Vol. 12, No. 4, p. 331 − 336, December 2008
ⓒ The Association of Korean Geoscience Societies and Springer 2008
A new species of Acer samaras from the Miocene Yeonil Group in the Pohang
ABSTRACT: Acer pohangense sp. nov. belonging to Aceraceae is
described based on the six detached samaras collected from the
Duho Formation of the Miocene Yeonil Group. This species is
characterized by its comparatively large-sized samara with a wing
and seed, and its wide divergent angle. The occurrence of such a
large-sized samara is the first on record not only in the Korean
Tertiary floras, but also in the East Asian Tertiary floras.
Key words: Acer pohangense, Aceraceae, samara, Duho Formation,
Recently six detached samaras (Aceraceae) were collected
together with many other fossil plants from the Duho For-
mation of the Miocene Yeonil Group distributed along the
northern beach of Pohang-City. Although an organic con-
nection between the present samaras and Acer leaves has not
yet been found, it is highly probable that the samaras men-
tioned above belong to Acer (Aceraceae).
The Yeonil Group of marine origin has been known to
yield abundant plant fossils and marine fossils such as mol-
lusca, scaphopoda, gastropoda, corals, fish fossils, crab, etc
(Kanehara, 1936). Among them, plant fossils were described
by previous authors (Kryshtofovich, 1921; Oishi, 1935; Huz-
ioka, 1943a, b, 1951, 1954a, b, 1955, 1972; Endo, 1950a, b,
1951, 1953; Tanai, 1952, 1983; Lee, 1975; Chun et al., 1982;
Kim, 2005, 2008; Kim and Seo, 2007). The most recent
paleobotanical works for the wood fossils of the Pohang
Basin were made by Jeong et al. (2003, 2004).
Acer is one of the most common fossils in the Tertiary of
East Asia and western North America, especially predomi-
nant in the Neogene (Tanai, 1977; Wolfe and Tanai, 1987),
and also one of the most familiar trees to us in the temperate
floras (Suzuki, 1963). As mentioned by Talor and Talor
(1993), Acer is represented by generally monoecious trees
and shrubs with opposing leaves and regular flowers, and
the fruit of Acer is a two-winged schizocarp.
A large number of fossils such as fruits, seeds, and leaves
have been found in the Tertiary floras of the world (e.g.,
Oishi & Huzioka, 1943; Suzuki, 1963; Inst. Bot. and Inst.
Geol. and palaeont., Acad. Sin., 1978; Tanai, 1983; Wolfe &
Tanai, 1987). Pollen from the Acer has also been reported
from the Oligocene (Piel, 1971). The fossil species of Acer
have been found for 91 species from North America (Wolfe
& Tanai, 1987), more than 40 species from Europe, and 35
species from Japan (Suzuki, 1963; Tanai, 1983). In addition
to the species mentioned above, 13 species were described
from China (Inst. Bot. and Inst. Geol. and palaeont., Acad.
The Acer fossil species are represented by both foliage
and samara, and some are only foliage or samara, and most
of the fossil samaras are generally small in size. To date,
there have been no samaras or comparable species found
similar to the present samaras. This paper deals with the
description of Acer pohangense sp. nov. first found in the
Korean Tertiary flora. The presence of Acer pohangense
provides new evidence for biogeographic and climatic rela-
2. GEOLOGICAL SETTING AND FOSSIL LOCALITY
The Tertiary strata of the Pohang Basin are distributed in
the southeastern coast of South Korea, and are divided into
the Yangbuk and Yeonil Groups in ascending order (Kim,
1987). The former consists predominantly of basalt, volcanic
tuff, conglomerate, sandstone, shale and lignite, while the
latter mostly of clastic sediments of marine origin. The
Yangbuk Group is nearly equivalent to the Changgi (Janggi)
Series of Tateiwa (1924).
Since Tateiwa’s (1924) geological investigation on the
Pohang Basin, many geological and palaeontological studies
have been carried out by many authors (Um et al., 1964; Kim,
1965; Yoon, 1975, 1976, 1982, 1992; Lee, 1986; Yun, 1986,
1994; Lee et al., 1988; Chung and Choi, 1993 etc). Further
paleontological references for flora, fauna and microfossils
were shown by Tateiwa (1976), Lee (1987), Lim et al. (1994),
Kim (1997), Yoon and Yun (2001). and Lee et al. (2004).
