| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Paleobotany |
2The Center of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, P. R. China; 3Florida Museum of Natural History, University of Florida, Gainesville, Florida 32611-7800 USA
Received for publication January 7, 2004. Accepted for publication September 9, 2004.
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
Key Words: architecture • arborescent lycopsids • Isoëtales s.l • Late Devonian • Leptophloeum rhombicum
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
; Scheckler, 1986
; DiMichele and Bateman, 1992
; Niklas, 1993
, 1997
; Niklas and Speck, 2001
; Bateman, 1994
, 1996
; Algeo et al., 1995
, 2001
; Srivastava and Srivastava, 2001
). However, compared with studies of coeval cladoxylaleans (Wang and Geng, 1997
; Berry and Fairon-Demaret, 2002
; Hilton et al., 2003
; Soria and Meyer-Berthaud, 2004
) and progymnosperms (Scheckler, 1976
, 1978
; Trivett, 1993
; Meyer-Berthaud et al., 1999
, 2000
), relatively little is known about the evolutionary-developmental changes resulting in modifications in the growth architecture of early arborescent lycopsids due to their poor preservation in Mid-Late Devonian sediments.
Leptophloeum is a genus of arborescent lycopsids first described by Dawson (1862)
from the Upper Devonian of Perry Basin, Maine, northeastern North America (Perry Formation, R. A. Gastaldo, Colby College, personal communication). Subsequently, it has been widely reported from the Late Devonian (Frasnian-Famennian) of Europe, Asia, Africa and Australia (Edwards and Berry, 1991
) and six species were documented in Fossilium Catalogus (Dijkstra and van Amerom, 1994
). However, based upon leaf cushion diagnosis, most of these species have been assigned to one taxon, i.e., the type species, L. rhombicum Dawson (Sze, 1952
; Li et al., 1986
; S. E. Scheckler, Virginia State University, personal communication). Leptophloeum rhombicum was reconstructed as a conceptual whole-plant species, bearing a stigmarian rhizomorph and an iso-dichotomous branching crown, about 10 meters tall (Li et al., 1986
; Lemoigne, 1988
). This plant was very common in the Late Devonian (Frasnian-Famennian) of China (Cai and Li, 1995
), but specimens with a preserved branching pattern are rare. Sporadic records from North America, Australia and China present thin stems (about 1 cm thick) that are isotomously forked (Dawson, 1863
; Carruthers, 1872
; Kräusel and Weyland, 1941
; Sze, 1956
; Li et al., 1986
; Scheckler, Virginia State University, personal communication). The previous reconstruction appears to lack unequivocal evidence for an iso-dichotomous branching crown.
In this paper, a reinvestigation of a L. rhombicum trunk from the early Upper Devonian of Hubei, China provides new insights into its growth architecture and advances our understanding of evolutionary-developmental biology of early rhizomorphic lycopsids.
|
MATERIALS AND METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
, was collected from Pingluoxiang, about 20 km southwest of Changyang City, Hubei Province, Central China (Fig. 1). It occurred in a yellowish mudstone bed near the bottom of the Huangchiateng (Huangjiadeng) Formation. This formation consists of quartz sandstone, fine sandstone, arenaceous mudstone, and mudstone sediments, which is of early Late Devonian age (Feng, 1984
; Geng, 1990
; Chen and Jin, 1996
; Cai, 2000
; Wang, 2002
; Wang et al., 2002
; for a related stratigraphic column see Wang et al., 2003b
).
|
original material (Fig. 14). It is preserved as a flattened petrification (Figs. 2, 3). Its anatomy is predominantly replaced by siliceous minerals and contains the primary vasculature that can be seen in cross section (Fig. 4). External morphology shows distinctive rhombic leaf cushions characteristically assignable to L. rhombicum Dawson. The mid-lower part of the trunk (Fig. 2, C; Fig. 14, C, D) was examined by Geng (1990)
. Here, we reinvestigated the remaining material (Figs. 2, 14, A, B). Using a standard procedure (Stein et al., 1982
), the specimen was photographed, embedded, and cut into serial wafers (Vari/Cut, VC-50, Leco Corporation, St. Joseph, Michigan) for examination with reflected light under a light microscope (LEICA, MZ12, Vermont Optechs, Inc., Charlotte). Combined with previous anatomical and morphological data on L. rhombicum (Li et al., 1986
; Cai and Qin, 1986
; Geng, 1990
, 1995
), we analyzed its ontogeny and architecture. Figures were digitized using CorelDRAW 9 software (Chinese edition, Tianlong Corporation, Beijing). The specimen and slides are housed at the Institute of Botany, Chinese Academy of Sciences, Beijing, P. R. China.
