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Three-dimensional visualization of fossil flowers, fruits, seeds, and other plant remains using synchrotron radiation X-ray tomographic microscopy (SRXTM): new insights into Cretaceous plant diversity

Published online by Cambridge University Press:  14 July 2015

Else Marie Friis ,
Federica Marone ,
Kaj Raunsgaard Pedersen ,
Peter R. Crane  and
Marco Stampanoni
Else Marie Friis
Affiliation:
Department of Palaeobiology, Swedish Museum of Natural History, SE-104 05 Stockholm, Sweden,
Federica Marone
Affiliation:
Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland, ;
Kaj Raunsgaard Pedersen
Affiliation:
Department of Geology, University of Aarhus, DK-8000 Aarhus, Denmark,
Peter R. Crane
Affiliation:
Yale School of Forestry and Environmental Studies 195 Prospect Street, New Haven, CT 06511, USA,
Marco Stampanoni
Affiliation:
Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland, ; Institute for Biomedical Engineering, ETZ F 85, Swiss Federal Institute of Technology Zürich, Gloriastrasse 35, 8092 Zürich,
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Abstract

The application of synchrotron radiation X-ray tomographic microscopy (SRXTM) to the study of mesofossils of Cretaceous age has created new possibilities for the three-dimensional visualization and analysis of the external and internal structure of critical plant fossil material. SRXTM provides cellular and subcellular resolution of comparable or higher quality to that obtained from permineralized material using thin sections or the peel technique. SRXTM also has the advantage of being non-destructive and results in the rapid acquisition of large quantities of data in digital form. SRXTM thus refocuses the effort of the investigator from physical preparation to the digital post-processing of X-ray tomographic data, which allows great flexibility in the reconstruction, visualization, and analysis of the internal and external structure of fossil material in multiple planes and in two or three dimensions. A review of recent applications in paleobotany demonstrates that SRXTM will dramatically expand the level of information available for diverse fossil plants. Future refinement of SRXTM approaches that further increases resolution and eases digital post-processing, will transform the study of mesofossils and create new possibilities for advancing paleobotanical knowledge. We illustrate these points using a variety of Cretaceous mesofossils, highlighting in particular those cases where SRXTM has been essential for resolving critical structural details that have enhanced systematic understanding and improved phylogenetic interpretations.

Type
Research Article
Information
Journal of Paleontology , Volume 88 , Issue 4 , July 2014 , pp. 684 - 701
Copyright
Copyright © The Paleontological Society 

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References

APGIII. 2009. An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG III. Botanical Journal of the Linnean Society, 161:105–121.CrossRefGoogle Scholar
Boas, F. E. and Fleischmann, D. 2011. Evaluation of two iterative techniques for reducing metal artifacts in computed tomography. Radiology, 259:894–902.CrossRefGoogle ScholarPubMed
Boin, M. and Haibel, A. 2006. Compensation of ring artefacts in synchrotron tomographic imaging. Optics Express, 14:12071–12075.CrossRefGoogle Scholar
Bonse, U. and Hart, M. 1965. An X-ray interferometer with long separated interfering beam paths (E). Applied Physics Letters, 7:99–100.CrossRefGoogle Scholar
Bronnikov, A. V. 2002. Theory of quantitative phase-contrast computed tomography. Journal of the Optical Society of America A, 19:472–480.CrossRefGoogle ScholarPubMed
