Philippe Steemans

• PhD Doctor in Sciences
• Senior Researcher at University of Liège

The Early Devonian plant fossil record provides evidence of large vegetation turnover events in addition to rapid morphological and anatomical changes among vascular plants. The Ardenno-Rhenish Massif has historically yielded a vast number of these plant fossils allowing us to obtain a nearly unparalleled snapshot of Early Devonian vegetation. None...

We present a review of Devonian palynology in Saudi Arabia based on the study of palynological samples from the subsurface of northern and central Saudi Arabia collected from the Tawil, Jauf and Jubah formations. Saudi Arabian Devonian palynological assemblages are dominated by abundant, well-preserved, and diverse miospores character- ized by low...

This paper describes dispersed cryptospores and trilete spores from tropical, temperate and cool climate belts within Přídolí and compares them with the land plant megafossil record. The palynology of earlier intervals in the Silurian are also reviewed. A common feature of the cryptospore and trilete spore records is that their number is surprising...

Acritarchs are an informal, polyphyletic, and morphologically heterogenous group of organic-walled microfossils of unknown biological affinity. Some acritarchs share morphological similarities with certain microplankton resting stages (from e.g., dinoflagellates, prasinophycean-, chlorophycean-, and zygnematophycean green algae), others with miospo...

The depositional successions of the Ponta Grossa Formation (Paraná Basin, Brazil) correspond to a wave-dominated shallow-marine environment. The marine fraction of the palynological assemblages of the Jaciara section is composed of highly abundant and diverse organic-walled phytoplankton. The section yielded worth-noticing new phytoplankton species...

The Lower Devonian Klerf Formation is an exceptional Konservat-Lagerstätte, exposed at multiple sites in the Waxweiler region in the Eifel area, western Germany. It has been studied for its various fossils, mainly arthropods, fishes, plants, molluscs, brachiopods, and crinoids. At Waxweiler, the sediments are palaeoecologically interpreted as a pro...

The depositional succession of the Ponta Grossa Formation (Paraná Basin) corresponds to a wave-dominated shallow-marine environment, represented by four coarsening-upwards cycles, limited by flooding surfaces. Previous studies on a well-preserved and diverse assemblage of miospores indicated a late Pragian to possibly middle Emsian age. The palynol...

The oldest reported occurrence of cryptospores supposed to derive from land plants (embryophytes) is currently considered to be in the Middle Ordovician. The two genera Virgatasporites and Attritasporites, described in the 1960ʹs from the Early Ordovician (Tremadocian) of Algeria, are morphologically close to the miospores, and therefore pose a dil...

Assemblages of cryptospores were reported and detailed for the first time from the Upper Ordovician from Brazil. These assemblages were recovered from diamictites and shales with dropstones of the Iapó Formation, Rio Ivaí Group, Paraná Basin. The analyzed sequence represents the Hirnantian glacial deposits containing well-preserved palynomorphs wit...

Lower Devonian plant megafossil assemblages are relatively uncommon although palaeogeographically dispersed. Their analysis indicates broad patterns of palaeophytogeographic distribution including the identification of areas with a high degree of provincialism. On the other hand Lower Devonian dispersed spore assemblages are both more numerous and...

The Tawil Formation was penetrated by two wells drilled on the Arabian Gulf coast in Saudi Arabia. The depositional environments of the formation range from shallow marine to braided-stream fluvial. The sampled intervals fall within a fining-upward succession that is probably a transgressive systems tract (TST) representing backfilling of an estuar...

The Rhynie chert (Aberdeenshire, Scotland, UK) plant Horneophyton lignieri is likely one of the most studied elements of Lower Devonian floras considering both macro and microremains. Intriguingly, while larger plant fragments are exceptionally fossilized, in situ spores are not necessarily well-preserved in the chert: they are dark brown and inten...

Gondwanan floras of Late Devonian age are poorly known. In Australia, the rare studies that have been published on Late Devonian plants are old and need reinvestigation. This paper is an account of the plant macro- and micro-remains found in the Mandowa Mudstone at Barraba, New South Wales. According to the miospores, plants are late to latest Fame...

Palynological investigations have been carried out on samples from the Upper Devonian Hongguleleng Formation of Western Junggar, Xinjiang, NW China. In total, 26 miospore species belonging to 19 genera and 28 acritarch species assigned to 19 genera have been recognized from the lower member of the Hongguleleng Fm. in the Bulongguoer section. The pa...

