Lower Devonian Plant Research Articles

Revisiting the Rebreuve plant assemblage from the Lower Devonian of Artois, northern France

ABSTRACT French Lower Devonian floras are rare, especially compared to certain other Western European countries. In this study, we reassess an assemblage collected in the 1930s in the Rebreuve quarry (Pas-de-Calais, northern France). We describe new features in several taxa and update taxonomic names from original descriptions. For instance, re-examination of vegetative remains previously described as Psilophyton princeps, led to the discovery of fertile structures allowing us to refer these specimens to Sawdonia. In total, this flora consists of 10 taxa, including up to four different Psilophyton species, such as P. parvulum. Other taxa include Danziella artesiana, Drepanophycus cf. spinaeformis, Sporogonites exuberans and some specimens of Taeniocrada and Sciadophyton, revealing a diverse Lower Devonian plant assemblage. The Rebreuve assemblage represents a typical Emsian flora from Laurussia and bears striking resemblance with coeval Belgian assemblages. Previous palynological investigations, in addition to the similarities with well-dated Belgian floras, suggest an early Emsian age for this assemblage. The paleogeographical implications of findings are discussed.

New insights into the South China Lower Devonian flora based on fossils from Hezhang, Guizhou Province.

The Early Devonian flora of South China is composed of many endemic members and has been studied mainly based on Yunnan materials. We in this study report a new Lower Devonian plant locality, recognize four sub-regions of the Early Devonian flora from South China and furthermore demonstrate these plants' distribution pattern and probable dispersal route. The new finds of plant fossils are from the Lower Devonian of Hezhang County, Guizhou Province, and include Zosterophyllopsida Demersatheca and Euphyllophytopsida Pauthecophyton. Demersatheca contigua, consisting of cylindrical strobili with four longitudinal rows of sporangia decussately arranged, shows great similarities to the plant from Yunnan and Guangxi localities. Pauthecophyton hezhangensis sp. nov. has distinct fertile units with grouped sporangia and each unit with two or three fusiform sporangia. The new locality belongs to the Guizhou sub-region and shares some taxa with the eastern Yunnan and Cathaysia sub-regional floras within South China, in which the shared plant members are distributed around the epicontinental sea. We suggest that the Guizhou sub-region might act as a bridge during plant dispersal from eastern Yunnan to Cathaysia Oldland in the Early Devonian. This article is part of the theme issue 'The impact of Chinese palaeontology on evolutionary research'.

Earliest record of transfer cells in Lower Devonian plants.

Key sources of information on the nature of early terrestrial ecosystems are the fossilized remains of plants and associated organic encrustations, which are interpreted as either biofilms, biological soil crusts or lichens. The hypothesis that some of these encrustations might be the remains of the thalloid gametophytes of embryophytes provided the stimulus for this investigation. Fossils preserved in charcoal were extracted from Devonian Period (Lochkovian Stage, c. 410-419 Myr old) sediments at a geological site in Shropshire (UK). Scanning electron micrographs (SEMs) of the fossils were compared with new and published SEMs of extant bryophytes and tracheophytes, respectively. One specimen was further prepared and imaged by transmission electron microscopy. Fossils of thalloid morphology were composed almost entirely of cells with labyrinthine ingrowths; these also were present in fossils of axial morphology where they were associated with putative food-conducting cells. Comparison with modern embryophytes demonstrates that these distinctive cells are transfer cells (TCs). Our fossils provide by far the earliest geological evidence of TCs. They also show that some organic encrustations are the remains of thalloid land plants and that these are possibly part of the life cycle of a newly recognized group of plants called the eophytes.

