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j.geobios.2018.08.004

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Accepted Manuscript
Title: Belowground rhizomes and roots in waterlogged
paleosols: Examples from the Middle Jurassic of Beijing,
China
Author: Lu Liu Min Qin Ning Tian Changfu Zhou Deming
Wang James F. Basinger Jinzhuang Xue
PII:
DOI:
Reference:
S0016-6995(17)30186-9
https://doi.org/doi:10.1016/j.geobios.2018.08.004
GEOBIO 837
To appear in:
Geobios
Received date:
Accepted date:
25-12-2017
3-8-2018
Please cite this article as: Liu, L., Qin, M., Tian, N., Zhou, C., Wang,
D., Basinger, J.F., Xue, J.,Belowground rhizomes and roots in waterlogged
paleosols: Examples from the Middle Jurassic of Beijing, China, Geobios (2018),
https://doi.org/10.1016/j.geobios.2018.08.004
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Belowground rhizomes and roots in waterlogged paleosols: Examples from the Middle Jurassic of Beijing,
China ?
Lu Liu a, Min Qin a, Ning Tian b, Changfu Zhou c, Deming Wang a, James F. Basinger d,e,
Jinzhuang Xue a,*
a
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Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences,
Peking University, Beijing 100871, PR China
College of Palaeontology, Shenyang Normal University, Shenyang 110034, PR China
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College of Earth Science and Engineering, Shandong University of Science and Technology,
Qingdao, Shandong 266590, PR China
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Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan,
S7N 5E2, Canada
an
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School of Biological Sciences, Victoria University of Wellington, Kelburn, Wellington 6012,
New Zealand
Corresponding editor: Evelyn Kustatscher.
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* Corresponding author. E-mail address: pkuxue@pku.edu.cn (J. Xue).
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Abstract
Plant rhizomes and roots occur in terrestrial ecosystems since at least the Devonian, but the
documentation of belowground plant tissues is sparse in the fossil record. In this study,
fossils representing belowground rhizomes and roots are described from the top of the
Upper Yaopo Formation (Middle Jurassic), at the Yuejiapo section, Mentougou District,
Beijing, China. Morphological studies of the plant fossils, together with lithofacies analyses,
provide new information on plant-soil interactions during the Jurassic period. Three types of
rooting systems are recognized from two fossiliferous beds. The Bed-1 Flora is interpreted as
representing a Cladophlebis-dominated community, where abundant foliage remains mainly
of Cladophlebis cf. scariosa and Cladophlebis delicatula are associated with Type-A rooting
system. The Bed-2 Flora includes Type-B and Type-C rooting systems, although the floristic
composition is unknown due to the absence of identifiable foliage remains. The Type-A and
Type-B rooting systems consist of abundant in situ vertical rhizomes, fine shoot-borne roots
and lateral roots, and are consistent with those of some extant ferns. The Type-C rooting
system shows a thick central taproot and at least three orders of lateral roots, an
architecture typical of various gymnosperms. The in situ rooting systems, as well as
sedimentary evidence, contribute to the recognition of stacked, reworked Entisols in a
dynamic waterlogged environment.
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Keywords:
Cladophlebis
Fern
Plant fossil
Rooting system
Lithofacies
Paleosol
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1. Introduction
Information from both aboveground and belowground plant tissues is essential for
understanding the roles that plants have played in terrestrial ecosystems since their
colonization on land (Raven and Edwards, 2001; Taylor et al., 2009; Kenrick and
Strullu-Derrien, 2014). Belowground rhizomes and roots directly mediate the interactions
between plants and soils and thus can provide a window onto ecological processes
(McCormack et al., 2017). Rhizomes and roots of extant plants have been subject to much
attention concerning their morphology, structure, development, genetics, interactions with
soils, fungal and bacterial symbioses, biomass allocation, etc. (Bellini et al., 2014;
McCormack et al., 2017). Nevertheless, the deep-time fossil record of belowground
structures is sparse in comparison to the extensive documentation of aboveground tissues
(Raven and Edwards, 2001; Taylor et al., 2009; Kenrick and Strullu-Derrien, 2014). Since the
early colonization of land in the Devonian, plant belowground structures have undergone
significant evolutionary adaptations (Raven and Edwards, 2001; Hetherington and Dolan,
2016). As an example, permineralized plants of the Early Devonian Rhynie Chert show early
symbiotic associations of fungi in rhizoid-bearing rhizomatous axes (Taylor et al., 2009;
Kenrick and Strullu-Derrien, 2014), and Early Devonian fossils from South China reveal that
belowground rhizomes of even very primitive vascular plants functioned in reducing soil
erosion and increasing the resilience of plant communities (Xue et al., 2016).
The Jurassic period was an important interval in the evolution of plants, when plant
communities were characterized by diverse ferns, sphenopsids, seed ferns, cycads, ginkgos
and conifers. So far, the interpretation of plant communities and their function in Jurassic
landscapes have been based largely on the description of aboveground tissues (mainly of
leaves), with limited record of belowground structures mainly pertaining to the rhizomes of
some ferns, such as the permineralized rhizomes of osmundaceous ferns (Zhou, 1995; Tian
et al., 2008, 2014; Yang et al., 2010; Bomfleur et al., 2014, 2015).
Deeper understanding of the evolution of plant rooting systems and plant-soil interactions
demands better fossil evidence, particularly from localities with in situ preserved plant
fossils, i.e., in paleosols. In this study, we report on two beds of plant fossils from the Jurassic
paleosols of western Beijing, China. Morphological studies of the fossil plants, together with
lithofacies analyses of the fossil-bearing rocks, provide new information on the fossil record
of belowground structures and plant-soil interactions during the Jurassic.
2. Geological setting and stratigraphy
Plant fossils are abundant in the Mentougou Group, which is well exposed in western Beijing,
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China, and was initially called the Mentougou Coal Series and later sub-divided into the
Lower Yaopo, Upper Yaopo, and Longmen formations, in ascending order (Chen et al., 1984).
The thickness of the Mentougou Group varies laterally, but can reach up to 1200 m where
the sequence is complete (Chen et al., 1984). The Lower Yaopo Fm. is composed of
conglomeratic quartz sandstone, siltstone and mudstone, and includes several coal seams.
The lower part of the Upper Yaopo Fm. is composed of sandstone with siltstone, and the
upper part consists of siltstone and mudstone interbedded with sandstone and rich in
siderite nodules. The Longmen Fm. is characterized by a basal conglomerate overlain by
sandstone and siltstone, with conglomerate in places. The Mentougou Group has been
interpreted as a sequence of fluvial and lacustrine deposits (Chen et al., 1984; Wang et al.,
2010).
