Editing Lepidodendron

{{short description|Extinct genus of vascular plants of the Carboniferous to Triassic}}
{{Automatic taxobox
| image = Lepidodendron reconstrucción.jpg
| image_caption = Life reconstruction
| fossil_range = {{fossilrange|Early Carboniferous|Late Permian}}
| taxon = Lepidodendron
| authority = Sternberg, 1820
| subdivision_ranks = [[Species]]
| subdivision = * ''L. aculeatum'' {{small|Sternberg 1820}}
* ''L. batovii'' {{small|Chachlov 1948}}
* ''L. obovatum'' {{small|Sternberg 1820}}
* ''L. whitehillianum''  {{small|Anderson & Anderson 1986}}
| synonyms = *''Dimicheleodendron'' B.A.Thomas & C.J.Cleal
}}

'''''Lepidodendron''''' is an [[extinct]] [[genus]] of primitive [[Lycopodiopsida|lycopodian]] vascular plants belonging the order [[Lepidodendrales]]. It is well preserved and common in the fossil record. Like other Lepidodendrales, species of ''Lepidodendron'' grew as large-tree-like plants in wetland [[coal forest]] environments. They sometimes reached heights of {{convert|50|m|-1|abbr=off}},<ref name=Alekhin/> and the trunks were often over {{cvt|1|m|ftin}} in diameter. They are often known as "scale trees", due to their bark having been covered in diamond shaped leaf-bases, from which leaves grew during earlier stages of growth. However, they are correctly defined as arborescent [[lycophytes]]. They thrived during the [[Carboniferous]] Period (358.9 to 298.9 [[million years ago]]), and persisted until the end of the [[Permian]] around 252 million years ago. Sometimes erroneously called "giant [[club mosses]]", the genus was actually more closely related to modern [[Isoetes|quillworts]] than to modern club mosses. In the [[form classification]] system used in [[paleobotany]], ''Lepidodendron'' is both used for the whole plant as well as specifically the stems and leaves.

== Etymology ==
The name ''Lepidodendron'' comes from the [[Greek language|Greek]] [[wikt:λεπίς|λεπίς]] ''{{transliteration|el|lepis}}'', scale, and [[wikt:δένδρον|δένδρον]] ''dendron'', tree.

== Description and biology ==

=== Overview ===
[[File:Lepidostrobus variabilis 2.jpg|thumb|''Lepidostrobus'', the [[strobilus]] of ''Lepidodendron'' lycophytes|370x370px]]
[[File:Lepidodendrales reconstrucción 02.jpg|left|thumb|Reconstruction of ''Lepidodendron'' (second from left) compared to a juvenile scale tree (far left) and other [[Lepidodendrales]], which from left to right include ''[[Lepidophloios]], [[Synchysidendron]], [[Diaphorodendron]]'' and ''[[Sigillaria]].'']]
''Lepidodendron'' species were comparable in size to modern trees. The plants had tapering trunks as wide as {{cvt|2|m|ft}} at their base that rose to about {{cvt|40|m}}<ref name="Lopatin">
{{cite book
| isbn = 978-5-903825-14-1
| url         = http://www.ras.ru/paleontological_museum/ae617790-a2fb-43c8-a511-1251c0e32004.aspx?hidetoc=0
| title       = Палеонтологический музей имени Ю.А. Орлова (The Orlov Museum of Paleontology)
| publisher   = Moscow: PIN RAN
| date        = 2012
| access-date  = 2020-10-05
| page        = 56
| author      = A. V. Lopatin
}}</ref> and even {{cvt|50|m}},<ref name="Alekhin">
{{cite book
| url         = https://books.google.com/books?id=OUIPAQAAMAAJ&q=лепидодендроны
| title       = Geografiia rastenii s osnovani botaniki (Geography of plants and basics of botany)
| publisher   = Gos. nauchno-pedagog. izd-vo
| date        = 1961
| access-date  = 2020-10-05
| page        = 167
| author      = V. V. Alekhin
}}</ref> arising from an underground system of horizontally spreading branches that were covered with many rootlets. Though the height of the lycopsids make the plants similar to modern trees, the constant [[Glossary of botanical terms#dichotomous|dichotomy]] of branches created a [[Glossary of plant morphology#Plant habit|habit]] that contrasts with that of modern trees. At the ends of branches were oval-shaped [[strobilus|strobili]] called ''Lepidostrobus'' that had a similar shape to modern cones of a [[spruce]] or [[fir]].<ref name="Students">{{cite book |pages= 93–192 |title= Fossil plants: for students of botany and geology |volume= 1 |url= https://www.biodiversitylibrary.org/item/115734 |publisher= Cambridge University Press |author= Seward, Albert Charles |year= 1898 }}</ref>