Discovery of Lower Devonian plants from Jiangxi, South China and the pattern of Devonian transgression after the Kwangsian Orogeny in the Cathaysia Block

The Kwangsian Orogeny is a major geological event in the Paleozoic of South China and has been debated with data of lithofacies, biofacies, palaeogeography and geodynamics. However, the transgression after the Kwangsian Orogeny has been less concerned. In this study, Early Devonian plants, including a basal euphyllophyte plant attributed to Pauthecophyton sp., are discovered for the first time from the Yangling Psephyte, Chongyi, Jiangxi Province, China, which palaeogeographically belongs to the Cathaysia Block of the South China Plate. Based on the presence of these plant fossils, the Yangling Psephyte is dated as Pragian (Early Devonian). Combined with 23 horizons and 52 Devonian plant fossil localities in southern China reported in previous studies, the transgression and deposition pattern after the Kwangsian Orogeny is recognized. It is indicated that in the Cathaysia Block the transgression and deposition after the Kwangsian Orogeny was stepwise, started not later than the Pragian Stage, continued until at least the Late Devonian and gradually strengthened northeastwards from the Early Devonian to the Late Devonian.

New Plants from the Lower Devonian Pingyipu Group, Jiangyou County, Sichuan Province, China.

Descriptions of Lower Devonian plants from Yunnan, South China, have revolutionized concepts of diversity and disparity in tracheophytes soon after they became established on land. Sichuan assemblages have received little attention since their discovery almost 25 years ago and require revision. With this objective, fieldwork involving detailed logging and collection of fossils was undertaken in the Longmenshan Mountain Region, Jiangyou County and yielded the two new taxa described here. They are preserved as coalified compressions and impressions that allowed morphological but not anatomical analyses. Yanmenia (Zosterophyllum) longa comb nov is based on numerous rarely branching shoots with enations resembling lycophyte microphylls, without evidence for vasculature. The presence of sporangia is equivocal making assignation to the Lycopsida conjectural. The plant was recently described as a zosterophyll, but lacks strobili. These are present in the second plant and comprise bivalved sporangia. The strobili terminate aerial stems which arise from a basal axial complex displaying diversity in branching including H- and K- forms. These features characterise the Zosterophyllopsida, although the plant differs from Zosterophyllum in valve shape. Comparisons indicate greatest similarities to the Lower Devonian Guangnania cuneata, from Yunnan, but differences, particularly in the nature of the sporangium border, require the erection of a new species, G. minor. Superficial examination of specimens already published indicate a high degree of endemism at both species and generic level, while this study shows that Yanmenia is confined to Sichuan and Guangnania is one of the very few genera shared with Yunnan, where assemblages also show a high proportion of further endemic genera. Such provincialism noted in the Chinese Lower Devonian is explained by the palaeogeographic isolation of the South China plate, but this cannot account for differences/endemism between the Sichuan and Yunnan floras. Such an enigma demands further integrated geological, palaeobotanical and palynological studies.

Lower Devonian plant and spore assemblages from Lower Old Red Sandstone strata of Tredomen Quarry, South Wales

Tredomen Quarry, near Brecon, South Wales, is regarded as a Lower Old Red Sandstone terrestrial lagerstätten and has yielded a palaeobotanical assemblage that illustrates the diversity and possible affinities of early vegetation across the Anglo–Welsh Basin during the lower Lochkovian (Early Devonian). Two boreholes were drilled at the site and subsequent logging resolved the stratigraphic position of the quarry to 64 m above the Bishop's Frome Limestone, thus the lower part of the St. Maughans Formation, a level which few other Anglo–Welsh Basin outcrops expose. A palynological assemblage from the quarry surface is assigned to the lower micrornatus-newportensis Sub-biozone of the lower Lochkovian. The assemblage is diverse, a notable characteristic being ornamented hilate cryptospores of which new species and varieties of Cymbohilates are described ( Cymbohilates horridus var. A, Cymbohilates cymosus var. A–C, Cymbohilates? sp. A–D). Large rhyniophytes and rhyniophytoids including Cooksonia, Salopella and Tarrantia comprise one component of the palaeobotanical assemblage, typical of southern Britain during the Lochkovian. A diverse group of minute axial plants (mesofossils) constitute a second component, rarely found in other assemblages and considered to be synonymous with the exceptionally well-preserved, charcoalified minute sporangia discovered from a mid-Lochkovian locality. Here they provide for the first time evidence that these minute plants were highly branched and are considered to be stem-group embryophytes with both tracheophytic and bryophytic characters, hence a separate component of vegetation living alongside the rhyniophytes and rhyniophytoids. Non-embryophytes form the third component of vegetation and include Nematasketum/Prototaxites and Pachytheca. Minute coalified banded tubes are observed intertwined across bedding planes and are interpreted as hyphae that may have derived from these non-embryophytes.