Plant fossils from the Mentougou Group were first reported by Newberry (1866), with
comprehensive studies by Chen et al. (1984; recognizing 73, 41, and 27 plant species from
the Lower Yaopo, Upper Yaopo, and Longmen formations, respectively) and Duan (1987;
recognizing 44 species in 28 genera from equivalent strata at neighboring Zhaitang region,
Mentougou). Previous work has focused on the taxonomic description of plant fossils, with
discussion of their biostratigraphic and paleoclimatological implications. The whole flora is
represented by horsetails, ferns, cycads, czekanowskialeans, ginkgos and conifers; it
generally indicates a warm-humid, subtropical climate (Chen et al., 1984).
The geologic age of the Mentougou Group has been tentatively determined based on
megafossil plants and regional stratigraphic correlation. Chen et al. (1984) suggested a late
Early Jurassic age for the Lower Yaopo Fm., and a Middle Jurassic age for the Upper Yaopo
and Longmen formations. Duan (1987) considered that both the Lower Yaopo and Upper
Yaopo formations are Middle Jurassic in age. Based on the occurrence of Coniopteris
Brongniart and Eboracia Thomas in the Lower Yaopo Fm., as well as the similarities of
floristic components between the Lower and Upper Yaopo formations, Zhou (1995)
suggested that both formations are early Middle Jurassic (probably Aalenian-Bojocian) in age,
a scheme followed in the present work.
3. Material, methods and terminological notes
The studied material was collected from the uppermost part of the Upper Yaopo Fm. at the
Yuejiapo section, located near Yuejiapo Village, Mentougou District, Beijing City (Fig. 1;
39�?24??N, 116�15??E). Chen et al. (1984) presented a logged lithological column of the
Mentougou Group near Yuejiapo Village (Fig. 2(A)), left column), but the exact location of
their section is now difficult to identify. Our fossils are from two beds from a new locality:
Bed-1 (Bed-1 Flora) is 2.6 m thick and composed of yellow-green muddy siltstone; Bed-2
(Bed-2 Flora), 1.1 m thick and also composed of siltstone, is ca. 23.9 m above Bed-1 and ca.
6.4 m below the basal conglomerate of the Longmen Fm. (Fig. 2(A-right column, B-E)).
Plant fossils, including numerous leaves (138 specimens from Bed-1), and rhizomes and roots
(84 specimens from Bed-1 and Bed-2), are preserved as compressions, lacking internal
anatomy. Leaf fossils mainly occur on horizontal sedimentary planes within lithofacies Fpd,
while most rhizomes and roots are vertically extended in rock matrix of lithofacies Fr (for
facies characteristics, see Section 4.3). The fossils were prepared with steel needles and
photographed with a digital camera system. Specimen measurements were taken using the
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free ImageJ 1.44 software (http://rsb.info.nih.gov/ij/index.html). For lithofacies analysis,
outcrops and sequences were observed for primary sedimentary structures, bed thicknesses,
grading, contacts, and repetitive cycles. Hand specimens were collected for thin-section
petrological analysis. All specimens prefixed by PKUB and slides prefixed by 1607JX are
housed at the School of Earth and Space Sciences, Peking University, Beijing.
Terminology for rhizomes, shoot-borne roots, and lateral roots is according to Groff and
Kaplan (1988) (Fig. 3(A, B)). Similarly, as per Bell and Tomlinson (1980), for the term
?rhizome? we mean a modified stem produced by axis elongation and branching, usually
found within the substrate. The term adventitious root is commonly used in the literature for
those roots borne on rhizomes or shoots; however, Groff and Kaplan (1988) recommended
that the term ?shoot-borne roots? be used instead, to better represent the predictable
pattern in which fern roots arise from shoots. A taproot system usually consists of a main,
central root and a few smaller first-order lateral roots, which further produce higher-order
lateral roots (Bellini et al., 2014; Fig. 3(C)). Branching density and angle are two aspects for
describing the architecture of rooting systems. Branching density is defined as the ?number
of lateral roots per unit length, e.g. cm?; those roots that are less than 2 mm in diameter are
called fine roots, and those larger than 2 mm in diameter, coarse roots (McCormack et al.,
2017).
It is quite difficult to recognize rhizome-root and taproot systems, and sometimes, to
distinguish rhizomes and roots from axes, based on compression fossils only. However, most
traits related to root morphology and modern plant architecture, such as root length, root
diameter, branching ratio, branching intensity, branching angles, etc. (summarized by
McCormack et al., 2017), are available and measureable for compression fossil rhizomes and
roots. Thus based on well-studied root morphology models (e.g., Fig. 3), it should be
possible to explore the value of morphological characters from the fossil record.
4. Results
4.1. Aboveground plant fossils of Bed-1 Flora
Fronds and leaves are generally fragmentary; nevertheless, six species can be recognized
based on 138 specimens, including: Cladophlebis cf. scariosa Harris (Fig. 4(A-C)),
Cladophlebis delicatula Yabe et 詉shi (Fig. 4(D, E)), Cladophlebis argutula (Heer) Fontaine
(Fig. 4(F)), Coniopteris hymenophylloides (Brongniart) Seward, Pityophyllum longifolium
(Nathorst) Moeller, and Elatocladus manchurica (Yokoyama) Yabe. Specimens assigned to the
genus Cladophlebis Brongniart dominate (particularly C. cf. scariosa and C. delicatula),
reaching 87% of the total collection (Fig. 5); the community is interpreted as
Cladophlebis-dominated.
Species of Cladophlebis are characterized by bipinnate fronds, subopposite pinnae and a vein
pattern typically with a midvein and dichotomous lateral veins, although they show great
interspecific variation (Fig. 4). In our collection, Cladophlebis cf. scariosa bears a bipinnate
frond at least 100 mm long; the ultimate pinnae are ca. 62 mm long and closely spaced; the
pinnules are slightly falcate, more than 12 mm long, with an entire margin; the midvein
departs at an angle of ca. 80� from the slender pinna-rachis (Fig. 4(A)); and the lateral veins
dichotomously divide twice. Ultimate pinnae of Cladophlebis delicatula are very slender,
more than 70 mm long, linear-lanceolate in outline, tapering gradually from the base upward
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to an acuminate apex (Fig. 4(D)); the pinnules are straight or slightly falcate, ca. 20 mm long
and ca. 4 mm wide at the base, with an entire or slightly undulate (flexuous) margin, and are
alternately arranged; the midvein is straight or flexuous; and the lateral veins depart from
the midvein at an angle of ca. 30�, forking once. Cladophlebis argutula is rare in our
collection (only 2 specimens), with linear, alternate, ultimate pinnae; the pinnules are small,
ligulate, 8-16 mm long and 5 mm wide; the margin is entire or slightly wavy; the base is
broad and fused with adjacent pinnules; the midvein is thin and decurrent, straight or
flexuous; and the lateral veins dichotomize twice.
