全 文 ：Received 6 Jun. 2003 Accepted 27 Sept. 2003
Supported by the Projects from The Chinese Academy of Sciences (KSCX2-SW-108), the National Natural Science Foundation of China
(39970056) and the Project of“Forward Research Field”from Institute of Botany, The Chinese Academy of Sciences.
* E-mail: .
http://www.chineseplantscience.com
Acta Botanica Sinica
植 物 学 报 2004, 46 (4): 407-414
Diaphorodendron rhombicum sp. nov., a New Anatomically Preserved
Lepidodendralean Stem from the Taiyuan Formation in
Southern Shandong Province, North China
WANG Shi-Jun*
(Laboratory of Systematic and Evolutionary Botany, Institute of Botany, The Chinese Academy of Sciences, Beijing 100093)
Abstract : In this paper a new species of anatomically-preserved lepidodendralean stem is described from
coal balls in the No.16 coal seam of the Taiyuan Formation in Shanjialin Coal Mine, Tao-Zao Coal Field,
southern Shandong Province. The stem has a well preserved stele, outer cortex, periderm and leaf
cushions preserved. Its organization is protostelic and it lacks secondary xylem. Outer cortex consists of
alternatively arranged radial thick-walled cell bands and damaged thin-walled cell areas. Periderm is well
developed, 4-5 mm wide, and is divided into phellem and phelloderm. Phelloderm is wider than the phellem
and is general ly uniform but in some places is di fferentiated into alternatively arranged zones of
tangentially thicker- and thinner-walled cell bands. Leaf cushions are approximately equidimensional or
rhomboidal in tangential section, whereas leaf scars are slightly elevated and are probably lenticular or
helmet-like in shape, located at the upper part of the leaf cushion. Leaf cushions are flat and lack a well
developed keel or plications. Leaf traces extend through a horizontal course in the cushion and turn
upwards slightly and then horizontally into the leaf scars, resulting in the outermost parts of the course
being somewhat “S” shaped. In radial section ligule pits are obliquely orientated with a broad basic part and
its aperture is directly located at the top of the leaf scar. The ligule is large, ovoid in shape, and
approximately 1.2 mm long and 1.0 mm wide. Compared with the stems of other genera in Lepidodendrales,
the stem under discussion is most comparable to the stems of Diaphorodendron to which it is here
assigned. Each of the three previously known species of Diaphorodendron occur in the middle Late
Carboniferous of the Euramerican Flora and are distinct from the stem under discussion in the form of the
leaf cushions. These differences support the erection of a new species, D. rhombicum, representing the
first discovery of the genus from late Late Carboniferous and Permian ages worldwide, and also representing
the first occurrence of the genus within the Late Palaeozoic Cathaysian Flora. It is very interesting that
the new species bears equidimensional leaf cushions with that probably represents a derived feature within
the genus, while the leaf cushions with greater vertical than horizontal dimension occupied by the Euramerican
species of Diaphorodendron are here considered ancestral in morphology. This hypothesis is supported by
the younger geological age (late Late Carboniferous or early Early Permian) of the new species than that
(middle Late Carboniferous) of the previously known Euramerican species of Diaphorodendron.
Key words: Cathaysian Flora; Taiyuan Formation; coal ball; Lepidodendrales; Diaphorodendron ; new
species
Diaphorodendron (DiMichele) DiMichele et Bateman
was established mainly on anatomical features for a whole
plant species o f Euramerican lepidodendralean plants in-
cluding vegetative and fertile organs. Its stem, when found
as a n is o lat ed mor ph os p ec ie s , a re c al le d as
Diaphorodendron whereas it s male and female cones are
assigned to the morphospecies Achlamydocarpon varius.
The stem is characterized by possessing protostele, outer
cortex composing of weakly to strongly radially alternating
areas of thick- and thin-walled cells, and a bifacial periderm
in which phellem and phelloderm are histologically differ-
entiable (DiMichele and Bateman, 1992). To date, species
of Diaphorodendron have been only found in the middle
Late Carboniferous (Westphalian age) from the Euramerican
Flora. However, in the Cathaysian Flora of northern China,
fossils o f lepidodendralean stems reported so far have
mainly been identified from impression-compression pres-
ervation and there have been a few of examples of reports
on anatomically preserved lepidodendralean stems (Wang,
1983; Guo and Tian, 1994; Tian and Wang, 1995; Wang et
al ., 2002; Chen et a l., 2003). Among these stems on ly
“Lepidodendron” pulchrum is similar to Diaphorodendron
in some aspects, such as in the features of periderm and
outer cortex (Chen et a l ., 2003). However there are

Acta Botanica Sinica 植物学报 Vol.46 No.4 2004408
distinctions between “L.” pulchrum and Diaphorodendron
and this particular species cannot be assigned into the ge-
nus Diaphrodendron. In short, no lepidodendralean stems
or whole plant of Diaphorodendron have been reported
from the Cathaysian Flora to date.