The invasion of the land by plants: when and where?

The invasion of the land by plants: when and where?

The early land plants from the Armorican Massif: sedimentological and palynological considerations on age and environment

AbstractThe Châteaupanne Unit belongs to the South Armorican domain of the Armorican Massif (France), which is part of the Variscan belt. This unit includes two Lower Devonian plant levels and one of them corresponds to the Basal Member of the Chalonnes Formation. A sedimentological and palaeontological analysis of these fossiliferous deposits from the Châteaupanne quarry (Montjean/Loire, Maine et Loire, France) is presented here for the first time. The age determination based on palynology indicates that the locality records the earliest occurrence of plant megafossils in the Armorican Massif. Their presence suggests an emergence event that has never been described before. Our study highlights the promising potential of the Basal Member of the Chalonnes Formation to aid in understanding these occurrences, and provides new insights into the history of the Variscan belt.

Danziella artesiana, a new name for Zosterophyllum artesianum from the Lower Devonian of Artois, northern France

A reinvestigation of the Lower Devonian plant, Zosterophyllum artesianum Danzé-Corsin 1956, based on original collections and undescribed material leads to the erection of a new taxon, Danziella artesiana. The genus shares with Zosterophyllum smooth axes with lateral stalked sporangia comprising two equal valves, but in the French plant the stalks, attached at right angles to the fertile axes, are long and straight. Distal dehiscence occurs in the same plane of compression as the subtending axis. Sporangia are attached at irregular intervals and there is no well-defined spike. Anatomical evidence that would confirm affinity with the Zosterophyllales is lacking in these compression fossils. Consideration is also given to its relationship to taxa such as Renalia Gensel that appear to share characters with zosterophylls and rhyniophytes, with consensus that a basal position in the former seems more likely. However the age of the fossils, (Pragian–Emsian), based indirectly on spores, fish and field relationships, postdates that of the major radiation of zosterophylls elsewhere on the Old Red Sandstone Continent.

Silurian and Lower Devonian plant assemblages from the Anglo‐Welsh Basin: a palaeobotanical and palynological synthesis

AbstractA comprehensive survey of plant assemblages from Upper Silurian (Gorstian–Přídolí) and Lower Devonian (Lochkovian–Pragian) localities in South Wales and the Welsh Borderland is presented, together with some comments on recent improvements in dating and correlation. Spore assemblages provide a stratigraphic framework for plant evolutionary studies and, along with microvertebrates, enable correlation from continental to marine rocks, i.e. near‐shore to shelf deposits. While it is recognized that the assemblages provide the most complete and extensive record of the history of vascular plants in a restricted geographical area during the time interval, it seems likely that major evolutionary innovation occurred elsewhere. The plants themselves display a number of types of fossilization. Particularly important are the pyrite permineralizations which have helped in the elucidation of the ultrastructure of tracheids in early vascular plants. Minute, coalified, relatively uncompressed fossils (mesofossils) from the Přídolí Lochkovian of the Welsh Borderland are hypothesized to be the products of wildfire, the earliest records to date. In addition to displaying often exquisite anatomical detail, the sporangia contain spores which have been linked to those in dispersed assemblages. Such relationships are helpful in the reconstruction of local and regional vegetation, even in the absence of meso‐ and megafossils. However, because these fossils are allochthonous and preserved in fluvial sediments, the habitats of the plants remain uncertain. A new hypothesis suggests that interfluvial areas, where calcretes are interpreted as relicts of vertisols and a seasonally dry climate, provided refugia in the Lower Devonian for the cryptospore‐producing plants which dominated Ordovician and Lower Silurian land vegetation, while vascular plants colonized areas in the immediate vicinity of rivers. Variation in regional vegetation is explored via comparisons of composition of spore assemblages in southern Britain and Scotland and timing of appearances of derived taxa, integrated with limited information on the spore producers. Copyright © 2004 John Wiley & Sons, Ltd.

