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Early Cretaceous mesofossils from Portugal and eastern North America related to the Bennettitales-Erdtmanithecales-Gnetales group¹

² Department of Palaeobotany, Swedish Museum of Natural History, SE-104 05 Stockholm, Sweden ³ Department of Geology, University of Aarhus, DK-8000 Århus C, Denmark ⁴ Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois 60637 USA

ABSTRACT

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.

Key Words: anthophytes • BEG group • ephedroids • extinct seed plants • fossil seeds • PCXTM • seed plant phylogeny • SRXTM • synchrotron-radiation X-ray tomographic microscopy

Received for publication 29 March 2008. Accepted for publication 13 October 2008.

FOOTNOTES

¹ The authors thank J.-P. and M. Rioult for valuable information and help in retrieving the original specimen of Cycadeoidea morierei. They also thank P. von Knorring for preparing the line drawings, M. von Balthazar for preparing some of the Puddledock specimens, and M. Stampanoni, F. Marone, S. Bengtson, and T. Huldtgren for help with SRXTM and PCXTM analyses at the Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland. This research project has been supported by the European Commission under FP6: Strengthening the European Research Area, Research Infrastructures: project no. 20070197 (to P. C. J. Donoghue, S. Bengtson, and E. M. Friis), by the Swedish Natural Science Research Council (E. M. Friis), the Carlsberg Foundation (K. R. Pedersen), and the U.S. National Science Foundation (P. R. Crane).

⁵ Author for correspondence (e-mail: else.marie.friis{at}nrm.se)

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