Muriel Fairon-Demaret

Lorophyton goense gen. et sp. nov. from the Lower Givetian of Belgium and a discussion of the Middle Devonian Cladoxylopsida

Lorophyton goense gen. et sp. nov. is described from Lower Givetian strata at Goe (Vesdre Synclinorium, Belgium). This moderately sized plant resembles a small tree with robust roots and a crown of branches. The vegetative ultimate units are three-dimensional and dichotomize profusely. The fertile ultimate units also are three-dimensional and consist of two parts of unequal size: in each part a pseudo-main axis terminates with a dichotomous division and bears three dichotomously divided laterals. Either all the segments of the fertile units terminate in a pair of pendulous elongated sporangia, or several of them remain vegetative. The cladoxylalean affinities of the plant are discussed and the phylogeny of the Cladoxylopsida during Devonian time is considered.

The plant Leclercqia (Lycopsida) in Gondwana: implications for reconstructing Middle Devonian palaeogeography

Abundant and well-preserved material of the ligulate lycopsid genus Leclercqia is reported from a new Middle Devonian locality in northeastern Queensland (Australia). The plants occur in a chert horizon in the Storm Hill Sandstone of the Dosey-Craigie Platform. Lithological data and conodont analyses combined with information from in situ spores provide an age for the plant levels ranging from Eifelian, possibly Middle Eifelian, to Early Givetian. Plant taxonomic identification is based on vegetative and fertile stems that display both external morphology and anatomy. This material represents the best documented occurrence of Leclercqia outside Laurussia and possibly the earliest in Gondwana; it provides evidence that colonization of Gondwana by the species L. complexa was contemporaneous to that of Siberia and Kazakhstan. Analysis of the distribution patterns of L. complexa suggests that it was adapted to a wide range of environments, but within certain limits which we hypothesize to be those of a climatic belt. Such considerations support previous studies using other biological data, such as faunas and palynomorphs, for reconstructing Devonian palaeogeography. They favour a close proximity of Laurussia and Gondwana rather than the occurrence of a wide ocean separating the two palaeocontinents in Middle Devonian times.

Givetian-Frasnian phytogeography of Euramerica and western Gondwana based on miospore distribution

Abstract The Givetian and Frasnian miospore distributions in western Gondwana and southern Euramerica show a rather uniform vegetation prevailing from palaeo-polar to palaeo-tropical regions. Similar climatic conditions are certainly required to explain this but it is concluded from a discussion on the dispersal of homosporous vegetation that no wide oceans separated these regions at the time. Frasnian northern Euramerica vegetation seems different and might correspond to an equatorial belt. Heckel & Witzkes palaeogeographical reconstruction fits much better with the miospore distribution than other maps.

Lower and middle devonian miospore-based stratigraphy in Libya and its relation to the megafloras and faunas

Abstract A review of miospores, faunas and megafloras of the Lower and Middle Devonian in Libya allows new conclusions to be drawn. The application of the Ardenne-Rhenish Devonian miospore zonation in Libya gives the following results. In the North Hammadah Basin, the base of the Tadrart Formation might well be strongly diachronous depsite the lithostratigraphical correlations shown on the base of “Gamma-Ray/Neutron” logs. At least the lower part of the Tadrart Formation in borehole MG-1 is within the lowermost part of the Lochkovian not at its base. In the southern margin of the Hammadah Basin, the Tadrart and Ouan-Kasa formations are probably not older than late Emsian, maybe early Eifelian. The Ouenine Formation I is often absent there or strongly reduced. The isochroneity of the (discordant) lower limit of the Tadrart Formation across the Hammadah Basin is far to be demonstrated. The Caledonian age of the discordance on the southern margin of the Hammadah Basin can obviously be challenged. In the eastern Murzuk area, the plant-bearing Tadrart-Emi Magri formations have a Middle Devonian age according to the plant fossils themselves. The discordance which separates these formations from the Acacus Sandstone at Dor el Goussa has to be late Early Devonian or Middle Devonian because the Acacus Sandstone “Psilophytes” cannot be older than Pragian and can even be younger (Emsian). There is obviously no available argument which could counteract the fossil floral data and prove that the discordance in the eastern Murzuk has the same age as the Silurian/Devonian transitional beds in the northern Hammadah Basin.

