally ornamented whorls are fol-
lowed by about five smooth whorls, while the shells
figured by Gründel have at most one and a half. In
addition, H. burtonensis is 6.5 mm high, while accord-
ing to Gründel, the shells of H. burtonensis burtonensis
and H. burtonensis caleptra are at most 3.6 and 5 mm
high, respectively, plus different environmental condi-
tions. It is possible that, according to Gründel, the
smaller size and, hence, the short terminal stage of
smooth whorls in “H. burtonensis” are caused by less
favorable conditions than those in the habitats of
H. burtonensis from the Burton Bradstock section.
However, the combination of morphological and eco-
logical distinctions deserves special attention. As
Gründel's specimens are compared with the photo-
graph of the lectotype of H. burtonensis, the differ-
ences in the character of collabral ornamentation and
the general geometry of the shell are evident. The lec-
totype displays a significant growth of the shell in
diameter in all whorls, whereas Gründel's shells lack
this character. It seems plausible that the identification
of Gründel, which is based exclusively on the similar-
ity in ontogeny of ornamentation is erroneous.
Notwithstanding the similar in ontogeny, Boreom-
ica differs from Hudlestoniella in the teleoconch
whorls growing slowly in diameter and in the whorl
section; in Hudlestoniella, it is teardrop-shaped,
extended and pointed posteriorly. Species of the two
genera strongly differ in the shell proportions; in addi-
tion, Boreomica has a shorter teleoconch (in photo-
graphs of the originals of Hudlestoniella burtonensis, it
consists of eight whorls), and the majority of its spe-
cies have a well-developed collabral ornamentation up
to the shell tip.

PALEONTOLOGICAL JOURNAL Vol. 51 No. 13 2017
ON NEW JURASSIC RISSOOIDEA AND ZYGOPLEUROIDEA 1389
STRATIGRAPHICAL AND GEOGRAPHICAL
DISTRIBUTION OF BOREOMICA
The earliest records of the genus are known from
the boreholes in the vicinity of boundaries of Poland
and Germany, in the area of the Lagoon of Szczecin or
Bay of Szczecin (Polish: Zalew Szczeciński; German:
Stettiner Haff, Oderhaff), and are represented by the
species B. caleptra (Gründel, 1975). Exact strati-
graphic and lithologic binding of the material has not
been provided. Bajocian shells are dated to within the
Upper Bajocian; Bathonian shells, to the upper Lower
Bathonian–Upper Bathonian. At that time, this area
was occupied by an inland sea shelf where the follow-
ing deposits were accumulated: calcareous argilla-
ceous, aleuritic, and sandy–clayey deposits in the
Late Bajocian (mostly sandy deposits were only
during the phase of Parkinsonia schloenbachi); in the
Bathonian, there were mostly calcareous clays and
aleurites (Dayczak-Calikowska and Moryc, 1988;
Epikontinentalny perm …, 1997; The Geology …, 2008).
Younger records of the genus in the Jurassic of foreign
Europe have not been revealed.
On the Russian Plate, Jurassic Boreomica occur in
the following intervals: Lower Bathonian, Lower and
Middle Callovian, Upper Oxfordian, Upper Kimme-
ridgian, Middle and Upper Volgian substages. Lower
Bathonian records are only known in one locality, the
Sokurskii quarry, which is situated in the northern
marginal area of Saratov. The material described by
Gründel under the name Laevipleura sp. (Upper
Bajocian …, 2004) comes from gray aleuritic clays of
the Oraniceras besnosovi Zone. According to our data,
gastropods from this bed are allochtonous, confined
to reworked horizons. In a recent paper, Mitta et al.
(2014) recorded Laevipleura sp. not only in the Oran-
iceras besnosovi Zone, but also in Bed 2 of the Pseudo-
cosmoceras michalskii Zone of the Upper Bajocian.
However, judging from the figures, it remains uncertain
whether or not they belong to the genus Boreomica.
In the Callovian the species B. exigua became
widespread (Gerasimov, 1992). It is divided into two
subspecies, which show different lithologic confine-
ment: B. exigua exigua is recorded in argillaceous
deposits, whereas B. exigua arenosa occurs mostly in
sandy–clayey, aleuritic–sandy, and sandy rocks. The
subspecies are regarded here as a result of ecological dif-
ferentiation of the species. B. exigua arenosa occurs
from the Paracadoceras elatmae Zone to Kosmoceras
jason Zone, whereas B. exigua sensu stricto is recorded
from the Proplanulites koenigi Zone to Kosmoceras jason
Zone and also in the nonstratified Middle Callovian.
In Upper Oxfordian clays (Amoeboceras serratum
Zone) of the Moscow Region, rather rare juvenile
specimens of Boreomica were found.