=== Stem ===
[[File:PSM V18 D629 Lepidodendron modulatum and diplodigioides.jpg|thumb|upright|Leaf scars shown on a ''Lepidodendron''. The "diamond shape" or scale impressions are common indicators of the leaf scars from ''Lepidodendron'' lycophytes.]]
The stem of the lycopsids had a [[Unifacial cambium|unifacial]] [[Vascular cambium|vascular]] cambium, contrasting with the [[Bifacial cambium|bifacial vascular]] cambium of modern trees. Though the bifacial cambium of modern trees produces both secondary [[phloem]] and [[xylem]], the unifacial cambium of ''Lepidodendron'' lycopsid produced only secondary xylem. As the lycopods aged, the wood produced by the unifacial cambium decreased towards the top of the plant such that terminal twigs resembled young ''Lepidodendron'' stems. Compared to modern trees, the stems and branches of the lycopsids contained little wood with the majority of mature stems consisting of a massive [[Cortex (botany)|cortical]] [[meristem]]. The nearly-uniform growth of this cortical tissue indicates no difference in growth during changing seasons, and the absence of dormant [[bud]]s further indicates the lack of [[seasonality]] in ''Lepidodendron'' species.<ref name="Geography" /> The outermost cortex of oldest stems developed into the bark-like [[lycopodiopsid]] [[periderm]].<ref name="Evo">{{cite book |author=Karl J. Niklas |title=The Evolutionary Biology of Plants |publisher=University of Chicago Press |year=1997 |isbn=9780226580838 |edition=illustrated |page=321}}</ref> The bark of the lycopsid was somewhat similar to that of ''[[Picea]]'' species, as [[leaf scar]]s formed peg-like projections that stretched and tore as the bark stretched. To resist the bending force of wind, ''Lepidodendron'' depended on their outer bark rather than their vascular tissues, as compared to modern trees that rely mostly on their central mass of wood.<ref name="Students" />

=== Leaves ===
[[File:Lepidodendron leaf.jpg|thumb|left|Leaf of ''Lepidodendron''|200x200px]]
The leaves of the lycopsid were needle-like and were densely spiraled about young shoots, each possessing only a single [[Leaf vein|vein]]. The leaves were similar to those of a fir in some species and similar to those of ''[[Pinus roxburghii]]'' in others, though in general the leaves of ''Lepidodendron'' species are indistinguishable from those of ''[[Sigillaria]]'' species. The [[decurrent]] leaves formed a cylindrical shell around branches. The leaves were only present on thin and young branches, indicating that, though the lycopsid were evergreen, they did not retain their needles for as long as modern conifers. 
The leaf-cushions were fusiform and elongated, growing at most to a length of {{Cvt|8|cm|in|frac=2}} and a width of {{Cvt|2|cm|in|frac=4}}. The middle of leaf-cushions were smooth, where [[leaf scar]]s were created when an [[abscission]] layer cut a leaf from its base. Each leaf scar was composed of a central circular or triangular scar and two lateral scars that were smaller and oval-shaped. This central scar marks where the main [[vascular bundle]] of the leaf connected to the vascular system of the stem. This xylem bundle was composed only of primary [[Vessel element|trachea]].{{Citation needed|date=January 2024|reason=trachea instead of tracheids in lycophytes?}} The two outer scars mark the forked branches of a strand of vascular tissue that passed from the [[Cortex (botany)|cortex]] of the stem into the leaf. This forked strand is sometimes referred to as the "parichnos". Surrounding this strand were [[parenchyma]] cells and occasionally thick-walled elements. Surrounding both conducting tissues was a broad sheath of transfusion [[tracheid]]s. Below the leaf scar the leaf-cushion tapered to a basal position. In this tapering area, circular impressions with fine pits were present. These impressions were continuous with the parichnos scars near the top of the tapering portion. This is because the impressions are formed by [[aerenchyma]] tissue that developed in closely with the parichnos. Above the leaf scar was a deep triangular impression known as the "ligular pit" for its similarities to the [[ligule]] of ''[[Isoetes]]''. In some leaf-cushions a second depression was present above the ligular pit. Though its purpose is unclear, it has been suggested that the depression may mark the position of a [[sporangium]]. As the branch of a ''Lepidodendron'' lycopsid grew the leaf-cushion only grew to a certain extent, past which the leaf-cushion stretched. This stretching widened the groove that separated the leaf-cushions, creating a broad, flat channel.<ref name=Students/>