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4.2. Belowground plant fossils of Bed-1 Flora (Type-A rooting system)
Bed-1 contains abundant vertical, axis-like fossils (Figs. 6, 7) which are interpreted as in situ
plant rhizomes. We infer that these rhizomes, here called ?Type-A rooting system?, were
produced by the Cladophlebis species, because of the close association between these
rooting systems and fronds, and the dominance of Cladophlebis in Bed-1. It is acknowledged
that there are at least three Cladophlebis species in Bed-1, and therefore it is difficult to
determine whether only one species is represented, or different species of Cladophlebis bore
indistinguishable rooting systems.
Rhizomes are 2.0-5.7 mm wide (average = 3.3 mm; standard deviation [SD] = 0.9 mm; n =
113), and 6.4-68 mm long (average = 27 mm; SD = 13.9 mm; n = 113), although the
measured length must be considered incomplete. Rhizomes commonly branch
dichotomously (Figs. 6(A, B), 7(C, E, G)). While both downward and upward branchings can
be seen (Fig. 7(F)), the former are most frequent (Fig. 7(C, G)). Rhizomes may be straight, or
may show a twisted morphology (Figs. 6(C), 7(A)) probably due to distortion during sediment
compaction (Fig. 7(D, E)). Rhizomes are densely arranged, with ca. 12 rhizomes along a
10 cm transect perpendicular to the trend of the rhizomes. In some specimens, vertical
rhizomes extend to a horizontal sedimentary plane where pinnae assignable to Cladophlebis
cf. scariosa occur (Fig. 7(D)), but we did not find evidence for the direct, organic connection
between rhizome and frond.
Dense, fine shoot-borne roots are attached to rhizomes (Fig. 7(A, D, E), white arrows); they
are 1.7-25 mm long (average = 9.9 mm; SD = 5.4 mm; n = 84) and 0.3-2.0 mm wide
(average = 1.1 mm; SD = 0.5 mm; n = 84), markedly narrower than rhizomes (Fig. 8). Lateral
roots borne on these shoot-borne roots cannot be observed in hand specimens, but some
thin-sections show thin, branched coalified structures just less than 0.2 mm wide that
probably represent the remains of lateral roots (Fig. 9(D-F)).
4.3. Lithofacies associated with Bed-1 Flora
An integration of sedimentary structures such as texture, bedding surface morphology, and
plant fossil content permits division of Bed-1 into three distinct lithofacies: fines (siltstone
and mudstone) with abundant plant debris, here abbreviated as Fpd; fines with in situ
rooting systems (rhizomes and roots), Fr; and fines with no or few plant fossils, Fnp. The
2.6 m-thick Bed-1 is composed of the sedimentary aggradation of these three lithofacies
(Figs. 6(A, B), 10(A-C)), which we consider as the recording of three different stages
associated with the development of Bed-1 Flora.
Facies characteristics: Lithofacies Fpd is composed of yellow-green thin-bedded muddy
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siltstone, with abundant plant debris (including foliage assigned to species of Cladophlebis).
The units are 10-80 mm thick; they have undulating lower and upper surfaces, and show a
gradational or sharp base (Fig. 10(A, B)). The organic matter is mainly comprised of small
plant fragments shown as thin, compressed coalified material in profile, while large debris is
rare (Fig. 10(A), black arrow). Occurrence of irregularly shaped mineral infillings may have
resulted from decay of original plant tissues and mineral replacement. Vertical infillings in
places indicate the position of plant rhizomes (Fig. 10(A), white arrows). The thick Fpd units
may be composed of a random mixture of plant debris and sediments (Fig. 10(A)), while
other units show rhythmic alternation of plant fossils and sediment (Figs. 9(B), 10(B)). In the
latter case, coalified plant debris forms thin, wavy laminae separated by thicker layers of
detrital sediment (Figs. 9(A-C), 10(B)).
Lithofacies Fr is composed of grey-green muddy siltstone, and bears densely arranged
vertical rhizomes (Figs. 9(D-F), 10(C)). Fr units are ca. 8-110 mm in thickness and have a
gradational contact with lithofacies Fpd (Figs. 6(A, B), 10(C)). Vertical rhizomes are preserved
as two-dimensional compressions, and thus show thin coalified vestiges in profile and cross
sections (Fig. 10(D)). Some rhizomes penetrate from facies Fr into overlying facies Fpd.
Bioturbation can also be observed in facies Fr (Fig. 9(G)).
Lithofacies Fnp is composed of grey siltstone, with no or little plant debris; the units typically
show a more massive appearance (Figs. 9(H), 10(A)). Facies Fnp is overlain by facies Fpd on
an erosional base (Fig. 10(A)), or overlain by facies Fr with a gradational contact (Fig. 10(C)).
Facies association: Facies stack to form sedimentary cycles, and the most common type is
alternation of facies Fr and Fpd (Fr-Fpd couplet; Fig. 6(A, B)), where root fossils mainly occur
in Fr and foliage remains occur in Fpd. One other pattern includes a succession made of
Fr-Fpd-Fnp-Fr-Fpd, in ascending order (Fig. 10(C)).
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4.4. Belowground plant fossils of Bed-2 Flora (Type-B and Type-C rooting systems)
Bed-2 yields an abundance of belowground fossils (Fig. 11). Similar to Bed-1, facies Fpd
(fines with broken plant debris; Fig. 2(C)) and facies Fr (fines with abundant vertical rhizomes;
Fig. 2(D)) are common. Fossils of rhizomes and shoot-borne roots of an unknown plant are
defined as the Type-B rooting system (Fig. 11(A-G)). Rhizomes of Type-B similarly occur in
dense vertical arrangement, and are 11-74 mm long (average = 37.4 mm; SD = 20.5 mm; n =
12) and 1.3-6.8 mm wide (average = 3 mm; SD = 1.9 mm; n = 12), branching dichotomously.
Fine shoot-borne roots are 0.2-1.7 mm wide (average = 0.7 mm; SD = 0.4 mm; n = 55) and
1.0-22 mm long (average = 5.8 mm; SD = 4.3 mm; n = 55). Thin lateral roots average 0.2 mm
wide (range = 0.1-0.5 mm; SD = 0.1 mm; n = 12) and 1.2 mm long (range = 0.6-1.9 mm; SD =
0.4 mm; n = 12).
In Bed-2, the Type-C rooting system is represented by one specimen of a taproot system
comprising a main root and lateral smaller roots (Fig. 11(H-J)). The main root is ca. 64 mm
long and ca. 30 mm wide at the base. There are at least 9 first-order lateral roots 2.0-4.2 mm
wide (average = 2.7 mm; SD = 0.7 mm; n = 9) (Fig. 11(H, J), arrows 1-9). Second-order lateral
roots, 0.2-1.6 mm wide (average = 0.9 mm; SD = 0.4 mm; n = 10), depart from first-order
roots at an angle of ca. 53�. Third-order lateral roots, ca. 0.5 mm wide, are also present. One
of the lateral rooting systems, consisting of a first-order root and higher-order laterals,
reaches 63 mm in overall length.
