Jean Galtier

Distribution of anatomically-preserved floras in the Lower Carboniferous in Western Europe

Twelve localities of Lower Carboniferous strata in Scotland (Loch Humphrey Burn, Glenarbuck, Pettycur, Oxroad Bay and the Berwickshire localities of Cove, Burnmouth, Gavinton, Edrom, Foulden) and in France (Esnost, Roannais, Montagne Noire) have been investigated with particular regard to their anatomically preserved floras. New data on the composition and preservation of the assemblages, their geological setting and stratigraphical age, using palynology in particular, are presented. Present data suggest that four successive groups of floras obtained from these localities can be recognised: from the Montagne Noire (mid to late Tournaisian), from the Berwickshire localities and Oxroad Bay (late Tournaisian to early Visean), from Loch Humphrey Burn and possibly Glenarbuck (mid Visean) and from Roannais, Esnost, and Pettycur (late Visean). The similarities and differences between the floras are discussed with particular emphasis on stratigraphical as opposed to ecological controls. Comparisons are made with the New Albany Shale floras of the U.S.A., the Saalfeld and Glatzish-Falkenberg floras from the German Democratic Republic. The data suggest that the ferns and pteridosperms show the most striking changes through the Lower Carboniferous strata.

Earliest Evidence of Insect Endophytic Oviposition

Abstract The knowledge of fossil plant-insect interactions is almost entirely restricted to evidences of feeding behavior. Records of endophytic oviposition are relatively scarce, with previous earliest reports from the Middle to the early Late Triassic. Nevertheless, several Paleozoic insect taxa have been suspected of this reproductive behavior, but without any direct evidence. Specimens of Calamites cistii (Sphenophyta; Pennsylvanian, France) are described showing endophytic cavities, located in the outer cortex of the stem, a tissue that is rarely preserved. This new record shifts the appearance of this behavior back 60 Ma. Possible tracemakers are representatives of the Odonatoptera (Odonata and related extinct taxa), Palaeodictyopteroidea (extinct palaeopterous orders), and Archaeorthoptera (Orthoptera and related extinct orders). The antiquity of the insect endophytic oviposition behavior suggests that it could have been important during the emergence and diversification of the insect group.

First Grammatopteris tree ferns from the Southern Hemisphere – new insights in the evolution of the Osmundaceae from the Permian of Brazil

Abstract The stem anatomy and organization of new anatomically preserved Grammatopteris fern specimens are described from the Permian of the Maranhao Basin (NE Brazil). Grammatopteris freitasii nov. sp. is established to accommodate the newly collected material, which is preserved as silicified permineralization. On the basis of their anatomical details, Grammatopteris rigollotii , the type species originally described from the Permian of Autun, France, and Grammatopteris baldaufii , another species originally described from the Permian of Chemnitz, Germany, are re-examined and discussed. The generic diagnosis of Grammatopteris is emended. Furthermore, all species of the genus Grammatopteris are compared with Rastropteris pingquanensis (Galtier, Wang, Li and Hilton), a recently introduced type of fern from the Lower Permian of China. The Grammatopteris ferns are interpreted as showing a growth habit of small to medium-sized erect trees. Their trunks are 4–35 cm in diameter and possess an exarch maturated solid protostele surrounded by a dense mantle of petiole bases and more downwards completely clothed in a root mantle. Stem cortex contains different types of sclerotic tissue. Leaf trace vascular tissue developes from oval-shaped to tangentially elongated, typically bar-shaped strand. Grammatopteris ferns are thought to be of considerable importance or a link in the origin and early development of Osmundaceae.

Cordaitalean Seed Plants from the Early Permian of North China. I. Delimitation and Reconstruction of the Shanxioxylon sinense Plant