Morphology and wall ultrastructure of the spores of the Lower Devonian plant Oocampsa catheta Andrews et al., 1975

The enigmatic Lower Devonian plant Oocampsa catheta Andrews et al. (Can. J. Bot. 53 (1975) 1719) is considered intermediate between the trimerophytes and progymnosperms. In order to shed light on its evolutionary relationships, the morphology and ultrastructure of its sporangium and spores were analysed using light, scanning electron and transmission electron microscopy. In addition, dispersed spores ( Grandispora douglastownense McGregor (Palaeontographica B 142 (1973) 1) and Grandispora ?macrotuberculata (Trudy VNIGNI 37 (1963) 18) McGregor (Palaeontographica B 142 (1973) 1), considered to possibly represent forms derived from O. catheta, were also examined. It is concluded that G. douglastownense and G. ?macrotuberculata are probably end members of the same spore complex and most likely are dispersed spores produced by O. catheta. Oocampsa catheta spores are bilayered. An inner body has an innermost part consisting of continuous, parallel-stacked, laminae and an outermost part consisting of more erratic, anastomosing, laminae. The inner body is surrounded by an homogeneous outer layer that is extended at the equator forming a pseudozona, and is folded on the proximal surface forming the trilete mark and on the distal surface forming spinose ornament. The spores are partially camerate. On the inside of the sporangium wall there is a layer probably representing the residue left following degeneration of a (probably secretory) tapetum. Spore morphology, gross structure and wall ultrastructure are compared to that of extant and fossil plant groups, and it is concluded that the spores of O. catheta are highly distinctive and do not conform closely to any plant group, although they show most in common with the spores of the progymnosperms.

Novel conducting tissues in Lower Devonian plants

Elongate cells presumed to comprise water-conducting tissues are described from the central regions of short lengths of two naked, stomatiferous, coalified, axial fossils from Lochkovian (Lower Devonian) fluvial rocks in the Welsh Borderland. In one, a discrete central strand is predominantly composed of uniformly thickened cells that are compared with central tissues in coeval plants, e.g. Aglaophyton, and the hydroids of extant mosses. The other has at least two types of cells with pits of plasmodesmata dimensions that perforate only the inner layer of a bilayered wall. These are compared with liverwort and Takakia hydroids and the coeval S-type tracheids that characterize the Rhyniopsida. The affinities of the two axes remain equivocal. The relevance of plasmodesmata-derived pits to the evolution of diversity in water-conducting elements in early embryophytes is discussed.

Novel conducting tissues in Lower Devonian plants

Elongate cells presumed to comprise water-conducting tissues are described from the central regions of short lengths of two naked, stomatiferous, coalified, axial fossils from Lochkovian (Lower Devonian) fluvial rocks in the Welsh Borderland. In one, a discrete central strand is predominantly composed of uniformly thickened cells that are compared with central tissues in coeval plants, e.g. Aglaophyton, and the hydroids of extant mosses. The other has at least two types of cells with pits of plasmodesmata dimensions that perforate only the inner layer of a bilayered wall. These are compared with liverwort and Takakia hydroids and the coeval S-type tracheids that characterize the Rhyniopsida. The affinities of the two axes remain equivocal. The relevance of plasmodesmata-derived pits to the evolution of diversity in water-conducting elements in early cmbryophytes is discussed.

The role of mid-palaeozoic mesofossils in the detection of early bryophytes.