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5. Discussion
5.1. Morphological comparisons with other plants
Three types of rooting systems are found in Bed-1 and Bed-2. Type-A in Bed-1 and Type-B in
Bed-2 are interpreted as representing plant rhizomes and roots. The Type-A rooting system is
interpreted as probably produced by Cladophlebis species. Considering that Type-B rooting
system is similar in architecture and dimensions to Type-A (Table 1), we interpret this also as
being produced by ferns. The Type-C rooting system, found only in Bed-2, represents a
taproot system with a thick main root and lateral smaller roots (Table 1).
The Type-A and Type-B rooting systems are most closely comparable to the rhizome-root
systems of many extant ferns (Fig. 12). In extant plants, shoot-borne roots may develop from
different positions on subterranean rhizomes, stolons, or aerial shoots in contact with the
ground, and their development in the substrate is strongly influenced by environmental
factors (Cannon, 1949). As examples, the specimen of the extant gleicheniaceous fern
Dicranopteris dichotoma (Thunb.) Bernh. shown in Fig. 12(A) bears a rhizome ca. 2.7 mm
wide, with shoot-borne roots 0.4-1.5 mm wide (average = 0.8 mm; n = 20) and lateral roots
less than 0.3 mm wide; the specimen of Gleichenia squamosissima (Copel.) Nakai shown in
Fig. 12(C) has a rhizome 2.2-2.5 mm wide (average = 2.35 mm; n = 2), with shoot-borne roots
0.4-0.6 mm wide (average = 0.5 mm; n = 12). Both are similar in architecture and dimensions
to those of Type-A and Type-B rooting systems (Table 1). Nevertheless, in the fossil material
rhizomes are numerous, crowded and vertically arranged, while in extant ferns rhizomes are
typically horizontal and sparse, and shoot-borne roots numerous (Figs. 3(A), 12).
Rhizome-root systems similar to those of Type-A and Type-B are not uncommon in extinct
fern-like plants or ferns. Early occurrences of shoot-borne roots have been demonstrated in
the Late Devonian fern-like plants Melvillipteris quadriseriata Xue et Basinger and
Shougangia bella Wang et al., which bear adventitious roots generally less than 1.0 mm in
width along one side of the main axes, though they appear not to have borne lateral roots
(Wang et al., 2015; Xue and Basinger, 2016). For the Late Jurassic Regnellites Yamada et Kato,
a member of the Marsileaceae, the long, creeping rhizomes are 2.0-3.0 mm thick and bear
numerous, ca. 0.2 mm wide shoot-borne roots (Yamada and Kato, 2002), similar in
dimensions to the present material. Other fossil ferns showing structurally preserved
rhizomes include a Hymenophyllaceae fern from the Jurassic (Schneider, 2000), and
Coniopteris concinna (Heer) Chen, Li et Ren, Acanthopteris gothanii Sze, Eogonocormus
cretaceous Deng, and Boodlepteris turoniana Gandolfo from the Cretaceous (Gandolfo et al.,
1997; Deng, 2002). Nevertheless, in all cases of in situ preservation of fossil ferns, we are
unaware of a record of densely arranged vertical rhizomes comparable to those of Type-A
and Type-B rooting systems.
In free-sporing plants, rhizomes usually run horizontally, serving as a strategy for vegetative
reproduction. Vertical rhizome growth is rarely reported, particularly in the fossil record.
Recently, vertical rhizomes of a primitive lycopsid have been described by Xue et al. (2016)
from the Early Devonian paleosols of South China, showing evidence for the early acquisition
of this character in free-sporing plants. Vertical rhizome growth could be a mechanism to
accommodate the effects of frequent sediment burial.
Cladophlebis-type foliage remains have usually been allied to the Osmundaceae (e.g., Van
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Konijnenburg-van Cittert, 2002; Taylor et al., 2009). Fossil rhizomes of this group are mainly
based on anatomically permineralized material with limited morphological features (e.g.,
Gould, 1970; Tian et al., 2008; Yang et al., 2010). Rhizomes of three osmundaceous ferns
described from the Middle Jurassic of Liaoning Province, northeastern China, are surrounded
by a mantle of petiole bases and adventitious roots (Yang et al., 2010; Tian et al., 2013,
2014). Very well preserved Osmunda from the Jurassic of Sweden similarly shows a rhizome
up to 4 cm in diameter that is surrounded by a compact mantle of helically arranged,
persistent petiole bases and interspersed rootlets (Bomfleur et al., 2014, 2015). Rhizomes of
two extant osmundaceous ferns (Fig. 12(B, D)), as in their fossil relatives, are also
surrounded by petiole bases and are much larger than our Type-A and Type-B rooting
systems. Thus, the rhizome organization of osmundaceous ferns differs from the present
material, although shoot-borne and lateral roots of the two extant osmundaceous ferns and
our material are comparable in size (Table 1).
The Type-C rooting system differs from the rhizome-root systems discussed above: the
first-order lateral roots in Type-C show a decreasing diameter along a very short length,
while short-borne roots on a rhizome show a more-or-less constant diameter, excluding a
tapering tip (Figs. 3(A), 12). The Type-C rooting system recalls that of many extant
gymnosperms such as conifers, and is known from rooting systems as old as Late Devonian
progymnosperms such as Eddya Beck. The morphological reconstruction of roots of Eddya,
based on abundant anatomical material, shows a robust primary root and numerous lateral
roots (Beck, 1967). In gymnosperms, a primary root commonly grows to become a thick
central taproot, which then branches hierarchically to form a few orders of lateral roots
(Gregory, 2006). Such an organization is termed a taproot or allorhizic system (Bellini et al.,
2014), where the primary root is positively geotropic, and the first-order lateral roots more
widely scattered. The present fossil shows a frequently branched pattern, with laterals likely
close to the surface of the ground, making it comparable to the mesophytic root type of
modern plants (Cannon, 1949).
5.2. Interpretation of flora-associated lithofacies: implications for plant-soil interplay
Three lithofacies, Fpd, Fr and Fnp, are recognized in Bed-1 by detailed sedimentary analyses,
while their occurrences in Bed-2 are determined by field observations. Thus, the analysis
below is based on Bed-1, but we believe that similar patterns also pertain to Bed-2. The
extensive vertical rhizomes and roots in facies Fr, and its consistent color, suggest that this
facies represents a part of a buried soil experiencing a constant hydrological regime (i.e., a
stable water table). Facies Fpd contains abundant plant debris and usually forms couplets
together with facies Fr. For a single Fr-Fpd couplet, Fr is likely a subsurface horizon, while Fpd,
with an abundance of fossil foliage, represents the upper or uppermost horizon of an
ancient soil. The plant material accumulated in Fpd seems to have been reworked by
currents in shallow water, as evidenced by the occurrence of wavy laminations as well as
rhythmic alternation of plant debris and sediments (Fig. 10(B)). Such reworking processes
might have operated at a local scale, with potential for transportation of foliage of
Cladophlebis species within the community (i.e., parautochthonous burial), contributing to
their abundance and explaining their consistent orientation. Thus, if the Fr-Fpd couplets are
considered within a paleopedological context, the facies Fr and Fpd can be interpreted as
Page 8 of 28
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representing an A Horizon (layers with accumulation of organic matter mixed with mineral
fraction) and a reworked O Horizon (layers dominated by surface accumulation of organic
matter above an A Horizon), respectively (Retallack, 2001: p. 22; Schaetzl and Thompson,
2015: p. 30).
