Journal
AMERICAN JOURNAL OF BOTANY
Volume 96, Issue 1, Pages 252-283Publisher
WILEY
DOI: 10.3732/ajb.0800113
Keywords
anthophytes; BEG group; ephedroids; extinct seed plants; fossil seeds; PCXTM; seed plant phylogeny; SRXTM; synchrotron-radiation X-ray tomographic microscopy
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Funding
- European Commission under FP6
- Strengthening the European Research Area, Research Infrastructures [20070197]
- Swedish Natural Science Research Council
- Carlsberg Foundation
- U.S. National Science Foundation
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Four new genera and six new species of fossil seed (Buarcospermum tetragonium, Lignierispermum maroneae, Lobospermum glabrum, L. rugosum, L. stampanonii, Rugonella trigonospermum) are described from five Early Cretaceous mesofossil floras from Portugal and eastern North America. The four genera are distinguished by differences in size, shape, and details of seed anatomy, but all are unusual in having an outer seed envelope with a distinctive anatomical structure that surrounds the nucellus and the integument. The integument is extended apically into a long, narrow micropylar tube. The four new genera are part of a diverse, but previously unrecognized, complex of extinct plants that was widespread in Early Cretaceous vegetation and that coexisted in similar habitats with early angiosperms. The distinctive structure of these seeds, and the strong similarities to other fossil seeds (Ephedra, Ephedripites, Erdtmanispermum, Raunsgaardispermum, and some Bennettitales) already known from the Early Cretaceous. suggests that this newly recognized complex of extinct plants, together with Bennettitales, Erdtmanithecales, and Gnetales (the BEG group), is phylogenetically closely related.
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