|
|
|
RESULTS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
; Pichi-Sermoilli, 1958
; Banks, 1960
; Chaloner, 1967
; Plumstead, 1967
; Gu and Zhi, 1974
), or rarely in the Leptophloeodendrales (Lemoigne, 1982
) and the Lepidophytales (Danzé-Corsin, 1962
). Li et al. (1986)
tentatively transferred this genus from the Protolepidodendrales to the Lepidodendrales. Cai and Qin (1986)
and Geng (1990)
supported this position through anatomical studies. In this paper, we place Leptophloeum and its own family in the Isoëtales s.l., because recent phylogenetic analyses supported two major clades, the Lepidodendrales and the Isoëtales sensu stricto which constitute a monophyletic group, i.e., the Isoëtales s.l. (DiMichele and Bateman, 1996
; Kenrick and Crane, 1997
; Wang, 2002
; Wang et al., 2003a
).
emend. Li, Dou et Sun 1986
Description
The trunk presented here is straight, tapered acropetally, about 30 cm long and 6.8–8.0 cm wide, consisting of three larger fragments A, B and C (Figs. 2, 3). Besides these three fragments, Geng's (1990
, Plate, Fig. 1) original trunk also included an associated fragment D in the lowermost part (Fig. 14), about 7.6 cm long and 6.0–7.0 cm wide (incomplete), which was cut into wafers. Both surfaces of the trunk have obvious leaf cushions, which form even parastichies, showing the lepidodendroid phyllotaxy (sensu Grierson and Banks, 1963
; Thomas and Meyen, 1984
). The leaf cushion interareas are absent. Leaf cushions are rhombic, about 8–10 mm high and 10–12 mm wide, and the height-to-width ratios appear to be higher in the lower part of the trunk. In a few instances, a tiny dent can be observed in the upper corner of leaf cushions, possibly representing a ligule pit. There is an oval leaf scar (Fig. 5), about 3.0–3.5 mm long and 1.5–2.0 mm wide, approximately in the center of the leaf cushion.
There is a middle longitudinal ridge through the length of the trunk surface (Fig. 2), over the position of the internal vascular system, which can be seen in cross section (Fig. 4). Only a small amount of vascular tissue is present, accounting for only about 2% of the stem area in cross section. The vascular tissue is displaced to one side of the stem. The anatomically preserved portions are unevenly permineralized. A longitudinal section perpendicular to the flattened trunk was prepared from the lower part of fragment B (Figs. 6, 7), showing the primary vascular tissue. The protoxylem tracheids are poorly preserved. The metaxylem tracheids are elongated with tapered end walls and scalariform thickenings. In the lower level of fragment B (Fig. 7), the tracheids are very long, about 50–120 µm in diameter and 800–2000 µm in length. In the higher level, however, there is a small area consisting of very short tracheids (Fig. 6), about 50–120 µm in diameter and 200–600 µm in length, which may represent a lateral trace. Subsequently, six transverse sections were examined from successive higher levels (Figs. 8–13). These sections appear to contain exclusively primary vascular systems, which are irregular elliptical to round in outline. Because of poorly preserved protoxylem, the primary xylem elements are somewhat irregularly arranged, and we can not determine if they are exarch. The stele is reduced to a tiny rod of solid or medullated primary xylem. From the lower levels, a distinctive branch trace was observed in one of the two serial transverse sections (Figs. 12, 13). This small branch trace is not intact, and is adjacent to the main stele in a possibly elliptical outline. Along ascending levels, there are some regular circular cavities in the center of the stele, representing probable pith. The pith may begin to accrue acropetally in the area, starting from the branching position. No extra-stelar tissues were observed.