The facies Fnp, composed mostly of detrital sediments and with no or little plant debris,
adds to variations in sediment superposition pattern. One pattern forms an Fnp-Fr-Fpd
sequence, as shown in a sectioned specimen with an Fr-Fpd-Fnp-Fr-Fpd profile (Fig. 10(C)).
The Fnp is likely equivalent to a C Horizon (little altered and weathered parent material, with
geological structure and fabric; Retallack, 2001: p. 22; Schaetzl and Thompson, 2015: p. 30),
indicating the termination of local vegetation development. In this case, an Fnp-Fr-Fpd
sequence includes a more complete soil profile than an Fr-Fpd couplet alone. In another
pattern, Fpd units directly overlie facies Fnp with an undulating contact (Fig. 10(A)),
indicating re-deposition of sediments and plant debris transported from a nearby O Horizon
and/or probable erosion of a previously formed rooted horizon.
Root penetration is extensive in facies Fr and sometimes occurs in facies Fpd, while in other
respects, the facies Fr and Fpd seem to be little differentiated from their supposed parent
material, facies Fnp. Thus, Bed-1 can be considered as a cumulative sequence of Entisols
sensu Retallack (1993).
Bed-2 shows similar features to Bed-1, but is not described in detail here. The formation of
such Entisols represents the dynamic accumulation of plant matter and detrital sediments,
with decay subsequently inhibited by burial and waterlogging, leaving abundant in situ
preserved rhizomes and roots. By contrast, aboveground tissues were exposed to decay and
reworking by water currents, leaving only fragmentary preserved material.
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5.3. Implications of Type-A and Type-B rooting systems
The fossil rhizomes and shoot-borne roots described in this work shed light on
morphological disparity and conservatism of root evolution in ferns, although their
anatomical features are not preserved. The Type-A rooting system is probably attributed to
Cladophlebis and, most likely, to Cladophlebis cf. scariosa and/or C. delicatula, which
dominated the Bed-1 Flora. Although affinities between sterile foliage remains of
Cladophlebis and the Osmundaceae have commonly been suggested, unequivocal evidence
is lacking (Deng, 2002; Van Konijnenburg-van Cittert, 2002; Taylor et al., 2009; Tian et al.,
2016; Jarzynka, 2016). Moreover, while our fossils show resemblance of the shoot-borne and
lateral roots with both extinct and extant osmundaceous ferns, the rhizome morphology is
quite different. Rhizome-root architecture and dimensions found in our fossils do, however,
occur in diverse, distantly related fern taxa including members of the Gleicheniaceae and
Marsileaceae, as shown in this paper (see comparisons), and in fern-like plants such as those
from the Late Devonian (Wang et al., 2015; Xue and Basinger, 2016), perhaps pointing
towards a fundamental architecture among ferns.
In situ roots are important also for classification of paleosols and the interpretation of
ancient landscape surfaces, particularly in cases where the sediments may be little
differentiated from their parent material (Retallack, 2001). The Entisols that make up Bed-1
and Bed-2, and the preservation of organic remains throughout the sequences, indicate that
deep weathering of soils was inhibited by persistent high water tables and rapid
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sedimentation, as well as repetitive disturbance and burial of vegetated surfaces. The upper
part of earlier formed soils was frequently reworked during episodic sedimentary deposition
on a gently subsiding basin and buried in a shallow water setting. Nevertheless, it remains
difficult to estimate the time duration represented by the soil beds.
An interpretation of the present Cladophlebis species, most likely C. cf. scariosa and/or C.
delicatula, as semi-aquatic or wetland colonizers would be consistent with the interpretation
of the current-reworked paleosols as representing a marsh or wetland frequently disturbed
by clastic detritus influxes. The ecology of the genus Cladophlebis and other fossil ferns is
difficult to ascertain, and one of the reasons is that records of in situ preserved fossils are
rare, although species of Cladophlebis are widespread (e.g., Deng, 2002; Van
Konijnenburg-van Cittert, 2002; Sun et al., 2010; Akulov et al., 2015). Stems of 10-30 cm
wide belonging to Cladophlebis denticulata (Brongniart) Fontaine were found in growth
position in a paleosol from the Lower Jurassic of Romania (Van Konijnenburg-van Cittert,
2002, based on M.E. Popa?s unpublished data), indicating a much larger size for this species
than the present evidence would suggest. It was proposed that C. denticulata thrived in
marshes as they were filling with detrital material, or grew on the disturbed edges of
marshes (Van Konijnenburg-van Cittert, 2002). However, Barbacka (2011) suggested that C.
denticulata might have favored dry and disturbed conditions, while another species, C.
haiburnensis (Lindley et Hutton) Brongniart, might have grown in slightly wetter
environment, based on studies of Early Jurassic flora from southern Hungary. Cladophlebis
neimengguensis Deng, with fronds preserved in situ in the floor of a coal seam in the Lower
Cretaceous of Inner Mongolia, was interpreted as living in wetlands or marshes (Deng, 1995).
Parautochthonous remains of foliage of Cladophlebis species are common in coals and coal
roof beds, as well as floodplains (Deng, 1995, 2002; Van Konijnenburg-van Cittert, 2002; Sun
et al., 2010; Akulov et al., 2015), which would be consistent with growth in marsh or wetland
environments.
6. Conclusions
Two beds of paleosols with in situ preserved rooting systems are described from the Middle
Jurassic Upper Yaopo Fm. of western Beijing, China. Foliage specimens of Cladophlebis cf.
scariosa and C. delicatula dominate in Bed-1, associated with Type-A rooting system, and are
interpreted as representing a Cladophlebis-dominated community. Type-B and Type-C
rooting systems are found in Bed-2, where no identifiable foliage remains are available. The
Type-A and Type-B rooting systems show abundant vertically arranged rhizomes, dense
shoot-borne roots and fine lateral roots. These morphologies differ in rhizome organization
from that of osmundaceous ferns, a group to which Cladophlebis foliage remains are usually
allied, but are quite similar to those of some other ferns, indicating such rhizome-root
systems are probably conserved in at least some fern clades. The Type-C rooting system
shows a central main root and some smaller lateral roots; similar architecture typifies
taproot systems of many gymnosperms. Based on evidence from in situ preservation of
rooting systems and sedimentary features of the flora-associated lithofacies of Bed-1, a
dynamic process is inferred for the growth and burial of some Cladophlebis species. They are
interpreted as probable semi-aquatic or wetland colonizers growing in consistently
waterlogged paleosols, a cumulative sequence of Entisols with reworked O Horizon, A
Page 10 of 28
Horizon and C Horizon.