Brown, S. A. E., Scott, A. C., Glasspool, I. J., and Collinson, M. E. 2012. Cretaceous wildfires and their impact on the Earth system. Cretaceous Research, 36:162–190.CrossRefGoogle Scholar
Chandler, M. E. J. 1957. The Oligocene flora of the Bovey Tracey Lake Basin (Devonshire). Bulletin of the British Museum (Natural History) Geology, 3:7–123.CrossRefGoogle Scholar
Chapman, D., Thomlinson, W., Johnston, R. E., Washburn, D., Pisano, E., Gmur, N., Zhong, Z., Menk, R., Arfelli, F., and Sayers, D. 1997. Diffraction enhanced x-ray imaging. Physics in Medicine and Biology, 42:2015–2025.CrossRefGoogle ScholarPubMed
Cloetens, P., Barrett, R., Baruchel, J., Guigay, J. P., and Schlenker, M. 1996. Phase objects in synchrotron radiation hard x-ray imaging. Journal of Physics D-Applied Physics, 29:133–146.CrossRefGoogle Scholar
Cloetens, P., Ludwig, W., Baruchel, J., Van Dyck, D., Van Landuyt, J., Guigay, J. P., and Schlenker, M. 1999. Holotomography: quantitative phase tomography with micrometer resolution using hard synchrotron radiation x rays. Applied Physics Letters, 75:2912–2914.CrossRefGoogle Scholar
Collinson, M. E., Manchester, S. R., and Wilde, V. 2013a. Fossil fruits and seeds of the middle Eocene Messel biota, Germany. Abhandlungen der Senckenberg Gesellschaft für Naturforschung, 570:1–251.Google Scholar
Collinson, M. E., Smith, S. Y., Van Konijenburg-Van Cittert, J. H. A., Batten, D. J., Van Der Burgh, J., Barke, J., and Marone, F. 2013b. New observations and synthesis of Paleogene heterosporous water ferns. International Journal of Plant Sciences, 174:350–363.CrossRefGoogle Scholar
Crane, P. R. and Herendeen, P. S. 2009. Bennettitales from the Gristhorpe Bed (Middle Jurassic) at Cayton Bay, Yorkshire, U.K. American Journal of Botany, 96:284–295.CrossRefGoogle Scholar
Davis, T. J., Gao, D., Gureyev, T. E., Stevenson, A. W., and Wilkens, S. W. 1995. Phase-contrast imaging of weakly absorbing materials using hard X-rays. Nature, 373:595–598.CrossRefGoogle Scholar
Dorofeev, P. I. 1963. Treticnye flory Zapadnoj Sibiri. Izd. Akad. nauk SSSR, Moscow and Leningrad, p. 1–345.Google Scholar
Drinnan, A. N., Crane, P. R., Friis, E. M., and Pedersen, K. R. 1990. Lauraceous flowers from the Potomac Group (mid-Cretaceous) of eastern North America. Botanical Gazette, 151:370–384.CrossRefGoogle Scholar
Edwards, D. 1996. New insights into early land ecosystems: A glimpse of a lilliputian world. Review of Palaeobotany and Palynology, 90:159–174.CrossRefGoogle Scholar
Engler, A. 1930. Saxifragaceae, p. 74–226. InEngler, A. and Prantl, H., Die natürlichen Pflanzenfamilien, Bd. 18. Engelmann, Leipzig.Google Scholar
Eriksson, O., Friis, E. M., and Löfgren, P. 2000a. Seed size, fruit size and dispersal spectra in angiosperms from the Early Cretaceous to the late Tertiary. American Naturalist, 156:47–58.CrossRefGoogle Scholar
Eriksson, O., Friis, E. M., Pedersen, K. R., and Crane, P. R. 2000b. Seed size and dispersal systems of Early Cretaceous angiosperms from Famalicão, Portugal. International Journal of Plant Sciences, 161:319–329.CrossRefGoogle ScholarPubMed
Friis, E. M. 1985. Angiosperm fruits and seeds from the middle Miocene of Jutland (Denmark). Biologiske Skrifter, Det Kongelige Danske Videnskabernes Selskab, 24:1–165.Google Scholar
Friis, E. M. 1990. Silvianthemum suecicum gen. et sp. nov., a new saxifragalean flower from the Late Cretaceous of Sweden. Biologiske Skrifter, Det Kongelige Danske Videnskabernes Selskab, 36:1–35.Google Scholar
Friis, E. M., Crane, P. R., and Pedersen, K. R. 2011. Early flowers and angiosperm evolution. Cambridge University Press, Cambridge, p. 1–585.CrossRefGoogle Scholar