A new whole plant species of cordaitalean coniferophyte is reconstructed from a single Early Permian coal‐ball assemblage in northern China and is named Shanxioxylon sinense after its distinctive stem. This assemblage contains three cordaitalean whole plants reconstructed from evidence, including organs found in organic connection and other examples where two or more organs share distinctive anatomical features. With the exception of the fertile shoot systems, organs of the S. sinense plant may be ascribed to existing cordaitalean morphogenera, although in each case they represent distinct morphospecies. Stems have a septate central pith and have previously been assigned to S. sinense. Primary vascular architecture is sympodial, and primary xylem maturation of the cauline bundles is endarch. Adventitious roots are infrequently observed on smaller stems. Leaf traces are mesarch, diverging from the pith margin as a single bundle and approaching 8/21 phyllotaxis. Leaves are small and needle‐like. Roots are protostelic and ditetrarch, while rootlets are protostelic and diarch, belonging to the morphospecies Amyelon taiyuanense. Both pollen and ovulate cones are assigned to Cathayanthus gen. nov., characterized by helically inserted bract/shoot complexes. Male shoot systems of Cathayanthus ramentrarus comb. nov. have pollen cones with 14–18 scales, of which three to five apical scales may be fertile. Fertile scales possess a ring of approximately five pollen sacs apically, which contain saccate prepollen of the Florinites type. Ovulate cones of Cathayanthus sinensis comb. nov. contain more than 100 scales with the distal half fertile, bearing a single terminal ovule. Ovules are bilaterally symmetrical and have a prominent wing, conforming to the morphospecies Cardiocarpus samaratus. Based on characters of the stem, roots, leaves, male and female shoot systems, and ovules, the S. sinense plant is distinct from other cordaitalean plants, although its features are consistent with models of cordaitalean morphology, anatomy, and architecture, indicating that it belongs to this group. The S. sinense plant shows that coniferophyte fertile shoot systems with vertically arranged rows of bract/shoot complexes can no longer be considered diagnostic of, or synapomorphic to, cordaitalean coniferophytes.

The diversification of early arborescent seed ferns

Abstract Galtier, J. and B. Meyer-Berthaud. (UMR Botanique et Bioinformatique, CIRAD, TA40/PS2, 34398 Montpellier, France). The diversification of early arborescent seed ferns. J. Torrey Bot. Soc. 133: 7–19. 2006.—Seed plants of the lowermost Carboniferous time (Tournaisian) display important differences in morphology and habit with at least two size classes. On one side are plants of modest stature with protostelic stems, manoxylic wood and large leaves, interpreted as calamopityan, buteoxylalean and lyginopteridalean seed ferns, and on the other side are arborescent plants, with trunks up to 2 metres in diameter, of which the systematic position remains unclear. We summarize present information on these trees characterized by a thick development of generally dense wood, a broad eustele consisting of a large number of discrete primary xylem strands, short internodes and deciduous medium-sized fronds. New data have been recently obtained on Pitus, the best known member of this group, on Eristophyton, Bilignea, Stanwoodia, Aporoxylon and on several new taxa which exhibit a broad circular parenchymatous pith surrounded by numerous sympodial xylem strands, but which differ in secondary xylem and leaf trace features. Of particular interest is a new plant that has leaf traces originating as a double strand and a petiole base of the Kalymma-type, therefore showing characteristics of calamopityan seed ferns but being quite distinct in features of the stele, secondary xylem and phloem. Emphasis is placed on the evolutionary dynamics of this important diversification of arborescent plants which included: i) a rather abrupt increase in overall diameter, ii) increase in primary xylem size, with regard to other contemporaneous early seed plants; iii) very different types of wood, instead of a single dense/pycnoxylic wood as generally assumed; iv) distinct periderm types; v) deciduous leaves. The last feature may be interpreted as an innovation, related to the tree habit, within the lignophytes. The origin and systematic position of these arborescent plants remain problematical.

The Origins and Early Evolution of the Megaphyllous Leaf

Paleobotanical data, with emphasis on anatomical characters in ferns and seed plants, confirm that the megaphyllous leaf evolved independently several times from the Middle Devonian to the Early Carboniferous. Fernlike cladoxylaleans and aneurophytalean progymnosperms possessed only megaphyll precursors homologous with the small megaphylls of archaeopteridalean progymnosperms. Different trends toward developing a large megaphyll, from the modification of lateral branch systems of some basal euphyllophytes, are shown by the fernlike rhacophytaleans and by the zygopterid and tedelean ferns. Zygopterids, with their tridimensional frond, petiole of the phyllophore type, and annulate sporangia, must be considered as the earliest undisputable ferns while the probably derived tedeleans have evolved toward a convergent filicalean‐type of frond. The leaf of other early ferns certainly derived through a minimal change in anatomy from other Devonian euphyllophytes. Early seed plant leaves probably evolved through the modification of an entire lateral branch system of aneurophytalean or stenokolean ancestors. In contrast to ferns, the seed plants early developed broad laminate pinnules with dichotomous nervation. The leaves of ferns and seed plants are not homologous, and fundamental differences in their petiole anatomy support the early divergence of the two groups.

