Phase-contrast X-ray microtomography links Cretaceous seeds with Gnetales and Bennettitales

Abstract

Over the past 25 years the discovery and study of Cretaceous plant mesofossils has yielded diverse and exquisitely preserved fossil flowers that have revolutionized our knowledge of early angiosperms1, but remains of other seed plants in the same mesofossil assemblages2,3 have so far received little attention. These fossils, typically only a few millimetres long, have often been charred in natural fires and preserve both three-dimensional morphology and cellular detail. Here we use phase-contrast-enhanced synchrotron-radiation X-ray tomographic microscopy to clarify the structure of small charcoalified gymnosperm seeds from the Early Cretaceous of Portugal and North America. The new information links these seeds to Gnetales (including Erdtmanithecales, a putatively closely related fossil group2), and to Bennettitales—important extinct Mesozoic seed plants with cycad-like leaves and flower-like reproductive structures. The results suggest that the distinctive seed architecture of Gnetales, Erdtmanithecales and Bennettitales defines a clade containing these taxa. This has significant consequences for hypotheses of seed plant phylogeny by providing support for key elements of the controversial anthophyte hypothesis, which links angiosperms, Bennettitales and Gnetales.

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Figure 1: Early Cretaceous (Barremian–Aptian) seed from Catefica, Portugal, with affinities to Gnetales and Bennettitales.
Figure 2: Early Cretaceous (mid-Albian) seed from the Puddledock locality, USA, with affinities to Gnetales and Bennettitales.
Figure 3: The phylogenetic relationships among ‘anthophytes’.

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Acknowledgements

We thank F. Marone of the Swiss Light Source for valuable help in setting up the software on the cluster, and T. Huldtgren and N. J. Gostling for help with data analyses. We also thank the Natural History Museum, London, for the loan of petrified specimens, J.-P. Rioult for information on the Lignier fossils, and J. Hilton for helpful suggestions. This study was funded by the Swiss Light Source (P.C.J.D. and S.B.), European Union FP6, as well as by grants from the Swedish Research Council (E.M.F.), the Carlsberg Foundations (K.R.P. and E.M.F.) and the National Science Foundation (P.R.C.).

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Correspondence to Else Marie Friis or Marco Stampanoni.

Supplementary information

Supplementary Information

The file contains Supplementary Notes, Supplementary Figures S1-S2 with Legends and Supplementary Tables 1-3. Supplementary Notes include supporting data for the charcoalified fossils; anatomical comparison between the charcoalified seeds and extinct Bennettitales; cladistic analysis expanding the Hilton and Bateman data matrix and additional references. (PDF 1884 kb)

41586_2007_BFnature06278_MOESM203_ESM.mov

The file contains Supplementary Video 1 with the reconstructed slice data for specimen S153152 showing transverse sections. (MOV 42932 kb)

Supplementary Video 1

The file contains Supplementary Video 1 with the reconstructed slice data for specimen S153152 showing transverse sections. (MOV 42932 kb)

41586_2007_BFnature06278_MOESM204_ESM.mov

The file contains Supplementary Video 2 with the reconstructed slice data for specimen S153152 showing longitudinal sections. (MOV 30111 kb)

Supplementary Video 2

The file contains Supplementary Video 2 with the reconstructed slice data for specimen S153152 showing longitudinal sections. (MOV 30111 kb)

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Friis, E., Crane, P., Pedersen, K. et al. Phase-contrast X-ray microtomography links Cretaceous seeds with Gnetales and Bennettitales. Nature 450, 549–552 (2007). https://doi.org/10.1038/nature06278

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