The plant fossils from the Kaizara Formation (Callovian, Jurassic) of the Tetori Group in the Izumi district, Fukui Prefecture, Central Japan

Abstract

The Middle Jurassic (Bathonian to Callovian) Kaizara flora is proposed herein for the plant fossil assemblage in the Kaizara Formation, Kuzuryu Subgroup, Tetori Group. In addition to Otozamites crassipinnatus sp. nov., twelve species are reported, including species of Equisetales, uncertain order of pteridosperms, Cycadeoideales, Cycadales, and Coniferales. Some species have very thick lamina, implying that the climate might include dry periods. All species found in the Kaizara flora are new to the Tetori Group. Therefore, the Tetori-type flora is restricted to post-Callovian stages in the Tetori Group.

Full text

*KURAに登録されているコンテンツの著作権は，執筆者，出版社（学協会）などが有します。
*KURAに登録されているコンテンツの利用については，著作権法に規定されている私的使用や引用などの範囲内で行ってください。
*著作権法に規定されている私的使用や引用などの範囲を超える利用を行う場合には，著作権者の許諾を得てください。ただし，著作権者
から著作権等管理事業者（学術著作権協会，日本著作出版権管理システムなど）に権利委託されているコンテンツの利用手続については
，各著作権等管理事業者に確認してください。
Title The plant fossils from the Kaizara Formation (Callovian, Jurassic) of the
Tetori Group in the Izumi district, Fukui prefecture, Central Japan
Author(s) Yamada, Toshihiro; Uemura, Kazuhiko
Citation Paleontological Research, 12(1): 1-17
Issue Date 2008-04-30
Type Journal Article
Text version publisher
URL http://hdl.handle.net/2297/14544
Right Copyright © 2009 BioOne All rights reserved
http://dspace.lib.kanazawa-u.ac.jp/dspace/

Middle Jurassic Kaizara ora 1
Paleontological Research, vol. 12, no. 1, pp. 1–17, April 30, 2008
© by the Palaeontological Society of Japan
Introduction
The Tetori Group is a series of Middle Jurassic to
Lower Cretaceous formations which is widely dis-
tributed over the Hida Belt in northern Central Japan
(Figure 1A). The group consists of marine and non
marine deposits and is subdivided into three subgroups
which are dated roughly as follows; the Kuzuryu
Subgroup is Bathonian to Kimmeridgian, the Itoshiro
Subgroup is Tithonian to Barremian, and the Akaiwa
Subgroup is postBarremian, based on the ages of the
marine invertebrates in some of the constituent forma-
tions (Maeda, 1961a; Sato and Westermann, 1991;
Fujita, 2003; Sato et al., 2003; Sato and Yamada, 2005;
Matsukawa et al., 2006; Goto, 2007).
Since Geyler (1877) rst reported plant fossils from
it, many paleobotanical studies have been conducted in
the Tetori Group (e.g., Yokoyama, 1889; Oishi, 1940;
Kimura, 1958; Kimura et al., 1978). Four oras are
reported in the Tetori Group, namely, the Bathonian
to Callovian Kuzuryu ora in the Kuzuryu Subgroup
(Kimura, 1958), Tithonian to Barremian Oguchi ora
in the Kuwajima Formation of the Itoshiro Subgroup
(Kimura et al., 1978; Yabe et al., 2003), Barremian
Akaiwa ora in the Akaiwa Formation of the Akaiwa
Subgroup (Kimura and Sekido, 1976b; Yabe et al.,
2003), and Barremian Tamodani ora in the Chinabora-
dani Formation of the Akaiwa Subgroup (Kimura, 1975;
Yabe et al., 2003). These oras are similar to each other
in species composition, including various pteridophytes
and ginkgophytes, and are further classied as Tetori
type (or Siberian) oras, which ourished under a humid
warmtemperate climate (Kimura, 1987; Vakhrameev,
1991).
Among them, the Kuzuryu ora, that is, the oldest
one, has been used as a basis for inferring the paleo
phytogeography and paleoclimates during Middle Juras-
sic time in Japan (Kimura, 1987; Vakhrameev, 1991).
However, almost all horizons bearing the Kuzuryu ora
have been reassigned to postCallovian formations in
recent studies (Figure 2; for details, see the next sec-
tion). Besides the Kuzuryu ora, only one other pur-
portedly Middle Jurassic ora was known from Japan,
namely, the Utano ora in the Utano Formation of the
Toyora Group in Yamaguchi Prefecture in western
Honshu (Takahasi et al., 1965; Kimura et al., 1986;
Kimura and Ohana, 1987a). Recent reexamination of the
stratigraphy of the plantbearing deposits (Yamada and
Ohno, 2005) has shown that the Utano Flora actually
occurs from the Upper Jurassic to lowermost Cretaceous
The plant fossils from the Kaizara Formation (Callovian,
Jurassic) of the Tetori Group in the Izumi district,
Fukui Prefecture, Central Japan
TOSHIHIRO YAMADA1 AND KAZUHIKO UEMURA2
1Division of Life Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa 920-1192, Japan
(e-mail: ptilo@mb.infoweb.ne.jp)
2Department of Geology and Paleontology, National Museum of Nature and Science, 3-23-1 Hyakunincho, Shinjuku-ku, Tokyo 169-0073, Japan
Received December 5, 2006; Revised manuscript accepted October 10, 2007
Abstract. The Middle Jurassic (Bathonian to Callovian) Kaizara ora is proposed herein for the plant
fossil assemblage in the Kaizara Formation, Kuzuryu Subgroup, Tetori Group. In addition to Otozamites
crassipinnatus sp. nov., twelve species are reported, including species of Equisetales, uncertain order of
pteridosperms, Cycadeoideales, Cycadales, and Coniferales. Some species have very thick lamina, imply-
ing that the climate might include dry periods. All species found in the Kaizara ora are new to the Tetori
Group. Therefore, the Tetori-type ora is restricted to post-Callovian stages in the Tetori Group.
Key words: Kaizara ora, Kaizara Formation, Kuzuryu Subgroup, Tetori Group, Middle Jurassic, Tetori-
type ora

Toshihiro Yamada and Kazuhiko Uemura2
(Berriasian) Kiyosue Formation of the Toyonishi Group.
Therefore, as far as previous reports are concerned, no
true Middle Jurassic ora is known in Japan.
Here, we will report some plant fossils from the
BathonianCallovian Kaizara Formation of the Kuzuryu
Subgroup, found in the Izumi district of Ohno City,
Fukui Prefecture (Figure 1B). This is the rst reliable
report of a Middle Jurassic ora from Japan. A new
name, Kaizara Flora, is given to this ora and its strati-
graphic signicance will be discussed. Paleophytogeo
graphy of Middle Jurassic Japan is also inferred.
Previous and current stratigraphy
in localities bearing the Kuzuryu ora
The Kuzuryu ora was rstly dened as the plant
fossil assemblages of the Kuzuryu Subgroup and type
localities were designated in the Hakogase, Mochiana,
Shimoyama, Ushimaru and Wakogo areas (Kimura,
1958; Figures 1A.1–4, 1B, 2). After the proposal of the
Kuzuryu ora, plant fossil assemblages of the Sakaidera
and Kowashimizu formations in the Asuwa region (Fig-
ures 1A.5, 2) were considered as coevals of the Kuzuryu
ora (Maeda, 1961a). The previous and current status of
the stratigraphy in these localities is discussed below.
Shimoyama area in Kuzuryu / Itoshiro region (Figure
1A.1)
The type section of the Kuzuryu and Itoshiro Sub-
groups is designated in the Kuzuryu / Itoshiro region.
The Kuzuryu Subgroup in the type region is composed
of the Shimoyama, Oidani, Tochimochiyama, Kaizara
and Yambarazaka formations in ascending order (Maeda,
1961a; Fujita, 2003; Figure 2). These consist of marine
deposits except for the lowermost Shimoyama Formation
(Maeda, 1961a; Fujita, 2003). The ages of the Kaizara
and Yambarazaka formations are well constrained by
ammonoids, namely, late Bathonian to Callovian for the
former and Oxfordian to early Kimmeridgian for the
latter (Sato and Westermann, 1991).
Recent studies basically follow this stratigraphy and
the dating of the formations (Fujita, 2002, 2003; Matsu-
kawa et al., 2006), although the Oidani Formation is in-
cluded in the Tochimochiyama Formation in Matsukawa
et al. (2006). Otozamites sewardii, a component of the
Kuzuryu ora, is reported from the Kaizara Formation
distributed in the Shimoyama area by Oishi (1940). This
is the only component of the Kuzuryu ora which has
actually been collected from these Middle Jurassic de-
posits (Figure 2).
Hakogase and Mochiana areas in East of Izumi re-
gion (Figure 1A.2)
The Mochiana, Ochiai and Shimohambara Formations
comprised the Kuzuryu Subgroup in this region (Maeda,
1956, 1961a). The Shimohambara Formation was cor-
related to the Yambarazaka Formation using Inoceramus
sp. and Perisphinctes sp. (Maeda, 1961a). The plant
bearing horizons of the Hakogase and Mochiana areas
were placed in the Ochiai Formation which underlies the
Shimohambara Formation, thus a preOxfordian age for
the plant fossils was suggested (Figure 2).
Figure 1. A. Distribution of the Tetori Group (after Maeda, 1961b) indicated by shading. Numbers indicate localities of “Middle”
Jurassic plant assemblages: 1. Shimoyama area, Ohno City, Fukui Pref., 2. Hakogase and Mochiana areas, Ohno City, 3. Wakogo area, Ohno
City, 4. Ushimaru area, Takayama City, Gifu, Pref., 5. Asuwa region, Fukui City, Fukui Pref. B. Magnication of boxed area in A. The type
localities of the Kaizara ora are indicated by the leaet marks.

