Prestianni, Cyrille , Hilton, Jason , Gerrienne, Philippe .
“Xenotheca” and Pseudosporogonites: two Belgian acupulate seeds?
Accumulating evidence indicates that the first major seed plant radiation occurred during the Late Devonian. Fourteen species have now been recognized, 7 of which have been collected from Belgian localities. Late Devonian seeds are comprised of 5 broadly defined groups of which 4 include cupulate representatives. Aglosperma Hilton from Britain has previously been interpreted as lacking a cupule and has been used to characterize the acupulate early seed group. Aglosperma is most similar to the Belgian species “Xenotheca” bertrandii Stockmans and Pseudosporogonites hallei Stockmans, neither of which have been previously subjected to detailed investigation. We present new information on the Belgian species and conclude that they are very similar with each other and most likely belong to the same genus. Both are radially symmetrical ovules with 4 flat integumentary lobes that are fused to one another towards the chalaza only. The integument surrounds a megasporangium with probable hydrasperman-type pollen chamber. However, some specimens of both species show an additional structure that inconspicuously covers the base of the integument. This structure is interpreted as a small cupule. Presence of this small cupule excludes the specimens from the acupulate early seed group and their features differ markedly from those of the type species of “Xenotheca”. Results question the existence of an acupulate early seed group and have led to re-examination of Aglosperma in search of a small cupule at the base of the integument.
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1 - Universite de Liege, Géologie, unité P.P.M., Allée du 6 aout B18, Liège, 4000, Belgium
2 - University of Birmingham, School of Geography, Earth and Environmental Sciences, G5 Aston Webb Building, Edgbaston, Birmingham, B152TT, United Kingdom
Presentation Type: Oral Paper:Papers for Sections
Date: Monday, July 28th, 2008
Time: 8:30 AM