Friis, E. M., Crane, P. R., Pedersen, K. R., Bengtson, S., Donoghue, P. C. J., Grimm, G. W., and Stampanoni, M. 2007. Phase contrast enhanced synchrotron-radiation X-ray analyses of Cretaceous seeds link Gnetales to extinct Bennettitales. Nature, 450:549–552.CrossRefGoogle Scholar
Friis, E. M. and Pedersen, K. R. 2011. Canrightia resinifera gen. et sp. nov., a new extinct angiosperm with Retimonocolpites-type pollen from the Early Cretaceous of Portugal: Missing link in the eumagnoliid tree? Grana, 50:3–29.CrossRefGoogle Scholar
Friis, E. M. and Pedersen, K. R. 2012. Bertilanthus scanicus, a new asterid flower from the Late Cretaceous (late Santonian–early Campanian) of Scania, Sweden. International Journal of Plant Sciences, 173:318–330.CrossRefGoogle Scholar
Friis, E. M., Pedersen, K. R., and Crane, P. R. 1992. Esgueiria gen. nov., fossil flowers with combretaceous features from the Late Cretaceous of Portugal. Biologiske Skrifter, Det Kongelige Danske Videnskabernes Selskab, 41:1–45.Google Scholar
Friis, E. M., Pedersen, K. R., and Crane, P. R. 1994. Angiosperm floral structures from the Early Cretaceous of Portugal. Plant Systematics and Evolution, 8:31–49.Google Scholar
Friis, E. M., Pedersen, K. R., and Crane, P. R. 1999. Early angiosperm diversification: the diversity of pollen associated with angiosperm reproductive structures in Early Cretaceous floras from Portugal. Annals of the Missouri Botanical Garden, 86:259–296.CrossRefGoogle Scholar
Friis, E. M., Pedersen, K. R., and Crane, P. R. 2000. Reproductive structure and organization of basal angiosperms from the Early Cretaceous (Barremian or Aptian) of Western Portugal. International Journal of Plant Sciences, 161:S169–S182.CrossRefGoogle Scholar
Friis, E. M., Pedersen, K. R., and Crane, P. R. 2001. Fossil evidence of water lilies (Nymphaeales) in the Early Cretaceous. Nature, 410:357–360.CrossRefGoogle ScholarPubMed
Friis, E. M., Pedersen, K. R., and Crane, P. R. 2009a. Early Cretaceous mesofossils from Portugal and eastern North America related to the Bennettitales-Erdtmanithecales-Gnetales group. American Journal of Botany, 96:252–283.CrossRefGoogle Scholar
Friis, E. M., Pedersen, K. R., and Crane, P. R. 2010. Cretaceous diversification of angiosperms in the western part of the Iberian Peninsula. Review of Palaeobotany and Palynology, 162:341–361.CrossRefGoogle Scholar
Friis, E. M., Pedersen, K. R., and Crane, P. R. 2013a. New diversity among chlamydospermous seeds from the Early Cretaceous of Portugal and North America. International Journal of Plant Sciences, 173:530–558.CrossRefGoogle Scholar
Friis, E. M., Pedersen, K. R., and Crane, P. R. 2014a. Welwitschioid diversity in the Early Cretaceous: Evidence from fossil seeds with pollen from Portugal and eastern North America. Grana, in press.CrossRefGoogle Scholar
Friis, E. M., Pedersen, K. R., and Endress, P. K. 2013b. Floral structure of extant Quintinia (Paracryphiales, Campanulids) compared with the Late Cretaceous Silvianthemum and Bertilanthus. International Journal of Plant Sciences, 174:647–664.CrossRefGoogle Scholar
Friis, E. M., Pedersen, K. R., and Marone, F. 2014b. Arcellites punctatus sp. nov.: A new megaspore from the Early Cretaceous of Portugal studied using high resolution synchrotron radiation x-ray tomographic microscopy (SRXTM). Grana, in press.CrossRefGoogle Scholar
Friis, E. M., Pedersen, K. R., and Schönenberger, J. 2003. Endressianthus, a new Normapolles producing plant genus of fagalean affinity from the Late Cretaceous of Portugal. International Journal of Plant Sciences, 164 (5Suppl.):S201–S223.CrossRefGoogle Scholar