Middle Jurassic Kaizara ora 3
Recently, in a comprehensive stratigraphic study that
encompassed the Kuzuryu/Itoshiro and East of Izumi re-
gions (Fujita, 2002; Matsukawa et al., 2006) has shown
that only the Itoshiro Subgroup is distributed in this re-
gion. Fujita (2002) reassigned the plantbearing horizons
to the Ashidani Formation and redened the overlying
marine Shimohambara Formation as the Kamihambara
Formation. A Tithonian age for the Ashidani Formation
is deduced (Figure 2) because the underlain Yambara
Formation is postKimmeridgian in age (Sato and
Westermann, 1991; Fujita, 2003), while the occurrence
of Parapallasiceras sp. cf. pseudocontiguum (Donze
and Enay) suggests a late Tithonian age for the overly-
ing Kamihambara Formation (Sato and Yamada, 2005).
Matsukawa et al. (2006) assigned the plantbearing
horizons and overlying marine sediments to the Itsuki
Formation, but this assignment is not concomitant with
the report of an ammonoid of the family Crioceratitidae
from the Itsuki Formation, which rather indicates a late
Hauterivian to Barremian age (Goto, 2007).
Wakogo area in Mana region (Figure 1A.3)
The Kuzuryu Subgroup in the region consisted of the
Shimoyama, Shimowakago, Dosaiyama and Kaizara
Formations in ascending order (Maeda, 1960; Figure
2). Ammonoidbearing deposits were assigned to the
Kaizara Formation, which is a stratigraphic unit origi-
nally dened in the Kuzuryu/Itoshiro region. Plant
bearing horizons were arranged into the Shimowakago
Formation, which was considered to underlie the
Kaizara Formation (Maeda, 1960, 1961a; Figure 2).
In the previous stratigraphy, the ammonoidbearing
deposits were assigned to the Kaizara Formation on
the assumption that the deposits were isochronal to the
Kaizara Formation (Maeda, 1960), although none of the
ammonoids have been identied thus far by genera or
species. To the contrary, the existence of upper Titho-
nian marine deposits in the Mana region has been hinted
at recently by the occurrence of Parapallasiceras sp. cf.
pseudocontiguum (T. Sato, personal communication).
Therefore, reexamination of the ammonoids from the
marine sediments in the Mana region would be required
before reconstructing the stratigraphy in this region.
Figure 2. Previous and current interpretations on stratigraphic horizons bearing “Kuzuryu” ora (see text for references on these
interpretations). Previously accepted stratigraphic schemes are shaded. Corresponding formational boundaries between two interpretations
are correlated by dashed lines. Formations bearing “Kuzuryu” ora are indicated by leaet marks.

Toshihiro Yamada and Kazuhiko Uemura4
Yamada et al. (1989) pointed out that Maeda (1960)
interpreted the formational order in reverse, overlook-
ing the fact that the strata are inclined more than 90°
(inverted) in this region. Thus, it is obvious that the
plantcontaining horizons are younger than the marine
sediments, i.e., at least younger than the Callovian
(Yamada et al., 1989).
Ushimaru area in Shokawa region (Figure 1A.4)
The Kuzuryu Subgroup in the Shokawa region was
composed of the Ushimaru, Akahoke and Mitarai For-
mations in ascending order (Maeda, 1952, 1961a).
Among them, the Mitarai Formation is a marine unit
from which Lilloetia sp., indicating a Callovian age, was
obtained (Sato and Kanie, 1963). The Ushimaru Forma-
tion contains plant fossils and their age was considered
to be older than the Callovian (Maeda, 1961a; Figure 2).
Recently, a late Tithonian to Berriasian age for the
Mitarai Formation has been suggested based on the oc-
currence of Delphinella sp. cf. obtusenodosa (Retowski)
and the misidentication of Lilloetia sp., which was the
basis for the Callovian date, pointed out by Sato et al.
(2003). Accordingly, the Mitarai Formation is corre-
lated to the Kamihambara Formation and all the Tetori
Group formations in the Shokawa region are placed in
the Itoshiro Subgroup (Sato and Yamada, 2005; Figure
2). Furthermore, much younger ages (younger than late
Hauterivian) for the Ushimaru, Akahoke and Mitarai
formations are suggested by zircon UPb dating of tuff
beds (Kusuhashi et al., 2006).
Sakaidera and Kowashimizu Formations (Figure
1A.5)
Plantbearing horizons in the Asuwa region initially
were treated as the Itoshiro Subgroup (Kimura, 1958).
Later, Maeda (1961b) classied the Tetori Group sedi-
ments in the region into the Higashiamata, Sakaidera
and Kowashimizu formations in ascending order, of
which the Sakaidera and Kowashimizu Formations bear
abundant plant fossils (Oishi, 1940; Maeda, 1961b;
Figure 2). On the basis of unclassied ammonoids from
river oats, the uppermost Kowashimizu Formation
was compared to the Yambarazaka Formation (Maeda,
1961a, b). The Sakaidera Formation was correlated to
the Mitarai Formation of the Shokawa area based on
intercalated acidic tuffaceous beds (Maeda, 1961b).
The Sakaidera Formation was, in turn, correlated to the
Kaizara Formation because the Mitarai Formation was
compared to the Kaizara Formation at that time (Maeda,
1961a, b).
If the acidic tuffaceous beds in the Sakaidera and Mi-
tarai Formations are actually comparable, the Sakaidera
Formation is partly isochronal to the Mitarai Formation,
for which a late Tithonian to Berriasian age is inferred
(Sato et al., 2003). Another line of evidence, the chemi-
cal compositions of monazite and garnet particles in
sandstones, suggests that the three formations are in-
cluded in the Itoshiro Subgroup (Yamada et al., 2005;
Figure 2).
Summary of the updated stratigraphy and its impli-
cations on the Kuzuryu ora
The Kuzuryu ora was originally dened as the ora
of the Kuzuryu Subgroup, but all components of the
Kuzuryu ora were actually collected from the Itoshiro
Subgroup (Figure 2), except for Otozamites sewardii
which was reported from the Bathonian to Callovian
Kaizara Formation in the Shimoyama area by Oishi
(1940). Although the Kuzuryu ora thus includes at
least one species collected from the Kuzuryu Subgroup,
it is not even certain at this point whether the same ora
ourished continuously in the entire timespan of the
Kuzuryu Subgroup, ranging from the Bathonian to Kim-
meridgian (Sato and Westermann, 1991). Therefore, a
new oristic name for the plant fossil assemblage of the
Kaizara Formation is called for. Accordingly the name
Kaizara ora is given to this assemblage.
Materials and methods
Plant fossils were collected from the siltstone beds
in the Kaizara Formation (Kuzuryu Subgroup) at two
localities in Izumi district, Ohno City; Horadani (Hora
valley) at Kaizara area and Taniyamadani (Taniyama
valley) at Shimoyama area (Figure 1B). The geological
age of the Kaizara Formation is precisely determined
as latest Bathonian to early Callovian (Sato, 1962; Sato
and Westermann, 1991). All specimens are stored in the
National Museum of Nature and Science, Tokyo.
Taxonomy
Class Sphenopsida
Order Equisetales
Family Equisetaceae
Genus Equisetites Sternberg, 1833
Equisetites sp.
Specimen.―NSMPP9912 (Figure 3A)
Locality.―Horadani, Kaizara area.
Description.―A single fragment of stem was collect-
ed, consisting of two nodes and the internode between
them, which is compressed laterally. The internode is
2 cm long and 1.4 cm wide, and the surface is smooth.
The nodes are slightly swollen to 1.6 cm wide. Leaf
sheathes are 6 mm long and their lower twothirds is

Middle Jurassic Kaizara ora 5
Figure 3. A. Equisetites sp., NSMPP9912. B. Ctenozamites usnadzei Doludenko et Svanidze, NSMPP9903. Arrowheads show
remaining charred fragments of thick lamina. C. Line drawing of B. D. Anomozamites sp., NSMPP9917. E. Line drawing of D. F–J.
Otozamites crassipinnatus Yamada and Uemura, sp. nov. F. Holotype, NSMPP9914. G. Line drawing of F. H. Paratype, NSMPP9916. I.
Paratype, NSMPP9920. J. Paratype, NSMPP9915. Scale bars = 1 cm.