Accurate palyno-analysis by S. Loboziak (from 1980 to 1983) of 28 samples from the Upper Givetian to the Middle Frasnian Blacourt, Beaulieu and Ferques Formations and of 44 samples of the Upper Frasnian to the Lower Famennian Hydrequent Formation are re-evaluated. Chelinospora concinna, Verrucosisporites bulliferus, Cirratriradites jekhowskyi, Loph...

An integrated palynological and geochemical approach has been initiated to date and to precise the geochemical events of the Pimenteiras Formation, in the Late Devonian from the Parnaíba Basin, Brazil. Based on good biostratigraphic markers and presence of index species among miospores, acritarchs and chitinozoa, the investigated sequences are refe...

It is revealed that the lowest 1010 m of the Saint-Ghislain borehole (-4393 to -5403 m), of which cuttings are available, constitutes a crucial source of information to investigate, amongst others, the deep geothermal potential within the Brabant Parautochthon, underlying the Mons Basin, Hainaut. The lithological succession of this interval was rec...

The present study concerns the palynology (mainly miospores), and geochemistry of the Jaciara section, situated 5 km from the town of Jaciara, Mato Grosso, in the Paraná Basin of Brazil. The age of this outcrop is considered to be Early Devonian. A study of the whole assemblage has highlighted a diversified association of miospores. Their distribut...

Rich and well preserved dispersed spore assemblages have been recovered from Early Devonian (Pragian-Emsian) marine deposits of the Cantabrian Mountains of northern Spain. Devonian Iberia was part of an assemblage of islands, known as the Armorican Terrane Assemblage, separated from Laurussia to the north by the Rheic Ocean and Gondwana to the sout...

Land plants comprise the bryophytes and the polysporangiophytes. All extant polysporangiophytes are vascular plants (tracheophytes), but to date, some basalmost polysporangiophytes (also called protracheophytes) are considered non‐vascular. Protracheophytes include the Horneophytopsida and Aglaophyton/Teruelia. They are most generally considered ph...

Most evolutionary innovations in plant vascular tissues, including secondary growth, occurred during the Devonian period (~420 to 360 million years ago). Such innovations had a major impact on land colonisation by plants and on their biodiversity. Here, we show the hydraulic conductance of the secondary xylem of three shrubby or arborescent plant f...

The Lower Devonian Posongchong Formation (Wenshan, Yunnan Province, southwestern China) consists of a series of continental deposits with an outstanding plant megafossil diversity. More than 20 years ago, this formation was interpreted as ‘Siegenian' (∼Pragian) in age based on palynology. However, such interpretation needs further evidence because...

Lycopsids are a minor component of current terrestrial herbaceous floras. However, lycopsid fossil diversity shows a great diversity and disparity including heterosporous woody plants, e.g. the giant isoetaleans that populated the extensive Pennsylvanian wetlands. The earliest known isoetaleans come from late Devonian localities from China. Here, w...

Characters used in the phylogenetic analysis. Most are identical to those of Xue [8]. In bold: characters modified (2 to 4) in comparison with Xue [8]. (PDF)

Tree file (Newick format) of strap analysis. (PDF)

Age file (R package paleotree format) of strap analysis. (PDF)

Data matrix for the phylogenetic analysis. Raw data based on Xue [8]. Two taxa in bold (Lilingostrobus and Wuxia) have been added. Some modifications of raw coding in comparison with Xue [8] are shown in boxed numbers. (PDF)

List and temporal distribution of lycopsid genera involved in phylogenetic analysis. Absolute ages used for the time-scaled phylogeny appear in brackets. They are from the International Chronostratigraphic Chart (v2016/04). See S4 Text for supplementary references. (PDF)

Data matrix (Nexus format) of PAUP analysis. (PDF)

Supplementary references. (PDF)

Marine and terrestrial palynomorphs from the Loma de los Piojos section of the Precordillera Basin, western Argentina, were analyzed. The studied section embraces the upper part of the Lower Devonian Talacasto Formation and the whole Lower-Middle? Devonian Punta Negra Formation, which constitute the Gualilán Group. Terrestrial palynomorphs dominate...

My publications up to April 2018

The palynological content from the Cerro La Chilca and Quebrada Ancha sections of the Wenlock? to Přídolí Los Espejos Formation, in the Argentinean Precordillera is studied. The marine palynomorphs exhibit higher relative abundance and diversity in almost all the productive samples, except for the uppermost ones from both sections, in coincidence w...