Friis, E. M., Pedersen, K. R., Von Balthazar, M., Grimm, G. W., and Crane, P. R. 2009b. Monetianthus mirus gen. et sp. nov., a nymphaealean flowers from the Early Cretaceous of Portugal. International Journal of Plant Sciences, 170:1086–1101.CrossRefGoogle Scholar
Friis, E. M. and Skarby, A. 1981. Structurally preserved angiosperm flowers from the Upper Cretaceous of southern Sweden. Nature, 291:485–486.CrossRefGoogle Scholar
Friis, E. M. and Skarby, A. 1982. Scandianthus gen. nov., angiosperm flowers of saxifragalean affinity from the Upper Cretaceous of southern Sweden. Annals of Botany, 50:569–583.CrossRefGoogle Scholar
Gandolfo, M. A., Nixon, K. C., and Crepet, W. L. 2004. Cretaceous flowers of Nymphaeaceae and implications for complex insect entrapment pollination mechanisms in early angiosperms. Proceedings of the National Academy of Sciences, U.S.A., 101:8056–8060.CrossRefGoogle ScholarPubMed
Groso, A., Abela, R., and Stampanoni, M. 2006. Implementation of a fast method for high resolution phase contrast tomography. Optics Express, 14:8103–8110.CrossRefGoogle ScholarPubMed
Haberthür, D., Hintermüller, C., Marone, F., Schittny, J. C., and Stampanoni, M. 2010. Radiation dose optimized lateral expansion of the field of view in synchrotron radiation X-ray tomographic microscopy. Journal of Synchrotron Radiation, 17:590–599.CrossRefGoogle ScholarPubMed
Harris, T. M. 1981. Burnt ferns from the English Wealden. Proceedings of the Geologists' Association, 92:47–58.CrossRefGoogle Scholar
Heřmanová, Z., Kvaček, J., and Friis, E. M. 2011. Budvaricarpus serialis Knobloch and Mai, an unusual new member of the Normapolles complex from the Late Cretaceous of the Czech Republic. International Journal of Plant Sciences, 172:285–293.CrossRefGoogle Scholar
Kak, A. C. and Slaney, M. 2001. Principles of computerized tomographic imaging. Society of Industrial and Applied Mathematics, Philadelphia, PA, p. 1–327.CrossRefGoogle Scholar
Kirchheimer, F. 1957. Die Laubgewächse der Braunkohlenzeit. Wilhelm Knapp Verlag, Halle, p. 1–783.Google Scholar
Lupia, R. 1995. Paleobotanical data from fossil charcoal: an actualistic study of seed plant reproductive structures. Palaios, 10:465–477.CrossRefGoogle Scholar
Mader, K., Marone, F., Hintermüller, C., Mikuljan, G., Isenegger, A., and Stampanoni, M. 2011. High-throughput full-automatic synchrotron-based tomographic microscopy. Synchrotron Radiation, 18:117–124.CrossRefGoogle ScholarPubMed
Mai, D. H. 1995. Tertiäre Vegetationsgeschichte Europas. Gustav Fischer Verlag, Jena, Stuttgart, New York, p. 1–691.Google Scholar
Marone, F., Münch, B., and Stampanoni, M. 2010. Fast reconstruction algorithm dealing with tomography artifacts. InStock, S. R., Developments in X-Ray Tomography Vii, San Diego, Proceedings of SPIE-The International Society for Optical Engineering.CrossRefGoogle Scholar
Marone, F. and Stampanoni, M. 2012. Regridding reconstruction algorithm for real-time tomographic imaging. Journal of Synchrotron Radiation, 19:1029–1037.CrossRefGoogle ScholarPubMed
Mendes, M. M., Dinis, J., Pais, J., and Friis, E. M. 2014. Vegetational composition of the Early Cretaceous Chicalhão flora (Lusitanian Basin, western Portugal) based on palynological and mesofossil assemblages. Review of Palaeobotany and Palynology, 200:65–81.CrossRefGoogle Scholar
Mendes, M. M., Pais, J., and Friis, E. M. 2008. Raunsgaardispermum lusitanicum gen. et sp. nov., a new seed with in situ pollen from the Early Cretaceous (probably Berriasian) of Portugal: Further support for the Bennettitales-Erdtmanithecales-Gnetales link. Grana, 47:211–219.CrossRefGoogle Scholar
Mohr, B. A. R., Bernardes-De-Oliveira, M. E. C., and Taylor, D. W. 2008. Pluricarpellatia, a nymphaealean angiosperm from the Lower Cretaceous of northern Gondwana (Crato Formation, Brazil). Taxon, 57:1147–1158.CrossRefGoogle Scholar
