Biomedical subjects

M Fairon-Demaret

Publications and source records attributed to M Fairon-Demaret.

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↗

PubMed2001

Leaf dimorphism in Archaeopteris roemeriana (Progymnosperm): further early fossil evidence of shoot dorsiventrality.

Additional information on the morphology of the vegetative ultimate branches of Archaeopteris roemeriana was obtained by uncovering compression specimens collected in Upper Devonian deposits in Belgium. For the first time, anisophylly, previously inferred from anatomical studies, is demonstrated on one species of the genus. Small leaves less than half the size of those more readily seen in unprepared compressions are borne on the adaxial surface of the ultimate branches. The phyllotaxis is discussed and the eventual adaptation to light interception of the combination of anisophylly and shoot dorsiventrality is put forward.

Journal Article↗

PubMed2000

A Reconsideration of Hyenia elegans Kräusel et Weyland and Hyenia 'complexa' Leclercq: Two Middle Devonian Cladoxylopsids from Western Europe.

Two taxa of Middle Devonian Cladoxylopsida from localities in Belgium and Germany are redescribed. A counterpart of one of the missing type specimens of Hyenia elegans Kräusel et Weyland from Kirberg, Germany, demonstrates that rather than having simple forked fertile appendages (as apparent from the type description), more complex fertile units were present; these consisted of two daughter segments (resulting from a proximal dichotomy), each of which bore three pairs of elongate sporangia on short recurved stalks proximal to a terminal bifurcation. Specimens from Oé, Belgium, informally referred to as Hyenia 'complexa' by Leclercq, were shown to have a similar fertile organ that lacked the tuft of filiform extensions previously believed to be present. The parallel axes of this plant are now interpreted to be derived from a digitate branch rather than from a horizontal rhizome. Both taxa, H. elegans and H. 'complexa,' therefore demonstrate fertile appendage morphology and other characters that are typical of the Middle Devonian cladoxylopsid Calamophyton primaevum Kräusel et Weyland, which has priority.

Journal Article↗