Dispersed spores interpreted as deriving from the earliest land plants have complex configurations (e.g. permanent dyads and permanent tetrads) and are readily distinguished from the more familiar trilete spores that often dominate post-Late Silurian dispersed spore assemblages. These forms occur mainly from the Middle Ordovician to Early Devonian....

Palynological interpretations of both spores and acritarchs from the Devonian Tiffrit Formation located in Saïda (North-Western Algeria) support identical conclusions. Species of spores and acritarches that appear in the upper layers of the younger reference unit, named Boukourdène (BK1), are compatible with a Pragian-Emsian age, based especially o...

A rare occurrence of a rich and diverse palynological assemblage from the Tawil Formation is described from well JLMD-EW-8 in northwestern Saudi Arabia. The composition of this assemblage strongly indicates a middle Přídolí age. The assemblage encountered contains very characteristic chitinozoans, acritarchs, tasmanitids, freshwater algae, scolecod...

Core samples from the QSIM-801 water well, drilled in central Saudi Arabia, cover a 93-foot interval spanning the transition between the Sajir Member of the Saq Formation, that consists mainly of sandstones of tidal sand flat environments, and the Hanadir Member of the Qasim Formation, characterized by argillaceous graptolitic mudstones, correspond...

The inability to unambiguously distinguish the biogenicity of microfossil-like structures in the ancient rock record is a fundamental predicament facing Archean paleobiologists and astrobiologists. Therefore, novel methods for discriminating biological from nonbiological chemistries of microfossil-like structures are of the utmost importance in the...

In Australia, lycopsids are abundant in early land plant assemblages, leading to the concepts of a “Baragwanathia flora” extending from the late Silurian to the Early Devonian, and a “Leptophloeum flora” characterizing the Late Devonian. Yet, the taxonomic status and systematic affinities of a large number of lycopsid remains from the Devonian of A...

The QSIM-801 well from Central Saudi Arabia contains beds transitional between the Sajir Member of the Saq Formation and the Hanadir Member of the Qasim Formation. Core samples from these beds yielded rich assemblages of well-preserved palynomorphs of low thermal maturity. They are dominated by marine forms (acritarchs, chitinozoans and scolecodont...

A distinctive, rich and diverse marginal marine palynological assemblage from the Tawil Formation occurs in several wells from northwestern and eastern Saudi Arabia. The composition of this assemblage strongly indicates a middle Přídolí age. The assemblage encountered contains abundant, miospores, chitinozoans, acritarchs, tasmanites, freshwater al...

The Silurian succession of the Precordillera, western Argentina, constitutes a typical foreland basin deposit. The middle-upper Silurian to Lower Devonian (Wenlock to Lochkovian) is represented in the Los Espejos Formation. It is composed of siliciclastic, mainly fine-grained shelf deposits with a gradual upward thickening and coarsening and eviden...

A new well-preserved spore assemblage has been discovered from the Lower Devonian Nogueras Formation of Mezquita de Loscos (Teruel Province, north-eastern Spain). The palynoflora includes 34 spore species belonging to 20 genera, among which 14 are new for the locality, e.g. Apiculiretusispora, Brochotriletes, Cirratriradites, Iberoespora, Knoxispor...

A database of all reported Ordovician?Silurian land plant megafossil and dispersed spore assemblages has been assembled. For each assemblage a list of taxa has been prepared and its location plotted on new palaeocontinental reconstructions. These new data compilations are analysed with respect to palaeophytogeographical differentiation and various...

All publications, communications, books etc published up to 2015

Chap. 3 of the PhD Thesis of Mohamed M.A. Elkelani

Acritarchs and prasinophyte algae, associated with more enigmatic freshwater and marine organic-walled microfossils, are a major component of the Silurian palynofloras of the Arabian Peninsula. Significant advances in the knowledge of the palynological associations and their distribution have been made since the initial phase of the joint Saudi Ara...

Palynological analyses were carried out on 50 samples from the Övedskloster 1 (Ö1) and 2 drillcores (Ö2), southern Sweden. The study revealed well-preserved palynological assemblages including 77 spore species in 28 genera, and some additional forms retained under open nomenclature. The spore assemblages are collectively dominated by trilete spores...