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Acknowledgments
This work was supported by the National Natural Science Foundation of China (N� 41722201
to J.X.) and Shandong Provincial Natural Science Foundation (N� ZR2017MD031 to C.Z.).
The authors thank Prof. Baoyu Jiang (Nanjing University) for discussion about the
sedimentological context, and Prof. Ge Sun (Shenyang Normal University), Dr. Ga雝an
Guignard (Universit� de Lyon) and an anonymous reviewer for their helpful comments on an
early version of this paper.
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References
Akulov, N.I., Frolov, A.O., Mashchuk, I.M., Akulova, V.V., 2015. Jurassic deposits of the
southern part of the Irkutsk sedimentary basin. Stratigr. Geo. Correl. 23, 387?409.
Barbacka, M., 2011. Biodiversity and the reconstruction of Early Jurassic flora from the
Mecsek Mountains (southern Hungary). Acta Palaeobot. 51, 127-179.
Beck, C.B., 1967. Eddya sullivanensis, gen. et sp. nov., a plant of gymnospermic morphology
from the Upper Devonian of New York. Palaeontogr. Abt. B 121, 1?22.
Bell, A.D., Tomlinson, P.B., 1980. Adaptive architecture in rhizomatous plants. Bot. J. Linn. Soc.
80, 125?160.
Bellini, C., Pacurar, D.I., Perrone, I., 2014. Adventitious roots and lateral roots: similarities
and differences. Ann. Rev. Plant Biol. 65, 639?666.
Bomfleur, B., McLoughlin, S., Vajda, V., 2014. Fossilized nuclei and chromosomes reveal 180
Million years of genomic stasis in royal ferns. Science 343, 1376?1377.
Bomfleur, B., Grimm, G.W., McLoughlin, S., 2015. Osmunda pulchella sp. nov. from the
Jurassic of Sweden ? reconciling molecular and fossil evidence in the phylogeny of modern
royal ferns (Osmundaceae). BMC Evol. Biol. 15, 126.
Cannon, W.A., 1949. A tentative classification of root systems. Ecology 30, 542?548.
Chen, F., Dou Y.W., Huang, Q.S., 1984. The Jurassic Flora of West Hills, Beijing (Peking).
Geological Publishing House, Beijing (in Chinese with English summary).
Deng, S.H., 1995. Early Cretaceous Flora from Huolinhe Basin, Inner Mongolia. Geological
Publishing House, Beijing (in Chinese with English summary).
Deng, S.H., 2002. Ecology of the Early Cretaceous ferns of Northeast China. Rev. Palaeobot.
Palynol. 119, 93?112.
Duan, S.Y., 1987. The Jurassic Flora of Zhaitang, Western Hills of Beijing. Department of
Geology, University of Stockholm and Department of Palaeobotany, Swedish Museum of
Natural History.
Gandolfo, M.A., Nixon, K.C., Crepet, W.L., Ratcliffe, G.E., 1997. A new fossil fern assignable to
Gleicheniaceae from Late Cretaceous sediments of New Jersey. Am. J. Bot. 84, 483?493.
Gould, R.E., 1970. Palaeosmunda, a new genus of siphonostelic osmundaceous trunks from
the Upper Permian of Queensland. Palaeontology 13, 10?28.
Gregory, P.J., 2006. Plant Roots: Growth, Activity and Interaction with Soils. Wiley-Blackwell,
Williston.
Groff, P.A., Kaplan, D.R., 1988. The relation of root systems to shoot systems in vascular
plants. Bot. Rev. 54, 387?422.
Page 11 of 28
Ac
ce
pt
e
d
M
an
us
cr
ip
t
Hetherington, A.J., Berry, C.M., Dolan, L., 2016. Networks of highly branched stigmarian
rootlets developed on the first giant trees. Proc. Natl. Acad. Sci. U.S.A. 113, 6695?6700.
Jarzynka, A., 2016. Fossil flora of Middle Jurassic Grojec clays (southern Poland). Raciborski?s
original material reinvestigated and supplemented. II. Pteridophyta. Osmundales. Acta
Palaeobot. 56, 83?221.
Kenrick, P., Strullu-Derrien, C., 2014. The origin and early evolution of roots. Plant Physiol.
166, 570?580.
McCormack, M.L., Guo, D.L., Iversen, C.M., Chen, W.L., Eissenstat, D.M., Fernandez, C.W., Li,
L., Ma, C.G., Ma, Z.Q., Poorter, H., Reich, P.B., Zadworny, M., Zanne, A., 2017. Building a
better foundation: improving root-trait measurements to understand and model plant and
ecosystem processes. New Phytol. 215, 27?37.
Newberry, J.S., 1866. Description of fossil plants from the Chinese coal-bearing rocks, in:
Pumpelly, R. (Ed.), Geological Researches in China, Mongolia, and Japan: During the Years
1862-1865. Smithsonian Institution, Appendix n� 1, pp. 119?128.
Raven, J.A., Edwards, D., 2001. Roots: evolutionary origins and biogeochemical significance. J.
Exp. Bot. 52, 381?401.
Retallack, G.J., 1993. Classification of paleosols: discussion and reply. Geol. Soc. Am. Bull. 105,
1635?1637.
Retallack, G.J., 2001. Soils of the Past: An Introduction to Paleopedology. Second Ed.
Blackwell Science Ltd.
Schaetzl, R.J., Thompson, M.L., 2015. Soils: Genesis and Geomorphology. Second ed.
Cambridge University Press, Cambridge.
Schneider, H., 2000. Morphology and anatomy of roots in the filmy fern tribe Trichomaneae
H. Schneider (Hymenophyllaceae, Filicatae) and the evolution of rootless taxa. Bot. J. Linn.
Soc. 132, 29?46.
Sun, G., Miao, Y.Y., Mosbrugger, V., Ashraf, A.R., 2010. The Upper Triassic to Middle Jurassic
strata and floras of the Junggar Basin, Xinjiang, Northwest China. Palaeobiodiv.
Palaeoenviron. 90, 203?214.
Taylor, T.N., Taylor, E.L., Krings, M., 2009. Paleobotany: The Biology and Evolution of Fossil
Plants. Second Ed. Academic Press, Amsterdam.
Tian, N., Wang, Y.D., Jiang, Z.K., 2008. Permineralized rhizomes of the Osmundaceae
(Filicales): diversity and tempo-spatial distribution pattern. Palaeoworld 17, 183?200.