=== Underground Structures ===
The underground structures of ''Lepidodendron'' and similar lycopsid species known from the fossil record including ''[[Sigillaria]]'' are assigned to the form taxon, ''[[Stigmaria]]''. The rootlets were dichotomously branched from the [[rhizomes]] similar to ''Isoetes''. These rhizomorphic axes were shoot-like, and dichotomous branching of the rootlets structured the stigmarian systems. Rootlet scars can be seen from ''Stigmaria'' fossils where the root hairs used to be attached.<ref name="Hetherington">{{cite journal |last1=Hetherington |first1=A.J. |last2=Berry |first2=C.M. |last3=Dolan |first3=Liam |title=Networks of highly branched stigmarian rootlets developed on the first giant trees |journal=PNAS |date=2016 |volume=113 |issue=24| pages=6695–6700 |doi=10.1073/pnas.1514427113|doi-access=free |pmid=27226309 |pmc=4914198 |bibcode=2016PNAS..113.6695H }}</ref> [[Hypha]]e are occasionally present in the tissues of ''Lepidodendron'' lycopsids, indicating the presence of [[mycorrhiza]]l associations.<ref>{{cite journal |last1=Strullu-Derrien |first1=Christine |last2=Strullu |first2=Désiré-Georges |title=Mycorrhization of fossil and living plants |journal=Comptes Rendus Palevol |date=November 2007 |volume=6 |issue=6–7 |pages=483–494 |doi=10.1016/j.crpv.2007.09.006|bibcode=2007CRPal...6..483S }}</ref>

=== Decay ===
[[File:Estonian Museum of Natural History Specimen No 193541 photo (g23 g23-26 1 jpg).jpg|thumb|''Lepidodendron sp.'' bark from the [[Estonian Museum of Natural History]].|213x213px]]
Different [[fossil]] genera have been described to name the various levels of decay in ''Lepidodendron'' bark fossils. The name ''Bergeria'' describes stems that have lost their epidermises, ''Aspidiariu'' is used when cushions have been removed by deep decay, and ''Knorria'' is used when the leaf cushions and the majority of cortical tissues has decayed, with a shallow "fluted" surface remaining. However, it has been suggested that these are more likely growth forms than preserved bark types, as entire fossilized trunks have been discovered with dissimilar forms; if decay is assumed to be constant throughout the trunk, then different forms indicate growth rather than levels of decay. It is likely that the trunk of ''Lepidodendron'' lycopsids were subject to the growth forms ''Knorria'', ''Aspidiaria'', and ''Bergeria'' progressing up the trunk, respectively.<ref>{{cite journal |title= A rediscovered 114-foot Lepidodendron from Bolton, Lancashire |author= Thomas, B.A. and Watson, Joan |journal= Geological Journal |volume= 11 |number= 1 |pages= 15–20 |year= 1976 |publisher= Wiley Online Library |doi= 10.1002/gj.3350110102 |bibcode= 1976GeolJ..11...15T }}</ref>

==Growth and reproduction==
[[File:Lepidodendron joven reconstrucción.jpg|left|thumb|upright|Reconstruction of a juvenile ''Lepidodendron'', showing the unbranched trunk with leaves]]
During the early stages of growth, ''Lepidodendron'' grew as single, unbranched trunk, with leaves growing out of the scale leaf bases (cushions). Towards the end of the lycopod growth, the leaves on the lower part of the trunk were shed, and in ''Lepidodendron'', the upper part of the trunk [[Glossary of botanical terms#dichotomous|dichotomously]] branched into a [[Crown (botany)|crown]].<ref name=":02" /> The rate of growth of arborescent lycophytes is disputed, some authors contended that they had a rapid life cycle, growing to their maximum size and dying in only 10 to 15 years, while other authors argue that these growth rates were overestimated.<ref name=":02">{{Cite journal |last1=Thomas |first1=Barry A. |last2=Cleal |first2=Christopher J. |date=May 2018 |title=Arborescent lycophyte growth in the late Carboniferous coal swamps |journal=New Phytologist |language=en |volume=218 |issue=3 |pages=885–890 |doi=10.1111/nph.14903 |pmid=29282734|doi-access=free }}</ref> Rather than reproduce with seeds, ''Lepidodendron'' lycopsids reproduced with spores. The spores were stored in [[sporangia]] situated on fertile stems that grew on or near the main trunk. The fertile stems grew together in cone-like structures that clustered at the tips of branches.<ref>{{cite book |title= Geology of Michigan |author= John Adam Dorr, Donald F. Eschman |edition= illustrated |publisher= University of Michigan Press |year= 1970 |isbn= 9780472082803 |page= 429}}</ref>