The Upper Kimmeridgian and Volgian beds have
yielded Boreomica undulata (Tullb erg, 1881). To date,
several localities have been discovered on the Russian
Plate: at the village of Murzitsy (Nizhny Novgorod
Region) from Upper Kimmeridgian calcareous clays
of the Aulacostephanus autissiodorensis Zone; at the
village of Ivkino (Kostroma Region) from Middle Vol-
gian calcareous clays of the Dorsoplanites panderi
Zone (Gavrilov et al., 2008, Bed 3); from calcareous
clays of the same zone at the village of Gorodishchi
(Ulyanovsk Region: Rogov, 2013, Beds 2/2–2/15);
from Upper Volgian sandstone of Moscow, Cras-
pedites nodiger Zone; and others. In addition, it was
recorded in the cores of boreholes drilled in the area of
the Timan Ridge, but without exact dating (Kaim et
al., 2004). The species was originally described from
the Novaya Zemlya Archipelago (Bakan Bay) in bitu-
minous limestones of the Upper Volgian Substage,
Craspedites okensis Zone. The dating of the material
from the Novaya Zemlya Archipelago is confirmed by
the presence of Buchia and ammonites. Tullberg
(1881) reported that this assemblage comes from “dark
gray bituminous limestones.” They have yielded
Aucella keyserlingiana var. obliqua Tullberg, 1881,
presently, Buchia oblique, which is the index species of
the same Buchia Zone and corresponds to the Cras-
pedites okensis Ammonite Zone (Zakharov, 1981).
Based on ammonites, the boulders were referred to the
Kachpurites fulgens Zone (Bodylevsky, 1967). Bodyl-
evsky recognized the K. fulgens Zone on the basis of the
presence of Craspedites (redetermination of ammonites
follows Frebold, 1930): C. cf. fragilis (Trautschold) and
C. (?) cf. jurgens Prigorovsky. Mesezhnikov (1984) also
proposed to divide this part of the Volgian Stage on the
Novaya Zemlya Archipelago into the Kachpurites ful-
gens and Craspedites subditoides zones. However, none
of the publications provided figures of Kachpurites
from the Novaya Zemlya Archipelago. In Rogov’s
opinion, the ammonites figured by Frebold (1930)
belong to Craspedites okensis (d’Orbigny), C. ex gr.
subditoides (Nikitin), and Craspedites sp. juv.; ammo-
nites reported by Hryniewicz et al. (2015, text-fig. 9)
belong to C. okensis. These ammonites are character-
istic of the Craspedites okensis Zone of the boreal scale
and, since the presence of the genus Kachpurites on
the Novaya Zemlya Archipelago is not supported by
facts, it seems more correct to refer the boulders of
“bituminous limestone” to the C. okensis Zone. The
C. okensis Subzone is presently correlated with the
K. fulgens Zone of the Russian Plate (Rogov and
Zakharov, 2009).
In the Cretaceous, Boreomica is represented by the
only species B. recta, which is separated from Jurassic
species by a large time hiatus and occurs in Middle
Albian calcareous clays (Hoplites dentatus Zone) of a
quarry of Bully in France (Destombes, 1983).
The distribution of Boreomica is shown in Fig. 3,
with the geological age of particular records. Figure 4
shows localities that have yielded the material used in
the descriptive part. The genus is extremely rare out-
side Russia, in spite of the fact that the Mesozoic
fa una of Euro pe i s bet ter inves tigat ed. In the pa leo geo -
graphical aspect, the genus Boreomica is confined to

1390
PALEONTOLOGICAL JOURNAL Vol. 51 No. 13 2017
GUZHOV
the Boreal–Atlantic Region (Zakharov et al., 2003).
In the Jurassic of the Russian Plate, the latitudinal dis-
tribution of specimens varies widely depending on age.
In particular, the Lower Bathonian material comes
from the Saratov Region. The boundary of the zone of
mass distribution of Callovian species extends through
the Yaroslavl Region (the southernmost locality rich
in Boreomica is known near Rybinsk), while less abun-
dant localities are known southerly (in Ryazan,
Nizhny Novgorod, Bryansk, and northern Kursk
regions). The boundary of mass distribution of Boreo-
mica in the Late Kimmeridgian passed through the
southern Nizhny Novgorod Region; in the Middle
Volgian, it was in the Ulyanovsk Region. In general,
the frequency of finds increases northerly. On the
other hand, it is surprising that the genus is rare in the
Arctic Biogeographical Realm. To date, they have not
been recorded in northern Eastern Siberia (Beisel,
1983). This is probably caused by the fact that paleon-
tological works devoted to boreal gastropods are
extremely scarce (for example, two or three Jurassic
species are known in the Canadian sector of the Arctic
Region) and it is highly probable that certain taxa
escaped detection. This is evidences by the data pro-
vided by Kaim et al. (2004) on several new localities of
Boreomica. A search for Boreomica at different strati-
graphical levels of the Arctic Region seems promising.
MORPHOLOGICAL DIVERSITY
OF BOREOMICA SPECIES
In early works, Gründel (1975, 1999) marked the
disappearance of ridges toward the end of the shell
growth in “Hudlestoniella caleptra” and, in the shells
shown in the figures, the last whorl is smooth. How-
ever, subsequently, he figured two Bathonian shells of
“H. caleptra,” which are ornamented up to the tip
(Gründel et al, 2010, pl. 4, fig. 1; pl. 5, fig. 1). Thus,
ornamentation of the species apparently varied widely
in ontogeny. Some assemblages were probably domi-
nated by shells with smoothed ridges, whereas others
lacked smoothing. Boreomica exigua arenosa investi-
gated by us is mostly represented by completely orna-
mented shells, although they include specimens with
weaken or smoothed ridges. Depending on the assem-
blage, the last vary in abundance from rare to rather
widespread. It is plausible that, in B. caleptra, a similar
situation is possible; however, this is not the case;
shells with smoothed ridges prevail. B. caleptra is rep-
resented by rare specimens from a limited stratigraph-
ical interval. It is impossible to show morphological
difference between the samples of Upper Bajocian–
Lower Bathonian and Late Bathonian shells of the
species (in view of their facies confinement).