Tian, N., Wang, Y.D., Zhang, W., Jiang, Z.K., Dilcher, D.L., 2013. Ashicaulis beipiaoensis sp.
nov., a new osmundaceous fern species from the Middle Jurassic of Liaoning Province,
Northeastern China. Int. J. Plant Sci. 174, 328?339.
Tian, N., Wang, Y.D., Philippe, M., Zhang, W., Jiang, Z.K., Li, L.Q., 2014. A specialized new
species of Ashicaulis (Osmundaceae, Filicales) from the Jurassic of Liaoning, NE China. J.
Plant Res. 127, 209?219.
Tian, N., Wang, Y.D., Dong, M., Li, L.Q., Jiang, Z.K., 2016. A systematic overview of fossil
osmundalean ferns in China: diversity variation, distribution pattern, and evolutionary
implications. Palaeoworld 25, 149?169.
Van Konijnenburg-van Cittert, J.H.A., 2002. Ecology of some Late Triassic to Early Cretaceous
ferns in Eurasia. Rev. Palaeobot. Palynol. 119, 113?124.
Wang, D.M., Xu, H.H., Xue, J.Z., Wang, Q., Liu, L., 2015. Leaf evolution in early-diverging ferns:
Page 12 of 28
Ac
ce
pt
e
d
M
an
us
cr
ip
t
insights from a new fern-like plant from the Late Devonian of China. Ann. Bot. 115,
1133?1148.
Wang, G., Wang, Y.L., Liu, A.J., Liu, J., Wang, T.H., 2010. Yaopo Formation depositional system
and related coal-accumulating factors in Muchengjian Mine Area, Beijing. Coal Geol. China
22, 19?22 (in Chinese with English abstract).
Xue, J.Z., Deng, Z.Z., Huang, P., Huang, K.J., Benton, M.J., Cui, Y., Wang, D.M., Liu, J.B., Shen,
B., Basinger, J.F., Hao, S.G., 2016. Belowgroud rhizomes in paleosols: the hidden half of an
Early Devonian vascular plant. Proc. Natl. Acad. Sci. U.S.A. 113, 9451?9456.
Xue, J.Z., Basinger, J.F., 2016. Melvillipteris quadriseriata gen. et sp. nov., a new plant from
the Upper Devonian (Famennian) of Arctic Canada. Geol. Mag. 153, 601?617.
Yamada, T., Kato, M., 2002. Regnellites nagashimae gen. et sp. nov., the oldest macrofossil of
Marsileaceae, from the Upper Jurassic to Lower Cretaceous of western Japan. Int. J. Plant Sci.
163, 715?723.
Yang, X.J., Zhang, W., Zheng, S.L., 2010. An Osmundaceous rhizomes with sterile and fertile
fronds and in situ spores from the Jurassic of western Liaoning. Chin. Sci. Bull. 55,
3864?3867.
Zhou, Z.Y., 1995. Jurassic floras. In: Li, X.X., Zhou, Z.Y., Cai, C.Y., Sun, G., Ouyang, S., Deng, L.H.
(Eds.), Fossil Floras of China Through the Geological Ages. Guangdong Science and
Technology Press, Guangzhou, pp. 260?309.
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Table and Figure captions
Dicranopteris dichotoma
based on specimen in Fig. 12A)
Shoot-borne root
0.3-2.0
Lateral root
0.1-0.2
Rhizome
1.3-6.8
Shoot-borne root
0.2-1.7
Lateral root
based on specimen in Fig. 12D)
?
?
113
6
55�
84
0.8-2.6
?
?
11
11-74
?
?
12
1.0-22
5
66�
55
0.1-0.5
0.6-1.9
?
63�
12
Rhizome
2.7
218
?
?
1
Shoot-borne root
0.4-1.5
9.9-53
5
61�
20
0.1-0.3
0.9-4.3
8
71�
12
2.2-2.5
43-93
?
?
2
0.4-0.6
13-50
6
65�
12
0.2-0.3
0.9-3.3
5
70�
8
Rhizome
?
?
?
?
?
Shoot-borne root
0.6-1.1
?
?
?
13
Lateral root
0.1-0.4
2.5-8.7
6
65�
14
Rhizome
?
?
?
?
?
Shoot-borne root
0.6-1.2
22-55
3
?
7
Lateral root
0.3-0.5
5.9-21
4
81�
7
Main root
30
64
?
?
1
First-order lateral root
2.0-4.2
5.3-58
4
58�
9
Second-order lateral root
0.2-1.6
1.0-9.8
4
53�
10
d
Shoot-borne root
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Osmunda cinnamomea var. asiatica
N
1.7-25
Lateral root
based on specimen in Fig. 12B)
Branching
angles
cr
6.4-68
Rhizome
based on specimen in Fig. 12C)
ype-C (Bed-2)
2.0-5.7
Lateral root
Gleichenia squamosissima
Osmunda japonica
Rhizome
Branching
density
us
ype-B (Bed-2)
Length (mm)
an
ype-A (Bed-1)
Root-trait measurements
Root-trait
Width (mm)
M
ooting system type
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Table 1. Morphological comparisons of rooting systems described in this study and those of
four extant ferns shown in Fig. 12. Branching density: number of roots on a 10 mm-long
rhizome/main root or lower-order root; branching angles: departing angles of roots from a
rhizome/main root or lower-order root; N: number of measurements; ?: character not
applicable or data not available.
Table 1.
Fig. 1. Map showing the location of the fossil site (Yuejiapo section of Mentougou District,
Beijing, China).
Fig. 2. Stratigraphic column and studied fossil beds of the Upper Yaopo Formation at the
Yuejiapo section. A. Right column showing only the upper part of the Upper Yaopo Fm. at
the studied site, where the two studied floras occur (Bed-1 and Bed-2); left column showing
the complete sequence of the formation at a nearby site, based on Chen et al. (1984); the
Page 14 of 28
basal conglomerates of the overlying Longmen Fm. are found at both sites. B-D. Lithologies
of Bed-2. B: Outcrop showing massive gray muddy siltstone; C: Plant debris on a sedimentary
surface, collected from the outcrop in B (upper arrow), specimen PKUB16286; D: Vertically
arranged plant rhizomes, collected from the outcrop in B (lower arrow), specimen
PKUB16287. E. Outcrop showing Bed-1 composed of massive muddy siltstone (bottom part
indicated by the pickax) and overlying beds composed of sandstone and siltstone. Scale bars:
20 cm (B), 20 mm (C, D), 1 m (E).
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Fig. 3. Diagrams showing the terminology for rooting systems of ferns and seed plants. A.
Rhizome, shoot-borne roots, and lateral roots of an extant fern, Dicranopteris sp.
(Gleicheniaceae). B. Enlarged from A, showing higher-order lateral roots and descriptive
terms such as branching angle and density. C. Sketch drawing of a trunk and taproot system
composed of a main root and numerous lateral roots. Scale bar: 10 mm (A).