==Distribution==
The lack of [[growth rings]] and dormant buds indicates no seasonal growth patterns, and modern plants with similar characteristics tend to grow in [[tropical]] conditions. However, ''Lepidodendron'' species were distributed throughout [[subtropical]] regions. The lycopsid inhabited an extensive area compared to tropical flora of the same time period, with lycopods growing as far north as [[Spitsbergen]] and as far south as [[South America]], in a [[latitudinal]] range of 120°.<ref name=Geography>{{cite book |title= An introduction to historical plant geography |url= https://www.biodiversitylibrary.org/item/28244 |publisher= Chronica Botanica Company |author= Vulf, Evgenii Vladimirovich and Brissenden, Elizabeth |year= 1943 |pages= 176–177}}</ref>

== Extinction ==
In [[Euramerica]], ''Lepidodendron'' became extinct at the end of the Carboniferous,<ref name=":0">{{Cite journal |last1=Feng |first1=Ru |last2=D’Rozario |first2=Ashalata |last3=Zhang |first3=Jian-Wei |date=December 2019 |title=A new Bergeria (Flemingitaceae) from the Mississippian of Xinjiang, NW China and its evolutionary implications |journal=Journal of Palaeogeography |language=en |volume=8 |issue=1 |page=4 |doi=10.1186/s42501-018-0020-4 |issn=2524-4507|doi-access=free |bibcode=2019JPalG...8....4F }}</ref> as part of a broader pattern of ecological change, including the increasing dominance of [[seed plant]]s in lowland wetland forests, and increasingly arid-adapted vegetation across western Pangea.<ref>{{Cite journal |last1=Lucas |first1=Spencer G. |last2=DiMichele |first2=William A. |last3=Opluštil |first3=Stanislav |last4=Wang |first4=Xiangdong |date=2023-06-14 |title=An introduction to ice ages, climate dynamics and biotic events: the Late Pennsylvanian world |url=https://www.lyellcollection.org/doi/10.1144/SP535-2022-334 |journal=Geological Society, London, Special Publications |language=en |volume=535 |issue=1 |pages=1–15 |doi=10.1144/SP535-2022-334 |bibcode=2023GSLSP.535..334L |issn=0305-8719|url-access=subscription }}</ref> However, in the [[Cathaysia]] region comprising what is now China, wet tropical environmental conditions continued to prevail, with ''Lepidodendron'' (in its broad sense) only becoming extinct around the end of the Permian, around 252 million years ago, as a result of the extreme environmental disturbance caused by the [[Permian-Triassic extinction event]].<ref name=":0" /><ref>{{Cite journal |last1=Xu |first1=Zhen |last2=Hilton |first2=Jason |last3=Yu |first3=Jianxin |last4=Wignall |first4=Paul B. |last5=Yin |first5=Hongfu |last6=Xue |first6=Qing |last7=Ran |first7=Weiju |last8=Li |first8=Hui |last9=Shen |first9=Jun |last10=Meng |first10=Fansong |date=September 2022 |title=End Permian to Middle Triassic plant species richness and abundance patterns in South China: Coevolution of plants and the environment through the Permian–Triassic transition |url=https://linkinghub.elsevier.com/retrieve/pii/S0012825222002203 |journal=Earth-Science Reviews |language=en |volume=232 |pages=104136 |doi=10.1016/j.earscirev.2022.104136|bibcode=2022ESRv..23204136X }}</ref>