Representatives of Boreomica from the Russian
Plate can be regarded as a genetically connected
group, since they likely belong to the same lineage.
The conchological group of B. exigua looks stable
throughout the time interval from the Bathonian to
Volgian. The shell morphology did not change consid-
erably. However, intraspecific polymorphism is signif-
icant (see descriptions of the species B. exigua and
B. undulata). All the above strongly complicates work
with the group. The ecomorph from argillaceous
deposits (type A) is characterized by a small size and
relatively short shell (because of shortening the teleo-
conch), more stable parameters of ornamentation.
The ecomorph from coarse-grained deposits (sand)
(type B) is distinguished by the twice larger size and
longer teleoconch and also the more diverse ornamen-
tation and its norm in different populations. At the
same time, the morph B has wider isochronous whorls
of the shell (Fig. 2) than morph A. Thus, the greater
size was reached not only by the greater shell length,
but also by the larger size of individuals of the same
ontogenetic age. Members of the group of different
geological age are investigated to different extent with
reference to the spectrum of their ecomorphs. B. exi-
gua is well represented by the ecomorphs A and B. In
B. undulata, the type A is frequent and the type B is
very rare. For example, ecomorphs of the species
B. exigua and B. undulata of the type A clearly differ
from each other in the features of collabral ornamen-
tation, while differentiation between the species as a
whole is complicated. A certain role is played by
extreme scarcity of the data on the ecomorph of the
species B. undulata of the type B. In addition, there
were populations intermediate between the types A
and B. Their members are represented by rare speci-
mens of B. exigua. For example, they combine more
stable ornamentation of the ecomorph type A with
shells intermediate in height and diameter between the
morphs A and B. Bathonian Boreomica sp. is probably
also represented by the morph intermediate between
the types A and B. The material of Albian B. recta
should be assigned to the morph of the type A.
Intraspecific polymorphism and evolutionary sta-
bility of morphological characters of the shell strongly
complicate, on the one hand, differentiation and sub-
stantiation of independence of species and, on the
other hand, prevent the use of phylogenetically
important characters for differentiation between spe-
cies. The only trend which is evident is observed in
ecomorphs of the type A of the group B. exigua mani-
fested in an increase in the sharpness of ridges; from
B. exigua exigua (having the smoothest outline)
through Late Oxfordian Boreomica sp. and Late Kim-
meridgian B. undulata (distinctly sharper ornamenta-
tion) to Middle Volgian B. undulata (with the narrow-
est and sharpest ridges in the relief). The judgment of
the taxonomic significance of particular characters is
also not always unequivocal. It differs in ecomorphs of
different types. For example, for ecomorphs of the
type A, which show a much greater morphological sta-
bility, the character and density of collabral ornamenta-
tion has a greater taxonomic significance than for eco-
morphs of the type B, in which it varies considerably in
both the range and norm prevailing in population.

PALEONTOLOGICAL JOURNAL Vol. 51 No. 13 2017
ON NEW JURASSIC RISSOOIDEA AND ZYGOPLEUROIDEA 1391
In B. exigua, B. undulata, and B. recta, it appeared
possible to study certain features of protoconch mor-
phology. Larvae of all of the three species had a plank-
tonic stage, as follows from the division of the proto-
conch into embryonic and larval stages (Pl. 2, fig. 6c,
Pl. 3, figs. 1, 4b) and distinct morphological boundary
between the protoconch and teleoconch. The embry-
onic shell was initially covered with chaotic cellular
microornamentation, which was subsequently replaced
by microornamentation composed of chaotically
arranged tubercles. In B. exigua, protoconchs show
somewhat worse preservation, their ornamentation is
mostly preserved in the sites near the whorl sutures
and represented by tubercles. In B. undulata, some
shells also have protoconchs, which are covered over
varying extent by ornamentation of strokes radially
converging in the direction of the shell growth. The
sites of protoconchs with this ornamentation can be
absent completely. Judging from the data obtained
with the aid of an electron microscope, the zone of the
development of radial strokes is usually interrupted
during mechanical damage of the growing margin of
larval shells, which is followed by ornamentation com-
posed of chaotic tubercles (Pl. 2, fig. 6c, Pl. 3, fig. 3b).
The ornamentation of B. recta is poorly investigated.
According to Destombes (1983), the protoconch of
this species has a series of transverse strokes (25–
35 per whorl), which diverge from the upper margin of
whorls, other ornamentation has not been recorded
(Destombes, 1983, p. 43, text-fig. 1, figs. 1, 2).