Toshihiro Yamada and Kazuhiko Uemura6
hardly distinguishable from the node. 9–10 leaf tooth
segments dissected from the sheath are visible in the
compressed specimen, thus it is probable that there are
more than 18–20 segments around the node. The seg-
ments are separated by depressed commissural anges
and the base of the segments is much broader than the
adjacent two anges (ca. 0.8 mm wide). The segments
are 5–10 mm long.
Comparison.―The specimen is assignable to genus
Equisetites because it has leaf sheathes and its stem is
smooth in the internode (Harris, 1961a). However, it
could not be classied down to species level because in-
formation on the nodal diaphragm and the exact number
of leaf tooth segments, which are inevitable for making
the specic assignment, are lacking.
Class Pteridospermopsida
Order uncertain
Family uncertain
Genus Ctenozamites Nathorst, 1886
Ctenozamites usnadzei Doludenko et Svanidze, 1969
Ctenozamites usnadzei Doludenko et Svanidze, 1969, p. 24, pl. 18,
gs. 1–6; pl. 19, gs. 3, 5, 6; Barnard and Miller, 1976, p. 37–41, pl. 1,
gs. 1–8; textgs. 1A–C; textgs. 2A–H.
Specimen.―NSMPP9903 (Figures 3B, C).
Locality. ―Taniyamadani, Shimoyama area.
Description.―Specimen consists of a partial pinna 8
cm long and 1.7 cm wide. Rachis of the pinna is about
2.5 mm and its upper surface is covered with the lamina.
The lamina margin is entire. Segments of the lamina are
rhomboidal, slightly revolute and as long as broad (ca.
10 mm). They arise at an angle of about 60° and imbri-
cate slightly. The segments have an obtuse apex, not
contracted acroscopic angle and decurrent basiscopic
angle. Veins are hardly seen in the parts where charred
fragments of the very thick lamina remain (arrowheads
in Figure 3B). About seven veins enter each segment.
They fork less than twice and run almost parallel before
ending in the margin of the segment. A concentration of
the veins of 12–15 per cm occurs in the middle part of a
segment.
Comparison.―This specimen is identied as C.
usnadzei, originally described from the Callovian of
Georgia, which has very thick lamina dissected into
rhomboidal segments with decurrent basiscopic base
(Doludenko and Svanidze, 1969). The number of veins
entering each segment in our specimen agrees with
the emended diagnosis of C. usnadzei by Barnard and
Miller (1976).
C. usnadzei is very similar to C. cycadea from the
Lower Jurassic of Germany (Schenk, 1887; Harris,
1964). According to Barnard and Miller (1976), C. us-
nadzei differs from C. cycadea in that the former has
hypodermis in the laminae. This means the lamina of
C. usnadzei is thicker than that of C. cycadea and this
feature makes the venation hardly visible in compressed
C. usnadzei specimens (Barnard and Millar, 1976).
Contrary to Barnard and Miller’s (1976) claim, inter-
specic variations in laminar and cuticular thicknesses
are reported in C. cycadea, which could be attributed
to conditions of insolation of the leaves (Barbacka and
van Koijnenburgvan Cittert, 1998). Barbacka and van
Koijnenburgvan Cittert (1998) also made note of the
possibility that a criterion based on laminar and cuticu-
lar thicknesses could form articially dened species.
However, the exact taxonomic relationships between
C. cycadea and C. usnadzei remain to be claried at
present. Therefore, we provisionally refer the specimen
under study to C. usnadzei based on its thick lamina and
hardly visible venation.
C. kachchhensis from the Middle to Upper Jurassic of
Kachchh, India (Bose and Banerji, 1984) differs from
the specimen because laminar segments of C. kachch-
hensis are broader than long. The specimen is similar to
C. serrani, originally described from the Upper Triassic
of Vietnam, in the shape of the laminar segments, but C.
serrani differs in having more crowded veins entering
the segments (Zeiller, 1903; Harris, 1961b).
Class Cycadeoidopsida
Order Cycadeoidales
Family uncertain
Genus Anomozamites Schimper, 1870
Anomozamites sp.
Specimen.―NSMPP9917 (Figures 3D, E).
Locality.―Taniyamadani, Shimoyama area.
Description.―Specimen consists of a leaf fragment 5
cm long and 3 cm wide. The leaf is lanceolate. Rachis is
3 mm wide. Lamina is divided suboppositely into rect-
angular segments 4–12 mm long and 5–7 mm wide. The
segments are entire, parallelsided and attach to the up-
per side of the rachis at almost right angles. Narrow slits
between the segments make segments imbricate. Veins
are parallel, simple, seldom forked and concentrated
with up to 40 veins/cm.
Comparison.―The specimen closely resembles A.
minor from the Upper Triassic of Scoresby Sound,
Greenland (Harris, 1926), A. sp. cf. minor from the
Upper Triassic of Anhui, China (Sze, 1933) and A. sp.
cf. minor from the Upper Triassic of Khorat, Thailand
(Konno and Asama, 1973), in the narrow slits between
the segments and crowded veins of the segments. How-
ever, the slits between the segments are slightly broader
in A. minor than in the specimen. Additional specimens

Middle Jurassic Kaizara ora 7
should be collected for further specic consideration.
Genus Otozamites Braun, 1843
Otozamites crassipinnatus T. Yamada and Uemura,
sp. nov.
Holotype.―NSMPP9914 (Figures 3F, G).
Paratype.―NSMPP9916 (Figure 3H), NSMPP
9920 (Figure 3I). NSMPP9915 (Figure 3J).
Type locality.―Horadani, Kaizara area (NSMPP
9914, 9920)
Other localities.―Taniyamadani, Shimoyama area
(NSMPP9915, 9916).
Etymology.―Compound of Latin adjective “crassus”
meaning thick and Latin adjective “pinnatus” meaning
pinnae.
Diagnosis.―Rachis completely covered by pinnae.
Pinnae alternate, thick, convex adaxially, arising at 60°.
Pinna margin reexed. Acroscopic angle of pinna over-
lapping diagonal basiscopic angle of pinna. Pinna apex
obtuse to round. Veins radiating from pinna attachment,
forked, at maximum concentration there are ca. 40 per
cm.
Description.―Specimens on hand are a fragment of
leaf 15.5 cm long and 3 cm wide (Figures 3F, G) and
detached pinnae (Figures 3H–J). The pinnatied leaf
is parallelsided. Petiole 2 mm in width is completely
covered by the pinnae. Pinnae with reexed margin 2–
9 cm long, 1.4–3.5 cm wide, thick, convex and round to
obovaterhomboid. Pinnae attach alternately to the upper
side of the petiole at 60° by the middle of their basal
margin. The basiscopic base of the pinnae is round or
not contracted and the acroscopic base is rounded. The
acroscopic base of the pinnae completely covers the
basiscopic base of the diagonal pinna. The apex of the
pinnae is obtuse to rounded. Veins are ne, radiating
from the point of the pinna attachment and forking sev-
eral times before ending at the margin. Their concentra-
tion is ca. 40 per cm at maximum.
Comparison.―Five species are reported so far which
have round to obovate pinnae with reexed margin simi-
lar to those of O. crassipinnatus, i.e., O. tenuatus, O.
tenellus, O. boolensis, O. marginatus and O. beani. Of
these O. crassipinnatus is most similar to O. tenuatus
from the Aalenian of Yorkshire, but the size of the pin-
nae and the number of veins are much smaller in O.
tenuatus (Leckenby, 1864; Harris, 1969). O. tenellus
from the Lower Jurassic of Hunan, China is different
in having a much narrower and smaller leaf with imbri-
cated pinnae (Zhou, 1983). O. boolensis, from the Juras-
sic of Australia and Antarctica, sometimes has round to
obovate pinnae, but it differs in the much smaller size
of the pinnae and more sparse veins (Douglas, 1963;
Cantrill and Hunter, 2005). O. marginatus, initially de-
scribed from the Bathonian of France, is distinguished
from O. crassipinnatus in its imbricated pinnae, which
is a diagnostic feature of that species (Saporta, 1875;
Harris, 1969). Adding to this, the pinnae of O. crassipin-
natus attach to the rachis at smaller angles than those of
O. marginatus. O. beani described from the Bajocian of
Yorkshire, UK is different in having more sparsely set
pinnae (Harris, 1969).
Otozamites sewardii Oishi, 1940
Otozamites sewardii Oishi, 1940, p. 334, pl. 31, g. 1.
Specimen.―NSMPP9901 (Figures 4C, D).
Locality.―Horadani, Kaizara area.
Description.―Specimen is a fragment of a leaf 10
cm long and wide. Petiole is 3 mm wide. Pinnae are
elongate, 6 cm long, 0.6–0.8 cm wide, and attach to the
upper side of the petiole by the slightly depressed mid-
point of the pinnae base. Angle between rachis and
pinnae is ca. 60°. Pinnae are contiguous at their base
because auricle is weakly developed. Apex of pinnae is
acuminate. About six veins arise at pinna base and each
of them forks several times and ends at the pinna mar-
gin. The maximum concentration of veins is about 50
per cm.
Comparison.―This specimen is identied as O.
sewardii, the only species described previously from
the Kaizara Formation, based on the feebly developed
auricle, seldom overlapping pinnae, and elongate pinnae
with acuminate apex (Oishi, 1940). O. sewardii is simi-
lar to O. pulcher from the Middle Jurassic of Elburz,
Iran in pinnae shape (Barnard and Miller, 1976), but O.
sewardii has more crowded veins in the pinnae than O.
pulcher.
Otozamites sp.
Specimen.―NSMPP9913 (Figures 4A, B).
Locality.―Horadani, Kaizara area.
Description.―Specimen is a small fragment of leaf 2.2
cm long and 1.5 cm wide. Petiole is about 0.5 mm wide.
Pinnae arise alternately at about 70° and the acroscopic
angle of the pinnae is contiguous to the basiscopic one
in the diagonal position. Pinnae are 0.8 cm long, 0.5
cm wide and ovate. The apex of the pinnae is obtuse to
rounded. The pinna base is depressed and the auricle is
weakly developed. Six to seven veins arising from the
base of the pinnae fork several times. Vein concentration
is 35 per cm. Usually one vein enters into the acroscopic
auricle.
Comparison.―O. mimetes is characterized by con-
tiguous pinnae arising at about 70°, feebly developed

Toshihiro Yamada and Kazuhiko Uemura8
Figure 4. A. Otozamites sp., NSMPP9913. B. Line drawing of A. C. O. sewardii Oishi, NSMPP9901. D. Line drawing of C. E.
Pterophyllum sp., NSMPP9919. F. Line drawing of E. G–I. Ptilophyllum caucasicum Doludenko et Svanidze. G. NSMPP9906. H. Line
drawing of G. I. NSMPP9909. Scale bars = 1 cm.

