Biomedical subjects

M Streel

Publications and source records attributed to M Streel.

4 recordsLinked to original sources

PubMed2004

Runcaria, a middle devonian seed plant precursor.

The emergence of the seed habit in the Middle Paleozoic 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.

Belgium↗

PubMed2001

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.

Journal Article↗

PubMed2000

Systematic study and stratigraphic correlation of the Grandispora complex in the Famennian of northwest and eastern Europe.

In northwest and eastern Europe different miospore zonation schemes have been erected for the Famennian rocks, and correlation of these has proved problematical. However, in both regions of Europe Grandispora taxa are common elements in the respective Famennian spore successions, and it appears these taxa may have important intra-continental correlation potential. In order to assess this potential, a C.I.M.P. working group has undertaken a taxonomic study of the Grandispora complex in the Famennian of both regions. Representative material from Belarus, Poland, Germany, Belgium, France and Ireland has been exchanged, and then jointly studied, at four workshop meetings. A consensus of agreement has been reached on the morphological delineation and nomenclature of 13 species of Grandispora, and a description of each taxon is presented. One new species Grandispora tamarae is erected, and six new generic combinations are proposed. The stratigraphic range of each species in both regions is documented and calibrated with the respective conodont zonation schemes. It can be shown that many of the Grandispora species seem to have their first occurrence at similar stratigraphic levels. These new data allow detailed correlations of the Famennian miospore zonation schemes to be proposed.

Journal Article↗

PubMed2000

Miospores from the Frasnian-Famennian Boundary deposits in Eastern Europe (the Pripyat Depression, Belarus and the Timan-Pechora Province, Russia) and comparison with Western Europe (Northern France).

A zonal subdivision of the Frasnian-Famennian transitional deposits in the Pripyat Depression and Timan-Pechora Province, based on a detailed palynological study, has been completed. The data obtained on miospores and conodonts from the Timan-Pechora Province enable a correlation to be made with the Standard Conodont Zonation. The lateral extent of the palynozones in Eastern Europe and the correlation with Western Europe are discussed. The following previously published new combinations are validated: Auroraspora speciosa (Naumova) Obukhovskaya, comb. nov., Corbulispora viminea (Nekriata) Obukhovskaya and Nekriata, comb. nov., Cristatisporites imperpetuus (Sennova) Obukhovskaya, comb. nov., Cymbosporites acanthaceus (Kedo) Obukhovskaya, comb. nov., Grandispora subsuta (Nazarenko) Obukhovskaya, comb. nov., and Verrucosisporites evlanensis (Naumova) Obukhovskaya, comb. nov.

Journal Article↗