As shown in the correlation of stratigraphic sequence of
the Yeonil Group in the Pohang Basin (Yoon, 1998), the
stratigraphic divisions of the Yeonil Group suggested by
some authors differ from each other. In the present study, the
Jong Heon Kim* Department of Earth Science Education, College of Education, Kongju National University, 182, Shink-
wan-dong, Kongju 314-701, Korea
*Corresponding author: firstname.lastname@example.org
332 Jong Heon Kim
stratigraphic terms are used which were suggested by Yun
(1986). According to Yun (1986), the Yeonil Group is divided
into the Chunbuk conglomerate, Hagjeon, and Duho For-
mation in ascending order. The fossil locality is shown in
The geological age of the Yeonil Group based on the fossil
plants and faunas and microfossils has generally been con-
sidered to be Middle Miocene (e.g., Tateiwa, 1924; Kane-
hara, 1936; Huzioka, 1972; Yoon, 1975; Yun, 1981; Chun et
3. MATERIAL AND METHOD
Six samaras were obtained from an outcrop of the Duho
Formation distributed along the northern beach of Pohang-
City, Kyeongbuk Province (129°24'50"E, 36°04'03"N). These
samaras are preserved as impressions in mudstone at a local-
ity where fossil plants and marine faunas are abundant. The
samaras were examined and mainly compared with samaras
of Acer known from Korea, East Asia and North America.
As shown in Figure 2, fossil fruits of Acer have been in most
cases found as single detached winged seeds and rarely as
two divergent winged seeds attached to a pedicel. In these
cases essentially the same technique that biologists employ
for investigating the exomorphic features of all extant spe-
cies was used on the fossil samaras.
The terminology of morphologic characteristics of Acer
fruit were illustrated in detail by Tanai (1983) and Wolfe and
Tanai (1987). The terminology as suggested by Tanai (1983)
is followed here. Major characteristics of Acer fruit are
shown in Figure 2. As mentioned by Tanai (1983), the fol-
lowing characteristics of samara are useful for classification;
size of samara, shape and thickness of seed, venation feature
on the seed surface, length of contact scar of seed, divergent
angles of its two wings, orientation of elongated seeds to the
wing, and presence of hairs covering the seeds. Tanai (1983)
also mentioned that the hairs and venation are generally of
less value in fossils, but most characteristics are usually well
defined in fossil samaras.
The specimens examined here will be kept at the Depart-
ment of Earth Science, Kongju National University.
4. SYSTEMATIC DESCRIPTION
Genus Acer Linne, 1753
Type species Acer amboyense Newberry 1895
Acer pohangense Kim sp. nov.
Figure 3. A~F
Material: Holotype; KNUM-980018, Paratype; KNUM-
2001007, 980024, 2001006.
Fig. 1. Geologic map of the Pohang
Basin (partly redrawn after Yi and
Yun, 1995) and fossil locality.
Fig. 2. Explanation of terms used in the description of Acer sama-
ras (Tanai, 1983).
A new species of Acer samaras from the Miocene Yeonil Group in the Pohang Basin, Korea 333
Locus typicus: Duhodong, Pohang-City.
Stratum typicum: Duho Formation of the Yeonil Group.
Derivatio nominis: This species is named after the geo-
logical name, Pohang near the locality.
Specific diagnosis: Samara large, 6.3 cm long and 2 cm
wide at the widest part near the base. Wing 3.8 cm long and
1.8 cm wide at the base. Length/width ratio 2.0 ~ 2.2. Mar-
gins nearly parallel-sided on the distal two thirds of the
wing, obtuse at the apex; inner margin nearly straight at the
distal two thirds and gradually narrowing to the tip. Outer
margin slightly convexed (covered) near junction with seed
and then nearly straight to the tip. Veins numerous, about 20
in number at the base, curving inwards and irregularly,
branching dichotomously, ending at the distal margin. Seed
part large and thick, semicircular in shape, about 1.5 cm in
diameter, seed about 0.9 cm in diameter contact line of the
seed 2.1 cm long. Angle between outer margin and contact
line of seed about 115°.
As shown in Figure 3, the present samaras are character-
ized by their long and broad wing on a large seed, and by
their wide divergent angles. Judging from the general outline
such as venation-type, junction with seed and wing, and the
presence of contact scar, it is highly probable that the present
samaras belong to the genus Acer. Accordingly, the present
samaras were arbitrarily placed into the genus Acer until
more information about this type of leaf and fruit is found.