|
|
DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
original material and related study, the trunk can be reconstructed as a three-dimensional architectural model, about 37.6 cm in height and 4.3–5.3 cm in diameter, calculated by its width (sensu Pigg and Rothwell, 1985
; Leary and Thomas, 1989
) (Fig. 14, E). Judging from its diameter, the trunk appears to represent a young lycopsid tree. The support for this suggestion comes from the fact that the preserved stem portion goes from protostelic to siphonostelic stelar system, while the stem diameter decreases. It also has continuous leaf bases that are nearly contiguous, suggesting that the stem still lacked active secondary growth in diameter. Nor is there any evidence of peridermal tissue. It does not represent the terminal iso-dichotomous branching pattern seen in Carboniferous arborescent lycopsids such as Paralycopodites brevifolius and Diaphorodendron scleroticum (DiMichele and Phillips, 1985
; DiMichele and Bateman, 1992
). We observed only one small branch trace, while there should be other lateral branches if this fossil represents a branch in a Leptophloeum tree canopy through the process of reiteration in tree architecture (sensu Tomlinson, 1983
). Lateral branch formation in trees can be related to different species within a genus, suggesting that there may be genetic determinism (Bateman and DiMichele, 1991
, 1994
; Nicolini et al., 2001
). Therefore, genetic factors may influence the lateral branch formation in this monotypic genus Leptophloeum. The appearance of lateral branches may be linked to changes in a tree's environment, such as edaphic and/or climatic factors, insect attacks (Wnuk, 1985
; Nicolini et al., 2001
), and the variable light between open and closed swamp forest canopies. Lateral branches of arborescent lycopsids may be ephemeral and caducous, often associated with a natural pruning process (Jonker, 1976
; Wang et al., 2003b
), which may increase plant exposure to light. Anatomically, the primary xylem tracheids are very long prior to branching, which suggests that Leptophloeum may have developed by rapid axial elongation. Besides the primary vascular system examined here, a living Leptophloeum tree, like most of arborescent lycopsids in general, probably had a very thick mantle consisting of massive cortical tissue and some secondary woody tissue so that it could maintain an upright stature, developing into a self-supporting form (sensu Speck and Rowe, 1999
).
As for other anatomical features, Geng (1990
, 1995
) described the features of the tracheid structure under SEM and of leaf cushions, demonstrating that the plant is ligulate and has Williamson's striations in the metaxylem tracheids and possibly contains secondary xylem from the lower level of the trunk presented here (Fig. 2, C; Fig. 14, C, D). Cai and Qin (1986)
reported a L. rhombicum trunk from the Upper Devonian (Famennian) Hongguleleng Formation of Xinjiang, northwest China. It possesses an exarch protostele surrounded by an extensive secondary xylem with radial rays and probably is from the lower level of a mature Leptophloeum tree. These two studies demonstrated that the secondary xylem of a L. rhombicum tree diminished in thickness toward the trunk apex. In combination with our current study, the ontogenetic changes of this plant show a determinate growth pattern similar to that of Carboniferous arborescent lycopsids, such as Lepidophloios and Lepidodendron (Andrews and Murdy, 1958
; Eggert, 1961
; Wnuk, 1985
). We suggest that the L. rhombicum tree probably rarely branched, similar to Carboniferous arborescent lycopsids, such as Paralycopodites brevifolius, Diaphorodendron scleroticum (DiMichele and Phillips, 1985
; DiMichele and Bateman, 1992
), or Bothrodendron punctatum (Wnuk, 1989
). Therefore, the L. rhombicum tree produced lateral branching systems by pseudomonopodial branching of the trunk rather than equal ramifications as formerly thought. These lateral branches may have been sparsely positioned on the trunk. Such an architectural analysis raises the question of why there are no visible branch scars on the surface of the trunk. Based upon anatomical observations, we suggest that most branch traces may have been crushed towards either side of the trunk during preservation. This happened because the direction of compression was, more or less, perpendicular to both the main trunk and the lateral branches during the fossilization processes (Fig. 14, F). We suggest that the trunk bore biseriate to alternate lateral branches, which grew by means of isotomous dichotomies (i.e., formerly documented small forks), forming a slender canopy. Remarkably, a trunk with Ulodendron-scars was discovered in another Late Devonian (Famennian) arborescent lycopsid Sublepidodendron songziense from Hubei, China (Wang et al., 2003b
). We propose that similar specimens of L. rhombicum will be discovered in future collections.
As for other biological properties, Li et al. (1986)
comprehensively reviewed L. rhombicum Dawson. The associated vegetative leaves are linear with swollen leaf bases (Zhao et al., 1986
) whereas its fertile leaves are peltate in outline, possibly aggregating into a strobilus (Carruthers, 1872
; Walton, 1926
; Kräusel and Weyland, 1941
; Li et al., 1986
). No in situ spores are known, although Lemoigne (1982)
described a possible megaspore. Recently, Wang et al. (2003c)
described a new Lepidostrobus species from the Upper Devonian in Xinjiang, China, that also contained abundant L. rhombicum stem impressions in the same horizon, but there was no evidence for an organic connection between these two taxa. As for the rooting system, Li et al. (1986)
reported a 65 cm long Leptophloeum trunk, with a Stigmaria-type appearance of a 7.5 cm wide base, from the Upper Devonian in Xinjiang, China. Also, Hlustik (1991)
described numerous L. rhombicum stems, stumps and stigmarian root systems preserved in situ within the Upper Devonian (Famennian) of Libya, North Africa. To date, the widest L. rhombicum stem known is at least 52 cm from the Upper Devonian of China (Li et al., 1986
) and up to 30–40 cm in diameter from Australia (S. E. Scheckler, Virginia State University, personal communication). So a well-developed Leptophloeum tree is up to 10–25 meters tall and 0.3–0.4 meters thick at the base. Based upon the above discussion, a new reconstruction is presented (Fig. 15) for the general habit of L. rhombicum with special reference to previous works of DiMichele and Phillips (1985)
, Wnuk (1985)
and Wang et al. (2003b)
.