Middle Jurassic Kaizara ora 9
acroscopic auricle, veins with a concentration of 30 per
cm and roundobtuse to roundtruncate apex of pinnae
(Harris, 1949). These diagnostic features are concordant
with the specimen described, thus it could be compared
to O. mimetes. However, these external characters
are also shared with O. walkamotaensis from the Up-
per Jurassic of Kachchh, India (Bose and ZebaBano,
1981). These two species can be distinguished from
one another by their epidermal features; O. mimetes
shows irregular arrangement of stomata (Harris, 1949;
Barbacka et al., 2006), while O. walkamotaensis has dis-
tinct stomatiferous bands (Bose and ZebaBano, 1981).
Unfortunately, this epidermal feature is not preserved in
our specimen, and therefore we could not assign it to a
species.
O. kachchhensis from the Middle to Upper Jurassic of
Kachchh, India is closely similar to our leaf specimen in
attachment and shape of pinnae, but differs from it in the
smaller number of veins entering into the auricle (Bose
and Banerji, 1984). It is also similar to O. contiguus
from the Middle to Upper Jurassic of Kachchh, India,
but is distinguished from O. contiguus because the latter
has pinnae with acuminate apices (Feistmantel, 1876). O.
kilpperiana from the Middle Jurassic of Elburz, Iran is
similar to our specimen in pinnae shape, but in this spe-
cies veins entering pinnae are less crowded than in our
specimen (Barnard and Miller, 1976). O. margaritaceus
also has small pinnae with vein concentration of 30–
50 per cm (Zhou, 1983), but it is distinguished from our
specimen in asymmetrical pinnae shape.
Genus Pterophyllum Brongniart, 1828
Pterophyllum sp.
Specimen.―NSMPP9919 (Figures 4E, F).
Locality.―Horadani, Kaizara area.
Description.―A leaf fragment 4 cm long, 3.8 cm
wide, with pinnae of one side not preserved. Rachis is
2.5 mm wide and marked with three ribs on the side ex-
posed (the opposite side is unknown). Lamina is thick.
Pinnae are 3.6 cm long, 0.5–0.6 cm wide, closely set,
and attach to the lateral side of the rachis at 70°. The
base of the pinnae is neither contracted nor expanded.
The acroscopic margin of the pinnae is nearly straight
while the basiscopic margin gradually curves toward the
apex from the distal third of the pinnae, so that the apex
is asymmetrically rounded. Each pinna is entered by 9–
12 veins, which fork several times before ending at the
margin. The maximum concentration of veins is ca. 20
per cm.
Comparison.―The specimen is similar to P. cheon-
daeriense from the Upper Triassic Amisan Formation,
Cheondaeri, Korea in the closely set pinnae and in the
number of ribs on the rachis and number of veins enter-
ing each pinnae (Kimura and Kim, 1989), but is distin-
guished from it by the veins forking at all levels and the
pinnae with asymmetric rounded apex. This specimen
could be assigned to a new species, but further observa-
tions on additional specimens would be required.
Genus Ptilophyllum Morris, 1840
Ptilophyllum caucasicum Doludenko et Svanidze, 1964
Ptilophyllum caucasicum Doludenko et Svanidze, 1964, p. 113–118,
pl. 1, gs. 1–13; pl. 2, gs. 1–10; Doludenko et Svanidze, 1969,
p. 65–67, pl. 70, gs. 1–10; pl. 71, gs. 1–9.
Specimens.―NSMPP9906 (Figures 4G, H), NSM
PP9904 (Figure 5A), NSMPP9908 (Figure 5B), NSM
PP9907 (Figure 5C), NSMPP9909 (Figure 4I).
Locality.―Horadani, Kaizara area (NSMPP9904
9909, 9923)
Description.―The apicalmost and basalmost parts of
the leaf are not preserved. Leaf was probably more than
10 cm long. Leaf slightly tapers towards both its ends,
is less than 1.4 cm wide at the apex, 1.7–2 cm wide in
the middle, and 1.2 cm wide near the base. Rachis of
pinnae is ca. 1 mm wide. Pinnae attach suboppositely
to the upper side of the rachis at about 60°. Size of the
pinnae varies gradually along the proximaldistal axis
of the leaf: they are 4 mm wide and 8 mm long near the
distal end, 6 mm wide and 10 mm long at the middle
part, and 3 mm wide and 6 mm long at the basal part.
The pinnae on the same side of the rachis are imbricate.
Apex of the pinnae is obtuse. Acroscopic base of the
pinnae is not contracted while basiscopic base is slightly
decurrent. About seven veins arising from the pinnae
base sometimes fork a few times and the concentration
of veins becomes 20–30 per cm at the middle of the
pinnae length. Veins on the basiscopic and acroscopic
sides diverge slightly while the other veins run almost
parallel.
Comparison.―Specimens collected are identied as
P. caucasicum, originally described from the Callovian
of Georgia, based on concentration of veins and imbri-
cated pinnae (Doludenko and Svanidze, 1964, 1969). P.
caucasicum shows variations in its pinnae shape, i.e.,
from short pinnae with rounded apex to long pinnae with
pointed apex (Doludenko and Svanidze, 1964, 1969).
The specimens in hand are comparable to the shorttype
pinnae of P. caucasicum.
The specimens resemble P. shinadaniense from the
Lower Jurassic Kuruma Group of Toyama Pref., Japan
in their imbricate narrow pinnae (Kimura and Tsuji,
1982). However, the specimens are distinguished from
P. shinadaniense because P. shinadaniense invariably
has more elongate pinnae. They are also similar to P.