Among more than 130 species of Acer hitherto known to
originate from the Tertiary floras of East Asia (Tanai, 1983)
and North America (Wolfe and Tanai, 1987), such long and
broad samaras with a wide divergent angle as in the present
specimens, have not yet been recorded. Although the whole
form of the leaf and fruit for their separate occurrence from
the vegetative leaf is as of yet unknown, a new specific
name is proposed for the present samaras, Acer pohangense
Among the 35 species of Acer known from East Asia, 25
species were associated with their samaras. The following
three species, Acer ezoanum, A. palaeo-platanoides, and A.
kokangenense are comparable in samara size to the present
species. Acer ezoanum established by Oishi and Huzioka
(1943) from the Tertiary strata of Japan and later in detail by
Tanai (1983) is most similar in size to the present species.
According to Tanai (1983), the size of samaras is 4.8 to
11cm long and 1.4 to 2.2 cm wide. But Acer ezoanum differs
from the present species by its short contact scar (0.5 to
1cm) as it relates to the length of the samara and ellipsoidal
seed (1.1 to 2.5 cm long and 0.5 to 1.1 cm wide). Acer
palaeo-platanoides and A. kokangenense both defined by
Endo (1950) from the Tertiary of Hamjindong Formation
and Janggi Group of Korea respectively are also similar in
samara-size to the present species. According to Endo
(1950), the size of Acer palaeo-platanoides and A. kokan-
genense is 5 cm long and 1.5 cm wide, 5.3 cm and 1.3 cm
wide respectively. The former is distinguished from the
present species by its oblong to oblanceolate samara with a
small seed (0.9 × 0.7 cm) and narrow divergent angle (120°).
The latter also differs from the present species by its trian-
gular and small samaras (1cm long) and by its short contact
line (1cm). According to Tanai (1983), Endo’s A. kokangen-
ense is conspecific to A. fatsiaefolium originally described
by Huzioka (1943) from the Tertiary flora of Korea.
In China, 13 species of Acer have been described from the
Palaeogene floras (Inst. Bot. and Inst. Geol. and Palaeont.,
Acad. Sin., 1978), but all of them clearly differ from the
present species by their small-sized samaras.
The known fossil fruits and leaves of Acer from North
America represent 91 species (Wolfe and Tanai, 1987).
Among these 91 species, the samaras of Acer busamarum,
A. busamarum busamarum, A. busamarum fingerrockense
are the largest group for any species of Acer. For example,
the overall length of samara of Acer busamarum fingerrock-
ense is 5.4 to 9.7 cm (typically 7.5 cm). Acer macrophyllum
also have a large samara (6.3 cm in length). However, all the
samaras mentioned above clearly differ from the present
species in the shape of samaras.
The samara of Acer grahamensis Knowlton et Cockerell
described by Wolfe and Tanai (1980) is similar in seed size
Fig. 3. Detached samaras of Acer pohangense sp. nov.
334 Jong Heon Kim
and samara length to the present species, but the former is
much narrower in width relative to the length of samara
(1 cm width).
In detached samaras, the divergent angle of the two wings
is determined by doubling the angle, which is measured
between the contact scar and the outer margin of the wing.
In most species of Acer, the divergent angles of the two
wings are generally less than 100° (Tanai, 1983). However,
the following five species have more than 100° between the
divergent angles of the two wings; Acer palaeo-platanoides,
A. proto-miyabei, A. palaeo-rufinerve, A. proto-japonicum,
and A. uemurae. The former two species have the largest
divergent angles and are 110° to 180° and 180° to 220°
respectively (Tanai, 1983). Acer proto-miyabei is to the most
similar in divergent angles to the present species, but the
former is characterized by its small-sized samaras (1.8 to
3.5 cm long and 0.7 to 1.1 cm wide) and short contact scar
(0.7 to 1.2 cm). The specific names of Acer proto-miyabei,
A. palaeo-rufinerve, and A. proto-japonicum suggested by
Van Gelderen et al. (2005) are followed here.
In general the length of contact scar in the fossils of Acer
samaras usually do not exceed 1.5 cm. In this point Acer
pohangense sp. nov., with a long contact scar, is unique and
quite different from any existing and previously described
fossil species. According to Lee (2006), extant 15 species of
Acer are now distributed in the Korean Peninsula. Among
them, Acer okamotoanum Nakai distributed in Ulleungdo is
comparable with the Acer pohangense sp. nov. in general
outline, but it is distinguished from the present species by its
small sized samaras (2 to 3 cm length, 1.5 to 1.8 cm width)
with small divergent angles.