|
; Bateman, 1994
). However, the dearth of a fossil record of organic connections between these modules greatly hinders an accurate understanding for reconstructing a whole-plant species concept. Current understanding of the early radiations of rhizomorphic lycopsids has been dramatically augmented by recent description of the Famennian taxa (Wang, 2001
; Cai et al., 2002
; Wang et al., 2002
, 2003b
, c
; Berry et al., 2003
; Klavins, 2004
; Wang and Xu, in press
; Cressler and Pfefferkorn, in press
). The diverse architectural forms from this time suggest that rhizomorphic lycopsids have undergone evident diversification into two major clades—the Lepidodendrales bearing stigmarian rhizomorphs, and Isoëtales s. s. bearing cormose rhizomorphs. Lepidosigillaria whitei (Griseron and Banks, 1963
; Pigg, 2001
), Clevelandodendron ohioensis (Chitaley and Pigg, 1996
), and Otzinachsonia beerboweri (Cressler and Pfefferkorn, in press
) may be progenitors of the Carboniferous Isoëtales s. s. Sublepidodendron songziense, bearing a stigmarian rhizomorph and lateral branches may be a member of the group ancestral to the monosporangiate-strobilus clade of the Carboniferous Lepidodendrales (Wang and Hao, 2003
; Wang et al., 2002
, 2003a
, b
, c
). This suggests that diverse architecture of arborescent lycopsids might have undergone incipient radiations by the Frasnian of the Late Devonian. Longostachys latisporophyllus (Cai and Chen, 1996
) from the Givetian and Chamaedendron multisporangiatum (Schweitzer and Li, 1996
) from the Frasnian of China, despite their small size, possess a dichotomous rooting system and branching crown, which shows a close affinity to true arborescent lycopsids (Gensel and Berry, 2001
; Berry and Fairon-Demaret, 2001
; Wang et al., 2003c
).
Current anatomical evidence from a L. rhombicum trunk confirms that the pseudomonopodial architectural forms in rhizomorphic lycopsids have occurred in the early Late Devonian. Widespread occurrence of Leptophloeum implies that it must have undergone rapid speciation with such a structurally modular architecture. Robust cladistic, evolutionary, and developmental studies have predicted a hypothetical ancestral architecture in the basal rhizomorphic lycopsids (Bateman, 1992
, 1994
, 1996
; Bateman and DiMichele, 1991
, 1994
; Bateman et al., 1992
; DiMichele and Bateman, 1992
), which is similar to that of L. rhombicum presented here. Therefore, in future efforts to understand early evolution of the growth architecture of rhizomorphic lycopsids, we should pay more attention to the Frasnian and Givetian taxa, such as Lepidosigillaria whitei (Kräusel and Weyland, 1949
; Grierson and Banks, 1963
; Scheckler, 1986
) and Sigillaria? gilboense (Grierson and Banks, 1963
; Banks, 1966
) from the Givetian-Frasnian of New York, USA, Lepidodendropsis arborescens (Gu and Zhi, 1974
; stem impressions up to 12 cm wide from Yunnan, C. M. Berry, Cardiff University, UK, personal communication), Longostachys latisporophyllus (Cai and Chen, 1996
) from the Givetian of China, Atasudendron mirum (Senkevitch et al., 1993
; Berry and Fairon-Demaret, 2001
) from the Givetian of Kazakhstan, and Protolepidodendropsis pulchra (Schweitzer, 1965
; Berry and Fairon-Demaret, 2001
) from the Givetian of Spitzbergen.
