References of "Steemans, Philippe"
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Steemans, Philippe ULg

Textual, factual or bibliographical database (2005)

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See detailRuncaria, a middle Devonian seed plant precursor
Gerrienne, Philippe ULg; Meyer-Berthaud, B.; Fairon-Demaret, Muriel ULg et al

in Science (2004), 306(5697), 856-858

The emergence of the seed habit in the Middle Pateozoic was a decisive evolutionary breakthrough. Today, seed plants are the most successful plant lineage, with more than 250,000 living species. We have ... [more ▼]

The emergence of the seed habit in the Middle Pateozoic was a decisive evolutionary breakthrough. Today, seed plants are the most successful plant lineage, with more than 250,000 living species. We have identified a middle Givetian (385 million years ago) seed precursor from Belgium predating the earliest seeds by about 20 million years. Runcaria is a small, radially symmetrical, integumented megasporangium surrounded by a cupule. The megasporangium bears an unopened distal extension protruding above the multilobed integument. This extension is assumed to be involved in anemophilous pollination. Runcaria sheds new light on the sequence of character acquisition leading to the seed. [less ▲]

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See detailThe Moesian Terrane during the Lochkovian - a new palaeogeographic and phytogeographic hypothesis based on miospore assemblages
Steemans, Philippe ULg; Lakova, I.

in Palaeogeography, Palaeoclimatology, Palaeoecology (2004), 208(3-4), 225-233

The relative position of terranes during the Palaeozoic can be indicated by a combination of palaeomagnetic and floral/faunal evaluation. Palaeomagnetic data are absent from the Moesian Terrane, South ... [more ▼]

The relative position of terranes during the Palaeozoic can be indicated by a combination of palaeomagnetic and floral/faunal evaluation. Palaeomagnetic data are absent from the Moesian Terrane, South-Eastern Europe, and its position is here estimated thanks to palaeophytogeographic considerations based on miospore assemblages. Miospore assemblages have been studied in two boreholes from northern Bulgaria. Preliminary analyses of chitinozoans, acritarchs and phytodebris have already been published. The oldest samples were considered to be of Pridoli age based on chitinozoan data, but here we provide new miospore evidence suggesting a Lochkovian age. This age determination is in accordance with the new interpretations based on previously published acritarch data. It is likely that the previous Pridoli age determination was influenced by Pridoli chitinozoans being reworked into the Lochkovian. The miospores are typical of assemblages only present in a small area of Avalonia and the western part of the Baltica Plate, and belong to the sinuosus-zavallatus (S-Z) Phytogeographic Province, defined here. On the contrary to the miospores, marine palynomorphs have affinity with Gondwanan assemblages. The different palaeogeographic affinities of the different palynomorph groups are not necessarily in contradiction, as it has recently been suggested that the Rheic Ocean did not act, around the Silurian-Devonian boundary, as a hermetic barrier for transoceanic chitinozoan and acritarch exchange. Therefore, the results are tentatively interpreted as indicating that the Moesian Terrane, belonging to the S-Z Province, was close to southern Laurussia during the Lower Devonian. This northern position of the Moesian Terrane during the Lower Devonian conflicts with most current palaeogeographic reconstructions, but partially supports the hypothesis of a migration of this terrane from Gondwana to Laurussia during the Palaeozoic. The possible presence of reworked palynomorphs in the Lochkovian may reflect early tectonic events associated with the close proximity of the Moesian Terrane and the Dobrudgea periphery of Palaeo-Europe. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailMiospores and the emergence of land plants
Steemans, Philippe ULg; Wellman, C. H.

in Webby, B.; Paris, F.; Droser, M.L. (Eds.) et al The Great Ordovician Biodiversification Event (2004)

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See detailPosition of the Moesian platform at the Lochkovian. Hypothesis based on miospores
Steemans, Philippe ULg; Lakova, I.; Breuer, P.