Moreau, J.-D., Cloetens, P., Gomez, B., Daviero-Gomez, V., Néraudeau, D., Lafford, T. A., and Tafforeau, P. 2014. Multiscale 3D virtual dissections of 100-million-year-old flowers using X-Ray synchrotron micro and nanotomography. Microscopy and Microanalysis, 20:305–312.CrossRefGoogle ScholarPubMed
Münch, B., Trtik, P., Marone, F., and Stampanoni, M. 2009. Stripe and ring artifact removal with combined wavelet-Fourier filtering. Optics Express, 17:8567–8591.CrossRefGoogle ScholarPubMed
Paganin, D., Mayo, S. C., Gureyev, T. E., Miller, P. R., and Wilkins, S. W. 2002. Simultaneous phase and amplitude extraction from a single defocused image of a homogeneous object. Journal of Microscopy-Oxford, 206:33–40.CrossRefGoogle ScholarPubMed
Pedersen, K. R., Crane, P. R., and Friis, E. M. 1989. Pollen organs and seeds with Eucommiidites pollen. Grana, 28:279–294.CrossRefGoogle Scholar
Prell, D., Kyriakou, Y., Kachelriess, M., and Kalender, W. A. 2010. Reducing metal artifacts in computed tomography caused by hip endoprostheses using a physics-based approach. Investigative Radiology, 45:747–754.CrossRefGoogle ScholarPubMed
Rashid-Farrokhi, F., Liu, K. J. R., Berenstein, C. A., and Walnut, D. 1997. Wavelet-based multiresolution local tomography. Transactions on Image Processing, 6:1412–1430.CrossRefGoogle ScholarPubMed
Reid, C. and Reid, E. M. 1915. The Pliocene floras of the Dutch Prussian border. Mededelingen van de Rijksopsporing van Delfstoffen, 6:1–178.Google Scholar
Rothwell, G. W., Crepet, W. L., and Stockey, R. A. 2009. Is the anthophyte hypothesis alive and well? New evidence from the reproductive structures of Bennettitales. American Journal of Botany, 96:296–322.CrossRefGoogle ScholarPubMed
Rydin, C., Pedersen, K. R., Crane, P. R., and Friis, E. M. 2006. Former diversity of Ephedra (Gnetales): evidence from Early Cretaceous seeds from Portugal and North America. Annals of Botany, 98:123–140.CrossRefGoogle ScholarPubMed
Schönenberger, J. and Friis, E. M. 2001. Fossil flowers of ericalean s.l. affinity from the Late Cretaceous of southern Sweden. American Journal of Botany, 88:467–480.CrossRefGoogle ScholarPubMed
Schönenberger, J., Friis, E. M., Matthews, M. L., and Endress, P. K. 2001a. Cunoniaceae in the Cretaceous of Europe: evidence from fossil flowers. Annals of Botany, 88:423–437.CrossRefGoogle Scholar
Schönenberger, J., Pedersen, K. R., and Friis, E. M. 2001b. Normapolles flowers of fagalean affinity from the Late Cretaceous of Portugal. Plant Systematics and Evolution, 226:205–230.Google Scholar
Schönenberger, J., Von Balthazar, M., Takahashi, M., Xiao, X., Crane, P. R., and Herendeen, P. S. 2012. Glandulocalyx upatoiensis, a fossil flower of Ericales (Actinidiaceae/Clethraceae) from the Late Cretaceous (Santonian) of Georgia, U.S.A. Annals of Botany, 109:921–936.CrossRefGoogle Scholar
Scott, A. C., Galtier, J., Gostling, N. J., Smith, S. Y., Collinson, M. E., Stampanoni, M., Marone, F., Donoghue, P. C. J., and Bengtson, S. 2009. Scanning electron microscopy and synchrotron radiation X-ray tomographic microscopy of 330 million year old charcoalified seed fern fertile organs. Microscopy and Microanalysis, 15:166–173.CrossRefGoogle ScholarPubMed
Scott, A. C. and Jones, T. P. 1991. Microscopical observations of recent and fossil charcoal. Microscopy and Analysis, July 1991:13–15.Google Scholar
Sijbers, J. and Postnovz, A. 2004. Reduction of ring artefacts in high resolution micro-CT reconstructions. Physics in Medicine and Biology, 49:N247–N253.CrossRefGoogle ScholarPubMed