JURASSIC AND CRETACEOUS
ZYGOPLEUROIDEA CONVERGENTLY
SIMILAR TO BOREOMICA
In the Jur ass ic b eds o f th e Russia n Pl ate, Boreomica
frequently co-occurs with relatively small and simi-
larly ornamented shells belonging mostly to the family
Zygopleuridae. The data on these finds are scarce and
the majority of shells display fragmentary and fre-
quently poor preservation. Therefore, in some cases,
they were referred to the same genus as species that are
here assigned to the genus Boreomica. In the Jurassic
of Russia, similar zygopleurids have been described
from the Lower Bathonian as Katosira? sp. (Mitta
et al., 2004) and Hudlestonella caleptra (Gerasimov,
1992) from the Volgian Stage as Procerithium volgense
(Gerasimov, 1955, 1969, 1992) from the Jurassic and
Cretaceous of northern Russia as Eulima pusilla (Tull-
berg, 1881) and Hudlestoniella pusilla (Kaim et al.,
2004).
Eulima pusilla was described from boulders of the
same locality as Boreomica undulata. Tullberg (1881)
divided boulders that have yielded the fauna into three
types: “dark gray bituminous limestone,” which is
presently dated Upper Volgian Substage; “light sabu-
lous limestone” dated Valanginian, and “light gray
calcareous sandstone” dated Upper Oxfordian.
E. pusilla is the only species which according to the
description comes from “gray sandstone.” However,
in the table of that paper, this species is placed in the
same column as species collected from “light gray cal-
ciferous sandstone.” Tullberg determined ammonites
from “calcareous sandstone” as Ammonites alternans
Buch. Frebold (1930) believed that they are Lower
Oxfordian, and determined as Cardioceras excavatum
var. arctica (Pavlow, 1914). The deposits enclosing
ammonites he characterized similar to Tullberg. In a
recent paper, Hryniewicz et al. (2015) reexamine the
rocks collected by their expedition in the Skodde Bay
(=Bakan Bay), describe the fauna from “dark gray
calcareous sandstone,” and provide a figure of an
ammonite. M.A. Rogov (personal communication)
believes that smaller specimens of Cardioceras excava-
tum var. arctica figured by Frebold (1930, pl. 24) and the
ammonite from Hryniewicz et al. (2015, text-fig. 8A)
are characteristic of the Upper Oxfordian, likely of its
upper part. The large ammonite (Frebold, 1930, pl. 25)
is relatively poorly preserved, complicating identifica-
tion; perhaps, this is possibly Upper Oxfordian Priono-
doceras. A similar point of view on ammonites from
work of Frebold was provided by Bodylevsky (1967).
However, the situation with “Upper Oxfordian”
E. pusilla is ambiguous. In the characteristics of the
Upper Oxfordian fauna in the paper of Hryniewicz,
E. pusilla is not mentioned at all, whereas Tullberg
marked that it is frequent in “gray sandstones.” What
is the reason for the absence of mentioning?
E. pusilla is also recorded by Tullberg in “sabulous
limestone.” Based on Buchia and ammonites, these
boulders are referred to the Lower Valanginian. From
boulders, Tullberg described Aucella keyserlingiana
var. majuscule, which Zakharov (1981) synonymized
under Buchia keyserlingi, an index species of the
Buchia Zone of the same name, and correlated it with
the upper part of the Lower Valanginian. Bodylevsky
(1967) provided the list of the following ammonites:
Temnoptychites hoplitoides (Nikitin), T. n ovosem e l i c u s
(Sokolov), T. aff. novosemelicus (Sokolov), T. e legans
Bodylevsky, T. b orea l i s Bodylevsky, T. triptychiformis
(Nikitin), Russanovia diptycha (Keyserling), etc., dat-
ing them as the Temnoptychites hoplitoides Zone of the
Middle Valanginian (the Berriasian was then regarded
as the Lower Valanginian). In the scheme of the boreal
Lower Cretaceous proposed by Bogomolov (1989), the
interval rich in Tem n optychites falls in the Tollia kli-
movskiensis Zone of the Lower Valanginian, which is also
reflected in the boreal standard of Baraboshkin (200 4).
Let us turn to the specimen from the collection of
Nordenskiöld f igured by Kaim et al. (2004, text-fig. 12B)
as the “holotype” of E. pusilla. The type specimen cho-
sen by later researchers should be named the lectotype
of the species, the type series of which contains more
than one specimen (see International Code …, 1999,
article 73F). In addition, it is recorded in a wide range of
stratigraphic levels and, hence, almost for sure, rep-
resents a mixture of two different taxa. However, there is
no comment. It can only be guessed that the lectotype is
the specimen figured by Tullberg in pl. 2, fig. 24. Unfor-
tunately, Tullberg has not reported the type of boulders

1392
PALEONTOLOGICAL JOURNAL Vol. 51 No. 13 2017
GUZHOV
that yielded shells of E. pusilla. The lectotype is dated
“Upper Jurassic.” This repeatedly raises the question of
whether or not “gray sandstone” is the fourth type of
boulders distinguished from others in stratigraphy. And
why only three basic types of boulders are considered in
the paper by Hryniewicz devoted to lithologic and geo-
chemical analysis of boulders, while the type of “gray
sandstones” is not considered.