Toshihiro Yamada and Kazuhiko Uemura10
hsingshanensis from the Middle Jurassic Xietan Forma-
tion of Hubei, China (Sze, 1949; Wu et al., 1980), but
that species differs from our specimens in its narrower
pinnae. P. guliqiaoense from the Early Cretaceous of
Zhejiang, China also has convex and wide pinnae, but is
distinguished from our specimens in having frequently
forked veins (Cao, 1999). P. cutchense and P. sahnii
from the Middle to Upper Jurassic of Kachchh, India
have similar venation and leaf shape (Gupta and Sharma,
1968; Bose and Kasat, 1972), while our specimen has
broader pinnae (i.e., > 3 mm) than those species.
Two Japanese Ctenozamites species identied based
on their external morphologies are similar to our speci-
mens: Ctenozamites sp. from the Lower Cretaceous
Oguchi Formation of Ishikawa Pref. (Kimura and
Sekido, 1976b) and C. fukutomii from the Upper Juras-
sic to Lower Cretaceous Kiyosue Formation (sensu
Yamada and Ohno, 2005) of Yamaguchi Prefecture
(Kimura and Ohana, 1987b). They have distinctly iso-
lated pinnae, while laminar segments of other Ctenoza-
mites species are never isolated completely from adja-
cent segments, even in a species with highly dissected
lamina (e.g., Schenk, 1887; Harris, 1961b, 1964, 1969).
C. sp. is similar to our specimens in their pinnae shape,
but our specimens can be distinguished from it in pinnae
set more closely and less crowded veins. C. fukutomii is
also similar to our specimens in pinnae shape, but it dif-
fers in that its pinnae are not imbricate. Thus, they are
actually species of the genus Ptilophyllum.
Ptilophyllum sp. A
Specimens.―NSMPP9905 (Figure 5D), NSMPP
9923 (Figure 5E, F).
Locality.―Horadani, Kaizara area.
Description.―The basalmost part of the leaf is not
preserved. Leaf is probably more than 8 cm long and
slightly tapers towards apex: less than 0.8 cm wide at
the apex, 1.5 cm wide in the middle. Rachis with 0.5
mm width is covered by pinnae with slight exposure
in its central part. Pinnae are ca. 2 mm wide and 6 to 8
mm long and closely attach suboppositely to the upper
side of the rachis at 50 to 60 degrees. The pinna apex is
obtusely rounded. The acroscopic base of the pinnae is
slightly contracted while the basiscopic base is decur-
rent. Eight or nine veins arise from the pinnae base and
fork once or twice. The concentration of veins is 40 to
50 per cm. The veins run almost parallel.
Comparison.―The specimens obtained are indistin-
guishable in external morphology both from P. cutch-
ense, which was reported from the Middle to Upper Ju-
rassic of Kachchh, India by Bose and Kasat (1972), and
P. choshiense from the Choshi Group of Japan (Kimura
et al., 1991). However, the diagnostic features of both
species are on their epidermis, and thus we could not
assign our specimens to those species. This specimen
closely resembles Ptilophyllum ex gr. P. pecten from
the Yuasa and Arida formations of Japan (Kimura and
Kansha, 1978).
Ptilophyllum sp. B
Specimen.―NSMPP9918 (Figures 5G, H).
Locality.―Taniyamadani, Shimoyama area.
Description.―Specimen is a leaf fragment without
basal and apical part 3 cm long and 5 cm wide. Apex of
pinnae is missing. Rachis of pinnae is completely cov-
ered by pinnae. Pinnae are ca. 0.4 cm wide and more
than 2.5 cm long and attach suboppositely to the upper
side of the rachis at 60°. Pinnae on the same side are
imbricate. Acroscopic base of the pinnae is slightly con-
tracted while basiscopic base is decurrent. Eight or nine
veins arise from the pinnae base and fork once or twice.
Concentration of veins is 20 to 30 per cm. Veins run al-
most parallel.
Comparison.―The specimen resembles the elongate
pinnae type of P. caucasicum (Doludenko and Svanidze,
1969) in pinnae shape and the number of veins entering
each pinnae. Taking into account that some specimens
of P. caucasicum of the shortpinnae type were collected
at the same locality, this specimen might be the long
pinnae type of P. caucasicum. P. elongatum Kimura and
Ohana from the Lower Cretaceous Choshi Group of
Japan also has elongate pinnae (Kimura and Ohana,
1984; Kimura et al., 1991), but its pinnae width is about
half that of our specimen.
Class Cycadopsida
Order Cycadales
Family uncertain
Genus Pseudoctenis Seward, 1911
Pseudoctenis? sp.
Specimen.―NSMPP9902 (Figures 5IK).
Locality.―Taniyamadani, Shimoyama area.
Description.―Leaf fragment 11.5 cm long and 11 cm
wide, pinnae on one side of the rachis are not preserved.
The rachis is marked with ne longitudinal striations,
stout, and 1.1 cm wide. Pinnae are 11 cm long and vary
in width along their length; they are 4 mm wide at the
base, 5 mm wide at the middle and then taper to a point-
ed apex. Pinnae attach to the upperlateral side of the
rachis at 70°. Base of the pinnae slightly contracted on
both acroscopic and basiscopic sides and a crescentic
mound is developed at the base. Intervals between the
pinnae are ca. 4 mm. Veins are seldom forked and at

Middle Jurassic Kaizara ora 11
Figure 5. A–C. Ptilophyllum caucasicum Doludenko et Svanidze. A. NSMPP9904. B. NSMPP9908. C. NSMPP9907. D–F.
Ptilophyllum sp. A. D. NSMPP9905. E. NSMPP9923. F. Line drawing of E. G. Ptilophyllum sp. B, NSMPP9918. H. Line drawing of G.
I. Pseudoctenis? sp., NSMPP9902. J. Closeup of I. K. Line drawing of I. A–E, G–K. Scale bars = 1 cm.

Toshihiro Yamada and Kazuhiko Uemura12
concentrations of up to 35–40 per cm.
Comparison.―Pinnae of genus Zamites (Benneti-
tales) also have an equally contracted base and attach to
the upper side of the rachis. Unfortunately, the epider-
mal features essential for distinguishing Zamites from
Pseudctenis are not preserved in our specimen. There-
fore, the possibility could not be ruled out that the speci-
men belongs to Zamites.
The specimen is similar to Pseudctenis sp. reported
from the Callovian of Elburz, Iran by Barnard and Mill-
er (1976) in the narrow pinnae attaching to the upperlat-
eral side of a stout rachis by a slightly contracted base.
However, the veins in the pinnae are more crowded in
this specimen than in Barnard and Miller’s (1976) speci-
men. Our specimen is also similar to P. fragilis from the
Middle Jurassic of Kachchh, India in the shape of the
pinnae base, but that species has less crowded veins on
the pinnae (Bose and Banerji, 1984).
The specimen is also similar to Pterophyllum pachyra-
chis from Mochiana, although this species is included
in a different genus (Oishi, 1940; Kimura and Ohana,
1987b). Our specimen resembles it in narrow pinnae
attached to the upperlateral side of a broad rachis, but
differs from P. pachyrachis in the more elongate pinnae
and acuminate pinna apex.
Class Coniferopsida
Order Coniferales
Family uncertain
Formgenus Elatocladus Halle, 1913
Elatocladus sp.
Specimen.―NSMPP9911 (Figures 6A, B).
Locality.―Taniyamadani, Shimoyama area.
Description.―A fragment of shoot without base and
apex 6 cm long and 2.5 cm wide. Stem is 1.5 mm wide
and bears helically arranged scale leaves with faint mid-
rib. Angle between adjacent leaves is usually 60 to 80
degrees, but the phyllotaxy is uncertain, because some
of the leaves are not observed in the compressed speci-
men. The leaves are compressed along the adaxialabax-
ial axis, are linear in shape and have an acuminate apex.
They attach to the stem almost at right angles via their
decurrent base, while the angles between the leaf and
stem become smaller near the shoot apex. The leaves are
1–1.2 cm long, and 1–1.5 mm wide in the part free from
the stem.
Comparison.―The specimen is closely similar to E.
zamioides from the Middle Jurassic of Yorkshire, UK
in angle between adjacent scale leaves, and leaves with
short petiole and acuminate apex (Harris, 1979). How-
ever, E. zamioides differs from the specimen in having
opposite and more elongate leaves.
Formgenus Pagiophyllum Heer, 1881
Pagiophyllum? sp.
Specimen.―NSMPP9910 (Figures 6C, D).
Locality.―Taniyamadani, Shimoyama area.
Description.―A shoot fragment 6.2 cm long and 1.5
cm wide. The apex and base of the shoot are not pre-
served. The stem is 1.8 mm wide. Leaves are arranged
helically and sparsely, but phyllotaxy is uncertain be-
cause the specimen is obliquely compressed. The free
parts of the leaves are 6–8 mm long and 3–3.5 mm wide,
and the angle between the stem and free parts of the leaf
is ca. 90°. The base of the leaves is slightly contracted
and the decurrent part is 3 mm wide. The apex of the
leaves is obtuse. The adaxial surface of the leaves is
convex, while the abaxial one is not observed in the
compressed specimen.
Comparison.―The specimen is too compressed to
examine the thickness of the leaves, which is one of the
generic diagnostic features of Pagiophyllum. However,
as to the diagnostic characters which could be observed
in the specimen, it is similar to Pagiophyllum: the leaves
are longer and slightly broader than their decurrent base.
Among Pagiophyllum species, the specimen is similar
to P. kurrii from the Lower Jurassic of Germany and the
Middle Jurassic of Yorkshire, UK in their sparsely set
leaves and slightly contracted leaf base (Salfeld, 1907;
Harris, 1979).
Discussion
Characteristics of the Kaizara Flora
Here, the name Kaizara ora is proposed for the Mid-
dle Jurassic (Bathonian to Callovian) plant fossils from
the Kaizara Formation. In addition to already described
Otozamites sewardii (Oishi, 1940), twelve species are
newly reported; they belong to Equisetales, uncertain
order of pteridosperms, Cycadeoideales, Cycadales, and
Coniferales (Table 1). Most of these gymnospermous
taxa have very thick lamina. The ora is most character-
ized by abundant microphyllous cycadeoidealean taxa
(sensu Ziegler et al., 1996; Rees et al., 2000), such as
Otozamites and Ptilophyllum species. Scantiness of pte-
ridophytes and absence of ginkgophytes and Nilssonia
are other prominent features of the ora. Despite ex-
tensive searches over twenty years, such taxa were not
discovered from the area, except for small fragments of
Gleicheniteslike pinnule (data not shown in this study).
The offshore sedimentary environments of the Kaizara
Formation are a possible cause of the peculiar assem-
blage, but this can not fully explain the taphonomic bias,
because these underrepresented taxa are often recovered
from offshore sediments from other formations such as