Conference (2004)

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See detailLlandovery biostratigraphy of the Paraná Basin, East Paraguay
Mendlowicz Mauller, P.; Pereira, E.; Grahn, Y. et al

Conference (2004)

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See detailPalynology of the Jauf Formation from the Northeastern part of the Arabian Shield
Al-Ruwaili, M.; Breuer, P.; Higgs, K. et al

Conference (2004)

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See detailAnálise bioestratigráfica do intervalo Llandoveriano da Bacia do Paraná no Paraguai Oriental
Mendlowicz Mauller, P.; Pereira, E.; Grahn, Y. et al

in Revista Brasiliera de Paleontologia (2004), 7(1), 199-212

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See detailA Psammosteid Heterostracan (Vertebrata: Pteraspidomorphi) from the Emsian (Lower Devonian) of the Grand Duchy of Luxembourg
Delsate, D.; Blieck, A.; Steemans, Philippe ULg

in Geologica Belgica (2004), 7(1-2), 21-26

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See detailThe plant Leclercqia (Lycopsida) in Gondwana: implications for reconstructing Middle Devonian palaeogeography
Meyer-Berthaud, B.; Fairon-Demaret, Muriel ULg; Steemans, Philippe ULg et al

in Geological Magazine (2003), 140(2), 119-130

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 ... [more ▼]

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. [less ▲]

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See detailAnalysis of the Llandovery in the Paraná Basin, Paraguay, boreholes 269-R1 and 269-R2
Mauller, P. M.; Pereira, E.; Grahn, Y. et al

Conference (2003)

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See detailDe l'utilité des miospores en prospection pétrolière
Steemans, Philippe ULg

Scientific conference (2003)

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See detailVila Maria Formation (Silurian, Parana Basin, Brazil): integrated radiometric and palynological age determinations
Mizusaki, A. M. P.; Melo, J. H. G.; Vignol-Lelarge, M. L. et al

in Geological Magazine (2002), 139(4), 453-463

Fresh shale samples taken from a well-known outcrop section of the Silurian Vila Maria Formation, located on the northeastern margin of the Parana Basin (Tres Barras Farm, Goias State, central-western ... [more ▼]

Fresh shale samples taken from a well-known outcrop section of the Silurian Vila Maria Formation, located on the northeastern margin of the Parana Basin (Tres Barras Farm, Goias State, central-western Brazil), have been analysed for both palynological and radiometric age determinations. The rocks yielded a fairly diverse, age-definitive cryptospore assemblage, and the same samples proved suitable for Rb-Sr analysis, despite Silurian sedimentary rocks being rarely suited to radiometric dating techniques. This study thus introduces an alternative, independent method for estimating the minimum depositional age of the Vila Maria Formation. The Rb-Sr age value has been calculated via an isochron diagram that yields 435.9 +/- 7.8 Ma. Accordingly, the latter value is interpreted as the minimum depositional age of the analysed Vila Maria strata, implying their deposition during Llandovery times. This concurs with the palynological results, which indicate an age no older than Early Silurian and, more particularly, favour an Early to Middle Llandovery (Rhuddanian-Early Aeronian) attribution. [less ▲]

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See detailPalaeozoic palynology. A special Issue in honour of Dr. Stanisla Loboziak
Steemans, Philippe ULg; Servais, T.; Streel, Maurice ULg

in Review of Palaeobotany and Palynology (2002), 118(Special Issue), 1-421

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See detailMiospore assemblages from the Silurian-Devonian boundary, in borehole A1-61, Ghadamis Basin, Libya
Rubinstein, C.; Steemans, Philippe ULg

in Review of Palaeobotany and Palynology (2002, April), 118(1-avr Sp. Iss. SI), 397-421

Well preserved and diversified miospore assemblages have been recorded from a relatively continuous sequence in borehole A1-61 which spans the Silurian-Devonian boundary in the northwestern part of the ... [more ▼]

Well preserved and diversified miospore assemblages have been recorded from a relatively continuous sequence in borehole A1-61 which spans the Silurian-Devonian boundary in the northwestern part of the Ghadamis Basin, Libya. The sequence is represented by early Devonian Lochkovian beds of the Tadrart Formation that transgress onto the Silurian Ludlow-Pridoli beds of the upper part of the 'Alternances Argilo-greseuses' Formation. The present work demonstrates a succession of miospore assemblages from closely sampled layers that have been stratigraphically dated as Ludlow-middle Pridoli and early Lochkovian by chitinozoans and acritarchs. Over 80 species of cryptospores and trilete spores have been identified. Modified detailed morphological interpretations are given. The miospore assemblages are correlated with miospore zonation schemes established for the type sequences of the Welsh Borderland, and those previously described from Libya. Early occurrences of some species as Streelispora newportensis on the western Gondwana plate, are put forward by comparison with the Old Red Sandstone continent. Phytogeographic and palaeobotanic implications based on these observations are discussed. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailDistribution du genre Leclercqia au Dévonien: implications paléogéographiques.
Meyer-Berthaud, Brigitte; Gerrienne, Philippe ULg; Fairon-Demaret, Muriel ULg et al

Conference (2002)

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