Let us turn to the material referred by Kaim to
E. pusilla. The lectotype is a teleoconch fragment,
which is initially covered with collabral ridges, whereas
the last two whorls already lack ridges. A photograph
at a high magnification shows spiral undulation on the
whorls with ridges. Other specimens come from a
borehole core from the territory of the subpolar Urals
(Valanginian) on the Levaya Boyarka River in the
Taimyr Peninsula (Volgian Stage) (Kaim et al., 2004,
text-figs. 12A, 12C). It is possible to conclude that the
protoconch (last whorl) is covered with microscopic
tubercles; the boundary with the teleoconch is marked
by the appearance of ridges. The first one or two
whorls of the teleoconch are covered with greater or
lesser developed ridges; succeeding whorls are
smooth. Ornamented whorls of the teleoconch are
also covered with spiral undulae or thin threads.
From the Lower Bathonian of the Belgorod Region
(a borehole near the town of Shebekino), Gerasimov
(1992, p. 62) described the species Hudlestonella
caleptra. In the description, it is reported that the shells
are up to 10–12 mm high and consist of 8–8.5 whorls.
The whorl surfaces have 8 or 9 rough ridges and one to
three low spiral threads. In addition, a heterostrophic
protoconch is marked. One specimen was figured (Ger-
asimov, 1992, pl. 18, fig. 39). Unfortunately, these spec-
imens were lost, but I have found a negative of the orig-
inal (Fig. 1h). This is a teleoconch of five whorls, which
are covered at the beginning by wide, but poorly devel-
oped ridges; the last whorl already lacks ridges. All
whorls are covered with densely spaced spiral undulae,
which are also seen on the base. A negative of one more
specimen from the same locality that has not been pub-
lished corresponds to the original. This is a fragment
formed of three whorls, the last of which lacks ridges
and has a similar spiral undulation (Fig. 1g). The
description provided by Gerasimov was probably based
on a mixture of different species, whereas these speci-
mens resemble Laevipleura, differing from the type spe-
cies in the character of ridges, which have a rounded
bend between the lateral side and base on smooth
whorls, and in the better developed spiral ornamenta-
tion. It is similar in morphology to shells of Hudleston-
iella pusilla (Kaim et al., 2004).
Gerasimov’s material shows certain similarity to
the shells described by Gründel from the Lower
Bathonian of Saratov as Katosira? sp. (Mitta et al.,
2004, p. 26, pl. 9, figs. 3, 5). Shells of Katosira? sp. are
poorly preserved; they are fragmentary and strongly
eroded on the surface, but retain some traces of col-
labral ornamentation (on late whorls, they look like
rough growth lines) and spiral ornamentation, which
is stronger on the base. The largest fragment reaches
14 mm in height. The presence of spiral ornamenta-
tion and its character make this form most similar to
Katosira Koken, 1892 (family Procerithiidae).
Gerasimov’s Hudlestonella caleptra and Eulima
pusilla are similar in a number of characters: more or
less early disappearance of collabral ornamentation,
development of thin spiral ornamentation, and pres-
ence of rounded basal–palatal bend. In addition, in
both forms, a stronger spiral ornamentation on the
base (as in Katosira? sp. from the Lower Bathonian of
Saratov) has not been recorded (and this is not seen in
photographs). The two forms probably belong to an
undescribed group of zygopleurids.
The situation with Volgian Procerithium volgense is
considerably more complex. This species was origi-
nally described from the Virgatites virgatus Zone of the
Middle Volgian Substage of the Yaroslavl Region
(Gerasimov, 1955). Later, it was also recorded in the
Craspedites nodiger and Kachpurites fulgens zones of
Moscow and Moscow Region (Gerasimov, 1969,
1992). However, the taxonomic position of species
remains uncertain, since it is covered only with rich
collabral ornamentation, whereas Procerithium is
characterized by reticulate ornamentation, in which
collabral elements are only stronger than spiral ones.
In 1992, Gerasimov included this species in a new sub-
genus of Plicacerithium (Gerasimov, 1992). Later, the
species was referred without comment to the genus
Glosia (Guzhov, 2002), while Plicacerithium was
ranked genus included in the family Epitoniidae.
Examination of available material of Procerithium
volgense from Gerasimov’s collection has shown that it
actually can combine several species and genera, the
taxonomic position of which is open to question
because of poor preservation.
When establishing the species, Gerasimov did not
designate the holotype. The type material is four
imprints from sandstone of the Virgatites virgatus Zone
at the village of Gorodok. Two specimens were shown
in figures; one without magnification and the second
is magnified (Gerasimov, 1955, pl. 40, figs. 13, 14). In
redescriptions of the species in 1969 and 1992, he
repeatedly did not designate the holotype. In the last
work, the description was accompanied by photo-
graphs of shells from other locality (Gerasimov, 1992,
pl. 24, figs. 14, 15) and also by a large, but poor photo-
graph of an imprint from the type locality (Gerasimov,
1992, pl. 15, fig. 15). The last specimen was refigured
from Gerasimov’s negative in fig. 1l.
The diagnoses of the species provided by Gerasi-
mov in different years contradict each other. In the
original description, he marked the presence of very
densely spaced thin spiral threads crossing collabral
ridges. In the diagnosis of 1969, the first three sen-
tences from the original description are repeated, but
the sentence concerning spiral threads is omitted.
They are also omitted in 1992. Perhaps, Gerasimov
actually observed a spiral pattern, but later mistaken it
for an artifact instead of a true character of the shell.