Middle Jurassic Kaizara ora 13
the Toyora Group (Yamada and Ohno, 2005), the Yezo
Group (Oishi, 1940), the Choshi Group (Kimura and
Okubo, 1985), and the Kamihambara Formation of the
Tetori Group (T. Yamada, unpublished data).
Multivariate statistical analysis was conducted to
assess the distributional link among 57 foliar genera
reported from the Jurassic strata of the Northern Hemi-
sphere and the results were further correlated to the
paleoclimate (Ziegler et al., 1993, 1996; Rees et al.,
2000). As a result, it was suggested that the microphyl-
lous cycadophytes and conifers favored a climate under
which dry conditions prevailed at least during a part
of a year, while macrophyllous conifers and ginkgo-
phytes favored cool temperate conditions. Other foliar
genera, such as those of some pteridophytes, conifers
and macrophyllous cycadophytes, show the maximum
abundance of their diversity in warm temperate climates
(Rees et al., 2000). The Kaizara ora includes abundant
species of microphyllous cycadophytic and coniferous
genera (Otozamites, Ptilophyllum and Pagiophyllum), as
well as species of Equisetites, Anomozamites, Pterophyl-
lum, and Elatocladus which are indicators of a warm
temperate climate. This would suggest that the Kaizara
ora grew under a seasonally wet climate. The leaf
physiognomy observed in species of the Kaizara ora,
i.e., leaves with very thick lamina, would support the
existence of dry period(s) in the climate.
Only two coeval late Bathonian to Callovian oras
were reported whose ages are unequivocally controlled,
one from the Caucasian Province, Georgia (Doludenko
and Svanidze, 1969) and the other from Elburz, Iran
(Barnard and Miller, 1976). These two oras are similar
to the Kaizara ora in the abundance of Otozamites and
Figure 6. A. Elatocladus sp., NSMPP9911. B. Line drawing of A. C. Pagiophyllum? sp., NSMPP9910. D. Line drawing of C.
Scale bars = 1 cm.
Table 1. List of the Kaizara ora. Figures show the number of
collected specimens.
Species Kaizara Shimoyama
Pteridophyte
(Equisetales)
Equisetites sp.
Gymnosperms
(Pteridosperms)
Ctenozamites usnadzei
Doludenko & Svanidze
(Cycadeoideales)
Anomozamites sp.
Otozamites crassipinnatus
T. Yamada & Uemura
O. sewardi Oishi
O. sp.
Pterophyllum sp.
Ptilophyllum caucasicum
Doludenko & Svanidze
Ptilophyllum sp. A
Ptilophyllum sp. B
(Cycadales)
Pseudoctenis? sp.
(Coniferales)
Elatocladus sp.
Pagiophyllum? sp.
1
2
1
9
2
1
1
1
2
1
1
1
1
1

Toshihiro Yamada and Kazuhiko Uemura14
Ptilophyllum species. However, the Kaizara ora differs
from these in the occurrence of the genera Equisetites
and Elatocladus, which would favor the interpretation
of a warm temperate climate (Rees et al., 2000).
Stratigraphic signicance
This study has clearly shown that there is no common
species between the Kaizara and other Tetoritype oras
proposed in the Tetori Group. Taking the late Bathonian
to Callovian age of the Kaizara ora into account, this
result implies that the Tetoritype ora appeared later
than the Callovian in the land of the Tetori Group. Based
on a recently compiled stratigraphic scheme (Fujita,
2003; Figure 2), the oldest records of the Tetoritype
ora in the Tetori Group are those from the Tithonian
Ashidani (formerly assigned to the Ochiai Formation:
Kimura, 1958) and Ushimaru formations (Kimura, 1958;
Maeda, 1961a, b).
The exact age of the Jurassic and Lower Cretaceous
strata is difcult to establish paleontologically in East
Asia except for Far East Russia and Japan since they
consist mostly of nonmarine deposits (e.g., Arkell, 1956;
Chen et al., 1982). Therefore, phytostratigraphy could
be a powerful tool by which to correlate the Jurassic
and Lower Cretaceous strata if it is worked out in Japan
and Far East Russia where marine and terrestrial facies
are often intercalated (Sato et al., 1963; Sato, 1992;
Kirillova and Kiriyanova, 2003). Oishi (1933a, b, 1940)
stressed the signicance of Onychiopsis, a pteridophyte
genus unclassied as to family, in Japanese Jurassic
to Cretaceous biostratigraphy when he proposed an
“Onychiopsis Series” as a local chronozone ranging from
the Oxfordian to early Cretaceous. In his study, the rst
appearance of O. elongata (Geyler) Yokoyama, a repre-
sentative of the Tetoritype ora (e.g., Kimura, 1988),
was estimated as the Oxfordian in the Tetori Group.
Later, his claim was dismissed as socalled middle Juras-
sic assemblages including Onychiopsis were proposed,
such as the “Kuzuryu” and “Utano” oras. However,
recent progress in stratigraphy of the Mesozoic System
indicates that this counterevidence for the lower limit
of the “Onychiopsis Series” is no longer sustainable
(Yamada et al., 1989; Fujita, 2002; Sato et al., 2003;
Sato and Yamada, 2005; Yamada and Ohno, 2005).
Results of this study also suggested the postOxfordian
appearance of Onychiopsis in the Tetori Group.
As far as the Mesozoic strata of Japan are concerned,
the appearance of Onychiopsis after the Oxfordian seems
to be sound because O. yokoyamai, another Onychiopsis
species reported from Japan (Kimura and Aiba, 1986),
is found in postOxfordian deposits (Kimura and Ohana,
1989; Kimura et al., 1990). In Far East Russia, the old-
est reliable record of the genus is O. elongata from
the Berriasian of Amur and Lena provinces (Kirillova
and Kiriyanova, 2003). Volynets (1997) compared the
Onychiopsisbearing Alexeevsky oristic assemblage
to the Utano ora and considered its age as Aalenian to
Bathonian, following the previous age estimate on the
Utano ora (Kimura et al., 1986; Kimura and Ohana,
1987a). However, the age of the Utano ora is now re-
vised to Late Jurassic to Early Cretaceous (Yamada and
Ohno, 2005). Therefore, the appearance of Onychiopsis
after the Oxfordian is also applicable to Far East Russia,
implying that its appearance after the Oxfordian could
be a shared event in Eastern Asia.
Acknowledgments
I thank K. Hachiya, T. Hayashi and Y. Mizuno for
providing materials used in this study. M. Kato and T.
Sato kindly revised this manuscript. This study is partly
supported by a research project of the National Museum
of Nature and Science, entitled “Historical development
and origin of biodiversity under the global environmen-
tal dynamics”.
References
Arkell, W. J., 1956: Jurassic Geology of the World, 806 p. Oliver and
Boyd, Edinburgh.
Barbacka, M., Pálfy, J. and Smith, P. L., 2006: Hettangian (Early
Jurassic) plant fossils from Puale Bay (Peninsular terrane,
Alaska). Review of Palaeobotany and Palynology, vol. 142, p. 33
–46.
Barbacka, M. and van Konijnenburgvan Cittert, J. H. A. 1998: Sun
and shade leaves in two Jurassic species of pteridosperms. Review
of Palaeobotany and Palynology, vol. 103, p. 209–221.
Barnard, P. D. W. and Miller, J. C., 1976: Flora of the Shemshak For-
mation (Elburz, Iran), Part 3: Middle Jurassic (Dogger) plants
from Katumbargah, Vasek Gah and Imam Manak. Palaeonto-
graphica, Abt. B, vol. 155, p. 31–117.
Bose, M. N. and Banerji, J., 1984: The fossil oras of Kachchh. I–
Mesozoic megafossils. Palaeobotanist, vol. 33, p. 1–189.
Bose, M. N. and Kasat, M. L., 1972: The genus Ptilophyllum in India.
Palaeobotanist, vol. 19, p. 115–145.
Bose, M. N. and ZebaBano, 1981: On a new species of Otozamites
from Kachchh, western India. Palaeobotanist, vol. 27, p. 227–
231.
Braun, C. F. W., 1843: Beiträge zur Urgeschichte der Panzen. In
Münster, G. ed., Beiträge zur Petrefactenkunde. Heft 6, p. 1–33.
Bayreuth.
Brongniart, A., 1828: Prodrome d’une histoire des végétaux fossiles.
Dictionnaire des Sciences Naturelles, vol. 57, p. 61–212.
Cantrill, D. J. and Hunter, M. A., 2005: Macrofossil oras of the
Latady Basin, Antarctic Peninsula. New Zealand Journal of Geol-
ogy and Geophysics, vol. 48, p. 537–553.
Cao, Z., 1999: Early Cretaceous ora of Zhejiang. Palaeontologia
Sinica, New Series A, no. 13.
Chen, P., Li, W., Chen, J., Ye, C., Wang, Z., Shen, Y. and Sun, D.,
1982: Stratigraphical classication of Jurassic and Cretaceous in
China. Scientia Sinica, Series B, vol. 25, p. 1227–1248.
Doludenko, M. P. and Svanidze, T. I., 1964: Some Jurassic Ptilophyl-