|
FOOTNOTES |
|---|
4 happyking2644{at}sina.com
; dilcher{at}flmnh.ufl.edu
|
LITERATURE CITED |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
Algeo T. J. S. E. Scheckler J. B. Maynard 2001 Effects of the Middle to Late Devonian spread of vascular land plants on weathering regimes, marine biotas, and global climate. In P. G. Gensel and D. Edwards [eds.], Plants invade the land: evolutionary & environmental perspectives, 213–236. Columbia University Press, New York, New York, USA
Andrews H. N. W. H. Murdy 1958 Lepidophloios and ontogeny in arborescent lycopods. American Journal of Botany 45: 552-560
Banks H. P. 1960 Notes on Devonian lycopods. Senckenbergiana Lethaea 41: 59-88
Banks H. P. 1966 Devonian flora of New York State. Empire State Geogram 4: 10-24
Bateman R. M. 1992 Morphometric reconstructuion, palaeobiology and phylogeny of Oxroadia gracilis Alvin emend. and O. conferta sp. nov.: anatomically-preserved rhizomorphic lycopsids from the Dinantian of Oxroad Bay, Se Scotland. Palaeontographica 228B: 29-103
Bateman R. M. 1994 Evolutionary-developmental changes in the growth architecture of fossil rhizomorphic lycopsids: scenarios constructed on cladistic foundations. Biological Review 69: 527-597[CrossRef]
Bateman R. M. 1996 Nonfloral homoplasy and evolutionary scenarios in living and fossil land plants. In M. J. Sanderson and L. Hufford [eds.], Homoplasy: the recurrence of similarity in evolution, 91–130. Academic Press, London, UK
Bateman R. M. W. A. DiMichele 1991 Hizemodendron, gen. nov., a pseudoherbaceous segregate of Lepidodendron (Pennsylvanian): phylogenetic context for evolutionary changes in lycopsid growth architecture. Systematic Botany 16: 195-205[CrossRef][ISI]
Bateman R. M. W. A. DiMichele 1994 Saltational evolution of form in vascular plants: a neoGoldschmidtian synthesis. In D. S. Ingram and A. Hudson [eds.], Shape and form in plants and fungi, 63–102.Academic Press, London, UK
Bateman R. M. W. A. DiMichele D. A. Willard 1992 Experimental cladistic analysis of anatomically preserved arborescent lycopsids from the Carboniferous of Euramerica: an essay on paleobotanical phylogenetics. Annals of the Missouri Botanical Garden 79: 500-559[CrossRef][ISI]
Berry C. M. M. Fairon-Demaret 2001 The Middle Devonian flora revisited. In P. G. Gensel and D. Edwards [eds.], Plants invade the land: evolutionary & environmental perspectives, 120–139. Columbia University Press, New York, USA
Berry C. M. M. Fairon-Demaret 2002 The architecture of Pseudosporochnus nodosus Leclercq et Banks: a Middle Devonian Cladoxylopsid from Belgium. International Journal of Plant Sciences 163: 699-713[CrossRef]
Berry C. M. Y. Wang C. Cai 2003 A lycopsid with novel reproductive structures from the Upper Devonian of Jiangsu, China. International Journal of Plant Sciences 164: 263-273[CrossRef]
Cai C. 2000 Non-marine Devonian System. In Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences [ed.], Stratigraphical studies in China (1979–1999), 95–127. China University of Science and Technology Press, Hefei, P. R. China
Cai C. L. Chen 1996 On a Chinese Givetian lycopod, Longostachys latisporophyllus Zhu, Hu and Feng, emend.: its morphology, anatomy and reconstruction. Palaeontographica 238B: 1-43
Cai C. S. Chitaley Y. Dou 2002 Studies on some permineralized lycopsid remains from the Upper Devonian of North Xinjiang, NW China. Palaeontographica 262B: 119-136
Cai C. X. Li 1995 A review of Silurian and Devonian macrofloras in China. Palaeontologia Cathayana 6: 167-214
Cai C. H. Qin 1986 First discovery of a stem with internal structure referable to Leptophloeum rhombicum from the Upper Devonian, Xinjiang. Acta Palaeontologica Sinica 25: 516-524
Carruthers W. 1872 Notes on fossil plants from Queensland, Australia. Quarterly Journal of the Geological Society of London 28: 350-360
Chaloner W. G. 1967 Lycophyta. In W. G. Boureau, O. A. Høeg, S. Jovet-Ast, and W. G. Chaloner [eds.], Traité de Paléobotanique 2, 435–802. Masson et Cie, Paris, France
Chaloner W. G. A. Sheerin 1979 Devonian macrofloras. In The Devonian System, Special Papers in Palaeontology 23: 145–161. Palaeontological Association, London, UK
Chen G. J. Jin 1996 Devonian-Jurassic. In Bureau of Geology and Mineral Resources of Hubei Province [eds.], Stratigraphy (Lithostratic) of Hubei Province, 140–160. China University of Geosciences Press, Wuhan, P. R. China
Chitaley S. K. B. Pigg 1996 Clevelandodendron ohioensis, gen. et sp. nov., a slender upright lycopsid from the Late Devonian Cleveland Shale of Ohio. American Journal of Botany 83: 781-789[CrossRef][ISI]
Cressler W. L. H. W. Pfefferkorn In press A Late Devonian isoetalean lycopsid, Otzinachsonia beerboweri, gen. et sp. nov., from north-central Pennsylvania, USA. American Journal of Botany.