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Fig. 4. Foliage fossils of Bed-1 Flora. A-C. Cladophlebis cf. C. scariosa Harris. A: Ultimate
pinnae, specimen PKUB16204. Note that the slightly falcate pinnules are arranged in a
subopposite pattern. The pinnules are attached to the rachis nearly at a right angle (arrow);
B: Bipinnate frond with sub-opposite ultimate pinnae, specimen PKUB16200a; C: Two
pinnules, showing a midvein and dichotomously branched lateral veins, specimen
PKUB16200a. D, E. Cladophlebis delicatula Yabe et 詉shi. D: Pinnules showing veins,
specimen PKUB16207. Arrow points to a tapering tip; E: Ultimate pinna with seven pinnules
at the left side, specimen PKUB16218b. F. Cladophlebis argutula (Heer) Fontaine, specimen
PKUB16203. Ultimate pinna with short, broad-based pinnules. Arrow points to a lateral vein
that is twice dichotomously branched. Scale bars: 5 mm (A, E, F), 10 mm (B), 2 mm (C, D).
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Fig. 5. Relative abundance of foliage specimens from Bed-1, showing the dominance of
Cladophlebis spp.
Fig. 6. Belowground fossils of Bed-1 Flora. A. Vertical section showing plant fossils and
sedimentary repetition of two lithological facies: fines (siltstone and mudstone) with
abundant plant debris (Fpd) and fines with in situ rooting systems (Fr). Such facies repetition
is interpreted as representing periodic disturbance and development of vegetation and soil.
Within a pedological context, facies Fpd represents a reworked soil surface (O Horizon) and
Fr represents an A Horizon (see text). Specimen PKUB16258. B. Two sedimentary cycles, each
of which includes lithofacies Fr and Fpd, from bottom to top. Arrows point to vertical
rhizomes. Specimen PKUB16249. C. Densely arranged rhizomes in lithofacies Fr. Specimen
PKUB16243. Scale bars: 50 mm (A), 10 mm (B, C).
Fig. 7. Belowground fossils of Bed-1 Flora. A. Vertical section showing interpreted vertically
arranged rhizomes bearing fine shoot-borne horizontal roots (arrows). Note that rhizomes
distortion is probably due to diagenetic compaction. Specimen PKUB16242. B. Vertically
arranged plant fossils interpreted as rhizomes. Specimen PKUB16257. C. Densely arranged
rhizomes. Dichotomous branching shown at arrow. Specimen PKUB16260. D. Rhizomes and
pinnae associated, but not attached. Black arrows point to a rhizome and pinna of
Page 15 of 28
Cladophlebis cf. scariosa Harris. White arrows indicate numerous shoot-borne roots borne
on a rhizome. Specimen PKUB16239. E. Vertically oriented rhizomes with shoot-borne roots
(arrows). Specimen PKUB16237. F, G. Rhizome fragments. Dichotomous branching at arrows.
F: Specimen PKUB16259; G: Specimen PKUB16262. Scale bars: 10 mm (A-F), 20 mm (G).
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Fig. 8. Box plot of measured width of rhizomes and shoot-borne roots of Bed-1 Flora. The
25-75% quartiles are drawn using a box, the median value is the horizontal line inside the
box, and minimum and maximum values are short horizontal lines below and above the box.
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Fig. 9. Vertical thin-section photomicrographs of major lithologies. A-C. Lithofacies Fpd, fines
with abundant plant debris, showing the arrangement of plant debris and wave ripples. A,B:
Slide 1607JX-06; C: Slide 1607JX-03; D-F. Lithofacies Fr, fines with in situ rooting systems.
Arrow points to fine lateral root. F. Enlargement of branched root in E. D: Slide 1607JX-03; E,
F: Slide 1607JX-06. G. Bioturbation (arrow) in lithofacies Fr. Slide 1607JX-08. H. Fines with no
plant fossils, lithofacies Fnp (fines with no or few plant fossils). Slide 1607JX-04. Scale bars:
1 mm (A, E, G), 500 ?m (B-D, F, H).
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Fig. 10. Polished sections showing lithofacies associated with Bed-1 Flora. A-C. Vertical
profile views. A: Sequence composed of two lithofacies: lower part, Fnp (fines with no or few
plant fossils); upper part, thick Fpd (fines with abundant plant debris). White arrows point to
vertical rhizomes, and black arrow to large plant debris. Lithofacies Fnp is interpreted as
representing the C Horizon of a paleosol, specimen PKUB16277; B: Lithofacies Fpd, showing
the arrangement of plant debris and wave ripples, specimen PKUB16280; C: Sequence of
lithofacies Fr, Fpd, Fnp, and again Fr and Fpd, from bottom to top, with arrows pointing to
vertical rhizomes, specimen PKUB16282. D. Polished horizontal section showing cross
sections of vertical rhizomes, which are preserved as compressions and showing thin
coalified vestiges in cross section (arrows). Horizontal sedimentary surface view. Specimen
PKUB16279. Scale bars: 20 mm (A), 10 mm (B, C), 5 mm (D).
Fig. 11. Belowground fossils of Bed-2 Flora. A-G. Type-B rooting system, with vertical
rhizomes bearing fine shoot-borne roots, which in turn bear lateral roots. A: Upper arrow
points to dichotomy, and lower arrow to the part enlarged in G, Specimen PKUB16292; B:
Specimen PKUB16291; C: Arrow points to a shoot-borne root enlarged in F, Specimen
PKUB16295-1; D: Specimen PKUB16295-2; E: Specimen PKUB16293; F, G: Enlargement of
shoot-borne roots and lateral roots (arrows). H. Taproot system comprised of a main root
and lateral roots (Type-C rooting system). Arrows 1-7 point to the bases of first-order lateral
roots. Specimen PKUB16288a. I. Enlargement of a lateral root in H (bottom), showing
higher-order lateral roots. J. Counterpart of specimen shown in H, showing expanded bases
of first-order lateral roots at arrows 8 and 9. Specimen PKUB16288b. Scale bars: 10 mm (A, E,
H, J), 5 mm (B-D, I), 1 mm (F, G).
Fig. 12. Rhizomes and shoot-borne roots of selected extant ferns, for morphological
comparisons with the studied fossils. A. Dicranopteris dichotoma (Thunb.) Bernh.
(Gleicheniaceae). The specimen label is in reverse orientation, because the plant stipes are
Page 16 of 28
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in correct orientation (upright). Specimen PE00234158. B. Osmunda japonica Thunb.
(Osmundaceae). Specimen PE00289782. C. Gleichenia squamosissima (Copel.) Nakai
(Gleicheniaceae). Specimen PE01623521. D. Osmunda cinnamomea L. var. asiatica Fernald
(Osmundaceae). Specimen PE00289592. All specimens are deposited at the Herbarium of
the Institute of Botany, Chinese Academy of Sciences, Beijing, China. Scale bars: 20 mm.
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2018, 004, geobios
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