Middle Jurassic Kaizara ora 15
lum fronds of Ukraine and Georgia and their correlation with
Indian species of this genus. In, International Geological Con-
gress 22nd Session. Report of Soviet Geologists. Problem 9, p.
111–122. Nauka, Moscow. (in Russian)
Doludenko, M. P. and Svanidze, T. I., 1969: The Late Jurassic ora of
Georgia. Transactions of Geological Institute, Academy of Sci-
ences of USSR, vol. 178, p. 1–118. (in Russian)
Douglas, J. G., 1963: New bennettitalean leaves from the Mesozoic
of eastern Australia. Proceedings of the Royal Society of Victoria,
vol. 77, p. 197–206.
Feistmantel, O., 1876: Fossil ora of Gondwana System. Jurassic
(Oolitic) ora of Kach. Memoirs of Geological Survey of India,
Palaeontologia Indica, Series 11, vol. 2, p. 1–80.
Fujita, M., 2002: A new contribution to the stratigraphy of the Tetori
Group, adjacent to Lake Kuzuryu, Fukui Prefecture, Central
Japan. Memoir of the Fukui Prefectural Dinosaur Museum, vol. 1,
p. 41–53.
Fujita, M., 2003: Geological age and correlation of the vertebrate
bearing horizons in the Tetori Group. Memoir of the Fukui Prefec-
tural Dinosaur Museum, vol. 2, p. 3–14.
Geyler, H. T., 1877: Über fossile Panzen aus der Juraformation
Japans. Palaeontographica, vol. 24, p. 221–232, pls. 30–34.
Goto, M., 2007: An Early Cretaceous ammonoid from the Itoshiro
Subgroup of the Tetori Group in the Uchinami River area of Ohno
City, Fukui Prefecture, Central Japan. Memoir of the Fukui Pre-
fectural Dinosaur Museum, vol. 6, p. 27–34. (in Japanese with
English abstract).
Gupta, K. M. and Sharma, B. D., 1968: Investigations on the Jurassic
ora of the Rajmahal Hills, India. 2On a new species of Ptilo-
phyllum, P. sahnii from Amarjola in Amarapara region. Journal of
the Palaeontological Society of India, vol. 11, p. 19–66.
Halle, T. G., 1913: The Mesozoic ora of Graham Land. Wissen-
schaftliche Ergebnisse der Schwedischen Südpolar-Expedition,
1901–1903, vol. 3, p. 1–122.
Harris, T. M., 1926: The Rhaetic ora of Scoresby Sound, east Green-
land. Meddelelser om Grønland, vol. 68, p. 44–148.
Harris, T. M., 1949: Notes on the Jurassic ora of Yorkshire, 40–42.
40. Otozamites anglica (Seward) comb. nov.; 41. The narrow
leaved Otozamites species; 42. Ptilophyllum hirsutum Thomas
and Bancroft and its differentiation from P. pecten (Phillips.).
Annals and Magazine of Natural History, London, ser. 12, vol. 1, p.
275–299.
Harris, T. M., 1961a: The Yorkshire Jurassic ora I. Thallophyta-
Pteridophyta. British Museum (Natural History), London.
Harris, T. M., 1961b: The form and structure of Ctenozamites cycadea
(Berger) Schenk. Bulletin of the British Museum (Natural
History) Geology, vol. 5, p. 159–173, pls. 31–32.
Harris, T. M., 1964: The Yorkshire Jurassic ora II. Caytoniales,
Cycadales and Pteridosperms. British Museum (Natural History),
London.
Harris, T. M., 1969: The Yorkshire Jurassic ora III. Bennettitales.
British Museum (Natural History), London.
Harris, T. M., 1979: The Yorkshire Jurassic ora V. Coniferales.
British Museum (Natural History), London.
Heer, O., 1881: Contributions à la ore fossile de Portugal. Lisbon.
Kimura, T., 1958: On the Tetori ora (Part 1). Mesozoic plants from
the Kuzuryu SubGroup, Tetori Group, Japan. Bulletin of the
Senior High School attached to the Tokyo University of Educa-
tion, vol. 2.2, p. 1–47.
Kimura, T., 1975: MiddleLate Early Cretaceous plants newly found
from the upper course of the Kuzuryu River Area, Fukui Prefec-
ture, Japan. Transactions and Proceedings of the Palaeontogical
Society of Japan, New Series, no. 98, p. 55–93.
Kimura, T., 1987: Recent knowledge of Jurassic and Early Cretaceous
oras in Japan and phytogeography of this time in East Asia.
Bulletin of the Tokyo Gakugei University, Sect. 4, vol. 39, p. 87–
115.
Kimura, T., 1988: Jurassic macrooras in Japan and palaeophytogeog-
raphy in East Asia. Bulletin of the Tokyo Gakugei University,
Section 4, vol. 40, p. 147–164.
Kimura, T. and Aiba, H., 1986: Onychiopsis yokoyamai (Yabe) comb.
nov. from the Lower Cretaceous Plantbeds in the Outer Zone of
Japan. Bulletin of the National Science Museum, Tokyo, Series C,
vol. 12, p. 41–52.
Kimura, T. and Kansha, Y., 1978: Early Cretaceous plants from the
Yuasa District and the Aridagawa Valley, Wakayama Prefecture,
in the Outer Zone of Japan. Bulletin of the National Science
Museum, Tokyo, Series C, vol. 4, p. 99–116, pls. 1–4.
Kimura, T. and Kim, B. K., 1989: New taxa in the Late Triassic Dae-
dong ora, south Korea. Part 2. Transactions and Proceedings of
the Palaeontogical Society of Japan, New Series, no. 155, p. 141–
158.
Kimura, T. and Ohana, T., 1984: Ptilophyllum elongatum sp. nov.,
from the Lower Barremian Kimigahama Formation, the Choshi
Group, in the Outer Zone of Japan. Proceedings of the Japan
Academy, Series B, vol. 60, p. 381–384.
Kimura, T. and Ohana, T., 1987a: Middle Jurassic and some Late Lias-
sic plants from the Toyora Group, southwest Japan (I). Bulletin of
the National Science Museum, Tokyo, Series C, vol. 13, p. 41–76.
Kimura, T. and Ohana, T., 1987b: Middle Jurassic and some Late Lias-
sic plants from the Toyora Group, southwest Japan (II). Bulletin
of the National Science Museum, Tokyo, Series C, vol. 13, p. 115–
148.
Kimura, T. and Ohana, T., 1989: Late Jurassic plants from the Ogino-
hama Formation, Oshika Group in the Outer Zone of Northeast
Japan (I). Bulletin of the National Science Museum, Tokyo, Series
C, vol. 15, p. 1–24.
Kimura, T. Ohana, T. and Aiba, H., 1990: Late Jurassic plants from
the Shishiori Group, in the Outer Zone of Northeast Japan (I).
Bulletin of the National Science Museum, Tokyo, Series C, vol.
16, p. 127–153.
Kimura, T., Ohana, T., Kurihara, Y. and Komori, K., 1986: Middle
Jurassic Utano ora and its signicance for biostratigraphy and
palaeophytogeography in East Asia (abstract). Proceedings of the
Japan Academy, Series B, vol. 62, p. 341–344.
Kimura, T. and Okubo, A., 1985: Nilssonia dictyophylla sp. nov. from
the Lower Cretaceous Choshi Group, in the Outer Zone of Japan.
Proceedings of the Japan Academy, Series B, vol. 61, p. 430–432.
Kimura, T., Okubo, A. and Miyahashi, H., 1991: Cuticular study of
Ptilophyllum leaves from the Lower Cretaceous Choshi Group,
in the Outer Zone of Japan. Bulletin of the National Science
Museum, Tokyo, Series C., vol. 17, p. 129–152.
Kimura, T. and Sekido, S., 1976a: Dictyozamites and some other
cycadophytes from the early Lower Cretaceous Oguchi Forma-
tion, the Itoshiro Group, Central Honshu, Japan. Transactions and
Proceedings of the Palaeontogical Society of Japan, New Series,
no. 101, p. 291–312, pls. 30–32.
Kimura, T. and Sekido, S., 1976b: Mesozoic plants from the Akaiwa
Formation (Upper Neocomian), the Itoshiro Group, Central Hon-
shu, Japan. Transactions and Proceedings of the Palaeontogical
Society of Japan, New Series, no. 103, p. 343–378, pls. 36–39.
Kimura, T., Sekido, S. and Yamazaki, Y., 1978: Plant fossil assemblage
from the Oguchi and the Akaiwa Formations of the Itoshiro Sub-
group, with special emphasis on the fossils from the Shiramine
Village, Ishikawa Pref., central Japan. In, Ishikawa Prefectural
Board of Education, ed., Research report on the silicied wood
localities of the Tetori Group along the Tedori River, p. 119–271.
Ishikawa Prefectural Board of Education, Japan (In Japanese).