A ne w s p ec ie s o f a na to mica lly p r es er ve d
lepidodendralean stem of Diaphorodendron is reported in
th is pap er. Th is repres e n ts the firs t s p ecies o f
Diaphorodendron to be described from the Cathays ian
Flora and also represents the first occurrence of this genus
outside Euramerican palaeofloristic province.
1 Materials and Methods
The new species is represented by a single specimen
that is preserved in coal ball No. SS-14 from coal seam No.
16 in the Tao-Zao Coal Field of South Shandong Province,
North China. The stem moderately well-preserved apart from
the thin-walled cells in the outer cortex and stele are poorly
preserved. The geological background of the locality was
introduced in detail by Guo et a l. (1990) and Chen et al.
(2003).
The peel method (Phillips et al., 1976; Galtier and Phillips,
1999) was employed in the study of the new species. The
coal balls and peels and slides in this study are housed in
Paleobotanical Collections of Beijing Campus of China Uni-
versity of Mining and Technology and Institute of Botany
of The Chinese Academy of Sciences respectively.
2 Description of the New Species
Order Lepidodendrales
Family Diaphorodendraceae
Genus Diaphorodendron (DiMichele) DiMichele
et Bateman, 1992
Species D. rhombicum sp. nov. (Figs. 1-26)
Diagnosis of the new species:
Haplos tele Inner and middle cortex unknown. Outer
cortex 7-8 mm wide. Dimension of thick-walled cells of
outer cortex increasing from inner side to outer side and the
length changing in a cont rary way. Areas of th in-walled
cells badly preserved. Phelloderm 1.5-4.0 mm wide. Phellem
1-2 mm wide. Leaf cus hion nearly equid imens ional or
squarely rhomboidal in shape with a height : width ratio of
nearly 1:1. Leaf cushion with a distinct slope with weakly
developed plicates on it above and behind the leaf scar and
with a sligh tly contracted bottom s ide somet imes with
weakly developed plicates on it. Leaf scar located on the
upper part of the leaf cushion with a probable lenticular or
helmet-like shape and slightly elevated. Several layers o f
cells with s mall s ize and thick wall, us ually in poor
preservative condition , beneath the epidermis. Leaf trace
in a nearly horizontal course with its outermost part slightly
bending upwards and ou twards o r in a somewhat “S”
shape. Parichnos s trand b ifurcat ing at the bas e of ligule
pit. Few t ransfusion cells between the ligule pit and leaf
trace. Ligule pit with a broad basic part and obliquely orien-
tated and with its aperture located directly at the top angle
of the leaf scar. Ligule ovate and large with its long axis up
to 1.2 mm and short axis up to 1 mm in radial section.
Holotype: Coal Ball: SS-14 and voucher peels and slides.
Etymology: Species epithet is derived from the rhomboi-
dal surface view of the leaf cushion of the new species.
Stratigraphy and local ity: No .16 Coal Seam, Taiyuan
Formation; Tao-Zao Coal Field, Shandong Province.
2.1 Stele
The stem is flattened probably because of the pressure
of the overlying geological formations, and has a long axis
length of 60 mm and a short axis length of 25 mm in diameter
when viewed in cross section (Fig.1).
The cells of the stele are inconspicuous because of ad-
vanced pyrite growth destroying the plant tissues. Despite
the poor preservation it is clear that the stem possesses a
haplostele that lacks secondary xylem (Fig.17). The primary
xylem is exarch with a smooth outer margin. The tracheids
of protoxylem do not form distinct corona or pole. Trache-
ids in the central part of the stele are loosely arranged. The
tracheids of the metaxylem are nearly isodiametric with a
diameter from 70-100 mm at the outer margin to 200-250
mm in the central part in cross section and possess scalari-
form thickenings and Williamson’s striations on the wall in
longitudinal section (Fig.22).