PALEONTOLOGICAL JOURNAL Vol. 51 No. 13 2017
ON NEW JURASSIC RISSOOIDEA AND ZYGOPLEUROIDEA 1393
We did not find in Gerasimov’s collection an
imprint from the type locality. In the description of the
species, Gerasimov indicated that the shell consists of
10–11 whorls and one of specimens is 7.8 mm high,
and the number of ridges is 10–13 per whorl (Gerasi-
mov, 1955, p. 189). However, the presence of many
whorls in the shell is not confirmed by figures: the
specimen from the paper published in 1955 shows five
whorls (Gerasimov, 1955, pl. 40, fig. 14), while in
1992, there are only four (Gerasimov, 1992, pl. 14,
fig. 15). The shell measurements are as follows: in
fig. 13, 6 mm; in fig. 14, 5.6 mm (Gerasimov, 1955; if
the figures correspond to the scale provided). The size
of lost shells considered in 1992 is impossible to estab-
lish, since in the publication, the original size of plates
was decreased (by an unknown coefficient) and mag-
nification in explanations to the plates are deprived of
original plates. The specimen shown in fig. 14 (Gera-
simov, 1955) is covered with thick ridges adjoining
each other, so that there is a narrow slit between them.
In my opinion, this cast only roughly reflects the mor-
phology of the imprint, since this is probably a tin
rather than plasticine cast. Therefore, it is impossible
to identify this original. I already dealt with a similar
cast in the study of Longaevicerithium bitzae (Gerasi-
mov, 1992). When producing metal casts, the mor-
phology of imprints are strongly distorted because
metal becomes hardened too early. An example is pro-
vided by the comparison of casts of L. bitzae (Gerasi-
mov, 1992, pl. 26. fig. 1b) with a silicone cast (Guzhov,
2004, pl. 11, fig. 5). Other figure (Gerasimov, 1992,
pl. 14, fig. 15) shows smooth transition from the lateral
side to the base and shell whorls are covered with
curved ridges, about ten per whorl.
Shells from the Kachpurites fulgens Zone (Figs. 1i–1k)
of Moscow are divided into two morphological types.
The first type (Fig. 1k) is represented by the original
from (Gerasimov, 1992, pl. 24, fig. 14). This is a rela-
tively large shell (fragment is 8.2 mm high) with opist-
hocyrt ridges, without a trace of a basal–palatal bend
or spiral undulation. The second type (Fig. 1i) is rep-
resented by the original shown in fig. 15 (3.7 mm
high). It is distinguished by the more densely spaced
opisthocyrt ridges and clearly different contour of the
last whorl, with a rounded basal–palatal bend and rel-
atively low base. The collection includes three more
fragmentary imprints from the same locality, probably
belonging to the second type. Reliable identification is
precluded by poor preservation. The taxonomic posi-
tion of the first type is uncertain (Zygopleura?). This
specimen is much larger than Boreoimica or Bralitzia.
Available fragment is about 8 mm high and, hence, the
complete shell was much higher. In addition, Volgian
Bralitzia found in the Virgatites virgatus Zone of the
same locality has a well-pronounced spiral ornamen-
tation. The ornamented imprint shown in Fig. 1j may
belong to the same form. The original of the second
type belongs to an unknown zygopleurid, which is
similar in whorl outline to Hudlestonella caleptra from
the Bathonian of Shebekino, but strongly differs from
it in the ornamentation.
The type material of Procerithium volgense was
apparently represented by imprints of shells of the
genus Boreomica (morph of the type B). If this is the
case, the Gerasimov’s species should be regarded as a
synonym of B. undulata (Tullberg, 1881). Other speci-
mens in the collection of Gerasimov identified as
P. vo l g e n s e belong to other species: Laevipleura sp.
(Craspedites nodiger Zone) and two or three species of
uncertain taxonomic position (Kachpurites fulgens
Zone), probably a mixture of two different zygopleu-
rids and Bralitzia.
Material “Procerithium volgense” from the Cras-
pedites nodiger Zone (Pl. 3, figs. 8–10) belongs to one
taxon. It is represented by shells with many whorls
covered with orthocline or opisthocyrt ridges and hav-
ing a rounded basal–palatal bend. Below they are
described as Laevipleura sp. The main difference of
this form from the type species L. blainvillei (Münster,
1841) is the absence of smoothed collabral ornamen-
tation throughout available whorls of the teleoconch.
REFERENCES
Arkell, W.J., The Jurassic System in Great Britain, Oxford:
Clarendon Press, 1970.
Baraboshkin, E.Yu., Lower Cretaceous ammonitic zonal
standard of the Boreal Belt, Byull. Mosk. Ob-va Ispyt. Prir.
Otd. Geol., 2004, vol. 79, no. 5, pp. 44–68.
Beisel, A.L., Late Jurassic and Early Cretaceous gastropods
of the north of Middle Siberia (taxonomic composition,
paleoecology, stratigraphical and paleogeographical signif-
icance), Tr. Inst. Geol. Geofiz., 1983, no. 484, pp. 1–94.
Bodylevsky, V.I., Jurassic and Cretaceous faunas of the
Novaya Zemlya Archipelago, Zap. Gorn. Inst., 1967 , vol. 53 ,
no. 2, pp. 99–122.
Bogomolov, Yu.I., Polypt ychites (ammonites) and biostra-
tigraphy of the boreal Valanginian, Tr. Inst. Geol. Geofiz.