Toshihiro Yamada and Kazuhiko Uemura16
Kimura, T. and Tsuji, M., 1982: Early Jurassic plants in Japan. Part 4.
Transactions and Proceedings of the Palaeontogical Society of
Japan, New Series, no. 125, p. 259–276.
Kirillova, G. L. and Kiriyanova, V. V., 2003: J/K boundary in South-
eastern Russia and possible analogue of the Tetori Group, Japan.
Memoir of the Fukui Prefectural Dinosaur Museum, vol. 2, p. 75–
102.
Konno, E. and Asama, K., 1973: Contributions to the geology and
palaeontology of Southeast Asia, 122. Mesozoic plats from
Khorat, Thailand. Geology and Palaeontology of Southeast Asia,
vol. 12, p. 149–171.
Kusuhashi, N., Matsumoto, A., Murakami, M., Tagami, T., Hirata,
T., Iizuka, T., Handa, T. and Matsuoka, H., 2006: Zircon UPb
ages from tuff beds of the upper Mesozoic Tetori Group in the
Shokawa district, Gifu Prefecture, central Japan. Island Arc, vol.
15, p. 378–390.
Leckenby, G., 1864: On the sandstones and shales of the oolites of
Scarborough, with descriptions of some new species of fossil
plants. Quarterly Journal of the Geological Society, vol. 20, p.
74–82.
Maeda, S., 1952: A stratigraphical study on the Tetori Series in the
Upper Shiokawa District in Gifu Prefecture. Journal of the Geo-
logical Society of Japan, vol. 58, p. 145–153. (in Japanese)
Maeda, S., 1956: Stratigraphy and geological structure of the Tetori
Group on the borderland of Fukui and Gifu Prefectures. Journal
of the Geological Society of Japan, vol. 63, p. 225–237. (in Japa-
nese)
Maeda, S., 1960: Stratigraphy of the Tetori Group in the southern part
of the Kuzuryu River, Fukui Prefecture. Journal of the Geological
Society of Japan, vol. 67, p. 23–31. (in Japanese)
Maeda, S., 1961a: On the geological history of the Mesozoic Tetori
Group in Japan. Journal of College of Arts and Sciences, Chiba
University. Natural Sciences Series, vol. 3, p. 369–426. (in Japa-
nese)
Maeda, S., 1961b: The Tetori Group along the Asuwa River in Fukui
Prefecture. Journal of Geography, vol. 70, p. 65–69.
Matsukawa, M., Ito, M., Nishida, N., Koarai, K., Lockley, M. G. and
Nichols, D. J., 2006: The Cretaceous Tetori biota in Japan and its
evolutionary signicance for terrestrial ecosystems in Asia. Creta-
ceous Research, vol. 27, p. 199–225.
Morris, J., 1940: Typication of Ptilophyllum. In, Grant, C. W.,
Memoir to illustrate a geological map of Cutch. Transactions of
the Geological Society, London, vol. 5, p. 289–329, pls. 20–26.
Nathorst, A. G., 1886: Om oran i Skånes kolförande Bildingar. I.
Floran vid Bjuf. Sveriges Geologiska Undersökning Serie C, vol.
85, p. 83–116.
Oishi, S., 1933a: On the Tetori Series, with special references to its
fossil zones. Part 1. Journal of the Geological Society, Tokyo, vol.
40, p. 617–644. (in Japanese)
Oishi, S., 1933b: On the Tetori Series, with special references to its
fossil zones. Part 1. Journal of the Geological Society, Tokyo, vol.
40, p. 669–699. (in Japanese)
Oishi, S., 1940: The Mesozoic oras of Japan. Journal of the Faculty
of Sciences, Hokkaido Imperial University, Section 4, vol. 5, p.
123–480.
Rees, P. McA., Ziegler, A. M. and Valdes, P. J., 2000: Jurassic phy-
togeography and climates: new data and model comparisons. In,
Huber, B. T., Macleod, K. G. and Wing, S. L. eds., Warm climates
in Earth history, p. 297–318. Cambridge University Press, Cam-
bridge.
Salfeld, H., 1907: Fossile LandPanzen der Rät und Juraformation
Südwestdeutschlands. Palaeontographica Stuttgart, vol. 53, p.
164–204.
Saporta, G., 1873–1875: Paléontologie française ou description des
fossils de la France (2, Végétaux), Plantes jurassiques, vol. II,
Cycadeés. 548 p. 74 pls., Paris.
Sato, T., 1962: Études biostratigraphiques des ammonites du Juras-
sique du Japon. Mémoires de la Société Géologique de France,
vol. 94, p. 1–122.
Sato, T., 1992: Southeast Asia and Japan. In Westermann, G. E. G.
ed., The Jurassic of the Circum Pacic, p. 194–213. Cambridge
University Press, Cambridge.
Sato, T., Hachiya, K. and Mizuno, Y., 2003: Latest JurassicEarly
Cretaceous ammonites from the Tetori Group in Shokawa, Gifu
Prefecture. Bulletin of the Mizunami Fossil Museum, vol. 30, p.
151–167.
Sato, T., Hayami, I., Tamura, M. and Maeda, S., 1963: The Jurassic.
In Takai, F., Matsumoto, T. and Toriyama, R. eds., Geology of
Japan, p. 79–98. University of Tokyo Press, Tokyo.
Sato, T. and Kanie, Y., 1963: Lilloetia sp. (Ammonite callovienne) de
Mitarasi au Bassin de Tetori. Transactions and Proceedings of the
Palaeontogical Society of Japan, New Series, no. 49, p. 8.
Sato, T. and Westermann, G. E. G., 1991: Japan and SouthEast Asia.
Jurassic taxa ranges and correlation charts for the CircumPacic,
6. Newsletter on Stratigraphy, vol. 24, p. 81–108.
Sato, T. and Yamada, T., 2005: A Lower Tithonian (Upper Jurassic)
ammonite Parapallasiceras newly discovered from the Itoshiro
Subgroup (Tetori Group) in Izumimura, Fukui Prefecture. Pro-
ceedings of the Japan Academy Series B, vol. 81, p. 267–272.
Schenk, A., 1887: Fossile Panzen aus der Albourskette. Bibliotheca
Botanica, Abhandlungen aus dem Gesammtgebiete der Botanik,
vol. 6, p. 1–12.
Schimper, W. P., 1870: Traité de paléontologie végétale, vol. 2. J. B.
Baillière et Fils, Paris.
Seward, A. C., 1911: The Jurassic ora of Sutherland. Transactions of
the Royal Society of Edinburgh, vol. 47, p. 643–709.
Sternberg, C. von, 1833. Versuch einer geognostischbotanischen
Darstellung der Flora der Vorwelt, Hefte 5, 6. 80 p., 22 pls.
Leipzig and Prague.
Sze, H. C., 1933: Beiträge zur mesozoischen Flora von China. Palae-
ontologia Sinica, Series A, vol. 4, p. 1–92.
Sze, H. C., 1949: Die mesozoische Flora aus der Hsiangchi Kohlen
Serie in Westhupeh. Palaeontologia Sinica, New Series A, vol. 2,
p. 1–71.
Takahasi, E., Uto, S., Mihara, A. and Takahasi, H., 1965: Palaeozoic
and Mesozoic formations of the eastern and the southern parts
of the Tabe Basin, Yamaguchi Prefecture. Science Reports of the
Yamaguchi University, vol. 15, p. 33–49. (in Japanese)
Vakhrameev, V. A., 1991: Jurassic and Cretaceous oras and climates
of the earth. Cambridge University Press, Cambridge.
Volynets, E. B., 1997: New data on the age of the Monakinsky
sequence, Partizansk coal basin. Tikhookeanskaya Geologiya, vol.
16, p. 135–139. (in Russian)
Wu, S. Q., Ye, M. N. and Li, B. X., 1980: Upper Triassic and Lower
and Middle Jurassic plants from the Hsiangchi Group, western
Hubei. Memoir of Nanjing Institute of Geology and Palaeontol-
ogy, Academia Sinica, vol. 14, p. 63–131. (in Chinese)
Yabe, A., Terada, K. and Sekido, S., 2003: The Tetoritype ora,
revisited: a review. Memoir of the Fukui Prefectural Dinosaur
Museum, vol. 2, p. 23–42.
Yamada, K., Niwa, S. and Kamata, M., 1989: Lithostratigraphy of the
Mesozoic Tetori Group in the upper reaches of the Kuzuryu River,
central Japan. Journal of the Geological Society of Japan, vol. 95,
p. 391–403. (in Japanese)
Yamada, T. and Ohno, T., 2005: Revision of the stratigraphy of the
Toyora and Toyonishi Groups in the OuchiKikugawa area,
Yamaguchi Prefecture, West Japan, Journal of the Geological
Society of Japan, vol. 111, p. 389–403.

Middle Jurassic Kaizara ora 17
Yamada, T., Yokoyama, K. and Kunugiza, K., 2005: Stratigraphic
correlation of Tetori Group in Asuwa River area based on chemo-
taxonomy of clastic particles in sandstone. Abstracts of the 112th
Annual Meeting of the Geological Society of Japan, p. 227. (in
Japanese)
Yokoyama, M., 1889: Jurassic plants from Kaga, Hida, and Echizen.
Journal of College of Science, Imperial University, Japan, vol. 3,
p. 1–66, pls. 1–14.
Zeiller, R., 1903: Flore fossile des gites de charbon du Tonkin (Études
des gîtes de minéraux de la France), Maison Quantin, Paris.
Zhou, Z., 1983: Early Liassic plants from southwest Hunan, China.
Palaeontologia Sinica, New Series A, no. 7.
Ziegler, A. M., Parrish, J. M., Yao, J., Gyllenhaal, E. D., Rowley, D.
B., Parrish, J. T., Shangyou, N., Bekker, A. and Hulver, M. L.,
1993: Early Mesozoic phytogeography and climate. Philosophical
Transactions of the Royal Society of London, Series B, vol. 341, p.
297–305.
Ziegler, A. M., Rees, P. M., Rowley, D. B., Bekker, A., Qing, L. and
Hulver, M. L., 1996: Mesozoic assembly of Asia: constraints
from fossil oras, tectonics, and paleomagnetism. In, Yin, A. and
Harrison, M. eds., The Tectonic Evolution of Asia, p. 371–400.
Cambridge University Press, Cambridge.