Recently discovered Silurian and Devonian coalified mesofossils provide an additional source of data on early embryophytes. Those reviewed in this paper are considered of some relevance to understanding the early history of bryophytes while highlighting the difficulties of recognizing bryophytes in often very fragmentary fossils. The first group comprises sporophytes in which terminal sporangia contain permanent dyads and tetrads. Such spores (cryptospores) are similar to those found dispersed in older Ordovician and Silurian strata, when they are considered evidence for a land vegetation of embryophytes at a bryophyte grade. The phylogenetic significance of plants, where the axes associated with both dyad- and tetrad-containing sporangia are branching, a character state not found in extant bryophytes, is discussed. The second group comprises axial fossils, many with occasional stomata, in which central conducting strands include G-type tracheids and a number of novel types of elongate elements not readily compared with those of any tracheophyte. They include smooth-walled, evenly thickened elongate elements as well as those with numerous branching +/- anastomosing projections into the lumen. Some of the latter bear an additional microporate layer, but the homogenized lateral walls between adjacent cells are never perforate. Such cells, which occur in various combinations in central strands, are compared with the leptoids and hydroids of mosses, hydroids of liverworts and presumed water-conducting cells in coeval Lower Devonian plants such as Aglaophyton. It is concluded that lack of information on the chemistry of their walls hampers sensible assessment of their functions and the affinities of the plants. Finally, a minute fossil, comprising an elongate sporangium in which a central cylindrical cavity containing spores and possible elaters terminates in a complex poral dehiscence apparatus, is used to exemplify problems of identifying early bryophytes. It is concluded that further progress necessitates the discovery of pre-Upper Silurian fossils with well-preserved anatomy, as well as a re-evaluation of criteria used to assess existing and new Devonian fossils for bryophyte affinity.

99/00996 Solid state 13C NMR and high temperature 1H NMR determination of bulk structural properties for mesophase-containing semi-cokes prepared from coal tar pitch : Andresen, J. M. et al. Carbon, 1998, 36, (7–8), 1043–1050

The coalified remains of three extinct nonvascular Lower Devonian plants (Prototaxites Dawson, Pachytheca Hooker, and Parka Fleming) have been analysed using flash pyrolysis-gas chromatography-mass spectrometry, FTIR, and 13C solid-state NMR. The affinities of these fossils are unknown and their habitats remain conjectural. Host rock lithology and grain size correlate with the state of morphological and chemical preservation of Prototaxites. The flash pyrolysates of well-preserved Prototaxites and Pachytheca were dominated by aromatic hydrocarbons and alkylphenols. Given their resistance to compression when compared with associated lignified vascular plant fossils, it is possible that Prototaxites and Pachytheca contained an extinct polyphenolic structural biomacromolecule that was a failed experiment during terrestrialization. Precise affinities for the enigmatic fossils Prototaxites, Pachytheca, and Parka are still to be confirmed, although Prototaxites and Pachytheca are chemically distinct from Parka.

Molecular characterization of some enigmatic Lower Devonian fossils

The coalified remains of three extinct nonvascular Lower Devonian plants ( Prototaxites Dawson, Pachytheca Hooker, and Parka Fleming) have been analysed using flash pyrolysis-gas chromatography-mass spectrometry, FTIR, and 13C solid-state NMR. The affinities of these fossils are unknown and their habitats remain conjectural. Host rock lithology and grain size correlate with the state of morphological and chemical preservation of Prototaxites. The flash pyrolysates of well-preserved Prototaxites and Pachytheca were dominated by aromatic hydrocarbons and alkylphenols. Given their resistance to compression when compared with associated lignified vascular plant fossils, it is possible that Prototaxites and Pachytheca contained an extinct polyphenolic structural biomacromolecule that was a failed experiment during terrestrialization. Precise affinities for the enigmatic fossils Prototaxites, Pachytheca, and Parka are still to be confirmed, although Prototaxites and Pachytheca are chemically distinct from Parka.

98/01060 Determination of gasoline properties using 1H-NMR spectroscopy : Hutter, M. et al. Pet. Coal, 1995, 37, (3), 50–52

The coalified remains of three extinct nonvascular Lower Devonian plants (Prototaxites Dawson, Pachytheca Hooker, and Parka Fleming) have been analysed using flash pyrolysis-gas chromatography-mass spectrometry, FTIR, and 13C solid-state NMR. The affinities of these fossils are unknown and their habitats remain conjectural. Host rock lithology and grain size correlate with the state of morphological and chemical preservation of Prototaxites. The flash pyrolysates of well-preserved Prototaxites and Pachytheca were dominated by aromatic hydrocarbons and alkylphenols. Given their resistance to compression when compared with associated lignified vascular plant fossils, it is possible that Prototaxites and Pachytheca contained an extinct polyphenolic structural biomacromolecule that was a failed experiment during terrestrialization. Precise affinities for the enigmatic fossils Prototaxites, Pachytheca, and Parka are still to be confirmed, although Prototaxites and Pachytheca are chemically distinct from Parka.