Dorinnotheca streelii Fairon-Demaret, gen. et sp. nov., a new early seed plant from the upper Famennian of Belgium

Dorinnotheca streelii Fairon-Demaret, gen. et sp. nov. is described from three upper Famennian localities in Belgium. This new early seed plant bears cupules hanging singly at the tips of the slender ultimate axes of a pinnately branched system. Each cupule encloses a single, centrally located preovule with four free integumentary lobes. At the base of the fertile unit, the cupule segments are fused for a quarter of their total length; higher up they are free, recurved and highly dissected. The integumentary lobes appear joined to the fused part of the cupule segments. The preovule is sessile; at the apex, the nucellus shows a long, tubular, salpinx-like extension. This distinctive type of organisation is discussed in relation to the other Late Devonian preovulate structures from which it appears different.

The in situ Glyptostroboxylon forest of Hoegaarden (Belgium) at the Initial Eocene Thermal Maximum (55 Ma)

Abstract Hundreds of silicified standing stumps have been discovered within a lignitic horizon in the middle of the Tienen Formation near Hoegaarden in northeast Belgium. The anatomical features of the fossil stumps, as those of the numerous silicified secondary xylem remains collected since the last century from this area, demonstrate that they all belong to a single taxodiaceous taxon. The stumps bear characteristics shared by Taxodioxylon gypsaceum and Glyptostroboxylon tenerum, but affinities with the latter appear closer. They are attributed to Glyptostroboxylon sp. Calibration of the sedimentological, stratigraphical and organic carbon isotope data reveals that these taxodiaceous fossil trees developed in a swampy lowland environment most probably during the Initial Eocene Thermal Maximum at ca. 55 Ma.

Fruits and seeds from the Tienen Formation at Dormaal, Palaeocene–Eocene transition in eastern Belgium

Abstract The Belgian locality of Dormaal is famous for the diversity of its vertebrate faunas that illustrate part of the biota at the Palaeocene–Eocene transition in northwest Europe, 55 million years ago. This paper completes the palaeoenvironmental information with the description of fruits and seeds collected at Dormaal in the same layers as the vertebrates. Fleshy fruits, drupes and berries produced by climbing plants, especially woody lianas, (Menispermaceae, Vitaceae and Icacinaceae), are well represented. The assemblage includes also aquatic plants (Lythraceae) and trees or shrubs (Nyssaceae, ?Theaceae and ?Ericaceae). Reconstruction of the local environment confirms the analysis made from the vertebrates, and indicates the presence of a channel in a densely wooded area with a warm–humid to subtropical climate.

A propos des specimens determines Protolepidodendron scharianum par Kräusel et Weyland, 1932

Abstract Several specimens of Protolepidodendron scharianum which are part of Krausel and Weylands (1932) original collection from the Middle Devonian of Elberfeld (Germany) are restudied. The leaves when uncovered from the embedding sediment show morphological features which are different from those of P. scharianum leaves. Evidence is provided that transversal sections through the axes exhibit an exarch xylem strand which is circular rather than triangular in outline. In the light of these new features the characteristics of P. scharianum and the validity of P. gilboense are discussed.

Les plantes fossiles de l'emsien du sart tilman, Belgique. I. Stockmansia langii (Stockmans) comb. nov.

Abstract Taeniocrada langii Stockmans is transferred to the new genus Stockmansia Fairon-Demaret on the basis of the morphology of its sporangia and its anatomical structure. The ribbon-like axes bear lateral sporangia. The sporangia are fusiform and attached to the axis by a pad of tissue, circular in outline, which most probably functioned as an abcission layer. They dehisce along a specialized longitudinal slit which is clearly distinguishable from the more or less numerous splitting lines. The conducting strand is composed of helically strengthened cylindrical elements which are of various diameters. It can not be defined as the xylem strand of a “classical” tracheophyte. The affinities of the plant remain obscure.

Archaeopteris from the Upper Famennian of Belgium: Heterospory, Nomenclature, and Palaeobiogeography

New fertile specimens of Archaeopteris roemeriana from Upper (but not uppermost) Famennian strata of Belgium have been studied. Crowded sporangia are borne on non-laminate, three times bifurcate fertile leaves helically arranged around the fertile ultimate axes. Vegetative leaves occur both proximal and distal to the fertile leaves. Heterospory is demonstrated with miospores belonging to the Geminospora-Aneurospora complex and macrospores most probably to Contagisporites genus. The established morphological traits allow us to substantiate a synonymy between A. roemeriana and A. halliana. The apparent dominance of A. halliana on the eastern side of the Acadian mountains during Late Famennian times is discussed.