Danzé-Corsin P. 1962 Les Lépidophytes, historique et classifications. Annales des Sciences Naturelles, Botanique et Biologie Végétale 12: 293-319
Dawson J. W. 1862 On the flora of the Devonian period in North-Eastern America. Quarterly Journal of the Geological Society of London 18: 296-330
Dawson J. W. 1863 Further observations on the Devonian plants of Maine, Gaspé, and New York. Quarterly Journal of the Geological Society of London 19: 458-473
Dijkstra S. J. H. W. J. van Amerom 1994 Lycopodiales XI 2. Supplement. In H. W. J. van Amerom [ed.], Fossilium Catalogus II: Plantae 95, 129–143. Kugler Publications, Amsterdam, The Netherlands
DiMichele W. A. R. M. Bateman 1992 Diaphorodendraceae, fam. nov. (Lycopsida: Carboniferous): systematics and evolutionary relationships of Diaphorodendron and Synchysidendron, gen. nov. American Journal of Botany 79: 605-617[CrossRef][ISI]
DiMichele W. A. R. M. Bateman 1996 The rhizomorphic lycopsids: a case-study in paleobotanical classification. Systematic Botany 21: 535-552[CrossRef][ISI]
DiMichele W. A. T. L. Phillips 1985 Aborescent lycopod reproduction and paleoecology in a coal-swamp environment of Late Middle Pennsylvanian age (Herrin coal, Illinois, U.S.A). Review of Palaeobotany and Palynology 44: 1-26
Edwards D. C. M. Berry 1991 Silurian and Devonian. In C. J. Cleal [ed.], Plant fossils in geological investigation: the Palaeozoic, 117–153. Ellis Horwood Limited, UK
Eggert D. A. 1961 The ontogeny of Carboniferous arborescent lycopsida. Palaeontographica 108B: 43-92
Feng S. 1984 Devonian system and plant kingdom. In Institute of Geology and Mineral Resources of Yichang [eds.], Biostratigraphy of the Yangtze Gorge Area-Late Palaeozoic Era, 3: 6–31, 293–317. Geological Publishing House, Beijing, P. R. China
Geng B. 1990 New observations on Leptophloeum rhombicum from the Upper Devonian of Hubei, China. Acta Botanica Sinica 32: 951-956
Geng B. 1995 Leptophloeum rhombicum. In C. Li and J. Cui [eds.], Atlas of fossil plant anatomy in China, 18. Science Press, Beijing, P. R. China
Gensel P. G. C. M. Berry 2001 Early lycophyte evolution. American Fern Journal 91: 74-98[CrossRef][ISI]
Grierson J. D. H. P. Banks 1963 Lycopods of the Devonian of New York State. Palaeontographica Americana 4: 220-295
Gu (Nanjing Institute of Geology and Palaeonotology) and Zhi (Institute of Botany, Beijing). 1974 Chinese plant fossils, vol. 1, Chinese Palaeozoic plants, 21–23. Science Press, Beijing, P. R. China
Hilton J. B. Geng P. Kenrick 2003 A novel Late Devonian (Frasnian) woody cladoxylopsid from China. International Journal of Plant Sciences 164: 793-805[CrossRef][ISI]
Hlustik A. 1991 Late Palaeozoic floras of the Wadi ash Shati area, Libya. In M. J. Salem, O. S. Hammuda, and B. A. Eliagoubi [eds.], The geology of Libya: Third Symposium on the Geology of Libya, 1275–1284. Elsevier, Amsterdam, The Netherlands
Jonker F. P. 1976 The Carboniferous "genera" Ulodendron and Halonia-an assessment. Palaeontographica 157B: 97-111
Kenrick P. P. R. Crane 1997 The origin and early diversification of land plants: a cladistic study. Smithsonian Institution Press, Washington, D.C., USA
Klavins S. D. 2004 Re-interpretation of Wexfordia hookense from the Upper Devonian of Ireland as an arborescent lycophyte. Botanical Journal of the Linnean Society 144: 275-287[CrossRef]
Kräusel R. H. Weyland 1941 Pflanzenreste aus dem Devon von Nord-Amerika. Palaeontographica 86B: 1-78
Kräusel R. H. Weyland 1949 Pflanzenreste aus dem Devon. XIV. Gilboaphyton und die Protolepidophytales. Senckenbergiana 30: 129-152