Palynological analysis of a sequence of Upper Ordovician to lowermost Silurian sediments from the Qusaiba-1 core hole drilled in the Qasim region of central Saudi Arabia has yielded rich palynomorph assemblages. The palynomorphs are abundant, exceptionallywell preserved and of lowthermalmaturity. The sequence represents marine sediments that encomp...

The palynological assemblages of the upper part of the Los Espejos Formation and the lower part of the Talacasto Formation, in the northern outcrops of San Juan Precordillera, Argentina, were studied. This section spans the Silurian/Devonian boundary. Therefore the palynological analysis helps to constrain the age and to identify the position of th...

A new euphyllophyte, Planatophyton hujiersitense gen. et sp. nov., is described on the basis of adpression fossils collected from a late Early or Middle Devonian locality from the Hujiersite Formation in the Hujiersite area, Hoboksar County, North Xinjiang, North-West China. The plant is possibly rhizomatous and comprises main axes with alternately...

Palynological assemblages from a conventional core taken during the drilling of a velocity survey well in central Saudi Arabia near Arabian Shield contained abundant cryptospores. The cored interval is within a succession of grey shale of the early Silurian Qusaiba Member, Qalibah Formation. Samples have common specimens of Leiosphaeridia spp. (of...

A database of all reported Ordovician–Silurian land plant megafossil and dispersed spore assemblages has been assembled. For each assemblage a list of taxa has been prepared and its location plotted on new palaeocontinental reconstructions. These new data compilations are analysed with respect to palaeophytogeographical differentiation and various...

This study is concentrated on Ludlow (to Pridoli?) miospores from the Los Espejos Formation at the Quebrada Ancha locality, Central Precordillera, San Juan Province, Argentina. The Ludlow age is in agreement with the age based on acritarchs. The assemblage of continental palynomorphs is composed of 43 miospore species (29 trilete spores and 14 cryp...

Devonian spores from 16 subsurface successions in Saudi Arabia and North Africa are systematically documented to characterise assemblages for the northern margin of western Gondwana. The taxonomic study provides the identification and description for 205 spore taxa and form the basis for a refined biostratigraphy and palaeogeography. Most species a...

Well preserved assemblages of cryptospores, chitinozoans, acritarchs, leiospheres, tasmanitids, colonies of Gloeo-capsomorpha, scolecodonts and eurypterid fragments from 23 core samples of the Moussegouda core hole in the Erdi Basin, northern Chad, and from two samples from well KW-2 in Kufra Basin, South East Libya are investigated. These palynomo...

The advent of wood (secondary xylem) is a major event of the Paleozoic Era, facilitating the evolution of large perennial plants. The first steps of wood evolution are unknown. We describe two small Early Devonian (407 to 397 million years ago) plants with secondary xylem including simple rays. Their wood currently represents the earliest evidence...

This study is concentrated on Ludlow (to Pridoli?) miospores from the Los Espejos Formation at the Quebrada Ancha locality, Central Precordillera, San Juan Province, Argentina. The Ludlow age is in agreement with the age based on acritarchs. The assemblage of continental palynomorphs is composed of 43 miospore species (29 trilete spores and 14 cryp...

A palynological study based on sedimentary rocks (mainly calcareous siltstones and mudstones with minor carbonate beds) from the upper Silurian ved-Ramsåsa Group in the Klinta 1 and Bjärsjölagård 2 drillcores, Skåne, Sweden, reveals a rich assemblage of well-preserved spores produced by early land plants. Thirty-four spore taxa belonging to 19 gene...

Recently, major advances have been made in understanding terrestrialization processes and the development of early vegetation. This chapter reviews the major steps in the evolution of early land plants, with focii on cryptospores, trilete spores and on the meso- and megafossil remains of Silurian and Devonian plants. The major morphological innovat...

The advent of wood (secondary xylem) is a major event of the Paleozoic Era, facilitating the evolution of large perennial plants. The first steps of wood evolution are unknown. We describe two small Early Devonian (407 to 397 million years ago) plants with secondary xylem including simple rays. Their wood currently represents the earliest evidence...

A restudy of Devonian palynological assemblages of samples from the A1-69 borehole, drilled in the Ghadamis Basin, western Libya, North Africa has led to the discovery of numerous well-preserved megaspores amongst abundant miospores, rare acritarchs and rare chitinozoans. Thirteen samples from base to top, 1496 ft (456 m) up to 965 ft (294 m), cont...