2.2 Cortex
Only the ou ter cortex is p reserved. It is 7-8 mm wide
and consists of radial thick-walled cell bands and poorly
preserved thin-walled cell areas. In cross section the thick-
walled cells are nearly isodiametric with increasing size cen-
tripetally from 50-70 mm at the outer side to 100-120 mm at
the inner s ide (Fig .4). In long itud inal section the thick-
walled cells are slightly vertically elongate and the length
increases centrifugally from 80-160 mm at the inner side to
120-250 mm at the outer side (Fig.24). The shape and size
of the thin-walled cells are unknown due to preservational
limitations.
2.3 Periderm
Periderm can be divided into two distinct parts (Fig.3).
The outer zone is typically with lighter color and is phellem,
varying from 1-2 mm wide and consisting of uniform cells.
The cells are nearly rectangular with smaller radial diameter
than the tangen tial one in cross section. In radial section,
Acta Botanica Sinica 植物学报 Vol.46 No.4 2004410
the cells are vertically elongate with tapered or rounded
ends (Fig.23). None of the cells observed contain any secre-
to ry con ten ts. The inner zone is darker in colo r and is
phelloderm, varying from 1.5-4.0 mm wide and consisting
of cells o f nearly square to rectangular with greater radial
diameter than the tangential one in shape and arranged in
radial rows in cross section. In some places the phelloderm
consists of the alternately arranged tangential thin-walled
cell bands and thick-walled cell bands. The thin -walled
bands are often poorly preserved and form tangential waved
cracks (Fig.3). In radial section, the cells of phelloderm are
vertically elongate with rounded ends (Fig.25). No secre-
tory content is present in the cells.
2.4 Leaf cushion
2.4.1 Morphology Leaf cus hions are arranged spirally
and con tiguously on the s tem (Fig.21). They are nearly
fusiform in shape in tangential section through its inner-
most part with a heigh t of 6-7 mm and a width of 4.5 mm
(Figs.16, 26). The width slightly increases outwards and is
about 6 mm at the one-half of the th ickness of the leaf
cushion (Figs.14, 15, 26). At the surface of the leaf cushion
it has an outline of squarely rhomboidal with both its width
and height being about 5 mm (Figs.13, 26). The surface of
the leaf cush ion is flat with the leaf scar located at the
upper one-third part of the leaf cushion (Fig.26). Leaf scar
is len ticular or helmet-like in shape and slightly elevated,
about 4-5 mm wide and 2.0-2.5 mm high (Figs.12, 20, 26).
There is a distinct slope with weakly developed plicates on
it above the leaf scar. The bottom side of the leaf cushion is
nearly perpendicular to the surface of the stem (Figs.9, 10,
26).
2.4.2 Anatomy There are several layers of small and thick
walled cells beneath the epidermis. They are nearly isodia-
metric or s lightly radially elongate in shape in cross and
longitudinal sections, although they are often poorly pre-
served (Figs.2, 9, 10, 14). Inside of these cells are large and
thin-walled parenchyma cells and they are usually isodia-
metric and polygonal in shape except for those around the
ligule pit that are smaller and isodiametric in cross and tan-
gential sections (Figs.18, 19) but radially elongate in radial
section (Fig.11). Few of transfusion cells with thickenings
on the wall have been observed in the region between the
base of the ligule pit and leaf trace.
Leaf trace enters the middle part of the leaf cushion from
the periderm and extend outwards at a nearly horizon tal
course. When it arrives at the base of the ligule pit it bends
upwards and then turns outwards and enters into the leaf
scar, so the outermost part of the leaf trace is in a “S” shape
(Figs.9, 11, 26). In tangential section the leaf trace is nearly
semi-circu lar in shape with a flat upper side and a convex
lower side (Fig.18). The bundle sheath consists of 2-3 lay-
ers of cells that are tangentially elongate except for those
located at the upper side that are larger and nearly round.
The xylem strand is somewhat horizontally elongated and
is in most instances poorly p reserved. Below the xy lem
strand is a wide “V”-shaped sclerenchyma strand.
Parichnos enters the leaf cushion as a single strand from
the periderm and is accompanying with the leaf trace by
just beneath it before it bifurcates at the base of the ligule
pit (Figs.18, 19). W hen the branch parichnos strands ex-
tend continuously outwards, they tend to be isodiametric
in shape and smaller in size. It can be deduced that in the
leaf scar two branch parichnos strands flank the leaf trace
are located at the same horizontal line. However the exact
size and s hape of parichnos and leaf trace in the leaf scar
are unknown because of preservational limitations within
the leaf scar (Fig.20).