Leary R. L. B. A. Thomas 1989 Lepidodendron aculeatum with attached foliage: evidence of stem morphology and fossilization processes. American Journal of Botany 76: 283-288[CrossRef][ISI]
Lemoigne Y. 1982 Le Genre Leptophloeum Dawson, 1862 Du Dévonien. Géobios 15: 33-41
Lemoigne Y. 1988 La flore au cours des temps géologiques. Géobios (mé moire spécial) 10: 130-132 Édition De L' Université Claude-Bernard, Lyon, France
Li X. Y. Dou Z. Sun 1986 The genus Leptophloeum Dawson based on a recent study of new material from the Junggar Basin, Xinjiang. Acta Palaeontologica Sinica 25: 349-379
Meyer-Berthaud B. S. E. Scheckler J. Wendt 1999 Archaeopteris is the earliest known modern tree. Nature 398: 700-701[CrossRef]
Meyer-Berthaud B. S. E. Scheckler J.-L. Bousquet 2000 The development of Archaeopteris: new evolutionary characters from the structural analysis of an Early Famennian trunk from southeast Morocco. American Journal of Botany 87: 456-468
Nicolini E. B. Chanson F. Bonne 2001 Stem growth and epicormic branch formation in understory beech trees (Fagus sylvatica L). Annals of Botany 87: 737-750
Niklas K. J. 1993 Ontogenetic-response models and the evolution of plant size. Evolutionary Trends in Plants 7: 42-48
Niklas K. J. 1997 The evolutionary biology of plants, 1–449. The University of Chicago Press, Illinois, USA
Niklas K. J. T. Speck 2001 Evolutionary trends in safety factors against wind-induced stem failure. American Journal of Botany 88: 1266-1278
Pigg K. B. 2001 Isoetalean lycopsid evolution: from the Devonian to the present. American Fern Journal 91: 99-114[CrossRef][ISI]
Pigg K. B. G. W. Rothwell 1985 Cortical development in Chaloneria cormosa (Isoetales), and the biological derivation of compressed lycophyte decortication taxa. Palaeontology 28: 545-553[ISI]
Pichi-Semolli R. E. G. 1958 The higher taxa of the pteridophyta and their classification. In O. Hedberg [ed.], Systematics of to-day. Uppsala Universitets Årsskrift (Acta Universitatis Upsaliensis) 6: 70-90
Plumstead E. P. 1967 A general review of the Devonian fossil plants found in the Cape System of South Africa. Palaeontologia Africana, Annals of the Bernard Price Institute for Palaeontological Research (University of the Witwatersrand, Johannesburg) 10: 1-83
Scheckler S. E. 1976 Ontogeny of progymnosperms. I. Shoots of Upper Devonian Aneurophytales. Canadian Journal of Botany 54: 202-219[ISI]
Scheckler S. E. 1978 Ontogeny of progymnosperms. II. Shoots of Upper Devonian Archaeopteridales. Canadian Journal of Botany 56: 3136-3170[CrossRef]
Scheckler S. E. 1986 Floras of the Devonian-Mississippian transition. In R. A. Gastaldo and T. W. Broadhead [eds.], Land plants: notes for a short course, 81–96. University of Tennessee Department of Geological Sciences Studies in Geology 15
Schweitzer H.-J. 1965 Über Bergeria mimerensis und Protolepidodendropsis pulchra aus dem Devon Westspitzbergen. Palaeontographica 115B: 117-138
Schweitzer H.-J. C. Li 1996 Chamaedendron nov. gen., eine multisporangiate lycophyte aus dem Frasnian Südchinas. Palaeontographica 238B: 45-69
Senkevitch M. A. A. L. Yurina A. D. Arkhangelskaya 1993 On fructifications, morphology and anatomy of Givetian lepidophytes in Kazakhstan (USSR). Palaeontographica 230B: 43-58
Soria A. B. Meyer-Berthaud 2004 Tree fern growth strategy in the Late Devonian cladoxylopsid species Pietzschia levis from the study of its stem and root system. American Journal of Botany 91: 10-23
Speck T. N. P. Rowe 1999 A quantitative approach for analytically defining size, growth form and habit in living and fossil plants. In M. H. Kurmann and A. R. Hemsley [eds.], The evolution of plant architecture, 447–479. Whitstable Litho Printers Ltd.,Whitstable, Kent, UK