Sib. Otd. Akad. Nauk SSSR, 1989, vol. 696, pp. 1–200.
Cossmann, M., Essais de paléoconchologie comparée: Livra-
sion 12, Paris: Chez l’Auteur, 1921.
Dayczak-Calikowska, K. and Moryc, W., Rozwój basenu
sedymentacyjnego i paleotektonika jury sródkowej na
obszarze Polski, Kwartalnik G eo l., 1988, vol. 32, no. 1,
pp. 117–136.
Destombes, P., Récherches sur la mesofaune de l’Albien
inférieur de Bully-Saint-Martin l’Hortier (Pays de Bray),
Bull. Trimmest. Soc. Géol. Normand Amis Mus. Havre, 1983,
vol. 70, no. 4, pp. 41–57.
Epikontinentalny perm i mezozoik w Polsce, Prace Państ-
wow. Inst. Geol., 1997, vol. 153, pp. 1–452.
Frebold, H., Verbreitung und Ausbildung des Mesozoikums
in Spitsbergen, Skr. Svalb. Ishav., 19 30, no. 31, pp. 1–127.
Gavrilov, Yu.O., Shchepetova, E.V., Rogov, M.A., and
Shcherbinina, E.A., Sedimentology, geochemistry, and
biota of the Volgian carbonaceous beds of the northern part
of Central Russian Sea (Kostroma Region), Litol. Polezn.
Iskop., 2008, no. 4, pp. 396–424.
GB3D Type Fossils: Hudlestoniella burtonensis Hudleston,
1892. <http://www.3d-fossils.ac.uk/fossilType.cfm?typSam-
pleId=20006601>.

1394
PALEONTOLOGICAL JOURNAL Vol. 51 No. 13 2017
GUZHOV
Gerasimov, P.A., Rukovodyashchie iskopaemye mezozoya
tsentral’nykh oblastei evropeiskoi chasti SSSR. Ch. I. Plastin-
chatozhabernye, bryukhonogie, lad’enogie mollyuski i pleche-
nogie yurskikh otlozhenii (Index Fossils from the Mesozoic
of the Central Regions of the European Part of the USSR:
Part I. Lamellibranchiates, Gastropods, Scaphopods, and
Brachiopods from the Jurassic Beds), Moscow: Gos-
geoltekhizdat, 1955.
Gerasimov, P.A., Gastropody yurskikh i pogranichnykh nizh-
nemelovykh otlozhenii Evropeiskoi Rossii (Gastropods from
the Jurassic and Boundary Lower Cretaceous Beds of Euro-
pean Russia), Moscow: Nauka, 1992.
Gerasimov, P.A., Mitta, V.V., and Kochanova, M.D., Isko-
paemye volzhskogo yarusa Tsentral’noi Rossii (Fossils from
the Volgian Stage of Central Russia), Moscow: 1995.
Gerasimov, P.A., Mitta, V.V., Kochanova, M.D., and Tesa-
kova, E.M., Iskopaemye kelloveiskogo yarusa Tsentral’noi
Rossii (Fossils from the Callovian Stage of Central Russia),
Moscow: 1996.
Gründel, J., Gastropoden aus dem Dogger: III. Rissoini-
dae, Eucyclidae und Trochidae, Z. Geol. Wissensch., 1975,
vol. 3, no. 2, pp. 239–251.
Gründel, J., Truncatelloidea (Littorinimorpha, Gastrop-
oda) aus dem Lias und Dogger Norddeutschlands und Nor-
dpolens, Berl. Geowiss. Abh. R. E, 1999, vol. 30, pp. 89–119.
Gründel, J., Gastropoden des Pliensbachiums (unterer
Jura) aus der Usedom-Senke (Norddeutschland), Zitteli-
ana, 2007, vol. 30, pp. 89–119.
Gründel, J., Koppka, J., and Schneider, S., Neue Gas-
tropoden aus Dogger-Geschieben Nordostdeutschlans Süd-
frankreich, Arch. Geschiebek., 2010, vol. 6, no. 1, pp. 1–50.
Gründel, J. and Mitta, V., Gastropoden aus dem Unter-
callovium des Unzha-Beckens (Zentralrussland), Freib.
Forschung. R. C., 2013, no. 545, pp. 107–139.
Gründel, J. and Nützel, A., Gastropoden aus dem oberen
Pliensbachium (Lias δ2, Zone des Pleuroceras spinatum)
von Kalchreuth östlich Erlangen (Mittelfranken), Mitt.
Bayerisch. Staatssamml. Palaontol. Hist. Geol., 1998, no. 38,
pp. 63–96.
Guzhov, A.V., On the revision of Jurassic gastropods of
Central Russia: 1. Genus Plicacerithium, Paleontol. Zh.,
2002, no. 4, pp. 17–20.
Guzhov, A.V., Jurassic gastropods of European Russia
(orders Cerithiiformes, Bucciniformes, and Epitonii-
formes), Paleontol. J., 2004, vol. 38, suppl. no. 5, pp. 457–
562.
Guzhov, A.V., Gastropod assemblages from the Middle and
Lower Callovian of central European Russia, Pal eontol. Zh.,
2006, no. 5, pp. 33–38.