The first taxonomic work of Acer fossils in Korea was
undertaken by Huzioka (1943) from the Tertiary strata of the
Table 1. List of Acer species recorded from the Korean Tertiary floras (Ablaev et al., 1993; Huzioka, 1972; Lim et al., 1994)
Pohang Tongcheon Gilju-MyeongcheonHyeryeongKogeonwon
A. ezoanum0 0 0
A. nordenskioldi00 0 0 0
A. subpictum00 0 0 0
A. pictum0 0 0 0
A. rotundatum0 0
A. diabolicum 0
A. palaeo-platanoides 0 0 0
A. proto-trifidium0 0 0 0
A. japonicum 0
A. miohenryi 0
A. cf. palaeodia bolicum 0
A. kotchkoriensis 0
A. endoanum 0
A. meisense 0
A. palaeo-diabolicum 0
A. palaeo-rufinerve 0
A. proto-japonicum 0
A. pseudoginnala 0
A. trilobatum var. productum 0
A. trilobatum tricuspidatum 0
A. miyabei 0
A. trilobatum 0
A. tricuspidatum 0
A. sp. cf. A. negundo
A. cuneatum 0
A. kokangense 0
A. koreanicum 0 0
A. fatsiaefolium 0 0
A. proto-miyabei 0
A new species of Acer samaras from the Miocene Yeonil Group in the Pohang Basin, Korea 335
Gilju-Myeongcheon district. Subsequently some short papers
on the Korean Tertiary floras including Acer were published
by Endo (1950, 1951) and Tanai (1952). The most compre-
hensive and descriptive work on the Korean Tertiary floras
was made by Huzioka (1972). Huzioka described 44 species
and 35 species from the Janggi and Yeonil Groups. Huzi-
oka’s paper included 18 species of Acer (excluding sp.).
Chun et al. (1982) reported 41 genera and 64 species
(including 4 species of Acer) from the Pohang Basin without
their descriptions. Tanai (1983) made a general review on
the 35 species of Acer described by many authors from the
Tertiary strata of East Asia. Tanai's paper contains a useful
list of all species previously described in the Tertiary strata
of Korea. His revision seems to be appropriate and is
accepted in this study.
Ablaev et al. (1993) described 32 genera and 48 species of
plant fossils from the Tertiary strata of the Gogeonwon dis-
trict in the Hamgyeongbug-do. He added 4 species of Acer.
Lim et al. (1994) described many species of fauna and flora
(including 8 species of Acer) from the Tertiary deposits of
North Korea. Table 1 shows the Acer species recorded by
the previously mentioned authors from the Korean Tertiary
As shown in Table 1, 29 species of Acer have been iden-
tified from the Tertiary of Korea. Among them, 20 species
are represented by both foliage and samara, and 9 species
only from their foliage or samara. The Janggi and Yeonil flo-
ras in the Pohang Basin include only 5 species and 3 species
of Acer respectively. They are smaller in number relative to
the same age of Hamjindong flora with 14 species of Acer.
It is thought that the difference of floral composition
between Janggi, Yeonil and Hamjingdong floras is a resulted
of the difference of mean annual temperature due to differ-
ences of latitude.
According to Huzioka (1972), about 140 species of fossil
plants are known from the Miocene floras of Korea. Among
them, Acer occupies about 21% of the Yeonil flora and is the
largest taxa in the species level. It is thought that the pale-
oclimate of middle Miocene in the Korean Peninsula might
be the optimal climate for Acer habitation.
The extant mapple family, Aceraceae includes more than
140 extant species that are mostly distributed in temperate
regions and some tropical mountains (Ogata, 1967; Park,
1986; Talor and Talor, 1993). Therefore there is no doubt
that the Yeonil flora bearing Acer pohangense sp. nov. might
have flourished in a temperate climate.
A new species of Acer pohangense was proposed on the
basis of the detached large-sized samaras of Acer. The
occurrence of such a large-sized samara is the first recorded
not only in the Korean Tertiary flora, but also in the East
Asian Tertiary floras.
ACKNOWLEDGMENTS: The writer thanks to two anonymous
reviewers for their critical reading and valuable comments.
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Manuscript received July 17, 2008
Manuscript accepted November 21, 2008