Srivastava G. K. P. C. Srivastava 2001 Origin and evolution of heterosporous lycopods. Phytomorphology (Golden Jubilee Issue) 51: 499–527
Stein W. E. D. C. Wight C. B. Beck 1982 Techniques for preparation of pyrite and limonite permineralizations. Review of Palaeobotany and Palynology 36: 185-194[CrossRef]
Sze H. C. 1952 Upper Devonian plants from China. Scientia Sinica 1: 166-192
Sze H. C. 1956 Ein neuer fund von Leptophloeum rhombicum Dawson aus dem Oberdevon von Sinkiang. Acta Palaeontologica Sinica 4: 361-363
Thomas B. A. S. V. Meyen 1984 A system of form-genera for the Upper Palaeozoic lepidophyte stems represented by compression-impression material. Review of Palaeobotany and Palynology 41: 273-281[CrossRef]
Tomlinson P. B. 1983 Tree architecture: new approaches help to define the elusive biological property of tree form. American Scientist 71: 141-149[Medline]
Trivett M. L. 1993 An architectural analysis of Archaeopteris, a fossil tree with pseudomonopodial and opportunistic adventitious growth. Botanical Journal of the Linnean Society 111: 301-329[CrossRef]
Walton J. 1926 On some Australian fossil plants referable to the genus LeptophloeumDawson. Manchester Memoirs 70: 113-123
Wang Q. 2002 Studies on the genus Sublepidodendron (Nathorst) Hirmer, 1927. Ph.D. dissertation, Peking University, Beijing, P. R. China. Request at website: http://www.lib.pku.edu.cn/xwlw.html
Wang Q. S. Hao 2003 Review of the genus Sublepidodendron (Nathorst) Hirmer, 1927. Acta Palaeontologica Sinica 42: 598-612
Wang Q. S. Hao D. Wang 2003a A cladistic study on Sublepidodendron (Nathorst) Hirmer and its related genera. Acta Scientiarum Naturalium Universitatis Pekinensis 39: 858-870
Wang Q. S. Hao D. Wang D. L. Dilcher 2002 An anatomically preserved arborescent lycopsid, Sublepidodendron songziense (Sublepidodendraceae), from the Late Devonian of Hubei, China. American Journal of Botany 89: 1468-1477
Wang Q. S. Hao D. Wang Y. Wang T. Denk 2003b A Late Devonian arborescent lycopsids Sublepidodendron songziense emend. (Sublepidodendraceae Kräusel et Weyland 1949), with a revision of the genus Sublepidodendron (Nathorst) Hirmer 1927. Review of Palaeobotany and Palynology 127: 269-305[CrossRef][ISI]
Wang Q. C. Li B. Geng S. Chitaley 2003c A new species of Lepidostrobus from the Upper Devonian of Xinjiang, China and its bearing on the phylogenetic significance of the order Isoëtales. Botanical Journal of the Linnean Society 143: 55-67[CrossRef]
Wang Y. 2001 A new lycopsid megaspore cone from the Upper Devonian of Chaohu, China. Botanical Journal of the Linnean Society 136: 439-448[CrossRef]
Wang Y. H. Xu In press Sublepidodendron grabaui (Sze) emend. A lycopsid from Upper Devonian of China. Botanical Journal of the Linnean Society.
Wang Z. B. Geng 1997 A new Middle Devonian plant: Metacladophyton tetraxylum gen. et sp. nov. Palaeontographica 243B: 85-102
Wnuk C. 1985 The ontogeny and paleoecology of Lepidodendron rimosum and Lepidodendron bretonense trees from the Middle Pennsylvanian of the Bernice Basin (Sullivan County, Pennsylvania). Palaeontographica 195B: 153-181
Wnuk C. 1989 Ontogeny and paleoecology of the Middle Pennsylvanian arborescent lycopsid Bothrodendron punctatum, Bothrodendraceae (western middle anthracite field, Shamokin quadrangle, Pennsylvania). American Journal of Botany 76: 966-980[CrossRef][ISI]
Zhao X. X. Wu Q. Gu 1986 Late Devonian flora from southern Ningxia. Acta Palaeontologica Sinica 25: 544-559
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