== Gallery ==
<gallery widths="180" heights="180">
File:Lepidodendron sp. (fossil lycopod) (lower Pottsville Group, Lower Pennsylvanian; Irish Ridge East roadcut, near Trinway, Ohio, USA) 2 (32394265633).jpg|''Lepidodendron sp.'' bark from the [[Pottsville Group]], Lower Pennsylvanian
File:Lepidodendron elegans.JPG|''Lepidodendron elegans''
File:Lepidodendron aculeatum.jpg|''Lepidodendron aculeatum''
File:Lepidodendron lycopodioides.jpg|''Lepidodendron lycopodioides''
File:PSM V18 D630 Restoration of a lepidodendron.jpg|Restoration of ''Lepidodendron'' with leafy branches
File:Joggins Lepidodendron bark imprint.jpg|''Lepidodendron'' bark from [[Joggins]], Nova Scotia, Canada
File:Fossil Tree Stumps at Fossil Grove Glasgow 1977.jpg|''Lepidodendron'' fossil stumps from [[Fossil Grove]], Glasgow, Scotland
File:Lepidodendron sp. - Impressão do caule MN 01.jpg|''Lepidodendron sp.'' stem impression displayed at a collection held in the [[National Museum of Brazil]]
File:Description of the coal flora of the Carboniferous formation in Pennsylvania and throughout the United States (Plate LXIII) (21489161993).jpg|Various ''Lepidodendron'' diagrams from the Geological Survey of [[Pennsylvania]]
File:LepidodendronOhio.jpg|External mold of ''Lepidodendron'' from the [[Upper Carboniferous]] of [[Ohio]].
File:Stigmaria Heimans.jpg|1911 reconstruction of a mature ''Lepidodendron'', showing dichotomous branching at the top of the trunk
File:Lepidodendron PAMuseum.jpg|Trunk fragment, showing leaf base scars
</gallery>
== See also ==
* ''[[Archaeopteris]]''
* ''[[Carboniferous]]''
* [[Evolutionary history of plants]]
* [[Fossil Grove]]
* ''[[Glossopteris]]''
* ''[[Lepidodendrales]]''
* ''[[Lycophytes]]''
* ''[[Lycopsid]]''
* ''[[Stigmaria]]''
* ''[[Sigillaria]]''

== References ==
{{Reflist}}

== Further reading ==
{{Commons category|Lepidodendron}}
* {{cite book |title=Fossil Plants |last=Davis |first=Paul |author2=Kenrick, Paul |year=2004 |publisher=Smithsonian Books |location=Washington, DC |isbn=1-58834-181-X }}
* {{cite book |title=A Natural History of Ferns |last=Morran |first=Robin C. |year=2004 |publisher=Timber Press |location=Portland |isbn=0-88192-667-1 }}
* "Plant fossils of the British Coal Measures" by Christopher J.Cleal and Barry A.Thomas, publ. The Palaeontological Association, London, 1994, 222 pages, {{ISBN|0-901702-53-6}}
* J. M. Anderson and H. M. Anderson. 1985. Palaeoflora of Southern Africa. Prodromus of South African Megafloras Devonian to Lower Cretaceous 1-423

{{Taxonbar|from=Q576530}}

[[Category:Prehistoric lycophytes]]
[[Category:Prehistoric trees]]
[[Category:Pennsylvanian plants]]
[[Category:Carboniferous life of North America]]
[[Category:Fossils of Georgia (U.S. state)]]
[[Category:Paleozoic life of New Brunswick]]
[[Category:Paleozoic life of Newfoundland and Labrador]]
[[Category:Paleozoic life of the Northwest Territories]]
[[Category:Paleozoic life of Nova Scotia]]
[[Category:Paleozoic life of Nunavut]]
[[Category:Paleozoic life of Quebec]]
[[Category:Permian Africa]]
[[Category:Fossils of South Africa]]
[[Category:Paleozoic life of Oceania]]
[[Category:Permian life of Australia]]
[[Category:Fossils of Australia]]
[[Category:Paleozoic life of Asia]]
[[Category:Permian China]]
[[Category:Fossils of China]]
[[Category:Fossils of Indonesia]]
[[Category:Fossils of North Korea]]
[[Category:Fossils of Oman]]
[[Category:Fossils of South Korea]]
[[Category:Paleozoic life of Europe]]
[[Category:Fossils of Italy]]
[[Category:Fossil taxa described in 1820]]
[[Category:Prehistoric lycophyte genera]]