The ligule pit is located in the outer one-half of the ra-
dial thickness of the leaf cushion with a broad basic part
and is obliquely orientated with its apertu re probably lo-
cated at the top angle of the leaf scar (Figs.11, 26). In radial
section, the ligule is ovate and obliquely orientated or at a
slight angle with the horizontal line. It has a long axis of up
to 1.2 mm and a short axis o f up to 1 mm and consists of
very small and isodiametric cells with dark brown color (Fig.
11). In tangential section through the outer part of the ligule
pit there is a very narrow or crack-like opening extending
from the top of the ligule pit to the small thick-walled cell
layers beneath the epidermis (Figs.14, 15, 18).
3 Comparison and Discussion
3.1 Comparison
The present specimen complies with the those of the
genus Diaphorodendron in the features of the stele, outer
cortex and periderm. The stele of the present specimen is
obviously protostelic, although it is unknown if it is mixed
protostelic such as that in Diaphorodendron. Differences
between the present specimen and Diaphorodendron
mainly exist in the form of the leaf cushion. The leaf cush-
ion of the present specimen is squarely rhomboidal or with
a height-width ratio of nearly 1:1 in tangential section, while
in Diaphorodendron the leaf cushions are vertically elon-
gate or with a heigh t-width ratio o f 2:1 to 4:1. The shape
and orientation of ligule pit and ligule are also very distinct
in the present specimen and Diaphorodendron (Table 1).
The leaf cushion of Synchysiodendron is similar to that
of the present specimen in the obliquely orientated ligule
pit with its aperture close to the top angle of leaf scar and

Acta Botanica Sinica 植物学报 Vol.46 No.4 2004412
has a somewhat broad basic part. However, the ligule is not
so broad as that of the present specimen and is elongate,
club-shaped (DiMichele, 1979b). Synchysiodendron pos-
s ess es a s iphonos tele, an ou ter cortex largely o f
homogeneous, elongate, thick-walled parenchyma cells,
which are very distinct from the present specimen.
The present specimen is very different from the stems
of other genera of Lepidodendrales, such as Lepidodendron
Sternberg s ens u DiMichele, Lepidophloios Sternberg
(DiMichele, 1979a), Sigillaria Brongniart (Delevoryas, 1957;
Chaloner, 1967), Paralycopodites (Morey and Morey)
DiMichele (1980) and Hizemodendron Bateman et
DiMichele (1991). These distinctions are great enough such
that comparison of thes e genera with the specimen de-
scribed in this paper is not needed.
From the information above, the present specimen com-
pares well in several aspects with Diaphorodendron
DiMichele, a genus s egregated from Lepidodendron
Sternberg, although there are some differences in the shape
and orientation of the ligule pit and ligule in leaf cushions.
As the branching characteristics of the present specimen
is unknown it is d ifficult to compare it with specimens of
Diaphorodendron in which the branching of the stem is
well known (DiMichele, 1981; DiMichele and Bateman, 1992).
As s uch , the p resen t specimen has been as signed to
Diaphorodendron until such time that further research on
more specimens , especially lateral b ranch systems , is
conducted. This information will then permit an ass ess-
ment of the affinity of the stems, although it is possible that
these unknown characters of the stem are the same as those
of Diaphoroendron from Euramerica.
There are three species in the genus Diaphorodendron
Table 1 Comparison of Diaphorodendron rhombicum sp. nov. with other species of Diaphorodendron from the Euramerican Flora
D. rhombicum sp. nov.
D. vasculare D. scleroticum D. phillipsii
(DiMichele, 1981) (DiMichele, 1981) (DiMichele, 1981)
Morphology of leaf cushion
Outline of leaf cushion Squarely rhomboid Vertically elongate Vertically elongate Vertically elongate
Height-width ratios Nearly 1:1 2:1-4:1 1.8:1-3:1 1.8:1-2:1
Anatomy of leaf cushion
Ligule pit Broad and oblique with its Narrow and vertical with Narrow and vertical Narrow and vertical with its
aperture close to the top its aperture slightly away with its aperture slightly aperture slightly away from
angle of leaf scar from the top angle of the away from the top the top angle of the leaf
leaf scar angle of the leaf scar scar
Ligule Obliquely and broadly Vertically elongate ovoid, Vertically elongate ovoid, Vertically elongate ovoid,
ovoid, 1 200 mm long and 300-500 mm long and less up to 600 mm long and 300-500 mm long and less
800-1 000 mm wide than 300 mm in radial less than 200 mm in than 300 mm in radial
diameter radial diameter diameter
Thickness of leaf cushion > 3 mm Usually < 2 mm Usually 2 mm , up to Usually 2 mm
4.1 mm in large leaf
cushions
Anatomy of stem
Outer cortex No sclerotic or secretory- Sclerotic or secretory-like Sclerotic or secretory-like A ring of cavities present
like cells present at the cells usually present at the cells usually present at at the outer edge of the
inner edge and no cavities inner edge of the outer the inner edge of the outer cortex
present at the outer edge cortex outer cortex
of the outer cortex
Fig.26. Line drawings of the leaf cushion. A. Surface view. The
outer black line represents the outline of the cushion through the
one half of the radial thickness and the inner one rep resents the
outline of the surface view. The dotted line represents the outline
of the cushion through its innermost part. B. Radial section, show-
ing the shape of ligule pit and ligule and the extending course of
leaf trace and parichnos. C. Cross section, showing the smaller
dimension of the leaf cushion at its innermost part.