Chemical characterization of Lower Devonian vascular plants

Vegetative remains of three coalified Lower Devonian vascular plants ( Zosterophyllum, Psilophyton, Renalia) were analyzed using flash pyrolysis-gas chromatography-mass spectrometry. The distributions of pyrolysis products are compared with those from younger vascular plant fossil xylem ( Cordaixylon, Callixylon) and cuticle ( Pachypteris). The likelihood of the chemical preservation of characteristic higher plant macromolecules (e.g., lignin and cutan) in the Lower Devonian plant fossils is considered in light of this comparison and associated thermal maturity assessments. Reflectance values from vitrinite-like macerals, which may not be vitrinite sensu stricto in the Lower Devonian host rocks for the fossils selected for this study, are shown to provide a reasonable assessment of the thermal maturity of these early vascular plant fossils. Although lignin altered through burial maturation is the most likely source of the prominent alkylphenols and aromatic hydrocarbons in the Lower Devonian tracheophyte flash pyrolysates, a contribution from thermally modified tannins cannot be ruled out. Comparison of the highly aliphatic pyrolysates from the Zosterophyllum and Psilophyton axes with that of a thermally mature fossil gymnosperm leaf revealed that cutan was an important component in the Devonian plant remains. This is the earliest chemical evidence for the presence of cutan in vascular plants.

A New Genus and Species, Celatheca beckii, from the Siegenian (Early Devonian) of Southeastern Yunnan, China

A new genus and species, Celatheca beckii, is described from the Early Devonian (Siegenian) Posongchong Formation, Wenshan district of southern Yunnan, China. The plants consist of anisodichotomously divided vegetative or fertile axes. Divisions of the main axes produce irregularly to helically arranged lateral branch systems; vegetative ones are two to three times divided, and each unit ends in strongly recurved tips. Fertile lateral branches divide one to two times basally, and after a distance of 0.3-1.7 cm divide again twice closely and cruciately. Each of the four resulting segments consists of two parts, an inner elongate-oval sporangium and an outer adjacent leaflike appendage. The lobed distal ends of the leaflike appendages fold inward to enclose the sporangia so that the whole fertile structure appears coherent. Superficially the fertile structures resemble a synangium, but close examination shows the sporangium/appendage units are discrete structures joined only at the juncture of their stalks with the fertile axis. Comparison to the similar-appearing, presumed synangiate Yarravia shows the Chinese fossils to differ in having a smaller number of discrete sporangia and in the presence of the leaflike appendages forming a cupule-like covering. The sporangium/appendage organization is similar to that of some early cupulate ovules but probably is not homologous. This discovery further enriches the composition and diversity of the Posongchong flora and demonstrates another plant in which sporangia are protected by a modified vegetative structure. Its similarity to Australian Lower Devonian plants is discussed in view of current evidence of paleocontinental positions and early land plant biogeography.

Depositional environment and preservation of biota in the Lower Devonian hot-springs of Rhynie, Aberdeenshire, Scotland

ABSTRACTThe Lower Devonian plant- and arthropod-bearing cherts of the Rhynie area of Aberdeenshire, NE Scotland, were deposited from silica-rich waters emanating from the hot-springs of a precious-metal (Au) bearing epithermal system. Cherts were deposited at temperatures up to 100°C. The hot-springs were active in the waning phase of local volcanism and reworked volcanic debris is associated with the hot-spring system. Plant and animal communities inhabited a low energy alluvial plain with small ponds. Hot-springs deposited surficial sinter and silicified standing plants and underlying plant litter in a generally terrestrial setting, but aquatic organisms were present in low temperature pools within areas of sinter deposition. Silicification also affected plants and sediment in the shallow subsurface. The cherts display massive, vuggy, laminated, lenticular, nodular and brecciated textures in laterally impersistent beds. Faunal and floral variation between beds is of local significance, possibly reflecting general water availability. Variations in preservation of plants reflect not only degrees of imperfection in the permineralisation process, but also silicification at different times in the cycle of plant growth and decay.