Guzhov, A.V., Mesozoic rissoid gastropods: History of the
study, systematics, and diversity, Paleontol. J., 2017, vol. 51,
no. 7, pp. 92–111.
Hryniewicz, K., Hagstrom, J., Hammer, O., Kaim, A., Lit-
tle, C.N., and Nakrem, H.A., Late Jurassic–Early Creta-
ceous hydrocarbon seep boulders from Novaya Zemlya and
their faunas, Palaeogeogr., Palaeoclimatol., Palaeoecol.,
2015, vol. 436, pp. 231–244.
Hudleston, W.H., A monograph of the Inferior Oolite Gas-
tropoda, Palaeontogr. Soc. Monogr., 1887, vol. 40, pp. 1–56.
Hudleston, W.H., A monograph of the Inferior Oolite Gas-
tropoda, Palaeontogr. Soc. Monogr., 1892, vol. 45, pp. 225–
272.
Kaim, A., Beisel, A.L., and Kurushin, N.I., Mesozoic gas-
tropods from Siberia and Timan (Russia): Part 1. Vetigas-
tropoda and Caenogastropoda (exclusive of Neogastrop-
oda), Pol. Polar Res., 2004, vol. 25, nos. 3–4, pp. 241–266.
Mesezhnikov, M.S., Kimeridzhskii i volzhskii yarusa severa
SSSR (Kimmeridgian and Volgian Stages of the Northern
USSR), Leningrad: Nedra, 1984.
Mitta, V., Kostyleva, V., Dzyuba, O., Glinckikh, L., Shury-
gin, B., Seltzer, B., Ivanov, A., and Urman, O., Biostratig-
raphy and sedimentary settings of the Upper Bajocian–
Lower Bathonian in the vicinity of Saratov (central Russia),
Neues Jahrb. Geol. Paläontologie. Abh., 2014, vol. 271, no. 1,
pp. 95–121.
Nützel, A., Über die Stammesgeschichte der Ptenoglossa
(Gastropoda), Berl. Geowissensch. Abh. R. E, 1998, vol. 26,
pp. 1–229.
Nützel, A. and Gründel, J., Early Jurassic (Pliensbachian) gas-
tropods from Franconia, southern Germany, Palaeontogr.
Abt. A, 2015, vol. 305, nos. 1–3, pp. 1–87.
Nützel, A. and Kließling, W., Gastropoden aus dem Amal-
theenton (oberes Pliensbachium) von Kalchreuth, Geol.
Blätter Nordost Bayern, 1997, vol. 47, nos. 1–4, pp. 381–
414.
Ob’’ekty geologicheskogo naslediya Yaroslavskoi oblasti:
stratigrafiya, paleontologiya i paleogeografiya (Objects of
Geological Heritage of the Yaroslavl Region: Stratigraphy,
Paleontology, and Paleogeography), Moscow: Yustitsin-
form, 2012.
Rogov, M.A., Ammonites and infrazonal division of the
Dorsoplanites panderi Zone (Volgian Stage, Upper Jurassic)
of European Russia, Dokl. Akad Nauk, 2013, vol. 451, no. 4,
pp. 435–440.
Rogov, M.A. and Zakharov, V.A., Ammonite- and bivalve-
based biostratigraphy and Panboreal correlation of the Vol-
gian Stage, Sci. Chin. Ser. D: Earth Sci., 2009, vol. 52,
no. 12, pp. 1890–1909.
Schröder, M., Frühontogenetische Schalen jurassischer
und unterkretazischer Gastropoden aus Norddeutschland
und Polen, Palaeontogr. Abt. A, 1995, vol. 238, nos. 1–4,
pp. 1–95.
The Geology of Central Europe, vol. 2. Mesozoic and Caenozoic,
London: Geol. Soc. London, 2008, pp. 749–1499.
Tullberg, S.A., Ueber Versteinerungen aus den Aucellen-
schichten Novaja-Semljas, Bih. Kongl. Sven. Vetens.-Acad.
Handl., 1881, vol. 6, no. 1, pp. 1–25.
Upper Bajocian and Lower Bathonian in the vicinity of
Saratov, Nov. Geol. Muz. Vernad., 2004, no. 12, pp. 1–39.
Wenz, W., Handbuch der Paläozoologie, vol. 6. Gastropoda I.
Allgemeiner teil und Prosobranchia, Berlin–Zehlendorf:
Gebürger Borntraeger, 1940, no. 4, pp. 721–960.
Yamnichenko, I.M., Melkoroslye gastropody yurskikh
otlozhenii Donbassa i Dneprovsko-Donetskoi vpadiny (Small-
sized Gastropods from the Jurassic of the Donets Coal
Field and Dnieper–Donets Depression), Kiev: Nauk.
Dumka, 1987.
Zakharov, V.A. Buchiidae and biostratigraphy of the boreal
Upper Jurassic and Neocomian, Tr. Inst. Geol. Geofiz. Sib.
Otd. Akad. Nauk SSSR, 1981, no. 458, pp. 1–272.
Zakharov, V.A., Meledina, S.V., and Shurygin, B.N., Pale-
obiochores of the boreal Jurassic basins, Geol. Geofiz., 2003,
vol. 44, no. 7, pp. 664–675.
Translated by G. Rautian