Diversification of early ferns

A review of current knowledge of early fern evolution is presented including new data on age, morphology and anatomy with two diagrams summarising the early diversification of cauline and foliar anatomy and of the reproductive structures. The relationships and even the attribution of some Devonian taxa to the ferns is questioned whilst most of the Carboniferous coenopterids are considered indisputable ferns, some of them being related to modern filicaleans. The discovery, in the Lower Carboniferous of Scotland, of diverse annulate filicalean sporangia suggests an earlier (Tournaisian) radiation of true ferns than was previously assumed.

Distribution and ecology of early ferns

A review of current knowledge of the distribution of Palaeozoic ferns and fern-like plants is presented. Whilst numerous putative ferns occur in the Devonian, it is not until the Lower Carboniferous that ferns belonging to the Filicales appear. The Namurian represents a major gap in our knowledge. The ecology of late Palaeozoic ferns is reviewed. The association of early fern assemblages with volcanic terrains is considered particularly significant in the relationship between evolution and environment. Extinction of more specialised groups may have been caused by climatic changes.

Plant Taphonomy and Paleoecology of Late Pennsylvanian Intramontane Wetlands in the Graissessac-Lodève Basin (Languedoc, France)

Abstract The Late Pennsylvanian Graissessac-Lodève basin is a small, fluvio-palustrine depocenter located in the southern part of the Massif Central (France). A taphonomic and sedimentologic study carried out in this area allows a reconstruction of Late Carboniferous vegetation in an intramontane context. The paleoecology of such limnic settings is poorly known, and this study permits detailed comparison with paralic basins for the first time. The Graissessac peat mires developed in abandoned fluvial channels, in floodplains, and above distal alluvial fans. The vegetation was dominated by monospecific stands of the arborescent lycopsid Sigillaria brardii, whereas the tree fern Psaronius occurred during the later stages of mire accretion. This is in contrast to coeval North American peat mires, which generally were dominated by tree ferns and pteridosperms throughout the mire profile. Stephanian floodplains and distal alluvial fans of the Graissessac-Lodève Basin were devoid of vegetation, with the exception of isolated thickets of sphenopsids that were composed of Calamites and Sphenophyllum. These plants were found growing in situ in the floodplain mudstones as well as in fine-grained sands of secondary channels. Parautochthonous foliage assemblages of ferns and pteridosperms found in floodplain mudstones represent the most diverse plant community. The plants supplying these remains were growing in exposed areas close to floodplains. Large logs attributed to cordaitaleans and monotypic assemblages of large Cordaites leaves were found in fluvial sediments, and suggest that the plants were riparian elements in the basin.

A new late Tournaisian (lower carboniferous) flora from the Kilpatrick Hills, Scotland

Abstract Permineralized plants have been collected from the basal part of the section of Lower Carboniferous rocks at Loch Humprey Burn. These rocks have also yielded a rich CM Biozone palynoflora indicating a late Tournaisian (Tn3 — Courceyan) age. The well-preserved vegetative and reproductive structures are mostly of different species from those previously collected at this locality, from the top of the section, which is of early to middle Visean age. The vegetative remains are assigned to Archaeocalamites Stur, Cladoxylon cf. taeniatum Unger, Hierogramma Unger, Clepsydropsis Unger, Metaclepsydropsis Bertrand, Botryopteris cf. antiqua Kidston, Kalymma Unger and Lyginorachis Kidson. Of special interest are the abundant and diverse fructifications bearing in situ spores; this material is currently under study, using a range of techniques: peel sections, macerations and scanning electron microscopy. Several species of sphenopsid fertile organs occur, as well as sporangia related to those of the zygopterid ferns Corynepteris (annulate) and possibly Musatea (exannulate), and also annulate filicalean sporangia of the Botryopteris antiqua-type with spores referable to the dispersed miospore genus Dictyotriletes. Still another category of sporangia contains spores referable to the dispersed miospore genus Knoxisporites. In addition, a detached radial synangium composed of eight sporangia fused laterally for about 3/4 their length is attributed either to an early seed-fern or an early marattialean fern. This material provides the oldest evidence for early true fern diversification.