WANG Shi-Jun: Diaphorodendron rhombicum sp. nov., a New Anatomically Preserved Lepidodendralean Stem from the
Taiyuan Formation in Southern Shandong Province, North China 413
distributed within the Euramerican Flora. They are different
from the present specimen in several aspects (Table 1), sug-
gesting the present specimen represents a new species of
the genus.
3.2 Discussion
Before the 1980s the lepidodendralean stems in impres-
sion-compression preservative condition were mainly as-
signed into Lepidodendron Sternberg and on ly a few of
them were pu t in to s everal o ther genera, s uch as
Lepidophloios, Sigi llaria, Bothrodendron Lindley et
Hutton, Ulodendron Lindley et Hutton, Asolans Wood and
Cathaysiodendron Lee (Shen, 1995). More than 80 species
of the genus Lepidodendron Sternberg in the Cathaysian
Flora have been described, including many different kinds
of leaf cushion of which some probably belong to genera
other than Lepidodendron. Recently several anatomical
species of lepidodendralean stems were described from the
Cathaysian Flora of China, including Sigillaria cf. brardii
(Guo and Tian, 1994) and “Lepidodendron” lepidophloides
Yao (Wang et a l., 2002) from the Late Permian in Guizhou
Province, s ou thwes tern China; “Lepidodendron”
pulchrum Zhang (Chen et al., 2003), “L.” tachingshanense
Lee and “L.” posthumii Stockmans et Mathieu (Tian and
Wang, 1995) from the late Late Carboniferous or early Early
Permian in Shandong Prov ince, North China. In these
species, “L.” pulchrum is comparable to Diaphorodendron
in outer cortex and periderm, however, they are quite differ-
ent in stele and leaf cus hions. “L.” tachingshanense and
“L.” posthumii, like the new s pecies , are very close to
Diaphorodendron in stele, outer cortex and periderm, how-
ever their leaf cush ions d iffer s ign ifican tly from
Diaphorodendron in morpho logy (mainly in the shape of
the leaf scar) and anatomy. So D. rhombicum is the first
species of the genus described from the Cathaysian Flora
up to now.
It is very interesting that the leaf cushion of the new
species is nearly equidimensional or with nearly equal ver-
tical and horizon tal dimension , while those of the other
three species of Diaphorodendron from the Euramerican
Flora are vertically elongate or with greater vertical than
horizontal dimension when measured tangentially . In
Lepidodendron Sternbe rg s ens u DiMic hele and
Synchysiodendron, the leaf cushions on large stems are
vertically elongate, while those on the small lateral branches
can be nearly equidimensional (DiMichele, 1979; 1983). The
present specimen, although not large and without second-
ary xylem, is not a small branch because it has quite thick
periderm, up to 4-5 mm in thickness. It is possible that the
equidimensional leaf cush ions of the new species are
derived from the vertically elongate ones of the species in
the Euramerican Flora, because the geological age o f the
new species is Stephanian Stage of the late Late Carbonif-
erous or Asselian Stage of the early Early Permian and is
younger than the latter (Westphalian Stage of the middle
Late Carbon iferous ). It is pos sib le that species o f
Diaphorodendron with the vertically elongate leaf cush-
ions can be found from the middle Upper Carboniferous
(such as Penchi (=Benxi) Formation and the Yanghukou
Formation) in China.
Acknowledgements: The author is grateful to Dr Jason
Hilton o f Univers ity o f Birmingham for ed iting the
manuscript. Prof. TIAN Bao-Lin and CHEN Gui-Ren of China
University of Mining and Technology in Beijing for pro-
v iding the materials o f th is res earch and valuab le
suggestion.
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