Slater, B. J., McLoughlin, S., and Hilton, J. 2011. Guadalupian (Middle Permian) megaspores from a permineralised peat in the Bainmedart Coal Measures, Prince Charles Mountains, Antarctica. Review of Palaeobotany and Palynology, 167:140–155.CrossRefGoogle Scholar
Smith, S. Y., Collinson, M. E., Rudall, P. J., Simpson, D. A., Marone, F., and Stampanoni, M. 2009a. Virtual taphonomy using synchrotron tomographic microscopy reveals cryptic features and internal structure of modern and fossil plants. Proceedings of the National Academy of Sciences, 106:12013–12018.CrossRefGoogle ScholarPubMed
Smith, S. Y., Collinson, M. E., Simpson, D. A., Rudall, P. J., Marone, F., and Stampanoni, M. 2009b. Elucidating the affinities and habitat of ancient, widespread Cyperaceae: Volkeria messelensis gen. et sp. nov., a fossil mapanioid sedge from the Eocene of Europe. American Journal of Botany, 96:1506–1518.CrossRefGoogle Scholar
Snigirev, A., Snigireva, I., Kohn, V., Kuznetsov, S., and Schelokov, I. 1995. On the possibilities of x-ray phase contrast microimaging by coherent high-energy synchrotron radiation. Review of Scientific Instruments, 66:5486–5492.CrossRefGoogle Scholar
Staedler, Y. M., Masson, D., and Schönenberger, J. 1913. Plant tissues in 3D via X-ray tomography: Simple contrasting methods allow high resolution imaging. PlosOne, 8:1–10.Google Scholar
Stampanoni, M., Groso, A., Isenegger, A., Mikuljan, G., Chen, Q., Bertrand, A., Henein, S., Betemps, R., Frommherz, U., Bohler, P., Meister, D., Lange, M., and Abela, R. 2006. Trends in synchrotron-based tomographic imaging: the SLS experience, p. 780410-1/11. InBonse, U., Developments in X-Ray Tomography V, Proceedings of the Society of Photo-Optical Instrumentation Engineers (SPIE).CrossRefGoogle Scholar
Takhtajan, A. L. 1969. Flowering plants. Origin and dispersal. Oliver and Boyd, Edinburgh, p. 1–310.Google Scholar
Tiffney, B. H. 1977. Dicotyledonous angiosperm flower from the Upper Cretaceous of Martha's Vineyard. Massachusetts. Nature, 265:136–137.CrossRefGoogle Scholar
Tiffney, B. H. 1984. Seed size, dispersal syndromes, and the rise of the angiosperms: evidence and hypothesis. Annals of the Missouri Botanical Garden, 71:551–576.CrossRefGoogle Scholar
Titarenko, S., Withers, P. J., and Yagola, A. 2010. An analytical formula for ring artefact suppression in X-ray tomography. Applied Mathematics Letters, 23:1489–1495.CrossRefGoogle Scholar
Weitkamp, T., Diaz, A., David, C., Pfeiffer, F., Stampanoni, M., Cloetens, P., and Ziegler, E. 2005. X-ray phase imaging with a grating interferometer. Optics Express, 13:6296–6304.CrossRefGoogle ScholarPubMed
Viehofen, A., Hartkopf-Fröder, C., and Friis, E. M. 2008. Inflorescences and flowers of Mauldinia angustiloba sp. nov. (Lauraceae) from mid-Cretaceous karst infillings in the Rhenish Massif, Germany. International Journal of Plant Sciences, 169:871–889.CrossRefGoogle Scholar
Von Balthazar, M., Crane, P. R., Pedersen, K. R., and Friis, E. M. 2011. New flowers of Laurales from the Early Cretaceous (early to middle Albian) of eastern North America, p. 49–87. InWanntorp, L. and Ronse De Craene, L. P.(eds.), Flowers on the Tree of Life. Cambridge University Press, Cambridge.CrossRefGoogle Scholar
Von Balthazar, M., Pedersen, K. R., Crane, P. R., and Friis, E. M. 2008. Carpestella lacunata gen. et sp. nov., a new basal angiosperm flower from the Early Cretaceous (early to middle Albian) of eastern North America. International Journal of Plant Sciences, 169:890–898.CrossRefGoogle Scholar
Von Balthazar, M., Pedersen, K. R., Crane, P. R., Stampanoni, M., and Friis, E. M. 2007. Potomacanthus lobatus gen. et sp. nov., a new flower of probable Lauraceae from the Early Cretaceous (early to middle Albian) of eastern North America. American Journal of Botany, 94:2041–2053.CrossRefGoogle Scholar